bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of Linkage in a Hispanic Cohort with a Class III Dentofacial Phenotype
Authors: Frazier-Bowers S. , Rincon-Rodriguez R. , Zhou J. , Alexander K. , Lange E.
Published: January 2009

Despite the prevalence of craniofacial disorders, the genetic contribution remains poorly understood. Class III malocclusion represents a specific craniofacial problem that can be handicapping, both functionally and socially. We hypothesized that the Class III phenotype is genetically linked to specific loci that regulate maxillary or mandibular growth. To determine the region linked to the Class III phenotype in four Hispanic families, we performed a genome-wide scan and linkage analysis using 500 microsatellite markers. Pedigree and linkage analyses revealed that the Class III phenotype (primarily maxillary deficiency) segregates in an autosomal-dominant manner, and that 5 loci (1p22.1, 3q26.2, 11q22, 12q13.13, and 12q23) are suggestive of linkage. Candidate genes within the 12q23 region (ZLR=2.93) include IGF1, HOXC, and COL2A1. Chromosome 1 results (ZLR=2.92) were similar to those reported previously in an Asian cohort with mandibular prognathism, suggesting that a common upstream genetic element may be responsible for both mandibular prognathism and maxillary deficiency.
Biological Mechanisms in Palatogenesis and Cleft Palate
Authors: Meng L. , Bian Z. , Torensma R. , Von den Hoff J.W.
Published: January 2009

Clefts of the palate are common birth defects requiring extensive treatment. They appear to be caused by multiple genetic and environmental factors during palatogenesis. This may result in local changes in growth factors, extracellular matrix (ECM), and cell adhesion molecules. Several clefting factors have been implicated by studies in mouse models, while some of these have also been confirmed by genetic screening in humans. Here, we discuss several knockout mouse models to examine the role of specific genes in cleft formation. The cleft is ultimately caused by interference with shelf elevation, attachment, or fusion. Shelf elevation is brought about by mesenchymal proliferation and changes in the ECM induced by growth factors such as TGF-βs. Crucial ECM molecules are collagens, proteoglycans, and glycosaminoglycans. Shelf attachment depends on specific differentiation of the epithelium involving TGF-β3, sonic hedgehog, and WNT signaling, and correct expression of epithelial adhesion molecules such as E-cadherin. The final fusion requires epithelial apoptosis and epithelium-to-mesenchyme transformation regulated by TGF-β and WNT proteins. Other factors may interact with these signaling pathways and contribute to clefting. Normalization of the biological mechanisms regulating palatogenesis in susceptible fetuses is expected to contribute to cleft prevention.
The Microbiota of Acute Apical Abscesses
Authors: Siqueira J.F. , Rôças I.N.
Published: January 2009

As the breadth of bacterial diversity in the oral cavity has been deciphered by molecular studies, several newly identified species/phylotypes have emerged as potential pathogens. We hypothesized that many of these species/phylotypes could also be involved with the etiology of endodontic abscesses. Abscess aspirates from 42 persons were analyzed for the presence of 81 species/phylotypes by means of a reverse-capture checkerboard hybridization assay. Associations between the most frequently detected taxa were calculated. The most prevalent taxa were Fusobacterium nucleatum, Parvimonas micra, and Porphyromonas endodontalis. Other frequently found taxa included Olsenella uli, streptococci, Eikenella corrodens, some as-yet-uncultivated phylotypes ( Bacteroidetes clone X083 and Synergistes clone BA121), and newly named species ( Prevotella baroniae and Dialister invisus). Several positive bacterial associations were disclosed. Findings not only strengthen the association of many cultivable species with abscesses, but also include some newly named species and uncultivated phylotypes in the set of candidate pathogens associated with this disease.
A Novel Mutation in the DSPP Gene Associated with Dentinogenesis Imperfecta Type II
Authors: Lee S.-K. , Lee K.-E. , Jeon D. , Lee G. , Lee H. , Shin C.-U. , Jung Y.-J. , Lee S.-H. , Hahn S.-H. , Kim J.-W.
Published: January 2009

Hereditary dentin defects are divided into dentinogenesis imperfecta and dentin dysplasia. We identified a family segregating severe dentinogenesis imperfecta. The kindred spanned four generations and showed an autosomal-dominant pattern of inheritance. The proband was a child presenting with a severely affected primary dentition, with wide-open pulp chambers and multiple pulp exposures, resembling a DGI type III (DGI-III) pattern. We hypothesized that a mutation in the DSPP gene is responsible for this severe phenotype. Mutational analyses revealed a novel mutation (c.53T>A, p.V18D) near the intron-exon boundary in the third exon of the DSPP gene. We analyzed the effect of the mutation by means of an in vitro splicing assay, which revealed that the mutation did not affect pre-mRNA splicing. Further studies are needed for a better understanding of the nature of the disease and the development of an appropriate treatment strategy.
The Boy with the Golden Tooth: A 1593 Case Report of the First Molded Gold Crown
Authors: Spielman A.I.
Published: January 2009

The case of the Boy with the Golden Tooth, a “miracle” in a remote village in Silesia, in what is today southwestern Poland, was reported extensively in 1593. Here we report that the hoax, perpetrated by someone close to the family and with knowledge of goldsmith techniques, is the first documented case of the use of a molded gold crown. Using period instruments available to goldsmiths and a 0.001” copper sheet, we reproduced, on a plastic pediatric model, what the gold crown could have looked like.
Temporal and Spatial Expressions of Type XII Collagen in the Remodeling Periodontal Ligament during Experimental Tooth Movement
Authors: Karimbux N.Y. , Nishimura I.
Published: January 2009

This study tested the hypothesis that the remodeling processes of adult periodontal ligament (PDL) reiterate the cellular and molecular events that occur sequentially during development. Type XII collagen has been implicated in the three-dimensional organization of the PDL extracellular matrix, and its expression has been restricted to the terminally differentiated stages. This study focused on the examination of the temporal and spatial expression of type XII collagen during experimental PDL remodeling in the rat. The temporal expressions of types I and XII collagen mRNAs were examined by RNA transfer blot and RNase protection assays, respectively, and were found to be relatively stable in the control group throughout the experimental period. In the tooth movement group, the expression of type I collagen increased at 72 hours and sustained the high level of expression at one week, while an increase in the expression of type XII collagen was first noted at the one-week period. The temporal activation of types I and XII collagen expression in the remodeling occurred in a pattern similar to that found during the development of the PDL. The spatial expression of type XII collagen mRNA was examined by in situ hybridization in the one-week-tooth-movement specimens. Labeled cells, which were more evident in the tension side, typically exhibited a spindle shape and were surrounded by the mature PDL matrix. Our data suggest that the type XII collagen expression may be closely associated with the functional regeneration of the PDL.
Phenytoin at Micromolar Concentrations is an Osteogenic Agent for Human-mandible-derived Bone Cells in vitro
Authors: Nakade O. , Baylink D.J. , Lau K.-H.W.
Published: January 2009

The present study sought to test the hypothesis that phenytoin acts on normal human-mandible-derived bone cells to induce osteogenic effects. To test the effects of phenytoin on bone cell proliferation, we measured [3H]-thymidine incorporation into cell DNA during the final four hr of a 24-hour incubation with phenytoin. Phenytoin at micromolar concentrations significantly stimulated the [3H]-thymidine incorporation in a dose-dependent, biphasic, manner with a maximal effect at from 10 to 50 uM. We confirmed the proliferative effect of phenytoin by counting cell number. To evaluate the effects of phenytoin on osteoblastic differentiation, we determined alkaline-phosphatase specific activity and found that phenytoin at micromolar concentrations significantly increased that activity in a dose-dependent manner, with maximal stimulation at approximately 1 μM. To investigate the effects of phenytoin on mature osteoblastic activities, we measured de novo collagen synthesis and osteocalcin secretion. Mitogenic doses of phenytoin significantly increased collagen synthesis and osteocalcin secretion in a dose-dependent, biphasic, manner, with the maximal stimulatory dose at from 5 to 10 uM. In summary, phenytoin at micromolar ranges increased (a) [3H]-thymidine incorporation and cell number, (b) alkaline-phosphatase specific activity, (c) collagen synthesis, and (d) osteocalcin secretion in monolayer cultures of normal human-mandible-derived bone cells. These observations are consistent with the premise that low doses of phenytoin act on human craniofacial bone cells to stimulate cell proliferation, differentiation, and mature osteoblastic activities to stimulate bone formation.
Phosphorus Magnetic Resonance Spectroscopy of Human Masseter Muscle
Authors: Plesh O. , Meyerhoff D.J. , Weiner M.W.
Published: January 2009

Masseter muscle metabolism is poorly understood. 31P Magnetic Resonance Spectroscopy (MRS) provides an opportunity for non-invasive study of muscle metabolism during rest, exercise, and recovery. The aim of this study was to investigate the changes in high-energy phosphates and pH in human masseter muscle associated with exertional pain. Phosphates and pH were measured with 31P Magnetic Resonance at 2.0 Tesla. The bite force was simultaneously measured with a force transducer. Continuous biting at maximum voluntary bite force (MVBF) and two intermittent biting exercises with different duty cycles were performed to pain intolerance. The light intermittent exercise did not produce pain. Brief MVBF requested at the beginning, during, and end of each exercise showed no decay. Qualitatively, changes in phosphates were similar to those reported from comparable limb muscle exercises: increased inorganic phosphate (Pi), decreased phosphocreatine (PCr), and no changes in ATP level. Quantitatively, however, the Pi/PCr ratio did not reach the levels reported in limb muscles during similar exercises. Also, the pH changed very little. Thus, the lack of fatigue was no surprise, since the level of changes in Pi/PCr and pH, reported to be associated with fatigue in limb muscles, was far less in the masseter. Pain development toward the end of the heavy exercises prevented further depletion of metabolites. Thus, the lack of fatigue generally postulated for the masseter muscle may not be due to resistance to fatigue of these fibers, but rather to the presence of pain preventing the fatigue. However, no specific metabolic changes associated with exertional pain were found.
Characterization of Low-molecular-weight Peptides in Human Parotid Saliva
Authors: Perinpanayagam H.E.R. , VanWuyckhuyse B.C. , Ji Z.S. , Tabak L.A.
Published: January 2009

The low-molecular-weight components of human saliva remain poorly characterized. Therefore, low-molecular-weight peptides (Mr < 3000) have been purified from human parotid saliva and characterized with respect to their amino acid sequence. From the sequences obtained, it is likely that these peptides are derived from proteolysis of the hydroxyapatite-interactive human salivary proteins, histatins, proline-rich proteins, and statherins. Since human parotid saliva is an amicrobial fluid, much of the low-molecular-weight peptide fraction of this secretion appears to be derived from the proteolytic processing of the larger proteins. Because of their small size, these peptides are likely to be in exchange with dental plaque fluid and may therefore help modulate events such as demineralization/remineralization, microbial attachment, and dental plaque metabolism at the tooth-saliva interface.
Binding of Human High-molecular-weight Salivary Mucins (MG1) to Hemophilus parainfluenzae
Authors: Veerman E.C.I. , Ligtenberg A.J.M. , Schenkels L.C.P.M. , Walgreen-Weterings E. , Nieuw Amerongen A.V.
Published: January 2009

In human saliva, two different mucin populations can be distinguished, viz., high-molecular-weight mucins (MG1, mol. wt > 1 x 106) and low-molecular-weight mucins (MG2, mol. wt -125 kD). The carbohydrate moiety of MG1 displays a wide spectrum of oligosaccharide structures, varying in composition, length, branching, and acidity. The biological significance of the heterogeneity in carbohydrate structures of mucins is unclear. The present investigation focused on the question whether MG1, because of its diverse carbohydrate side-chain population, can bind to a large variety of oral micro-organisms. A replica plate technique, in combination with immunochemical detection with monoclonal antibodies against MG1, was used to screen in vivo human oral microflora for the presence of micro-organisms which could bind the high-molecular-weight salivary mucin MG1. Binding to purified MG1 was established for Hemophilus (para)influenzae species, whereas other species, including Streptococcus and Staphylococcus, were negative. MG1 binding to Hemophilus parainfluenzae could be abolished by protease treatment of MG1. In contrast, periodate acid treatment, partial deglycosylation, or addition of monosaccharides did not affect MG1 binding to H. parainfluenzae, indicating that MG1 carbohydrate side-chains were not directly involved in the binding. The binding was pH-dependent, showing an increase when the pH was lowered from 8.0 to 4.0. These data indicate that MG1 can be bound in a selective manner by Hemophilus spp. and suggest that the 'naked' unglycosylated polypeptide moiety of MG1 is involved in its binding to Hemophilus parainfluenzae.
Tooth Color and Reflectance as Related to Light Scattering and Enamel Hardness
Authors: ten Bosch J.J. , Coops J.C.
Published: January 2009

Tooth color is determined by the paths of light inside the tooth and absorption along these paths. This paper tests the hypothesis that, since the paths are determined by scattering, a relation between color and scattering coefficients exists. One hundred and two extracted incisors were fixed in formalin, mounted in a standardized position in brass holders, and pumiced. A facet was prepared near the incisal edge on the labial plane to allow for Knoop hardness measurements with a 500-gram load. Light scattering by the enamel was measured in a 45°/0° geometry; light scattering by both enamel and dentin was measured in a 0°/0° geometry. The reflection spectrum of the tooth was measured from the labial plane with a spectroradiometer in a 45°/0° geometry, with standard illuminant A and standard illuminant D65. To include all volume-reflected light, we used entire-tooth illumination and small-area measurement. CIELAB color coordinates were calculated from the spectra. Neither spectra nor coordinates showed evidence of a contribution of fluorescence to tooth color. Averaged values and standard deviations for L*,a*,b* were 69.9 (4.1), 1.22 (1.4), and 17.9 (2.9), respectively. Both scattering coefficients averaged to 0.6 (0.4) mm-1; Knoop hardness number was, on average, 271 (39) kg/mm 2. L* correlated with a* (r = -0.51), with the enamel scattering coefficient (r = 0.60), and slightly with hardness (r = 0.17, p = 0.03). The colors of 28 teeth from which the enamel was removed correlated strongly with the colors of the complete tooth. This study quantitatively confirms that tooth color is determined mainly by dentin, with enamel playing only a minor role through scattering at wavelengths in the blue range.
Effects of Treatment and Storage Conditions on Ceramic/Composite Bond Strength
Authors: Roulet J.F. , Söderholm K.J.M. , Longmate J.
Published: January 2009

During the past few years, the interest in using ceramic inlays and veneers has increased. New materials and methods have been introduced to bond these restorations to resinous materials. Since our knowledge of how to optimize such bonding is limited, the objective of this study was to test the hypothesis that various surface treatment variables and combinations of these variables affect the strength of the ceramic/composite interphase of ceramic inlays differently. The influences of material composition, surface-roughening method, silane treatment, silane heat treatment, and storage condition on bond strength were investigated. Three ceramics (Dicor®, Mirage®, Vitabloc®), three surface-roughening methods (etching, sandblasting, grinding), three silane treatments (γ-methacryloxypropyltrimethoxysilane [MPS], MPS + paratoluidine, vinyltrichlorosilane), two heat treatments (20°C for 60 s, 100°C for 60 s), and two storage conditions (24-hour dry, one yr in water at 37°C) were studied. For each of the 108 combinations, five specimens were tested. Ceramic cylinders were treated according to group assignment and bonded to blocks of the same ceramic material with a dual-cured resin. The shear bond strength was determined, and the experimental factors were evaluated by analysis of variance. The results showed that surface-roughening method had the strongest effect on bond strength, while ceramic selection had the least significant effect. Of the surface-roughening methods, etching was associated with higher bond strength values than either sandblasting or grinding. Bond strength to etched ceramics remained constant after water storage, while the bond strength to both sandblasted and ground specimens decreased by from 50 to 75% compared with dry storage. Heating the MPS-coated specimens to 100°C resulted in bond strength twice as high than if no heating was used. Mechanical interlocking appears to be the key factor influencing the ceramic-composite bond strength.
Effects of Potassium Ions on Action Potential Conduction in A- and C-Fibers of Rat Spinal Nerves
Authors: Peacock J.M. , Orchardson R.
Published: January 2009

Potassium ions in dentifrices for treating 'hypersensitive' dentin are believed to act directly on intradental nerves by raising extracellular potassium ion concentration ([K+]o) sufficiently to prevent action potential generation by axonal accommodation. However, the [K+]o necessary to block nerve conduction is not precisely known, nor is it certain that K+ can diffuse from a dentifrice in sufficient amounts to inactivate intradental nerves. To establish more accurately the [K+]o required to block nerve conduction under controlled conditions, we studied the effects of increased [K+]o on the sizes of compound action potentials (CAP) recorded from rat spinal nerves in vitro. [K+]o was increased by the addition of either KCl or KNO3 to Krebs' solutions applied to the central portion of the nerves. CAP attenuation increased in a dose-dependent manner as [K+]o was raised in the 8 to 64 mmol/L range, and complete block was generally produced with solutions containing at least 32 mmol/L K+. CAP attenuation was reversible, and recovery times increased with increasing [K+]o. The effects of KCl and KNO3 solutions were the same for all [K+]o tested. Half-maximal (50%) reduction in the Aβ-fiber component of the CAP occurred with 17.4 mmol/L K+, and with 17.8 mmol/L and 19.3 mmol/L K+, respectively, for the AS- and C-fiber components. Control experiments with glucose and choline chloride confirmed that the conduction block observed with increased [K+]o was not due to increased solution osmolarity or ionic strength. Assuming that intradental axons are as sensitive to altered [K+]o as spinal nerve axons, we suggest that for K+ in dentifrices to block intradental nerve conduction: (1) [K+]o in excess of 8 mmol/L would have to be achieved around nerve axons in the inner dentin or peripheral pulp, and (2) increases in [K+]o of these magnitudes would have to be maintained in order for intradental nerve inactivation to be sustained.
Weakness in Mouse Masticatory Muscles by Repetitive Contractions with Forced Lengthening
Authors: Hutchins M.O. , Skjonsby H.S. , Brazeau G.A. , Parikh U.K. , Jenkins R.M.
Published: January 2009

The etiology of myofascial tenderness and pain of masticatory muscles in humans is difficult to understand. Parafunctional oral habits such as tooth grinding or vigorous chewing are thought to be factors. The objective of this study was to determine if masticatory muscles are susceptible to weakness and injury induced by repetitive, dynamic, forced-lengthening contractions. Results would support the hypothesis that contraction-induced injuries could occur in hyperactive masticatory muscles of humans in response to parafunctional oral habits. Mice were anesthetized and randomly assigned to three groups: non-treated controls, treated by repetitive passive jaw opening, or treated by repetitive isometric tetanic contractions with lengthening by jaw opening. In each treatment group, masticatory muscle injury was evaluated by contractile tension, plasma creatine kinase, and muscle glycogen. Contractile tension was determined at different stimulation frequencies and was significantly decreased 5 min, 4 h, and 72 h after repetitive contraction/lengthening. Plasma creatine kinase was significantly elevated at 4 but not at 72 h post-treatment in mice subjected to repetitive contraction/lengthening. Masticatory muscle glycogen was not significantly different in any groups at 4 or 72 h post-treatment. These results indicate that contraction injuries can be induced in masticatory muscle of mice by forced lengthening contractions which simulate eccentric contractions.
Specific and Charge Interactions Mediate Collagen Recognition by Oral Lactobacilli
Authors: McGrady J.A. , Butcher W.G. , Beighton D. , Switalski L.M.
Published: January 2009

The mechanisms by which oral lactobacilli, one of the three major genera of cariogenic bacteria, attach to tooth surfaces are unknown. We hypothesize that recognition of collagen, the major component of dentin, may be a mechanism which localizes these bacteria to exposed root surfaces as well as to carious lesions which have penetrated the dentin. We found that the majority of oral Lactobacillus spp. strains recognize and bind collagen type I. Binding of 125I-labeled collagen type I to two strains of L. casei rhamnosus has been characterized in some detail. These strains were previously characterized with respect to their attachment to dentin (Switalski and Butcher, 1994). The process of 125I-collagen binding was mediated via specific as well as charge interactions. The putative adhesin-mediated (specific) interaction involved a limited number of bacterial surface components (2 x 103/cell). Under conditions conducive for non-specific interactions (low ionic strength), the binding was higher by an order of magnitude. Collagen binding strains were found to adhere to collagen-coated surfaces, while strains unable to bind collagen adhered to a much lesser extent. Adherence of bacteria to collagen-coated surfaces could be competitively inhibited with collagen. These interactions may target collagen-binding strains of lactobacilli to dentin collagen in the oral cavity and thus play a role in the pathogenesis of root surface and/or coronal caries. Interference with this collagen-mediated attachment of lactobacilli may provide effective means of caries control, particularly in view of the fact that other oral acidogenic microbiota also interact with collagen.
Antigen Specificity of Serum Antibody in A. actinomycetemcomitans-infected Periodontitis Patients
Authors: Ebersole J.L. , Cappelli D. , Sandoval M.-N. , Steffen M.J.
Published: January 2009

We hypothesized that serum antibody with selected antigen specificities would relate to infection and disease in the patients and, thus, describe the characteristics of potential protective antibody. This study used serum samples from 24 periodontitis patients with subgingival infection and elevated serum IgG antibody to A. actinomycetemcomitans to define the antigenic specificities of IgG, IgM, IgA, and IgGl-4 antibody to A. actinomycetemcomitans strain Y4 outer membrane antigens (OMA). Uniform IgG antibody (> 70% of the patients) was noted to antigens with Mr of 65, 38, 29, and 17 kDa. Both IgA and IgM specificities reflected those shown for IgG in each patient. IgGl and IgG2 antibody reacted with several OMA bands in each patient, while IgG3 antibodies were directed to numerous OMA bands in many patients and represented the most broad-based response. The IgG4 response patterns were limited to a few OMA bands. We noted a prominent occurrence of IgG reactions with OMA bands that were characteristic for individual patients. The frequency of responses to OMA of higher Mr ( i.e., > 80 kDa) and to the 34-, 31-, and 24-kDa antigens was positively related to the total IgG antibody levels. Antibody reactive with OMA bands at 65-, 38-, 29-, 17-, 15-, and 11-kDa antigens was detected in patients with few to many teeth infected with A. actinomycetemcomitans. Furthermore, patients with a high percentage of teeth with ≥ 6 mm pockets had a decreased frequency of responses to the high-Mr antigens ( i.e. > 90 kDa) as well as to the 58-kDa antigen.

These findings indicate that human antibody reactivities with specific OMA bands of A. actinomycetemcomitans: (i) are positively correlated with the level of serum antibody, (ii) are associated with the number of teeth infected, and (iii) describe differences in the severity of the disease as measured by the frequency of teeth with deep pockets.
Localization of Active and Inactive Elastase, Alpha-1-Proteinase Inhibitor, and Alpha-2-Macroglobulin in Human Gingiva
Authors: Kennett C.N. , Cox S.W. , Eley B.M.
Published: January 2009

Biochemically, there is usually much less elastase activity in gingival tissue than in crevicular fluid. The tissue distributions of active and inactive elastase and the endogenous inhibitors alpha-1-proteinase inhibitor (α 1PI) and alpha-2-macroglobulin (α2M) were therefore compared. Inflamed tissue was obtained from chronic periodontitis patients, and cryostat sections were incubated with the histochemical elastase substrate MeOSuc-Ala-Ala-Pro-Val-MNA. Adjacent sections were examined immunocytochemically with antibodies to neutrophil elastase, α1PI, α2M, and leukocyte differentiation antigens. Antigenic elastase was widely distributed in CD15-positive granulocytes in both the epithelium and lamina propria as well as in granulomatous tissue from infrabony defects. However, there was very limited histochemical staining of these cells, and biochemical activity against the equivalent substrate MeOSuc-Ala-Ala-Pro-Val-AFC could be extracted only from sections with such staining. The pH optimum and effector response of the activity in the extracts were, nevertheless, consistent with those of leukocyte elastase. The large difference between the total elastase content of the tissue, as determined immunocytochemically, and the limited amount of active enzyme, as demonstrated histochemically, indicated that the majority was in an inactive form. The involvement of tissue inhibitors was suggested by the fact that extracts from sections with no histochemical staining reduced biochemical elastase activity in crevicular fluid. α2M was found in many fibroblasts and also some CD68-positive macrophages, which additionally contained α1PI. Both inhibitors appeared to be present extracellularly, since there was significant background staining. Thus, α1PI and α2M could contribute to the regulation of elastase activity in the gingiva.
Three-year Tooth Loss among Black and White Older Adults in North Carolina
Authors: Drake C.W. , Hunt R.J. , Koch G.G.
Published: January 2009

The distribution and determinants of tooth loss in older adults are poorly defined, especially in Blacks, who have been underrepresented in previous studies. This study investigated, epidemiologically, the distribution and predictors of tooth loss in elder Blacks and Whites by following a random sample of older adults in North Carolina for three years. It was hypothesized that Blacks would be at greater risk of tooth loss and would have different risk factors for tooth loss. Data from 263 Blacks and 228 Whites were collected by dental examinations and interviews conducted in the participants' homes. During the three-year follow-up, 53% of Blacks and 29% of Whites lost at least one tooth. Blacks lost 13% of their remaining teeth compared with 4% for Whites. Logistic regression models showed that factors related to tooth loss for Blacks were: more S. mutans in stimulated saliva, deeper periodontal pockets, more P. intermedia in subgingival plaque, high blood pressure, limited help from others, and few symptoms of depression. For Whites, significant factors were: more lactobacilli in stimulated saliva, history of current oral pain at baseline, more alcohol consumption, no history of past use of calcium or xerostomic medications, higher income, lower occupational prestige, and increased numbers of negative life events. This study showed that older Blacks were at greater risk of tooth loss than older Whites. For both races, factors such as oral bacteria, periodontal conditions, oral symptoms, and psychosocial and economic factors are related to increased risk of tooth loss.
The Fidelity of Initial Acquisition of Mutans Streptococci by Infants from Their Mothers
Authors: Li Y. , Caufield P.W.
Published: January 2009

Previous cross-sectional studies using bacteriocin profiles, serotyping, or genotyping suggest that mothers are the principle source of mutans streptococci (MS) to their infants. This study determined the commonality of MS genotypes between mothers and their infants at the time of initial acquisition. Oral bacteria of mothers and their infants were monitored from birth for approximately 3 years at three-month intervals. Genotypes of MS in infants appeared identical to those present in mothers in approximately 71% of 34 mother-infant pairs studied. Interestingly, female infants acquired MS genotypes identical to their mothers' with significantly greater fidelity than male infants (88% vs. 53%). Homology of genotypes between mothers and their infants at initial acquisition strongly suggests that MS strains were transmitted from mother to infant and that this transfer exhibited gender specificity. In no instance did we observe homology of genotypes between fathers and infants or fathers and mothers, further supporting the notion that acquisition of MS in humans follows maternal lines. Although the prevalence of dental caries was low in this young child population (11/34; 32%), we observed that male children who harbored the same genotype as their mothers had a 13 times greater likelihood of having caries than female children who acquired their mothers' strain; this difference was statistically significant (p < 0.01). Although we do not know the biological mechanisms governing fidelity of acquisition between a mother and her infant, our data suggest that caries outcome may be, in part, determined by both the source of MS and the presence of a specific genotype of MS. These findings point to continued studies which will further delineate the interrelation among gender, race, and caries outcome as a function of fidelity of transfer of MS from mothers to their infants.
The Diffusion and Enzymic Hydrolysis of Monofluorophosphate in Dental Plaque
Authors: Pearce E.I.F. , Dibdin G.H.
Published: January 2009

Although the ability of dental plaque to hydrolyze sodium monofluorophosphate (MFP) has been known for some time, its effect on the F- concentration at the plaque-enamel interface is undefined. We have determined enzyme kinetic values for MFP hydrolysis and diffusion coefficients so that the penetration and degradation of MFP in plaque can be modeled by computer. The KM and Vmax values for natural human plaque were 1.77 mmol/L and 41.4 nmol/min/mg protein, respectively, at pH 8.0. At pH 6.0, the Vmax was lower, 15.6 nmol/min/mg, but KM was not significantly different. Competitive inhibition by orthophosphate gave a Ki of 4.55 mmol/L. The diffusion coefficient for MFP in artificial plaque was 1.91 x 10-6 cm2/sec. When these data were used for mathematical modeling of the effects of rinsing with MFP and F-solutions, compared with an equivalent NaF application, the concentration of F- from MFP was lower at the inner surface of plaque, and the peak occurred later. Both pH and plaque thickness had a marked effect on the amount of MFP that could penetrate: At pH 8.0, almost none reached the inner surface of a 1-mm-thick plaque intact. At pH 6.0, however, more MFP was able to penetrate, due to lower MFPase activity. While MFP diffusion is inherently slower than that of F-, enzymic degradation increases the gradient for inward diffusion. If the conventional view that MFP in toothpaste acts as a source of F- is true, then MFP toothpaste should be formulated to optimize MFPase activity in dental plaque.
Characterization of Cellular Responses Involved in Reparative Dentinogenesis in Rat Molars
Authors: D'Souza R.N. , Bachman T. , Baumgardner K.R. , Butler W.T. , Litz M.
Published: January 2009

During primary dentin formation, differentiating primary odontoblasts secrete an organic matrix, consisting principally of type I collagen and non-collagenous proteins, that is capable of mineralizing at its distal front. In contrast to ameloblasts that form enamel and undergo programed cell death, primary odontoblasts remain metabolically active in a functional tooth. When dentin is exposed to caries or by operative procedures, and when exposed dentinal tubules are treated with therapeutic dental materials, the original population of odontoblasts is often injured and destroyed. The characteristics of the replacement pool of cells that form reparative dentin and the biologic mechanisms that modulate the formation of this matrix are poorly understood. Based on the hypothesis that events governing primary dentinogenesis are reiterated during dentin repair, the present study was designed to test whether cells that form reparative dentin are odontoblast-like. Cervical cavities were prepared in rat first molars to generate reparative dentin, and animals were killed at various time intervals. In situ hybridization with gene-specific riboprobes for collagen types I and III was used to study de novo synthesis by cells at the injured dentin-pulp interface. Polyclonal antibodies raised against dentin sialoprotein (DSP), a dentin-specific protein that marks the odontoblast phenotype, were used in immunohistochemical experiments. Data from our temporal and spatial analyses indicated that cells forming reparative dentin synthesize type I but not type III collagen and are immunopositive for DSP. Our results suggest that cells that form reparative dentin are odontoblast-like.
Multiple-outcomes Meta-analysis of Treatments for Periodontal Disease
Authors: Berkey C.S. , Antczak-Bouckoms A. , Hoaglin D.C. , Mosteller E. , Pihlstrom B.L.
Published: January 2009

The results of periodontal therapy vary by disease severity, outcome measure, and method of data analysis. Several clinical trials and a subsequent meta-analysis have demonstrated that, for teeth with severe disease, surgery decreases probing depth (PD) and increases attachment level (AL) more than non-surgical treatment. For other disease levels, the choice of therapy depends on the outcome measure. When clinical trials use two or more outcome measures (such as PD and AL), investigators ordinarily analyze each outcome separately. When the correlations are incorporated among the outcomes, a meta-analysis can use generalized-least-squares (GLS) regression to analyze multiple outcomes jointly. We applied the GLS multiple-outcomes model in a meta-analysis of 5 trials comparing surgical and non-surgical periodontal treatments, each assessing the outcomes PD and AL one year after treatment. The clinical conclusions are similar to those reported earlier, but our estimates of the relative benefits of surgical and non-surgical treatment should be more accurate, because the GLS method takes into account correlation between AL and PD. When correlations between the two outcomes rise, as they do with increasing severity of disease, the GLS estimates depart from those derived from separate analyses of PD and AL.
Monoclonal Antibodies Against a High-molecular-weight Agglutinin Block Adherence to Experimental Pellicles on Hydroxyapatite and Aggregation of Streptococcus mutans
Authors: Carlen A. , Olsson J.
Published: January 2009

High-molecular-weight (HMW) glycoproteins, agglutinins, in parotid saliva induce the aggregation of S. mutans and mediate binding of the bacteria to saliva-coated hydroxyapatite (SHA). Two types of monoclonal antibodies (mAb) directed against, respectively, protein and carbohydrate epitopes on the agglutinin have been reported to inhibit the aggregation of S. mutans. In this study, the mAbs were tested for their ability to block aggregation and adherence to SHA of S. mutans serotype c mediated by parotid, submaxillary, and whole saliva from three subjects. Both types of antibody inhibited the adherence and aggregation in a dose-dependent manner. However, individual variations were noted for the effects of the antibodies. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent immunoblotting with the antibodies revealed a > 300 kDa agglutinin component in all types of saliva and in the proteins desorbed from SHA. The degree of staining of this component in immunoblots of the salivas and the desorbates seemed to be paralleled by the rates of aggregation and adherence, respectively. Thus, our results indicate that the adherence to SHA as well as the aggregation of S. mutans serotype c is primarily mediated by structurally related, HMW glycoproteins in parotid, submaxillary, and whole saliva.
Differential Expression of IL-1β, TNF-α, IL-6, and IL-8 in Human Monocytes in Response to Lipopolysaccharides from Different Microbes
Authors: Agarwal S. , Piesco N.P. , Johns L.P. , Riccelli A.E.
Published: January 2009

Macrophages respond to bacterial lipopolysaccharides (LPS) and activate several host defense functions through production of mediators. However, it is not clear whether the degree of macrophage responsiveness to different sources of LPS is equivalent to or varies with the source of LPS. Therefore, in this report, we examined the extent of the human monocyte response to LPS derived from two oral pathogens, Actinobacillus actinomycetemcomitans ( Aa) and Porphyromonas gingivalis ( Pg). Additionally, due to its well-established ability to activate monocytes, we used LPS from Escherichia coli (Ec). Human monocytes, when activated with a specific source of LPS, exhibited rapid expression of mRNA for IL-1β, TNF-a, and IL-8, which was followed by IL-6, as measured by RNA-PCR. Moreover, the expression of mRNA for these cytokines was followed by cytokine synthesis. Monocytes from the same subject, when activated with LPS from Pg, Aa, or Ec expressed quantitatively different levels of mRNA and proteins for all four cytokines. A given LPS induced either high or low expression of the battery of cytokines tested, indicating that the expression of these pro-inflammatory cytokines may be regulated by a single or a cluster of gene(s). However, no apparent differences in the time course of mRNA expression for these cytokines were observed in response to any of the LPS tested. Furthermore, the relative ability of the different sources of LPS to induce mRNA for cytokines varied throughout a wide range of LPS concentrations. This suggests that differences exist in the sensitivity of monocytes to a specific LPS, rather than in the kinetics of the secretory process itself. The ability of LPS to induce cytokine-specific mRNA also depended on the source of monocytes. Our results demonstrate that monocyte activation and cytokine release depend on the physicochemical form of LPS as well as the source of monocytes. These critical determinants may be significant in the pathogenesis of periodontal infections.
Enhanced Cytokine Production and Collagen Synthesis of Gingival Fibroblasts from Patients with Denture Fibromatosis
Authors: Nakao K. , Yoneda K. , Osaki T.
Published: January 2009

The mechanisms of denture-induced gingival hypertrophy remain to be explored. Since fibroblast proliferation and bone resorption characterize this disorder, the possible involvement of cytokines was investigated. Gingival fibroblasts were obtained from six patients with denture fibromatosis (Den-Fb) and six healthy persons (Nor-Fb). Cells were compared for proliferation, collagen synthesis, and cytokine production. Incorporation of [3H]thymidine (TdR) was increased in 3 Den-Fb and 3 Nor-Fb lines in the presence of interleukin-1-beta (IL-1β) (10 U/mL) and tumor necrosis factor-alpha (TNF-a) (from 10 to 100 U/mL). Proline incorporation in Den-Fb was higher than that in Nor-Fb, and the mean collagen synthesis level in Den-Fb was significantly higher than that in Nor-Fb. Although there was no difference between the up-regulation of protein synthesis in Den-Fb and Nor-Fb induced by IL-1β or TNF-a, the receptors for these cytokines were expressed at higher levels in cell lines which exhibited higher protein synthesis. Between Nor-Fb and Den-Fb, there was no difference in the generation of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-6 (IL-6). However, most Den-Fb produced more GM-CSF and IL-6 in the presence of TNF-a. Enhancement of IL-6 generation by GM-CSF was also more prominent in Den-Fb. GM-CSF and IL-6 were synergistically generated after co-culture of the fibroblasts with gingival keratinocytes. GM-CSF and IL-6 generation of Den-Fb was markedly enhanced by co-culture of Den-Fb with peripheral blood mononuclear cells (PBMC), especially PBMC from patients. PBMC from patients generated more cytokines than did those from healthy subjects. These results indicate that cytokines generated in situ cooperatively by keratinocytes infiltrated mononuclear cells, and fibroblasts evoke up-regulation of collagen synthesis by fibroblasts expressing cytokine receptors.
Light Deposition in Dental Hard Tissue and Simulated Thermal Response
Authors: Seka W. , Fried D. , Featherstone J.D.B. , Borzillary S.F.
Published: January 2009

Near-IR (- 1 um) lasers are presently used for a variety of intra-oral applications including dental hard tissue ablation, although the light intensity distribution and subsequent heating of the hard tissue are still poorly understood. This paper presents a detailed numerical study of the scattered light intensity distribution along with the corresponding predicted thermal response. The calculations are based on recently published scattering and absorption data for dental hard tissue around 1 um. Our simulations indicate strongly enhanced energy deposition and concomitant heating near the dentino-enamel junction (DEJ), mainly due to the higher absorption in dentin. We predict from 10 to 20 times higher internal temperatures near the DEJ compared with the surface. For example, for 50-ms pulses of 5-J energy on a 3-mm-diameter spot (- 1 kW/cm2 or - 50 J/cm2), one can expect internal temperatures near the DEJ in excess of 100°C. Elevated temperatures are predicted to extend far into the dentin, endangering the vitality of the pulp several millimeters below the surface. Our results are compared with published experimental data taken under similar conditions and are found to be in good general agreement. The results of this study do not contradict recently reported ablation of dentin with Nd:YAG laser radiation by contact fiber probes. In this case, the irradiation intensities are 3 to 4 orders of magnitude higher, so plasma formation and plasma shielding of the interior of the tooth are likely.
Tensile Properties of Resin-infiltrated Demineralized Human Dentin
Authors: Sano H. , Takatsu T. , Ciucchi B. , Russell C.M. , Pashley D.H.
Published: January 2009

The ability of adhesive resins to restore the physical properties of demineralized dentin has not been well-documented. The unfilled resins that are used for adhesion have relatively low moduli of elasticity and limited ability to increase dentin stiffness, although they may increase the ultimate tensile strength of dentin. This study tested the hypothesis that resin infiltration of demineralized dentin can restore its tensile properties to those of mineralized dentin. Small (ca. 0.5 mm thick x 0.5 mm wide) specimens of demineralized human dentin were infiltrated with one of five different dentin bonding resins over many hours, to determine how these resins altered the tensile properties of dentin. Tensile stress and strain were measured in these and control (mineralized and demineralized) specimens until their ultimate failure. The results indicate that some adhesive resins, after infiltrating demineralized dentin, can restore and even exceed the ultimate tensile strength of mineralized dentin. These resins increased the modulus of elasticity of resin-infiltrated dentin to values equal to or greater than those of the resins but far below those of mineralized dentin. Although the conditions in this experiment were far removed from the manufacturer's recommendations or clinical practice, the results support the potential of resin infiltration for reinforcing dentin.
Preparation and Characterization of Cyclopolymerizable Resin Formulations
Authors: Stansbury J.W. , Dickens B. , Liu D.-W.
Published: January 2009

An amine-catalyzed reaction between acrylates and formaldehyde has been used to convert mono-acrylates to difunctional monomers and di-acrylates to multifunctional oligomers by linking the acrylic double bonds together in 1,6-diene pairs. The resulting monomers and oligomers undergo efficient cyclopolymerization to high conversion with significantly less shrinkage than normally found for acrylates. In this study, a convenient single-step process was used with mixtures of mono- and di-acrylate starting materials to produce a series of resins with potential for effective cyclopolymerization. Incremental changes in the ethyl acrylate (EA) to ethoxylated bisphenol A diacrylate (EBPAD) ratio directly supplied cyclopolymerizable resins with a broad range of viscosities and product distributions. Those resins produced from reaction mixtures rich in EA have low viscosities because of high diluent monomer contents and limited oligomerization of EBPAD due to end-cap formation. Resin viscosity and average molecular weight of the oligomeric component of the resin were inversely related to the amount of EA used in the reaction. Through the choice of reactants and their ratio, this simple technique has the potential to provide cyclopolymerizable resins for use in a variety of dental polymer applications.
Ethical Issues in Sponsored Clinical Research
Authors: Barnett M.L.
Published: January 2009

In recent years, the relationship between industry and academic investigators has been strengthened and has become increasingly complex, creating a variety of situations which have the potential of leading to ethical compromises. Two categories of behavior have been the primary concern of those dealing with ethical issues in science, namely, scientific misconduct and conflict of interest. This paper presents an overview of emerging ethical concerns as well as institutional responses designed to manage the new relationships.