Faculty Bibliography

The purpose of this study was to compare three-dimensional laser digitizing with subjective evaluations of wear in posterior resin-based composite restorations during a 24-month period. BACKGROUND: The authors describe an indirect method of analyzing wear in resin-based composite restorations. A computer-driven laser was used to scan stone casts of restorations and create three-dimensional computerized surface models of the teeth. A standard computer algorithm was used to superimpose the follow-up model images over the baseline model images and to calculate the amount of wear within 10 micrometers. METHODS: Patients were selected whose treatment plans required a Class II restoration. A total of 100 restorations were inserted at baseline and evaluated at six months, 12 months and 24 months. Polyether quadrant impressions were taken and casts were made. Twenty-one casts were selected for the three-dimensional laser digitizing technique. The same casts were evaluated via subjective evaluations using sets of 18 calibrated standard models, following the method developed by Leinfelder. RESULTS: Statistical analysis using the Wilcoxon test revealed significant differences (P < .01) between subjective wear evaluation and the three-dimensional laser digitizing wear analysis. CONCLUSION: The normalized three-dimensional laser digitizing technique is significantly more effective than subjective evaluations in establishing restoration wear rates

The purpose of this in vitro microleakage study was to evaluate four low-viscosity composite resin systems. Each resin system included the corresponding bonding agent for each respective flowable composite. A hybrid material was used as a control. A total of 75 noncarious, freshly extracted human teeth were prepared with a Class 5 occlusal preparation and a gingival preparation at the cementoenamel junction. The materials were inserted according to the manufacturers' recommendations using the single-component bonding agent for each system. Teeth were thermocycled 800 times between 5 degrees C and 55 degrees C with 30-second dwell times. The teeth were then coated with nail polish 1 mm short of the restoration, placed in a basic fuchsin dye for 24 hours, and sectioned with a diamond wheel. Enamel and dentin/cementum margins were analyzed for microleakage on a scale of 0 (no leakage) to 3 (axial wall). Results were evaluated with the Fisher's exact test. The results of the study indicate that there was no leakage at the enamel margin of any restorations. No statistically significant differences in microleakage were found in dentin/cementum margins among the samples in the experimental group or between the experimental group and control group. The results indicate flowable composites demonstrate resistance to microleakage in both enamel and cementum/dentin margins similar to TPH hybrid composite

PURPOSE: To compare the adhesion of a flowable resin-based composite (RBC) vs. a condensable RBC to tooth structure using scanning electron microscopy (SEM). MATERIALS AND METHODS: Fifteen recently extracted human teeth were prepared for Class I restorations and equally divided into three groups. Group 1 was filled with Heliomolar bonded with Syntac Single Component. Group 2 was lined with Flow-It in addition to ALERT condensable RBC bonded with Bond-1 Primer/Adhesive. Group 3 was filled with ALERT bonded with Bond-1 Primer/Adhesive. All teeth were thermocycled, sectioned and evaluated for gap formation with the SEM. RESULTS: SEM at x15 demonstrated that restorations with the flowable RBC at the tooth/restoration interface showed no evidence of marginal gaps between the RBC material or at the underlying tooth structure. A significant difference (P < 0.05) in wall adaptation was found between Groups 2 and 3

OBJECTIVE: The purpose of this investigation was to evaluate microleakage in Class II cavities restored with the condensable resin composite SureFil, placed with or without a liner and 1 of 2 different dentin bonding agents. METHOD AND MATERIALS: Extracted noncarious human teeth were randomly divided into 4 groups of 15 each and restored according to manufacturer's instructions: group 1, SureFil and Prime & Bond NT; group 2, SureFil and PQ1; group 3, SureFil, PermaFlow, and PQ1; group 4, Heliomolar and Syntac Single-Component (control). Specimens were stored in 37 degrees C water for 24 hours. All specimens were thermocycled between 5 degrees C and 55 degrees C for 500 cycles. Each specimen was immersed in 0.2% basic fuchsin dye for 24 hours and then sectioned longitudinally and horizontally. Dye penetration at enamel and cementum margins were viewed at x30 magnification by 2 independent, calibrated evaluators. Specimens exhibiting dye penetration > or = 0.1 mm beyond the cavosurface margin were considered to have leakage. RESULTS: Chi-square tests revealed no statistically significant differences in the presence of microleakage when all groups were analyzed together. However, 2 by 2 comparisons revealed that group 3 had significantly fewer specimens with microleakage than did group 1, 2, or 4. CONCLUSION: To limit microleakage, a flowable composite should be used as a liner when a condensable composite material is used

Low bond strength between tooth structure and restorative ceramic material is a major cause of ceramic fractures or failures. Prebonding measures performed on pressable ceramic material were evaluated and the different shear bond strengths obtained by each method were tabulated. The three individual groups were subjected to 9% hydrofluoric (HF) acid gel for 0, 1, and 5 minutes. The different acid-etched time groups were chemically treated with silane coupler alone, silane coupling agent with bonding agent, and bonding agent alone. The silane coupling agent produced the highest bond strength between the composite structure and the pressable ceramic restorative material. High bond values were achieved by etching the porcelain for one minute. The use of the silane coupling agent with a one minute 9% HF acid etch yielded the greatest bond strength

The purpose of this scanning electron microscope study was to observe the dentin-amalgam interface after utilizing a standard restorative liner and a single-component dentin adhesive. Continuous interface gaps of over 15 mu were observed in specimens containing no lining and Copal varnish. Discontinuous 5 microns gaps were observed in specimens treated with PQ1. Additionally, specimens treated with PQ1 exhibited resin interpenetration into the dentin surfaces

PURPOSE: To examine and evaluate the topographies of Vita Mark II and Dicor MGC surfaces by SEM after simulating the common clinical procedures. MATERIALS AND METHODS: Twelve (12) samples of Dicor MGC and 12 samples of Vita Mark II were milled on a Cerec, a computer-controlled machine. Three cut surfaces were observed and photographed using a scanning electron microscope following standardized milling, etching and polishing procedures. RESULTS: The surface topographies of the ceramic restorative materials showed distinctly different characteristics. Dicor MGC showed definite shaped crystals after etching. The surface characteristics of etched Dicor MGC were different than etched Vita Mark II, which exhibited large trabeculations. The occlusal and proximal surfaces, which were not etched but polished, displayed large vacuoles with Vita Mark II while smaller vacuoles were seen in the fused crystals of Dicor MGC