bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Dietary and Dentifrice Effects Upon Calculus Accumulation Rates in the Domestic Ferret
Authors: Harper D.S. , Mann P.H. , Regnier S.
Published: November 2010

Most animal models for the study of calculus accumulation and control currently use rodents or dogs. In an effort to overcome limitations inherent in the use of these species, we investigated calculus formation in domestic ferrets, a species used by King et al. in the 1940's and 1950's. Ferrets are much smaller than dogs, and, unlike rodents, can be scored while alive. In this study, we examined the kinetics of calculus formation in female ferrets fed with moist canned cat food-either plain or supplemented with sucrose-and two combinations of mineral salts. An additional group given supplemented cat food was treated twice daily with regular Crest toothpaste. Animals were sedated with a 1:1 mixture of ketamine and xylazine solutions and given a mechanical prophylaxis prior to the trial period, then scored for area and extent of calculus accumulation at two, four, six, and eight weeks thereafter. The data showed that the mineral-supplemented groups accumulated calculus at a significantly faster rate than the unsupplemented or dentifrice-treated groups, but the differences were no longer significant at eight weeks. This demonstrated that the ferret is a suitable model for the study of calculus, that dietary mineral content influenced calculogenesis, and that the application of regular dentifrice initially slowed, but did not prevent, calculus accumulation.
Reduction of Calculus Accumulation in Domestic Ferrets With Two Dentifrices Containing Pyrophosphate
Authors: Mann P.H. , Harper D.S. , Regnier S.
Published: November 2010

Work performed by King et aL in the 1940's and 1950's, as well as recent studies by our group, have shown that the domestic ferret is a suitable model for the study of calculus formation, offering several advantages over the rodent and dog models in current use. We have demonstrated that mineral supplementation of a moist diet accelerates calculus accumulation, and that twice-daily application of a regular dentifrice slows the initial rate of calculus formation, but permits significant accumulation by the eighth week. The present study compared calculus accumulation in female ferrets receiving mineral-supplemented cat food and a twice-daily application of either Regular Crest toothpaste (Crest), Anti-tartar Crest (Crest-AT), or Anti-tartar Colgate Gold toothpaste (Colg-AT). Animals received an ultrasonic prophylaxis, then were fed once daily for eight weeks with moist canned cat food supplemented with sucrose and mineral salts, and were scored for area and extent of calculus accumulation at four and eight weeks after prophylaxis. The data show that the groups treated with the anticalculus dentifrices produced significantly less calculus than the group treated with regular dentifrice; the Colg-AT group also exhibited lower scores than did the Crest-AT group, especially at four weeks. These results, similar to those seen in human studies, demonstrate that the ferret is a suitable model for the study of anti-calculus dentifrices.
A Comparison of the Influence of Lanthanum and Fluoride on De- and Remineralization of Bovine Enamel in vitro
Authors: Collys K. , Slop D. , De Langhe L. , Coomans D.
Published: November 2010

The influence of fluoride and lanthanum on enamel softening was compared by hardness measurements and by determination of the calcium content in the solution. The addition of lanthanum to an acetate buffer solution (0.05 mollL, pH=5.0) had no significant influence on the change of the indentation length and on the calcium release, compared with those of the control group. In the fluoride group, a moderate increase of the indentation length and a reduced calcium loss were observed. In a second experiment, surface-softened bovine enamel was treated with calcifying solutions (Ca/P ratio = 1. 67). Differences in treatment were created by the addition of traces (2 ppm) of lanthanum, fluoride, or both. The acid resistance of the treated enamel was evaluated by two successive softening steps (0.1 mol/L acetate buffer, pH = 5.5). Alterations of the enamel surface were longitudinally followed with a hardness tester. The addition of fluoride, lanthanum, or both significantly improved the rehardening of surface-softened enamel, compared with that of the control group. A 2 x 2 factorial analysis of variance showed that lanthanum and fluoride had a highly significant main effect and a significant negative interaction effect on the rehardening of surface-softened enamel. Subsequent acid treatments revealed that only samples treated with a fluoride-containing solution were adequately protected from further dissolution. The enamel surfaces treated with a solution containing both lanthanum and fluoride were covered with an acid-resistant surface coating. SEM observation of this surface layer revealed the presence of globular and spherulite structures.
Characteristics of Mandibular Masticatory Movement in Young and Elderly Dentate Subjects
Authors: Karlsson S. , Carlsson G.E.
Published: November 2010

Dimensions and velocity of mandibular movement are important variables in the evaluation of masticatory and speech patterns. However, little information is available concerning elderly dentates and their oral motor function and behavior. Double recordings of a chewing period, from start to swallowing, were performed in 14 elderly (mean age, 80 years) and 30 young (mean age, 26 years) dentate subjects chewing crispbread. Three-dimensional records of mandibular movements were obtained by means of the Selspot movement analysis system, which monitors infrared light pulses from light-emitting diodes attached to the test subject. There was no difference in the duration of the total chewing cycle between the two groups. Mandibular velocity was significantly lower in the elderly group, in both the opening and the closing phases. Despite great inter-individual variations, significantly smaller mean vertical displacements of the mandible were found in the elderly than in the younger group. The lateral component in the vertical opening movement was similar for both the elderly and younger subjects. The similar chewing rates in the two groups might imply that the function of the central pattern generator was unaffected by old age. Aging was, however, associated with reduction of vertical mandibular displacement and velocity.
Observations on the Elastic Behavior of a Synthetic Orthodontic Elastomer
Authors: Huget E.F. , Patrick K.S. , Nunez L.J.
Published: November 2010

The study focused on changes in elasticity that accompany water storage of a synthetic orthodontic elastomer. We plotted loading and unloading curves to permit the direct measurement of instantaneous elastic recovery (IER) and permanent set (PS) and the calculation of delayed recovery (DR). We obtained baseline data by testing dry as-received material. Comparable tests were performed on material that had been stored in water at 37°C for one, seven, 14, 42, and 70 days. Gas chromatography-mass spectrometry was used for analysis of organic substances leached from the elastomer by water. A two-way ANOVA revealed that extension distance and water storage duration affected load requirement, IER, PS, and DR. The presence of leachable organic substances in 14-, 42-, and 70-day storage water was evidence of time-dependent matrix decomposition. Findings from tests of elastic performance and analysis of specimen storage water indicate that exposure of the elastomer to water leads first to weakening of noncovalent forces and subsequently to degradation.
The Prevalence and Pattern of Distribution of Root Caries in a Scottish Medieval Population
Authors: Kerr N.W.
Published: November 2010

The prevalence and pattern of distribution of root caries were determined in a Scottish Medieval population. The principal finding was a lower root caries prevalence, compared with that of modern times, with respect to surfaces at risk; this was particularly marked with respect to buccal root caries. A lower intake of refined sugars and the presence of heavy deposits of supragingival calculus are suggested as factors that may be responsible for the observed differences.

The common site for the early root caries lesion was just apical to the enamel-cementum junction. Initially, it extended laterally in the form of an elliptical erosion; however, the greater the depth of the lesion, the more circular the outline became.
Depressed Eruption Rate of the Rat Maxillary Incisor in a Drug-induced Uncompensated Hemolytic State Model
Authors: Giglio M.J. , Sanz A.M. , Bozzini C.E.
Published: November 2010

Female rats weighing about 180 g were separated into two groups. One group (A) received phenylhydrazine (PHZ) every other day during three weeks (for induction of an uncompensated hemolytic state), while the control group (C) received saline.

The evidence for the establishment of the uncompensated hemolytic state was obtained by hematocrit value, reticulocyte count, and red-cell-volume-59Fe uptake. Body-weight gain (which is a measure of overall body growth rate), body-length gain (which is a measure of longitudinal skeletal growth rate), food intake, and maxillary incisor eruption rate (ER) were significantly depressed in rats of group A during the PHZ-injection period, in relation to rats of group C. These results indicate that anemia and/or associated factors depress ER, along with body growth and skeletal growth.
The Release of Mercury from Dental Amalgam: The Mechanism and in vitro Testing
Authors: Marek M.
Published: November 2010

Dissolution of mercury from the Ag-Hg matrix phase of dental amalgam in distilled water and synthetic saliva, and the mercury evaporation from the solutions, were studied in vitro. The main objectives of the study were to evaluate the factors that affect the results of the mercury release tests, and to consider the possible mechanisms of the release in vivo. Specimens were exposed to the liquids in open or closed bottles, and the changes in the mercury concentration were determined by cold-vapor Atomic Absorption Spectrophotometry.

Concentration vs. time tests showed the dissolution rate decreasing with time. Tests involving sequences of short and long exposures with solution changes showed higher average rates for short-term dissolution into the fresh solution than for the longer preceding exposures. The differences were attributed to a stifling effect of the concentration of elemental mercury on the dissolution. It is believed that mercury dissolved mainly in the elemental form and that a continuous increase in the concentration was made possible by oxidation in the solution. In open cells, some of the mercury was lost by evaporation. The analysis showed that the results of mercury dissolution tests depend on many test variables, such as time, solution volume, oxidation and evaporation conditions, etc.

Evaporation, dissolution, and evaporation/dissolution mechanisms of the mercury release in vivo were considered. It was concluded that the dissolution/evaporation model best described the mercury release from dental amalgam restorations.
Optical Quantification of Caries-like Lesions in vitro by Use of a Fluorescent Dye
Authors: Van de Rijke J.W. , Ten Bosch J.J.
Published: November 2010

An experimental method was developed for measurement of the fluorescence intensity of a dye that was introduced into caries-like lesions in vitro. A distinct pattern of change of fluorescence intensity with time appeared, displaying a plateau value and a peak value for each measurement. Both plateau and peak values showed a linear correlation with calcium loss, as measured with longitudinal microradiography. The correlation coefficients were r = 0.87 for plateau values and r = 0.89 for peak values. The difference in scattering by dry and wet caries lesions was also measured with the same equipment, which showed a linear correlation with calcium loss of r = -0.53.
Histopathology of Root Surface Caries
Authors: Schüpbach P. , Guggenheim B. , Lutz F.
Published: November 2010

The histopathology of active and arrested human root caries was examined in extracted teeth by different optical methods. Significant differences were observed between the mechanisms operating on the various dental structures. Three different patterns of initial cementum and dentin lesions could be distinguished, depending on the severity of the cariogenic attack, the degree of sclerosis of the peripheral dentin, and the presence of calculus. Advanced lesions were characterized by various patterns of demineralization. In particular, a massive lateral spread of bacteria into intertubular dentin was observed. Consequently, unaffected dentinal areas became continuously undermined. In arrested lesions, either a partial or complete mineralization of the intertubular dentin was apparent. Dentinal tubules were sclerosed passively by re- or precipitation of Ca and P04 ions. In contrast, tubules filled with ghosts of bacteria appeared mineralized by fine-granular crystals. Our observations indicate that both the arrestment and the remineralization of active lesions depend on (1) the degree of active sclerosis of dentinal tubules in areas underlying the lesion, (2) the degree of the bacterial infection of the dentin, (3) the degree of progression of the lesions, and (4) the location of the lesions at the various root surfaces. It is suggested that remineralization of active lesions can occur. This supports the concept of non-invasive treatment of root caries lesions without cavitation.
Clinical Signs of Root Caries: Measurement Issues from an Epidemiologic Perspective
Authors: Katz R.V.
Published: November 2010

The measurement of root caries using a relatively precise, utilitarian, and universally-acceptable methodology based upon clinical signs is a critical and necessary step in the progression of the epidemiologic study of this oral disease. While a clinician directly involved in the care of a patient will always incorporate spontaneous judgment-based-upon-experience into the diagnostic process, the clinical investigator must rely upon a much more standardized approach to the diagnosis of root caries. A comprehensive overview of the current epidemiologic research findings and methodologic literature for root caries precedes a series of discussions on methodologic issues that relate to the measurement of root caries in epidemiologic study conditions. Topics discussed include: (1) appropriate categories of lesions for inclusion (active vs. inactive and supragingival vs. subgingival lesions), (2) surface visibility issues (clinical treatment effects and oral debris accumulations), and (3) examination techniques (examination instruments and use of radiographs). The final section of this article proposes seven diagnostic conventions for use by investigators when they are diagnosing root caries in descriptive, analytical, and experimental epidemiologic studies.
Indices of Root Surface Caries
Authors: Aherne C.A. , O'Mullane D. , Barrett B.E.
Published: November 2010

Despite the increasing international interest in recent years in the epidemiology of root surface caries, there is no agreement on the diagnostic criteria to be used when the condition is recorded. In this paper the different methods used by dental epidemiologists are reviewed. It is shown that the wide variation in the levels of root surface caries recorded among different populations could be due to differences in the diagnostic methods as well as to inherent differences in the prevalence of the condition. It is recommended that an attempt be made to reach a global consensus on the methods of diagnosing root surface caries. Also, it is suggested that in reports of epidemiological studies of root surface caries, a basic set of tables including details of tooth loss be included.
Oxide Adherence and Porcelain Bonding to Titanium and Ti-6A1-4V Alloy
Authors: Adachi M. , Mackert J.R. , Parry E.E. , Fairhurst C.W.
Published: November 2010

The bonding of an experimental low-fusing porcelain to titanium and Ti-6AI-4V was evaluated by an x-ray spectrometric technique that measures the area that remains covered with porcelain following a controlled deformation of the metallic substrate. Oxide adherence strength values for titanium and Ti- 6AI-4V oxidized at 750° and 1000°C were measured in tension with use of high-strength adhesives. The effect of further oxidation that would occur during porcelain firing was evaluated via simulated porcelain firings without actual porcelain application. Interface cross-sections of the titanium-porcelain and Ti-6AI-4V-porcelain bonds were examined in a scanning electron microscope (SEM). The porcelain was found to delaminate completely from the metal substrate, leaving less than 1% of the surface covered with porcelain. The oxide adherence of the specimens oxidized at 750°C was good, but those oxidized at 1000°C exhibited significantly lower oxide adherence (p = 0.001). The simulated porcelain-firing oxidation treatments also produced a significant decrease in oxide adherence (p = 0.004). The 750°C oxidation treatments produced oxide films too thin to be visualized in the SEM, whereas the 1000°C oxidation treatments produced oxide films approximately 1 µm thick. The lower oxide adherence of the 1-~,m-thick oxide films is consistent with reports in the titanium literature of oxide delamination when the oxide film reaches 1 µm in thickness.
Amine-induced Polymerization of Aqueous HEMA/Aldehyde During Action as a Dentin Bonding Agent
Authors: Munksgaard E.C.
Published: November 2010

Aqueous mixtures of HEMA with glutaraldehyde or propionaldehyde polymerize by addition of catalytic amounts of amines or amino acids. The maximal reaction velocity of the transformation of HEMA/glutaraldehyde with glycine was obtained at pH 0.8. Kinetic data suggested a second-order reaction between glutaraldehyde and glycine, and solubility data suggested formation of a cross-linked polymer. A relatively high bond strength between dentin and resin composite was obtained by pre-treatment of dentin with Gluma (35% HEMA, 5% glutaraldehyde in water) adjusted to pH 1.0 with hydrochloric acid. It is proposed that on application of Gluma, amino-group-containing substances in dentin react with glutaraldehyde and start the formation of a HEMA polymer. This product may be cross-linked by an α,β-unsaturated glutaraldehyde aldol condensation product and may bond to dentin by aldehyde fixation to dentin proteins. Resin composite will bond to this product by copolymerization.
Complete Marginal Seal of Class V Resin Composite Restorations Effected by Increased Flexibility
Authors: Kemp-Scholte C.M. , Davidson C.L.
Published: November 2010

The use of adhesive resin composites for restoration of Class V lesions often results in cervical marginal gap formation due to polymerization contraction. In this laboratory study, flexible linings applied between the bonding agent and the bulk restorative appeared to preserve the marginal integrity of Class V restorations during curing. Measurements of the polymerization contraction stress showed 20 to 50% relief due to various flexible intermediate materials. Apparently, reduction of the total stiffness by application of an intermediate layer can render the total restoration sufficiently flexible to compensate for that part of the stress that would otherwise exceed the bond strength.
Biochemical Mechanisms of Enhanced Inhibition of Fluoride on the Anaerobic Sugar Metabolism by Streptococcus sanguis
Authors: Hata S. , Iwami Y. , Kamiyama K. , Yamada T.
Published: November 2010

The effect of fluoride on acid production by Streptococcus sanguis ATCC 10556 was compared under anaerobic and aerobic conditions. The rate of acid production under constant-pH and pH-free-fall conditions was determined during glucose metabolism by resting cells. Anaerobic glycolysis was inhibited more strongly by fluoride than was aerobic glycolysis. Intracellular levels of 3-phosphoglyceric, 2-phosphoglyceric, and phosphoenolpyruvic acids were lower under anaerobic conditions than under aerobic conditions. Thus, S. sanguis had a low phosphoenolpyruvate (PEP) potential under anaerobic conditions. This low PEP potential was suggested to account for the more effective fluoride inhibition of enolase and, consequently, the reduced transport of sugar by the PEP-dependent phosphotransferase system of this micro-organism.
Effect of pH on the Growth and Proteolytic Activity of Porphyromonas gingivalis and Bacteroides intermedius
Authors: Takahashi N. , Schachtele C.F.
Published: November 2010

The effect of pH on the growth and proteolytic activity of the type strain and fresh isolates of Porphyromonas gingivalis and Bacteroides intermedius was investigated. B. intermedius strains grew with and without glucose at a pH as low as 5.0. These bacteria grew almost as well as Streptococcus mutans at pH 5.0 and better than Actinomyces viscosus at pH 5.5 and 5.0. Some B. intermedius strains raised the culture pH when grown at a low pH without glucose. In contrast, P. gingivalis strains grew only at pH 6.5 to 7.0. The P. gingivalis strains had proteolytic activities against azocoll, azocasein, and azoalbumin, while the B. intermedius strains degraded azocasein and azoalbumin, but not azocoll. B. intermedius showed maximum proteolytic activity at pH 7.0, and high activity over a wide pH range. In contrast, the optimum pH of proteolytic activity in P. gingivalis was pH 7.5 to 8.0. The P. gingivalis activities were more sensitive than those of B. intermedius to low pH. The capacity of B. intermedius to degrade proteins to more readily metabolizable substrates at low pH might explain the growth of this bacterium in an acidic environment. These differences between B. intermedius and P. gingivalis could explain their capacity to survive at different sites in the oral cavity and indicate how B. intermedius might positively influence the growth of P. gingivalis in subgingival plaque.
The Caries Status of Occlusal Amalgam Restorations with Marginal Defects
Authors: Kidd E.A.M. , O'Hara J.W.
Published: November 2010

The purpose of this study was to examine histologically occlusal amalgam restorations with both defective and sound margins for comparison of their caries status. Thirty extracted teeth with occlusal amalgam restorations were sectioned so that a ditched and a clinically sound margin could be examined on the same tooth in the mouth. Histological examination showed a low prevalence of caries lesions in the outer enamel. However, lesions were present in the enamel of the cavity wall in 54% of specimens, whether the margin was defective or sound. If the results of this study are applicable to all occlusal amalgams with defective margins, it would appear that a defective margin alone is not an indication that a restoration needs to be replaced.
The Inorganic Components of Cementum- and Enamel-related Dentin in the Rat Incisor
Authors: Steinfort J. , Deblauwe B.M. , Beertsen W.
Published: November 2010

Recently, we have shown that, in rodent incisors, the crown- and root-analogue dentin (enamel- and cementum-related dentin) show differences in mineralization rates (Beertsen and Niehof, 1986) and composition of the organic matrices (Steinfort et al. , 1989). It was the aim of the present study to determine whether these differences were accompanied by differences in the inorganic components.

Rat incisors were analyzed by means of hardness measurements, microradiography, and the determination of Ca, Mg, and PO4 content. The outer circumpulpal dentin layer of the enamel-related dentin (ERD) was considerably harder and denser than the comparable layer of the cementum-related dentin (CRD). Concomitantly, a higher Ca and P04 content was found for the ERD than for the CRD, while the reverse occurred with respect to Mg. From the apical end of the incisor toward the incisal edge, the Ca/PO4 ratio tended to decrease for both ERD and CRD, while the Mg/PO4 ratio increased. All differences appeared to be statistically significant.

It is concluded that differences in the non-collagenous organic matrix were accompanied by differences in the inorganic components. More specifically, a relatively high content of highly phosphorylated phosphoproteins (ERD) was associated with a higher Ca and a lower Mg content.
Plaque Fluid and Diffusion: Study of the Cariogenic Challenge by Computer Modeling
Authors: Dibdin G.H.
Published: November 2010

Every cariogenic challenge involves a mixture of convective transport, diffusive transport, and biochemical reactions, plus physico-chemical reactions (including charge-coupling of diffusion), all of which together require numerical methods for their analysis. This presentation describes a one-dimensional finite-difference computer model of the cariogenic process, and some conclusions obtained from it.

Sugar clearance from the mouth, together with site-dependent exchange between the bulk saliva and plaque surface via a salivary film, is combined with a finite-difference model of events occurring within the dental plaque. The latter includes: sugar diffusion and pH-dependent acid production; diffusion and dissociation equilibria for two acid end-products of fermentation and their anions (acetate and lactate); diffusion and dissociation equilibria of phosphate buffer; diffusion of potassium and chloride; diffusion of protons and simultaneous equilibration with fixed and mobile buffers. So that proper concentration distributions consistent with local charge neutrality can be ensured, an algorithm called Q-couple is used to impose charge-coupling between the fluxes of different ions including fixed charges. Mineral dissolution and precipitation are modeled as part of the same equilibrium calculations.

The predictions of the model are compared with those of an earlier, much simpler one, in which fixed buffers were not included. It is shown that the known concentration of fixed buffer greatly extends the low pH of a Stephan curve. The isoelectric point of the plaque bacteria also appears to be of importance. The effects of various concentrations of mobile buffers, including acetate, are investigated. It is also shown that varying plaque/saliva contact over the known range derived from published studies has a profound effect on the modeled cariogenic challenge.
Plaque Fluid as a Bacterial Milieu
Authors: Edgar W.M. , Higham S.M.
Published: November 2010

Studies of the extracellular, free concentrations of substrates, growth factors, inhibitors, and end-products of metabolism to which the intact plaque microflora is exposed in situ can assist in the understanding of factors controlling plaque pathogenicity. Information is becoming increasingly available from analysis of fluid separated by centrifugation of plaques collected at various intervals after an intra-oral pulse of dietary or experimental substrate, or different procedures or treatments having cariostatic potential. Such analytical results give more information than those obtained by analysis of aqueous or other extracts, because they yield values of substrate concentration representing those occurring at the bacterial cell surface.

The largest body of information concerns extracellular levels of acid end-products of sugar catabolism in relation to food quality or sequence, and of amino acids and other products of nitrogen metabolism, in relation to studies of the detailed metabolic events of the Stephan curve, and of the demineralizing effect of the plaque environment. Areas where little information is available and which merit further study include plaque clearance of salivary and other components with anti-caries activity (e.g., antibodies, enzymes, fluorides, cations, other antimicrobials, etc.), and substrate concentrations to determine gradients for diffusion into and out of plaque.
An Assessment of Recent Advances in the Study of the Chemistry and Biochemistry of Dental Plaque Fluid
Authors: Margolis H.C.
Published: November 2010

This paper discusses key points made during the symposium in the light of work carried out in other laboratories. It is emphasized that the unique importance of plaque fluid is that the net result of chemical changes induced by microbial activity is reflected in this medium, which is in intimate contact with the enamel surface, and that this medium is accessible to chemical and biochemical analyses. However, in order to assess the cariogenic potential of plaque, we must consider the properties of both whole plaque and plaque fluid together. Although it is apparent that results of plaque fluid composition are sensitive to both isolation and the storage procedures utilized, plaque fluid appears to be a distinct entity within the oral cavity. Technical advances have been made which allow for the determination of the activity of selected ions (hydrogen, calcium, phosphate, potassium, fluoride) in plaque fluid obtained from a single site within the mouth. It appears, however, that such data alone may be insufficient to define the cariogenic potential of plaque appropriately. Evidence is presented from which it can be concluded that, with use of pooled samples of plaque obtained from individuals with clear differences in caries experience, results on plaque and plaque fluid composition can be obtained which are consistent with noted differences in caries susceptibility. The importance of base production is also discussed, and it is noted that few studies have been carried out to elucidate the role of proteins found in plaque fluid. In conclusion, recent advances in the study of plaque fluid have provided new insights into the mechanism of caries formation which are also germane to the formation of dental calculi.
Mutans Streptococci, Oral Hygiene, and Caries in an Adult Swedish Population
Authors: Salonen L. , Allander L. , Bratthall D. , Hellden L.
Published: November 2010

The objective of the present study was to describe the distribution of salivary mutans streptococci in a randomly selected adult population and to relate the distribution to the prevalence of caries. The aim was also to study the association between caries and different levels of oral hygiene (OH). The results were based on the assessment of caries, dental plaque, and concentration of salivary mutans streptococci in 914 subjects who represented 95% of an age- and gender-stratified population sample of 967 individuals, randomly selected from the total adult population living in Alvsborg County, Sweden. The results showed that the distribution of mutans streptococci among dentate adults not wearing any kind of removable denture(s) was similar to that previously reported from studies on Swedish schoolchildren, while a comparably higher proportion of subjects with high levels of mutans streptococci was found among the dentate individuals wearing some kind of removable denture(s). Even higher proportions were found among edentulous individuals with complete denture(s). There was a correlation between mutans streptococci concentration in saliva and caries. The subjects with lower concentrations showed a significantly lower mean number of decayed surfaces, compared with the individuals with higher concentrations of mutans streptococci in their saliva.

The median OH standard was lower in the older age groups, and there was a higher ratio of decayed surfaces per remaining tooth in those age groups, in comparison with the younger groups. However, for individuals without mutans streptococci, no relation between OH standard and caries could be found and, regardless of OH standard, higher numbers of decayed surfaces were found with an increasing concentration of mutans streptococci in saliva.
Relationship of TMJ Articular Soft Tissue to Underlying Bone in Young Adult Condyles
Authors: Pullinger A.G. , Baldioceda F. , Bibb C.A.
Published: November 2010

This investigation used a histological model to study the relationship of articular soft-tissue thickness and contour to the underlying bone in the TMJ condyle of young adults. The usefulness of selected dental and demographic factors in the prediction of the articular soft-tissue thickness and contour was also tested. One sagittal histological section was studied from the lateral, central, and medial thirds of 53 left mandibular condyles. Outline tracings of the articular and compact bone surface were divided into anterior, superior, and posterior sectors for the study of curvature measured by the overlaying of a template of a harmonic series of arcs. The thickness and composition of the articular tissues were measured in each sector by light microscopy. The fibrous connective tissue layer always maintained the articular surface, even in the absence of a cartilage layer. The histological character, including the presence or absence of cartilage, rather than the overall tissue thickness, was considered to be a more useful marker of functionally stimulated changes in the joint. Articular soft-tissue thickness was not related to surface deviation in form and was not correlated with age in this young adult sample. Reduced soft-tissue thickness in the anterior part of the condyle was more common in cases with lack of molar support. Dental attrition was not a useful predictor of soft-tissue thickness. Compact bone contour correlated with soft-tissue contour in the superior (r = 0.816) and posterior (r = 0.808) sectors, explaining only 64% of the variance, but not in the anterior sector (r = 0.265). Thicker or thinner articular soft tissue was not predictable by the underlying compact bone contour or thickness. Therefore, the clinician should not automatically assume that the radiographic osseous image represents the actual articular surface.
Stimulation of Proteoglycan and DNA Syntheses in Chondrocytes by Centrifugation
Authors: Inoue H. , Hiasa K. , Samma Y. , Nakamura O. , Sakuda M. , Iwamoto M. , Suzuki F. , Kato Y.
Published: November 2010

So that the effects of biomechanical forces on the proliferation of chondrocytes and their proteoglycan synthesis could be studied, growth-plate and articular chondrocytes were maintained separately as packed masses in centrifuge tubes in the presence of 10% serum. In these conditions, the cells became re-organized into cartilaginous tissue in seven days. After ten days, they were centrifuged at gravities (g) of 1.3-27 for 24 h in a CO2 incubator. Control cells were maintained in the CO2 incubator without centrifugation. Centrifugation of growth-plate chondrocytes at 3 g resulted in a two-fold increase in incorporation of [35S]sulfate into proteoglycans, but had little effect on their [3H]thymidine incorporation into DNA. On the other hand, centrifugation of articular chondrocytes at 3 g for 24 h caused 1.5-fold increases in both [35S]sulfate incorporation into proteoglycans and [3H]thymidine incorporation into DNA. These results suggest that biomechanical forces have different effects on the growth and differentiation of articular and growth-plate chondrocytes.
The Effect of Nutritional Status on the Age Distribution of Dental Caries in the Primary Teeth
Authors: Alvarez J.O. , Eguren J.C. , Caceda J. , Navia J.M.
Published: November 2010

A cross-sectional study of dental caries in the primary teeth as a function of nutritional status was conducted on 1481 children one to 13 years old in Lima, Peru. Forty-one percent of the children were found to be chronically malnourished (stunted), 3% were acutely malnourished (wasted), and 5% were both stunted and wasted. A plot of decayed, extracted, and filled teeth (deft) vs. age resulted in a bell-shaped curve that was shifted to the right by 2.5 years for malnourished groups, compared with normal children (p<0.01). The shift to the right of the age distribution of caries was associated with a delay in both the eruption and exfoliation of the primary teeth in malnourished children. Peak caries activity was significantly higher in wasted and in stunted and wasted children, when compared with normal controls. It is concluded that malnutrition delayed tooth development, affected the age distribution of dental caries, and resulted in increased caries experience in the primary teeth.
Onset of Elasticity in Setting Elastomers
Authors: McCabe J.F. , Carrick T.E.
Published: November 2010

A controlled stress-rheometer used in creep/recovery mode was used for detection of the onset of elasticity in setting elastomers. The time for the materials to develop 5-20% elastic recovery corresponded with the time to reach a phase angle of 60° in an oscillatory test.
In vitro Evaluation of a Fluoride-releasing Orthodontic Resin
Authors: Chan D.C.N. , Swift E.J. , Bishara S.E.
Published: November 2010

Decalcification around brackets is sometimes observed following orthodontic treatment. Fluoride-releasing orthodontic adhesives have been developed and used for reduction of the frequency and severity of decalcification. This study evaluated a light-activated, fluoride-releasing resin composite adhesive, FluorEver OBA.

Our findings indicate that FluorEver OBA released small concentrations of fluoride ions over time. However, the adhesive had significantly lower tensile bond strengths than a conventional composite cement. Microhardness testing indicated that the resin underneath metal orthodontic brackets was not thoroughly polymerized, which may have contributed to cohesive failures of the resin composite.

Despite its lower tensile bond strength, FluorEver OBA may be indicated for cases where decalcification is expected.
Limit of Resolution of Flow Cytometry for the Detection of Selected Bacterial Species
Authors: Obernesser M.S. , Socransky S.S. , Stashenko P.
Published: November 2010

The enumeration of bacteria in dental plaque samples is a vital but time-consuming procedure that uses standard cultural methods. Flow cytometry has proven to be a useful tool for the analysis of eukaryotic cells. In the present investigation, the utility of this technology for the enumeration of bacteria in mixtures was explored. Rabbit antisera were produced against the putative periodontal pathogens A. actinomycetemcomitans, B. intermedius, B. gingivalis, E. corrodens, W. recta, B. forsythus, as well as the frequently isolated supragingival species S. sanguis. Cross-reactive antibodies were removed by absorption, and the specificity of each antiserum was confirmed by being tested against a panel of 235 oral microbial strains (79 genera; 94 species) by means of ELISA. Conditions were established for the indirect immunofluorescent labeling of cells without agglutination with use of a goat anti-rabbit Ig-FITC second antibody. When an internal bead standard was used, it was found that unstained bacteria were enumerated by light-scattering parameters with poor efficiency (<3%). However, cells exposed to FITC either in the presence of specific or nonspecific first antibody were enumerated with high efficiency (102.6±29.3%), indicating that a small amount of non-specific binding of fluorochrome facilitates bacterial detection. Clear discrimination between specifically- and non-specifically-stained bacteria was achieved with all six rabbit antisera. Mixtures of known composition were made (1) with pure cultures or (2) with a known species and supragingival plaque devoid of that species by culture. The results from both approaches with various species combinations revealed that the limit of resolution for accurate quantitation of a selected species was approximately 5%, although specific organisms could be detected qualitatively when present at approximately 1%.
Effect of Placement of Amalgam Restorations on Urinary Mercury Concentration
Authors: Landro Olstad M. , Holland R.I. , Hensten Pettersen A.
Published: November 2010

Dental amalgam emits mercury, especially during setting. In addition, the preparation of the amalgam and its compaction into the cavity involve unbound metallic mercury or create a waste product with free metallic mercury. The present study was performed to explore whether emission of mercury in these situations would measurably influence the individual urinary mercury concentration of dental patients as a result of a single-session treatment with dental amalgam restorations. Informed consent was obtained from the parents of nine children about to be treated with amalgam restorations as part of their regular dental care. The children delivered a total of five morning urine samples before, during, and after the treatment period. No effect on the urine mercury concentration was found during the treatment period. Conclusively, one single session of amalgam treatment did not per se represent a mercury exposure of sufficient quantity to be detectable in a longitudinal, individual study.
Adhesive Bonding of Titanium with a Titanate Coupler and 4-META/MMA-TBB Opaque Resin
Authors: Matsumura H. , Yoshida K. , Tanaka T. , Atsuta M.
Published: November 2010

Adhesive bonding of titanium was evaluated with a titanate primer and adhesive opaque resin. The primer consisted of 2% isopropyl dimethacryloyl isostearoyl titanate in methyl methacrylate. The adhesive was 4-META/MMA-TBB opaque resin that contained 4-methacryloyloxyethyl trimellitate anhydride and was initiated by tri- n-butylborane derivative. Titanium discs were machined and blasted with aluminum oxide. They were primed and bonded together with the opaque resin. A shear test was performed after repeated thermocycles for investigation of the durability of the bond. The shear strength of the primed and 4-META resin-bonded specimens was 37.2 MPa after 50,000 thermocycles, with only a small decrease in bond strength. This was significantly higher than the control values. Thus, titanate primer and 4-META/MMA-TBB opaque resin may be used for the bonding of titanium in prosthodontic practice.
Statistical Models for Evaluating the Penetrating Ability of Endodontic Instruments
Authors: Fuchs C. , Friedlander C. , Rosenberg E. , Tamse A.
Published: November 2010

An in vitro study was conducted to evaluate the penetrating ability of hand instruments (No. 10 K-file and "Pathfinder") and an automated device with a No. 08 (Canal Finder System) file in 270 extracted curved and narrow molar roots. The roots were randomly allocated to six groups, each one corresponding to a different permutation of the three instruments. The experiment was performed in three sequential stages, and Stages II and III were undertaken only in roots where no apical penetration was achieved in the previous stage(s). Statistical models were designed to fit the resulting clinical data. The No. 08 Canal Finder System and No. 10 K-file proved to be similar in their penetrating ability in Stage I (with estimated probabilities of 71.1% and 68.8%, respectively). The No. 08 Canal Finder was found to be the most efficient in Stage II and especially in Stage III, with a probability of penetration of 20.7%, compared with 9.8% for the "Pathfinder" and 7.4% for the No. 10 K-file.
Oral Induction of Immunological Tolerance to Chromium in the Guinea Pig
Authors: Vreeburg K.J.J. , Van Hoogstraten I.M.W. , Von Blomberg B.M.E. , De Groot K. , Scheper R.J.
Published: November 2010

Metal alloys used in dentistry may elicit adverse side-effects. Contact allergic reactions to metals released from such alloys are among the most frequently encountered problems. In an earlier study, we observed that oral contacts with nickel or chromium salts did not sensitize, but rather decreased the risk of subsequent sensitization to these metals. In the present study, we focused on chromium allergy and extended our earlier observations by further dose-response studies. In addition, we compared different chromium valencies as to their potential oral tolerogenic effects. Development of immunological tolerance in chromium-fed guinea pigs was demonstrated by their inability to develop chromium hypersensitivity after a subsequent immunization attempt. For these studies, the techniques of immunization and skin testing were first improved.

One feeding with a high dose of K2Cr2O7, (containing hexavalent chromium) was effective in full tolerance induction. In contrast, trivalent chromium (CrCl3) induced a distinctly lower degree of tolerance, whereas metallic chromium powder was not detectably tolerogenic after a limited number of feedings. Dose-frequency-response studies with K2Cr2O 7, showed that full tolerance could also be induced by an increase in the number of feedings with sub-optimal tolerogenic doses. The present results therefore support our hypothesis that long-lasting oral contact with chromium-releasing metal alloys may ultimately result in strong immune tolerance to this metal in subjects without previous skin contact with it. This view is further supported by recent insights into the unique tolerogenicity of oral, as compared with gastro-intestinal, allergenic contacts.
The Growth-inhibitory Effect of the Enterococcus faecalis Bacteriocin Encoded by pADl Extends to the Oral Streptococci
Authors: Jett B.D. , Gilmore M.S.
Published: November 2010

Many strains of Enterococcus faecalis, a normal inhabitant of the oral cavity, elaborate a plasmid-encoded bacteriocin. The growth-inhibitory effect of this bacteriocin was observed to extend to a variety of pathogenic oral streptococci, including those that play a major role in tooth surface colonization and caries formation. These results suggest that transient colonization by bacteriocin-producing E. faecalis may effect shifts in oral colonization by susceptible organisms and that bacteriocin-producing E. faecalis may be a candidate for application in strain replacement therapy.
The Effect of Sucrose Application and Implantation of Mutans Streptococci on the Microbial Composition of Three-week Experimental Plaque—An in situ Study
Authors: Macpherson L.M.D. , MacFarlane T.W. , Aitchison T.C. , Stephen K.W.
Published: November 2010

This study describes the predominant cultivable microflora of three-week-old plaque samples obtained from human enamel sites, on the basis of microbial identification of over 9000 fresh isolates. Lower removable appliances, on which were mounted enamel sections and slabs, were worn by five young adult subjects under three experimental protocols. These were (1) 'normal' plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each subject's own mutans streptococci onto the enamel test sites and sucrose applications, as described above. With the exception of slightly higher proportions of Gram-negative bacilli associated with slab plaque following sucrose application, no significant differences in percentage or absolute counts of organisms were found between normal and sucrose plaques. The inoculation of mutans streptococci, combined with extra-oral sucrose applications, was associated with significantly higher percentages and absolute mean counts of both mutans streptococci and lactobacilli, and lower proportions of S. sanguis and S. oralis. Although the isolation frequency of mutans streptococci increased in all subjects and the overall mean proportion rose following inoculation, considerable inter-subject variation was seen in mean percentage counts of these organisms isolated from the three-week plaque samples.