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Biomedical subjects

S C Bayne

Publications and source records attributed to S C Bayne.

At least 19 recordsLinked to original sources
PubMed1992

Marginal fit of castable ceramic crowns.

The objective of this study was to measure marginal fit of castable ceramic versus gold crowns. Full veneer gold and ceramic crowns were made on Ivorine dies. Crowns were cemented, embedded, sectioned faciolingually and mesiodistally, and photographed for measurement of absolute marginal discrepancies (cavosurface angle to casting margin) to evaluate fit. Results revealed no statistically significant differences in fit among four locations around the margins of either ceramic or gold crowns. There was no statistically significant difference in the combined absolute marginal discrepancy (fit) between ceramic and gold crowns. The variance of the combined absolute marginal discrepancy (fit) of the ceramic crowns was significantly different than that of the gold crowns (p = 0.01 level). The standard deviation (variability) of the gold crowns was more than twice that of the ceramic crowns. Randomized block ANOVA demonstrated statistically significant differences among individual gold crown specimens, but none among individual ceramic crown specimens.

Analysis of Variance↗
PubMed1992

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, and some are identified as misleading. New techniques in pulp physiology and pathology are reported. Laser use and techniques in prevention, restorative dentistry, and materials use are reported. Epidemiology of selected diseases and the results of various formulations for treatment are cited. Diagnosis of craniomandibular dysfunction is well represented as well as references to literature reviews and other sophisticated scientific investigation. Research on adhesives is presented in respect to bonding agents for dentin and enamel. Several clinical studies are included, along with customary laboratory reports on several materials.

Dental Materials↗
PubMed1992

Protection hypothesis for composite wear.

Significant occlusal wear occurs on posterior composite restorations in areas without direct contact with opponent teeth (contact-free wear) in addition to wear at the contacts. Recent research has indicated that all occlusal posterior composite surfaces wear, and those surfaces show decreasing wear rates over time. This provides more evidence for an earlier theory proposed by Jørgensen et al. (1979) that composite contact-free wear is a function of access and attrition caused by small particles in the food bolus. This hypothesis is now called the "protection theory" or "protection hypothesis" for wear. Macroscopic protection or "sheltering" from wear is provided by cavity preparation walls. Microscopic protection against resin matrix wear is provided by filler particles that are close together. Clinical evidence supporting the protection hypothesis comes from recently confirmed low wear rates for microfill and hybrid composites. The objective of this work was to calculate the minimum inter-particle spacing required for microscopic protection (wear resistance) for composites based on assumptions of packing fractions (0.68) with small particles (0.02 microns radius) for dispersed versus agglomerated conditions. An inter-particle spacing (IPS) of < 0.10 microns was assumed to afford wear protection. The results are that only 1.5-6.0 volume percentage microfiller is theoretically required to generate an IPS of 0.1 micron for composite microscopic protection. However, microfiller particles are suspected to agglomerate into clusters. Modified calculations for that effect indicate that at least 35% filler is required to provide microscopic protection. This effect explains much of the 3 to 5 year clinical research results for microfills and hybrids.(ABSTRACT TRUNCATED AT 250 WORDS)

Composite Resins↗
PubMed1992

Dental composites/glass ionomers: clinical reports.

Composites and glass ionomers have not been extensively tested in clinical trials for biological safety. Most clinical evaluations have looked at other factors, such as retention, wear, or color. The primary evaluation criterion used in clinical trials is post-operative sensitivity. Sensitivity does not seem to have any correlation to pulpal inflammation. Inflammation can be the result of mechanical, thermal, chemical, and bacterial insults. It is complicated for individual contributions to be separated in short-term studies. General usage of these materials over about 20 years indicates a high benefit-to-risk ratio. Despite some complaints of sensitivity with some glass-ionomer compositions, both composites and glass ionomers are relatively trouble-free. There is no evidence of short-term or long-term risk. Toxicological studies have focused almost exclusively on pulpal reactions. Systemic reactions have not been closely examined, although there is no suspicion of any problems after virtually billions of procedures in the United States. New glass-ionomer cements are similar to contemporary composite formulations. Continued development of these materials may ultimately produce an amalgam replacement material that is economically and philosophically desirable to general dentists.

Animals↗
PubMed1991

Effect of air abrasives on marginal configurations of porcelain-fused-to-metal alloys: an SEM analysis.

Air abrasion of castings for metal ceramic crowns is a routine procedure in ceramics laboratories for cleaning, seating, and preparing casts for porcelain application. This technique can result in damage to the margins of castings. This investigation evaluated the extent and significance of this procedure. Marginal abrasion ranged from 5 to 110 microns. ANOVA, followed by Tukey's post hoc evaluation revealed no difference between abrasives, but significant differences were noted among alloys and margin configurations (p less than 0.05). Marginal loss by alloy was as follows: [Jelenko O] greater than [Olympia = Cameo] greater than [Jelstar] greater than [Genesis II]. Marginal loss by marginal configuration was as follows: [beveled shoulder] greater than [chamfer = shoulder]. Significant marginal damage can occur during air abrasion of dental castings.

Air↗
PubMed1991

Effect of in vivo crown margin discrepancies on periodontal health.

Numerous reports have suggested a relationship between marginal adaptation of dental castings and periodontal tissue health, and this study examined this relationship quantitatively. Forty-two crown restorations in 29 randomly selected patients were selected for this study using three criteria. (1) The crowns were placed at the University of North Carolina School of Dentistry; (2) the crowns were in service for a minimum of 4 years; and (3) the crown margins were within the intracrevicular crevice (subgingival). Replica impressions of the facial margins of specific crowns were made with a vinyl polysiloxane impression material, and poured casts were prepared for scanning electron micrograph evaluation. Marginal discrepancy measurements were identified on each micrograph at 10 equally spaced locations along the margin and averaged for each specimen. Periodontal indices of pocket depths, crevicular fluid volume, and gingival index were accumulated for clinical measurements. Pearson correlation and Bonferroni adjusted probability tests were performed, but no significant correlation was found between marginal discrepancy (0.16 +/- 0.13 mm) and pocket depth (2.4 +/- 0.9 mm). However, a strong correlation (p less than 0.001) existed between marginal discrepancy and gingival index (2 +/- 0.8) and between marginal discrepancies and crevicular fluid volume (49.9 +/- 31.1). These results established that a significant quantitative relationship existed between the marginal discrepancy and periodontal tissue inflammation for subgingivally located crown margins.

Adult↗
PubMed1991

A crown for clinically investigating microleakage.

This investigation evaluated a cast crown with an access port for in vivo microleakage studies. Fifteen complete cast crowns containing an access port in the facial surface were cast. The gingival margins of the crowns were modified to test the sealing ability of the access port. Each casting was thermocycled 750 times at 5 degrees to 60 degrees C over a 24-hour period. Air pressure of 90 psi followed by 28 mm Hg vacuum was applied for 1 hour each during immersion of the devices in silver nitrate solution. Castings were embedded in acrylic resin and sectioned with a diamond saw through the sealing device. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed no leakage with the 13 test devices and 100% leakage with the controls. The device should be effective for use in human subjects.

Clinical Trials as Topic↗
PubMed1991

Five-year clinical study of u.v.-polymerized posterior composites.

Four u.v.-polymerized composites (Estilux, Nuva-Fil, Nuva-Fil P.A. and Uvio-Fil) were clinically evaluated in Class I and II cavity preparations in permanent teeth. The restorations were evaluated at baseline, 1, 2, 3, 4 and 5 years using USPHS criteria for direct evaluation and at 3, 4 and 5 years using the Leinfelder method for indirect evaluation of wear. The wear measured by the USPHS method showed increasing wear rates in earlier reports, apparently due to the limited sensitivity of the scale to early wear. The wear by the Leinfelder method showed gradually decreasing wear rates. There were no statistically significant differences among the wear values for the four u.v.-cured materials or between these materials and the self-cured and visible light-cured controls.

Analysis of Variance↗
PubMed1991

Contributing co-variables in clinical trials.

To accurately compare Class V dentinal bonding studies, it is essential to critically classify the effects of the intraoral location and age of the patient on the retention of resin composite restorations. A mathematical formula for normalization combined with the Weibull analysis also is proposed that could provide CL50 values for the clinical longevity of adhesive restorations.

Adult↗
PubMed1991

Effects of air polishing on the abrasion of occlusal sealants.

Air polishing, routinely used in dental offices, is known to be abrasive to polymer-based materials. The purpose of this study was to evaluate the effect of repeated air abrasion on two types of sealants: self-curing Concise or light-curing Delton. Scanning electron micrographs were collected after 0, 10, 30, 60, and 90 total seconds of air polishing. The remaining sealant was rated by two examiners (100% agreement) as little or no loss; some loss; or most or complete loss. Statistical tests revealed no significant sealant loss at any time interval, despite the fact that some sealant loss was observed on all but three samples.

Acrylic Resins↗
PubMed1990

Correlation of M-L, Leinfelder, and USPHS clinical evaluation techniques for wear.

Most recent clinical research studies on wear of posterior composite restorations have used the USPHS and Leinfelder measuring techniques. New studies are adopting the Moffa-Lugassy (M-L) technique. However, to date there has been no means of comparing results of the different techniques. The objective of this study was to correlate the M-L scale wear values to Leinfelder scale wear values and to USPHS scale alfa-bravo transitions, so that data can be pooled across studies for comparisons. M-L evaluations were made for 221 restorations previously evaluated by the USPHS and Leinfelder methods. The M-L wear values were determined as the mean of three independent evaluators' values. At the USPHS alfa-bravo transition, the mean Leinfelder wear value was 192 microns, and the mean M-L value was 97 microns. The correlation coefficient for the linear regression of M-L values vs. Leinfelder values was 0.87. The scales were linearly related, with a slope of 0.52. The average values for M-L readings of wear were statistically different and approximately half the Leinfelder values.

Clinical Trials as Topic↗
PubMed1989

Considerations in measurement of marginal fit.

The terminology describing "fit" and the techniques used for measuring fit vary considerably in the literature. Although fit can be most easily defined in terms of "misfit," there are many different locations between a tooth and a restoration where the measurements can be made. In this work, the measurements of misfit at different locations are geometrically related to each other and defined as internal gap, marginal gap, vertical marginal discrepancy, horizontal marginal discrepancy, overextended margin, underextended margin, absolute marginal discrepancy, and seating discrepancy. The significance and difference in magnitude of different locations are presented. The best alternative is perhaps the absolute marginal discrepancy, which would always be the largest measurement of error at the margin and would reflect the total misfit at that point.

Dental Cavity Preparation↗
PubMed1989

Comparison of direct and indirect methods for analyzing wear of posterior composite restorations.

The vast majority of recent clinical research involving wear analyses of posterior composite resin restorations have used either the direct evaluation method (USPHS) or the indirect cast comparison (Leinfelder) method. However, there has never been any established correlation of the two wear scales. The objective of this study was to determine the amount of wear for the USPHS alfa-bravo transition on the basis of cast comparison data. Clinical wear data were collected over five years by both the direct method and the indirect method. Three materials were used involving a total of 221 restorations in 61 patients. Each restoration was evaluated at baseline, six months, one, two, three, and five years by each method. Then, for those restorations which underwent a transition from an alfa to a bravo clinical rating, the absolute wear at the transition was determined by averaging the indirect ratings just before and just after the transition. The mean wear corresponding to the alfa-bravo transition was 192 +/- 60 microns. Because of the large width of the alfa category up to the alfa-bravo transition, extensive early changes and high initial wear rates cannot be detected by the USPHS system.

Bicuspid↗
PubMed1989

Bonding to resurfaced posterior composites.

Despite significant improvements in the wear resistance of posterior composite restorations, they still undergo occlusal wear, color change, and surface staining with time. One method of repairing these restorations is re-surfacing the old composite. This study investigated the bonding of new composite to the corresponding old composite material by several different mechanical conditioning steps, chemical conditioning steps, primer conditioning steps, and four posterior composites. Aged composite surfaces were conditioned, re-bonded to new composite, stored in artificial saliva for seven days at 37 degrees C, and tested in shear. The mean shear strength for unrepaired composites was 27 MPa. Optimal re-bond strengths were 88% (Estilux), 77% (Ful-Fil), 92% (Occlusin), and 102% (P-10) of original bulk shear strengths. General linear modeling revealed that the best combination tested was roughening with a D830 diamond bur, conditioning the surface with water, and priming with Scotchbond-1 dentin bonding agent.

Composite Resins↗
PubMed1989

Three-year clinical evaluation of a self-cured posterior composite resin.

A study was conducted to determine whether the wear resistance of a posterior composite could be improved by maximizing filler particle-to-particle contacts. This was expected to reduce stress concentrations on the resin matrix and thus reduce occlusal wear. A self-curing quartz-filled composite with this design, P-10, was used to restore 90 Class I and II cavity preparations in adult teeth. Restorations were recalled after baseline at six months, one year, two years, and three years to measure wear by direct and indirect evaluation methods. There was no apparent advantage for this material compared with other previously evaluated posterior composites. The average cumulative wear for P-10 after three years was 145 microns. In addition, the restorations were evaluated for color-matching, interfacial staining, secondary caries, marginal adaptation, surface texture, and postoperative sensitivity. This material was not significantly different in those ways from other posterior composite products except in terms of more rapid color change, because it is self-cured.

Bicuspid↗