bluuebunny/crossref_metadata_2025 huggingface dataset:
An in vitro Model of Human Dental Pulp Repair
Authors: Magloire H. , Joffre A. , Bleicher F.
Published: January 2009

Pulp tissue responds to dentin injury by laying down reactionary dentin secreted by existing odontoblasts or reparative dentin elaborated by odontoblast-like cells that differentiated from precursor cells in the absence of inner dental epithelium and basement membrane. Furthermore, growth factors or active dentin matrix components are fundamental signals involved in odontoblast differentiation. In vitro, dental pulp cells cultured under various conditions are able to express typical markers of differentiation, but no culture system can re-create pulp response to dentin drilling. This paper reports the behavior of thick slices from human teeth drilled immediately after extraction and cultured from 3 days to 1 month. Results show that the damaged pulp beneath the cavity is able to develop, in vitro, some typical aspects correlated to tissue healing, evidenced by cell proliferation (BrdU-positive cells), neovascularization (positive with anti-type-IV collagen antibodies), and the presence of functional (3H proline-positive) cuboidal cells close to the injured area. After 30 days of culture, elongated spindle-shaped cells can be seen aligned along the edges of the relevant dentin walls, whereas sound functional odontoblasts are well-preserved beneath healthy areas. This tissue recovery leads us to believe that such a culture model will be a useful system for testing factors regulating pulp repair.
Membrane Components of Treponema denticola Trigger Proteinase Release from Human Polymorphonuclear Leukocytes
Authors: Ding Y. , Uitto V.-J. , Haapasalo M. , Lounatmaa K. , Konttinen Y.T. , Salo T. , Grenier D. , Sorsa T.
Published: January 2009

Tissue destruction during periodontitis is believed to be primarily brought about by leukocyte proteinases. We postulate that oral spirochetes cause discharge of polymorphonuclear leukocyte (PMN) lysosomal enzymes. Effects of Treponema denticola 53-kDa outer membrane protein, lipopolysaccharide (LPS), and peptidoglycan on degranulation of matrix metalloproteinases (MMP)-8 (collagenase) and -9 (gelatinase), cathepsin G, and elastase by human peripheral blood PMNs were studied by specific enzyme assays and Western blot analysis. T. denticola 53-kDa outer membrane protein was found to be a particularly efficient inducer of MMP-8 release. The induction was comparable with that of phorbol myristate acetate, a known inducer of PMN specific granule discharge. All of the treponemal substances, most notably the 53-kDa protein and LPS, induced release of MMP-9, a component of C-type granules. Both collagenase and gelatinase released from PMNs were mostly in active forms. Release of cathepsin G and elastase was also observed with the 53-kDa protein treatment. The other T. denticola substances did not induce release of these serine proteinases. Lactate dehydrogenase was not released from PMNs by the treatments, indicating that the degranulation was specific and not caused by toxic effects of the substances. This was confirmed by transmission electron microscopy of PMNs treated with the 53-kDa protein that showed rapid vacuole formation and cell shape changes but no disintegration of the cells. Thus, T. denticola may participate in the PMN-dependent extracellular matrix degradation during the course of periodontal inflammation by triggering the secretion and activation of matrix metalloproteinases.
Distributional Changes of Osteoclasts and Pre-osteoclastic Cells in Periodontal Tissues during Experimental Tooth Movement as Revealed by Quantitative Immunohistochemistry of H+-ATPase
Authors: Yokoya K. , Sasaki T. , Shibasaki Y.
Published: January 2009

To investigate the mechanism of alveolar bone remodeling in response to orthodontic force application, we examined the distribution of osteoclasts and pre-osteoclastic cells using quantitative immunohistochemistry of vacuolar-type H+-ATPase. For orthodontic force to be produced by the Waldo method, an orthodontic elastic band was inserted between the upper first and second molars of rats. The observed areas of periodontal tissues around second molars were the distal surfaces of mesial roots, as the pressure side, and the mesial surfaces of distal roots, as the tension side. Specific expression of vacuolar-type H+-ATPase at the ultrastructural level was detected in mononuclear and multinucleated pre-osteoclastic cells, as well as osteoclasts with ruffled borders on bone surfaces. At 6 hrs after orthodontic force application, many osteoclasts and pre-osteoclastic cells with H+-ATPase expression were first observed in vascular canals of the alveolar bone crest near the pressure side of the periodontal ligament, but the number of osteoclasts was not increased in the periodontal ligament. On day 1 after tooth movement, osteoclasts were increased in number in the periodontal ligament and in adjacent alveolar bones on the pressure side, but were seldom observed in corresponding areas on the tension side. The number of osteoclasts increased until day 7, but had decreased by day 14. These results suggest that, in bone remodeling during experimental tooth movement, (1) osteoclasts and pre-osteoclastic cells can be identified by H+-ATPase immunohistochemistry, (2) osteoclasts and pre-osteoclastic cells are rapidly induced after force application, (3) osteoclast induction first occurs in vascular canals of the alveolar bone crest on the pressure side, and then, (4) the number of osteoclasts increases in the periodontal ligament on the pressure side.
An FT-Raman Spectroscopic Investigation of Dentin and Collagen Surfaces Modified by 2-Hydroxyethylmethacrylate
Authors: Xu J. , Stangel I. , Butler I.S. , Gilson D.F.R.
Published: January 2009

Although 2-hydroxyethylmethacrylate (HEMA) is commonly used for adhesive bonding to dentin, its role in promoting adhesion is not completely understood. Here, we use FT-Raman spectroscopy to elucidate further the nature of the interaction of HEMA with dentin. Ground dentin was exposed to 2.5% (w/w) nitric acid, washed, dried in air, and treated with HEMA. The samples were then sequentially washed with distilled water, with FT-Raman spectra being obtained after different wash times. Hydroxyapatite and bovine type I collagen were similarly treated with HEMA except for the acid exposure. The FT-Raman spectra of these samples were also recorded. The spectra of HEMA-treated, water-washed dentin and collagen revealed the following changes: (1) The band intensities of HEMA absorbed on dentin and collagen decreased with increasing wash times; (2) the v(C=O) and v(CCO) modes of HEMA at 1718 and 607 cm -1, respectively, either disappeared or decreased after extensive washing; (3) the v(C=C) (1640 cm-1) and δ(=CH2) (1403 cm -1) bands exhibited minor variations in band position and relative intensity. These results demonstrate that HEMA interacts with dentin both physically and chemically. The chemical interaction can be interpreted by either hydrogen bonding or the formation of a new bond to the ester group of HEMA.
Changes in the Permselectivity of Human Teeth during Caries Attack
Authors: Vogel G.L. , Mao Y. , Carey C.M. , Chow L.C.
Published: January 2009

Previous studies have shown that enamel permselectivity can influence fluid composition within caries lesions during de- and remineralization. The permselectivity of human enamel, cementum, and dentin sections was examined, in a microwell model, by measurement of the membrane potential developed by KCl diffusion while the sections were immersed in solutions simulating resting (pH = 5.6) and cariogenic plaque fluid (pH = 4.8). In a second experiment, the effects of charged compounds (phytate and Zonyl-FSC) on the tooth permselectivity were examined. The average membrane potentials (± SD) in "resting plaque" solution were: sound enamel, 18.9 ± 3.2 mV, n = 66; dentin, 0.9 ± 9.2 mV, n = 59; and cementum, -0.8 ± 8.2 mV, n = 42, with a positive sign indicating cation selectivity. The average membrane potentials became more negative in "cariogenic plaque" solution for all types of sections: sound enamel, 5.2 ± 2.1 mV, n = 46; dentin, -8.1 ± 7.4 mV, n = 45; and cementum, -14.3 ± 8.0 mV, n = 34. In lesion enamel sections, the membrane potential was reduced from the non-lesion wells in both types of test solutions, while phytate treatment caused an increase of approximately 10 mV in potential (increased cation selectivity) in every enamel well in either "resting" or "cariogenic" solution. Treatment of enamel sections with Zonyl-FSC caused the membrane potential to become more negative in both test solutions, with many of the wells showing anion selectivity in the cariogenic "plaque-like" solution. However, the changes in enamel membrane potentials induced by Zonyl-FSC slowly increased toward the initial values after treatment, while the effects of the phytate pre-treatment persisted. Most dentin sections treated with phytate also showed an increase in potential after phytate treatment; however, Zonyl-FSC seemed to have little effect on the membrane potential of dentin. The results of this study suggest that modification of tooth permselectivity by surface-active agents may be a viable method of decreasing the rate of caries progression.
Description of Mandibular Finite Helical Axis Pathways in Asymptomatic Subjects
Authors: Gallo L.M. , Airoldi G.B. , Airoldi R.L. , Palla S.
Published: January 2009

Despite wide use of systems to record jaw motion with six degrees of freedom, most studies have analyzed only the movement of a single mandibular point. The finite helical axis (FHA) is a mathematical model which can be used to describe comprehensively the movements of a rigid body. The aim of this investigation was to describe the FHA of the mandible during habitual jaw movements. Thirty subjects (13 females, 17 males; mean age, 26 years; range, 18 to 34 years) without myoarthropathies of the masticatory system participated in the study. Opening and closing movements, performed at 1-Hz frequency, were recorded with the optoelectronic system Jaws-3D. Three opening and closing movements were recorded from the right side and three from the left side of the jaw. The movement data were low-pass-filtered for noise reduction prior to the computation of the finite helical axis by means of a software program developed in our laboratory. The following parameters were calculated: the rotation of the FHA, its spatial orientation, and the translation along it, as well as its position and distance relative to an intracondylar point. In addition, methodological errors of the model were calculated.

During opening and closing, the group mean FHA rotation was 24.3° ± 4.2°. The group mean of the maximum total translation along the FHA was 0.9 ± 0.7 mm. The group mean distance between the FHA and the intracondylar point was 48.9 ± 9.9 mm. The FHA pathways were smooth and varied between individuals. Furthermore, the finite helical axes were never localized within the condyle, and often were located outside of the mandible. The analysis of the FHA pathways yields more information on whole mandibular movements than simply the movements of a single condylar point.
Movements of the Mandibular Condyle Kinematic Center during Jaw Opening and Closing
Authors: Yatabe M. , Zwijnenburg A. , Megens C.C.E.J. , Naeije M.
Published: January 2009

Little is known about the detailed kinematics of the human temporomandibular condyle during jaw opening and closing. According to the rotate and swing model by Osborn (1989), the condyle is kept in close contact with the articular eminence during opening. Whether the condyle is in closer contact with the articular eminence during opening than during closing is unknown. Another consequence of the model is that the opening condylar movements are less variable than the closing movements. In this study, the hypothesis that the opening condylar path is closer to the articular eminence and also less variable than the closing condylar path is tested. Twenty subjects (10 males and 10 females with a mean age of 22) without signs or symptoms of a craniomandibular disorder performed 2 series of 4 protrusive movements and 2 series of 4 empty opening-closing movements. The movements were recorded by a six-degrees-of-freedom opto-electronic jaw movement recording system (OKAS-3D). The kinematic center of the condyle was used as a reference point for the reconstruction of condylar movement paths. Characteristics of the opening and closing paths were investigated by means of a displacement index (DI). This index is the quotient between the three-dimensional path length and the three-dimensional path distance between the start and the end point of an opening or closing movement of the kinematic center. The DI was smaller (p < 0.0001) and also less variable (p < 0.0001) during opening than during closing. The smaller DI value, in combination with the concave nature of the movement path, indicates that the opening path of the kinematic center lies above the closing path and thus closer to the articular eminence.
Human Salivary Mucin MG1 Selectively Forms Heterotypic Complexes with Amylase, Proline-rich Proteins, Statherin, and Histatins
Authors: Iontcheva I. , Oppenheim F.G. , Troxler R.F.
Published: January 2009

Heterotypic complexes between the high-molecular-weight mucin MG1 and other salivary proteins in human submandibular/sublingual secretion (HSMSL) could have a significant impact on the biological properties of these proteins in oral fluids in both health and disease. We describe a mild procedure for isolation and purification of native MG1 by gel filtration chromatography on Sepharose CL-2B which does not involve dialysis, lyophilization, use of denaturing agents, or covalent modification. Western blots of native MG1 probed with antibodies against 8 different salivary proteins showed that complexing occurs between MG1 and salivary amylase, proline-rich proteins (PRPs), statherins, and histatins but not MG1, slgA, secretory component, or cystatins. When native MG1 was placed in 4 M guanidine hydrochloride and chromatographed on Sepharose CL-4B, ELISA measurement of column fractions showed that amylase, PRPs, statherins, and histatins were released. Interestingly, gel filtration resolved the material which eluted into 4 or 5 distinct peaks, suggesting that the released entities were heterotypic complexes. From these studies, the occurrence of at least three different types of complexes between MG1 and other salivary proteins has been identified. Type I complexes are dissociated by SDS-PAGE and in 4 M guanidine hydrochloride. Type II complexes are not dissociated under these conditions. Type III complexes are dissociated during SDS-PAGE and by 4 M guanidine hydrochloride, but the released proteins appear to be complexes containing amylase, PRPs, statherins, and histatins. The possible functional role of heterotypic complexes between MG1 and other salivary proteins as a physiologic delivery system, a mechanism for protection against proteolysis, a repository for precursors of the acquired enamel pellicle, and a vehicle for modulation of the viscoelastic and rheological properties of saliva is discussed.
Effect of Pressure Difference on the Quality of Titanium Casting
Authors: Watanabe I. , Watkins J.H. , Nakajima H. , Atsuta M. , Okabe T.
Published: January 2009

In casting titanium using a two-compartment casting machine, Herø et al. (1993) reported that the pressure difference between the melting chamber and the mold chamber affected the soundness of the castings. This study tested the hypothesis that differences in pressure produce castings with various amounts of porosity and different mechanical properties values. Plastic dumbbell-shaped patterns were invested with an alumina-based, phosphate-bonded investment material. Both chambers of the casting machine were evacuated to 6 x 10-2 torr; the argon pressure difference was then adjusted to either 50, 150, 300, or 450 torr. The porosity of the cast specimens was determined by x-ray radiography and quantitative image analysis. Tensile strength and elongation were measured by means of a universal testing machine at a strain rate of 1.7 x 10-4/s. The fractured surfaces were examined by SEM. Changes in Vickers hardness with depth from the cast surface were measured on polished cross-sections of the specimens. Raising the argon pressure difference to 300 and 450 torr caused a significant increase in internal porosity and a resultant decrease in the engineering tensile strength and elongation. The highest tensile strength (- 540 MPa), elongation (- 10%), bulk hardness (HV50g 209), and lowest porosity level (- 0.8%) occurred in the specimens cast at 150 torr. Turbulence of the metal during casting was thought to be responsible for the increase in porosity levels with the increase in argon pressure difference. By choosing an argon pressure difference (around 150 torr) suitable for this geometry, we could produce castings which have adequate mechanical properties and low porosity levels.
Porphyromonas gingivalis Fimbriae Mediate Coaggregation with Streptococcus oralis through Specific Domains
Authors: Amano A. , Fujiwara T. , Nagata H. , Kuboniwa M. , Sharma A. , Sojar H.T. , Genco R.J. , Hamada S. , Shizukuishi S.
Published: January 2009

Fimbriae are major adhesive components on the cell surface of Porphyromonas gingivalis. In this study, we evaluated the role of fimbriae in coaggregation with Streptococcus oralis. Fimbriae purified from P. gingivalis competitively inhibited the coaggregation by 100% at a concentration of 50 ug/mL. On the other hand, the same amount of lipopolysaccharide isolated from P. gingivalis was inhibited by only 25% of the level of the fimbriae. A fimA-inactivated mutant of P. gingivalis failed to show distinct coaggregation activity. Fimbriae added to a solution of various strains of streptococci caused their self-aggregation at a concentration of 10 to 30 ug/mL. The self-aggregation induced by fimbriae was inhibited by \-arginine (20 to 40 mM/L). Iodinated fimbriae reacted with S. oralis cells immobilized on the nitrocellulose membrane, and 100°C heating of the cells diminished the binding abilities. Recombinant fimbrillin (r-Fim, corresponding to whole residues 1 to 337 of native fimbrillin) of P. gingivalis also showed 100% inhibition of the coaggregation. The r-Fim variant (residues 1 to 286) lacking the C-terminal 51 residues was as inhibitory as r-Fim. However, the variant (residues 1 to 265) without the C-terminal 72 residues lost 77% of the inhibitory activity. These findings suggested that residues 266 to 286 contain a domain involved in the coaggregation of P. gingivalis with S. oral is. Inhibition by three polypeptides corresponding to residues 266 to 286, 266 to 337, and 287 to 337 was studied. Peptides 266 to 286 and 266 to 337 inhibited by 96 and 100%, respectively, at a concentration of 1.5 nmol/mL. Peptide 287 to 337 also showed a significant inhibitory effect but to a slightly lesser extent than that of peptide 266 to 286. P. gingivalis fimbriae appear to be involved in coaggregation with streptococci, probably through an adhesive protein molecule(s) of the latter, and the fimbriae possess several domains in the C-terminal residues 266 to 337 for interaction with S. oralis.
The Effects of Simple Interventions on Tooth Mortality: Findings in One Trial and Implications for Future Studies
Authors: Hujoel P.P. , Powell L.V. , Kiyak H.A.
Published: January 2009

The purpose of this report was to use a particular clinical trial, the Preventive Geriatric Trial (PGT), as a starting point to discuss whether treatment efficacy can be evaluated by means of tooth mortality. In the PGT, 296 subjects were recruited and randomly assigned to five treatment groups: (1) usual procedures (UP); (2) UP + a cognitive-behavioral intervention (CB); (3) UP + CB + weekly chlorhexidine rinse (CHX); (4) UP + CB + CHX + semi-annual fluoride varnish (F); and (5) UP + CB + CHX + F + semi-annual prophylaxis, including scaling (P). Exploratory analyses revealed that tooth mortality after the 1st year was lower in treatment groups 3, 4, and 5 than in groups 1 and 2. A one-year exposure resulted in a 45% reduction in tooth mortality (p < 0.05); a two-year exposure resulted in a 59% reduction (p-value < 0.04). The PGT findings suggested that it is possible to design trials based on clinically relevant endpoints, such as tooth mortality. For the detection of moderate treatment effects, such trials could take the form of Large, Simple Trials (LST), where many subjects are recruited with minimally restrictive entry criteria, and data are collected only on essential baseline characteristics and tooth mortality. LSTs have provided "reliable answers to important clinical questions" for other chronic diseases, and several arguments suggest that they could play a similar critical role in dental research: (1) Periodontitis and caries are among the most common and costly chronic diseases affecting humans, and the identification of even moderately effective treatments by LSTs can have a large socio-economic impact; (2) the identification of low-cost widely practicable treatments that lend themselves to be investigated in LSTs is likely to benefit more people than the identification of high-cost complex treatments; and (3) tooth mortality is simple to assess and more relevant than the unvalidated surrogate endpoints that have largely failed for more than 20 years to provide reliable answers to certain controversial issues regarding treatment efficacy. The cost of not reliably establishing the safety and the efficacy of treatments may be far greater than the cost of conducting LSTs.
Comparative Physico-mechanical Characterization of New Hybrid Restorative Materials with Conventional Glass-ionomer and Resin Composite Restorative Materials
Authors: Gladys S. , Van Meerbeek B. , Braem M. , Lambrechts P. , Vanherle G.
Published: January 2009

The recently developed hybrid restorative materials contain the essential components of conventional glass ionomers and light-cured resins. The objective of this study was to determine several physical and mechanical properties of eight such materials in comparison with two conventional glass ionomers, one micro-filled, and one ultrafine compact-filled resin composite. The two resin composites and two of the three polyacid-modified resin composites could be polished to a higher gloss than the conventional as well as the resin-modified glass ionomers. After abrasion, surface roughness increased for all materials, but not at the same extent, being the least for the conventional resin composites and one polyacid-modified resin composite, Dyract. In contrast to the latter resin composites, of which the surface roughness is principally determined by the presence of protruding filler particles above the resin matrix, roughness of conventional and resin-modified glass ionomers results from both protruding filler particles and intruding porosities. The mean particle size of the hybrid restorative materials fell between the smaller mean particle size of the resin composites and the larger one of the conventional glass ionomers. The micro-hardness and Young's modulus values varied substantially among all eight hybrid restorative materials. For all the resin-modified glass-ionomer restorative materials, the Young's modulus reached a maximum value one month after mixing and remained relatively stable thereafter. The Young's modulus of the conventional and the polyacid-modified resin composites decreased slightly after one month. The conventional glass-ionomer materials undoubtedly set the slowest, since their Young's modulus took six months to reach its maximum. The flexural fatigue limit of the hybrid restorative materials is comparable with that of the micro-filled composite. From this investigation, it can be concluded that the physico-mechanical properties vary widely among the eight hybrid restorative materials, indicating that these materials probably have yet to achieve their optimum properties. Their mechanical strength is inadequate for use in stress-bearing areas, and their appearance keeps them from use where esthetics is a primary concern.
Oral Mucosal Smokeless Tobacco Lesions among Adolescents in the United States
Authors: Tomar S.L. , Winn D.M. , Swango P.A. , Giovino G.A. , Kleinman D.V.
Published: January 2009

The presence of oral smokeless tobacco lesions among adolescents may be an early indicator of increased risk for oral cancers. Data from the 1986-1987 National Survey of Oral Health in US School Children were used to examine the cross-sectional relationship between the use of tobacco and alcohol and the presence of white or whitish oral soft-tissue lesions. The sample included 17,027 schoolchildren (aged 12 to 17 years) who provided information on the use of snuff, chewing tobacco, cigarettes, and alcohol and who received oral clinical examinations. Smokeless tobacco lesions were detected in 1.5% of students (projects to about 300,000 nationally), including 2.9% of males and 0.1% of females. These lesions were more prevalent among whites (2.0%) than among African-Americans (0.2%) or Hispanics (0.8%). Modeling with multivariate logistic regression revealed that, among white males, current snuff use was the strongest correlate of lesions [odds ratio (OR) = 18.4; 95% confidence interval (CI) = 8.5-39.8], followed by current chewing tobacco use [OR = 2.5; 95% CI = 1.3-5.0]. Lesions were strongly associated with duration, monthly frequency, and daily minutes of use of snuff and chewing tobacco. These data suggest that snuff may be a stronger risk factor than chewing tobacco for smokeless tobacco lesions, but the use of either of these forms of oral tobacco exhibits a dose-response relationship with the occurrence of lesions. We found little evidence that the use of alcohol or cigarettes may increase the risk of smokeless tobacco lesions. Preventing smokeless tobacco lesions and their possible malignant transformation may be best accomplished among adolescents by preventing the use of snuff and chewing tobacco.
Changes in Self-reported Dental Anxiety in New Zealand Adolescents from Ages 15 to 18 Years
Authors: Thomson W.M. , Poulton R.G. , Kruger E. , Davies S. , Brown R.H. , Silva P.A.
Published: January 2009

Little is understood of the natural history of dental anxiety. The aim of this study was to examine three-year changes in self-reported dental anxiety among adolescent participants in the Dunedin Multidisciplinary Health and Development Study. Dental anxiety was estimated at ages 15 and 18 by means of the Corah Dental Anxiety Scale (DAS). A DAS score of 13+ defined high dental anxiety. Participants were assigned to one of four dental-anxiety study groups (Chronic, Incident, Remitted, or Never) on the basis of changes in reported level of anxiety from ages 15 to 18. Results are reported for the 691 participants who completed the DAS at both ages. The sample's overall dental anxiety score decreased significantly from age 15 (mean, 8.79) to 18 (8.52) (paired t test, t = 2.37; P < 0.05). The Chronic and Never groups had small negative DAS increments, the Incident group showed a substantial positive increment, and the Remitted group recorded an even larger negative increment. Multivariate analysis showed that the DAS score at age 15 was the sole predictor of the change in DAS score for the Chronic and Remitted groups, and was a co-predictor for the Incident and Never groups. An episodic dental visiting pattern was a strong predictor of a positive change in DAS score for the Incident group; and for the Never group, a higher DMFS score at age 15 predicted a positive change in DAS score at 18, but being female was predictive of a decrement. This study indicates lower stability of dental anxiety in late adolescence than has been reported from other age groups.
Three-year Changes in Self-perceived Oral Health Status in an Older Canadian Population
Authors: Locker D. , Jokovic A.
Published: January 2009

Although change is a central goal of oral health care interventions, little attention has yet been paid to change in self-perceptions of oral health status. This is an important omission, given the current emphasis on assessing health outcomes. This paper reports the results of a study which examined changes over a period of three years in self-perceived oral health among 611 community-dwelling Canadians aged 50 years and over. Change in self-perceptions was measured by means of a global transition item and change scores derived from repeat administrations of four subjective oral health status indicators. Overall, 20.5% reported that their oral health had deteriorated over the three-year observation period, 68.5% that it had remained the same, and 10.5% that it had improved. There was a significant association between these global change categories and change scores for the four subjective indicators. Because of the small number of edentulous subjects, the analysis of baseline characteristics predicting change was confined to dentate subjects. Bivariate and logistic regression analyses were used to compare the two groups reporting change with those whose oral health status remained stable over the observation period. The results suggest that, when compared with this reference group, those who deteriorated and those who improved were similar in some respects but distinct in others. Those who improved appeared to have specific oral conditions at baseline causing pain. Those who deteriorated had poor oral health in general and came from more disadvantaged backgrounds. However, the explanatory power of logistic regression models predicting change in self-perceived oral health was poor when judged in terms of model sensitivities. This was to be expected, given that the models did not include variables documenting the incidence of disease, receipt of dental care, or changes in social and personal circumstances over the observation period.
Why do Shear Bond Tests Pull Out Dentin?
Authors: Versluis A. , Tantbirojn D. , Douglas W.H.
Published: January 2009

It is widely accepted that a dentin shear bond test which pulls out dentin must mean that the adhesive strength is superior to the cohesive strength of the dentin. Using numerical modeling techniques, Van Noort et al. (1988,1989) and DeHoff et al. (1995) alerted the scientific community that there were massive stress concentrations in the familiar dentin bond test. It is not inconceivable that these localized high tensile stresses could initiate cracks which diverge monolithically into dentin, leaving the interface unchallenged. To test this hypothesis, we developed a failure accumulation simulation program which determined localized failure interactively "on the fly" with a finite element solver, and also included brittle behavior, adhesive and cohesive failure, stochastic response, and dynamic remeshing. All of the familiar dentin bond variables were included in the simulation. A parallel experimental dentin bond test validation was run, and the fractography was examined in the scanning electron microscope for mode of failure. The simulation confirmed the tensile monolithic fracture hypothesis. It is also confirmed that dentin pull-out was partly due to the biomechanics of the test and did not necessarily mean superior adhesive strength or even that the cohesive strength of the dentin was reduced. There is clear need for a new technology for the evaluation of biological interfaces, and the present work has shown the vital role of numerical modeling in the interpretation of such experimental procedures.
The Genetic Contribution to Dental Maturation
Authors: Pelsmaekers B. , Loos R. , Carels C. , Derom C. , Vlietinck R.
Published: January 2009

It has been established in the literature that there is a major genetic impact on tooth size (Potter et al., 1976; Corruccini and Sharma, 1985; Sharma et al., 1985), tooth morphology (Kraus and Furr, 1952; Biggerstaff, 1970), and root formation (Garn et al., 1960; Green and Aszkler, 1970). None of the studies concerning root formation, however, used the more advanced method of path analysis and model fitting to estimate genetic influence. The aim of the present study was to determine the genetic and environmental influence on dental maturation. Dental age scores were determined on panoramic radiographs of 58 pairs of twins-26 monozygotic (MZ) and 32 dizygotic (DZ)-with the method of Demirjian et al. (1973). No mirror-image effect was found between the sides of the same individual or between twin members, so dental maturation seems to be symmetrical for both left and right sides of the mandible. Correlation coefficients were significantly higher in MZ than in DZ twins, which suggests a genetic influence. Model fitting showed that the variation in dental age was best explained by additive genetic influences (A-component) (43%) and by environmental factors common to both twins (C-component) (50%). The specific environment (E-component) added only 8% to the model. The importance of the common environmental factor can be explained by the fact that twins, being raised together, share the same prenatal, natal, and immediate post-natal conditions that are of importance for the formation of the teeth.
Effect of Amine- and Stannous Fluoride on Human Neutrophil Functions in vitro
Authors: Shapira L. , Schatzker Y. , Gedalia I. , Borinski R. , Sela M.N.
Published: January 2009

Amine fluoride (AmF)- and stannous fluoride (SnF2)-containing products were found to have a therapeutic effect on gingivitis and periodontitis. This effect was suggested to correlate with the antibacterial activity of the fluoride compounds. However, their effect on inflammatory cell function can also play a role in the therapeutic effect on gingival inflammation. The present study was designed to test the effects of AmF, SnF2, and an AmF/SnF2 combination on the function of human peripheral blood neutrophils, as compared with effects of chlorhexidine and salicylic acid. Neutrophils were isolated from human blood by ficoll centrifugation followed by dextran sedimentation. The neutrophils were pre-incubated with AmF, SnF 2, or AmF/SnF2, followed by stimulation with fMLP. Cell vitality was verified by trypan-blue exclusion (> 95% vitality at all tested concentrations). Superoxide production was measured by cytochrome C reduction and the enzymatic activity of lysozyme and β-glucoronidase by optical density measurement of substrate conversion. The results showed that AmF, SnF2, or AmF/SnF2 enhanced by two- to three-fold the superoxide release from fMLP-stimulated human neutrophils. Furthermore, the effective concentration of the AmF/SnF2 combination was several-fold lower than that of AmF or SnF2 alone (10 nM for AmF, 0.5 μM for SnF2, and 3 pM for SnF2/AmF). On the other hand, chlorhexidine and salicylic acid were found to reduce superoxide production by the cells. All the tested compounds had no effect on granular enzyme release by the stimulated neutrophils. The results suggest that AmF and SnF2 enhance the oxygen-dependent antibacterial activity of neutrophils. This effect may contribute to a more efficient elimination of bacteria from the periodontal environment, resulting in improvement in gingival health.
Longevity and Cariostatic Effects of Everyday Conventional Glass-ionomer and Amalgam Restorations in Primary Teeth: Three-year Results
Authors: Qvist V. , Laurberg L. , Poulsen A. , Teglers P.T.
Published: January 2009

The aim of this study was to compare the longevity and cariostatic effects of everyday conventional glass-ionomer and amalgam restorations in primary teeth. The materials consisted of 515 Ketac-Fil glass-ionomer restorations and 543 Dispersalloy amalgam restorations prepared in 666 children, from 3 to 13 years of age, by 14 dentists within the Danish Public Dental Health Service in the municipalities of Vaerlose and Hillerød. The restorations, of which 79% were of the Class II type, were in contact with 593 unrestored surfaces in adjacent primary and permanent teeth. After 3 years, 6% of the patients had dropped out of the study, and 33% of the teeth were exfoliated with the restoration in situ. A further 37% of the glass-ionomer and 18% of the amalgam restorations were recorded as failed (p < 0.001). The frequency of failures was highest for Class II glass-ionomer restorations, which showed a 50% median survival time of only 34½ months, because of many fractures, while the 75% survival time for Class II amalgam restorations just exceeded the actual 36 months (p < 0.001). Caries progression was most often recorded in surfaces adjacent to amalgam restorations, and 21% of these surfaces needed restorative treatment vs. 12% of the surfaces adjacent to glass-ionomer restorations (p < 0.01). The three-year results indicated that conventional glass ionomer is not an appropriate alternative to amalgam for all types of restorations in primary teeth. In particular, the short longevity of Class II glass-ionomer restorations could not be compensated for by the reduced caries progression and need for restorative therapy of adjacent surfaces.
Sensitivity of Periodontal Pathogens to the Bactericidal Activity of Synthetic Protegrins, Antibiotic Peptides Derived from Porcine Leukocytes
Authors: Miyasaki K.T. , Iofel R. , Lehrer R.I.
Published: January 2009

Protegrins, small peptides (1900 to 2160 daltons) isolated from porcine leukocytes, are bactericidal against a broad range of medical pathogens in vitro under conditions which reflect the extracellular milieu. The purpose of this study was to determine whether Gram-negative, facultative periodontal pathogens were sensitive to the protegrins. Synthetic L- and D-enantiomers of protegrin 1 (PG-1 and D-PG-1, respectively), and L-enantiomers of protegrins 2, 3, and 5 (PG-2, PG-3, and PG-5) were tested against Actinobacillus actinomycetemcomitans (three strains) and Capnocytophaga spp. (three strains). Strains of both A. actinomycetemcomitans and Capnocytophaga spp. were sensitive to PG-1, and exhibited ED99 (dose at which 99% killing was observed after 1 hr at 37°C) of 0.5 to 3 ug/mL and 4 to 19 ug/mL, respectively. The D-form and the L-form were equally effective. Serum (above 5% v/v) inhibited the bactericidal effects of 10 ug/mL PG-1, but the inhibitory effect was overcome by concentrations of PG-1 at 100 ug/mL. Different patterns of sensitivity were observed when the effects of PG-1, D-PG-1, PG-2, PG-3, and PG-5 were compared against A. actinomycetemcomitans and the Capnocytophaga. We conclude that protegrins may be useful antimicrobial agents in therapy against periodontal infections.
Recombinant Human Bone Morphogenetic Protein-2 Promotes Wound Healing in Rat Periodontal Fenestration Defects
Authors: King G.N. , King N. , Cruchley A.T. , Wozney J.M. , Hughes F.J.
Published: January 2009

Although there is considerable interest in the use of bone morphogenetic protein (BMP) to promote periodontal regeneration, little is known of its effects on the early stages of wound healing. The aim of this study was to investigate the effects of recombinant human bone morphogenetic protein 2 (rhBMP-2) on an early stage of post-operative wound healing and following complete healing (10 and 38 days, respectively) in a rat model of periodontal regeneration. The buccal aspects of molar roots were carefully denuded of their periodontal ligament through a bony window created in the mandibles of Wistar rats under general anesthesia. After the root surfaces were acid-conditioned, a 10-μL quantity of 50 μg/mL rhBMP-2 in a collagen gel solution was placed into the surgically created defect in test animals; in controls, either a 10-μL quantity of only collagen gel was received, or the defect was untreated. Animals were killed 10 days or 38 days after surgery and the tissues processed for histological examination. Transverse 5-um sections were stained for the identification of new bone, cementum, and collagen fiber formation. In the 10-day study groups, new bone formation over the second molar and beyond the defect was significantly increased in the test group (p < 0.02), although there was no evidence of increased ankylosis. RhBMP-2 stimulated more than twice the area of cementum growth coronally compared with controls (712 ± 286 μm2 and 258 ± 57 μm2, respectively). Connective tissue attachment, including the number and width of collagen bundles, was similar in both test and controls. Complete healing without any evidence of ankylosis had occurred in all animals 38 days postoperatively, and no significant differences were observed between test and control groups. In conclusion, a single dose of rhBMP-2 increased the rate of normal intramembranous bone formation and selectively enhanced cementum formation coronally during early wound healing. However, the finding that rhBMP-2 induced bone formation at some distance from the defect suggests the importance of developing a suitable delivery system to maintain the concentration of BMP-2 at the site of implantation for potential therapeutic use.
Variability in Cytotoxicity and Fluoride Release of Resin-modified Glass-ionomer Cements
Authors: Kan K.C. , Messer L.B. , Messer H.H.
Published: January 2009

New-generation glass-ionomer cements contain resin to improve their restorative properties. These resin-modified glass-ionomer cements vary considerably in their chemistry, which could result in corresponding variability in their physical and biological properties. This study investigated the cytotoxicity and the fluoride release of two resin-modified glass ionomers, a conventional glass-ionomer cement, and a resin composite. Samples were prepared and extracted in distilled water for 1, 4, and 7 days; eluates were filtered and tested by means of 3T3 mouse fibroblasts. Cytotoxicity (MTT assay) values were low for all materials and extraction times, indicating minimal cytotoxicity of all materials (less than 30% inhibition). Cytotoxicity of one resin-modified glass ionomer was significantly higher than for the other materials (p < 0.001). One resin-modified glass ionomer and the conventional glass-ionomer cement released significantly more fluoride at each time interval (p < 0.001) than the other resin-modified glass-ionomer cement and the resin composite. Fluoride release and cytotoxicity were correlated ( r 2 = 0.60; p < 0.001), although the fluoride release does not account for the cytotoxicity observed. Cytotoxicity and fluoride release suggest that one hybrid behaved more like a conventional glass ionomer, and the other like a resin composite. These differences may have implications for material selection in specific clinical situations.
Differential Effects of Noxious Conditioning Stimulation of the Cheek by Capsaicin on Human Sensory and Inhibitory Masseter Reflex Responses Evoked by Tooth Pulp Stimulation
Authors: Kemppainen P. , Waltimo A. , Waltimo T. , Könönen M. , Pertovaara A.
Published: January 2009

In this study, we investigated whether selective activation of nociceptive primary afferent fibers by capsaicin would induce modulations on tooth-pulp-evoked sensory or inhibitory masseter reflex responses in healthy human subjects. The contribution of central N-methyl-D-aspartate (NMDA) receptor mechanisms in capsaicin-induced effects on sensory or reflex responses was evaluated by dextromethorphan, an NMDA-receptor antagonist. The inhibitory masseter reflex was evoked by electrical stimulation (constant current, single pulses) of the upper incisor while the subject was biting at 10% of his maximal force. The sensation of the tooth pulp stimulation was evaluated by visual analogue scale (VAS). The magnitude, duration, and the latency of the reflex were determined by bite force measurements. The inhibitory masseter reflex could be induced by non-painful tooth pulp stimulation, and the inhibition was enhanced as a function of increasing stimulus intensity. Capsaicin (1%) applied topically to the skin of the cheek produced a spontaneous burning pain sensation. During capsaicin treatment, the VAS ratings for the sensation induced by tooth pulp stimulation were significantly reduced, whereas no significant changes were found in the tooth-pulp-induced masseter reflex responses. Double-blind treatment with dextromethorphan at a dose of 100 mg (= the highest dose without side-effects) had no effect on sensory or reflex responses. These data indicate that noxious stimulation of the facial skin by capsaicin induces differential effects on tooth-pulp-evoked sensory and inhibitory masseter reflex responses: Sensory responses are strongly attenuated, while masseter reflex responses are not significantly changed. Dextromethorphan at a clinically applicable dose does not influence tooth-pulp-evoked sensory or reflex responses or their modulation by capsaicin. Furthermore, the lack of modulation of the masseter reflex response by capsaicin differs from the capsaicin-induced enhancement of a nocifensive limb flexion reflex described earlier.
Effects of the D2 Receptor Agonist Bromocriptine on Sleep Bruxism: Report of Two Single-patient Clinical Trials
Authors: Lobbezoo F. , Soucy J.-P. , Hartman N.G. , Montplaisir J.Y. , Lavigne G.J.
Published: January 2009

An altered dopamine receptor status has been associated with sleep bruxism. Evidence from a functional neuro-imaging study has implicated an abnormal side imbalance in striatal D2 receptor expression in its pathophysiology. To assess the significance of this finding, we studied the effects of short-term administration of the preferential dopamine D2 receptor agonist bromocriptine on sleep bruxism in a double-blind, placebo-controlled polysomnographic and neuro-imaging study with a single crossover design. Six otherwise healthy and drug-free patients with sleep bruxism were entered into the trial. One of the patients dropped out due to an intercurrent illness, while three others were discontinued from the study due to severe adverse reactions to bromocriptine. Because of the high frequency and intensity of the side-effects, the trial was interrupted. Two patients, however, completed the trial without any adverse reactions. Their outcome measures are presented as single-patient clinical trials. Following a two-week administration of bromocriptine, both patients showed a decrease in the number of bruxism episodes per hour of sleep of about 20% to 30% with respect to the placebo. While no significant differences between both conditions (i.e., placebo and bromocriptine) were found for the number of bruxism bursts per episode, significantly lower root-mean-squared EMG levels per bruxism burst occurred during bromocriptine use. In association with this polysomnographically established attenuation of sleep bruxism, bromocriptine afforded a decreased abnormal side distribution of striatal D2 receptor binding, as was evidenced by single-photon-emission computed tomography using the radioactive D2 receptor antagonist iodine-123-iodobenzamide. This study supports previous suggestions that the central dopaminergic system may be involved in the modulation of sleep bruxism.

To see if the present findings apply across a population, investigators should use a peripheral D-2 antagonist to prevent side-effects.