A comparison of the retention of three endodontic dowel systems following different surface treatments.

PURPOSE: Practitioners have several options during the selection of a dowel for core restoration, including metal and glass fiber materials. Retention of the cemented dowel is critical for the success of this type of restoration. The purpose of this in vitro study was to evaluate the effect of two surface treatments on the retention of three types of dowels placed into prepared canals with a resin cement. MATERIALS AND METHODS: Following the removal of the clinical crown, gutta percha was used to restore canals prepared to size 40 in 90 extracted human anterior teeth. The access openings were then sealed, and the teeth stored in water for 3 weeks at 37 degrees C. Post preparations were made to a depth of 9 mm, and parallel ParaPost, FibreKleer, and FibreKor dowels were each used to restore 30 teeth. Ten dowels in each group received no surface roughening treatment, 10 were air abraded with 50 mu aluminum oxide, and 10 were air abraded with CoJet. The specimens were stored in water for 24 hours at 37 degrees C following dowel placement and prior to debonding with an Instron Testing Machine. RESULTS: The forces (N) required in tensile load to dislodge the dowels for each group were: ParaPost/CoJet 214.04 +/- 91.72, FibreKleer/AlOxide 196.07 +/- 57.69, ParaPost/AlOxide 184.46 +/- 35.05, FibreKleer/CoJet 176.36 +/- 42.43, FibreKor/AlOxide 174.32 +/- 53.64, ParaPost/Unroughened 174.14 +/- 40.74, FibreKor/CoJet 167.16 +/- 35.94, FibreKor/Unroughened 116.69 +/- 37.01, and FibreKleer/Unroughened 96.88 +/- 33.45. Post hoc analysis demonstrated that the unroughened FibreKor and FibreKleer dowels had significantly less retention than all other test groups (p < or = 0.05). CONCLUSION: Surface roughening with air abrasion increases retention in dowels cemented with a resin cement. Both the aluminum oxide and CoJet systems were equally effective in this regard.

Effect of polymerization mode of adhesive and cement on shear bond strength to dentin.

PURPOSE: To investigate the shear bond strength to dentin when two resin adhesive systems in light-cure, dual-cure, and auto-cure modes were used with three resin cements. This was done to determine the degree of compatibility that exists when resin products with different polymerization mechanisms are used together. METHODS: Three hundred non-carious human molars were divided into 30 test groups in which Prime & Bond NT and ScotchBond Multi-Purpose were used as adhesives with Calibra, Nexxus and Variolink cements to attach Rexillium III posts to flattened dentin surfaces. Debonding was achieved with an Instron testing machine and mean shear bond strengths were determined for each test group. The data were subjected to three-way ANOVA and post-hoc LSD testing to determine whether significant differences existed between the test groups. RESULTS: Bond strengths achieved were affected by the adhesive, the cement, and the cement curing mode. In general, the auto-cure application of the three cements demonstrated reduced shear bond strengths, both with respect to the different adhesives and their curing modes as well as compared to the dual-cure technique of the same cement. Additionally, Prime & Bond NT demonstrated considerably more variability than ScotchBond Multi-Purpose when used with both dual-cure and auto-cure varieties of the three cements. The bond strengths of resin cements depend on the curing mode of the cement and the adhesive. Unlike with direct light-cured resin composites, combining adhesive systems and dual-cured resin cements from different manufacturers may be contraindicated.

Microtensile bond strength of total-etch and self-etch adhesives to the enamel walls of Class V cavities.

PURPOSE: To determine the difference in microtensile bond strengths (MTBS) of resin-based composite bonded to the enamel of cavity preparations using a conventional or a self-etching adhesive. METHODS: Buccal and lingual Class V cavities were prepared in each of 12 caries-free human molars. Six teeth were randomly selected to be restored with Spectrum TPH resin-based composite and Prime & Bond NT adhesive. The remaining six teeth were restored with the same composite and Prompt L-Pop self-etching adhesive. Enamel/composite sticks were cut from each specimen and subjected to microtensile bond testing. Each debonded specimen was evaluated by SEM to determine the mode of failure. RESULTS: The mean MTBS for Prime & Bond NT specimens was 15.2+/-13.1 MPa. The mean MTBS for Prompt L-Pop self-etching adhesive samples was 18.2+/-14.3 MPa. ANOVA demonstrated no statistically significant difference between the mean MTBS associated with the two adhesives (P> 0.05). The results of SEM analysis revealed that the bonding failures occurred primarily at the interface between the adhesive and the enamel, suggesting a primarily adhesive failure.

An accelerated in vitro model for adhesive testing.

PURPOSE: To develop a pilot in vitro accelerated laboratory testing protocol for assessing marginal sealing capability of dental adhesives. METHODS: Occlusal cavities were prepared in 20 human molar teeth and restored with Spectrum TPH resin composite. Prime & Bond NT and Prompt L-Pop served as the adhesive for eight teeth each. An experimental self-etching adhesive system was used on the remaining four teeth. Each specimen was subjected in sequential fashion to the following challenges: 400,000 wear cycles in a Leinfelder simulator; 5000 thermocycles between water baths maintained at 5 degrees C and 55 degrees C with a dwell time of 40 seconds in each; and a repetition of the 400,000 wear cycles. Polyvinyl siloxane impressions were made at baseline and after each challenge. Microleakage was assessed following silver nitrate staining and marginal degradation was evaluated using light microscopy and the stone casts made from the impressions taken during the project. RESULTS: Microleakage analysis yielded the following median leakage values: Prime & Bond NT - 0; Prompt L-Pop - 1; and experimental self-etching adhesive - 3. The Wilcoxon sign rank test demonstrated significant differences between all three adhesives (P < or = 0.05). Evaluation of the stone casts demonstrated that marginal gaps were more prevalent after the second wear challenge.

Gender-based differences in satisfaction with academic preparation and practice experiences.

The purpose of this study was to investigate the effect that practice patterns and other variables had on graduates' level of satisfaction with dental school preparation and satisfaction with several career experiences and to determine if any gender-based differences occurred in these findings. Dentists who graduated from Creighton University School of Dentistry between 1985 and 2005 were surveyed regarding demographic factors, practice characteristics, satisfaction with educational preparation, and satisfaction with practice experiences. The response data were analyzed using Spearman's rho, multiple regression analysis, and the Pearson product moment. As a result of this analysis, no statistically significant differences were found between male and female dentists who graduated from Creighton University between 1985 and 2005 with respect to satisfaction with academic preparation and postgraduation practice experiences. The findings indicate that gender is not associated with graduates' level of satisfaction with their academic preparation while in dental school and their practice experiences.