bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification Tree Prediction Models for Dental Caries from Clinical, Microbiological, and Interview Data
Authors: Stewart P.W. , Stamm J.W.
Published: November 2010

Caries prediction by Classification And Regression Tree (CART) analysis is an appropriate and powerful alternative or complement to the commonly used classification methods of logistic regression and discriminant analysis, both parametric and nonparametric. The binary classification tree method discussed in this article is designed for complex data and does not require assumptions about the predictor variables or about the presence or absence of interactions among the predictor variables. Furthermore, the results give insight into the structures and interactions in the data and are easy to interpret and apply. In preliminary applications of the CART algorithms to data from The University of North Carolina Caries Risk Assessment Study, the method produced prediction rules having sensitivities and specificities that were similar to or slightly better than those associated with logistic and discriminant analyses. The classification trees constructed tended to involve far fewer predictor variables than required for adequate logistic and discriminant models. For example, for first-grade children in Aiken, South Carolina, nine variables were used to define a prediction rule having 64% sensitivity and 86% specificity. Ten-fold cross-validation estimates for future data were 58% and 79%, respectively. For first-grade children in Portland, Maine, two variables were used to define a prediction rule having 62% sensitivity and 77% specificity. The cross-validation estimates for future data were 58% and 78%, respectively. A brief, and previously unavailable, explanation of the CART method is given for the special case of a dichotomous outcome variable.
Age-related Changes in Mucins from Human Whole Saliva
Authors: Denny P.C. , Denny P.A. , Klauser D.K. , Hong S.H. , Navazesh M. , Tabak L.A.
Published: November 2010

The predominant mucins in human whole saliva, MG1 and MG2, serve to protect and to lubricate the oral cavity. In this study, both unstimulated and stimulated whole salivas were collected from two groups of subjects: young (18-35 years of age) and aged (65-83 years of age). The subjects were in apparent good health. Saliva samples from each subject were analyzed by SDS-PAGE. The gels were stained with Stains-all, and both MG1 and MG2 were quantitated by video-image densitometry. The protocol gave reproducible values for each mucin. The stimulated and unstimulated salivas from aged subjects showed significant reductions in concentrations of both MG1 and MG2, as quantitated in mucin dye-binding units. Possible associations of these reductions with the aging process are discussed.
Characteristics of Masticatory Mandibular Movements and Velocity in Growing Individuals and Young Adults
Authors: Kiliaridis S. , Karlsson S. , Kjellberg H.
Published: November 2010

Studies of the development of mastication in the normal growing individual have received little attention in the literature. The aim of this study was to determine whether changes in oral motor function occurred during growth. Ninety healthy individuals with normal occlusion were divided into six groups of males and females, 9-10, 13-15, and 20-22 years of age. Oral motor function, with respect to mandibular displacement and velocity, was monitored with an opto-electronic method. The results revealed that the total duration of the masticatory cycle was not influenced by age or gender. However, the time distribution between the different phases was found to be influenced by the age factor, causing a longer opening time and a shorter closing time in the adults. In mastication, both mandibular displacement and the mandibular velocity in closing were less in females. A reduction of the masticatory opening velocity and an increase in closing velocity were observed with increasing age. Physiological maturation of the masticatory system due to central and peripheral changes and functional adjustments due to changes in dentition and skeletal growth may be the underlying reasons for our findings.
A Quantitative Analysis of Mineral Loss and Shrinkage of in vitro Demineralized Human Root Surfaces
Authors: Ten Cate J.M. , Nyvad B. , Van De Plassche-Simons Y.M. , Fejerskov O.
Published: November 2010

Demineralization of dentin specimens proceeds at a faster rate than that of enamel. Although this is generally accepted, a quantification of the rate of formation of root lesions is hampered by the shrinkage of the lesions when these are dried prior to microradiographic analysis.' This leads to a significant underestimation of the lesion depth and total mineral loss. The aim of this paper was to quantitate the rate of mineral loss during root lesion formation in vitro and to determine the shrinkage of root specimens as a result of drying. Unerupted roots of human teeth were subjected to a demineralizing system of 0.1 mol/L lactate buffer (pH = 4.8) with 0.2 mmol/L methanehydroxydiphosphonate during four, 11, 22, and 44 days. The root lesions were assessed by quantitative microradiography. The demineralizing solutions were analyzed to determine the amounts of root tissue dissolved. A comparison of these two sets of data showed that, with the demineralizing system used, root lesions may shrink up to 62%. Fixation of the specimens in fixative did not affect this shrinkage. Chemical analysis showed that mineral loss proceeded linearly with time. From the data-sets of this study, a model was developed to compensate for the shrinkage in the dentin specimens. In this way, it was possible to calculate the lesion depth at four demineralization times as being 130, 220, 320, and 530 μm, respectively. These values were in agreement with a microscopic determination of the lesion depth.
Reliability of Pulpal Blood-flow Measurements Utilizing Laser Doppler Flowmetry
Authors: Ramsay D.S. , Artun J. , Martinen S.S.
Published: November 2010

Pulpal blood flow can now be measured non-invasively in the clinic utilizing laser Doppler flowmetry. The purpose of our study was to test (1) whether the position of the measurement probe on the tooth affects blood-flow measurements and (2) whether measurements from identical locations vary over time. Blood flow of one maxillary central incisor was measured in each of 13 volunteers. Measurements were recorded at five different locations on the labial surface of each tooth. Four measurement sessions were performed, and two sets of measurements were recorded at each session. Custom-made splints ensured accurate and reproducible positioning of the measurement probe at each session. Spatial position of the probe had a clear effect on the pulpal blood-flow measurements (p < 0.0001). Measurements made at incisal and gingival locations were less and greater (p < 0.05), respectively, than those made at central locations. Measurements from various mesio-distal locations did not differ (p > 0.05) when made at the same height on the tooth. Pulpal blood-flow measurements recorded at a given site were not consistent across all of the testing sessions (p < 0.0001). Our data suggest that reliable interpretation of longitudinal measurements of pulpal blood flow obtained with laser Doppler flowmetry requires accurate repositioning of the measurement probe. In addition, an adequate control condition should be included to account for bias due to temporal variation.
Reproducibility and Sensitivity of Oral Malodor Measurements with a Portable Sulphide Monitor
Authors: Rosenberg M. , Kulkarni G.V. , Bosy A. , McCulloch C.A.G.
Published: November 2010

Forty-one subjects with bad breath were assessed for oral malodor and periodontal status on three occasions, at intervals of approximately one week. Oral malodor was assessed by measurement of peak and steady-state volatile sulphide levels with a portable sulphide monitor and by organoleptic measurement of whole-mouth, tongue dorsum, and interproximal dental odors by two independent judges. Reproducibility of measurements, assessed by paired t tests and Kappa testing, demonstrated no significant differences between any ofthe test results from the first and second appointments. Steady-state sulphide levels were the most reproducible of all tests. The ability of the tests to detect an expected reduction of malodor following a 0.2% chlorhexidine mouthrinse regimen was investigated by comparison of test values between the second and third appointments. Following the mouthrinsing treatment, 43% reductions of peak, 47% reductions of steady-state volatile sulphide levels, and 15-58% reductions in all other measurement categories were observed. The majority of the participants (22/41) had no pockets greater than 5 mm and exhibited both moderate gingival inflammation (Mean Gingival Index = 1.17) and moderate plaque accumulation (Mean Plaque Index = 1.84). Plaque Index and presence of pockets greater than 7 mm were weakly related to sulphide measurements. Whereas assessment of steady-state sulphide levels by the sulphide monitor does not constitute a direct measure of oral malodor, its relation to organoleptic measurement, superior reproducibility, objectivity, and sensitivity support the use of the sulphide monitor in clinical studies.
Remineralization and Demineralization in situ from a Triclosan/Co-polymer/Fluoride Dentifrice
Authors: Mellberg J.R. , Blake-Haskins J. , Petrou I.D. , Grote N.E.
Published: November 2010

An in situ study was conducted to evaluate the effect of a dentifrice containing 1100 ppm F (NaF) and triclosan, an anti-plaque agent, on remineralization of artificially-formed caries lesions in thin sections of human enamel. The thin sections were placed in mandibular partial dentures of 15 subjects and covered with a steel mesh to provide an area for plaque accumulation. The subjects brushed their teeth and dentures three times daily for two-week periods in a cross-over design, after which the specimens were removed and analyzed by quantitative microradiography for changes in mineral content. Results showed that lesions treated with the triclosan-fluoride product were remineralized 18.0 ± 23.4% compared with 19.0±32.3% from a 1100-ppm F (NaF) positive control. Use of a placebo dentifrice resulted in 71.9% demineralization. The findings showed that triclosan neither enhanced nor interfered with the promotion of remineralization by fluoride.
Permselectivity of Sound and Carious Human Dental Enamel as Measured by Membrane Potential
Authors: Carey C.M. , Vogel G.L. , Chow L.C.
Published: November 2010

A microwell technique was used for determination of the permselectivities of sound and carious enamel in the same slice of tooth. The permselectivity determination was accomplished by drilling microwells in the enamel and filling them with a simulated plaque fluid containing lactate, carbonate, and inorganic ions at concentrations similar to those in resting plaque fluid, but with different concentrations of KCI. The electrical potentials developed across the enamel membrane were measured with microreference electrodes placed in the wells or in the solution outside the tooth. The results showed that the membrane potential was a function of the composition of the solutions separated by the enamel membrane and was independent of the composition of the solutions in the adjacent wells. The enamel was found to be cation-permselective, and sound enamel was more permselective than carious enamel. The flux rate of K+ was estimated from the change in the K+ concentration of the well solution as a function of time. The flux rate and the membrane potential data were used in the Nernst-Planck Flux Equation for calculation of the diffusion coefficient of K+ through enamel. The results indicate that the permselectivity of enamel can greatly influence the diffusion of ions through enamel membranes.
The Areas of Various Surfaces in the Human Mouth from Nine Years to Adulthood
Authors: Kerr W.J.S. , Kelly J. , Geddes D.A.M.
Published: November 2010

Surface area measurements of five regions of the oral cavity were made from study casts of 57 subjects with an age range from 9.3 to 19 years. While the longitudinal pattern of growth exhibited by the total of the five areas, when subgroups were compared, was characterized by a steady increase to around puberty (13 years), followed by a plateau, different areas showed different patterns of growth. Increase in the surface area of the teeth was associated with the eruption of the second and third molars, whereas the area of the buccal lingual mucosa continued to increase into adult life. The palate, buccal vestibular mucosa, and dorsum of the tongue demonstrated a typically skeletal pattern of growth, i.e., increase until puberty with a rapid cessation thereafter.

The results of this study indicate the need for longitudinal data to further knowledge concerning growth of the oral cavity.
The Effect of Sucrose on Plaque pH in the Primary and Permanent Dentition of Caries-inactive and -active Kenyan Children
Authors: Fejerskov O. , Scheie A.AA. , Manji F.
Published: November 2010

The hypothesis that the Stephan pH responses of dental plaque would be different in caries-active and -inactive individuals was tested in 20 seven-year-old and 19 14-year-old Kenyan children. In each age group, half the children had ≥ 2 dentin cavities; the other half had no such lesions. With a palladium-touch microelectrode, interdental plaque pH was monitored between m1/m2 in each quadrant in the primary dentition and in the four molar/premolar regions in the permanent dentition. pH was also monitored in caries cavities in the occlusal surfaces of lower first molars and on the tongue. pH was measured before and up to 60 min after the children rinsed with 10 mL of 10% sucrose. Caries status of the individual was unrelated to plaque pH in comparable non-carious sites in both of the age groups. The pH minimum in the maxilla was about 0.5 pH units lower than that in the mandible. Active occlusal caries lesions had a resting pH value of about 5.5, about 1 pH unit lower than that of sound surfaces. The pH dropped to about 4.5 in caries lesions and recovered slowly. In sound occlusal sites, a pH drop to about 6.0 was followed by a relatively rapid return to the resting value. Thus, when the mean values were considered, the classic Stephan curve response was evident. However, when the pH changes at single sites were considered at various time intervals, a substantial, erratic fluctuation was observed. The tongue had a resting pH value of 7.0, which dropped to about pH 5.5 and remained low for more than 60 min.
Electromyographic Heterogeneity in the Human Masseter Muscle
Authors: Blanksma N.G. , Van Eijden T.M.G.J. , Weijs W.A.
Published: November 2010

The complex, pennate architecture of the human masseter muscle points to a functional division into more than the commonly distinguished deep and superficial parts. In this study, the possible existence of regional differences in activation was examined. EMG activity was registered in three deep and three superficial regions with the use of bipolar fine-wire electrodes. Recordings were made during different static bite tasks, in specified directions, and with a specified bite-force magnitude. A linear bite-force/EMG relationship was observed. Furthermore, it appeared that muscle regions showed a different pattern of change in activity as a function of bite-force direction. Heterogeneity was nearly absent in anteriorly-, anteriomedially-, and medially-directed bites, but became increasingly obvious in the other bite-force directions. The posterior deep region showed the most aberrant activation pattern, which was almost opposite that from the other regions. This part was fully active in posterolaterally-directed bites. The posterior superficial region showed the largest variability in activity as a function of bite-force direction. The results point to a functional partition of the masseter muscle in at least three parts: anterior deep, posterior deep, and superficial. A further subdivision of the superficial portion might be present, but was not as obvious as the division of the deep masseter.
A Statistical Approach to the Ecology of Porphyromonas gingivalis
Authors: Loos B.G. , Van Winkelhoff A.J. , Dunford R.G. , Genco R.J. , De Graaff J. , Dickinson D.P. , Dyer D.W.
Published: November 2010

Previous studies have suggested that infections with Porphyromonas gingivalis, associated with periodontal disease, may consist of one clonal type. It has also been shown that each individual patient carries a unique clonal type of P. gingivalis, as assessed by DNA fingerprinting. This issue was further examined by random collection of multiple isolates ofP. gingivalis from multiple sites in several patients, and characterization of these isolates by DNA fingerprinting. Although most patients appeared to be infected exclusively by one clonal type of P. gingivalis, at least one patient was found to harbor two distinct clonal types. This indicates that the simultaneous presence of different clonal types of P. gingivalis can occur. A statistical method was developed for retrospective analysis of these data for estimation of whether the remainder of these patients were actually infected with single or multiple clonal types ofP. gingivalis. With this statistical method, a confidence interval was calculated for estimation of the true proportion of a single observed clonal type in the potential population of P. gingivalis that might be recovered from an infected patient. Statistically, the sampling of small numbers of sites per patient or isolates per site leads to a wide confidence interval for the estimated true proportion of the observed clonal type in the infecting P. gingivalis population. For example, when five sites in an oral cavity yield indistinguishable P. gingivalis isolates, then the true proportion of this clonal type in the total P. gingivalis population in the infected oral cavity is estimated to be in the interval between 55% and 100% (at a 95% confidence level). If the isolates from all sampled sites from a periodontal patient appear to be of the same clonal type, it can be calculated that at least 29 different sites must be sampled for this observed clonal type to represent at least 90% of the P. gingivalis population in this patient (95% confidence level); this was termed the LTP, or lowest true proportion. Such calculations can also be used for estimation of the LTP of a clonal type infecting a single oral site in a periodontal patient. These results confirm the commonly held opinion that studies investigating the ecology of P. gingivalis and other suspected pathogens must be designed on a large scale in order for statistically meaningful results to be obtained.
Comminution of Food by Complete-denture Wearers
Authors: Slagter A.P. , Olthoff L.W. , Steen W.H.A. , Bosman F.
Published: November 2010

A method for quantifying the comminution of an artificial test food (Optosil®) was evaluated with respect to its suitability for measurements of masticatory performance in complete-denture wearers. Reference was made to subjects with natural dentitions. The description of particle size distributions generated by complete-denture wearers by a Rosin-Rammler equation was subject to limitations, due to the presence of large proportions of almost-intact particles, which had hardly been damaged or broken during chewing. This finding might be explained by: (i) the relatively high fracture strength of Optosil® as compared with natural foods; and (ii) the limitations of complete-denture wearers in exerting bite forces. The particle size distributions obtained after repeated measurements and described by linear interpolation of data points were reproducible. In comparison with young adults with natural dentitions, the denture-wearers needed approximately seven times more chewing strokes to achieve an equivalent reduction in particle size.
A Longitudinal Radiographic Study of the Periosteal Migration along the Growing Rabbit Mandible
Authors: Frankenhuis-Van Den Heuvel T.H.M. , Maltha J.C. , Kuijpers-Jagtman A.M. , Van't hof M.A.
Published: November 2010

In the present study, the role of the periosteum in mandibular growth was investigated. The orientation of the superficial bony spicules of rabbit mandibles was determined on dry skulls after perfusion of the animals with an India ink solution. The spicular orientation in the ramus area appeared to be toward the condyle, rostrally toward the incisors, and caudally toward the angular region. The behavior, during growth, of the periosteum in the caudal mandibular half was studied by implantation of metal periosteal and bone markers. A series of cephalograms revealed the migration pattern of the periosteal markers, and by that the migration pattern of the periosteum.

It can be concluded that both the pattern of the superficial bony spicules and the periosteal migration pattern suggest a possible influence of the periosteum on mandibular growth.
Acute and Chronic Fluoride Toxicity
Authors: Whitford G.M.
Published: November 2010

Compared with the latter half of the 19th century and the first half of the 20th century, the frequency of fatalities stemming from the ingestion of fluoride compounds has declined dramatically. Since 1978, there have been four fatalities caused by the ingestion of fluoride, all in dental products. The numbers of exposures to fluoride doses that cause concern, however, has increased, as judged by the annual reports of the American Association of Poison Control Centers. The number of reports made to poison control centers has increased from approximately 7700 in 1984 to 10,700 in 1989. Over 3700 persons have been treated in health care facilities for exposure to fluoride during this period, and there have been 133 cases for which the medical outcomes were classified as moderate or major. The sources of fluoride have been limited almost exclusively to fluoride-containing vitamins and dental products. Based on a review of the doses involved in the four fatalities, three of which involved young children, the "probably toxic dose" of fluoride has been set at 5 mg F/kg body weight. For children who are 6 years of age or less, the PTD can be found in single containers of several kinds of dental products. Recommendations that should reduce the frequency of over-exposures to fluoride are described.

Regarding adverse effects due to the chronic intake of fluoride (excluding dental fluorosis), there is no evidence for risk in the US up to the level of intake that is associated with drinking water containing 4 ppm. This statement is based on 1990 or 1991 reports by the NY State Department of Health, the USPHS, and the National Cancer Institute. Two new reports, however, have implicated chronic fluoride intake at relatively low levels in a higher incidence of bone fractures. This relationship requires further study.
Alterations in Rat Condylar Cartilage Following Discectomy
Authors: Hinton R.J.
Published: November 2010

The purpose of this study was to examine the effect of unilateral extirpation of the articular disc of the temporomandibular joint on selected metabolic and compositional characteristics of the condylar cartilage. Unilateral discectomy was performed in one group of growing (28-day-old) rats, while another group received only unilateral arthrotomy. The effect of the discectomy procedure was assessed by comparison of ratios of the operated to unoperated sides in the discectomy and arthrotomy groups. Total uronic acid content (μg/mg dry tissue wt) of the condylar cartilage and [35S]-sulfate incorporation (dpm/μg uronic acid) into the condylar cartilage were decreased in discectomy-group animals at nine, 16, and 28 days following surgery, while hydration of the cartilage was increased in discectomy animals at both 16 and 28 days post-surgery. Wet and dry tissue weights of the cartilage were dramatically increased in discectomy-group animals at all post-operative intervals. These metabolic and compositional changes were accompanied by pronounced structural alterations in the cartilage, including chondrocyte clustering and tears parallel to the articular surface. With the exception of [35S]-sulfate incorporation, the changes demonstrated in the condylar cartilage following discectomy were similar to early osteoarthritic alterations reported in limb articular cartilage following partial meniscectomy or cruciate ligament resection.
ESCA Study on Dental Alloy Surfaces Modified by Ga-Sn Alloy
Authors: Ohno H. , Araki Y. , Endo K.
Published: November 2010

A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/ MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect.

A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga 2O3 and SnO2, less than 1-2 nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.
Initial Dissolution Rate Studies on Dental Enamel after CO2 Laser Irradiation
Authors: Fox J.L. , Yu D. , Otsuka M. , Higuchi W.I. , Wong J. , Powell G.L.
Published: November 2010

The influence of CO 2 laser irradiation on the dissolution behavior of human dental enamel has been investigated. Human enamel was irradiated by a continuous-wave CO 2 laser at 10.6 μm and initial dissolution rates (IDRs) were measured in 0.1 mol/L acetate buffer, pH = 4.5, both with and without calcium and/or phosphate common ion, by means of a rotating disk assembly. The effects of (1-hydroxyethylidene) bisphosphonic acid (EHDP), fluoride (F), and dodecylamine HCI (DAC) at various levels upon the IDR were also determined. All of the findings were consistent with the hypothesis that CO2 laser irradiation converts dental enamel to hydroxyapatite (HAP) possessing site #2 character (Yamamoto et al., 1986). The dissolution driving force function, KHAP = aca10apO46aOH2, was found to have a value of 10-129.9 after being lased, as compared with 10-121.4 before being lased. The IDR values for EHDP (3 mmol/L) and DAC (3 mmol/L) were essentially zero as expected for site #2 HAP. For solution F, the deduced dissolution driving force function, K FAP = aca10aPO46aF2 was 10-128.6 after being lased as compared with 10-116.3 before being lased. These results all support the hypotheses (1) that laser irradiation may convert the surface of human dental enamel to an apatite of significantly lower effective solubility (i.e., site #2 HAP) than that of unlased enamel; and (2) that there is significant synergism between laser treatment and these chemical dissolution rate inhibitors (again consistent with site #2 HAP).

Simple model calculations indicate that, in both the presence and absence of fluoride, these laser-induced changes in the driving force for dissolution should dramatically lessen the susceptibility of enamel to the types of acid challenge that might be encountered in the mouth
Examination by X-ray Photoelectron Spectroscopy of the Adsorption of Chlorhexidine on Hydroxyapatite
Authors: Sodhi R.N.S. , Grad H.A. , Smith D.C.
Published: November 2010

X-ray photoelectron spectroscopy (XPS) was used for determination of the effects of chlorhexidine (CHX) solutions (0.2% and 1% solutions of the digluconate salt) on the elemental composition of hydroxyapatite surfaces. So that the nature of the adsorbed species after they were washed with water could be identified, comparisons were made with reference spectra for CHX obtained from a CHX digluconate film and CHX dichloride powder. The XPS results clearly indicated the retention of CHX moieties, which could be ascertained from the spectra by the presence of N and Cl, features unique to CHX. The spectral envelopes were virtually identical to those obtained from the reference spectra. High-resolution C Is spectra also gave support for the retention of CHX; however, the spectra differed from those of the CHX digluconate film in that no feature attributable to the C-OH of the gluconate anion was present, consistent with the view that the CHX cation remains behind to form an electrostatic bond with the phosphate groups of the hydroxyapatite. The N:Cl ratio for the washed samples was found to be higher than that for the reference samples and may be indicative of partial decomposition of the CHX. Decomposition was also seen to be induced by x-ray exposure. While the high-resolution spectra presented here do not directly address the controversy on the mechanism for the anti-plaque efficacy of CHX, they do provide the necessary basis for the application ofXPS to future in vitro studies on the retention of CHX to dental surfaces.
Fluoride Retention in Dentin after Topical Application of Aminefluoride
Authors: Hellwig E.
Published: November 2010

The retention of KOH-soluble and structurally bound fluoride in dentin after topical application of aminefluoride was investigated. One cylindrical dentin sample was prepared from each of 40 extracted third molars. All samples received one topical application of 1 μL of aminefluoride solution (1.23% F) for three min. Ten of them were analyzed immediately after fluoridation. The remaining 30 samples were mounted in the buccal aspects of a special mouth appliance which was carried by a person for five days. After one, three, and five days, 10 of the 30 samples were removed from the appliance. In all samples, the amount of structurally bound fluoride was determined in three layers (20 μm, 20 um, 20 μm) by use of a special grinding technique. Before each grinding step, the dentin specimens were analyzed for KOH-soluble fluoride. The total amount of KOH-soluble fluoride in dentin was 48.7 ± 14 μg/cm2. It decreased drastically during the experimental period. Structurally-bound fluoride increased one day after fluoridation in the first and second layers. Thus, topical application of aminefluoride resulted in a significant accumulation of KOH-soluble fluoride in dentin. This precipitate was unstable, but fluoride ions released from it could perhaps increase the amount of structurally bound fluoride.
Effects of Chlorhexidine-containing Gel and Varnish on Abutment Teeth in Patients with Overdentures
Authors: Keltjens H.M.A.M. , Creugers T.J. , Schaeken M.J.M. , Van Der Hoeven J.S.
Published: November 2010

Previous experiments have shown that daily use of 1% chlorhexidine gel strongly reduced caries development in the abutment teeth under overdentures. The present experiment was designed to determine whether intermittent application of chlorhexidine, either in a varnish or in a gel, might be used as an alternative preventive method, less demanding for the patient. To this end, 31 patients were distributed among four treatment groups, with the number of mutans streptococci in plaque and saliva used as a balancing criterion. The treatments consisted of a single application of 40% chlorhexidine varnish, daily application of 1% chlorhexidine gel for one week, or the corresponding placebo treatments with varnish or gel without chlorhexidine. Patients were re-called for bacteriological and clinical examination at various intervals during an eight-week period following treatment.

Chlorhexidine varnish and chlorhexidine gel applications significantly suppressed mutans streptococci on the abutment teeth for four and eight weeks, respectively. In agreement with earlier findings, the numbers of Actinomyces viscosus/naeslundii in plaque were significantly increased after chlorhexidine varnish treatment. The chlorhexidine gel reduced plaque accumulation and gingival bleeding for one week but had no long-lasting effect.

The results seem to justify a long-term clinical test of intermittent chlorhexidine applications as an alternative for daily use in patients with overdentures.
Influence of Tempering Method on Residual Stress in Dental Porcelain
Authors: Asaoka K. , Kuwayama N. , Tesk J.A.
Published: November 2010

The porcelain component of a porcelain-fused-to-metal restoration is strengthened by residual (tempering) stresses which are induced by cooling procedures followed in dental laboratories. The thermophysical properties of materials and cooling rate are the main factors which determine the residual stress. In this paper, the temperatures in the midplane of body-porcelain disks were measured from a heat-soak temperature (1000°C) to room temperature during two different cooling procedures: slow cooling in air and forced-air cooling. Experimental results approximated exponential cooling wherein the cooling rates could be represented by a linear equation of temperature. Residual stresses, as affected by the tempering method and thickness of a porcelain disk, were calculated by computer simulation for regions away from the edges. The following temperature-dependent factors were incorporated into the simulation: elastic modulus, viscosity, and coefficient of thermal expansion. The cooling rate dependencies of the glass transition temperature and the temperature distribution during cooling were also included. The cooling rates used in this simulation were derived from the tempering data. The agreement between development of transient and residual stresses—calculated by computer simulation for various cooling methods, and the tendency toward failures of porcelain disks subjected to the tempering processes-was examined. Simulated residual stresses were also in good agreement with those measured by the indentation fracture method of Marshall and Lawn (1977) and Anusavice et al. (1989).
Evaluation of Subsurface Defects Created During the Finishing of Composites
Authors: Ferracane J.L. , Condon J.R. , Mitchem J.C.
Published: November 2010

The objective ofthis study was to test the hypothesis that a degraded subsurface layer containing microcracks is produced in dental composites as a result of finishing procedures. Various composites in the form of rectangular bars were finished with a 12-fluted carbide bur or a fine diamond within minutes of light-curing, and were subsequently stained with silver nitrate. Microscopic evaluation revealed that significant penetration of stain occurred in the unfinished as well as in the finished surfaces. The extent of dye penetration that could be directly attributed to a damaged layer produced by the finishing procedure was less than 10 μm, being greatest for a microfill (Silux Plus) and a hybrid (P-50) composite. There was no difference between the effects of the finishing instruments. SEM analysis of the subsurface showed an absence of any cracks for the composites. However, occasional disruption of the interface between the pre-polymerized resin fillers and the matrix was apparent for the microfill material. The results showed that only a very limited subsurface damage may be created in certain composites during the initial contouring of a restoration.
Composition of Pooled Plaque Fluid from Caries-free and Caries-positive Individuals Following Sucrose Exposure
Authors: Margolis H.C. , Moreno E.C.
Published: November 2010

The composition of pooled plaque fluid from five population samples was determined before and at selected times (7, 15, 30, and 60 min) after a 10% sucrose rinse. Subjects were grouped according to caries status (caries-free, CF, DMFS = 0; caries-positive, CP, DMFS > 10). Samples were also studied from white-spot surfaces and from sound surfaces of the same mouths of two additional CP groups. Plaque fluid was isolated by centrifugation and analyzed for organic acids, inorganic ions (ion chromatography), and pH (microelectrodes). Prior to sucrose exposure, plaque fluids from the CF subgroups and from sound surfaces of the CP subjects had higher pH values than samples from CP subgroups and from white-spot surfaces, respectively ; the ionic compositions were otherwise similar. Starved plaque fluids were also found to be supersaturated with respect to enamel and to a significantly greater degree in the CF samples, suggesting that CF plaque fluid may have a greater remineralization potential than CP samples. Following sucrose exposure, a rapid decrease in plaque fluid pH was observed, which corresponded primarily to lactic acid production. For all times examined, mean pH and DS(En) values were lower and lactic acid concentrations were higher in the CP samples than in the CF samples; noted differences were statistically significant at 7 min for pH and DS(En), and at 7, 15, and 30 min for lactic acid. Lower values of DS(En) suggest that plaque fluid from CP subjects had a measurably greater cariogenic potential. Calcium concentrations also increased in plaque fluid, following sucrose exposure, and to similar levels in samples from CF and CP subjects, despite significantly lower acid production in the CF samples. These latter results appear to be associated with the further finding that whole plaque from the CF subgroups contained significantly more calcium than the samples from the CP subjects. The availability of mineral ions like calcium within plaque may, therefore, play an important role in controlling enamel demineralization.
Influence of Ketones on Selected Mechanical Properties of Resin Composites
Authors: Peutzfeldt A. , Asmussen E.
Published: November 2010

The present study investigated a concept for additional crosslinking of dental polymers, by which resistance to wear of resin composites might be increased. Bifunctional ketones were added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to type and ratio of monomer and ketone. For measurement of possible effects of the cross-linking agents added, four mechanical properties of the experimental resin composites were determined. Addition of the bifunctional ketone diacetyl resulted in the following increases in mechanical properties: diametral tensile strength, 11%; flexural strength, 29%; modulus of elasticity, 19%; and modulus of resilience, 50%.
Change in Surface Hardness of BisGMA/TEGDMA Polymer due to Enzymatic Action
Authors: Larsen I.B. , Freund M. , Munksgaard E.C.
Published: November 2010

The surface microhardness of specimens made of a BisGMA/ TEGDMA polymer was measured before and during treatment for 60 days with phosphate buffer or phosphate-buffered esterase solution with an activity corresponding to the mean hydrolase activity of human saliva. The hardness of the buffer-treated specimens was unchanged during the incubation period, while that of the esterase-treated specimens decreased gradually. After about five days of treatment, no further change in hardness was observed for up to 60 days. Based on the difference in the calculated hardness of the specimens as a function of the applied load during measurement, it was estimated that the mean microhardness of the outermost surface layer of the esterase-treated specimens was diminished by about 15%, compared with that of the buffer-treated specimens. From these results, it was concluded that the wear resistance of a BisGMA/TEGDMA polymer is most likely diminished by hydrolases in saliva.
An Assessment of Survival Rates and Within-patient Clustering of Failures for Endosseous Oral Implants
Authors: Weyant R.J. , Burt B.A.
Published: November 2010

This study examined endosseous cylinder implant survival, defined as the unqualified presence of the implant in the mouth at the end of the observation period, in 598 consecutive VA patients, with a total of 2098 implants. Data were taken from the Department of Veterans Affairs (VA) Dental Implant Registry, which has maintained longitudinal data on the survival of individual dental implants in VA patients since 1987. The maximum time of observation in any one patient was 2040 days (5.6 yr). Survival analysis by use of life-table methods was carried out on both an implant- and a patient-specific basis. Implant cases were accrued randomly, and therefore a random censoring model was used. A correlated binomial model was used for assessment of the degree of within-patient clustering of implant removals. Results showed that the implant-specific survival rate during the longest time interval (5.6 yr) was 89.9%; the patient-specific implant survival rate during the same time was 78.2%. Among implants which were removed, the mean time to removal was 292 days. The hazard function, which describes the probability of implant loss as a function of time, decreased steadily throughout the observation period. The correlated binomial model suggested a clustering of removals within patients with multiple implants (p = 0.11, p = 0.0001). The odds of having a second implant removed were 1.3 times greater if the patient had already had one implant removed.

This study suggests that when implants fail, they do so soon after placement, and the likelihood of failure decreases steadily from implantation through the first five years post-surgery. These findings also suggest the existence of systemic factors which affect the survival of all implants within a given patient and may lead to multiple implant failures. Identification of these systemic factors may lead to improvements in patient selection and increases in the success rates for oral implants. Finally, results show that pure titanium implants had better short-term survival rates, but worse long-term survival rates, when compared with implants that had some other form of surface coating.
The Effects of Triclosan and Zinc Citrate, Alone and in Combination, on a Community of Oral Bacteria Grown in vitro
Authors: Bradshaw D.J. , Marsh P.D. , Watson G.K. , Cummins D.
Published: November 2010

A mixed-culture chemostat system has been used as a more stringent laboratory system for evaluation of the antimicrobial effects of Triclosan and zinc citrate. The inhibitors were added alone, and in combination, as a pulse (a high initial inhibitor concentration which decreased with time) or as a dose (concentration of inhibitor increased with time) to give maximum concentrations of 34.5 μmol/L Triclosan and 39.8 μmol/L zinc citrate. When dosed, Triclosan inhibited A. viscosus and all five Gram-negative species, whereas zinc citrate had less effect, probably due to complexation by media components. Similar effects were seen when Triclosan was pulsed, except that S. mutans was the most sensitive Gram-positive species and V. dispar was unaffected. However, when the inhibitors were dosed or pulsed in combination, marked complementary and additive inhibitory effects were observed, particularly against Gram-negative species, although S. gordonii and S. oralis were relatively unaffected. The data confirm that increased effects can be obtained with suitable combinations of antimicrobial agents and suggest that, under certain conditions, apparently broad-spectrum antimicrobial agents may be acting more selectively than hitherto suspected.
Relationships between the Temporomandibular Joint and the Middle Ear in Human Fetuses
Authors: Rodriguez Vazquez J.F. , Velasco Merida , Jimenez Collado J.
Published: November 2010

A study was conducted, on 30 human fetuses, of the structures passing through the tympanosquamosal fissure. The tympanosquamosal fissure lies between the middle ear and the temporomandibular region. Meckel's cartilage passes through the tympanosquamosal fissure and continues on into the middle ear with the cartilaginous anlage of the malleus. A tract of fibrous tissue arises from the mesenchyme, located cranial and lateral to Meckel's cartilage, that enters from the posterior area of the temporomandibular joint disc to the middle ear through the tympanosquamosal fissure, and attaches onto the area of continuity of Meckel's cartilage with the malleus. Transformation of Meckel's cartilage into the sphenomandibular ligament and anterior ligament of the malleus determines their continuity through the tympanosquamosal fissure. The posterior fibers of the temporomandibular joint disc giving rise to the discomalleolar ligament insert into the anterior ligament of the malleus.
Comparative SEM and TEM Examination of the Ultrastructure of the Resin-Dentin Interdiffusion Zone
Authors: Van Meerbeek B. , Dhem A. , Goret-Nicaise M. , Braem M. , Lambrechts P. , Vanherle G.
Published: November 2010

The resin-dentin interdiffusion zone produced by a dentin-adhesive system that removes the smear layer and concurrently decalcifies superficial dentin was morphologically examined by both scanning and transmission electron microscopy. Cross-sectioned resin-bonded dentin discs were etched with an argon-ion beam to make the resin-dentin interface observable by SEM. For the TEM examination, the sections were partly decalcified by an aqueous EDTA solution to facilitate ultramicrotomy and to disclose the ultrastructure of the interdiffusion zone. Both SEM and TEM confirmed the presence of the resin-dentin interdiffusion zone as the junction between the deep unaltered dentin structure and the restorative resin. Within the interdiffusion zone, three sublayers with characteristic ultrastructure and staining were identified by TEM. An upper diffuse black layer contained few structural features. Underneath, partially-altered collagen fibrils were closely packed, mostly running parallel with the interface and perpendicular to the dentinal tubules. Their outline was electron-dense, forming tunnel-like structures. At the base of the upper layer, several stained projections were found to bulge out into the underlying collagen network and appeared to be confined by obstructive, parallel-running collagen fibrils. Finally, the third dense layer, containing hydroxyapatite crystals, demarcated the superficially demineralized dentin layer from the deeper unaltered dentin. Resin diffusion into the decalcified dentin surface layer was evident, but diminished with depth, presumably reducing deeper resin impregnation into the interfibrillar spaces. The citric acid dentin-pretreatment probably caused denaturation of the superficial collagen fibrils. Its decalcifying effect gradually weakened with depth, leaving behind hydroxyapatite crystals at the base of the interdiffusion zone. These crystals appeared to have been resistant to the EDTA TEM-sample decalcification procedure, which suggests that they were protected by resin encapsulation.
Differences Two Years after Tooth Extraction in Mandibular Bone Reduction in Patients Treated with Immediate Overdentures or with Immediate Complete Dentures
Authors: Van Waas M.A.J. , Jonkman R.E.G. , Kalk W. , Van 't Hof M.A. , Plooij J. , Van Os J.H.
Published: November 2010

In a randomized controlled clinical trial, 74 patients who required immediate dentures were randomly treated with immediate overdentures on two lower canines or with immediate complete dentures. Mandibular bone reduction was measured by use of oblique lateral cephalometric radiographs made at baseline and the results compared with those of one year and two years after denture treatment.

Analysis of the data showed that the average bone reduction in the lower canine regions in the first year was 0.9 mm in the immediate-overdenture group and 1.8 mm in the immediate complete-denture group. In the posterior parts of the mandible, the bone reductions were, respectively, 0.7 mm and 1.9 mm. The differences were statistically significant in all measured regions. During the second year, no significant differences in bone reduction were found. The sums of differences in the first two years were significant in all regions except the molar region, preserving the initial difference.

Retention of roots of canines beneath a mandibular denture in immediate denture patients, even when they were in poor condition, reduced the collapse of the alveolar processes in all regions of the mandible.