bluuebunny/crossref_metadata_2025 huggingface dataset:
Submandibular Salivary Proteases: Lack of a Role in Anti-HIV Activity
Authors: Kennedy S. , Davis C. , Abrams W.R. , Billings P.C. , Nagashunmugam T. , Friedman H. , Malamudl D.
Published: January 2009

Whole human saliva contains a number of proteolytic enzymes, mostly derived from white blood cells and bacteria in the oral cavity. However, less information is available regarding proteases produced by salivary glands and present in salivary secretions. In the present study, we have analyzed submandibular saliva, collected without contaminating cells, and identified multiple proteolytic activities. These have been characterized in terms of their susceptibility to a series of protease inhibitors. The submandibular saliva proteases were shown to be sensitive to both serine and acidic protease inhibitors. We also used protease inhibitors to determine if salivary proteolytic activity was involved in the inhibition of HIV infectivity seen when the virus is incubated with human saliva. This anti-HIV activity has been reported to occur in whole saliva and in ductal saliva obtained from both the parotid and submandibular glands, with highest levels of activity present in the latter fluid. Protease inhibitors, at concentrations sufficient to block salivary proteolytic activity in an in vitro infectivity assay, did not block the anti-HIV effects of saliva, suggesting that the salivary proteases are not responsible for the inhibition of HIV-1 infectivity.
Perceptions of the Natural Dentition in the Context of Multiple Variables
Authors: Gift H.C. , Atchison K.A. , Drury T.F.
Published: January 2009

Perceived oral health status has been shown to be associated with a variety of single clinical and self-reported indicators of oral health and oral health-related behaviors. A behavioral model is utilized which hypothesizes that perceived condition of natural teeth is predicted by multiple factors, including individual demographic and enabling characteristics, other health perceptions and orientations, actual levels of diseases and conditions, and self-defined need for treatment. The data are from the clinical examination and adult questionnaire of Phase 1 (1988-1991) of the Third National Health and Nutrition Examination Survey, which is based on a stratified multistage probability sample to produce nationally representative data for the civilian, non-institutionalized US population. Multivariate hierarchical regressions were used to assess perceived condition of natural teeth in two groups of dentate adults (those with a dental visit during the past 12 months, and those with a less recent dental visit). Self-defined treatment need made a significant, non-trivial contribution after other variables had been controlled. In both subpopulation models, the perception of general health and epidemiological indicators of oral health status were also significant factors. Socio-economic indicators did not contribute significantly in either regression. Understanding components of overall perceptions of oral health moves us closer to understanding oral health behaviors and oral-health-related quality of life.
The Effects of Xylitol-containing Chewing Gums on Dental Plaque and Acidogenic Potential
Authors: Scheie A.Aa. , Fejerskov O. , Danielsen B.
Published: January 2009

The aim of this study was to test the hypothesis that the chewing of xylitol- or xylitol/sorbitol-containing chewing gum reduces plaque formation and the acidogenic potential of dental plaque. Thirty healthy volunteers aged from 19 to 28 yrs were randomly allocated to one of three test groups, chewing either xylitol-, xylitol/sorbitol-, or sucrose-sweetened gums. A three-day plaque accumulation period of no oral hygiene was instituted prior to and at the termination of the chewing gum program, which lasted 33 days. Plaque quantity was assessed on the basis of protein content of individual plaque samples collected by a standardized technique. Acidogenic potential of individual baseline and test plaque samples was assessed by the quantity of various organic acids formed from D-(U-14C)glucose. Identification of extracellular and intracellular metabolites was performed by HPLC. Statistical evaluation of data was performed according to paired comparisons of individual baseline and post-chewing data. Plaque formation, acidogenic potential, and glycolytic profiles were similar at baseline and after the gum-chewing periods. Also, there was no intracellular accumulation of glycolytic metabolites within the plaque bacteria to indicate the inhibition of glycolysis. The study thus leads to the conclusion that, in young adults with low caries experience, exposure of the oral cavity to acceptable doses of xylitol or xylitol and sorbitol has no effect on the microbial deposits on the teeth.
Diphenylhydantoin Affects Glycosaminoglycans and Collagen Production by Human Fibroblasts from Cleft Palate Patients
Authors: Bosi G. , Evangelisti R. , Valeno V. , Carinci F. , Pezzetti F. , Calastrini C. , Bodo M. , Carinci P.
Published: January 2009

During embryonic development, the proper production of extracellular matrix molecules mediates morphogenetic processes involved in palatogenesis. In the present study, we investigated whether any differences exist in glycosaminoglycan (GAG) and collagen synthesis between palate fibroblasts from infants, with or without cleft palate, in two age ranges. Subsequently, the effects of diphenylhydantoin (PHT), a teratogen known to induce cleft palate in human and mammalian newborns, on extracellular matrix (ECM) production were studied. We found that cleft palate fibroblasts (CPFs) synthesize greater amounts of GAG and collagen than normal fibroblasts (NFs). CPFs produced less cellular hyaluronic acid (HA) and more sulphated GAG. HA was the principal GAG species in the medium, and its percentage was lower in one-to three-year-old CPFs. Cleft palate fibroblasts produced more extracellular chondroitin 4- and 6-sulphate (CS) and dermatan sulphate (DS). Associated with a higher production of sulphated GAG, we observed a higher synthesis of type III and type I collagen with a normal ratio of a2(I) to al(I) chains. PHT treatment of NFs reduced collagen and GAG synthesis, with a marked effect on sulphated GAG. The drug changed collagen synthesis, whereas it did not affect GAG production in CPFs whose phenotype may already be impaired. These findings indicate that, in CPFs, modifications in the pattern of ECM components, which are most likely responsible for the anomalous development, persist in infants. In addition, NFs and CPFs with a different phenotype respond differently to PHT treatment.
The Activation and Function of Host Matrix Metalloproteinases in Dentin Matrix Breakdown in Caries Lesions
Authors: Tjäderhane L. , Larjava H. , Sorsa T. , Uitto V.-J. , Larmas M. , Salo T.
Published: January 2009

Matrix metalloproteinases (MMPs) are a family of enzymes which, in concert, are capable of degrading collagen. We investigated whether human MMPs could participate in the degradation of dentin organic matrix after demineralization. We performed Western blot analyses using MMP-specific antibodies to identify MMPs in human dental caries lesions. Enzymography and functional activity assays, with 125I-labeled gelatin as substrate or quantitating the degradation of type I collagen, were used to determine the activity of purified and salivary gelatinolytic (MMP-2 and MMP-9) and collagenolytic (MMP-8) enzymes with and without acid-activation in pHs relevant to caries. Respective analyses were done with caries-related bacteria. We performed electron microscope analyses to assess the degradative activity of sterilized salivary host MMPs on demineralized human dentin. Human MMP-2, MMP-8, and MMP-9 were identified in demineralized dentinal lesions. The latent purified forms of these enzymes were activated at low pH (4.5), followed by neutralization, mimicking the conditions during caries progression. Incubation of human saliva at low pH followed by neutralization resulted in a four-fold increase in the gelatinolytic activity. No gelatinolytic or collagenolytic activity was observed in bacterial samples. The activated enzymes in saliva degraded demineralized dentin organic matrix in vitro. These results demonstrate the pH-dependent activation mechanism of MMPs, which may have a distinct role in different physiological and pathological conditions. They further demonstrate that host MMPs, activated by bacterial acids, have a crucial role in the destruction of dentin by caries.
Effect of Three Months' Frequent Use of Sugar-free Chewing Gum with and without Urea on Calculus Formation
Authors: Fure S. , Lingstrom P. , Birkhed D.
Published: January 2009

Studies on the relationship between gum-chewing and calculus formation have produced contradictory results, and it is not clear whether frequent use of chewing gum promotes or inhibits calculus formation. Also, little is known about whether the addition of a small amount of urea to the chewing gum influences calculus formation. The aim of this investigation was to study the effect of sugar-free chewing gum-with and without urea-on calculus formation and some associated clinical variables. Three three-month periods were studied in a double-blind, crossover design, during which the subjects: (1) chewed 5 pieces/day of a sugar-free, urea-containing chewing gum (20 mg urea/piece); (2) chewed 5 pieces/day of a sugar-free, non-urea-containing gum; or (3) performed no gum-chewing. Twenty-nine persons, all calculus-formers, participated. They were scored for calculus at mesio-lingual, lingual, and disto-lingual sites on the 6 anterior mandibular teeth according to the Volpe-Manhold index. Plaque and gingival bleeding index, stimulated salivary secretion rate and buffer capacity, resting plaque pH, mutans streptococci in saliva and plaque, and lactobacilli in saliva were also determined. No differences in calculus formation were found among the 3 periods. The resting plaque pH was higher after the period with urea-containing gum than after the period with non-urea-containing gum and the no-gum period (p < 0.05). A slight increase in stimulated salivary secretion rate was found after the 2 gum periods (p < 0.05). The plaque and gingival bleeding indices decreased, while resting plaque pH and salivary buffer capacity increased throughout the entire study (p < 0.05). No significant differences in prevalence of the acidogenic micro-organisms were found among the test periods. The main conclusion from this study is that three months' frequent use of sugar-free chewing gum-with or without urea-neither promotes nor inhibits calculus formation.
Emotional Responses Evoked by Dental Odors: An Evaluation from Autonomic Parameters
Authors: Robin O. , Alaoui-Ismaïli O. , Dittmar A. , Vernet-Maury E.
Published: January 2009

Among the factors which could explain avoidance behavior toward dental care, the typical clinging odor of the dental office, due to eugenol, is investigated in this study. The hypothesis is supported by the well-known effects of odorants which may influence cognition, emotion, and behavior. The association between the odor of eugenol and dental fear and anxiety could be explained by the fact that eugenates (eugenol-containing cements) are often used in potentially painful restorative dentistry on vital teeth. The emotional impact of the odors of eugenol and two other dental products (menthol and methyl methacrylate) was evaluated on volunteer subjects through autonomic nervous system (ANS) analysis by recording the variations of six ANS parameters (two electrodermal, two thermovascular, and two cardiorespiratory) induced by the inhalation of the odorants. After the experiment, subjects were asked to fill out an 11-point hedonic scale to rate the pleasantness vs. unpleasantness for each odorant. Results were compared between two groups of subjects divided according to their own dental experience (fearful and non-fearful dental-care subjects). These showed that, in both groups, menthol was rated as pleasant and methyl methacrylate as very unpleasant, whereas eugenol was judged pleasant by non-fearful subjects but unpleasant by fearful subjects. Concerning autonomic analysis, only eugenol induced significantly different patterns of ANS responses between the two groups, with stronger variations for dentally fearful subjects, mainly observed through the electrodermal channel. These results suggest that eugenol can be responsible for different emotional states, depending on the unpleasantness of the subjects' dental experience. This seems to confirm the role of odors as elicitors of emotional memories and to support the possible influence of eugenol odor on the avoidance behavior of some subjects toward dental care.
The Association Between Water-borne Fluoride and Bone Mineral Density in Older Adults
Authors: Phipps K.R. , Orwoll E.S. , Bevan L.
Published: January 2009

While the benefit of fluoridation in the prevention of dental caries has been overwhelmingly substantiated, the effect of fluoride on bone mineral density is less clear. This cross-sectional study was designed to compare the bone mineral densities of older adults exposed to various levels of fluoride from community water systems. Participants were recruited from 3 rural communities with naturally occurring fluoride in their water systems at 0.03, 0.7, and 2.5 mg/L. All adults, age 60 and over, were eligible if they were ambulatory and had a long-term history (≥ 20 yrs) of ingesting city water. Bone mineral density (BMD) was measured by means of dual-energy x-ray absorptiometry at 3 anatomical sites: lumbar spine, proximal femur, and forearm. A total of 353 white non-Hispanic women and 317 white non-Hispanic men took part in the study. When the data were stratified by city of residence and gender, men and women living in the community with high levels of fluoride in their community water system had significantly higher lumbar spine BMD than their counterparts from the communities with low and moderate fluoride levels. The women in the high-fluoride community had significantly higher proximal femur BMD, but there were no statistically significant differences among men in either proximal femur or forearm BMD. Long-term exposure (≥ 20 yrs) to higher levels of fluoride appears to have a positive impact on lumbar spine and proximal femur BMD. Based on the results of this study, exposure to fluoride at levels considered "optimal" for the prevention of dental caries (from 0.7 to 1.2 mg/L) appears to have no significant impact on bone mineral density. The relationship between higher levels of fluoride exposure and bone mineral density requires further investigation.
Edgard C. Moreno, PhD: A Tribute to His Major Contributions to Oral Biology Research
Authors: Margolis Henry C.
Published: January 2009

The seminal contributions of Dr. Edgard C. Moreno to physical chemical aspects of oral biology research are reviewed, with personal insights provided by the author. Dr. Moreno has made major contributions to our understanding of fundamental processes which occur within the oral cavity and which control the formation of mineralized tissues. These contributions include extensive research in the areas of: the chemistry of synthetic calcium phosphates and biominerals, the interaction of salivary proteins and other molecules of biological interest with calcium phosphate surfaces, the mechanism of dental caries formation and the effects of fluoride on this process, the mechanism of dental calculus formation and prevention, and the mechanism of dental enamel formation.
Colonization with Mutans Streptococci and Lactobacilli and the Caries Experience of Children after the Age of Five
Authors: Straetemans M.M.E. , van Loveren C. , de Soet J.J. , de Graaff J. , ten Cate J.M.
Published: January 2009

Some authors suggest that there is a "window of infectivity" for mutans streptococci (MS) at an early age, after which colonization is not likely to occur. Moreover, children with low or non-detectable levels of MS at an early age are at lower risk for caries. It was our aim to study caries experience and colonization with MS and lactobacilli in a group of children at 11 years of age who had been documented to have been MS-free until 5 years of age. For this group, the mfs and MFS values at 11 years of age were found to be 1.12 ± 2.81 and 0.44 ± 0.88, respectively. These values are much lower than those of a control group of 11-year-old children who had always been MS-positive since the age of 2, being 3.10 ± 3.43 and 1.20 ± 1.91, respectively. Of the 30 children without detectable MS up to the age of 5, 22 had acquired MS at 11 years of age, but their MS counts were significantly lower than those of the control group. No correlation was observed between the levels of MS of the children and the mothers. In children at 11 years of age, no differences were found in the numbers of lactobacilli and sugar intakes per week between the children MS-free and the children MS-colonized at 5 years of age. The present study indicates that the acquisition of MS is still possible after the so-called "window of infectivity" and that a delayed acquisition of MS may reduce the caries experi-ence in the primary and permanent dentition at a later age.
Crack Propagation Directions in Unfilled Resins
Authors: Baran G. , Sadeghipour K. , Jayaraman S. , Silage D. , Paul D. , Boberick K.
Published: January 2009

Posterior composite restorative materials undergo accelerated wear in the occlusal contact area, primarily through a fatigue mechanism. To facilitate the timely development of new and improved materials, a predictive wear model is desirable. The objective of this study was to develop a finite element model enabling investigators to predict crack propagation directions in resins used as the matrix material in composites, and to verify these predictions by observing cracks formed during the pin-on-disc wear of a 60:40 BISGMA:TEGDMA resin and an EBPADMA resin. Laser confocal scanning microscopy was used to measure crack locations. Finite element studies were done by means of ABAQUS software, modeling a cylinder sliding on a material with pre-existing surface-breaking cracks. Variables included modulus, cylinder/material friction coefficient, crack face friction, and yield behavior. Experimental results were surprising, since most crack directions were opposite previously published observations. The majority of surface cracks, though initially orthogonal to the surface, changed direction to run 20 to 30° from the horizontal in the direction of indenter movement. Finite element modeling established the importance of subsurface shear stresses, since calculations provided evidence that cracks propagate in the direction of maximum KII(θ), in the same direction as the motion of the indenter, and at an angle of approximately 20°. These findings provide the foundation for a predictive model of sliding wear in unfilled glassy resins.
Circadian Rhythms in the Incorporation and Secretion of 3H-proline by Odontoblasts in Relation to Incremental Lines in Rat Dentin
Authors: Ohtsuka M. , Saeki S. , Igarashi K. , Shinoda H.
Published: January 2009

Circadian incremental lines are universally found in the dentin of animals. They are believed to be caused by functional changes in odontoblasts over 24 hrs. However, the mechanism of rhythmic dentin formation has not yet been elucidated. In the present study, we investigated whether there is a 24-hour rhythm in the collagen-synthetic and secretory activities of odontoblasts by radioautography with 3H-proline as a tracer. Six different groups of rats were injected with 3H-proline at 0000, 0400, 0800, 1200, 1600, or 2000 after the animals had become acclimated to a 12/12-hour light-dark illumination cycle for 2 wks. One hour after the injection, the maxillary incisors were removed and processed for radioautographic study. The silver grains of 3H-proline were most intense over odontoblasts and predentin during the environmental light period, while the nadir occurred during the dark period. The peak value was approximately two-fold higher than the minimum value. Moreover, in the dentin from rats that had been infused with 3H-proline continuously for 10 days by means of osmotic minipumps, silver grains of 3H-proline were heavily distributed over the dark hematoxylin-stained incremental lines. Thus, we demonstrated that odontoblasts show circadian rhythm with regard to collagen synthesis and secretion. These rhythms in odontoblastic function may be responsible for circadian incremental lines in dentin. Key words: circadian rhythm, collagen synthesis, incremental line, odontoblast, radioautography.
Toxicity of Formaldehyde to Human Oral Fibroblasts and Epithelial Cells: Influences of Culture Conditions and Role of Thiol Status
Authors: Nilsson J.A. , Zheng X. , Sundqvist K. , Liu Y. , Atzori L. , Elfwing A. , Arvidson K. , Grafström R.C.
Published: January 2009

The toxicity of formaldehyde, a monomer released from certain polymeric dental materials, was studied in cultured human oral fibroblasts and epithelial cells. The influences of growth conditions were evaluated for both cell types, as well as the role of the internal and external thiol states. A one-hour exposure to formaldehyde decreased the colony-forming efficiency (CFE) of both cell types in a concentration-dependent manner, although the toxicity varied up to 100-fold with the conditions. Clearly, the presence of serum and the thiol cysteine counteracted the toxicity in fibroblasts. Similarly, pituitary extract and cysteine, or a mixture of amino acids and ethanolamines, counteracted the formaldehyde toxicity in serum-free cultures of epithelial cells. In contrast, a growth-promoting surface matrix of fibronectin and collagen did not influence the formaldehyde toxicity, as shown by both the CFE assay and a dye reduction assay. Further, a short-term change to the various growth media per se with or without the supplements serum or cysteine did not significantly alter the CFE. Analysis of the thiol state demonstrated significant differences between epithelial cells and fibroblasts, i.e., comparatively lower cellular levels of the free low-molecular-weight thiols glutathione and cysteine in fibroblasts. This result correlated to significantly higher formaldehyde toxicity in the fibroblasts than in the epithelial cells. Taken together, the results indicated the cytoprotective function of both intracellular and extracellular thiols toward formaldehyde, as well as the usefulness of thiol-free and chemically defined conditions for toxicity assessments in oral epithelial cells and fibroblasts. We conclude that the combined use of a controlled external milieu and the presumed target cell type may be advantageous in evaluations of oral toxicity mechanisms or the toxic potency of dental materials, particularly those which, like formaldehyde, may react with thiols or amines.
Pharmacokinetic and Safety Evaluations of Ketoprofen Gels in Subjects with Adult Periodontitis
Authors: Lawrence H.P. , Paquette D.W. , Smith P.C. , Maynor G. , Wilder R. , Mann G.L. , Binder T. , Troullos E. , Annett M. , Friedman M. , Offenbacher S.
Published: January 2009

This clinical trial used a randomized, partially double-blind, controlled parallel design to evaluate the pharmacokinetics and safety of the NSAID, ketoprofen (KTP), in gel formulations. Forty-two subjects, ages 35 to 57 years, with generalized, moderate to advanced adult periodontitis were recruited and randomized to one of 5 treatments over a 14½-day treatment period: (1) 0.5% KTP gel; (2) 1.0% KTP gel; (3) 1.0% KTP alternate gel; (4) 2.0% KTP gel; and (5) 25 mg KTP capsule (positive control). Plasma samples were obtained on days 1 (pre-dosing, 0.5, 1, 2, 3, 6 hr), 8 (pre-dosing, 2 hr), 15 (pre-dosing, 2 hr), and 22 (7 days post-treatment). Plasma KTP concentrations were determined by means of high-performance liquid chromatography. Significant differences in mean area under the plasma concentration vs. time curve (AUC0-∞ ) among the groups were detected (p < 0.001), with the 25 mg p.o. capsule exhibiting the largest value (5054 ng-hr/mL), the 2.0% gel exhibiting an intermediate value (2244 ng-hr/mL), the 1.0% gels exhibiting lower but comparable values (1516 for the alternate formulation vs. 1461 ng-hr/mL), and the 0.5%. gel showing the lowest value (736 ng-hr/mL). Significant differences in dose- and weight-adjusted maximum plasma concentration (Cmax/dose/kg) were detected overall such that the 25 mg p.o. capsule demonstrated higher values as compared with the 4 gel formulations (p = 0.001). The 5 treatments exhibited similar mean times of maximum plasma concentration (tmax) values ranging from 0.6 to 1 hr. Systemic exposures relative to dose and body weight were lower for the gel formulations than for the capsule. The relative systemic bioavailability of the gels compared with peroral administration ranged from 54% to 69%.
Abnormally High Levels of Cystatin S in Submandibular Glands, Saliva, and Gingiva of Plaque-resistant Rats
Authors: Abe K. , Okina A. , Yano T. , Gao C. , Ohmori H. , Ishibashi K. , Nishiura T. , Letic-Gavrilovic A.
Published: January 2009

To identify salivary biomarkers of periodontal diseases, we used plaque-resistant and -susceptible rats as animal models. The levels of salivary cystatin S in saliva, salivary glands, and gingiva were tested in Nembutal-anesthetized young and adult plaque-resistant and -susceptible rats of both sexes with and without chronic treatment with isoproterenol. Isoproterenol was injected i.p. once a day for 4 or 6 consecutive days. Isoelectric focusing electrophoresis by the PhastSystem and the Western blotting method were used to separate different proteins and to identify a salivary cystatin S band in these samples. The expression of salivary cystatin S mRNA was also determined by the Northern blotting method. Depending upon the types of agonists, a few differences were observed in secretory functions between both strains of rats in both sexes, but the levels of salivary cystatin S in saliva elicited from the submandibular gland and in the extracts of the submandibular glands and gingiva were significantly higher in plaque-resistant rats when compared with those of plaque-susceptible rats in both sexes. However, no significant difference was seen between the strains after chronic treatment with isoproterenol. The N-terminal 26-amino-acid sequence of salivary cystatin S purified from submandibular saliva of plaque-resistant rats was identical with that purified from submandibular saliva of Sprague-Dawley rats subjected to chronic treatment with isoproterenol. The expression of salivary cystatin S mRNA was dramatic in the submandibular glands of the plaque-resistant rats and in the submandibular glands of Wistar rats subjected to chronic treatment with isoproterenol, but not in those of plaque-susceptible rats. These results suggest that salivary cystatin S might be a good biomarker in distinguishing between the two strains of rats and that its concentration is correlated with plaque resistance.
Developmental Changes in Enzyme Activities and in Structural Features of Rat Masticatory Muscle Mitochondria
Authors: Sato I. , Konishi K. , Kuramochi T. , Sato T.
Published: January 2009

The functional ability of a muscle is closely related to the activities of the mitochondria, which are energy-producing organelles in muscle cells. The development of the mammalian masticatory muscle progresses dramatically when feeding behavior changes from suckling to mastication, but it is unclear how the energy-producing systems of the mitochondria change. In this paper, the development of rat masticatory muscle mitochondria was investigated in terms of enzyme activities of the mitochondrial respiratory chain and the structural and numerical development of mitochondria, especially regarding the change in feeding behavior from suckling to mastication. Using isolated mitochondria from the masticatory muscle, we measured succinate dehydrogenase, NADH dehydrogenase, succinate-O2 oxidoreductase, and NADH-O 2 oxidoreductase. These were found to be increased in the 15-day postnatal rat compared with the 0-to 10-day postnatal rat. The structural development of mitochondria was gradual in the 0- to 15-day postnatal rat. However, a notable increase was found in the cross-sectional area of mitochondria between 10 and 15 days postnatally. The number of mitochondria per muscle fiber was apparently constant during the same period. We demonstrated that the change in feeding behavior was well-correlated with an increase in mitochondrial enzyme activity, also supported by the early structural development of mitochondria.
Food Properties that Influence Neuromuscular Activity During Human Mastication
Authors: Agrawal K.R. , Lucas P.W. , Bruce I.C. , Prinz J.F.
Published: January 2009

The rate of breakdown of food in mastication depends on the ratio of two mechanical properties of the food-the toughness and modulus of elasticity (Agrawal et al., 1997)-a result which can be predicted by an analysis of the energetics of fracture. The work input to produce food fragmentation is provided by the masticatory muscles, the activity levels of which depend on sensory feedback from the mouth. Here, we test the hypothesis that the activity of a representative of this musculature is modulated by the above combination of food properties. The surface electrical activity (EMG) of the anterior temporalis muscles of ten human subjects was recorded while subjects chewed standardized volumes of 15 food types. The integrated EMG in these muscles was highly significantly related to the square root of the ratio of the above two food properties. Significant correlations were found between this food property index and integrated EMG, both when data for all chews and all subjects were lumped together (r = -0.86; p < 0.0001) and when correlation coefficients between the index and EMG were plotted for each chew made by each subject. Except for two subjects in the first chew, these coefficients reached and maintained highly significant levels throughout the masticatory sequence. Thus, a clear relationship between the electrical activity of a jaw-closing muscle and the mechanical properties of food has been found for the first time.
Heteronymous H-reflex in Temporal Muscle Motor Units
Authors: Macaluso G.M. , Pavesi G. , De Laat A.
Published: January 2009

An electric stimulation of the masseteric nerve elicits a heteronymous H-reflex in the temporal muscle. The characteristics of this reflex response were investigated by analysis of the firing probability changes of single motor units. Eleven healthy subjects participated in the experiments. The heteronymous H-reflex of the temporal muscle was electrically elicited by stimulation of the masseteric nerve at 120% of the intensity needed for the maximal masseteric M-wave. From 8 to 24 motor units were sampled from the temporal muscle of each subject. Peri-stimulus time histograms of motor unit recordings were built with a 0.5-ms bin width. The mean firing probability was calculated for the 20 ms preceding the stimulus. The firing probability was considered increased when it exceeded the mean by 3 standard deviations. Of 104 sampled motor units, 40 motor units showed a significant increase of the firing probability, which lasted 1 ms or less in 29 of them. In 12 out of 16 motor units, a significant increase of firing probability also persisted at a lower stimulation intensity (120% of the threshold needed to elicit a masseteric M wave). These data indicate that: (1) some temporal muscle motor units are modulated by afferents from the masseter muscle, (2) the heteronymous H-reflex has a monosynaptic component, and (3) there might be a more complex than just monosynaptic organization serving the heteronymous temporal H-reflex. For the latter conclusion regarding synaptic wiring, however, PSTH studies like the present one can offer only indirect evidence, and this question could be better studied in animals.
Continuous Administration of Basic Fibroblast Growth Factor (FGF-2) Accelerates Bone Induction on Rat Calvaria— An Application of a New Drug Delivery System
Authors: Kimoto T. , Hosokawa R. , Kubo T. , Maeda M. , Sano A. , Akagawa Y.
Published: January 2009

Some studies have shown that locally applied basic fibroblast growth factor (FGF-2) enhances bone regeneration at a fracture site, while others have not been in agreement. We developed a new continuous FGF-2 delivery system designed to accelerate cytokine-induced new bone formation. A subperiosteal pocket was surgically formed in 36 eight-week-old male Wistar rats. The rats were administered 0, 1, 10, or 100 ng of FGF-2 contained in a collagen minipellet, mixed with allogeneic demineralized bone matrix in a dome-shaped Millipore® filter and then placed into the pocket. New bone formation in the dome was evaluated at 2, 4, and 8 wks after placement. Soft x-ray radiographs disclosed an apparently larger radiopaque region in the 1-ng group at 4 wks compared with those in the other groups. Morphometrical analysis revealed that the new bone area in the 1-g group was significantly larger than that in the 0-g group (p < 0.01). In the 100-ng FGF-2 group, new bone formation seemed suppressed. We concluded that continuous slow administration of a small amount of FGF-2 accelerates bone-derived osteogenic cytokine-induced new bone formation.
Cloning, Characterization, and Tissue Expression Pattern of Mouse Tuftelin cDNA
Authors: MacDougall M. , Simmons D. , Dodds A. , Knight C. , Luan X. , Zeichner-David M. , Zhang C. , Ryu O.H. , Qian Q. , Simmer J.P. , Hu C.-C.
Published: January 2009

Tuftelin is a protein that has been suggested to function during enamel crystal nucleation. Published sequences for bovine tuftelin cDNA and genomic clones proposed different reading frames that radically affected the derived amino acid sequence of the tuftelin carboxyl-terminus. We have isolated and characterized a full-length mouse cDNA clone and a partial porcine cDNA clone that include the region of the proposed frame-shift. The mouse tuftelin clone is 2572 nucleotides in length, exclusive of the poly(A+) tail. Translation from the 5'-most ATG yields a protein of 390 amino acids with an isotope-averaged molecular mass of 44.6 kDa and an isoelectric point of 5.9. Comparison of the bovine, mouse, and porcine cDNAs supports the revised bovine tuftelin amino acid sequence and suggests that the bovine tuftelin translation initiation codon be re-assigned to a more 5' ATG. Re-assigning the translation initiation codon lengthens the tuftelin protein by 52 amino acids, 51 of which are identical between bovine and mouse. At the carboxyl-terminus, the revised bovine and the mouse sequences match at 39 of the final 42 amino acid positions, compared with 2 identities with the originally published bovine reading frame. Northern blot analysis reveals that tuftelin is not ameloblast-specific but is expressed in multiple tissues, including kidney, lung, liver, and testis. Two tuftelin RNA messages, of 2.6 and 3.2 kb, were detected. DNA sequence characterization of an RT-PCR amplification product confirmed expression of tuftelin in kidney, and identified an alternatively spliced mouse tuftelin mRNA lacking exon 2.
Adenomatous Polyposis Coli Protein is Expressed in Alternate Stages of the Ameloblast Life Cycle
Authors: Wang M. , Dobeck J.M. , Sorkin B.C. , Skobe Z.
Published: January 2009

Mutations of the adenomatous polyposis coli gene protein (APC) are associated with familial polyposis and also sporadic colon adenomas, both preconditions to cancer formation. Some familial polyposis patients also develop Gardner's syndrome, a condition characterized by supernumerary teeth, mandibular osteomas, and other maladies. We investigated participation of APC in normal tooth development. Using a monoclonal antibody to study APC expression in the forming rat incisor, we found no APC staining in differentiating ameloblasts, then strong staining in secreting ameloblasts and stratum intermedium cells, followed by cells in the transition stage which did not stain. Intense APC staining resumes in maturation-stage ameloblasts and proximal papillary cells. APC staining disappears again in reduced ameloblasts at the conclusion of amelogenesis. APC staining was not seen in any other odontogenic cells. We report a unique system in which APC expresssion is upregulated and downregulated twice during the normal life cycle of ameloblasts. APC, therefore, is important in the normal maturation of both colonic epithelium and odontogenic epithelium. At this point, we cannot rule out any of the known functions of APC, which include: modulation of cell adhesion by binding to catenin, regulation of β-catenin as a differentiative signaling molecule, and promotion of microtubule assembly. In this respect, the rat incisor enamel organ provides a unique tissue for studying the regulation and functions of APC.
Indentation Creep Behavior of a Direct-filling Silver Alternative to Amalgam
Authors: Xu H.H.K. , Liao H. , Eichmiller F.C.
Published: January 2009

Amalgam creep has been identified as a key parameter associated with marginal breakdown and corrosion. The aim of this study was to evaluate the time-dependent deformation (creep) of a novel silver filling material as an alternative to amalgam. We made the silver specimens by pressing a precipitated powder at room temperature to a density that can be achieved in clinical hand consolidation. The surface of the silver was either polished or burnished. To examine local contact creep and the effect of surface finishing, we used an indentation creep method in which a Vickers indenter was loaded on the specimen surface at a load of 10 N with dwell times of 5 sec to 6 x 104 sec. We used a bonded-interface technique to examine subsurface creep mechanisms. The flexural strength (mean ± SD; n = 10) was 86 ± 20 MPa for amalgam, 180 ± 21 MPa for polished silver, and 209 ± 19 MPa for burnished silver-values which are significantly different from each other (family confidence coefficient = 0.95; Tukey's multiple-comparison test). Indentation creep manifested as hardness number decreasing with increased dwell time. With dwell time increasing from 5 sec to 6 x 104 sec, the hardness number of amalgam was reduced by approximately 80%; that of the polished silver and the burnished silver was reduced by only 40%. Subsurface creep in amalgam consisted of the shape change of the alloy particles from spherical to elongated shapes, and the separation of matrix grains from each other, possibly due to grain-boundary sliding. Creep of the polished silver occurred by densification reducing porosity and increasing hardness; that of the burnished silver occurred by the displacement of the burnished layer. These results suggest that, due to creep-induced subsurface work-hardening and densification, the consolidated silver exhibits a higher resistance to indentation creep than does amalgam. The hardness number of silver approaches that of amalgam after prolonged indentation loading.
Surface Chemistry of a High-copper Dental Amalgam
Authors: McDermott A.J. , Kothari S. , Short R.D. , van Noort R. , Alexander M.R.
Published: January 2009

In amalgam, mercury is intended to take the form of stable intermetallic compounds. Any mercury leakage must therefore come from free mercury not involved in such compounds. Thus, a knowledge of the exact surface chemistry of dental amalgam is necessary if this phenomenon is to be understood. From XPS and EDS analyses, a model of the surface chemistry of amalgam is proposed which fully characterizes all the phases that are present. The data show the surface to have a composition different from that of the bulk, being comprised of a hydrocarbon deposit and adsorbed water covering the intermetallic phase γ2 (Sn6-8Hg), tin (iv) oxide, and mercury in a free state. After amalgamation, the amount of mercury at the surface decreases with time and eventually attains a constant concentration, where it is all involved in the γ2 phase, leaving no free mercury. A model is proposed for the surface of amalgam and the changes in this model with time.
Expression of Collagen α1(I) mRNA Variants during Tooth and Bone Formation in the Rat
Authors: Brandsten C. , Lundmark C. , Chritersson C. , Hammarström L. , Wurtz T.
Published: January 2009

Collagen al(I) mRNA is composed of two variants of 5 and 6 kb, differing in the length of the 3' untranslated region. In this work, the nucleotide sequences of the two rat mRNA variants were compared, and their expression pattern in cells forming bone, dentin, and cementum were analyzed. The sequences were determined from cDNA inserts of tooth and bone libraries plus directly from PCR fragments, obtained from bone. A total of 5721 bases of the rat collagen α1(I) sequence from cDNA of tooth and bone was determined. All sequences of the short variant were represented in the long variant. Only the alternatively poly-A additions gave rise to the variants in hard tissue. Two oligonucleotides were chosen as probes, one of which recognized, on Northern blots, the two bands of 5 and 6 kb, and the other the 6-kb variant only. The oligonucleotides were used in in situ hybridization experiments, for study of the distribution of the variants in different extracellular matrix-forming cells. Osteoblasts, odontoblasts, and cementum-associated cells were closely examined in sections from rat maxillae from 2 to 25 days of age. A similar or identical pattern of mRNA expression was observed with both oligonucleotides, indicating that the two mRNA variants were co-expressed in all cases.
Aberrant Gene Expression in Epithelial Cells of Mixed Odontogenic Tumors
Authors: Papagerakis P. , Peuchmaur M. , Hotton D. , Ferkdadji L. , Delmas P. , Sasaki S. , Tagaki T. , Berdal A.
Published: January 2009

Comparative investigations of odontogenic cells in normally forming teeth and tumors may provide insights into the mechanisms of the differentiation process. The present study is devoted to late phenotypic markers of ameloblast and odontoblast cells, i.e., proteins involved in biomineralization. The in situ expression of amelogenins, keratins, collagens type III and IV, vimentin, fibronectin, osteonectin, and osteocalcin was performed on normal and tumor odontogenic human cells. The pattern of protein expression showed some similarities between ameloblasts and odontoblasts present in normally developing human teeth and cells present in neoplastic tissues of ameloblastic fibroma, ameloblastic fibro-odontomas, and complex odontomas. Amelogenins (for ameloblasts) and osteocalcin (for odontoblasts) were detected in cells with well-organized enamel and dentin, respectively. In contrast, "mixed" cells located in epithelial zones of mixed odontogenic tumors co-expressed amelogenins and osteocalcin, as shown by immunostaining. The presence of osteocalcin transcripts was also demonstrated by in situ hybridization in these cells. Keratins and vimentin were detected in the same epithelial zones. Tumor epithelial cells were associated with various amounts of polymorphic matrix (amelogenin- and osteocalcin-immunoreactive), depending on the types of mixed tumors. No osteocalcin labeling was found in epithelial tumors. This study confirms that the differentiation of normal and tumor odontogenic cells is accompanied by the expression of some common molecules. Furthermore, the gene products present in normal mesenchymal cells were also shown in odontogenic tumor epithelium. These data may be related to a tumor-specific overexpression of the corresponding genes transcribed at an undetectable level during normal development and/or to an epithelial-mesenchymal transition proposed to occur during normal root formation. A plausible explanation for the results is that the odontogenic tumor epithelial cells are recapitulating genetic programs expressed during normal odontogenesis, but the tumor cells demonstrate abnormal expression patterns for these genes.
The Theoretical Optimal Center of Rotation for a Temporomandibular Joint Prosthesis: A Three-dimensional Kinematic Study
Authors: van Loon J.-P. , Falkenström C.H. , de Bont L.G.M. , Verkerke G.J. , Stegenga B.
Published: January 2009

A unilateral temporomandibular joint (TMJ) prosthesis may cause dysfunction of the contralateral, natural TMJ because of lack of translatorial movements of the prosthetic side. The natural translatorial capacity of the mandible can be restored in part by a TMJ prosthesis with a fixed center of rotation (CR), positioned inferiorly to the center of the natural mandibular condyle. The aim of this study was to determine the optimal position for the fixed CR of a unilateral TMJ prosthesis. A mathematical model was used to analyze different positions of the CR. These positions were evaluated based on the calculated rotation of the mandible in the frontal (θf) and horizontal (θh) plane, and the mediolateral movement (MLM) of the contralateral natural condyle. For current TMJ prostheses, with the CR positioned in the center of the natural condyle, 6h exceeded the natural limits. When the CR was shifted inferiorly, all parameters improved, particularly θh. The addition of an anterior shift to an inferior shift slightly worsened θf, while the addition of a posterior shift to an inferior shift slightly improved θf and worsened MLM. We concluded that the functioning of the contralateral TMJ improves by shifting the CR inferiorly. An anterior shift may be added to remain within the contour of the mandibular ramus. The proposed position of the CR is 15 mm inferior to the center of the natural condyle, combined, if necessary, with an additional anterior shift of 5 mm.
Origin of Primary Sensory Neurons Innervating the Buccal Stretch Receptor
Authors: Yamamoto T. , Onozuka M. , Nagasaki S. , Watanabe K. , Ozono S.
Published: January 2009

The primary sensory neurons innervating mechanoreceptors in oro-facial regions have their cell bodies in either the trigeminal ganglion or the mesencephalic nucleus of the trigeminal nerve. The buccal stretch receptor (BSR), a type of mechanoreceptor in the jaw of rodents, has recently been recognized as signaling the position of the mandible. The location of the primary afferent neurons innervating this receptor is unknown. To investigate the cell bodies of the BSR afferent neurons in rats, we applied wheat germ agglutinin-horseradish peroxidase (WGA-HRP) to the proximal stump of the severed nerve branch of the buccal nerve that supplied the BSR. HRP-labeled cell bodies were observed in the posterolateral portion of the ipsilateral trigeminal ganglion. None was found in the contralateral trigeminal ganglion or in the brainstem. All labeled cell bodies were oval or round and closely resembled pseudo-unipolar neurons. The mean diameter of the labeled somata ranged between 25.5 and 52.5 μm, with small (≤ 30 μm), medium (from 31 to 40 μm), and large somata (≥ 41 μm) accounting for 8.8%, 54.9%, and 36.3%, respectively. Among the myelinated nerve fibers in the branch in which WGA-HRP was applied, 78.5% terminated in the BSR and had larger fiber diameters than the rest, indicating that most of the medium and large HRP-labeled cell bodies were BSR afferents. From these results and the ontogenetic origin of this receptor, it is suggested that the BSR differentiated from the mechanoreceptors in the oral mucosa or the fascia of masticatory muscles.