bluuebunny/crossref_metadata_2025 huggingface dataset:
Application to Forensic Odontology of Aspartic Acid Racemization in Unerupted and Supernumerary Teeth
Authors: Ogino T. , Ogino H.
Published: November 2010

Racemization of aspartic acid in dentin protein during the human lifetime progresses with age. The extent of racemization of aspartic acid in coronal dentin of normal permanent teeth can be used in forensic odontology to estimate the age of an individual at the time of death (Ogino et al., 1985). A series of experiments was conducted with dentin separated from unerupted and supernumerary teeth of various ages in an attempt to evaluate the advantages and limitations of this age-estimation method. The current study on nine tooth specimens showed that some unerupted permanent teeth with normal-sized and -shaped crowns (impacted third molar, canine, and incisor) could be used to estimate the age of individuals at the time of death within ± 4 years. However, supernumerary teeth (mesiodens, paramolar) with extremely tiny (length of crown: 4~5 mm) and abnormally shaped crowns could not be used for analysis. In such cases, the estimated age of individuals analyzed by the racemization method deviated considerably from their actual age.
A New Ion-coating Surface Treatment of Alloys for Dental Adhesive Resins
Authors: Tanaka T. , Hirano M. , Kawahara M. , Matsumura H. , Atsuta M.
Published: November 2010

4-META and new phosphate-methacrylate resins adhere strongly to dental alloys. However, for strengthening the water durability of the adhesive interface, the oxidation of the alloy surface is indispensable. A new oxidation method using ion-sputtering was developed, and the effectiveness of this surface treatment on two dental alloys-a type IV gold alloy and Ni-Cr-Be alloy-was investigated. As an endurance test, thermocycling for a maximum of 100, 000 cycles was adopted, and the tensile adhesive bond strength was then measured. Ion-coating the surface of the alloys resulted in strong bonds with adhesive resins, and after 100, 000 thermocycles, a bond strength of above 20 MPa was maintained.
In vitro Effects of Calcitonin and/or Parathyroid Hormone on Odontogenesis of Mouse Embryonic Molars
Authors: Sakakura Y. , Fujiwara N. , Sugawara M. , Nawa T.
Published: November 2010

Mandibular first molars of mouse embryos were cultivated for examination of the effects of calcitonin (CT) and/or parathyroid hormone (PTH) on the odontogenesis of the molars, and for determination of whether and how CT, which is a PTH antagonist, has an influence on the effect of PTH on odontogenesis. On the second day, the inner enamel epithelium in the control group had already differentiated into pre-ameloblasts. Typical odontoblasts had secreted a layer of pre-dentin. On the fourth day of culture, the pre-ameloblasts achieved terminal differentiation into secretory ameloblasts, and enamel and dentin had already been deposited. PTH (1 unit/mL) inhibited the odontogenesis of the cultured molars during the designated culture periods (two and four days), while CT (0.5 unit/mL) stimulated odontogenesis. On the second day, the development of the molars in the CT + PTH group showed an intermediate stage between the control and PTH-treated explants, but on day 4 it corresponded to that of the controls. Moreover, when the molars exposed to PTH for two days were untreated and treated with CT for an additional two days, the former produced a small yuantity of enamel matrix, while the latter formed a large amount of the matrix. These histological findings were also supported by a morphometric analysis of the enamel matrix in the cultured molars. The present results suggest that CT stimulates, but PTH suppresses, the odontogenesis of the mouse embryonic molars, and that CT is an antagonist to the inhibitory effect of PTH on odontogenesis.
Finite Element Method Simulation of Bone Resorption Beneath a Complete Denture
Authors: Maeda Y. , Wood W.W.
Published: November 2010

Bone resorption beneath a maxillary complete denture was simulated by the finite element method, assuming that a threshold of compressive strain exists in the alveolar bone above which the resorption occurred. The pattern of predicted resorption was observed when 100 N of force was applied to three positions occlusally, and 20 N was applied facially. Moreover, we observed the effect of rebasing the denture after initial resorption. The results indicate that resorption was initiated on the facial and occlusal surfaces of the alveolar ridge and proceeded palatally. The resorption was greater as the occlusal load point moved facially and when the force was applied in the facial direction. When the load point was toward the facial, rebasing the denture accentuated the resorption, but when the load point was toward the palatal, the resorption was almost the same regardless of rebase. The pattern of simulated bone resorption was similar to that reported from clinical observations, which suggests that the resorption may be associated with compressive strains developed in the alveolar bone. The results argue for the importance of occlusal adjustment of dentures to move the occlusal load point palatally and produce balanced occlusion in protrusion and lateral excursions, especially after a rebase procedure.
Microbiology of Root Surface Caries in Humans
Authors: Bowden G.H.W.
Published: November 2010

Studies on the microbiology of root surface caries between 1970 and 1975 placed emphasis on Gram-positive pleomorphic filamentous rods, particularly Actinomyces viscosus and Actinomyces naeslundii. Both of these species had been shown to produce root surface caries in experimental animals. Since this time, studies have placed more emphasis on Streptococcus mutans, and S. mutans and Lactobacillus are significant in prediction of root surface caries risk in patients. Subsequent studies confirmed an association between S. mutans and 'soft' or 'initial' root lesions. Thus, it is important when determining the microflora of root surface lesions to make careful characterization of the state of the lesion.

A second important aspect of the analysis of bacterial communities associated with root surface caries is better definition of the organisms. Most studies have concentrated on 'target organisms' S . mutans, S. sanguis, A. viscosus, A. naeslundii, Lactobacillus, and Veillonella. However, it has been known for 17 years that the Actinomyces associated with the lesions may be variants of A. viscosus and A. naeslundii. Such strains (intermediate strains) have been described in taxonomic studies of Actinomyces, yet little is known of the differences in physiology of these strains or their relationship to root surface caries. A similar situation exists with oral Streptococcus where new taxonomic divisions are being proposed. Recognition of the potential diversity within the 'target' genera of root surface caries could yield valuable data. Recent studies suggest that this is so, since samples from root surface lesions which contain S. mutans and Lactobacillus show a high isolation of S . mitis 1 and no isolations of A. naeslundii.

Careful definition of the lesions of root surface caries and the flora will allow analysis to relate a specific bacterial community to the state of the lesion and assist in monitoring the control of the lesion through fluoride and antibacterials.
Root Hard-tissue Demineralization Rate Measured by 125I Absorptiometry: Comparison with Lesion-depth Measurements
Authors: Almqvist H. , Wefel J.S. , Lagerlof F.
Published: November 2010

The aim of the present study was to compare demineralization of root hard tissue, monitored by 125 I absorptiometry, with lesion-depth measurements under polarized light microscopy. The intact roots of ten human molars, which had not been exposed to the oral environment, were divided into 39 cementum/dentin blocks and exposed to a buffer solution of pH 4.5 containing 2.2 mmol/L calcium and inorganic phosphate. After demineralization for 3.5, 7, 14, and 21 days, transmission measurements by 125I absorptiometry were performed, and one block from each tooth was taken out of the solution for lesion-depth measurement. The results showed a high degree of correlation (r = 0.952) between lesion depth and change in transmission, with a more rapid increase initially in both variables. A linear relationship with the square root of time was found. Conversion of transmission data to lesion-depth data was possible when this caries model system was used on cementum/ dentin blocks.
Periostomy and Growth of the Mandibular Condyle in the Rat
Authors: Killiany D.M.
Published: November 2010

It has been shown that a release of periosteal tension may augment the growth of a long bone; however, similar experiments in the mandible have produced equivocal results. For further definition of the role of periosteal tension in the growth of the mandibular condyle, 80 young female Sprague-Dawley rats were randomly assigned to four equal groups: (1) sham, (2) condylotomy, (3) narrow periostomy, and (4) wide periostomy. All procedures were performed unilaterally. Lateral cephalograms, transcranial condylar radiographs, and metallic implants made possible the measurement of the actual increment of condylar growth over three post-operative periods: 0 to 14 days, 14 to 28 days, and 0 to 28 days. Analysis of covariance was performed (weight gain as the covariate) and, where overall significance was found, Tukey's HSD test was used for determination of individual group differences. Conservative, circumferential periostomy of the condylar neck as well as condylotomy failed to alter the condylar growth rate, whereas removal of a wide band of periosteum led to a small decrease. These findings suggest that, at least in the rat, periosteal tension plays only a minor role-if any-in the control of condylar/mandibular growth. Furthermore, a subsequent increase or decrease in condylar growth, in experiments that use a condylotomy model, cannot be attributed solely to a disturbance in periosteal integrity caused by the condylotomy.
The Utility of the BANA Test for Monitoring Anaerobic Infections due to Spirochetes (Treponema denticola) in Periodontal Disease
Authors: Loesche W.J. , Giordano J. , Hujoel P.P.
Published: November 2010

Treponema denticola, Porphyromonas gingivalis, and Bacteroides forsythus each possesses an enzyme(s) that hydrolyzes the synthetic substrate benzoyl-DL-arginine-naphthylamide (BANA). The presence of these organisms in a subgingival plaque sample can be determined by the ability of the plaque to hydrolyze BANA. In the present study, we describe the usefulness of the BANA test at various stages of a clinical trial of the efficacy of metronidazole in the treatment of periodontal disease. A BANA-positive test was significantly associated with high levels and proportions of spirochetes in the plaque, so that it provided information comparable with that which could be obtained by a microscopic examination of the plaque. Patients with such anaerobic spirochetal infections were randomly assigned to a group receiving either metronidazole or placebo (250 mg, three times a day) for one week and whose teeth were scaled and root-planed. The advantages of the decision that metronidazole be used were apparent from the comparison with the results obtained in the patients who received only the scaling and root planing. The initially BANA-positive teeth in the patients treated with metronidazole, scaling, and root planing gained attachment and exhibited a significant reduction in the need for periodontal surgery, when compared with the BANA-positive teeth in the patients who received only placebo, scaling, and root planing. After the conclusion of this therapy, those teeth with persistent BANA-positive plaques had significantly higher proportions and levels of spirochetes than did the teeth with BANA-negative plaques. A tooth site which tested BANA-positive after the initial therapy lost significantly more attachment in the year following active treatment than did a tooth site that tested BANA-negative, i.e., a mean difference of 0.48 mm per year. The ability of the BANA test to detect an anaerobic infection due to the BANA-positive species and possibly to predict future attachment loss indicates that this test may be helpful in the management of the periodontally diseased patient.
Electrochemical Impedance Characterization of Human and Bovine Enamel
Authors: Levinkind M. , Vandernooti T.J. , Elliott J.C.
Published: November 2010

The alternating current impedance characteristics of human and bovine enamel slices were measured in vitro. An electrochemical cell containing two platinum gauze electrodes and 0.01 mol/L KCI buffered to pH 7.4 at 20°C was used. The electrodes were attached to a potentiostat that was connected to a microcomputer-controlled frequency-response analyzer. Measurements were made at discrete frequencies between 1 Hz and 65 kHz by application of a sinusoidal potential of 50 mV (rms) across the assembled cell. The impedance was calculated from the input potential and the resulting measured flow of current. For quantitative evaluation of these measurements, an equivalent circuit was postulated. It contained five passive electronic components and accurately modeled the different specimens. Values for individual electrical components in the equivalent circuit were estimated by complex non-linear least-squares regression analysis. This study demonstrated that it is possible to measure and quantitatively distinguish between the impedance characteristics of: permanent human, deciduous human, and bovine enamel, as well as the enamel from a variety of sites from human teeth, some of which had been extracted prior to being fully erupted. Proposals are made as to which physical properties in the specimens are modeled by individual components in the equivalent circuit.
Invited Review: A Review of Quantitative Methods for Studies of Mineral Content of Intra-oral Incipient Caries Lesions
Authors: Ten Bosch J.J. , Angmar-Månsson B.
Published: November 2010

Modern prospective caries studies require the measurement of small changes in tooth mineral content. Quantitative measurements of changes in mineral content in a single caries lesion is desirable. Quantitative methods can be either destructive or non-destructive. The latter type permits longitudinal studies to be conducted. Various methods available for the analysis of lesion parameters are reviewed. The basic principle of each method is summarized, and its characteristics are discussed. For each method, the correlation between the measured parameter and mineral loss, the useful range of mineral loss, the discrimination threshold, and the repeatability, are presented. Where such quantities were not available in the original papers, they were calculated from literature data. A comprehensive table of specifications of all methods is given.
Detection of Periodontal Disease Activity with a Scintillation Camera
Authors: Reddy M.S. , English R. , Jeffcoat M.K. , Tumeh S.S. , Williams R.C.
Published: November 2010

The goal of this study was to assess the ability of a scintillation camera method to detect areas of active bone loss due to periodontitis. Technetium 99m methylene diphosphonate was used as the bone-seeking radiopharmaceutical. Bone-seeking radiopharmaceutical uptake (BSRU) was imaged and quantified in alveolar bone regions of interest with a scintillation camera and a computer. Analysis of the sequential radiographs over six months constituted the basis for determination of sites of active disease. The study was composed of two parts. First, 18 subjects, nine with adult periodontitis and nine controls, were enrolled in a cross-sectional study to determine whether the quantitative scintillation camera methodology detected differences in BSRU in periodontitis vs. periodontally healthy patients. Second, the nine patients with periodontitis were studied longitudinally in order to determine whether the BSRU examination was indicative of bone loss subsequently measured radiographically. In the cross-sectional study, the mean uptake ratio for the periodontitis group was significantly higher than that for the control group (1.63 ± 0.06 and 1.42 ± 0.04, respectively, p<0.01, t test). From the longitudinal study, the mean patient scintillation image uptake ratios were highly correlated with the mean bone loss determined from serial radiographs (p<0.01). The accuracy, sensitivity, and specificity of the quantitative gamma camera method for detecting site(s) of active bone loss within the region of interest were assessed relative to the longitudinal radiographic data. The accuracy, sensitivity, and specificity were 85%, 90%, and 79%, respectively. Alveolar bone scintigraphy with a gamma camera and computer may provide a simple and valid technique for the immediate indication of areas of periodontal disease activity.
Microleakage of Three Cement Bases
Authors: Heys R.J. , Fitzgerald M.
Published: November 2010

The purpose of this study was to evaluate the ability of a glass-ionomer cement-base material to prevent bacterial penetration along the dentin interface and to compare it with two conventional cement-base materials. A total of 107 Class 5 restorations was placed in Rhesus monkey teeth by means of three test materials [zinc oxide-eugenol (ZOE), copalite varnish + zinc phosphate cement base (V + ZP), and a glass-ionomer lining cement (GI)], with unetched and unbonded resin composite used alone as a control material and as a final restoration over the test base materials. Following disinfection, Class 5 cavities were prepared on the buccal surfaces of the teeth to the inner one-half of dentin. A sterile filter-paper disk was then placed on the axial wall and covered with a Teflon disk. Next, the cavities were based to the dento-enamel junction with one of the test base materials and finally restored with unetched and unbonded resin composite. After five and 16 weeks, the filter-paper disks were retrieved and cultivated for the presence and type of bacteria. The five-week results showed positive growth in two groups: the composite-only controls and the V + ZP group. The 16-week results showed growth in all of the test groups, but only one of nine teeth showed growth in the zinc oxide-eugenol group and one of 16 teeth in the glass-ionomer group. The results of this study indicate that under the conditions tested, a glass-ionomer base was capable of minimizing bacterial penetration along the material-tooth interface.
Protection of Rats Against Dental Caries by Passive Immunization With Hen-egg-yolk Antibody (IgY)
Authors: Otake S. , Nishihara Y. , Makimura M. , Hatta H. , Kim M. , Yamamoto T. , Hirasawa M.
Published: November 2010

Hen-egg-yolk antibody (IgY) was prepared against Streptococcus mutans MT8148 serotype c that was cultivated in medium containing sucrose, and it was used in passive caries-immunity studies. Specific pathogen-free rats infected with S. mutans MT8148 (c) and fed with a cariogenic diet containing more than 2% immune yolk powder developed significantly lower caries scores than did the ones infected with the same strain and fed with a diet containing only control yolk powder obtained from non-immunized hens. Similar results were obtained in an experiment with rats infected with S. mutans JC-2 (c) strain. Rats provided a diet supplemented with 0.5% immune water-soluble protein fraction containing S. mutans-specific IgY and challenged with S. mutans MT8148 exhibited significantly fewer caries lesions, compared with control rats on the normal diet.
Influence of Operatory Size and Nitrous Oxide Concentration Upon Scavenger Effectiveness
Authors: Henry R.J. , Primosch R.E.
Published: November 2010

Concern regarding environmental health hazards for dental personnel chronically exposed to waste nitrous oxide (N2O) prompted this investigation. The influence on ambient N 2O levels of scavenging, operatory size, and N2O concentration delivered to the patient was evaluated during treatment of 36 pediatric dental patients. The results showed that scavenging significantly reduced ambient N2O levels measured at 50-56 cm from the patient's nose. Scavenged ambient N2O levels were also observed to decrease when N2O concentrations administered to the patient were reduced from 50 to 30%. This concentration effect was not observed in the non-scavenged groups. ANOVA showed that operatory size exerted a non-significant influence on ambient N2O. The data collected during routine treatment of pediatric dental patients demonstrated that the scavenging system tested significantly reduced waste N20 in the operator's breathing zone, nearly approximating the 25-ppm recommendation established by the National Institute for Occupational Safety and Health (NIOSH).
Compensatory Hyperplasia of the Rat Submandibular Gland Following Unilateral Extirpation
Authors: Schwartz-Arad D. , Michaelp Y. , Zajicek G.
Published: November 2010

This study investigated the morphological changes in rat submandibular glands undergoing compensatory hyperplasia. Fifteen adult male rats underwent left submandibulectomy, after which they were killed in groups of five (at days 3,7, and 14), and their right submandibular glands (SMG) were excised. Fifteen control rats were killed in groups of five (at days 0, 7, and 14), and their right SMG were removed. Sections of 3 μm were cut, and the parenchymal and stromal cells were counted in 50 microscopic fields and sorted according to their morphological features and "class". Class is equivalent to the number of nuclei in an acinar or tubular cross-section.

No change in glandular weight was noted post-surgery. Total cell count/field rose to 138.5 ± 7.1% of control values on day 3 after gland extirpation, remaining almost constant thereafter until the end of the experiment. Acinar cell count and class showed a 154.1% peak on day 3, followed by a 30% drop in cell count by day 7 and an equivalent decline in class by day 14. Tubular cell count increased gradually to 146.5% by day 14, without a change in class. In the first week, the increase in tubular cells was mainly due to intercalated duct (ID) cells, while in the second week, there was a sharp rise in granular duct (GD) cells. This diverging cellular behavior indicates that the GD cell stems from the ID cell.

The cellular changes in the hyperplastic SMG indicate death of newly generated acinar cells and expansion of the glandular progenitor compartment, as expressed in elongation of the ID.
Induction of Calcium Phosphate Precipitation by Titanium Dioxide
Authors: Damen J.J.M. , Ten Cate J.M. , Ellingsen J.E.
Published: November 2010

Titanium powder and various titanium dioxides were tested for their capacity to reduce the induction time for calcium phosphate precipitation from supersaturated solutions. Only after a pretreatment aimed at increasing its oxide surface layer was titanium powder found to accelerate the precipitation from solutions containing 2 mmol/L CaCl2, 2 mmol/L KH2PO4, 50 mmol/L Hepes, pH 7.2, and to induce precipitation from metastable solutions containing 1.2 mmol/L CaCl2, 1.2 mmol/L KH2PO4, 50 mmol/L Hepes, pH 7.2, at 37°C. Even stronger effects were found when suspensions of the titanium dioxides anatase or rutile (10-50 μg/mL) were added to these solutions. TiO2 appeared to serve as a reactive substrate for secondary nucleation at a wide range of calcium-to-phosphate ratios and concentrations, even in the presence of 40 mg/mL bovine serum albumin, which completely inhibited precipitation in control incubations. These results suggest that the oxide surface layer of titanium implants may induce calcium phosphate precipitation in the metal-to-bone interface, which may play a role in the integration of such implants in bone.
Enumeration of Oral Streptococci on Media Containing Different Concentrations of Sodium and Potassium Ions
Authors: Willcox M.D.P. , Irwin A.M. , Jacques N.A. , Knox K.W.
Published: November 2010

Laboratory "type" strains of oral streptococci were screened for their ability to grow on mitis-salivarius agar (MSA) in the presence of increasing concentrations of either Na + or K+ up to 500 mmol/L. Strains were generally better able to withstand increasing concentrations of Na+ than K +, although low numbers of colony-forming units (cfus) were seen with the highest concentration of either cation. Two strains of Streptococcus mutans, Ingbritt 162 and Ingbritt 175, behaved differently when the concentration of cation was increased from 50 to 200 mmol/L; the latter showed a marked increase in the number of cfus when the Na* concentration was increased from 50 to 200 mmol/L, whereas there was a decrease with strain Ingbritt 162. Strains of oral streptococci from the saliva of adults and children were isolated on modified MSA containing known concentrations of Na + and K+ and further examined if they showed "mutans-like" colony morphology. The number of cfus generally dropped as the concentration of Na+ or K+ was increased from 200 to 350 or 500 mmol/L. Greater numbers of streptococci were tolerant to Na+ than to K +. Half of the isolates were members of the Streptococcus sanguis group (SSG), either Streptococcus mitis or S. sanguis II, and these were more tolerant to high concentrations of Na+ or K+ than other isolates that were identified as Streptococcus morbillorum, Streptococcus acidominimus, and Streptococcus milleri.
Lysozyme Enhances the Inhibitory Effects of the Peroxidase System on Glucose Metabolism of Streptococcus mutans
Authors: Lenander-Lumikari M. , Månsson-Rahemtulla B. , Rahemtulla F.
Published: November 2010

The combined effect of the salivary peroxidase system and lysozyme on the glucose uptake of Streptococcus mutans NCTC 10449 was investigated. The bacteria were grown to late-exponential phase, washed, re-suspended in buffer at pH 6, and incubated with (1) 50 μg/ mL lysozyme from human milk for 60 min; (2) 7-15 μmol/L hypothiocyanous acid/hypothiocyanite for 10 min; and (3) lysozyme for 60 min prior to addition of and incubation with hypothiocyanous acid/hypothiocyanite for 10 min. Glucose uptake was initiated by adding the bacterial suspensions to 10 mL of pre-warmed 50 μmol/L glucose containing 0.98 μmol/L D-(U-14C-)-glucose, and the mixture was incubated in a shaking water-bath at 37°C. Samples were withdrawn at various time intervals, rapidly filtered through 0.45-μm membranes, washed with ice-chilled buffer, and the incorporated radioactivity determined. Lysozyme stimulated S. mutans glucose uptake slightly, but significantly inhibited S. rattus glucose metabolism. A 20-30% inhibition of radiolabeled glucose incorporation was observed with hypothiocyanous acid/hypothiocyanite alone. Incubation of the bacteria with lysozyme prior to addition of hypothiocyanous acid/hypothiocyanite containing peroxidase resulted in a total inhibition of the glucose uptake. In contrast, lysozyme in combination with hypothiocyanous acid/hypothiocyanite without peroxidase gave only a 30-50% inhibition. The addition of 5 mmol/L dithiothreitol after incubation with lysozyme and hypothiocyanous acid/hypothiocyanite eliminated the inhibition of the bacterial glucose uptake. The viability of S. mutans was not affected by treatment with any of the components used. Our results indicate that physiological concentrations of lysozyme and the salivary peroxidase system components have a synergistic effect which results in a significant inhibition of glucose metabolism by S. mutans.
A Study of the Ability of an in situ Remineralization Model to Differentiate between the Effects of Two Fluoride Dentifrices that Produced Significantly Different Clinical Caries Results
Authors: Mellberg J.R. , Petrou I.D. , Grote N.E.
Published: November 2010

The purpose of this study was to determine whether an in situ remineralization model was able to show a difference in the effects of two dentifrices of different fluoride concentrations and significantly different clinical efficacies. Three dentifrices were tested in a double-blind, cross-over study design. The products contained 0 ppm F, 250 ppm F, or 1000 ppm F from sodium fluoride and were formulated with a silica base according to the formulations used in a human caries trial (Koch et al., 1990).

Nineteen subjects each carried three or four thin sections of enamel in their partial dentures. The thin sections, containing artificial caries lesions, were covered with a steel mesh to provide space for plaque formation and then brushed in situ three times daily with the dentifrices. Following the two-week treatment periods, the specimens were removed from the dentures and analyzed for changes in mineral content. The findings showed that the placebo dentifrice (0 ppm F) resulted in 56.8 ± 74.3% demineralization, the 250-ppm-F dentifrice produced 12.9±41.3% demineralization, thereby showing partial caries protection, and the 1000-ppm-F dentifrice produced 17.3 ±32.1% remineralization. Linear regression analysis showed that the percent remineralization was significantly related to the fluoride concentration in the dentifrice (p < 0.001). The 250-ppm-F dentifrice was also significantly less effective than the 1000-ppm-F dentifrice (p = 0.04, one-tailed Fisher Protected LSD test).

These findings are in accord with the human caries trial and support the use of the present in situ remineralization model for prediction of the anticaries efficacy of fluoride dentifrice products.
Synthesis and Evaluation of New Oxaspiro Monomers for Double Ring-opening Polymerization
Authors: Stansbury J.W.
Published: November 2010

Polymerization with expansion in volume can be achieved with spiro orthocarbonate monomers through a double ring-opening process wherein two bonds are cleaved for each new bond formed. The resulting expansion can be applied to counter the polymerization shrinkage associated with the conventional methacrylate monomers used in dental composites and thereby provide formulations with drastically reduced degrees of shrinkage. New monomers have been prepared that exhibit enhanced reactivities and ring-opening efficiencies compared with earlier free-radical-polymerizable oxaspiro compounds. In dental composite formulations, the monofunctional oxaspiro monomers provided DTS values equivalent to those of the controls under certain curing conditions; however, only modest reductions in polymerization shrinkage were observed.

2,3-Bis(methylene) spiro orthocarbonate monomers with a conjugated diene structure were also synthesized and evaluated. These novel monomers appear to offer significant potential for future development of free-radical ring-opening polymerization. While visible-light-cured formulations of the bis(methylene) compounds with methacrylate comonomers did not yield acceptable composite materials in this initial attempt, the high reactivity and the ability to form rigid, cross-linked polymers make this type of monomer worthy of continued investigation. These properties may allow the bis(methylene) oxaspiro monomers to be used alone or in concert with other ring-opening monomers for special applications.
Microbiological Aspects of the Chemical Control of Plaque and Gingivitis
Authors: Marsh P.D.
Published: November 2010

Antimicrobial agents, delivered either by mouthrinse or toothpaste, can be used to maintain plaque at levels compatible with oral health by (a) reducing existing plaque, (b) preventing the formation of new plaque, (c) selectively inhibiting those particular bacteria that are associated with disease, and (d) inhibiting the expression of virulence determinants. Although many antimicrobial agents would appear to be suitable for plaque control, few have been found to possess clinical efficacy. This is because of inherent problems in the mode of action of agents in the mouth, and with difficulties with their formulation into dental products. Currently formulated antimicrobial agents include metal salts (e.g., zinc, stannous, copper), phenols (triclosan), plant extracts (sanguinarine), enzymes (e.g., glucanase, amyloglucosidase/glucose oxidase), "essential oils" (e.g., thymol, menthol), and bisbiguanides (chlorhexidine). Although many of these agents exhibit a broad spectrum of antimicrobial activity in the laboratory, they may display valuable selective properties on plaque. The effect of an agent will be concentration-dependent. Initially, the inhibitor may be briefly at levels above its MIC, but thereafter, it will be desorbed off oral surfaces and operate at sub-lethal concentrations. At these latter levels, agents can be effective by inhibiting metabolism (e.g., acid production, protease activity), and slowing bacterial growth. Agents with complementary modes of action are being combined to increase their antibacterial effectiveness. The long-term use of dental products containing antimicrobial agents should not (a) disrupt the natural balance of the oral microflora, (b) lead to colonization by exogenous organisms, or (c) lead to the development of microbial resistance. Several products are now available that satisfy these criteria, and are clinically effective in helping to control plaque and gingivitis.
Determination and Selection of the Optimum Number of Sites and Patients for Clinical Studies
Authors: Hujoel P.P. , DeRouen T.A.
Published: November 2010

Calculating required sample sizes is a critical step in the design of any study. For dental studies, the sample size needs to be specified at two levels: (1) the number of patients (n) enrolled in the study, and (2) the average number of sites (m) examined per patient. In general, m and n should be selected in such a way that the precision of the research findings is maximized, while the cost of the study is minimized. This objective can be realized by taking stock of the components of variation and the costs involved with enrolling patients and examining sites. The research cost for n patients ($C1/ patient), at an average of m sites per patient ($C2/site), can usually be approximated by n C1 + nm C2. The precision varies as a function of the variance components, m, and n. To optimize precision for a fixed cost, the average number of sites examined per patient (mopt) should be approximately equal towhere p is the within-patient correlation coefficient of the site-specific variable measured. When mopt is approximately equal to or in excess of the average number of sites availableper patient, whole-mouth examinations are indicated. When mopt is considerably smaller than the average number of sites available, the sample of optimum size should be obtained by some random mechanism. Examination of a number of sites considerably different from mopt results in a waste of resources, regardless of the number of patients studied. Standard statistical analyses for determination of the patient sample size required to obtain a pre-specified precision or power are discussed.
Effect of 45,X/46,XX Mosaicism on Root Morphology of Mandibular Premolars
Authors: Varrela J.
Published: November 2010

The effect of X chromosome mosaicism on root morphology of mandibular premolars was studied in 14 females with 45,X/46,XX chromosome constitution. Occurrences of two-rooted premolars and the morphology of the roots were examined from orthopantomograms. Six (43%) of the 45,X/46,XX mosaics had two-rooted mandibular premolars. Two-rooted first premolars were found in four (29%) and second premolars in three (21%); in one, all four mandibular premolars were two-rooted. The results indicate that the frequency of two-rooted mandibular premolars was similar in 45,X/46,XX mosaics and in 45,X females, and in both groups significantly higher than in normal 46,XX females. Compared with 45,X females, the 45,X/46,XX mosaics showed a slight tendency toward more simplified root morphology in the first premolars. The findings suggest that the presence of normal 46,XX cells among the defective 45,X cells does not affect the development of the mandibular premolar roots. Furthermore, the results do not support the earlier proposal that the presence of normal 46,XX cells in 45,X/46,XX mosaic individuals would be reflected in gradual normalization of dental development.
Early Bond Strength of Luting Cements to a Precious Alloy
Authors: Mojon P. , Hawbolt E.B. , MacEntee M.I. , Ma P.H.
Published: November 2010

Previous studies have reported that glass-ionomer and adhesive resin cements can bond to various alloys, while zinc phosphate cements lack this adhesive property. This study evaluated the bonding properties of three luting cements during the first seven days after cementation. Thirty cylinders were cast with a high-noble porcelain-fused-to-metal (PFM) alloy and luted in pairs with one of the cements. The joints were stored in water at 37°C for one, two, or seven days before being fractured in shear. The cylinders were re-used to provide 40 joints within each test group. The data were subjected to a Weibull analysis, a curve-fitting method shown to be appropriate for comparing the bond strengths of dental materials. The results showed that the zinc phosphate cement was the weakest material, whereas the adhesive resin produced the strongest joints. Microscopic observations of the fractured samples did not reveal any specific differences between the samples in terms of their mechanism of fracture. The glass-ionomer cement reached its maximum bond strength after two days, whereas storage time had no influence on the zinc phosphate cement. The adhesive resin cement was slightly, but not significantly, weaker after one week in water. We suggest that excessive loading of restorations cemented with glass ionomer should be avoided for the first two days after the placement. The use of an adhesive resin cement can be recommended on endodontically treated teeth, but further studies are needed to evaluate its biocompatibility and adhesion to dentin.
Effect of Age on Immunoglobulin Content and Volume of Human Labial Gland Saliva
Authors: Smith D.J. , Joshipura K. , Kent R. , Taubman M.A.
Published: November 2010

Stimulated lower labial (LLGF) and parotid salivary volumes and IgG, IgA, and IgM concentrations were measured in 264 subjects whose ages ranged from 17 to 76 years. A significant (p <0.001) age-related decline in LLGF output was observed for subjects over this age range. Sixty-three percent of the subjects in the 18-20-year-old group (n = 46) secreted at least 10 μL of labial saliva in a 7- 10-minute period, while approximately 70% of the subjects in the two oldest groups (61-70 and 71-76 years old) secreted less than 1 μL of LLGF during this time period (n = 64). No significant gender-based differences occurred in the volumes of labial saliva secreted. Stimulated parotid salivary flow showed no age-related trend in these subjects. Lower labial gland salivary IgA concentrations in an older population (mean age ± SD = 55.6 yr ± 1.3) were significantly lower (p < 0.025) than IgA concentrations in a younger population (20.7 yr ±0.8), when IgA was expressed as μg/mL LLGF collected. Immunoglobulin A concentrations in parotid saliva and IgG and IgM concentrations in labial and parotid saliva were not significantly different when the two age populations were compared. These data suggest that the physiological and immunological potential of labial gland saliva may decrease with age.
Comparison of Rates of Enamel Synthesis in Impeded and Unimpeded Rat Incisors
Authors: Skobe Z. , Heeley J.D. , Dobeck J.M. , Prostak K.S. , Maravelis L. , Stern D.N.
Published: November 2010

Periodic intubations of rats with solutions of fluoride (F) lead to the appearance of bands of disrupted pigmentation in continuously erupting incisors. Distances between fluorotic bands reflect time intervals between intubations. In this experiment, the periodicity of fluorotic banding was used for estimation of the rate of enamel synthesis in impeded and unimpeded rat incisors. Rats kept on a low-F diet and distilled water were intubated two or four times per week with 2 mg NaF/150 g body weight. In a group of rats, one of the mandibular incisors was cut at the gingival margin after two weeks, and intubations were continued for an additional two weeks. In another group of F-intubated rats, incisors were cut or notched at the gingival margin twice, six days apart. Control rats either received the same periodic F intubations or were maintained on the low-F diet without intubation.

Measurements of spacing between fluorotic bands were identical in impeded and unimpeded teeth, even though the latter erupted at a faster rate. In unimpeded mandibular incisors, there was a significant elongation of the secretory zone and a shortening of the pigmentation zone, resulting in reduced pigmentation intensity of the erupted portions of the teeth. The results show that the rate of enamel synthesis is independent of the eruption rate.
The Distribution of Saliva and Sucrose Around the Mouth During the Use of Chewing Gum and the Implications for the Site-specificity of Caries and Calculus Deposition
Authors: Dawes C. , Macpherson L.M.D.
Published: November 2010

Over a 20-minute period, subjects expectorated 8 samples of whole saliva (EWS) while chewing gum. Flow rates were calculated, and sucrose was analyzed in these samples as well as in saliva collected on filter paper strips from different tooth surfaces. Salivary film velocity (SFV), based on a 0.1-mm-thick film, was estimated from the clearance half-times of KCl in agarose disks positioned in different regions of the mouth. Salivary flow rate peaked at 5.1 mL/min in the first min but fell to about 1.25 mL/ min by the end of the 20 min of gum-chewing. In contrast, flow rate when subjects sucked sour lemon drops averaged about 5.3 mL/min throughout the 20-minute period. The mean salivary sucrose concentration during gum-chewing peaked in the second min at 384 mmol/L (13.1%) but had fallen to 14 mmol/L by the 15-20-minute time interval. The sucrose concentrations on the palatal surfaces of the upper incisors and the facial and lingual surfaces of the lower molars were not significantly different from that in EWS but were much lower on the facial surfaces of the upper incisors and molars, and on the lingual surfaces of the lower incisors. When flow was unstimulated, SFV was 0.8-1.0 mm/min on the facial surfaces of the upper incisors and lower molars but about 5-8 mm/min on the facial surfaces of the upper molars and on the lingual surfaces of the lower incisors and molars. During chewing-gum use, the SFV increased only to 4 and 10 mm/min on the facial surfaces of the upper incisors and lower molars, respectively, but on the facial surfaces of the upper molars and on the lingual aspects of the lower incisors and molars, it became equivalent to that in a well-stirred solution. This study showed that even during gum-chewing, which would be expected to facilitate the mixing of the different salivary secretions, the saliva provided a series of distinctly different fluid environments, some with cariogenic and others with calculogenic potential, for plaque in different regions of the mouth.
Power Spectral Analysis of Temporomandibular Joint Sounds in Asymptomatic Subjects
Authors: Gallo L.M. , Airoldi R. , Ernst B. , Palla S.
Published: November 2010

Very little has been done to quantify temporomandibular joint (TMJ) sound amplitudes and background noise and to determine the spectrum from healthy TMJs. Thus, the aim of this study was to record acoustically the sounds emitted by healthy TMJs with and without mandibular movements, for determination of baseline spectra. TMJ sounds were recorded bilaterally from 40 subjects with healthy joints by means of a self-developed recording system using miniature capacitor microphones inserted into the earpieces of a medical stethoscope placed in the meatus of the auditory canal. The recordings were performed without mandibular movements and during three consecutive opening and closing movements. The signals were high-pass-filtered at 50 Hz, low-pass-filtered at 2 kHz, and analyzed by fast Fourier transform computation on a 1024-point window (f = 5 kHz). The linearly weighted average baseline spectrum recorded without motion showed maximum values of 31 dBSPL (sound pressure level) with a standard error of + 2 to - 3 dB. The linearly weighted average movement spectrum had a peak of 66 dBSPL at 156 Hz and decreased almost linearly by about 40 dB/decade to 25 dBsPL at 2000 Hz with a standard error of ± 2 dB. Thus, the TMJ sound spectrum of mandibular movements in asymptomatic subjects differed at low frequencies by up to 35 dB from the baseline spectrum in absence of motion.
Calcification of a Cariogenic Streptococcus and of Corynebacterium (Bacterionema) matruchotii
Authors: Moorer W.R. , Ten Cate J.M. , Buijs J.F.
Published: November 2010

The main aim of this investigation was to challenge the idea that cariogenic streptococci do not calcify. Calcium uptake or calcification of Streptococcus mutans C180-2, proven to be an acidogenic and cariogenic strain, was compared with calcium uptake and calcification of Corynebacterium (Bacterionema) matruchotii, known as a ready calcifier. Bacteria were grown on Brain Heart Infusion Agar (BHIA) and on well-buffered semi-synthetic E-agar, both containing 1.4 mmol/L calcium, 2 g/L glucose, initial pH 7.4. Calcium uptake from BHIA by C. matruchotii (25 mmol Ca/kg wet bacterial cell mass), but not by S. mutans, was found. Grown as a plaque-like lawn on E-agar, the S. mutans cell mass concentrated calcium to 63 ± 11 mmol/ kg compared with 145 ± 61 mmol/kg in C. matruchotii. X-ray diffraction confirmed the presence of crystalline apatite in the bacterial cell masses. Electron microscopy revealed crystals and mineralized deposits in both organisms. Heavy calcifications in some cells of S. mutans were seen. Calcification was partly inhibited by magnesium ion and by methanehydroxybisphosphonate. S. sobrinus 6715, as well as freshly isolated S. mutans and S. sobrinus from patients, concentrated very large quantities of calcium, up to 500-fold from the medium, when maintained for several weeks on E-agar of initial pH 7.6. Our observations widen the view on acidogenic bacteria as mineralization agents and support the notion that members of the mutans group of streptococci may be involved in events that trigger heavy intracellular calcifications and, possibly, dental calculus formation.
The Effect of Fluoride Application on Fluoride Release and the Antibacterial Action of Glass lonomers
Authors: Seppa L. , Forss H. , Øgaard B.
Published: November 2010

The aim of this study was to investigate whether the release of fluoride and the antimicrobial effect of freshly mixed glass ionomers could be prolonged by application of fluoride on aged material. Test slabs of freshly mixed and aged (14 d in water) conventional and silver glass ionomer (Ketac-Fil and Ketac-Silver, Espe, Seefeld, Germany) and composite (Silux Plus, 3M, St. Paul, MN) were fitted into the bottom of a test tube. A layer of S. mutans Ingbritt cells was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% sucrose solution. After the incubation, pH, F, and Ca contents of the fluid phase, and F, Mg, P, and K contents of the cells were determined. The aged glass-ionomer samples were then covered with toothpaste (0.1% F) or with fluoride gel (1.25% F), and the composite samples with fluoride gel. After being thoroughly rinsed, S. mutans cells were incubated on the samples as above. The pH fall was significantly inhibited by freshly mixed glass ionomers, and there were changes in cellular cation and phosphorus contents. Large amounts of fluoride were found in the fluid and cells. For old glass ionomers, no inhibitory effect on pH fall could be seen. Fluoride release had decreased to a low level. Application of fluoride toothpaste on the material resulted in a small increase in the release of fluoride and slight inhibitory effects on bacteria. After application of fluoride gel, the fluoride contents of the fluid phase and cells were as high as in freshly mixed samples, and the inhibitory effect on pH fall and electrolyte metabolism was even more pronounced than initially. Fluoride release from old glass ionomers and their antimicrobial effect could be significantly increased by application of fluoride gel on the material.