Showing papers in "Journal of Dental Research in 1984"

Black-pigmented Bacteroides species, Capnocytophaga species, and Actinobacillus actinomycetemcomitans in human periodontal disease: virulence factors in colonization, survival, and tissue destruction.

Abstract: There have been many advances in the past decade in our knowledge of the microflora associated with periodontal diseases, the potential of specific periodontal bacterial species to destroy periodontal tissues, and the host responses to bacterial infections of the periodontium. It is the purpose of this and an accompanying paper, to present important features of the host-parasite interaction in human periodontal disease. The present communication emphasizes characteristics of periodontopathic bacteria which may enable them initially to colonize the host, to survive in the periodontal pocket, and possibly to invade the gingival tissue despite potentially effective host defense systems, and to destroy the collagenous periodontal ligament, the alveolar bone, and other tissue components surrounding the tooth. It seems reasonable to assume that a bacterial species must possess factors applicable to most if not all of the above aspects of the infectious process of periodontal disease in order to produce periodontitis.

The Competition between the Composite-Dentin Bond Strength and the Polymerization Contraction Stress

Abstract: The influence of contraction stresses, developed during the polymerization of composites, on adhesion to dentin treated with a dentin adhesive was studied for a chemically- and a light-activated microfilled composite. In both linear and 3-D models. The linear model consisted of an arrangement set up in a tensilometer in which the composites could be applied to a flat dentin surface fixed to the stationary cross-head at one end, and mechanically clamped to the cross-head connected to the load cell at the other end. The increase of the bond strength was measured at different time intervals from the start of mixing and was compared with the developing contraction stress. Throughout the complete polymerization process, the adhesion survived the contraction stress, which is explained by flow relaxation, which can occur sufficiently in this configuration. In the three-dimensional model, the composites are attached to more than two dentin walls. In this situation, flow is severely limited, and contraction stress values can exceed the bond strength, leading to separation. This was demonstrated in Class V cavities. The shape of the cavity is considered to be of great importance in conservation of the composite-dentin bond.

Hydrolytic Degradation of Dental Composites

Abstract: The leakage of filler elements from four composites after storage in water was investigated by use of atomic absorption spectrophotometry. The results confirmed previous findings that leaching of silicon from different composites is strongly dependent on filler composition. Consideration of the total filler surface of each composite material indicated that quartz as well as pyrolytic silica-containing composites leached less silicon than did composites containing fillers of strontium and/or barium glasses. A correlation between leakage and crack formation in the matrix appeared to exist for all composites except for the microfilled resin. These cracks were explained as a result of osmotic pressure built up at the matrix-filler interface due to hydrolytic degradation of the filler. Of the investigated materials, the microfilled resin was found to be the most stable material in a wet environment with respect to crack formation. This finding was explained by filler composition, filler form, and the specific structure of the microfilled resin.

Relaxation of Polymerization Contraction Stresses by Flow in Dental Composites

Abstract: The hardening stresses in wall-to-wall bonded composites were measured and related to calculated values obtained from freely shrinking materials. Since the ultimate tensile strength of the materials contracting under restricted conditions was not lower than that of composites which were not hindered during the polymerization shrinkage, the conclusion was drawn that the contraction was compensated for by flow instead of internal disruptions.

Host responses in periodontal diseases.

Abstract: Great progress has been made in our understanding of the pathogenesis of periodontal disease, the primary role of bacteria as etiologic agents, and the critical modifying role of host responses. It is useful to consider several stages in the pathogenesis of periodontal disease - (a) colonization, (b) invasion, (c) destruction, and (d) healing - and to place into perspective the various host responses as they may affect each of these four stages (Table 5). With respect to colonization, although very little direct evidence is available, it is reasonable to suggest that antibodies, either secretory or serum-derived, acting by virtue of their ability to block attachment, could inhibit colonization by immune reduction of adherence mechanisms. With respect to invasion of the tissue, it appears that phagocytes, particularly the neutrophils, are important, acting in concert with opsonic antibody and complement in ingesting and killing the periodontal microflora before or during the early invasive process. A major advance in our understanding of the pathogenesis of periodontal diseases is the realization that the virulence of periodontopathic bacteria relates to their leukaggressive properties, allowing them to evade neutrophil protective mechanisms. Invasion of the periodontal tissues by bacterial products may be inhibited by the complexing of these products with antibody with the formation of antigen-antibody complexes that are phagocytosed and digested, particularly by scavenger phagocytes such as the macrophage. With respect to the destructive phase of periodontal disease, it is clear that the direct effect of lymphocytes mediated either through direct cytotoxic activity, or through biologically-active destructive lymphokines (such as alpha-lymphotoxin and osteoclast activating factor), can lead to tissue destruction. Macrophages, through the production of monokines, collagenase, and reactive oxygen species, can also lead to tissue destruction. The direct effects of bacterial toxins or enzymes which can lead to tissue destruction can be inhibited by complexing with antitoxic or enzyme-neutralizing antibodies. With respect to healing and fibrosis, very little direct information is available; however, it is possible that the lymphocytes and macrophages affect fibrosis by the production of chemotactic factors for fibroblasts which would be expected to bring them to the area of periodontal inflammation and also by production of fibroblast-activating factors, which then cause the fibroblasts to proliferate and produce collagen which replaces lost collagen or results in fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-term F Release from Glass Ionomer Cements

Abstract: Fluoride release from three commercial glass ionomer filling cements and three glass ionomer luting cements was measured in the laboratory over a 12-month period. Fluoride release from these glass ionomer cements was compared with that released from a silicate, silicophosphate, and a fluoride-containing polycarboxylate cement. The fluoride released from the glass ionomer cements throughout the one-year period was similar, both in quantity and pattern, to that released by the silicate cement. The silicophosphate cement tended to release fluoride in somewhat lesser amounts, while the amount of fluoride released by the polycarboxylate was negligible after the first few days. Analysis of these data indicates that these glass ionomer cements probably possess anticariogenic properties similar to those of silicate cement.

Fourier Transform Infrared Analysis of Degree of Polymerization in Unfilled Resins—Methods Comparison

Abstract: Two methods of transmission Fourier Transform Infrared analysis were compared to determine the degree of polymerization (DP) in unfilled Bis-GMA-based dental resins. Diluent concentration, curing mode, and activator type were investigated. DP ranged from 55-72% and was highest for the most diluted resins. The effects of polymerization activation mode and type were insignificant. DP was slightly enhanced in the bulk of the resin, as determined by a KBr-pellet technique, in comparison with results from a thin film method, but both techniques seem to provide useful and reproducible results for dental resins.

Bond Strength between Dentin and Restorative Resins Mediated by Mixtures of HEMA and Glutaraldehyde

Abstract: We investigated the bond strength between restorative resin and dentin pre-treated with mixtures of HEMA and glutaraldehyde. It is suggested that the mixture acts by forming a chemical bond of HEMA molecules to a collagen-glutaraldehyde reaction complex. Subsequently applied resin will then co-polymerize with the collagen-linked methacrylate groups. Statistical analysis of the results from varying mixtures of HEMA and glutaraldehyde revealed that the bond strength was highly dependent on the HEMA concentration, with a maximum at 35%, and nearly independent of the glutaraldehyde concentration when greater than 3%. The highest mean bond strength was about 1.8 kg/mm2, and bond strength of this order of size may be attractive for clinical use.

Microbial Ecology Adherent Interactions Which May Affect Microbial Ecology in the Mouth

Abstract: Bacteria attach to teeth and oral mucosal surfaces in a surprisingly selective manner, and attachment appears to be the first step in the colonization process. Attachment is thought to involve lectin-like and/or hydrophobic ligands, called adhesins, often present in bacterial surface appendages which interact with receptors on oral tissues. A variety of factors can influence bacterial attachment, and therefore have the potential to affect host-parasite interactions in the mouth. Factors discussed include salivary components, dietary lectins, and sublethal concentrations of antibiotics.

Basic Biological Sciences Unstimulated and Stimulated Parotid Salivary Flow Rate in Individuals of Different Ages

Abstract: Both unstimulated and stimulated parotid saliva samples were collected from 85 healthy, unmedicated individuals between the ages of 23 and 81 years. There were no significant differences in flow rate related to age with either unstimulated or stimulated secretion.

In vivo and in vitro Wear of Potential Posterior Composites

Abstract: The influence of cavity size, material composition, and curing mechanism on wear resistance of Class II MOD resin restorations was analyzed quantitatively. Wear resistance tends to increase both as cavity size decreases, and also from chemical- to light- to heat-cured. As to wear, among the composite resins tested, there was no acceptable resin-based amalgam substitute.

The Volume of Saliva in the Mouth Before and After Swallowing

Abstract: In 20 male and 20 female adult subjects, the volume of saliva in the mouth before (VMAX) and after (RESID) swallowing was determined. RESID could be computed by measuring the potassium and chloride concentrations in unstimulated saliva and in the expectorate after a five-second rinse with 5 ml of water immediately following a swallow. The mean value of RESID after a normal swallow was significantly higher in males (0.87 ml) than in females (0.66 ml). After a forced swallow, RESID was only slightly but significantly reduced, being 0.82 ml and 0.60 ml in males and females, respectively. The volume of saliva normally swallowed was calculated from the unstimulated salivary flow rate and the normal swallowing frequency. The mean value of VMAX (RESID plus volume normally swallowed) in males was 1.19 ml, which was slightly but not significantly higher than that in females (0.96 ml). When water was infused into the mouth at increasing flow rates, there was an increase in VMAX and in both the volume of fluid swallowed and the swallowing frequency.

The Effect of Dental Amalgam Restorations on Blood Mercury Levels

Abstract: Mercury levels in blood and in mouth air before and after chewing were measured in 47 persons with ana 14 persons without dental amalgam restorations. Questionnaires relating to exogenous sources of mercury exposure were administered to both groups. Differences in the mouth air mercury levels before and after chewing were statistically significant in the group with amalgams, but not in the group without amalgams. Analysis of the data from the questionnaires indicated that little or no exogenous exposure to mercury occurred among the two groups. Blood mercury concentrations were positively correlated with the number and surface area of amalgam restorations and were significantly lower in the group without dental amalgams.

Three-dimensional Measurements of the Occlusal Surfaces of Upper Molars in a Dutch Population

Abstract: The occlusal surfaces of the first upper molars of a Dutch population were measured three-dimensionally by moire contourography. Cusps and ridges were higher than those of a Japanese population, but distances between cuspal tips were smaller. Differences in occlusal form may influence jaw movements in the two populations.

Virulence Factors of Streptococcus mutans and Dental Caries Prevention

Abstract: Streptococcus mutans possesses the abilities to adhere to pellicle-coated tooth surfaces and to form acids - two characteristics associated with the cariogenicity of this micro-organism. De novo synthesis of insoluble glucan by S. mutans glucosyltransferase from sucrose is essential in the adherence process. Therefore, agents which interfere with the adherence ability of S. mutans would be useful for controlling dental caries. In the present report, we have summarized our recent findings concerning virulence factors of S. mutans and means for prevention of S. mutans-induced dental caries.

Effect of hydrogen sulfide and methyl mercaptan on the permeability of oral mucosa.

Abstract: Hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) are the volatile sulfur compounds (VSC) that were investigated for a possible role in the etiology of periodontal disease. The results show that the permeability of porcine non-keratinized sublingual mucosa is increased by up to 75% or 103% following exposure to H2S and CH3SH, respectively. The effect may be attributed to VSC reaction with tissue components resulting in alteration in the integrity of the tissue barrier. The increase in permeability of the mucosa to [35S]-Na2SO4 was dependent on both the time of exposure and concentration of VSC in the head-space. The [35S]-H2S was retained by the mucosal tissue and was able to penetrate the intact layers consisting of non-keratinized epithelium, basal membrane, and connective tissue. Treatment of the mucosa with 0.22% ZnCl2, either prior to or after exposure to CH3SH, nullified the effect of CH3SH and restored the permeability to a state similar to that observed in control 95% air/5% CO2 systems.

Relationships between Masticatory Muscle Cross-section and Skull Shape

Abstract: Cross-sectional areas of the masseter, temporalis and medial, and lateral pterygoid muscles were determined in 16 subjects by means of computer tomography. In each subject three scans were made, intersecting the thickest part of the muscles at right angles to the fiber direction. The masseter and medial pterygoid muscles are large in persons with brachycephalic skulls, short faces, and a small jaw angle. The cross-sectional areas of the temporalis and lateral pterygoid muscles showed no correlation with facial dimensions.

An Analysis of the Release and the Diffusion Through Dentin of Eugenol from Zinc Oxide-Eugenol Mixtures

Abstract: Tritium-labeled eugenol was released from mixtures of zinc oxide eugenol (ZOE) into aqueous solution at rates which declined exponentially with time, and which were directly proportional to the liquid-powder ratio. The release pattern was consistent with a model of progressive hydrolysis of zinc eugenolate in a limited-thickness ZOE surface layer. Intervening dentin had a profound effect on this pattern of release. In human teeth in vitro containing ZOE as a base or temporary filling, peak eugenol release at the pulpal surface of dentin was of the order of a thousand-fold less than that at the salivary surface. In such teeth, eugenol reached concentrations in excess of 10(-2) M in dentin just beneath ZOE, and 10(-4) M or less adjacent to the pulp space. Both pulpal outflow and dentin concentrations of eugenol remained relatively constant for more than a week, unlike release into aqueous solution. While these data were derived from studies on human teeth in vitro, they give a strong indication of probable events in vivo, and appear to provide a basis for the explanation of the paradox of the therapeutic and toxic actions of ZOE.

Clinical Science Cusp Reinforcement by the Acid-etch Technique

Abstract: Strain gauges were mounted on 12 maxillary pre-molars which were subjected to a sequence of restorative procedures for MOD preparations. An occlusal stress was applied using servohydraulics, and the cuspal flexure was assessed using a strain gauge. Two bonded and three non-bonded restorative procedures were tested for each tooth. The two bonded conditions showed significantly higher cuspal reinforcement when compared with the MOD preparation and the non-bonded restorative procedures. The non-bonded restorations showed some intragroup differences, with one non-bonded composite showing useful cuspal reinforcement. However, this was much less than that afforded by the bonded technique. The deformation of the cusp under occlusal force in restorations bonded by the acid-etch technique showed much less hysteresis when compared with non-bonded restorations.

Build-up and Repair of Light-cured Composites: Bond Strength

Abstract: Interfacial bond strengths of light-activated composites were measured as a function of age using a transverse strength test. Bond strength between layers decreased with the age of the initial layer and reflected the setting curves of the composites. The highly-filled composites exhibited the greatest bond strengths. Uncut surfaces provided a better substrate for bonding than did ground surfaces. Use of a bonding agent on both uncut and ground surfaces improved bond strengths. Mean repair strengths of light-activated composites were similar to those of selfcuring composites. Composites with ground surfaces aged for one wk had mean repair strengths 27% of the cohesive strength without bonding agent and 48% with bonding agent.

Dental Fear and Avoidance: A Comparison of Two Modes of Treatment

Abstract: Ninety-nine individuals, all of whom had long avoided dental treatment due to severe dental fear, received therapy according to one of two treatment modalities - behavioral therapy from a psychologist (BT) and treatment under general anesthesia (GA) - both of which were followed by clinical training and dental test treatments. These treatment programs were followed by referring the individuals to community dental clinics for complete oral rehabilitation.Among BT patients, significantly more (92%) completed the treatment program, compared with the GA patients (69%). Complete oral rehabilitation in community dental clinics was achieved by 78 and 53%, respectively. BT patients also had a significantly lower frequency of cancellations. The reduction in dental anxiety according to the Corah Dental Anxiety Scale was substantial in both groups, but the anxiety was significantly more reduced for BT patients, who reached a level equivalent to that of average dental patients. Patients' self-reported tension and the...

Basic Biological Sciences Effect of Eugenol on Respiration and Division in Human Pulp, Mouse Fibroblasts, and Liver Cells in vitro

Abstract: Eugenol depressed cell respiration in homogenates of human dental pulp and in mouse fibroblast monolayers. The depression was concentration-dependent, with a threshold at about 10(-4)M and a maximum at 10(-3)M in both preparations. Onset of the depression appeared to be rapid. The effects of variation in both duration and concentration of eugenol exposure on subsequent uptake of 3H-thymidine were examined in mouse fibroblast monolayers and human pulp explants. Fibroblasts survived short-term (up to 12 hr) exposure to 10(-3)M eugenol or less, but died after exposure to 10(-3)M for one day or more. The cells survived exposure to 10(-4)M for ten days, the longest period examined. Human pulp maintained in tissue culture medium showed similar eugenol susceptibility. Analysis of these data, when coupled with those of previous studies on eugenol release from ZOE and diffusion through dentin, gives strong support for the concepts that: the blandness of ZOE when applied to intact dentin is due to eugenol reaching the pulp in sub-toxic concentrations, and the irritant effect of ZOE when applied directly to soft tissue is due to the development of concentrations of eugenol in tissue adjacent to ZOE sufficient to inhibit respiration and thus kill cells.

Materials Science Subsurface Damage Layer of in vivo Worn Dental Composite Restorations

Abstract: Dental composite restorations have been examined using a silver staining method to elucidate in vivo wear mechanisms. Emphasis was placed on examination of material immediately beneath the wearing surfaces. Several in vitro tests were also investigated for their ability to generate in vivo-like surface defects. For all the clinically worn composite restorations, a porous layer has been observed beneath those surfaces exposed to the oral environment. A laboratory test using certain substances to simulate the oral environmental effects can reproduce this porous layer. These results suggest that the in vivo wear process of dental composites is one accelerated by environmental softening of the composites.

Nerve Regeneration Through Collagen Tubes

Abstract: Severe nerve injuries may require microsurgical grafting to span a defect. Introduction of graft material into a highly vascular recipient bed is documented to aid in early regeneration of neuronal blood supply.A silicone rod (SR)-induced fibrovascular sheath was employed to evaluate the regeneration of rat tibial nerve through 2-mmdiameter collagen tubes (CT) or contralateral nerve autografts (AUTO). At first operation, 5 mm of right tibial nerve was resected from 30 retired male breeder Sprague-Dawley rats. Resected nerve was replaced with either a 5 x 2 mm SR or the nerve ends were sutured to the intermuscular fascia.Four weeks later, animals were repaired by replacing the SR with either a CT or a contralateral AUTO from the left tibial nerve. Three months later, EMG testing was performed, and histologic sections were prepared.The EMG latency and the size of the compound action potential for sheathed or non-sheathed CT or AUTO were statistically superior to controls at the 95% confidence level. All oth...

Basic Biological Sciences Relationship between Concentration of Human Salivary Statherin and Inhibition of Calcium Phosphate Precipitation in Stimulated Human Parotid Saliva

Abstract: Human salivary secretions are supersaturated with respect to the calcium phosphate salts which form dental enamel, a property which provides important protection for the teeth. We previously proposed that statherin, a 43-residue phosphopeptide, plays a key role in this protective system by inhibiting or delaying potentially harmful precipitation of calcium phosphate salts in the salivary glands and mouth. The purpose of the present study was to determine if the concentrations of statherin in saliva, despite their wide normal range, are high enough to fulfill this function. Concentrations of statherin in stimulated human parotid saliva samples from 36 female and 32 male subjects, aged from 17 to 30 years, were determined by a single radial immunodiffusion method. Values found ranged from 3.0 to >27.3 μM, with a mean value of 12.8 (S.D. ± 5.46) μM.At concentrations below these values, statherin inhibited spontaneous precipitation of calcium phosphate salts from an assay system which was more supersaturated ...

Dental Disease and Work Loss

Abstract: Few studies have analyzed dental diseases in terms of their social impact. This study explored the feasibility of a social outcome measure, work absence. 2600 employed people in the Hartford (CT) area were interviewed by 'phone using Random Digit Dialing methodology. While dental disability did not affect the majority (75%) of those workers interviewed, 25% reported an episode of work loss in the past 12 months related to dental problems and dental treatment visits. Workers lost an average of 1.7 hours. The prevalence and magnitude of work loss were sensitive to several sociodemographic, access, and health-related factors.

Effects of Local Anesthetics on Pulpal Blood Flow in Dogs

Abstract: Effects of 2% lidocaine with epinephrine (1:100,000) administered by the various local anesthetic techniques--i.e., infiltration, mandibular block, and intraseptal injection--on pulpal blood flow in dogs were determined using the 15 microns radioisotope-labeled microsphere injection method. The pulpal blood flow decreased significantly with all three techniques; however, the most drastic reduction occurred in the molar teeth with the intraseptal injection. When 2% lidocaine without epinephrine was used in the intraseptal injection, pulpal blood flow increased significantly.

Computer Correction of Projective Distortions in Dental Radiographs

Abstract: Distortions in radiographic images caused by changes in shape and position of the film relative to the x-ray beam can result in registration artifacts which interfere with interpretation of subtracted images.A warping transformation is described which maps known points of reference in one image into homologous points in another. The corrected image pair can then be superimposed and subtracted with significantly-reduced differences in registration to facilitate the detection of localized changes of diagnostic interest.

Whole-saliva secretion rates in old and young healthy subjects.

Abstract: Resting and stimulated whole-saliva secretion rates were compared in old and young healthy volunteers. The stimulated secretion rate was similar in both age groups, while the resting flow rate was significantly lower in the old females and males as compared with rates in the young.

The Surface Roughness and Gloss of Composites

Abstract: The contrast gloss and the average roughness were measured for four commercial composite filling materials. Using a factorial design, each material was subjected to four available finishing methods. A significant difference was found in the contrast gloss among finishing methods, and a significant linear regression is given which relates the inverse of the contrast gloss to the average roughness. Surface gloss is proposed as playing a major role in the esthetic appearance of composite restorations.