bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Admixing Microfiller to Small-particle Composite Resin on Wear, Tensile Strength, Hardness, and Surface Roughness
Authors: Pallav P. , De Gee A.J. , Davidson C.L. , Erickson R.L. , Glasspoole E.A.
Published: November 2010

A series of photo-initiated composite resins, with a Bis-GMA-TEGDMA resin matrix, was investigated in vitro for occlusal wear, surface roughness, diametral tensile strength, and hardness. The materials contained mixtures of ground quartz (macro filler, 3 μm) and colloidal silica (micro filler, 0. 04μm), with total filler being constant at 68.5% by volume. The study was conducted to determine the influence of an increasing ratio of micro to macrofiller in the mixtures. When the macrofiller was gradually replaced by 3, 5, 7.5, 10, 15, and 20 vol% of microfiller, wear resistance increased substantially, ultimately to a constant level. Any influence on surface roughness or tensile strength and hardness could not be demonstrated.
Comparison of Fluoride Uptake Produced by Tray and Flossing Methods in vitro
Authors: Guo M.K. , Chow L.C. , Schreiber C.T. , Brown W.E.
Published: November 2010

The purposes of this study were to compare: (i) the fluoride (F) uptake by enamel in approximal areas of teeth when the F agent was applied in vitro via a tray or a flossing technique; and (ii) the effectiveness of two treatments -acidulated phosphate fluoride (APF) alone and CaHPO4 ·2H2O (DCPD)-forming pre-treatment followed by APF. Groups of three teeth (one premolar and two molars) were mounted in impression compounds simulating their oral configuration. In the tray group, teeth received one four-minute treatment by means of custom-formed trays. In the flossing group, the approximal areas of teeth were flossed for 40 sec twice daily for three days with an absorbent floss wetted with the treatment solution. All teeth were incubated in a saliva-like solution except during treatment. At the end of the three-day period, teeth were unmounted and washed in I mol/L KOH for 24 hours. The F uptake was calculated from biopsy data obtained before and after the treatment. The results showed that (i) DCPD-APF produced significantly greater F uptake than APF alone in both the tray and flossing methods, and (ii) the flossing technique produced significantly greater F uptake in the approximal areas than the tray method for either treatment.
The Effect of Daily Gum-chewing on Salivary Flow Rates in Man
Authors: Jenkins G.N. , Edgar W.M.
Published: November 2010

Following reports of increased salivary gland size and increased function, induced by increased mastication in animals, the effects of long-term, frequent gum-chewing on resting and stimulated flow rates were studied in human volunteers in separate experiments in Newcastle upon Tyne and in Toronto. In both experiments, unstimulated and stimulated saliva flow rates were measured in student volunteers at intervals of one or two weeks over a baseline period. Approximately half of the subjects were then given sugarless gum to be chewed (four pieces per day) over the experimental period; controls refrained from vigorous mastication. During (and, in Newcastle, after) the experimental period, salivary flow rates were measured at intervals, as before.

In Newcastle unstimulated, but not stimulated, flow rates increased in the gum-chewing group and were still elevated (compared with controls) eight weeks following the experiment. In Toronto, the mean results showed no effect of gum-chewing, but the seven gum-chewers among the 11 subjects with low baseline flow rates (< 0.3 mLlmin) showed a 43% rise in unstimulated flow rate (p ∼ 0.05).

The results suggest that increased mastication, in the form of gum-chewing, can increase unstimulated flow rates, especially in those with low salivary function. In addition to short-term beneficial effects of sugarless gum, these long-term effects indicate the possibility of a beneficial effect in caries prevention.
EMG Power Spectrum Patterns of Anterior Temporal and Masseter Muscles in Children and Adults
Authors: Yuen S.W.H. , Hwang J.C.C. , Poon P.W.F.
Published: November 2010

The power spectrum of electromyograms (EMG) has been demonstrated to vary with muscles having different muscle fiber type compositions. This study investigated the variations in EMG power spectrum patterns of the masticatory muscles with age and gender by comparison of the mean power frequency (MPF) of the anterior temporal and masseter muscles in children and adults. Surface EMG signals were sampled bilaterally from the muscles when the subjects were performing maximum voluntary isometric clenches at maximal intercuspal position. The results indicated that MPF values were age-dependent (p<0.001), and sexual dimorphism was evident (p<0.001), with lower MPF values in male and adult muscles. While male adults had the lowest and female children had the highest MPF values, female adults had MPF values closer to values obtained from male children. These differences or similarities could be attributed to the degree of differentiation of the muscles during growth and development of the craniofacial morphology.
Relationship Between Jaw Muscle Volume and Craniofacial Form
Authors: Gionhaku N. , Lowe A.A.
Published: November 2010

To study the relationship between craniofacial form and jaw muscle function, we evaluated 25 adult male subjects with Obstructive Sleep Apnea (age, 30-61 years; weight, 58-122 kg) on the basis of CT scans obtained for routine diagnostic purposes. All scans were obtained with the Frankfort horizontal plane at right angles to the floor; each CT slice was 8 mm thick. Masseter and medial pterygoid muscle outlines were traced, digitized, and stored, and three-dimensional reconstructions were made for calculation of muscle volume. Lateral cephalometric radiographs were analyzed for quantification of selected craniofacial variables. Significant correlations could not be identified between physiological apnea variables and jaw muscle volume. An intersubject variability in masseter muscle volume was identified (range, 22.4 - 38.1 cm3). Medial pterygoid muscle volume revealed more variability (range, 7.4 - 15.2 cm3). Masseter muscle volume had a negative correlation with mandibular plane and gonial angle, and a positive correlation with posterior face height, ramus height, posterior face length, condylar center to first molar point length, gonion to pterygomaxillary fissure length, and the ramus height/ anterior face height ratio. Medial pterygoid muscle volume showed a positive correlation with posterior face height, ramus height, posterior face length, and the lengths between condylar center to first molar contact point, gonion to pterygomaxillary fissure, and antegonion to key ridge. Subjects with large masseter and medial pterygoid muscle volumes had flat mandibular and occlusal planes, and small gonial angles.
Clinical vs. Arthrographic Diagnosis of TMJ Internal Derangement
Authors: Anderson G.C. , Schiffman E.L. , Schellhas K.P. , Fricton J.R.
Published: November 2010

Internal derangements of the temporomandibular joint (TMJ) have gained increased recognition as a potential source of pain and dysfunction of the masticatory system. The objective of this study was to evaluate the reliability of clinicians in predicting an arthrographic diagnosis of articular disc position in a typical patient population presenting for TMJ arthrographic evaluation. Two clinicians utilized a brief history, clinical examination (including evaluation of mandibular movement and TMJ auscultation), and tomographic TMJ imaging in evaluating 60 patients. The radiologist subsequently performed the arthrographic procedures on 102 TMJs (18 unilateral and 42 bilateral). Diagnostic agreement was determined for all possible diagnostic categories including: normal disc position, TMJ internal derangement with reduction, TMJ internal derangement without reduction/acute, TMJ internal derangement without reductionlchronic, and osteoarthrosis. The significance of the diagnostic agreement between the clinicians and arthrography was evaluated with a Kappa Statistical Test, which showed good reliability. For epidemiological studies, it was concluded that clinical and tomographic evaluation would provide sufficient reliability for determination of the presence and stage of TMJ internal derangement. However, in a specific clinical situation, a difficult diagnostic problem may require the use of arthrography, depending on the impact of the diagnosis on subsequent treatment decisions.
The Effect of Sutural Growth Rate on Collagen Phenotype Synthesis
Authors: Yen E.H.K. , Yue C.S. , Suga D.M.
Published: November 2010

We determined the ratio of newly-synthesized type III collagen to the total of type I and type III collagen in mouse interparietal sutural tissue at selected ages between birth and adulthood (36 weeks old). We incubated mouse calvaria explants in Trowell-type organ culture dishes for one h and then added [14C]-glycine for two h. We dissected the interparietal sutural tissues for collagen solubilization by limited pepsin digestion. Fluorographic visualization of separated radiolabeled collagens, after SDS-PAGE, found the ratio of collagen type III a-chains to the total type I and type III a-chains to be age-dependent. The proportion of type III α -chains at birth was quite high, but there was a significant drop (p<0.05) during the first two days of life, probably because of the sudden environmental change from in utero. The proportion of type III α -chains rose significantly from day 2 to day 4, reaching a maximum and then dropping significantly to about the same proportion as at birth by day 7. A further significant drop took place during the second week of life, with the proportion stabilized at around 3.5% at two weeks to ten weeks of age. A final significant drop during the eleventh week of life led to no detectable synthesis of type III collagen after 12 weeks of age. The changes in the collagen phenotype ratio did not relate to changes in body weight during growth and development, which suggests that the interparietal suture may have an independent maturing pattern. Correlation of the ratio of newly-synthesized mouse interparietal sutural type III collagen with the growth rate of the rat interparietal suture (Massler and Schour, 1951) suggested a close relationship between high type III collagen ratios and periods of very rapid sutural growth. The desirable age for future orthopedic studies in Swiss male white mouse interparietal suture, in which collagen phenotype would be monitored, would be between four and ten weeks of age.
Effect of Firing Temperature and Water Exposure on Crack Propagation in Unglazed Porcelain
Authors: Anusavice K.J. , Lee R.B.
Published: November 2010

Static fatigue of dental ceramics results from the interaction of residual tensile stress and an aqueous environment. This phenomenon is a potential cause of delayed crack formation and propagation in ceramic or metal-ceramic restorations. For dental ceramics, the influence of microstructural defects such as porosity or fissures caused by incomplete sintering is not known. The objectives of this study were to characterize the influence of porosity (produced by underfiring) on the crack propagation resistance of two feldspathic porcelains and to determine whether lower stress corrosion susceptibility or higher fracture toughness accounts for the superior thermal shock resistance of one of these ceramics.

We underfired bars of each porcelain, 25 mm × 4 mm × 4 mm, by as much as 84°C below their recommended firing temperatures. After polishing the specimens through 0.05 μm alumina, we induced cracks in their surfaces with a Vickers microhardness indenter. Semicircular cracks, which were produced under an applied indenter load of 19.6 N, grew with time during storage in distilled water at 37°C. Underfiring of both ceramics caused a slight increase in fracture toughness and a relatively small change in pore volume fraction until we underfired the ceramics at 30°C or more. The crack propagation data indicate that the higher thermal shock resistance of one of the ceramics-as measured previously by a water-quench technique-may be due to its greater resistance to stress corrosion at the initial stage of crack propagation.
The Effect of Sugar Cane Chewing on the Development of Dental Caries
Authors: Frencken J.E. , Rugarabamu P. , Mulder J.
Published: November 2010

In Tanzania, the effect of sugar cane chewing on the development of caries was investigated. Two groups were selected; those who had easy access to sugar cane (sugar cane cutters) and those who did not (sisal plant workers). These groups had a similar socio-economic background, had similar levels of fluoride in drinking water, consumed similar amounts of refined sugar per day, but had a significant difference in number of pieces of sugar cane chewed per day. The caries prevalence in both groups was low compared with that in adult populations in Western countries. Sugar cane cutters had significantly higher mean DMT/S scores than sisal plant workers. Analysis of Variance revealed a weakly significant effect of sugar cane chewing on the caries scores (p = 0.02 for DMT and p = 0.05 for DMS). Results of the study suggest that sugar cane chewing in large quantities over a long period has a caries-promoting effect in populations with a low caries prevalence, and further, that sugar sales figures reported for such populations are of questionable reliability.
A Confocal Optical Microscope Study of the Morphology of the Tooth/Restoration Interface using Scotchbond 2 Dentin Adhesive
Authors: Watson T.F.
Published: November 2010

It is difficult to avoid specimen damage when one is preparing an adhesiveladherend interface for examination using conventional optical or scanning electron microscopy. Fluorescence imaging with a confocal optical microscope has facilitated evaluation of the distribution of Scotchbond 2 dentin adhesive, in an in vitro study with P50 composite resin used as the restorative material. The adaptation of the adhesive and restoration to the tooth was excellent. Gap formation between the restoration and the tooth was observed only when the adhesive system was used incorrectly. Contributions of the primer film former (Scotchprep) and hardening film former (Scotchbond 2) to the adhesive interface with the tooth and overlying composite restoration could be identified. The dentin smear layer was incorporated by the Scotchprep and subsequently impregnated by the Scotchbond 2. Control of the film thickness was difficult. Cracking and cohesive failure within the adhesive were observed when the film thickness exceeded 70 μm, with such thicknesses easily achieved in internal line angles. The extent of the slippery air-inhibited layer was considerable, but could be reduced if the adhesive was wiped with a cotton wool pledget. The distribution of the Scotch bond 2 within the tooth was localized to the smear layer and dentin up to 50 μm deep to it. This study has shown the penetration of Scotch bond 2 dentin adhesive within the tooth and its distribution within the restoration.
An Investigation into the Use of Restriction Endonuclease Analysis for the Study of Transmission of Mutans Streptococci
Authors: Kulkarni G.V. , Chan K.H. , Sandham H.J.
Published: November 2010

Restriction endonuclease analysis (REA) was performed on the total cellular DNA from each of 396 strains of mutans streptococci (1) to determine its potential usefulness for the study of transmission of the organism and (2) to document the proportions and variety of strains harbored by members of a small group of families. The DNA was digested with restriction enzyme EcoRI and/or Hindlll, electrophoresed on agarose gels, and the resulting patterns compared. The strains examined included fresh isolates from 58 subjects, including 19 strains from each member of five families. The sensitivity and reproducibility of REA patterns from the mutans streptococci seemed ideal for studies of their epidemiology and transmission. The pattern of each isolate from humans was unique, except for isolates from the same individual or from the same family. REA types from subjects from different families were always heterogeneous. A high frequency of multiple REA types (up to 5) was observed in many subjects. While evidence for intra-familial transmission was obtained, including transmission between spouses, there was also strong evidence of frequent sources of infection outside of the family. Mutations of strains to streptomycin resistance or to lactate dehydrogenase deficiency caused no detectable change in the REA patterns. The lack of plasmids in any of the 57 fresh isolates that were examined for them suggested that they may have contributed little to the heterogeneity of the patterns seen.
Scanning Electron Microscopy of Monkey Secretory-and Transitional-stage Enamel Organ Cells
Authors: Skobe Z. , Prostak K.S. , Stern D.N.
Published: November 2010

This scanning electron microscope (SEM) study of secretory- and transitional-stage enamel organ cells of the permanent dentition of Macaca mulatta and Macaca arctoides was undertaken because the topography of these cells in primates has not been described in the literature. Comparison of our results with murine enamel organ morphology reported previously revealed not only many similarities, but also some significant differences.

Tooth buds of the permanent dentition were routinely prepared for SEM. Murine secretory-stage ameloblasts have been described to be 65-70 μm long, with smooth lateral membranes, but those of monkeys were only 30-35 μ m tall, with four different lateral plasma membrane configurations: smooth, filamentous, longitudinally ridged, and transversely ridged. The filamentous form was most common. Cells were seen with either transverse or longitudinal ridges in the basal half, and with filamentous ridges in the apical portion; this indicates modulation between these forms. Because of the extraordinary similarity between these lateral membrane modulations and those of rat incisor maturation ameloblasts, a comparable function is proposed — namely, that monkey secretory ameloblasts function, in part, in the resorption and mineralization of enamel matrix. There were several layers of rounded stratum intermedium cells basal to monkey secretory-stage ameloblasts, but only one layer of cuboidal stratum intermedium in rodents. The stellate rcticulum cells of rats and monkeys appeared attenuated, with large extracellular spaces.

There was little or no reduction in cell length of monkey transitional-stage ameloblasls. The position of the nuclear bulge differentiated transitional- from secretory-stage ameloblasts. The lateral surfaces of monkey transitional ameloblasts had interdigitating bulbous extensions of cytoplasm, whereas those of mice were smooth, and became microvillous late in the transition stage. In this stage, monkey and murine stratum intermedium, stellate reticulum, and the outer enamel epithelium cells changed morphology to become papillary cells with microvillous surfaces. Clusters of papillaty cells were separated from each other by anastomosing blood vessels, with diameters ranging from 10 to 12 μ m in monkeys, but from only 5 to 8 μm in murine incisor teeth.
Effect of Admixed Indium on Mercury Vapor Release from Dental Amalgam
Authors: Powell L.V. , Johnson G.H. , Bales D.J.
Published: November 2010

The purpose of this study was to evaluate the effect of admixed indium on the amount of mercury vapor released from dental amalgam. We made amalgam specimens according to ADA Specification Number 1. We added various amounts (0-14% by weight) of indium to the alloy powder. We also tested the commercial amalgams Dispersalloy, Valiant, and Indiloy. Specimens were held at 37°C and 100% humidity. We used a Jerome Mercury Vapor Analyzer (model 411) to measure the mercury vapor released. We analyzed the data by means of AN-OVA and Student-Newman-Keuls procedures. Admixed indium significantly decreased the amount of mercury vapor released from dental amalgams; the period of the greatest effect on mercury vapor released was during the setting phase of amalgam; and dental amalgams with greater than or equal to 8% admixed indium released the least amount of mercury vapor.
An in vitro Investigation of the Effects of Glass Inserts on the Effective Composite Resin Polymerization Shrinkage
Authors: Donly K.J. , Wild T.W. , Bowen R.L. , Jensen M.E.
Published: November 2010

We placed an MOD preparation in each of 12 permanent molars, then restored each tooth with a posterior composite resin by means of six different application techniques (I-polymerization as one complete unit; II-polymerization as one complete unit with glass inserts; IIIpolymerization in gingivo-occlusal increments; IV-polymerization in gingivo-occlusal increments with glass inserts; V-polymerization in bucco-lingual increments; and VI-polymerization in a gingival increment with glass inserts, then bucco-lingual increments). A precision strain gauge was attached to the buccal surface of each tooth and balanced at zero. After each increment was polymerized, the strain appearing on the strain gauge indicator was recorded. Each tooth was restored by use of all techniques; two teeth started with each technique. Results demonstrated the average microstrain units to be 127-1, 102-11, 105-III, 86-IV, 72-V, and 66-VI.

A randomized block design was the format used for data evaluation. Scheffé's Test indicated that composite resin placement and polymerization in bucco-lingual increments (V) created significantly less cuspal deflection than polymerization as one complete unit, with or without glass inserts (I and II), p<0.001, and gingivo-occlusal increments (III), p<0.05. Placement and polymerization in a gingival increment with glass inserts, then bucco-lingual increments (VI), also created significantly less internal deflection than polymerization as one complete unit, with or without glass inserts (I and II), p<0.001, and gingivo-occlusal increments (III), p < 0_ 005.
The Effects of Submandibularectomy on the Thymus and T-cell System of Mice
Authors: Letic-Gavrilovic A. , Radojičić Č. , Abe K.
Published: November 2010

Functional changes of the T-cell immune system in submandibularectomized (SMx) male mice of CBA/H strain were analyzed three or four weeks after treatment. Thymuses and spleens were weighed and morphologically examined by light microscopy. We tested proliferation rates of thymocytes and splenocytes (stimulated by Con A and PHA) and cytotoxic activity of T lymphocytes in SMx, CBA/H (H-2k) mice by means of the rejection test of allogeneic skin graft (Balb/c, H-2d) and a microcytotoxicity to allo-antigens of EL-4 tumor cells (H-2b).

Results showed a reduction of the weights of the thymus and spleen. However, there was increased functional capacity of the thymocytes - expressed as increased proliferation rates of the stimulated thymocytes, increased microcytotoxicity to allo-antigens of EL-4 tumor cells in vitro, and a reduction of the survival period of skin allografts in vivo. No morphological changes other than a reduction in both the cortex and medulla of the thymus were observed. The subpopulational changes within the T-cell system because of SMx indicate that the morphological atrophy could be just a consequence of SMx.
A New Method for Isolation of Salivary Neutrophils and Determination of Their Functional Activity
Authors: Ashkenazi M. , Dennison D.K.
Published: November 2010

The purposes of this study were to develop a new method for isolating salivary neutrophils (SPMNs), and to determine their functional activity. Studies of neutrophils in the oral cavity have been largely limited to crevicular PMNs, because of difficulties in obtaining viable SPMNs free of epithelial cells. A method to obtain SPMNs is presented. Donors performed rapid sequential rinsings by placing in their mouths 15 mL of Hanks' balanced salt solution [free of calcium or magnesium ions (HBSS-CMF)], which contained 0.1% gelatin, then swishing the solution for 30 s, and expectorating into a polypropylene receptacle containing 400 mL 4°C HBSS-CMF. This sequence was repeated for 20 min. The collected solution was stirred for 10 min, the cells were washed, and the re-suspended pellet was passed sequentially through a 20-μm and a 10-μm nylon mesh. The cells consisted of 97.7 ± 1.7% SPMNs, only 2.3% epithelial cells, and were almost free of oral debris.

The SPMNs were studied for CDllb expression, H2O2 production, and F-actin polymerization. SPMNs had significantly higher resting values for CDIIb, H2O 2 production, and F-actin polymerization compared with blood neutrophils (BPMNs). SPMNs responded to stimulation by chemotactic peptide or phorbol ester in a dose-dependent fashion, with levels of CDllb, H2O 2, and F-actin comparable with BPMNs at optimal stimulant concentrations. The elevated resting levels of CD11b, H2O2, and F-actin for SPMNs were probably caused by exposure to gingival and oral bacteria. The ability of in vitro-stimulated SPMNs to increase their levels of CDllb, H2O2, and F-actin to levels comparable with BPMNs indicates that these cells can function after leaving the gingival crevices. The method described is relatively simple and provides a high number (4-30 × 10 6) of purified and functional SPMNs.
Fluoride Incorporation into and Retention in Remineralized Enamel
Authors: Jima Y. , Koulourides T.
Published: November 2010

This study assessed the incorporation of fluoride into remineralized enamel and the stability of the incorporated fluoride under various test conditions. Lesions were produced on bovine enamel slabs by a two-day immersion in 0.01 mollL lactic acid buffer containing 3.0 mmol/L Ca, 1.8 mmol/L P, and 1% CMC adjusted to pH 4. 0 at 37°C. The remineralizing solution contained the same amount of Ca, P, and CMC, plus 150 mmol/L NaCl and 3 ppm F, and was adjusted to pH 7.0 at 37°C. All slabs were exposed to this unstirred solution, which was changed every two days during the ten-day remineralizing period. The remineralized slabs were divided into four groups. Group A (the control group) received no further treatment. The other three groups were exposed for 24 h to either the intra-oral environment (Group B), a 1. 0 mol/L KOH solution (Group C), or a 0.01 mol/L lactic acid buffer (Group D).

Fluoride incorporation assessed by abrasion biopsy in 10-μm layers showed about 10,000 ppm F maximum in Group A. Similar levels of fluoride concentration from the surface to approximately 30μm thick were found in Groups A, B, and C. No appreciable fluoride was released from remineralized slabs from Groups B or C, and only a small fraction from Group D. Statistical analyses of the fluoride values showed no significant differences between the various test conditions in any of the layers sampled. No difference was evident in the CalP ratio between the ten-day remineralized enamel (Group A) and the treatment groups. The lack of appreciable fluoride loss from enamel with any of the above three conditions indicated a stable fixation of fluoride in the remineralized enamel lesions.
Relative Adherence of Bacteroides Species and Strains to Actinomyces viscosus on Saliva-coated Hydroxyapatite
Authors: Li J. , Ellen R.P.
Published: November 2010

The study was designed to compare the adherence of several Bacteroides species to A. viscosus. Using 3H, we labeled 24 laboratory strains, including 13 Bacteroides species and I I fresh clinical isolates of three Bacteroides species. Their adherence to A. viscosus bound to a saliva-coated mineral surface was quantified by liquid scintillation. Adherence relative to a standard strain, B. gingivalis 2561, was compared. Among the lab bacteroides, those of B. gingivalis (eight strains) were the greatest binders (mean, 80.5 ± 12.4%). Strains of other lab bacteroides bound less well (mean, 33.4 ± 6.3%). The difference in means was statistically significant (p<0.01). The mean for B. gingivalis strains was also significantly greater than that for strains of B. intermedius (51.7 ± 6.2%). Attachment of B . gingivalis was saturable in experiments in which either input concentration or time was the independent variable, indicating that B. gingivalis cells do not accumulate in this in vitro simulation of plaque formation by binding to each other. Subculture did not seem to affect the degree of binding.
The Permeability of Human Oral Mucosa and Skin to Water
Authors: Lesch C.A. , Squier C.A. , Cruchley A. , Williams D.M. , Speight P.
Published: November 2010

Specimens from fbur regions of oral mucosa (palate, buccal mucosa, lateral border of the tongue, and the floor of the mouth) and of abdominal skin were taken from 58 individuals at autopsy, for determination of permeability constants (Kp) to tritium-labeled water. Comparisons between fresh specimens and those stored at -80°C revealed no significant effect on Kp as a result of freezing; similar results were found with use of specimens from corresponding regions of the pig. Values for Kp were significantly different for all of the tissue regions examined and ranged from 44 ± 4 × 10-7 cm/min for skin to 973 ± 33 x 10-7 cmlmin for the floor of the mouth, which was the most penneable region. Similar differences were evident among corresponding regions of porcine oral mucosa and skin. Moreover, the Kp values obtained for human tissues were not significantly different from those of the pig, except for the floor of the mouth, which was more permeable in human than in pig tissue. The results reveal interesting differences in the permeability of human oral mucosa that might be related to susceptibility to mucosal disease in those conditions where local extrinsic etiological agents are implicated.
Adjustment of Frequently Used Chi-square Procedures for the Effect of Site-to-Site Dependencies in the Analysis of Dental Data
Authors: Donner A. , Banting D.
Published: November 2010

Donner and Banting (1988) presented a method of adjusting the standard chi-square test for the comparison of proportions when this procedure is applied to multiple-site dental data. The adjusted procedure allows for a comparison of two or more groups of subjects with respect to the prevalence over all sites of a specified characteristic, while taking site-to-site dependencies into account. In this paper, similar adjustments are presented for two other frequently used chi-square procedures, the chi-square test for linear trend and the Mantel-Haenszel test. Examples are given.
The Effect of Silicic Acid on Calcium Phosphate Precipitation
Authors: Damen J.J.M. , Ten Cate J.M.
Published: November 2010

So that a possible involvement in the mineralization of dental plaque could be investigated, the effects of silicic acid on calcium phosphate precipitation were assessed in vitro. By measuring the decrease in Ca2+ concentration (by means of ion-selective electrodes), we determined both spontaneous precipitation and seeded crystal growth from solutions that contained 1 mmol/L calcium, 7.5 mmol/L phosphate, 50 mmol/L Hepes pH 7.2, and various amounts of silicic acid. Polymerized silicic acid, but not its monomer, was found both to cause a 60% reduction in the lag period that precedes spontaneous precipitation and to enhance the growth rate of seeded hydroxyapatite crystals. Silica suspensions showed effects similar to those of polysilicic acid. In all cases, the precipitated material was found to be hydroxyapatite. Whereas seeded brushite crystals grew slowly without silicic acid, hydroxyapatite was the only mineral detected after crystal growth in the presence of silicic acid. Apparently, polysilicic acid acted as a substrate for hydroxyapatite nucleation, inducing secondary nuclei on both hydroxyapatite and brushite crystals. The finding that polysilicic acid could overcome part of the inhibitory effect of a phosphoprotein on calcium phosphate precipitation gave additional support for the idea that polysilicic acid and silica may promote the formation of dental calculus.
Serological Studies of Peptostreptococci Using an Indirect Fluorescent Antibody Test
Authors: Collins M.L.Z. , Falkler W.A. , Hall E.R. , Graham M.B.
Published: November 2010

Members of the genus Peptostreptococcus are frequent isolates from periodontal lesions. A study was undertaken for determination of the serological relationships of oral and non-oral strains of several species of this genus. Eighty-nine strains of peptostreptococci representing seven species were tested by means of an indirect fluorescent antibody technique (IFA), with rabbit antisera to Peptostreptococcus anaerobius ATCC 27337, Peptostreptococcus micros VPI 2618-A, and Peptostreptococcus productus ATCC 27340. Each antiserum showed positive fluorescence when reacted with homologous cells. When anti-P. micros VPI 2618-A serum was added to suspensions of P. micros ATCC 33270 and clinical isolates of P. micros in the IFA, positive fluorescence was observed to a titer of 1:64 with 26 out of 29 strains. Positive fluorescence was also seen when P. anaerobius VPI 5737 and clinical isolates of P. anaerobius were tested with anti-P. anaerobius ATCC 27337 serum; a titer of at least 1 :64 was observed in 10 out of 14 strains. These results support the presence of two serological groups of P. anaerobius, rabbit anti-P. anaerobius ATCC 27337 serum reacting with Group II organisms. No interspecies cross-reactivity was observed except with four strains of Peptostreptococcus magnus, which reacted with several antisera as well as with normal rabbit serum and the saline controls. These results indicate that rabbit antisera and the use of an IFA are useful in the identification of P. anaerobius and P. micros from oral lesions.
The Effect of Chronic Atropine Treatment on Salivary Composition and Caries in Rats
Authors: Watson G.E. , Pearson S.K. , Falany J.L. , Culp D.J. , Tabak L.A. , Bowen W.H.
Published: November 2010

Many instances of salivary dysfunction in humans can be traced to the use of medications that have hyposalivary side-effects. In this study, atropine, a cholinergic antagonist, was administered chronically to rats by use of osmotic mini-pumps. Steady-state blood levels, similar to levels obtained in human multiple oral dosing, were thus maintained. Atropine delivered in this manner for 24 days was found to decrease protein concentration of parotid saliva (p<0.05) elicited by pilocarpine, and to increase smooth-surface caries scores (p<0.05) in rats fed a cariogenic diet.

Parotid saliva collected via ductal cannulation from rats subjected to chronic atropine administration (and stimulated to secrete by pilocarpine) exhibited increased levels of two basic proline-rich proteins (Peak A and SP-3), as evaluated by SDS-PAGE, compared with those observed in saliva from controls.

Cannulation of sublingual glands in animals receiving high doses of atropine produced no measurable secretion upon pilocarpine stimulation. Carbachol stimulation of dispersed cell aggregates of sublingual glands from sham-operated and high-dose atropine groups indicated that the glands responded similarly once the antagonist was washed from the system, implying that the lack of secretion in vivo was caused by antagonism of the cholinergic receptor by atropine.

Our observations suggest that this model system can be exploited for determination of the effects of chronic administration of hyposalivary drugs on salivary composition and caries rates.
The Measurement of Toothbrush Wear
Authors: Rawls H.R. , Mkwayi-Tulloch N.J. , Casella R. , Cosgrove R.
Published: November 2010

Toothbrushes wear out and progressively lose their ability to clean as the bristles abrade and become curled and matted. To study the factors that influence this process, we developed a quantitative measure of bristle splaying (wear index) and a method for judging and ranking the overall state of brush deterioration (wear rating) and used these to determine the effects of the individual user, brush design, time in use, and bristle material.

Wear index is the average increase in brush-head dimensions normalized for maximum bristle length, and is dimensionless. Wear rating is a subjective means of classifying the increasing severity of deterioration on a scale of 0 to 3. The wear characteristics of a variety of commercial and experimental brushes with different design features were determined. Test variables were time in use, brush design (e.g., geometry and size of the brush head), and bristle composition. Time of use, the individual user, and bristle composition were found to have the strongest influences on splaying, and brush design was found to have the least influence.

The wear index offers a quantitative means of comparing brushes of different dimensions at various stages of splaying. The wear rating, although qualitative, is a quick means of ranking brushes in various stages of deterioration. The two methods correlate (R2 = 0.87), and both are sensitive to several factors that affect brush durability. Therefore, these methods appear to be suitable not only for research, but also for quality control, the setting of standards, and for substantiation of advertising claims.
Effects of Varnishes Containing Chlorhexidine on the Human Dental Plaque Flora
Authors: Schaeken M.J.M. , Van der Hoeven J.S. , Hendriks J.C.M.
Published: November 2010

This study describes the effects of varnishes containing 0%, 10%, 20%, or 40% chlorhexidine diacetate on the microflora of human fissure dental plaque. Sandarac, a natural resin, was used as the varnish base. Ten subjects, each with at least four sound fissures harboring high levels of Streptococcus mutans, participated in the study.

The fissures in each of the individuals were randomly assigned to four experimental groups, in each of which one of the varnishes was tested. The varnish treatment consisted of a single application of a small amount of varnish onto the fissures. Apart from the selected fissures, the rest of the dentition was left untreated. All chlorhexidine-containing varnishes selectively suppressed S. mutans in fissure plaque, and had no effect on total viable counts or on the numbers of Actinomyces viscosus/naeslundii and Streptococcus sanguis beyond one week.

The extent of the suppression depended upon the concentration of chlorhexidine in the varnish, 40% chlorhexidine varnish giving the greatest suppression of S. mutans. At 22 weeks, after a single treatment with varnish containing 40% chlorhexidine, mean S. mutans counts were more than ten times lower than in the control or 10%chlorhexidine varnish group. At that time, S. mutans was still undetectable in five out of ten experimental fissures in this group.

The results suggested that sandarac varnishes containing high concentrations of chlorhexidine can be used successfully for long-term suppression of S. mutans in dental fissures.
Growth Patterns of the Rabbit Masticatory Muscles
Authors: Langenbach G.E.J. , Weijs W.A.
Published: November 2010

The post-natal growth of the masticatory muscles in the rabbit was examined. By means of anatomical dissection and measurement, total muscle length, muscle fiber length, and muscle weight were determined in animals varying in age between one week and 36 months and exhibiting a 50-fold weight increase. Growth data were fitted by linear regression models with facial skull length used as the independent variable. Many deviations occur from size-dependent isometric growth. The muscles can be divided into three groups, according to their pattern of weight increase: The jaw openers grow negatively allometrically, and their contribution to total muscle weight decreases with time; the temporal muscle grows negatively allometrically but its relative weight proportion remains about the same; the masseter and medial pterygoid muscles have positively allometric growth, and their contribution to total muscle weight increases strongly. Generally, the length of the muscles and of their fibers increases at lower rates than does the length of the facial skull. After weaning, the rate of longitudinal growth drops steeply in some muscles. Total fiber area or physiological cross-section (PCS) of muscles is computed from weight and fiber length. It increases positively allometrically in the jaw closers and negatively allometrically in the jaw openers. In the lateral pterygoid muscle, the increase of PCS changes from negatively- to positively-allometric growth after weaning. The study demonstrates that individual oral muscles follow different patterns of longitudinal and cross-sectional growth, so that their functional capacities (force, range of contraction) and mutual functional relationships are age-dependent.
Relaxation of Polymerization Contraction Shear Stress by Hygroscopic Expansion
Authors: Feilzer A.J. , De Gee A.J. , Davidson C.L.
Published: November 2010

We studied relaxation by hygroscopic expansion of the interfacial polymerization shear stress of bonded resin composites. In the experimental set-up, resin composite-cured-to-glass strips bent due to the polymerization shrinkage. The strips were stored wet or dry. The curvatures of the bent strips were recorded, by the scanning of the glass surfaces with a contact profilometer, periodically over a period of two months. From the measured deflections, we calculated the maximum tangential bending stress in the resins near the adhesive interface, which provided an estimation for the maximum shear stress values occurring at both ends of the strips. In the particular experimental set-up, the shear stresses in Bis-GMA/TEGDMA and urethane dimethacrylate-based resins were either fully relieved or converted into an "expansion stress" by hygroscopic expansion. The hydrophobic tricyclodecane dimethacrylate-based resins showed very little stress relaxation.
Inductive Influences of Demineralized Dentin and Bone Matrix on Pulp Cells: an Approach of Secondary Dentinogenesis
Authors: Tziafas D. , Kolokuris I.
Published: November 2010

The effects of demineralized dentin and bone matrix on dental ectomesenchymal cells were evaluated after observation periods of twa or three weeks. Autogenous dentin and bone matrix, obtained from the crowns of primary molars or maxillary cortical bone, respectively, were demineralized with 3% acetic acid and implanted into pulpal or papilla sites of erupting dog teeth: first molars, fourth premolars, and canines. Dentin histogenesis associated with odontoblastic arrangement was demonstrated in relation to all dentin implants in pulpal sites. Deposition of osteodentin, followed in some areas by tubular predentin formation, was observed in contact with bone implants in pulpal sites. In papilla sites, the dentin implantation exhibited bone-like matrix formation, while bone implants were encapsulated by connective tissue. The interactions of pulp cells with demineralized dentin matrix constitute a model for experimental inductian of secondary dentinogenesis and odontoblast-like cell differentiation.
Alveolar Bone Loss of Senescence-accelerated Mouse (SAM)
Authors: Sashima M. , Satoh M. , Suzuki A.
Published: November 2010

SAM-R/1/Iw (senescence-accelerated mouse, resistant) and Pl2/Iw (senescence-accelerated mouse, prone) under a conventional environment and eating standard pellets were examined for alveolar bone loss and the presence of periodontitis around maxillary and mandibular molars as a function of age. Neither SAM strain manifested a chronic periodontitis similar to that in humans, and no obvious plaque and calculus were observed. However, in both strains, 15% of M3 was lost after 13 months of age, and alveolar bone loss gradually increased with advancing age. Though there was no significant difference in the incidence of M3 loss between the two strains, P/2/Iw showed a higher alveolar bone loss around all molars than did Rl1/ Iw after one month of age throughout their life span. For Ml, the difference in alveolar bone loss between Pl2/Iw and Rl1/Iw was significant, and it was probably caused by the difference in degree of molar eruption. Other factors, such as occlusal trauma and gingivitis, may play some role in alveolar bone loss.
Determination of Pseudocholinesterase Activity in the Gingival Crevicular Fluid, Saliva, and Serum from Patients with Juvenile Periodontitis and Rapidly Progressive Periodontitis
Authors: Yamalik N. , Özer N. , Çaglayan F. , Çağlayan G.
Published: November 2010

By use of a spectrophotometric method, pseudocholinesterase (PCE) activities were determined in gingival crevicular fluid (GCF), saliva, and serum from patients with juvenile periodontitis (JP) and rapidly progressive periodontitis (RPP) and from controls. The PCE activity in the GCF samples was 181 ± 48 U/L in the JP group, 588 ± 135 U/L in the RPP group, and 88.5 ± 29.1 U/L in the control group. Saliva PCE activity levels were 9.1 ± 1.7 U/L in the JP group, 21.8 ± 4.5 UlL in the RPP group, and 12.7 ± 0.8 UlL in the control group. GCF contained a higher PCE activity than saliva but a lower one than that of serum. The RPP group had a significantly higher PCE activity in both the GCF and saliva samples. No significant differences could be found regarding serum enzyme levels. Also, no significant correlations were present between biochemical values and the severity of periodontal disease. GCF may be an important source for the PCE content of saliva. It is suggested that the increased PCE activity seen in RPP patients might be caused by either the direct production of esterases by bacteria or the induction of esterases during periodontal destruction.
Comparison of Lead Levels in Human Permanent Teeth from Strasbourg, Mexico City, and Rural Zones of Alsace
Authors: Frank R.M. , Sargentini-Maier M.L. , Turlot J.C. , Leroy M.J.F.
Published: November 2010

A comparative study of the mean lead concentrations in enamel and dentin of human premolars and permanent molars was conducted by means of a systematic sampling procedure with energy-dispersive x-ray fluorescence analysis. In a first series of analyses, no significant statistical differences in mean lead concentrations at various levels of enamel and dentin were noted between young patients of Strasbourg and those of small villages of Alsace, nor between elderly patients living in these two locations, despite the fact that motor traffic was significantly lower in the rural zones. However, in both locations, a significantly higher concentration of lead was observed in enamel and dentin in relation to age. In a second series of analyses, the mean lead concentrations of both dental hard tissues of premolars and permanent molars of young individuals from Strasbourg, rural Alsace, and Mexico City were compared. Significantly higher mean lead concentrations were found in enamel and dentin samples from Mexico City. This was most evident for inner coronal dentin (5.7 and 6.1 times greater than in teeth of Strasbourg and rural zones of Alsace, respectively) and for pulpal root dentin (6.9 and 8.9 times greater than in teeth of Strasbourg and rural zones of Alsace). It is proposed that the higher lead concentrations are related to the higher lead content of motor gasoline and to more intense traffic conditions. The dental hard tissues appear to be of value for the study of environmental lead pollution.