John R. Sturdevant

Examining Tooth Flexure Effects on Cervical Restorations: A Two-Year Clinical Study

This study evaluated the clinical performance of dentinal adhesives in seven various material/technique combinations. No statistically significant differences were observed among the restorative combinations, or among technique variables after two years in terms of retention, sensitivity or USPHS categories. However, other factors related to tooth flexure--such as occlusal stress, patient age, restorative material and restoration location--showed statistically significant associations with retention failures. These results support a tooth flexural theory of restoration retention.

Fracture resistance of prepared teeth restored with bonded inlay restorations

STATEMENT OF PROBLEM intact, prepared, and restored human maxillary premolars. MATERIAL AND METHODS Fifty intact, noncarious human maxillary premolars were divided into 5 groups of 10 and were mounted with their roots imbedded in autopolymerized acrylic. In the first group, the teeth were intact with no preparation. In the other 4 groups, Class II MOD preparations were made with a water-cooled high-speed hand piece. In 1 group, the cavity preparations were restored with bonded CAD/CAM ceramic inlays. In 2 groups, the preparations were restored with bonded CAD/CAM composite inlays (acid etched or air particle abraded). In the final group, the teeth were prepared but unrestored. Specimens were tested individually in a universal testing machine, in which a 4.82-mm-diameter steel sphere plunger was mounted in the crosshead moving at 0.5 mm/min. The plunger contacted the facial and lingual triangular ridges beyond the margins of the restorations. Peak load to fracture (N) was measured for each specimen. Means were calculated and analyzed with analysis of variance (P</=.05). RESULTS MOD preparations weakened the teeth by approximately 59%. Restoring the teeth with ceramic or composite inlays did not significantly strengthen the teeth under this testing system. Of the restored teeth, those restored with indirect composite inlays cemented following manufacturers recommendations had the highest fracture resistance. CONCLUSION Within the limitations of this study, under static compression load testing, bonded inlay restorations did not strengthen maxillary premolars with large MOD preparations.

Clinical Evaluation of an All-in-one Adhesive in Non-Carious Cervical Lesions with Different Degrees of Dentin Sclerosis

This randomized clinical trial compared the performance of an all-in-one adhesive (iBond) applied in sclerotic and non-sclerotic non-carious cervical lesions with that of a three-step etch-prime-bond adhesive (Gluma Solid Bond, SB). One-hundred and five lesions were randomly assigned to four groups according to adhesive, sclerosis scale and technique: 1) SB applied to lesions with sclerosis scale 1 and 2 (n=26); 2) iBond applied to lesions with sclerosis scale 1 and 2 (n=28); 3) iBond applied to lesions with sclerosis scale 3 and 4 (n=25) and 4) iBond applied with prior acid-etching to lesions with sclerosis scale 3 and 4 (n=26). A microfilled composite (Durafill VS) was used as the restorative material. The restorations were evaluated for retention, color match, marginal adaptation, anatomic form, cavosurface margin discoloration, secondary caries, pre- and post-operative sensitivity, surface texture and fracture at insertion (baseline), 6, 18 months and at 3 years using modified USPHS evaluation criteria (Alfa=excellent; Bravo=clinically acceptable; Charlie=clinically unacceptable). There was a high percentage of Bravo scores for marginal adaptation (4%-32%) and marginal discoloration (18%-60%) in Groups 2, 3 and 4, but all groups had <5% Charlie scores at 6 months and <10% Charlie scores at 18 months for retention and marginal discoloration, respectively. However, it should be noted that 13% of the restorations in Group 4 were not retained at three years.

Five-year study of two lightcured posterior composite resins

Abstract Two visible light-cured composite resins, Ful-Fil and X-55, were used to restore 136 Class I and Class II cavity preparations in adult teeth. After 5 years the ratings for color matching, interfacial staining, secondary caries, and marginal adaptation remained good, using USPHS criteria (ranging from 75% to 100% Alfa). The average surface loss due to occlusal wear was 158 and 169 micrometers for Ful-Fil and X-55, respectively. Significant differences in occlusal wear were noted depending on tooth and restoration type. These results indicate that both composite resins meet the current ADA Council on Dental Materials specifications for full acceptance in adult posterior teeth.

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.

Three-year study of two light-cured posterior composite resins

Abstract Two visible light-cured composite resins, Ful-Fil and X-55, were used to restore 136 Class I and Class II cavity preparations in adult teeth. After three years, the ratings for color matching, interfacial staining, secondary caries, and marginal adaptation remained good using USPHS criteria (ranging from 72% to 100% Alfa). The average surface loss due to occlusal wear was 145 and 164 micrometers for Ful-Fil and X-55, respectively. These results indicate that Ful-Fil composite resin meets the current ADA Council on Dental Materials specifications for provisional acceptance in adult posterior teeth.

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.

Bond strengths of resin-bonded metal castings

Abstract Composite resin-retained appliances are susceptible to failure at the resin-metal interface. The objective of this study was to evaluate bond strengths of perforated and electrolytically etched framework designs by subjecting them to tensile and shear loading. Shear bond strengths were always higher than tensile bond strengths. Etched castings were consistently stronger than perforated designs. Castings that were both perforated and etched were stronger in tension than all other retentive designs.

Conservative preparation designs for Class II amalgam restorations.

Abstract This study evaluates whether improvements in the physical properties of dental amalgam affect the use of Class II preparations without an occlusal dovetail. Four amalgam alloys were selected providing combinations of particle shape and copper content. The amalgams were characterized for their 24-h compressive and tensile strengths. High-copper amalgams were significantly stronger in compression, but weaker in tension than low-copper amalgams. Five Class II preparation designs were evaluated in cast metal replicas of prepared teeth. Controlling for the amalgam used, the proximal boxonly designs required significantly higher loads for restoration failure than did designs with occlusal dovetails. Of the two physical properties tested prior to the metal die tests, tensile strength was more predictive of load required for restoration failure than compressive strength. Neither copper content nor particle shape of the alloys had a discernible effect on load required for restoration failure. The results indicate that box-only restorations should be tested clinically for their suitability in routine operative dentistry.

Thermal effects on retention of resin-bonded retainers

Abstract Composite resin-retained, fixed partial dentures are subjected to a wide range of temperatures in the oral cavity. The objective of this study was to evaluate the effect of thermocycling on bond strengths of perforated and electrolytically etched resin-bonded retainers. Shear bond strengths of both retainer designs were adversely affected by thermocycling while tensile bond strengths remained unaltered. Bond strengths of electrolytically etched castings were consistently stronger than those of the perforated design.