bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Malnutrition on Caries Development and Saliva Composition in the Rat
Authors: Johansson I. , Ericson T. , Bowen W. , Cole M.
Published: November 2010

The purpose of this study was to investigate the effect in rats of malnutrition on caries development and on some antibacterial substances in saliva. By gastric intubation, two groups of ten rats each were fed a liquid basic diet (100% diet), and two similar groups were fed the basic diet diluted with an equal volume of water to contain 50% of the nutrients of the basic diet (50% diet). One group on undiluted and one group on the diluted basic diet were offered sucrose as a supplement by mouth 17 times daily, using a programmed feeding machine, and the other two groups were offered starch in a similar manner. The extent and depth of the caries lesions were five times greater in the low-nourished (50% diet) sucrose group in comparison with the group given the undiluted diet supplemented with sucrose. The 50% diet group ate more frequently from the offered supplement. The 50% diet induced lower salivary lactoperoxidase activities, and there was an additive effect of starch as supplement. Higher concentrations of sIgA were found in the saliva of animals fed the 50% diet supplemented with sucrose than in those fed sucrose and the 100% diet. Significantly greater levels of sIgA and IgG were found in the saliva from the 50% diet-sucrose group than in the 50% diet-starch group. Plaque scores differed slightly but not significantly between the groups. The starch group receiving 100% diet showed a slightly lower level of S. mutans infection as compared with the 50% diet-starch group; the caries scores in the starch groups did not differ.
The Effect of Class II Elastic Forces on Craniofacial Growth in Rats
Authors: Bakker V.M. , Johnston L.E.
Published: November 2010

Full-time Class II elastic forces were applied to eight rats in order to evaluate their effects on the growth of the snout and the mandible. Eight animals served as controls. Lateral cephalograms were taken at the start of the experiment and again at the end, 23 days later. The pre- and post-treatment tracings were superimposed on the cranial base to measure alterations in snout growth, and on metallic implants to measure differences in mandibular growth.

As judged by t tests, Class II elastic forces caused a significant antero-posterior growth inhibition both in the snout and in the mandible.
Alpha Tocopherol Alters the Distribution of Langerhans Cells in DMBA-treated Hamster Cheek Pouch Epithelium
Authors: Schwartz J. , Odukoya O. , Stoufi E. , Shklar G.
Published: November 2010

Thirty-seven adult male and female golden hamsters (Mesocricetus auratus) were divided into four experimental groups. In Group A, the animals served as untreated controls, having the left buccal pouches painted with mineral oil. In Group B, the animals received 10 mg vitamin E (alpha tocopherol) in peanut oil by the oral route, with a fine pipette, twice weekly. In Group C animals, the left buccal pouch was painted three times weekly with DMBA (0.5% solution of 7,12 dimethylbenz(a)anthracene in heavy mineral oil). Group D animals received both vitamin E and DMBA in the amounts indicated for Groups Band C, with the vitamin E being administered on days alternate to the DMBA painting, also in the manner described for the above groups. All animals were killed after eight weeks of treatment. Epithelial whole mounts were prepared from the left buccal pouches. These specimens were then stained for ATPase to demonstrate the presence of Langerhans cells (LCs). A notably decreased density of LCs was observed after treatment with DMBA. Vitamin E administration in addition to DMBA treatment resulted in a less dramatic decrease in LC density. Since vitamin E has been shown to retard experimental oral carcinogenesis, vitamin E may retard carcinogenesis by maintaining the number of Langerhans cells.
Properties of Microfilled Composite Resins as Influenced by Filler Content
Authors: Germain H. St. , Swartz M.L. , Phillips R.W. , Moore B.K. , Roberts T.A.
Published: November 2010

Two series of composite resins were prepared with a light-cured urethane dimethacrylate matrix to which varying amounts of two types of silanated silica particles were added. One series contained volume fractions ranging from 15.8 to 28.8% silica particles of 20 nm in diameter (Type I filler) and the other series volume fractions of from 24 to 49.4% of an agglomerated silica particle of 40 nm in diameter (Type II filler). Tests were conducted to determine the effect of filler level on: depth of cure as determined by hardness measurements; color stability in both UV light and water; water sorption with time; hardness; compressive strength; strain behavior in slow compression; and resistance to toothbrush abrasion and wear by hydroxyapatite. Analysis of the data obtained for these two micro filled series indicate that increased filler levels result in trends for increased depth of cure, color stability, hardness, compressive strength, and stiffness, while water sorption and resistance to both toothbrush abrasion and wear by hydroxyapatite were reduced. These trends were more pronounced for the Type II filler series than for the Type I filler series. However, there was a greater differential in filler levels within the Type II series than within the Type I series.
An Erosion Test for Dental Cements
Authors: Walls A.W.G. , McCabe J.F. , Murray J.J.
Published: November 2010

A new method for the in vitro measurement of the erosion of dental cements is described which allows repeated, gentle removal of loose surface debris and provides a direct quantitative measurement of material lost. A linear relationship for erosion against time is demonstrated for a glass polyalkenoate material under mildly acidic conditions. This test method is applicable to all acid/base-type cements and gives results comparable to those from in vivo tests.
Dental Plaque Toxins are not Lymphotoxins
Authors: Levine M.
Published: November 2010

A major portion of the toxic activity of plaque extracts to cells in culture is due to macromolecules which might be lymphotoxins derived from antigen or mitogen-activated lymphocytes in the gingiva. Assays of sensitivity to aL929 and HeLa cells, and of the effect of neutralizing antibody, indicated that the plaque toxins did not have the properties of the lymphotoxins. The results are consistent with other findings and suggest that the toxins are microbial exotoxins.
The Bond Strength of Composite Laminate Veneers
Authors: Walls A.W.G. , McCabe J.F. , Murray J.J.
Published: November 2010

An in vitro model has been developed simulating a composite laminate veneer restoration, along with methods to mimic the environmental conditions to which these restorations are subjected in vivo. Fifty composite laminate specimens were prepared: Ten were left untreated as controls, and 40 were exposed to simulated environmental conditioning. The tensile bond strength of the veneer-to-composite interface was significantly reduced by both thermal and humidity cycling, which may explain the increasing prevalence of marginal failure and staining which occurs as these restorations age in vivo.
Fluoride Uptake and Retention at Various Stages of Rat Molar Enamel Development
Authors: Bawden J.W. , McLean P. , Deaton T.G.
Published: November 2010

Suckling rat pups were given intraperitoneal fluoride injections at selected ages so that we could study fluoride uptake in the enamel of the maxillary first molar at various stages of enamel development. Plasma fluoride levels in six-day-old and 11-day-old pups were monitored following the intraperitoneal injection of fluoride. The findings indicate that: (1) fluoride was more easily taken up and retained during the early stages of enamel formation, but fluoride uptake can occur during all stages of enamel formation; (2) when injections were started early in enamel formation, more fluoride was contained in the enamel of the maxillary first molar at 13 days of age; and (3) the same dose of fluoride per gram body weight resulted in greater exposure to elevated plasma fluoride levels in six-day-old pups than in 11-day-old pups.
Examiner Reliability in Dental Radiography
Authors: Valachovic R.W. , Douglass C.W. , Berkey C.S. , McNeil B.J. , Chauncey H.H.
Published: November 2010

In long-term investigations involving a large number of study participants, it is frequently necessary to employ the use of multiple examiners who must exhibit high levels of inter- and intra-examiner reliability in order to minimize examiner bias, which can distort scientific findings. This report on the calibration of four examiners in a large project investigating the efficacy of dental radiography shows high levels of examiner reliability using various statistical measures of agreement. Levels of intra-examiner agreement using Cohen's Kappa index were 0.75 and higher at baseline, and remained at approximately the same level (0.80) throughout the 24-month period of the study. The Kappa index of inter-examiner agreement among the six pairings of the four examiners ranged from 0.68 to 0.80 for caries and 0.72 and 0.83 for periodontal disease. Values of four statistical measures of agreement (proportional agreement, Kendall's rank correlation, Cohen's Kappa index, and Cohen's weighted Kappa index) were determined to show the importance of using measures, such as the Kappa index, which take chance agreement into account.
Separation and Properties of Rabbit Buccal Mucosal Wound Hyaluronidase
Authors: Bertolami C.N. , Day R.H. , Ellis D.G.
Published: November 2010

This study establishes the existence of a mammalian buccal mucosal wound hyaluronidase (hyaluronate 4-glycohydrolase; EC 3.2.1.35) having properties distinct from those of the endogenous lysosomal hyaluronidase of normal (uninjured) buccal mucosa. A time-dependent change in hyaluronidase activity was measured, with the highest specific activity occurring on post-wound day 4 (7.7 ± 1.3 unitslmg protein), followed by consecutive decreases until activity was no longer discernible by day 21. Mucosal wound hyaluronidase closely resembled a previously described integumentary wound endoglycosidase in terms of a high pH optimum (5.0-6.0), distinct (but non-exclusive) substrate preference for hyaluronic acid, and ability to generate saturated depolymerization products by an endoglycosidic hydrolysis.
A Histological Assessment of the Initial Healing Response Adjacent to Porous-surfaced, Titanium Alloy Dental Implants in Dogs
Authors: Deporter D.A. , Watson P.A. , Pilliar R.M. , Melcher A.H. , Winslow J. , Howley T.P. , Hansel P. , Maniatopoulos C. , Rodriguez A. , Abdulla D. , Parisien K. , Smith D.C.
Published: November 2010

We report here the results of a histological assessment of the initial healing response following implantation into the dog mandible of a porous-surfaced, titanium alloy endosseous dental implant. Two implants were placed in edentulous areas on each side of the mandible of each dog and covered with a full-thickness mucoperiosteal flap. The implant sites on one side of the mandible were allowed to heal for four weeks, while those on the other side were allowed to heal for eight weeks before the animals were killed. Histological specimens were obtained and assessed both qualitatively and by computer-assisted morphometry. All but one of the 24 implants were well-tolerated and healed with a variable ingrowth of bone into the porous-surface geometry. The histomorphometric measurements revealed that bone ingrowth had reached a plateau by four weeks of initial healing.
An Ultrastructural Study of Tooth Resorption in the Kitten
Authors: Ten Cate A.R. , Anderson R.D.
Published: November 2010

Eleven kittens of various ages were used to obtain teeth in situ at differing stages of exfoliation. The teeth were processed by routine techniques for examination by light and transmission electron microscopy. The dental hard tissues were eroded by odontoclasts supported by numerous blood vessels, fibroblasts, and macrophages. No evidence of intracellular collagen was found within any of these cells, indicating that helper cells are not required to remove the collagenous component of dentin and cementum. The loss of periodontal ligament during shedding involved the removal of cells and extracellular material. Two forms of fibroblastic cell death were identified: One, apoptotic cell death, involved condensation, and its occurrence suggests that exfoliation of deciduous teeth is a programed physiological event; the other occurred in cells containing many profiles of collagen and involved the selective disruption of the mitochondria and eventual dissolution of cytosol. This form of cell death has not been previously described and is significantly different from necrotic cell death, which was not observed during exfoliation. Some fibroblasts maintained a normal morphology. These various cellular responses suggest that phenotypically different populations of fibroblasts may exist in the periodontal ligament. Collagen removal was an extracellular occurrence which did not seem to involve increased phagocytotic activity by fibroblasts.
Interaction of Salivary Fibronectin with Oral Streptococci
Authors: Babu J.P. , Dabbous M.K.
Published: November 2010

Immunoreactive Fibronectin (Fn) has been demonstrated in stimulated human parotid saliva by western blot analysis and also found to be a component of the artificial tooth pellicles derived from hydroxyapatite (HA) beads coated with parotid saliva. Saliva depleted of gelatin-binding components showed a significantly lower degree of reactivity with anti-Fn antibodies than did the control saliva when tested by an enzyme-linked immunosorbent assay ( ELISA) . Depletion of gelatin-binding components from saliva was also found to affect the degree of saliva-mediated aggregation of four of the seven oral streptococci tested [Streptococcus mutans strains GS-5 and OMZ 176, S. sobrinus, and S. rattus]. Similarly, the adherence of the same four micro-organisms to the artificial tooth pellicles (derived from saliva which had previously been depleted of gelatin-binding component) was significantly inhibited ( 37-53%) when compared with the control saliva-coated HA beads. Pre-treatment of streptococci with 100 μg of soluble Fn also caused a 34—57% inhibition of adherence of the same oral streptococci to saliva-treated HA beads. Quantitation of Fn in human parotid saliva showed that the amounts of immunoreactive Fn varied from 2 to 6 μg/mL of parotid saliva. Furthermore, the Fn from parotid saliva was found to be adsorbed onto the bacterial surfaces, as demonstrated by immunofluorescence and ELISA. The presence of Fn in parotid saliva and its ability to bind to HA beads (artificial pellicles), in conjunction with the ability of soluble Fn to inhibit the adherence of streptococcal strains to the artificial tooth pellicles, suggest that the microbial ecology of the oral cavity may, in part, be influenced by the interactions mediated by salivary fibronectin.
Standardizing Evaluations of the Clinical Marginal Fracture of Amalgam
Authors: Mahler D.B. , Engle J.H. , Bryant R.W.
Published: November 2010

In this study, we investigated both inter-examiner and intra-examiner differences in the evaluation of the marginal fracture characteristics of dental amalgam restorations. Evaluations were made by matching intra-oral photographs of the occlusal surfaces of clinical restorations to a reference set of clinical photographs illustrating increasing amounts of marginal fracture. Four amalgam alloys and five examiners provided the data base. Differences in marginal fracture indices were found among examiners and between evaluation times for the same examiners. However, these differences were reduced significantly after application of a standardization procedure.
Arylaminopeptidase Activities of Oral Bacteria
Authors: Suido H. , Nakamura M. , Mashimo P.A. , Zambon J.J. , Genco R.J.
Published: November 2010

Protease and peptidase enzymes are thought to play a role in the virulence of many oral organisms, especially those associated with periodontal diseases. In order to evaluate the peptidases of periodontopathogens, we compared the arylaminopeptidase activities of Bacteroides gingivalis with those of other oral and non-oral bacteria. Sixty-three bacterial strains representing the prominent cultivable organisms in human periodontal pockets were tested, including representatives of the black-pigmented Bacteroides, Actinobacillus, Actinomyces, Campylobacter, Capnocytophaga, Eikenella, Fusobacterium, Haemophilus, Lactobacillus, Streptococcus, and Veillonella species. Each micro-organism was examined for its ability to hydrolyze 18 synthetic substrates of β-naphthylamide derivatives of amino acids, dipeptides, and tripeptides. Quantitation of the enzyme activity was accomplished by colorimetric measurement of the amounts of released β-naphthylamines.

N-CBz-glycyl-glycyl-L-arginine-β-naphthylamide was readily cleaved by B. gingivalis, but slightly or not at all by the other oral strains tested. L-arginine-β-naphthylamide was cleaved by B. gingivalis, Capnocytophaga species, and Streptococcus species, but not readily by the other Bacteroides strains. Some dipeptide substrates tested, such as glycyl-L-arginine- and glycyl-L-proline-β-naphthylamide, were strongly cleaved by B. gingivalis and weakly cleaved by other Bacteroides strains.

Since high levels of N-CBz-glycyl-glycyl-L-arginyl-aminopeptidase activity are characteristic of B. gingivalis, its measurement may be valuable in the identification of this organism in clinical samples as an aid in diagnosis and monitoring of periodontal infections. Furthermore, this and other aminopeptidases produced by B. gingivalis and other oral organisms may play a role in the tissue destruction seen in periodontal disease.
1985 Kreshover lecture. Molecular Factors Influencing Neutrophil Defects in Periodontal Disease
Authors: Genco R.J. , Van Dyke T.E. , Levine M.J. , Nelson R.D. , Wilson M.E.
Published: November 2010

Major advances in our understanding of the role of the neutrophil in host defense against periodontal organisms have been made through studies of localized juvenile periodontitis (LJP). Several.lines of evidence suggest that LJP is an infectious process closely associated with Actinobacillus (Haemophilus) actinomycetemcomitans as a causative agent, although other organisms may also participate. The immunologic profile of LJP patients suggests that a cell-associated neutrophil locomotory dysfunction is a key underlying immunodeficiency resulting in increased susceptibility to periodontal infection. In addition, LJP patients often exhibit cervical lymphadenopathy and IgG-hypergammaglobulinemia, and a markedly elevated antibody response to the infecting organism, A. actinomycetemcomitans, is found in the serum and crevicular fluid of most patients.

Evaluation of the locomotory properties of LJP neutrophils shows that random migration and chemokinesis are normal; however, about 70% of the LJP patients suffer from a defect in chemotaxis, with their neutrophils responding poorly to bacterial chemotaetic factors, synthetic chemotactic peptides, and complement fragments (C5a). Depressed chemotaxis of LJP neutrophils is paralleled by their reduced capacity to bind the synthetic chemotactic peptide N-formylmethionylleucylphenylalanine (FMLP), as well as C5a. Furthermore, there is a reduction in the amount of glycoprotein 110, a neutrophil membrane matrix component and differentiation antigen which is associated with FMLP- and possibly also C5a-mediated chemotaxis. Reduction ofC5a and of FMLP ligand binding, decreased expression of GP-110, and reduced neutrophil chemotaxis are consistent with a stem cell maturation error in LJP patients. This is further supported by studies demonstrating increased expression of CR2, the C3d/EBV receptor, on peripheral blood neutrophils of LJP patients. CR2 receptors are normally present on immature human neutrophils but are lost during the maturation process.

These alterations in neutrophil surface components and their reduced chemotaxis may result from a genetically determined abnormality. Studies demonstrating the familial nature of both the neutrophil chemotactic disorder and the clinical entity represented by localized juvenile periodontitis point to a strong role for genetic determinants in the disease which affect neutrophil surface receptors.
Food Cariogenicity in Americans Aged from 9 to 29 Years Assessed in a National Cross-sectional Survey, 1971-74
Authors: Ismail A.I.
Published: November 2010

The purpose of this study was to investigate the association between the probability of having high DMFT scores and reported consumption of eight food groups. The sample included Americans (aged from 9 to 29 years) examined during the first National Health and Nutrition Examination Survey conducted between 1971 and 1974. Analysis was restricted to comparing those individuals having DMFT scores equal to or above the 80th percentile of the DMFT distribution with those having scores equal to or below the 20th percentile of the distribution.

The strongest discriminator between the low- and high-DMFT groups was the between-meal consumption of table sugars and syrups. The between-meal consumption of sugary desserts was also significantly associated with high DMFT scores. Foods to which table sugars are usually added before consumption, such as coffee, chocolate, and tea drinks, were associated with high DMFT scores in the bivariate analysis. When the same-day consumption of table sugars and syrups was accounted for, the associations became nonsignificant. The reported consumption of breakfast cereals, bread, fruit juices, ice cream, and nuts and crackers was not associated with high DMFT scores, perhaps because they were consumed only infrequently.
An Epidemiological Investigation into the Relative Importance of Age and Oral Hygiene Status as Determinants of Periodontitis
Authors: Abdellatif H.M. , Burt B.A.
Published: November 2010

The objective of this study was to assess the relative effects of age and oral hygiene on the progression of periodontitis by estimating incidence from age-specific prevalence. This study analyzed data from a representative national sample of 14,690 dentate Americans, aged from 15 to 74, seen in the first National Health and Nutrition Examination Survey (NHANES 1) in 1971-1974. Results showed that the rate of increase in the estimated incidence of periodontitis with age, throughout all age groups, is much higher among subjects with poor oral hygiene than among those with good oral hygiene. Oral hygiene was confirmed as the most important predictor for periodontitis; in all age groups, more than 95% of those examined with good oral hygiene did not have periodontitis. It was concluded that the effect of age on the progression of periodontitis could therefore be considered negligible when good oral hygiene is maintained.
Immunochemical and Biochemical Studies of Human Enamel Proteins during Neonatal Development
Authors: Zeichner-David M. , Macdougall M. , Vides J. , Snead M.L. , Slavkin H.C. , Turkel S.B. , Pavlova Z.
Published: November 2010

The present communication provides descriptions of the developmental, biochemical, and immunological properties of the human enamel extracellular matrix proteins. We report the isolation and partial characterization of the major human enamel proteins, the production of polyclonal antibodies directed against the human enamelins, and a comparison between the immunogenicity of enamelins and amelogenins from human and mouse enamel extracellular matrices. Our results indicate that although enamelins and amelogenins share some epitopes, each one of these proteins appears to invoke a different degree of immunogenicity.
Transcapillary Transport during Secretion by the Rabbit Submandibular Salivary Gland
Authors: Smaje L.H. , Gamble J.
Published: November 2010

Fluid exchange in the rabbit submandibular gland has been studied with a view to improving understanding of the mechanisms underlying transcapillary transport during salivation. Using maximally vasodilated glands perfused in vitro, we found that acetylcholine had no signijicant effect on either hydraulic conductance (filtration coefficient, Lp) or reflection coefficient to albumin (σalb) of the gland microvessels. In vivo, parasympathetic nerve stimulation increased blood flow 20-fold, interstitial fluid production (total fluid efflux - saliva fTow) increased approximately 10-fold, while filtration fraction remained constant. At the same time, isogravimetric capillary pressure increased about six-fold. There are several possible explanations for these findings, and it is argued that they are likely to include capillary recruitment. Thus, during salivation, parasympathetic nerve stimulation does not lead to a change in capillary permeability as such, but rather produces a relaxation of resistance vessels and a fall in precapillary resistance, accompanied by an increase in available capillary surface area. This leads to a rise in capillary blood flow and pressure, which in turn increase fluid filtration. These changes are self-limiting due to the resulting dilution of interstitial protein and rise in interstitial pressure, but during salivation, since the secretion is pumped out of the interstitium, this fluid transport has no net effect on transcapillary gradients.
Antimicrobial Action of New, Proprietary Lining Cements
Authors: McComb D. , Ericson D.
Published: November 2010

The antibacterial activity of innovative, commercial lining cements was investigated. A liner which contains calcium hydroxide and is polymerized by visible light (Prisma VLC Dycal) and a glass-ionomer lining cement (GC lining cement) were compared with two more es tablished lining cements (Advanced Formula II Dycal and Life). Antibacterial activity and hemolysis-like agar change at 24, 48, and 72 hours were measured on blood agar plates inoculated with Streptococcus mutans KPSK 2 (serotype c), Lactobacillus casei ssp rhamnosus ATCC 11981, and chewing-stimulated saliva.

Prisma VLC Dycal did not affect bacteria or agar. The glass-ionomer lining cement, with an acidic pH at setting, had the most pronounced effect on all test organisms and on the agar. Even after 48 hours' setting, it inhibited growth of S. mutans. The control lining cement (AFII Dycal) showed antibacterial activity toward both specific micro-organisms as well as some activity against the salivary organisms. The material Life showed only partial inhibition of microbial growth. For all lining cements, the hemolytic-like agar change correlated with antibacterial effects.

The surface pH of the freshly-set cements containing calcium hydroxide was alkaline. It would seem that a simple correlation between high surface pH and antibacterial activity among these cements does not exist. Also, further biological characterization of new lining cements is required to direct their appropriate clinical use.
Bacteriology of Human Gingivitis
Authors: Moore L.V.H. , Moore W.E.C. , Cato E.P. , Smibert R.M. , Burmeister J.A. , Best A.M. , Ranney R.R.
Published: November 2010

The subgingival bacterial floras of naturally occurring gingivitis in adults and children were characterized and compared with the floras of other periodontal conditions previously studied. The composition of the gingivitis floras was found to be distinct from that of floras associated with health or with moderate, severe, or juvenile periodontitis. There were no major differences between the floras of naturally-occurring gingivitis and the floras of the human experimental gingivitis model. Data indicated that the flora of healthy sites within a mouth is influenced by the number of inflamed sites, which argues against independence of sites bacteriologically. Proportions of ten bacterial species increased in both gingivitis and periodontitis, as compared with health, in both adults and children. These species were found in both affected and unaffected sites of people with gingivitis. The numbers of five other cultivable species and the "large treponeme", which was not cultivated, increased in gingivitis and periodontitis of adults only.

Significant differences in non-spirochetal floras between children and adults were not found, although they were in the experimental gingivitis model studied previously. Cultivable spirochetes did differ between children and adults. Children had fewer samples positive for spirochetes, and children's positive samples contained greater proportions of T. socranskii subsp. paredis.

Some species that predominate in periodontitis, but which are absent from healthy gingivae, were found as a small percentage of the flora in gingivitis. This suggests that increased serum and blood in the gingival crevice encourage species that relate to periodontitis.
An Investigation into the Fracture Behavior of a Particulate-filled bis-GMA Resin
Authors: Davis D.M. , Waters N.E.
Published: November 2010

Dental composites are being increasingly used to restore occlusal surfaces of posterior teeth. If these restorations are not to fracture in service, an understanding of their fracture behavior is essential. The fracture parameter used is the stress-intensity factor at crack instability (KIC). This has been calculated by means of the double-torsion test in a mechanical testing machine.

The fracture behavior of the composite was studied by varying: the amount of filler (7%, 15%, 26%, and 41% by volume); the surface treatment of the filler (coated or uncoated); the environment (air and water); and the cross-head rate (0.05, 0.5, 5, and 50 mmlmin).

Fracture was found to occur in either a continuous (stable) or stick-slip (unstable) manner. The stick-slip behavior was due to blunting of the crack tip, which was controlled by the yield behavior. When there was no significant blunting, continuous crack growth occurred. An unique relationship was found to exist between the yield stress and the stress-intensity factor for all conditions of testing.
Ultrastructure of Extracellular Polysaccharides Produced by Serotype c Streptococcus mutans
Authors: Toda Y. , Moro I. , Koga T. , Asakawa H. , Hamada S.
Published: November 2010

The ultrastructure of extracellular polysaccharides produced in colonies by two clinical isolates and that of a nitrosoguanidine-induced mutant of serotype c Streptococcus mutans with different polysaccharide-synthesizing abilities were compared electron-microscopically. A large amount of polysaccharide was produced from sucrose by colonies of typical serotype c strain MT8148R and a clinical variant MT6801R with an enhanced fructan-synthesizing ability. Transmission electron-microscopy (TEM) revealed that the polysaccharides consisted of three structural components, i.e., globular, single-stranded filamentous, and double-stranded fibrillar structures. These structures were ascribed to production of fructan, water-soluble glucan, and water-insoluble glucan, respectively. On the other hand, two kinds of structures, a globular body and an amorphous substance, were observed by scanning electron-microscopy (SEM). The former was composed of fructan, while the latter contained a mixture of water-soluble and water-insoluble glucans which formed filamentous and double-stranded fibrillar structures under TEM. Very small quantities of polysaccharides were formed in colonies of mutant NG7183, which was derived from S. mutans MT6801R. This strain was found to possess low glucan- and no fructan-synthesizing abilities. The polysaccharides produced in colonies of mutant NG7183 were composed only of filamentous and double-stranded fibrils under TEM. A small amount of amorphous substance was observed by SEM in colonies of NG7183.
In vitro Infection and of Dentinal Tubules
Authors: Haapasalo M. , Ørstavik D.
Published: November 2010

An in vitro model for dentinal tubule infection of root canals was developed. Cylindrical dentin specimens, 4 mm high with a diameter of 6 mm and a canal 2.3 mm wide, were prepared from freshly extracted bovine incisors. The cementum was removed from all dentin blocks. The tubules were opened by four-minute treatments with 17% EDTA and 5.25% NaOCI before being infected with Enterococcus faecalis ATCC 29212 in yeast extract-glucose broth. Bacteria rapidly invaded the tubules. After three weeks of incubation, a heavy infection was found 400 μm from the canal lumen, and the front of the infection reached 1000 μm in some blocks. Camphorated paramonochlorophenol (CMCP) and a calcium hydroxide compound, Calasept®, were tested for their disinfecting efficacy toward E. faecalis- infected dentin. Liquid CMCP rapidly and completely disinfected the dentinal tubules, whereas CMCP in gaseous form disinfected tubules less rapidly. Calasept® failed to eliminate, even superficially, E. faecalis in the tubules. The method used in bacteriological sampling allowed for sequential removal of 100-μm-thick zones of dentin from the central canal toward the periphery. Control specimens were uniformly in fected and yielded growth in bur samples up to some 500 μm from the surface. The model proved quite sensitive and seems suitable for in vitro testing of root canal medicaments.
Clinical Results After 12 Months from a Study of the Incidence and Progression of Dental Caries in Relation to Consumption of Chewing-gum Containing Xylitol in School Preventive Programs
Authors: Kandelman D. , Gagnon G.
Published: November 2010

This study was designed to evaluate the effect of chewing-gum containing xylitol on the incidence and the progression of dental caries.

A sample of 433 children, aged 8 and 9 years, of low socio-economic status and high caries rate, was divided into two experimental groups (15% or 65% xylitol chewing-gum distributed three times a day at school) and one control group (without chewing-gum). The three groups were exposed to the same basic preventive program.

Children who chewed gum had a significantly smaller DMF(S) increment over a 12-month period than did the control group. The former had increments of 1.58 surfaces, compared with 3.28 for the latter. No statistically significant difference, however, was demonstrated between the two experimental groups.

The net progression of decay (progressions-reversals) showed a significant difference between the two experimental groups and the control group. In addition, 65% xylitol chewing-gum produced better results than did that containing 15% xylitol, suggesting a dose-response relationship. Chewing xylitol gum had a beneficial effect on the caries process for all types of tooth surfaces, but chewing gum with a higher xylitol content had an additional positive effect on buccolingual surfaces.

A questionnaire asking the participants about stomach pain indicated that there was no difference between the experimental and control groups.

The feasibility of such a preventive measure has been demonstrated by the excellent level of participation of both children and teachers. This activity could easily be integrated into existing preventive public health programs.
Fluoride in Saliva and Plaque Following Use of Fluoride-containing Mouthwashes
Authors: Duckworth R.M. , Morgan S.N. , Murray A.M.
Published: November 2010

The sensitivity of methodology for measuring the concentration of fluorine species in saliva and in plaque has been tested. Human subjects mouth-rinsed daily with aqueous solutions of NaF and Na2FPO3. Samples of unstimulated whole saliva and of plaque were collected twice weekly at least 18 hr after treatment application. Oral fluoride concentrations rose from placebo values for approximately two weeks before attaining equilibrium and returned to baseline when daily mouthrinsing was stopped. Mean elevated oral fluoride concentrations increased significantly with increasing applied NaF concentration in the range 0-1000 ppm F (0-0.053 mol/L). There appeared to be a linear relationship between saliva and plaque fluoride. The ability of fluoride treatments to sustain elevated oral fluoride levels between daily applications may be of major importance in caries control.
Adhesive 4-META/MMA-TBB Opaque Resin with Poly(methyl methacrylate)-coated Titanium Dioxide
Authors: Matsumura H. , Nakabayashi N.
Published: November 2010

An adhesive opaque resin for veneering on cast metal was developed with 4-methacryloxyethyl trimellitate anhydride and poly (methyl methacrylate)-coated titanium dioxide prepared by aqueous phase polymerization. The opaque resin was a modified 4-META/MMA-TBB resin. The powder consisted of 20% of the encapsulated material and 80% PMMA instead of pure PMMA powder. This resin hides the metal color when the thickness of the resin is as thin as 50 μm. The opaque resin bonded strongly to both cobalt-chromium alloy and visible-light-cured veneering resin. This self-curing opaque resin is applicable not only for bonding veneering resin to an alloy surface but also for bonding fixed partial dentures to enamel surfaces.
The in vitro Uptake of Fluoride by Secretory and Maturation Stage Bovine Enamel
Authors: Fridell R.A. , Lussi A. , Crenshaw M.A. , Bawden J.W.
Published: November 2010

The objectives of this study were to determine the specific surface area of secretory-stage and of maturation-stage enamel, to compare the fluoride uptake by isolated enamel at these two stages on a surface-area basis, and to examine the effect of the organic matrix on the fluoride uptake by whole enamel. Fetal bovine secretory and maturation stage enamel samples were collected, and a portion of the enamel at each developmental stage was treated with hydrazine for removal of the organic matrix. The specific surface areas of the enamel mineral, as determined by the multi-point BET method, were 59.3 m2/ g in the secretory stage and 37.9 m2/g in the maturation stage. Whole and deproteinated enamel samples were equilibrated in buffered solutions containing 10 -5 to 10-3 mol/L fluoride, and the uptake was measured with a fluoride specific electrode. The results indicate that the in vitro fluoride uptake was controlled solely by the surface area of the apatitic mineral and that the organic matrix did not contribute to the fluoride uptake.
Homology of Glucosyltransferase Gene and Protein Sequences from Streptococcus sobrinus and Streptococcus mutans
Authors: Russell R.R.B. , Shiroza T. , Kuramitsu H.K. , Ferreti J.J.
Published: November 2010

The sequences of glucosyltransferase genes from Streptococcus sobrinus (gtfI) and Streptococcus mutans (gtfB) were compared and show a high degree of homology. There is a 57.7% homology of nucleotides in the genes and a 56. 7% homology of amino acids in the deduced protein sequences. The G + C content for the protein-coding region is 43.6% for S. sobrinus and 41.2% for S. mutans. Internal repeating sequences present in both proteins exhibit some difference in sequence pattern.
An in vitro Evaluation of Artificial Caries-like Lesions on Restored Overdenture Abutments
Authors: Kambhu P.P. , Ettinger R.L. , Wefel J.S.
Published: November 2010

An acidified dialyzed gelatin gel system was used to determine the caries resistance of a variety of restorative materials used to obturate the canal orifice of overdenture abutment teeth. The restorative materials used were Tytin, Tytin + Copalite, P30 + Scotchbond, Fuji Ionomer-Type II, and Miracle Mix. Polarized light microscopy and microradiography were used to examine the caries-like lesions adjacent to the restorations. The lesions formed in the Fuji Ionomer-Type II and Miracle Mix groups appeared arrested at the wall adjacent to the restoration, and did not penetrate apically down the wall as did those associated with the other restorative materials. The mean depths of lesions adjacent to Fuji Ionomer-Type II and Miracle Mix restorations were significantly less than those of Tytin, Tytin + Copalite, or P30 + Scotchbond.
The Effect of Varying Diagnostic Thresholds upon Clinical Caries Data for a Low Prevalence Group
Authors: Pitts N.B. , Fyffe H.E.
Published: November 2010

This study investigated the impact of employing differing diagnostic thresholds on clinical caries data in studies of groups with low caries prevalence. Data from clinical examinations of 287 Hong Kong dental students were analyzed by means of the CARIES microcomputer software package. This software allows for re-calculation of raw data according to three different diagnostic thresholds (D3, D2, and D1). When "enamel" and "initial" lesions (as defined by WHO criteria) were included in the calculation of DMFT, its value increased from 3.0 (D3) to 5.9 (D1), while the percentage of individuals considered "caries-free" decreased from 28.2% to 7.0%. Little change was found in the magnitude of the intra-examiner reproducibility, when calculated at each threshold, for a random 10% of the subjects. It was unfortunately not possible to calculate inter-examiner reproducibility in this study. The use of criteria which might be misinterpreted as being similar, but which use differing effective diagnostic thresholds, can dramatically influence the reported level of dental caries. In view of these findings, it may be necessary for the question of diagnostic thresholds to be re-examined and to receive greater emphasis in future studies.
Effects of Rinses with an Acidic Calcium Phosphate Solution on Fluoride Uptake, Caries, and in situ Plaque pH in Rats
Authors: Schreiber C.T. , Shern R.J. , Chow L.C. , Kingman A.
Published: November 2010

The effects of oral rinses on enamel fluoride uptake, caries, and plaque pH in rats were investigated by use of (1) an acidic calcium phosphate solution (CPS) saturated with dicalcium phosphate dihydrate (DCPD) and (2) a 1% fluoride solution.

Osborne-Mendel rats, 19 days of age, were randomly assigned to one of four mouth-rinse treatment groups, with the two consecutively administered rinses being: H2O-H 2O; H2O-F; CPS-H20; and CPS-F. The treatments were administered on days 1 through 4, and the animals were provided with a cariogenic challenge throughout the study.

The groups treated with F exhibited significantly higher mean levels of enamel-bound F than did the non-F groups. Furthermore, CPS significantly increased uptake of F by enamel when used as an adjunct to the F treatment. The caries scores of the CPS-F and H2O-F groups were not statistically different; however, a strong negative correlation was observed between enamel F content and caries scores, indicating that as more F was incorporated into the teeth, less caries formation occurred. Despite the significant differences in enamel F and caries scores among some of the treatment groups, post mortem in situ plaque pH drop in response to a sucrose rinse showed no differences among these groups.
Correlations between Gingival Crevicular Fluid Enzymes and the Subgingival Microflora
Authors: Suido H. , Zambon J.J. , Mashimo P.A. , Dunford R. , Genco R.J.
Published: November 2010

Bacteroides gingivalis is a Gram-negative micro-organism implicated in the pathogenesis of adult periodontitis and producing relatively large amounts of specific enzymes. In the present study, subgingival samples taken from adults with moderate periodontitis were examined for the presence and relative amounts of enzymatic activity toward certain substrates. Enzyme levels were then correlated with clinical periodontal indices and microbiological analysis of subgingival plaque, including darkfield microscopy for bacterial morphotypes and immunofluorescence microscopy for B. gingivalis and Bacteroides intermedius.

The results of this study indicate a significant positive correlation between levels of enzyme capable of degrading N-benzoyl-D,L-arginine-β -naphthylamide hydrochloride, and subgingival B. gingivalis (r = 0.55). There was a much lower correlation coefficient between this enzyme activity and subgingival B. intermedius (r = 0.26). Statistically significant (p < 0.01) positive correlations were also demonstrated between total bacterial cell counts and levels of enzymatic activity against N-benzoyl-D,L-arginine-B-naphthylamide hydrochloride (r = 0.76), N-carbobenzoxy-glycyl-glycyl-L-arginine-β-naphthylamide hydrochloride (r = 0. 72), and glycyl-L-proline-4-methoxy- β-naphthylamide hydrochloride (r = 0.69). There were significant differences in the levels of these three enzymatic activities between sites exhibiting various degrees of clinical severity of gingival inflammation and harboring various proportions of B. gingivalis.

The data from this study indicate that measurement of specific enzymatic activities in subgingival samples can be useful in the diagnosis of B. gingivalis-associated periodontitis.
The Influence of Tonic Muscle Activation on Human Jaw Displacement Tremor
Authors: McCarroll R.S. , De Vries J.H.
Published: November 2010

Jaw displacement tremor was investigated. Both tremor amplitude and tremor frequency were found to increase with increasing muscle activation. Co-contraction of jaw elevator and jaw depressor muscles was employed in order to vary muscle activation levels without the teeth being in occlusion. Reproducibility of tremor changes was statistically significant for each individual investigated. The relationship between tremor frequency and tremor amplitude, over the range of muscle activation investigated, varied per individual. It is hypothesized that the physiological basis for this inter-individual variation is differences in the development of jaw stiffness with increasing muscle activation between subjects. This explanation may be the basis, at least in part, for the clinical presence of objective jaw stiffness in one subject and its absence in another.
Delayed Crack Development in Porcelain Due to Incompatibility Stress
Authors: Anusavice K.J. , Dehoff P.H. , Gray A. , Lee R.B.
Published: November 2010

Delayed failure of metal-ceramic restorations due to static fatigue can occur when residual tensile stress is present in porcelain, even in the absence of intra-oral forces. Fixed-partial-denture (FPD) specimens and semicircular arch specimens with gapped cross-arch segments were employed to characterize the potential of two incompatible metal-ceramic systems for producing delayed crack development and to determine the relative sensitivity of these test designs as monitors of incompatibility stresses which resulted from thermal contraction differences between a nickel-chromium alloy and three experimental porcelains.

The arch specimens were judged to be more suitable for analysis of residual stresses because of the larger magnitude of gap changes at each procedural change. However, the FPD specimens exhibited earlier evidence of delayed crack growth in porcelain when the thermal contraction coefficient of the metal exceeded that of the porcelain by either 1.7 × 10-6/°C or 2.2 × 10-6/°C. For these two states of incompatibility, the agreement between experimental gap values for the arch specimens and the gap values predicted from composite strip equations was excellent.
Parameters that Affect in vitro Bonding of Glass-ionomer Liners to Dentin
Authors: Barakat M.M. , Powers J.M. , Yamaguchi R.
Published: November 2010

The purpose of this study was to evaluate the effects of two concentrations of poly (acrylic acid) (10 and 25%), three treatments (untreated, passive conditioning, and active conditioning), and two storage conditions (24 hours in 37°C water and thermal cycling) on the in vitro tensile bond strength of three commercial glass-ionomer liners to human dentin. Bond strengths to untreated dentin after storage for 24 hours ranged from 19.0 to 21.7 kg/cm2 for Glasionomer Base Cement, Cement/Liner, and Ketac-Bond, but dropped to a range of 4.9 to 9.7 kg/cm2 after thermal cycling. Active conditioning with 10% acid resulted in bond strengths after 24-hour storage that ranged from 23.5 to 44.0 kg/cm2, compared with values from 21.7 to 38. 0 kg/cm2 with active conditioning using 25% acid. Active conditioning with 10% acid resulted in bond strengths after thermal cycling that were in the range of 15.8 to 27.4 kg/cm2 and were 80 to 320 percent higher than values resulting from passive conditioning under these conditions. Active conditioning with 10% acid for 30 seconds produced a bond strength for Glasionomer Base Cement of 44.0 kg/cm2, compared with a bond strength of 28.7 kg/cm2 for a 10-second active conditioning. Qualitative analysis of scanning electron photomicrographs showed that dentin tubules were opened to a greater extent by active conditioning with 25% acid than by passive conditioning with 10% acid.