Nonsurgical and surgical periodontal therapy in single-rooted teeth

The purpose of this study was to compare the effect of tooth related and patient related factors on the success of non-surgical and surgical periodontal therapy. In 41 patients (22 female) with untreated and/or recurrent periodontitis, no therapy, scaling and root planing (SRP), or access flap (AF) were assigned according to probing pocket depth (PPD). PPD and vertical relative attachment level (RAL-V) were obtained initially, 3 and 6 months after therapy. Baseline data were compared according to therapy, jaw, tooth type, and site. Factors influencing clinical parameters were identified using multilevel analyses. Baseline PPDs were deeper interproximally, in the maxilla and at premolars compared to buccal/oral sites, mandibular, and anterior teeth. At 6 months, PPD reduction and RAL-V gain were significantly greater at sites receiving SRP and AF as compared to untreated sites (p < 0.001). PPD reduction and RAL-V gain were significantly less (p < 0.005) in smokers as compared to nosmokers and at interproximal sites (p < 0.0001) as compared to buccal/oral sites. RAL-V gain was less in aggressive periodontitis, and PPD reduction was less in the maxilla (p < 0.001). In sites with greater bone loss and infrabony defects, a poorer response was observed regarding RAL-V gain or PPD reduction, respectively. The conclusions of the study are the following: (1) Nonsurgical and surgical periodontal therapies are effective in single-rooted teeth; (2) severe interproximal bone loss and infrabony defects deteriorate clinical results; and (3) there seem to be more defect-associated (tooth, site) factors influencing treatment outcome than patient-associated factors.
Introduction
The major factor in the etiology of periodontitis is the dental biofilm, i.e., bacterial plaque. Thus, the aim of anti-infective periodontal therapy is the reduction in supra- and subgingival microbial plaque to resolve periodontal inflammation. Subgingival scaling and root planing (SRP) may result in resolution of inflammation, reduced probing pocket depths (PPD), and clinical attachment gain [1, 2, 16]. However, nonsurgical periodontal therapy, i.e., SRP, is not found to be successful at all treated sites. Although not all factors influencing failure of nonsurgical therapy are known, deep periodontal pockets [3, 21, 25, 28] and furcation involvement [6, 9, 23] are some of them. Recent meta-analyses have shown the efficacy of nonsurgical therapy in moderate and deep periodontal pockets. In deep pockets, access flap (AF) techniques result in better reduction in PPD and clinical attachment gain [14, 15]. However, these meta-analyses like many other studies on this issue before [3, 21, 25, 28] use mean values and are not able to reflect the benefit of a particular technique at teeth with certain defects, e.g., infrabony pockets. However, calculation of a mean value, e.g., for PPD reduction, across a patient in fact levels out tooth-related characteristics. Even if separate strata for different baseline PPD are considered, tooth-related factors other than baseline PPD are leveled out also. This may lead to quite similar mean values for nonsurgical and surgical therapy for a patient or across a whole sample because tooth-related differences between both approaches because of different amounts or types of bone loss, jaw, etc. are leveled out. More recent statistical methods such as the multilevel modeling are considering single-tooth or even site characteristics while still regarding the individual patient as a statistical unit. In a structured review of 2002, it was explicitly stated that the included studies showed similar results for nonsurgical and surgical therapy after 1 year. However, insufficient studies are available to evaluate the various treatment procedures, e.g., in angular defects. Further, it is stated that subject characteristics and their possible effect on treatment outcome was not addressed in the studies available at that time [14]. Thus, there is a need for more information on the effect of patient and tooth-related factors on nonsurgical and surgical periodontal therapy. Well known hypotheses and the use of these more recent statistical methods may lead to new information.
Clinical measurements in posterior are less reproducible than in anterior teeth [7]. Furcation involvement is a known factor to influence treatment outcome of nonsurgical and surgical therapy. To provide a high level of reproducibility of clinical measurements and to exclude a already known influencing factor, only single-rooted teeth were considered in this study.
The hypothesis behind this study is that different tooth-related factors (e.g., tooth type, site, plaque, residual inflammation, horizontal/vertical bone loss) and patient-related factors (e.g., age, sex, diagnosis, smoking) determine the initial outcome of nonsurgical and surgical periodontal therapy in single-rooted teeth.
Thus, the aim of the present study was to identify patient and site factors that determine the initial outcome of nonsurgical and surgical periodontal therapy in single-rooted teeth using more recent statistical methods.
Materials and methods
Patients
The study group consisted of 41 patients (22 female) suffering from moderate to severe periodontal disease. These patients had been scheduled for periodontal treatment within a randomized placebo-controlled clinical trial evaluating the effect of a subgingivally delivered 14% doxycycline gel at the Section of Periodontology, Department of Conservative Dentistry, Clinic for Oral, Dental and Maxillofacial Diseases, University Hospital Heidelberg. Each patient had to have three single-rooted teeth that qualified as test teeth for the doxycycline study; that is, only three teeth per patient were included into this study [8]. Inclusion criteria were at least 23 years of age, untreated moderate to severe periodontal disease or recurrent periodontitis without periodontal surgery at least for the last 24 months, effective individual oral hygiene (plaque control record < 35%) [24], and written informed consent. Exclusion criteria were local and/or systemic antibiotic therapy within the last 6 months before the baseline examination of the study, known adverse reactions to any component of the test agent, anticoagulative therapy, liver, kidney, gastroenteral diseases, pregnancy, and women who were lactating. All patients were asked about current and past cigarette consumption. A patient was classified as a current smoker if he smoked one or more cigarettes per day and as a former smoker if he had quit smoking for at least 5 years. Patients who had quit smoking within the last 5 years were classified current smokers. No more than 50% of current smokers were allowed in the sample. All patients were classified as chronic or aggressive periodontitis according to the following criteria:
Aggressive periodontitis: Patient is clinically healthy; that is, systemic diseases predisposing for periodontitis are not known; radiographic bone loss greater than or equal to 50% in at least two different teeth and age less that or equal to 35 years at time of diagnosis.Moderate and severe chronic periodontitis: attachment loss greater than or equal to 3 mm and age greater than 35 years [19].
The study was approved by the Institutional Review Boards for Human Studies of the University of Heidelberg.
Clinical examination
After completion of initial periodontal treatment including oral hygiene instruction and supragingival scaling, PPD were measured at four sites of every tooth. If a patient fulfilled the inclusion criteria, the study protocol, risks, benefits, and procedures were explained, and informed written consent was obtained. One week before test therapy, the Gingival Index (GI) and Plaque Index (PlI) [22] were assessed at six sites (mesiobuccal, midbuccal, distobuccal, distolingual, midlingual, mesiolingual) of every incisor, canine, and premolar. PPD and vertical relative attachment levels (RAL-V) were measured to the nearest 0.5 mm using a straight periodontal probe (PCPUNC 15, Hu Friedy, Chicago, IL) at six sites per tooth. A reference splint gave the location of probing by notches and served as reference for the RAL-V measurements. Bleeding on probing (BOP) was recorded approximately 30 s after probing. After the first course of measurements, all PPD and RAL-V measurements were repeated. The means of the pairs of double measurements were used for analysis. If a pair of PPD double measurements showed a difference greater than 2 mm, a third measurement was performed at the respective site (option 3). Then, the mean of the pair of the closer measurements was taken for analysis at the respective site. All clinical measurements before therapy were performed by one examiner (Eickholz) who also performed active periodontal therapy (subgingival debridement and surgery) in all patients. Within each patient, three test teeth with PPD = 5 mm and BOP or PPD ≥ 6 mm were selected for the doxycycline study. These teeth were excluded from this examination. Three and 6 months after therapy, the clinical examinations were repeated in the same manner by a second examiner (Kim) who did not have any information about baseline data and the therapy [8].
Radiographic examination and evaluation
Before therapy, in 36 patients, full-mouth sets of periapical radiographs (Ektaspeed plus; Kodac, Rochester, NY) were obtained in XCP technique (XCP, Kentzler & Kaschner Dental, Ellwangen/Jagst, Germany). Intraoral size 0 (maxillary second incisors and mandibular anteriors) and 2 (all other regions) dental films were exposed to an X-ray source (Heliodent DS®, 60 kV, 7 mA, Sirona, Bensheim, Germany) and developed under standardized conditions (XR 24 Nova®, Dürr Dental, Bietigheim–Bissingen, Germany).
All radiographs were viewed in a darkened room using a radiograph screen (67-0420, Dentsply Rinn, Elgin, IL). Each interproximal surface of single-rooted teeth was classified for the type of bone loss (horizontal/vertical). Further, the prevalence of a double contour of the root was noted that was taken as indicative for a mesial or distal groove. Relative bone loss in percent was assessed at two sites per tooth (mesial and distal) using a Schei ruler [27]. This ruler consisted of six straight lines that divert in the same angle. For each site, the basic line of the Schei ruler was placed to the cementoenamel junction (CEJ) of the respective tooth parallel to the occlusal plane. Then, the ruler was moved until the sixth line was placed tangentially to the apex. Finally, the alveolar crest was located. Location between the two coronal lines meant bone loss up to 20% of root length. Location between the second and third line meant between 20 and 40% bone loss and so forth. If the CEJ was destroyed or overlapped by interproximal restorations, the restoration margin was used as reference. If the alveolar crest could not be determined because of overlapping of adjacent teeth, the interproximal site was classified as “cannot be assessed.” If an interproximal surface showed a double contour, this was classified as an interproximal root groove. All radiographic assessments were performed by an examiner who was blinded to the clinical measurements and therapy assignments (Schenk).
Therapy
Teeth exhibiting PPD < 3 mm were treated neither by subgingival SRP nor by AF [26]. SRP was performed when PPD ≥ 3 and ≤6 mm were present. If periodontal surgery was necessary at teeth not adjacent to test teeth, this was performed 1 week after SRP: AF was chosen for teeth exhibiting PPD > 6 mm. However, SRP was performed at all test teeth (not included in this analysis) and the respective neighboring teeth under local anesthesia with hand instruments even for baseline PPD > 6 mm. Thus, also some sites with PPD > 6 mm were treated exclusively by SRP. Further, the decision to perform AF was taken per tooth and not per site. Thus, also sites with PPD ≤ 6 mm were treated by AF if the respective tooth exhibited PPD > 6 mm at one site. Thereby, effectiveness of SRP and AF maybe analyzed across the limits of indications as the ranges of PPD for the three treatment groups in Table 4 demonstrate. Maintenance including oral hygiene instruction and professional tooth cleaning was done 3 months after test therapy.
Statistical analysis
Data handling
All data were entered into a personal computer program (Systat™ for Windows version 10, Systat, Evanston, IL; Schenk). Descriptive statistics were then calculated using another program (SPSS™, version 10.0.1, SPSS, Chicago IL) by an independent statistician (Lungeanu). Multilevel analyses were modeled by another independent statistician (Reitmeir) using a third program (SAS® version 6.12, SAS Institute, Cary, NC).
Reproducibility
The replicate PPD and RAL assessments for all teeth were used to estimate the intraexaminer reproducibility. The intraexaminer reproducibility of PPD and RAL measurements was expressed as the standard deviation of single measurements [4].
Treatment comparison
The individual patient was considered as a statistical unit in this analysis. The main outcome variable for the comparison of the therapeutic effects of no further therapy, SRP, or AF was chosen to be the change of PPD. RAL-V was considered as a secondary endpoint. All other clinical parameters (GI, PlI) were control variables.
Only sites were included that could be assessed at all three examinations. Additionally, baseline clinical parameters were calculated separately according to therapy (no therapy, SRP, AF), jaw, tooth type (anterior/premolar), and site (interproximal/buccal and oral) and compared using multilevel methodology [10, 11]. A probability p < 0.05 was accepted for a difference to be statistically significant. Because of multiple testing, a Bonferroni correction was performed: We tested 24 independent hypotheses on our set of data. Thus, the statistical significance level that should be used for each hypothesis separately is 1 of 24 times what it would be if only one hypothesis were tested, i.e., p = 0.002. For all analyses, the basic level “site” was nested in the upper level “tooth,” which itself was nested in the next upper level “patient,” and patient effects on the outcome were assumed to be random. This technique allows the identification of single-tooth effects or parameters while still considering the individual patient as a statistical unit and the dependencies of site and tooth data within a patient [10, 11]. Multilevel regressions were calculated including only clinical parameters providing six measurements per tooth first (site level: n = 4,146; patient level: n = 40). Further analyses were performed that included also radiographic parameters. Radiographic parameters were only available for those patients contributing full-mouth radiographic examinations and could be related only to interproximal sites (mesiobuccal, mesiolingual, distolingual, mesiolingual), i.e., four sites per tooth (site level: n = 1,792; patient level: n = 36).
To identify factors influencing the treatment result, change of RAL-V and PPD were analyzed by application of a multilevel regression model using backward selection. Models were fitted for the dependent variables (1) RAL-V change after 6 months and (2) PPD change after 6 months including the following independent variables: (1) clinical: age, sex, actual smoking (yes/no), pack years, diagnosis (aggressive/chronic periodontitis), jaw (maxilla/mandible), site (interproximal/buccal or oral), tooth type (anterior/premolar), therapy (none/SRP/AF), and PlI and GI at baseline, (2) radiographic: interproximal bone loss in percent, infrabony defect, and double contour of the root. For the analysis including radiographic parameters, the variable “site” (interproximal/buccal and oral) dropped out because only interproximal sites remained in the analysis. A probability p < 0.15 was required for parameters to be kept within the models.
Results
All 41 patients contributing 700 single-rooted teeth with 4,200 sites finished the 3-month re-examination. The patient characteristics (age, diagnosis, smoking status) are given in Table 1. From baseline to the 3-month examination, two single-rooted teeth were lost: one to an acute periapical periodontitis and another because of prosthodontic planning. After the 3-month re-examination, one patient left the study. Only sites were included into the analysis, which could be assessed at all three examinations: n = 4,146 in 40 patients.
Table 1Study population as related to age, sex, smoking habit, and diagnosisVariableNumber (n = 41)PercentAge45.9 ± 10.9SexFemale2253.7SmokingActive1946.3Former1229.3Never1024.4DiagnosisAggressive819.5
Reproducibility
The results of the intraexaminer reproducibility of PPD and RAL measurements as standard deviation of single measurement for each examination time point are given in Table 2.
Table 2Intraexaminer reproducibility at baseline, 3, and 6 months examinationExaminationMeasurements (n)s (RAL-V)s (PPD)Baseline8,4000.490.493 months8,3760.440.396 months8,2920.530.39s Standard deviations of a single measurement
Baseline data
The mean clinical parameters (RAL-V, PPD, PlI, GI) at baseline over all sites are given in Table 3. The respective data as related to therapy (no therapy, SRP, AF) are given in Table 4. Whereas no statistically significant differences for PlI were observed between the groups, RAL-V, PPD, and GI of the SRP and AF sites revealed to be significantly (p < 0.001) greater as compared to untreated sites (Table 4). Clinical parameters as related to jaw, tooth type, and site are given in Table 5. Baseline RAL-V and PPD were statistically significantly (p < 0.001) greater in the maxilla than in the mandible, whereas for PlI, it was vice versa (Table 5). For tooth type, just baseline PPD was statistically significantly (p < 0.001) different between premolars and anteriors with deeper pockets at the premolars (Table 5). All baseline clinical parameters were observed to be statistically significantly (p < 0.001) greater at the interproximal than at the buccal and oral sites (Table 5).
Table 3Clinical parameters at baseline, 3 and 6 months after therapy (mean ± standard deviation) Baseline3 months6 monthsSites4,1464,1464,146RAL-V (mm)5.12 ± 2.204.87 ± 1.874.92 ± 1.84PPD (mm)3.25 ± 1.832.67 ± 1.192.67 ± 1.20GI0.78 ± 0.970.51 ± 0.860.51 ± 0.86PlI0.16 ± 0.510.32 ± 0.700.37 ± 0.74Table 4Clinical parameters at baseline as related to therapy (mean ± standard deviation)SitesNo therapySRPAF1,440Range2,478Range198RangeRAL-V/mm4.35 ± 1.82*1.25–19.005.55 ± 2.301.75–18.005.39 ± 2.022.25–12.00PPD/mm2.45 ± 1.13*0.25–2.753.66 ± 1.980.50–12.253.98 ± 2.021.00–10.50GI0.48 ± 0.84*0.94 ± 1.001.02 ± 0.98PlI0.15 ± 0.490.16 ± 0.530.14 ± 0.49SRP Scaling and root planning, AF access flap*Statistically significantly different from SRP and AF with p < 0.001Table 5Clinical parameters at baseline as related to jaw (maxilla/mandible), tooth type (anterior/premolar), and site (interproximal/buccal and oral) (mean ± standard deviation) Maxillamandiblepremolaranteriorinterproximalbuccal/oralSites1,9262,2201,5902,5662,7641,382RAL-V/mm5.24 ± 2.14*5.00 ± 2.265.19 ± 2.20*5.07 ± 2.225.37 ± 2.26*4.60 ± 2.01PPD/mm3.55 ± 1.88*3.00 ± 1.783.47 ± 1.88*3.12 ± 1.813.67 ± 1.82*2.43 ± 1.59GI0.80 ± 0.98*0.76 ± 0.960.83 ± 0.97*0.75 ± 0.960.89 ± 0.98*0.56 ± 0.89PlI0.11 ± 0.43*0.19 ± 0.570.14 ± 0.48*0.17 ± 0.530.18 ± 0.54*0.11 ± 0.44*Statistically significantly different with p < 0.001
Treatment effect
The healing phase passed uneventfully for all patients. Clinical parameters as related to therapy after 3 and 6 months are given in Table 6, and their change after 3 and 6 months is given in Table 7. Whereas in untreated sites, the study failed to observe any significant change, SRP and AF resulted in PPD reduction and PAL-V gain after 3 and 6 months (p < 0.001; Table 7).
Table 6Clinical parameters at 3 and 6 months after therapy as related to therapy (mean ± standard deviation) 3 months after therapy6 months after therapyNo therapySRPAFNo therapySRPAFSites1,4402,4781981,4402,478198RAL-V (mm)4.37 ± 1.765.13 ± 1.905.14 ± 1.644.47 ± 1.765.17 ± 1.855.11 ± 1.61PPD (mm)2.33 ± 0.962.84 ± 1.253.09 ± 1.342.35 ± 1.052.83 ± 1.242.99 ± 1.27GI0.36 ± 0.760.58 ± 0.900.69 ± 0.940.36 ± 0.760.58 ± 0.900.65 ± 0.93PlI0.22 ± 0.560.36 ± 0.740.52 ± 0.890.31 ± 0.680.41 ± 0.780.27 ± 0.65SRP Scaling and root planing, AF access flapTable 7Change of clinical parameters at 3 and 6 months after therapy as related to therapy (mean ± standard deviation) 3 months after therapy6 months after therapyNo therapySRPAFNo therapySRPAFSites1,4402,4781981,4402,478198RAL-V (mm)0.03 ± 0.740.41 ± 1.11*0.26 ± 1.06*0.12 ± 0.940.38 ± 1.20*0.28 ± 1.18*PPD (mm)−0.11 ± 0.72−0.82 ± 1.33*−0.89 ± 1.25*0.09 ± 0.87−0.82 ± 1.40*−0.99 ± 1.41*GI−0.13 ± 0.97−0.36 ± 1.14*−0.33 ± 1.14*−0.13 ± 1.03−0.36 ± 1.18*−0.36 ± 1.44*PlI0.08 ± 0.690.20 ± 0.82*0.37 ± 0.97*0.16 ± 0.750.25 ± 0.87*0.13 ± 0.68*SRP Scaling and root planing, AF access flap*Statistically significantly different from no therapy with p < 0.001
Prognostic factors
RAL-V gain was less favorable in current smokers, in aggressive periodontitis, and at interproximal sites (Table 8). PPD reduction was poorer in current smokers, at premolars, in the maxilla, and at interproximal sites (Table 9). Whereas baseline PPD was related to better PPD reduction and RAL-V gain (p < 0.0001), baseline RAL-V was related to better RAL-V gain but to less favorable PPD reduction (Tables 8 and 9). Baseline PlI was associated with poorer PPD reduction (p < 0.15; Table 9). AF and SRP (p = 0.0114) were associated with better PPD reduction (Table 9).
Table 8Backward multilevel linear regression analysis—dependent variable: RAL-V reduction 6 months after therapy, n = 40 patients, 4,146 sites EstimateSEdfF valuep valueIntercept−1.87760.106837Current smoking−0.28750.11063,4276.760.0094Site (interproximal)−0.23410.02773,42771.28<0.0001Aggressive periodontitis−0.29030.13083,4274.930.0265Baseline PPD0.27460.01583,427303.72<0.0001Baseline RAL-V0.18320.01413,427169.61<0.0001Table 9Backward multilevel linear regression analysis—dependent variable: PPD reduction 6 months after therapy, n = 40 patients, 4,146 sites EstimateSEdfF valuep valueIntercept−1.64870.103738Current smoking−0.33120.10553,4519.860.0017Jaw (maxilla)−0.12990.03243,45116.05<0.0001Site (interproximal)−0.36640.02623,451195.10<0.0001Tooth type (premolar)−0.05010.03383,4512.200.1381Baseline PPD0.61620.01463,4511774.31<0.0001Baseline RAL-V−0.03540.01283,4517.630.0058Baseline Plaque Index−0.03680.02443,4512.270.1318Scaling and root planing0.11710.03923,4514.480.0114Access flap0.09970.08613,4514.480.0114
Taking radiographic parameters into consideration, current smoking resulted in less favorable and baseline PPD in better RAL-V gain and PPD reduction, respectively (Tables 10 and 11). Further, tooth type (premolar) and aggressive periodontitis were associated with poorer RAL-V gains (Table 10). Location in the maxilla and baseline PlI resulted in less favorable PPD reduction (Table 11). Generally, sites with greater interproximal bone loss demonstrated poorer RAL-V gain (p = 0.0001), and sites with infrabony defects were associated with inferior PPD reduction (p < 0.0001; Tables 10 and 11).
Table 10Multilevel linear regression analysis—dependent variable: RAL-V reduction 6 months after therapy, n = 36 patients, 1,796 sites EstimateSEdfF valuep-valueIntercept−1.82900.138533Current smoking−0.37580.13341,3137.940.0049Tooth type (premolar)−0.07630.05021,3132.310.1292Aggressive periodontitis−0.33110.16351,3134.100.0431Baseline PPD0.23710.02561,31385.86<0.0001Baseline RAL-V0.26370.02421,313118.36<0.0001Bone loss in %−0.01150.00161,31350.58<0.0001Table 11Multilevel linear regression analysis—dependent variable: PPD reduction 6 months after therapy, n = 36 patients, 1,796 sites EstimateSEdfF valuep valueIntercept−2.07710.136434Current smoking−0.46460.11971,31315.080.0001Jaw (maxilla)−0.14690.04331,31311.510.0007Baseline PPD0.62860.01191,3132791.95<0.0001Baseline Plaque Index−0.05500.03321,3132.750.0097Infrabony defect−0.29320.06711,31319.10<0.0001
Discussion
Study population
Patients treated in this study ranged from 23 to 71 years of age with chronic and aggressive periodontitis. Original measurements were performed in the setting of a randomized placebo-controlled clinical trial evaluating the effect of a subgingivally delivered 14% doxycycline gel at the Section of Periodontology, Department of Conservative Dentistry, Clinic for Oral, Dental and Maxillofacial Diseases, University Hospital Heidelberg. Each patient had to provide three single-rooted teeth that qualified as test teeth for the doxycycline study. To blind the examiner for the test teeth, not only those but all single-rooted teeth were assessed in all patients [8]. Despite the test teeth and their direct neighbors, all single-rooted teeth were treated according to the following criteria: Teeth exhibiting PPD < 3 mm were treated neither by subgingival SRP nor by AF. SRP was performed when PPD ≥ 3 mm was present. AF was chosen for teeth exhibiting PPD > 6 mm [21]. However, teeth directly adjacent to test teeth were treated only by SRP irrespective of baseline PPD. Thus, also some sites with PPD > 6 mm were treated exclusively by SRP. Further, the decision to perform AF was taken per tooth and not per site. Thus, also sites with PPD ≤ 6 mm were treated by AF, if they were located at a tooth with one or more sites with PPD > 6 mm. Thereby, effectiveness of SRP and AF may be analyzed across the limits of indications as the ranges of PPD for the three treatment groups in Table 4 demonstrate.
How could we exclude that the topically delivered doxycycline had any influence on the treatment results of the sites that were evaluated in this study? The subgingivally delivered agent or vehicle control may be partially absorbed and thereby have systemic effects at the other test teeth. A pharmacokinetic study had found doxycycline only in the blood of 1 of 16 patients [18]. Thus, a systemic additional effect on the other teeth is quite unlikely. It has to be kept in mind that in the sample investigated in this study, only one tooth of the whole dentition per patient received the active agent, i.e., doxycycline [8]. Further, amounts of the subgingivally delivered substance may leave the pocket via sulcus fluid and affect the other test teeth. Split-mouth studies designed to compare active agent and vehicle of topical antibiotics have made the provision that teeth selected as test sites should be separated by at least one tooth [8, 12], minimizing the interaction between therapy modes. In a pharmacokinetic study from control sites, much smaller amounts of doxycycline could be detected in the gingival crevicular fluid than from another site that had received the particular doxycycline gel subgingivally in the same dentition [20]. Thus, it is unlikely that the topical doxycycline had any additional effect on the treatment results of all teeth but the test teeth.
Treatment effect
The results observed in this study after SRP are in agreement with observations reported by other authors 3 and 6 months after nonsurgical debridement of single-rooted teeth [2, 6]. Our PPD reductions and RAL-V gains achieved 6 months after therapy confirm data by a meta-analysis on nonsurgical vs surgical periodontal therapy that reports PPD reduction of 1.07 mm and vertical attachment (PAL-V) gains of 0.6 mm at sites with baseline PPD 4–6 mm 6 months after SRP. However, PPD reductions 6 months after AF for mean baseline PPD of 5.4 mm were 1.0 mm which is less than the meta analysis lists for baseline PPD 4–6 mm: PPD reduction 1.37 mm. PAL-V gain after AF was 0.3 mm which comes quite close to the 0.31 mm reported by the meta analysis [15]. Serino et al. report results 12 months after treatment [28]. For baseline PPD 4–5 mm they report PAL-V gains of 0.31 mm and PPD reduction of 1.1 mm after non-surgical as well as 0.21 mm and 1.6 mm after surgical therapy. This is quite similar to the results of this study regarding PAL-V gain and PPD reduction after SRP. However, the PPD reduction after surgical therapy is more favorable than ours [28].
Prognostic factors
Current smoking was generally associated with less favorable PPD reduction and RAL-V gain in all models. Smoking is the most significant external risk factor for periodontitis [5, 13, 29] and is known to deteriorate the results of periodontal therapy in general [7, 30]. However, smoking was the only patient-associated factor that was kept in all models. The diagnosis of aggressive periodontitis was associated with less favorable RAL-V gains, whereas it was not kept in the models to explain PPD reduction. It is interesting to note that the other patient-associated factors, i.e., age and sex, were kept in neither model. This confirms observations of D’Aiuto et al. [5].
It is interesting to note that the diagnosis of aggressive periodontitis affected RAL-V gains but not PPD reduction. It seems that patients suffering from aggressive periodontitis have a higher risk for recessions than patients with chronic periodontitis.
Several tooth- and site-associated factors were identified by multilevel analysis to influence clinical outcomes. Generally, baseline PPD was related to better PPD reduction and RAL-V gain (p < 0.0001). PPD reduction and RAL-V gain was less pronounced in the premolars and at interproximal sites (p < 0.15), and PPD reduction was less pronounced in the maxilla (p < 0.001). These results are plausible because compared to anterior teeth, premolars are less accessible and interproximal sites are more difficult to debride than oral and lingual sites. Less favorable PPD reduction in premolars than in incisors was also recently reported by other authors [5]. However, D’Aiuto et al. observed more favorable PPD reduction at interproximal sites, whereas this study observed the contrary. The multilevel analysis performed in this study was adjusted for baseline PPD. Baseline pockets were deeper interproximally than at buccal or palatal/lingual sites. This might explain more favorable PPD reduction at interproximal sites without adjusting for baseline PPD. Considering the different therapies, SRP and AF provided better PPD reduction than no therapy. However, the analysis failed to reveal statistically significant differences between both therapies in single-rooted teeth. It seems that AF provides no advantages over SRP in single-rooted teeth.
Taking radiographic parameters into consideration, current smoking and baseline PPD were kept in the models. However, the greater the interproximal bone loss, the poorer the RAL-V gain (p < 0.0001), and infrabony defects were associated with inferior PPD reduction (p < 0.0001). Total amount of bone loss seems to be associated with poor prognosis of the respective tooth generally irrespective of the type of treatment. This has also been observed for long-term stability [17]. D’Aiuto et al. [5] did not assess radiographic parameters. However, they considered tooth mobility and found mobility was correlated with less favorable PPD reduction. It is interesting to note that interproximal grooves that had been assessed as root double contours failed to influence the outcomes of therapy. Up to our best knowledge, this is the first analysis on the influence of baseline bone loss on the outcome of nonsurgical or surgical periodontal therapy that does not use patient means but individual tooth parameters.
Within the limitations of the present study the following conclusions may be drawn: (1) Nonsurgical and surgical periodontal therapies are effective in single-rooted teeth; (2) severe interproximal bone loss and infrabony defects deteriorate the clinical results, and (3) there seem to be more defect-associated (tooth, site) factors influencing treatment outcome than patient-associated factors.

periodontal therapy
single-rooted teeth
smoking
clinical trial
surgical/nonsurgical therapy


Internet Usage by Low-Literacy Adults Seeking Health Information: An Observational Analysis

Background Adults with low literacy may encounter informational obstacles on the Internet when searching for health information, in part because most health Web sites require at least a high-school reading proficiency for optimal access.
Introduction
Although a tremendous volume of educational health materials is disseminated in the United States, not all Americans find this information accessible or usable. In particular, adults with poor health and low functional literacy face great risks of poor health outcomes and preventable disease progression [1-4]. While many low-literacy adults could benefit from enhanced health knowledge, most current health education materials are written at a 10th grade or higher reading level [3]. Inability to access or understand health education materials inhibits important preventive or treatment measures, and may decrease the likelihood of identifying a symptom of disease. Low health literacy is also a barrier to enrollment in clinical trials [5,6] and minimizes adherence to instructions given by health professionals [7]. These obstacles are compounded by low income levels pervasive in the undereducated population [1], which can prevent individuals from pursuing regular primary care, paying health insurance premiums, or purchasing medications when prescribed. Collectively, these factors help to explain why low-literacy adults are twice as likely to be hospitalized as individuals with high functional literacy [8].
The expense of poor health and low functional literacy on the health system is estimated at $73 billion each year [9]. High cost estimates have encouraged many health-care providers to search for innovative ways to improve health literacy. The Internet has been embraced as an easy-to-use, convenient, and comprehensive clearinghouse for information on diseases, disorders, treatments, and preventions. Even when receiving physician care, between 40% and 54% of medical patients use the Internet to learn about treatment options and tobetter understand their medical conditions [10].
However, the low-literacy population has largely been excluded from the veritable boom of Internet health resources. The expense of Internet services and personal computers may be too high for this population. In addition, most text-based health information on the Internet is too advanced to be optimally effective for low-literacy populations. On average, Internet health-education materials are written at a 10th grade or higher reading level, and 100% of English-language health Web sites examined in a 2001 study required at least high school-level reading proficiency [11,12]. Another study concluded that of 1000 Web sites reviewed, only 10 had a level of writing and content accessible to low-literacy adults [13]. Kalichman et al suggest that individuals who read English below a 6th grade level are not likely to make effective use of the Internet [14]. Further, Zarcadoolas et al report that complex Web features, such as animated links, may be challenging for low-literacy adults to identify and utilize [15]. The 1992 National Adult Literacy Survey (NALS) revealed that more than 90 million Americans either read at a low-literacy level or are functionally illiterate [1]; the paucity of Internet health resources appropriate for these individuals perpetuates discrepancies in health outcomes between the educated and undereducated.
While no studies to date have determined how many low-literacy adults regularly use the Internet to find health information, the dearth of educational materials suitable for these individuals may impair optimal usage and navigation. One study has reported interventions that enabled low-income HIV-positive individuals to use the Internet and to critically evaluate information that they encountered [16]. Health-related Internet use has also been shown to enhance knowledge about HIV and to be correlated with active coping in a study of HIV-positive patients [17]. Although these studies focus on low-income status rather than low-literacy status, the established correlation between these two factors suggests that low-literacy adults may likewise benefit from augmented health education via the Internet.
We conducted an observational study of low-literacy adults to assess how they searched for Internet health information in as close to a natural setting as possible. Our investigative questions include the following: if low- to mid-level literacy adults are given access to the Internet, can they find basic health information that they can understand? Will their search strategies be effective in identifying information that they can use and comprehend? How do they rate current health Web sites in relation to their needs and interests? Will they be able to conduct successful self-directed searches? In our investigation, we also categorized navigational strategies used by low-literacy adults and the reading level of materials they accessed.
Methods
We enrolled 13 adult literacy students (3rd to 8th grade reading levels) from Bidwell Training Center, a vocational school in Pittsburgh, Pennsylvania. The protocol used was approved by the University of Pittsburgh Institutional Review Board. Bidwell students are organized individually and/or in small groups for reading instruction; they meet together once a week for program announcements. The literacy program coordinator introduced the study to 20 students in this large-group setting. Thirteen interested students then self-selected into the study. All subjects participated in a computer skills workshop in May 2003, where they were presented with basic search and navigation strategies and learned how to use the Google search engine. We selected Google because it is a widely used search engine and has a "Did You Mean…" feature that corrects misspelled search terms. We anticipated that this might be a feature that low-literacy subjects would find particularly helpful. Among other topics, subjects were taught how to use the "Back" button and the "Forward" button, how to scroll down a page, how to identify links, and how to conduct basic searches. Each subject also filled out a brief questionnaire to give insight on their educational background, ethnicity, health insurance status, and previous experience with computers and the Internet. The questionnaire was written at a 3rd grade reading level (Flesch-Kincaid Reading Scale).
An investigator met individually with each of the participants within 3 weeks of the computer skills course for the observational portion of the study. Participants were 1) administered the REALM test (Rapid Estimate of Adult Literacy in Medicine) [18] to assess their health literacy level; 2) asked several questions to gauge their comfort level on the Internet and prior Internet experiences; and 3) taught how to "think aloud," or continually express their thoughts while using the computer. Investigators engaged each participant in several think-aloud examples in order to actively illustrate this process.
The investigator then asked the participant to use the Internet and Google search engine and think aloud while finding information on a subject of his or her choice. This preliminary question allowed participants to practice and review their Internet searching techniques. Participants were permitted to ask the investigator technical and navigation-related questions during this part of the study. These questions included, but were not limited to, whether to put spaces between words in search terms and how to initiate a search once a search term had been specified.
Participants were then asked to find answers on the Internet to 3 health-related questions developed by members of the research team. Participants were instructed to use the Google search engine so that their answers could be standardized. A committee consisting of a physician, a faculty member specializing in human-computer interactions, a community health educator, and an information sciences specialist compiled various answers to these questions that would qualify as accurate and complete. Subjects who were able to generate any of these answers during their online searches were considered to have answered the questions correctly; subjects who were not able to generate these answers were determined to have answered the question either incorrectly or incompletely. Examples of responses for each question that would have been considered correct are included in the Results section
The investigator read the 3 questions aloud and also provided them to the participant in written form (Arial font, 20 pt):
1. Think of a health question you are interested in for yourself or for someone you know. Find out information about this question on the Internet.
2. Imagine that someone you care about has lung cancer. This person would like to know about treatments for lung cancer. Can you find out the three main types of treatments using the Internet?
3. Imagine that you are at a doctor's office and you are told you have a disease called diabetes (sometimes called sugar). You are given a pill called Metformin to take for it. What does Metformin do?
Subjects identified answers to the investigator, who then asked them to articulate the answers in their own words. Participants who seemed frustrated or unreceptive, or who asked to move to a new question were directed to the next task. Participants were allowed to use any Web sites they felt would help them answer the questions. Participants also were not provided with dictionaries-our objective was to examine how they navigated the Internet without assistance from external sources. Subjects were given up to 15 minutes to complete each task, as measured by the investigator. To minimize anxiety, they were not informed of the time limitation. After the 15-minute period, investigators used a series of prompts to gradually guide subjects, if necessary, to the next task.
Next, investigators accessed the colon and rectum cancer Web page on the American Cancer Society (ACS) Web site [19]. Participants were asked to navigate through links on this page and find 2 ways to help prevent colon and rectum cancer. Investigators recorded the amount of time spent answering this question and the number of links participants clicked on to find the answers. After this task was completed, investigators asked the participants several subjective questions to qualify their experience on the Internet. Participants were then given $25 compensation, which ended their direct involvement in the study.
Investigators wrote notes on each participant's progress, and asked for participant feedback about the Internet both before and after searching the Internet. Investigators did not coach subjects on proper technical or navigational techniques after the initial practice question until subjects had completed their tasks. In 2 cases, investigators directed subjects to Google's "Did You Mean…" search term correction option in order to adjust for spelling mistakes; these subjects had repeatedly demonstrated very poor spelling proficiency before this intervention.
Camtasia Studio screen-capture software recorded individual keystrokes and think-aloud recordings. Questionnaires and think-aloud methods were used to ascertain the criteria used by participants in evaluating Internet health Web sites. Investigators also calculated the 1) literacy levels of Web sites accessed by the participants, 2) the amount of time spent on each Web site, 3) the number of questions answered thoroughly and correctly by each participant according to pre-determined standards, 4) the average number of sites used to answer each question, and 5) the number of participants who accessed sponsored sites, or paid advertisements appearing on the Google retrievals page, and how many used that information to answer questions.
Results
Qualitative and quantitative results were analyzed in this study.
Participants
In this study, the subject population was reduced from 13 to 8. Two participants were excluded because they did not attend the one-on-one searching session with the investigator. Two other participants were excluded because they were non-native English speakers who did not understand the tasks presented to them. One participant was later excluded because technical problems prohibited the retrieval of her computer searches.
The average age of our 8 remaining participants was 41.5 years. Five subjects were male and 3 were female. Seven identified themselves as African Americans and 1 self-identified as of Asian descent. The Asian participant was an English-as-a-second language (ESL) speaker with a university education from his native country. Seven of the 8 participants reported having health insurance. Seven of the 8 also had at least some high school or trade school education; 1 participant did not report educational experience on the intake questionnaire.
Of these subjects, 2 reported on the intake questionnaire that they had never previously used a computer or the Internet. Two reported that they had previously used a computer, but had not used the Internet. Subjects generally used computers with greater frequency than they used the Internet. Three participants reported on the questionnaire that they used the Internet 2 or more times a week; they later said verbalized that their main online interests were news, sports, cars, and/or entertainment information. The other 5 participants reported on the questionnaire that they used the Internet either occasionally or not at all. Usage reports from the intake questionnaires are provided in Table 1.
Table 1
Self-reported, written questionnaire responses about prior Internet and computer usage by subjects (n=8)
Subject
Have you ever used a computer? If so, how often?
Where do you use computers?
Do you use the Internet? If so, how often?
Where do you use the Internet?
1
No
"No where" [sic]
No
"I've never used the Internet"
2
Less than once a month
"When I was in jail"
No
(N/A)
3
2 or more times a week
"At school, Bidwell Training Center in Ms. Cooper's class."
No
"At the Carnegie Library in Beechview where I live"
4
No
"No"
No
"No"
5
2 or more times a week
"To type"
Yes; Less than once a month
"In school"
6
No; 2 or more times a week
"At home"
Once a week
"At home"
7
2 or more times a week
"Home"
2 or more times a week (at home)
"Home"
8
Once a week
"Different location"
2 or more times a week
"Different location"
As seen in Table 1, the self reports of prior Web and computer experiences are unclear in several cases. Subject 3 reported no prior Internet usage in one part of the questionnaire, but reported in a subsequent answer Web usage at a local public library. In addition, as Table 1 indicates, subject 8 reported more frequent usage of the Internet than of computers; subject 6 (ESL student) first indicated no prior computer usage, then later reported on the questionnaire computer usage of twice a week. Because there were seemingly divergent perceptions of what constitutes a computer or Internet experience, perceived computer/Web adeptness cannot be correlated with our participants' experience using this technology. Therefore, while this study will indicate differences in results between the 3 people with frequent Internet experiences (defined in this study as usage of at least once a week) and the 5 individuals without, the study will not attempt to conclude whether the skill level of subjects in the study correlated with the sustainability of their prior computer and Web experiences.
Search Engine Usage
Participants reviewed their navigational skills during their preliminary question, where they were encouraged to look for information on any subject that interested them. They used Google to search for a variety of topics, ranging from entertainment to health-related information. Participants occasionally searched for information on more than one topic.
Participants used the search items listed in Table 2 in order to answer the preliminary question and questions 1 to 3. Semicolons between words or phrases separate multiple search terms used by a subject to answer a question. The subjects are listed in Table 2 in the same order (ie, 1, 2, 3…) as they appeared in Table 1.
Table 2
Search terms used by subjects to answer preliminary questions and questions 1 to 3 (n=8)
Subject
Preliminary
Question 1
Question 2
Question 3
1
lena horn†
Lung cancer
Lung cancer
Metformin
2
health care;health care mental
Sports and health
health care about lung cancer
A pill called metformin
3
(no clear search topic)
Herpes
Cancer
Metformin
4
Wwwsoulfood; wwwsoulfoodcom; soulfood
AIDS
lung caner†
Diabetes
5
Will Smith; sipers†; spiders
High blood
Lung cancer
Metformin
6**
Bi;;;dwell training center†
Health
health lung caner†
Health diabetes
7
sonny Rollins
Tuberculosis
Treatments for lung cancer
Metformin
8
Babyface recording artist
Pain
Cancer
Pdr*
* Physicians' Desk Reference
** English-as-a Second Language subject
† misspellings for: "lena horne," "bidwell training center," "lung cancer," and "spiders"; the Google correction option was used in two instances when the subject was prompted by investigators to amend search terms.
Questions 1 to 3 were given to our participants in writing, as well as orally; this may have affected their selection of search terms. For question 2, one participant wrote "treatments for lung cancer" in the search term box, a phrase that is written explicitly in that question. Another participant was similarly prompted by the wording of question 3 to write "a pill called metformin" as his search term.
Individuals who used the Internet at least once a week are labeled in Table 1 and subsequent tables as subjects 6 to 8. Search terms generated by these frequent Internet users did not differ greatly from search terms generated by individuals who had little Internet experience. The one exception was subject 8, who attempted to answer question 3 by using the online Physicians' Desk Reference, a site about which she had once heard good reviews.
In general, this group found generating original search terms to be somewhat challenging. Many did not initially remember whether to put spaces between the words in search terms. Even a subject who reported using the Internet once a week hesitated when writing the search term for question 1, finally stating, "Yeah, you do have to space [between words]… I had to remember if you had to space." With one exception, participants were able to correct their terms by inserting the proper spaces.
Spelling of search terms was generally a problem for only 2 participants, one of whom (subject 7) spoke English as a second language. Subjects tended to self-correct for spelling in the search term box before pressing the "Google Search" button or Enter key. Several participants also had difficulty understanding what type of terms to put in. When conducting a preliminary search for information on the television show, Soul Food, one participant typed into the search term box, "wwwsoulfood." When this retrieved no results, the subject looked at the URL for guidance and then typed "wwwsoulfoodcom" into the Google search term box. This again did not yield any results. The participant next entered "soulfood" into the search term box. The investigator finally directed the subject to Google's "Did You Mean…" option so that the subject could answer the question. However, this participant had continued difficulties generating correct search terms; later in the study, he used "lungcaner" as a search term to find information about lung cancer.
Nearly all participants retained skills such as scrolling and clicking on links from the computer workshop or previous Internet experiences. They also learned other navigational strategies through repetition and practice. For example, one participant who was conducting a preliminary search for information about Will Smith looked at the Google retrievals and stated, "So it [search engine] must go to other Smiths ... I wonder if I was supposed to put in 'Will Smith the actor'?" Quickly, the subject had learned that increasing the specificity of search terms generally improves the specificity of results.
Six of the 8 participants did not venture past page 1 of the Google retrievals. One participant was surprised by the number of search results, saying, "You find a lot of stuff on this thing [the Internet]." Another participant explained why she stayed on page 1: "Oh boy, I've got a lot to choose from. I don't want to go to the other ten [pages of retrievals] because it might give me other information I don't really need ... the first page gives me just enough of what I need to know." This participant had deduced that first-page retrievals typically have the most relevant sites to the particular search term used. Later, this subject stated, "I didn't answer the questions, but I looked up the information, and it [Internet] gave me what it wanted me to have." This statement implies that the subject believed that the Internet was more in control of the searching than the subject, revealing a possible belief that the search engine and search terms selected are not the primary determinants of what type of information is retrieved.
Sites Accessed
Ability to Answer Questions
In question 1, participants were asked to use information on the Internet to find the answer to a health-related query of their choice. Most participants identified only a subject area, and did not clearly articulate a specific question despite verbal prompting by the investigators. Several participants initially stated a topic, but changed it as they retrieved unrelated material that they found more interesting. While recordings from the think-alouds would have been helpful in designating the search topics, we found that despite investigators' prompts and encouragement, subjects were very reluctant to verbally report their real-time experiences navigating through the Web. As one subject stated, "Shucks, I can't think aloud." It is therefore difficult to gauge whether participants were able to find adequate information for which they searched, especially during the unstructured searching period required to answer the first question.
Question 2 required participants to locate the 3 main types of lung cancer treatments (acceptable answers: chemotherapy, surgery, radiation). This question models the navigation of a typical Internet health-information seeker who searches for disease-related information. Of all 8 participants, only subject 5 was able to answer this question accurately and completely. Subject 3 verbalized one viable option-chemotherapy-based on information accessed online. The remaining participants either did not answer the question or identified an alternative medicine as one of the principal types of lung cancer treatments available.
Question 3 required participants to find out the role of metformin, or Glucophage, in diabetes treatment (one acceptable answer: metformin lowers sugar in the blood). This question models a doctor-patient interaction in which a patient who is prescribed an unfamiliar medication independently searches for information about its effects. Six of 8 participants were unable to find information on the Internet to answer the question. The 2 participants, subjects 3 and 7, who found the information, read directly from text on the site and did not articulate the information in their own words.
Surprisingly, subjects who reported sustained prior Internet experience in the questionnaire were no more successful at answering questions than subjects with little Internet experience. This could have been a result of the generalized search terms that they used to look for answers. Prior Internet experience does not seem to lead to satisfactory search/navigation skills for members of this group in searching for health information.
Information Accessed
Sites used by subjects 3, 5, and 7 to successfully answer questions 2 and 3 were written at a 12th grade reading level (Flesch-Kincaid). It is noteworthy that these subjects were able to identify the answer in the text and read it aloud. In 2 out of 3 cases, they were unable to express these answers in their own words, which suggests a minimal comprehension of the material accessed.
Seven of the 8 participants accessed sponsored site information while attempting to answer questions. Businesses pay a service fee to Google to have their site names appear as sponsored sites when triggered by a particular search term or keyword. Sponsored sites are outlined in color and/or appear in boxes on the right side and heading of the Google retrievals page. In general, alternative treatments and commercial therapies and medications appear under this listing; many of these sites may contain information that is uncorroborated by legitimate scientific sources.
Five participants used information provided by the sponsored sites to answer questions. Two out of 3 of the subjects who used the Internet at least once a week also used this information to answer questions. Half of the participants searching for lung cancer cures arrived at the same site: an Asian dietary supplement site claiming to cure cancer by removing free radicals from the body [20]. Another popular sponsored site promoted a radio frequency technique to hinder cancer progression [21]. The titles of these sites as they appeared in the sponsored sites submenu were: "New Cancer Treatment" and "Cancer Treatment." The Flesch-Kincaid formula indicated that the information on both sites was written at a 12th grade or higher reading level. Information on sponsored sites, therefore, was not necessarily any easier to read or interpret than information on non-sponsored sites accessed by subjects in this study.
General Site Profiles
Observational logs and records on the Camtasia software show little correlation between our subjects' ability to identify answers and the amount of text on a page; analysis using the Camtasia software also showed little conclusive difference in the amount of time that the subjects spent on each site despite variances in the amount of text on the pages accessed. Therefore, subjects did not seem to prefer or navigate towards Web pages/sites with less text.
Participants, on average, used between 1 and 2 Web sites to answer questions 1 to 3. Table 3 records the number of links from the Google retrievals page that were selected by subjects. The results for subjects 1 to 5-the participants with minimal prior Internet experience-are also presented separately from the results for participants with sustained prior Internet experience (subjects 6 to 8).
The Flesch-Kincaid reading scale used in this study scores text at a 1st to 12th grade reading level. Given this scale, sites ranked at the 12th grade level require at least that level of reading ability. That is, material scored at a 12th grade level may actually be written at a college level. In our study, the average site accessed required at least a 10th grade reading level.
Table 3
Average number of links used to answer questions
Avg. Number of Links Used (Average Total)
Avg. Number of Links Used (Subjects 1-5)
Avg. Number of Links Used (Subjects 6-8)
Preliminary
1.875
2.4
1.0
Question 1
1.14
1.2
1.67
Question 2
1.82
1.8
2
Question 3
1.5
1.6
1.33
AVG.
1.58
1.75
1.5
Table 4
Average (rounded) reading level of sites accessed
Avg. Reading Level of Sites Accessed
Avg. Reading Level of Sites Accessed (Subjects 1-5)
Avg. Reading Level of Sites Accessed (Subjects 6-8)
Preliminary
10.50
10.7
10.0
Question 1
10.50
9.4
11.2
Question 2
11.1
11.3
11.0
Question 3
11.8
11.8
11.9
AVG.
11.0
10.8
11.0
Table 5
Average time spent on sites
Avg. Total Time Spent Per Site (min)
Avg. Total Time Spent Per Site (Subjects 1-5)
Avg. Total Time Spent Per Site (Subjects 6-8)
Preliminary
7.2
8.7
4.7
Question 1
10.3
10.6
9.8
Question 2
8.7
8.7
8.7
Question 3
6.6
8.3
5.8
AVG.
8.2
9.1
7.25
Participants spent an overall average of 8.2 minutes on individual sites. All participants voluntarily finished answering questions 1 to 3 before the 15-minute time limit was reached.
After completion of these first 3 questions, subjects were directed to a specific site; question 4 was posed about information directly linked to that site. We chose to use the ACS colon and rectum cancer Web page site, which contains links to a variety of prevention resources written at 6.3-12.0 grade levels (Flesch-Kincaid Reading Scale). The page to which we directed subjects consists of a listing of links to defined topic areas, one of which was closely related in wording to question 4. On the ACS site, 5 out of 8 people were able to answer question 4 correctly. Three of the 5 reported prior Internet experience; 2 reported none. These subjects used 3.8 links on average to answer the question. The 3 subjects who did not access the material used 6.5 sites on average before they were either stopped by the investigator or quit voluntarily. Two of these subjects had never used the Internet prior to enrollment in the study.
Attitudes and Self-reporting
While most participants were unable to answer all of the questions asked, 7 out of 8 reported feeling very comfortable or comfortable with their Internet searching experience. The eighth participant felt moderately comfortable. Also, 5 out of 8 found it at least moderately easy to find readable and understandable information on the Internet. Two of the remaining participants found it very difficult to find readable information, and one participant reported that finding understandable information is easy if the Web user has strong reading skills.
Despite their dependence on sponsored sites and alternative Web sites to answer questions, 7 out of 8 subjects reported that they found it very easy to locate trustworthy information on the Internet. The eighth subject noted that it is moderately easy to find information that is trustworthy on the Internet. However, one subject said, "I believe that on the Internet, you have your shysters ... just like anything."
Subjects felt positive about continuing their online experiences, and all expressed some enthusiasm about improving their skills. One participant stated, "I'm getting a computer ... it can help your typing skills." Another subject said, "The computer is real interesting. I'm a see if I can get one so I can learn [how to use it]." After the study was completed, many participants asked investigators to continue teaching them Internet skills or to continue helping them locate Internet resources on a variety of subjects.
Discussion
This observational study is the first to examine Internet use by low-literacy adults seeking health information [11]. Irrespective of prior experience using the Internet and/or computers, low-literacy adults participating in our study did not use optimal search terms to answer questions, encountered difficulties finding health information at the appropriate reading level, and were unable to successfully interpret Internet health information as it was presented. While basic navigational skills (eg, using the "Back" button) were easily retained, areas that required reading and comprehension were problematic for most subjects-evidenced by their inability to answer questions and comments made during their think-alouds. Therefore, the literacy level needed to read health information on the Internet does appear to inhibit information-seeking efforts of low-literacy adults.
Searching strategies were sub-optimal in several respects. First, the search terms used by subjects were predominately non-specific (Table 2). Although we anticipated that subjects who used the Internet more often would generate more specific search terms than did their peers, we did not observe this in the study.
Difficulty Generating Search Terms
Without guidance, subjects had difficulty generating original search terms that would yield specific results. A recent study reveals that adolescents used similarly general search terms when searching the Internet for health information [22]; this corroborates results from another study, which found that among subjects with an average of 33 months of Internet experience, self-selected search terms to find health information were unexpectedly general [23]. These observations highlight search terms as a potential barrier to specific, targeted Internet health information for different types of Internet users with varying levels of Web expertise. A categorizing search engine might be particularly effective for use by these groups; it minimizes the need for individuals to both create a specific search term and independently read and assess all retrievals. A sample search to answer question 2 was conducted using the Vivisimo search engine [24]. The search term "lung cancer" yielded a series of folders about lung cancer separated by subject matter; one folder specifically focused on lung cancer treatments. Individuals clicking on that option could access all sites on lung cancer treatments retrieved by the engine, circumventing the need to sift through thousands of retrievals to locate treatment-focused sites. A future study could monitor the ease with which low-literacy individuals could conduct self-directed searches using an automatically sorting search engine.
Reluctance to Use Links
Search strategies observed in this study were also sub-optimal because most subjects exhibited some unwillingness to click on links to Web sites on the Google retrievals page. On average, subjects clicked on one to two links to answer questions. Even when the subjects did not appropriately answer questions or only partially answered questions, most seemed reluctant to click on additional links on the Google retrievals page, and 7 of 8 did not go to subsequent retrievals pages. These results did not seem to correlate with prior Internet experience. Subjects also rarely re-typed search terms in order to access more relevant retrievals. These results differ from those of a previous observational Internet study, whose participants preferred to choose links from page-one retrievals and then re-type original search terms if they were unable to find appropriate information [23]. As stated earlier, our subjects had such difficulty generating original search terms, figuring out appropriate spelling, and determining whether to place spaces between words in search terms, it is conceivable that this is why they avoided this strategy.
Another reason why subjects' generation of search terms and selection of links were so limited may have been because the subjects were not interested in the health materials or the questions. Subjects may have also found the Google retrievals page confusing and intimidating. While the think-alouds are inconclusive about which of these factors contributed most to the weak search strategies observed, the post-session questionnaire reveals that the majority of participants reported that it was easy to search the Internet. Future research may help to illuminate the factors that contribute to the inconsistencies between subjects' perceived unwillingness to explore the Internet's health resources and their positive feedback about navigating through these resources.
High Literacy Levels of Health Web Sites
The health sites participants accessed to answer questions 1 to 3 had, on average, an 11th grade reading level (Flesch-Kincaid Reading Scale), which was consistent with the findings of previous studies [3,25]. Clearly, all of our subjects experienced difficulties using these sites to answer questions. The literacy level of the materials that the subjects did access may have limited their ability to read and understand materials as presented to them, and may have also impaired their ability to select the appropriate links for finding information. However, a majority of subjects were able to find specific information on the ACS Web site. As one subject reported about the site, "This is a real good one 'cause it breaks it right down for you." This Web page consisted of a series of links: general links on the left and right sides of the page and links to colorectal cancer in the center. Subjects who were unable to answer the questions seemed to find the lists of links on the page confusing, and picked links that took them to unrelated pages on the ACS site rather than to specific pages containing colon and rectum cancer information. While the selection of only 1 link on the colon and rectum cancer Web page was necessary in order to answer the question, these subjects on average picked more than 6 separate links before quitting. Therefore, layout of health Web sites evidently affects the ability of low-literacy adults to find pertinent health information.
Despite the navigational difficulties observed on the ACS Web page, the ability of 5 subjects to correctly answer question 4 probably resulted from the fact that the information needed to answer question 4 was written at an 8th grade reading level-significantly lower than the11th grade reading level required on average to read information retrieved in the first 3 searches. This suggests that low-literacy individuals can identify and utilize easier-to-read materials on Web sites. The Internet may indeed be a useful health resource to this population if materials are written at an appropriate reading level. Considering the navigational struggles of our subjects, the actual process of locating low-literacy sites on the Web may prove a more daunting challenge to this population.
Difficulty Measuring Participants' Comprehension of Information
While most were able to competently navigate through lower literacy materials, subjects' comprehension of Internet health information was difficult to measure in our study. Some participants found correct answers and read them to the investigators directly from the Web text, but none were able to articulate the answer in their own words when prompted. In their analysis of the1992 National Adult Literacy Survey (NALS) results, Kirsch et al reported that low-literacy adults may successfully perform simple comprehension exercises such as locating a single piece of information from text, but often find it more difficult to integrate and synthesize that information [1]. Furthermore, subjects in our study may have been able to use cues from sentence structure to locate an answer, and then relied on their pronunciation skills in order to read the answer as written. However, their ability to identify relevant health information within text is not necessarily a measure of their ability to comprehend that information.
In addition, several subjects seemed to compensate for their low literacy skills by using external information resources. One subject who examined a Web site on mental health law (12th grade level) expressed great enthusiasm about a particular topic that he said was presented on the site. A perusal of the site after the session showed that this topic was not addressed on any of the pages he had accessed. This participant may have compensated for his struggles in reading the site by citing facts with which he was personally familiar. Another subject used a similar approach when accessing a lung cancer site. When asked about the type of information he was reading, the subject responded that the page focused on smoking cessation. However, there were no smoking-related topics on the pages examined by the subject. The subject was able to correlate lung cancer with smoking, and may have relied on this information in order to answer the investigator's query. Overall, some subjects may have been able to rely less on actual comprehension skills and more on background knowledge in order to infer answers.
Positive Web-site and performance feedback reported by most of the participants could have also been fueled by a desire to compensate for reading and comprehension difficulties. Participants were aware that the majority of the investigators were affiliated with a local hospital system; some may have felt compelled to answer positively about Internet health information because they were reporting to health-care professionals. Additionally, the participants may have been unwilling or ashamed to admit that they had difficulty understanding the information on the Internet. Individuals with low literacy tend to be embarrassed by their reading inadequacies [26]. Participants may have felt compelled to report more positively about their Internet experiences in order to de-emphasize their difficulties navigating the Web. These considerations might begin to explain that while most participants struggled when using the Internet, most 1) felt they did a good job searching for information, and 2) found information on the Internet readable and understandable. Collectively, then, poor comprehension of health information on the Internet coupled with a desire to compensate for self-perceived inadequacies in reading may have negatively affected the ability of our subjects to objectively evaluate Web sites. In this study, these factors may also have diminished the accuracy of their think-alouds and feedback in relation to their actual Internet experiences.
Inaccurate Self-assessment
An alternative reason why subjects reported positive experiences on the Internet could be that subjects were unaware of the magnitude of their Internet searching difficulties. A study by Moon et al indicates that 70% of subjects told investigators that they read "really well," while in actuality, their mean REALM scores reflected a 7th to 8th grade reading level [27]. This suggests that individuals may actually overestimate their reading ability in relation to standard educational parameters; it may also relate to a similarly heightened perception of Internet competence. Furthermore, because the majority of our subjects had minimal Internet experience, they may not have been able to objectively gauge the limitations of their Internet skills in relation to the skills of more advanced users. While the investigators were able to categorize their searching as sub-optimal, our participants could have considered their searching strategies to be adequate, if not standard.
Preference for Sponsored Sites
Subjects' reliance on sponsored-site information to answer questions, regardless of the high literacy level required to read those sites, suggests that other factors promote the selective advantage of sponsored sites over non-sponsored sites. In fact, the design of sponsored sites on the Google retrieval page follows many of the guidelines for creating optimal layouts for health information targeted to low-literacy adults [28]. First, the sponsored sites are organized by topic, and are also segmented in colored boxes that stand out from the rest of the Google retrievals. They do not contain the "teaser information" and keywords associated with normal Google links, and minimize the amount of text used. Most are easier to read than the normal Google links, are automatically categorized by subject, and are visually stimulating. In addition, despite misspellings of search terms, sponsored sites are often applicable to the intended subject. For example, a search of "lung caner" instead of "lung cancer" yields sponsored sites on lung cancer, though most of the non-sponsored Google retrievals are irrelevant. When individuals misspell search terms, which the low-literacy subjects in our study did fairly commonly, they might easily gravitate to sponsored-site information to answer their health questions.
Of concern is that subjects did not seem to differentiate between the information on the sponsored sites and information on non-sponsored sites. Subjects used these sites interchangeably to answer questions. One study suggests that critical interpretation of Web sites is based on the Internet acumen and interests of the information-seeker; if coupling the motivation to find a topic and the ability to do so successfully, the information-seeker will be well-equipped to evaluate Web sites objectively and perceptively [29]. This approach offers 3 possible explanations for our results. First, our questions may have been of little interest to our subjects; this may have diminished their motivation in answering questions and affected impacted their critical analysis of sites. Second, many of our subjects had little sustained exposure to various Web sites before the study. Those subjects in particular may not have been able to critically compare Web sites as readily as individuals who had previously seen both good and bad Web sites and developed their own rating system. In this context, most health information on the Internet may have seemed trustworthy and interchangeable to some of the subjects. Third, the searching problems observed even among those subjects with previous Internet experience underscore the fact that none of these subjects reported that their prior Web usage included searches for health information. While these subjects had successfully found items of personal interest in previous Web searches, they were unable to navigate to health materials that were any more accurate or easy-to-read than those found by the rest of the subjects. Therefore, health searches may present unique challenges to a low-literacy population that counter the ability to find accurate, trustworthy health information. This may result from the high literacy level required for reading health information and health Web sites in addition to the complexity of health terminology.
Limitations of Methodology
Standard methodologies used in this study to determine health literacy and to generate continual feedback were sub-optimal. First, REALM test results were inconclusive. Subjects were placed into the literacy program at Bidwell Training Center after taking the national Tests for Adult Basic Education (TABE). However, in our study, these subjects tested significantly higher on the REALM than expected for individuals with the reading levels indicated by their TABE scores as reported by Bidwell Training Center (3rd to 8th grade reading skills). Subjects may have strong phonetic skills that help compensate for poor word recognition and comprehension. This observation is supported in a study by Wilson et al [30], which similarly noted that lower literacy participants who used the REALM tested at several grade levels above their actual reading level. The REALM may not be an optimal tool for accurately determining the health literacy of low-literacy adults.
Whereas complete think-alouds could have helped us better understand subjects' navigational priorities and comprehension levels, the protocols we used in this study were ineffective at prompting verbalization. None of the participants consistently articulated their step-by-step navigational process at all points during their searching session. Investigators continually prompted the subjects through the exercise, but were unable to stimulate free-thinking, consistent, and self-motivated think-alouds. One potential explanation originates from the observation that our study population was not uniformly familiar with the Internet. Therefore, some subjects may have felt overly challenged by simultaneously learning how to use the Internet and verbalizing their navigational strategies. According to previous studies [31], these subjects were probably in an "acquisition role." Such studies disclosed that a learner who is new to a certain task focuses primarily on acclimatization, and finds it overwhelming to concurrently think aloud. Since traditional think-aloud protocols may be ineffective for this group, an interactive protocol may be of assistance for future studies. In such a protocol, subjects would directly be asked about specific site features, and asked to rate and make comparisons between health sites. This may highlight precise preferences the subjects might have for Web-site information, content, design, and presentation, and may result in a more cohesive rating system.
Overall, however, our subjects were very enthusiastic about learning how to use the Internet, and all indicated an interest in improving their skills for future use. In this study and other studies [13,15], members of the low-literacy population have expressed excitement about using the Internet. In order for the Internet to further empower these individuals to make informed health decisions, the development of easy to read and easy to comprehend health materials is imperative. If Google's sponsored sites are usedas a guide, low-literacy adults prefer information that is aesthetically pleasing, has minimal text, and is organized by subject matter. Search engines that are able to consolidate these features for searches will probably be of greater use to this population. However, low-literacy adults must improve their navigation and searching skills to efficiently locate low-literacy materials on the Internet. With sufficient practice, they are likely to develop the skills to use the Internet to find specific health information, and learn to critically evaluate the information they access.
Indications for Future Research
One caveat to the present study is that our sample size precluded the analysis of factors besides low literacy that could influence the results we observed. We believe, however, that our findings with this sample group in an observational study were representative of the way low-literacy adults interact with the Internet. It will be important to validate and analyze in a larger study the appeal of sponsored sites (as opposed to other retrieved links) to low-literacy adults. It will also be worthwhile to determine the relative importance of limited literacy in comparison to socioeconomic and cultural factors in effective use of the Internet by this population. Future work will identify the exact components of sites that engage and promote learning by low-literacy adults. Greater understanding of these factors will hasten the day when the Internet becomes an effective vehicle for optimizing the health knowledge and acumen for those at high risk of poor health outcomes.

internet
literacy
health
reading
health education
health promotion
socioeconomic factors


Drilling k-wires, what about the osteocytes? An experimental study in rabbits

Introduction The function of osteocytes regarding osteonecrosis has been underestimated for a long time. Recently it has been suggested that apoptosis of osteocytes results in strong osteoclastic bone resorption. Death of osteocytes due to drilling may therefore increase the risk of K-wire loosening. The purposes of our in vivo study were to assess the minimal drill time needed to notice disappearance of osteocytes and to measure the distance of the empty osteocyte lacunae surrounding the drill tract in relation with the insertion time, directly and 4 weeks after drilling Kirschner (K-) wires into the femur and tibia of rabbits.
Introduction
Experiments concerning thermal damage to bone tissue due to drilling Kirschner wires (K-wires) show several variables interfering with heat generation [7, 9–14, 32]. These variables can be categorized into three groups: drilling technique, K-wire characteristics and external factors. The drilling technique is a subtle balance between drilling speed, insertion time and pressure [1, 2, 5, 30, 31, 34]. The characteristics of K-wires differ in diameter and K-wire tip [17, 23, 29]. The main external factor is irrigation with a water spray during drilling [3, 20, 24, 36].
It is believed that critical temperature for bone injury is around 56°C because alkaline phosphatase denaturates at this temperature. Osteocytes, however, may even be more sensitive to heat [23, 24]. Eriksson [9, 10, 12] observed that a temperature of 47°C for only 1 min results in bone resorption. Bone is capable of remodeling by bone resorbing osteoclasts, bone forming osteoblasts and osteocytes [15, 19, 22, 26]. The latter differentiate out of osteoblasts which have ceased bone production and have become embedded in the bone matrix, in vacuoles cushioned by fluid and large molecules, forming a network [8, 15, 19, 22, 25]. Despite the fact that the osteocytes are the major constituents of bone, their role in bone resorption regulation has remained controversial for a long time [4, 16, 21, 22, 27]. In the past decade, however, understanding of osteocyte physiology has increased dramatically and it has become clear that osteocytes play an important role in bone remodeling [6, 15, 18, 25, 26, 35]. Now we know that micro damage to bone, e.g. by drilling, is associated with an increase in osteocyte death by apoptosis [25]. This process triggers local bone resorption resulting in K-wire loosening, because death of osteocytes turns off the inhibition of osteoclasts [6, 15, 16, 22, 25, 35].
The status of osteocytes after drilling into bone has been investigated before. Thompson [33] describes the absence of osteocytes as an acute cellular reaction, which increases in severity with increase of drilling speed. Pallan et al. [28] continued Thompson’s [33] work and describes the delayed cellular changes in bone after pin insertion which were left in situ for maximum 10 weeks. He also concluded that higher speeds produce relatively higher temperatures and increased tissue response after a long time period [28].
It is well known that in clinical daily practice K-wires are often drilled without proper cooling because most drilling devices do not have an incorporated cooling system and therefore cooling has to be done manually. In case percutaneous drilling is performed, the cooling effect on bone is minimal because of the surrounding soft tissues. An in vivo study was therefore designed which simulated daily practice concerning K-wire drilling to analyze the absence of osteocytes directly (t = 0) and 4 weeks (t = 4) after insertion. Our first aim was to measure the minimal drill time needed to notice disappearance of osteocytes. The second aim was to measure the distance of the disappeared osteocytes around the periphery of the drill holes in relation to drilling time.
Materials and methods
Animals and anesthesia
A total of 14 healthy, New Zealand white rabbits of female sex weighing a mean of 2.81 kg (2.66–3.09 kg) were used in this investigation. The rabbits were solely housed on a 12 h/12 h (light/dark) cycle and provided with standard diet food and water ad libitum. All animals were housed in the Central Animal Laboratory, Utrecht University, Utrecht, The Netherlands and received care in compliance with the European Convention Guidelines.
The animals were pre-anesthetized with a combination of methadone (10 mg/ml at a dose of 2.5–5.0 mg i.m.), ventraquil (10 mg/ml at a dose of 2.5–5.0 mg i.m.) and etomidaat (2 mg/ml at a dose of 2.0–8.0 mg i.v.).
After introduction of anesthesia the rabbits were cuffed and mechanically ventilated with O2:N2O, proportion 1:1, and 2% isoflurane. During the surgical procedure methadone (2.0–5.0 mg i.v.) was given. At the end of the operation nalbuphine (10 mg/ml at a dose of 1.0–2.0 mg/kg i.v.) was administered. After surgery the rabbits were housed at the intensive care for the rest of the day and night. At the end of the study the rabbits were euthanized by an i.v. overdose of pentobarbital.
Surgical technique
An operation device was created by the first author (Fig. 1). The operation device consists of a base plate. On this base plate, a dynamic plate was fixed which could be moved up or down. In front of the entire length of this dynamic plate a sideways moving slide was fixed on the base plate. On this sideways moving slide another back-forward slide including the drill was fixed. Forward movement of the drill was initiated using a 1.5 kg weight.
Fig. 1Operation device consisting of a base plate with a slide for sideways movement on top of this. On this slide another back-forward slide with a drill was fixed. The forward movement was initiated by a weight of 1.5 kg. Another dynamic plate was fixed on the base of the plate to move up and down. During surgery, the rabbit was fixed on this dynamic plate
During surgery the rabbit was fixed on the dynamic plate. This plate made it possible that the femur or tibia were on the same height as the K-wire. The sideways moving slide was responsible for the exact position of the K-wire in front of the femur or tibia.
After the rabbits were preanesthetized, X-rays were made to exclude deformities. Thereafter the animal’s hind limb was carefully shaved and prepared with a povidone-iodine solution. After this procedure, the hind limb was fixed on the testing machine. With the animal surgically draped, a straight-line skin incision was made on the lateral aspect of the femur extending from just below the anterior–inferior spine to the distal femur, followed by a straight-line skin incision on the lateral aspect of the tibia extending from just below the joint line proximally to about the joint line distally.
Dissection was carried out down to the periostium. Synthes Trocar tipped K-wires of 70 mm length and 0.6 mm thickness were drilled through the diaphysis. One K-wire was drilled into the femur and one into the tibia. Drilling was performed by a rotary engine fixed at 1,200 rpm. This is the maximum drilling speed used in our daily practice. Cooling was not performed. After insertion, the K-wires were cut short and the K-wire ends were bent to the cortex. After the wounds were closed in layers, X-rays were made to check the position of the K-wires and the condition of the bone. Insertion time could be measured very accurately by analyzing the operations recorded on video camera. All the experiments were performed by the same investigator.
Histological technique
After termination, the femur and tibia were removed from the hind limb and fixed in 4% formaldehyde solution. They were then decalcified, cut transversely next to the K-wire hole, after the K-wire was removed gently by a pair of tweezers, and embedded in paraffin according to standard procedures. Four micrometer thick serial sections were cut until the drill hole was visible, stained with hematoxylin and eosin and evaluated under a light microscope at 400× magnification for the presence or absence of osteocytes in the osteocyte lacunae surrounding the drill holes by a single investigator. The best section was used for evaluation. The distance over which the osteocytes had disappeared perpendicular to the drill holes was measured with an interactive morphometry device (Q-PRODIT, Leica, Cambridge, UK). In each section, four distances from the drill hole to the first osteocyte bearing lacuna were measured and averaged.
Statistics
Pearson’s Chi-square test was used to determine the drilling time needed for osteocytes to disappear. Pearson correlation was used to highlight any significant correlation between the drilling time and the distance of the disappeared osteocytes surrounding the drill holes. A P-value <0.05 was considered statistically significant. The data were analyzed using SPSS 12.0.1 for windows.
Results
After surgery (t = 0) six rabbits were terminated. Both hind limbs were used resulting in 24 assessments. From the remaining eight rabbits only one hind limb was operated. Four weeks later at termination this resulted in 16 assessments (t = 4). Two t = 0 and one t = 4 assessments were lost because no sections could be produced showing the drill hole, leaving 22 t = 0 and 15 t = 4 assessments.
Histological response to drilling was seen in most sections next to the drill hole (Fig. 2). At t = 0 and t = 4, all osteocyte lacunae next to the drill holes were empty in 11/22 (50.0%) and 13/15 (86.7%) of bones, respectively. At t = 4, a drilling time longer than 27 s resulted in a significant loss of osteocytes surrounding the drill holes (P = 0.008). At t = 0, a drilling time longer than 37 s resulted in a significant loss of osteocytes surrounding the drill holes (P = 0.011).
Fig. 2Status of osteocytes due to K-wire drilling at 1,200 rpm. Disappeared osteocytes due to drilling are marked by a dot. The osteocytes are encircled. The dotted line indicates the border between the present and disappeared osteocytes (hematoxylin and eosin)
A statistically significant positive correlation was seen between the distance of the empty osteocyte lacunae surrounding the drill hole in relation with drilling time, directly (P = 0.008, Fig. 3a) and 4 weeks after K-wire insertion (P < 0.000, Fig. 3b).
Fig. 3a Distance of empty osteocyte lacunae, in micrometers, surrounding the drill hole in correlation with drilling time, in seconds, at t = 0. b Distance of empty osteocyte lacunae, in micrometers, surrounding the drill hole in correlation with drilling time, in seconds, at t = 4
Discussion
The two most important findings of this experiment are that (1) osteocytes disappear especially beyond a drilling time of 27 s and (2) that there is a positive correlation between the distance of the empty osteocyte lacunae in relation with drilling time.
As far as we know there are no experiments studying the presence/absence of osteocytes while using drilling time as a variable. Therefore it is interesting to notice that our results, representing daily practice by using a drilling speed of 1,200 rpm, clearly indicate that osteocytes disappear after a drilling time above 27 s in this animal model, when no cooling is used. Pallan [28] and Thompson[33] however, noticed absence of osteocytes already after a drilling time varying from 5 to 12 s. The limitation of their experiments is that the insertion force was not standardized. That could be a possible factor explaining the difference in insertion time with matching histological changes.
The effect on osteocytes in our study was more pronounced 4 weeks after insertion compared to the effect on osteocytes directly after surgery. This confirms the results from Thompson [33] where the effect on osteocytes was more pronounced 72 h after the operation than at either 24 or 48 h. Apparently, not all damage to osteocytes is acute and microscopically visible, directly after K-wire insertion. This can be explained by the study of Eriksson et al. [13]. They compared histology and histochemistry for detection of bone viability directly after surgery. The histological sections revealed a 200 μm wide zone of empty osteocyte lacunae around the periphery of the drill hole while histochemistry of the same bone specimens showed a zone of 500 μm lacking diaphorase enzyme activity. This indicates that the empty osteocyte lacunae directly after surgery underestimates the extent of the drilling trauma and becomes clear as time passes. Neovascularisation is probably a reason for the increase of osteocytes disappearance in time. During heating, due to drilling, blood flow will stop in minor vessels preventing the clearance of the osteocyte lacunae [10, 13]. After neovascularisation the osteocyte lacunae can be cleared finally.
Our study also showed an interesting positive correlation between the distance of the empty osteocyte lacunae in relation with time. The zones of disappeared osteocytes varied from 106 to 1,285 μm and the drilling times from 41 to 262 s. A correlation between drill time and distance was not shown before. What we do know is that Eriksson et al. showed a 200 μm wide zone of empty osteocyte lacunae around the periphery of the hole after drilling into femurs of New Zealand white rabbits while conventional irrigation was administered[13]. These results are difficult to compare because Eriksson et al. did not measure time, irrigated with saline, did not standardize the insertion force and drilled with a running speed of 20,000 rpm. Furthermore, Pallan [28] showed that the histological changes, including absence of osteocytes, were never apparent more than 250 to 500 μm from the pins [28]. Like Eriksson they did not standardize insertion force and drilling time varied from 5 to 12 s.
No osteoclastic activity was noticed in the already existing cortex. This was expected as Pallan [28] hardly noticed osteoclastic activity after 6 weeks, and only slight osteoclastic activity after 8 and 10 weeks and our experiments covered a time span of only 4 weeks.
We are convinced that delayed tissue response corresponds with late K-wire loosening seen in daily practice. Although we did not compare drilling, with and without cooling, this study demonstrates the need for a short drill time, less than 27 s to prevent the disappearance of osteocytes and to limit the bone resorption cascade.

drilling
insertion time
kirschner wire
animal
histology


The inflammatory effects of UDP-glucose in N9 microglia are not mediated by P2Y14 receptor activation

In this study we evaluated the functionality and inflammatory effects of P2Y14 receptors in murine N9 microglia. The selective P2Y14 receptor agonist UDP-glucose (UDPG) derived from microbial sources dose dependently stimulated expression of cyclooxygenase-2 and inducible nitric oxide synthase, and potentiated the effects of bacterial lipopolysaccharide on nitric oxide production. However, another selective P2Y14 receptor agonist, UDP-galactose, did not affect these endpoints either alone or in combination with lipopolysaccharide. Interestingly, synthetic UDPG also had no detectable pro-inflammatory effects, although P2Y14 receptors are both expressed and functional in N9 microglia. While synthetic UDPG decreased levels of phosphorylated cyclic AMP response element binding protein, an effect that was blocked by pertussis toxin, the pro-inflammatory effects of microbial-derived UDPG were insensitive to pertussis toxin. These data suggest that the pro-inflammatory effects of microbial-derived UDPG are independent of P2Y14 receptors and imply that microbial-derived contaminants in the UDPG preparation may be involved in the observed inflammatory effects.

cyclic amp response element binding protein (creb)