Faculty Bibliography

PURPOSE/OBJECTIVE:To evaluate the effect of tray-based and trayless tooth whitening systems on surface and subsurface microhardness of human enamel. METHODS:Enamel slabs were obtained from recently extracted human third molars. Specimens were randomly assigned to six groups according to tooth whitening treatment (n = 10): 6.0% hydrogen peroxide (HP) (Crest Whitestrips), 6.5% HP (Crest Professional Whitestrips), 7.5% HP (Day White Excel 3), 9.5% HP (Day White Excel 3), 10% carbamide peroxide (Opalescence), and a control group (untreated). Specimens were treated for 14 days following manufacturers' recommended protocols, and were immersed in artificial saliva between treatments. Enamel surface Knoop microhardness (KHN) was measured immediately before treatment, and at days 1, 7, and 14 of treatment. After treatment, subsurface microhardness was measured at depths of 50-500 microm. Data were analyzed for statistical significance using analysis of variance. RESULTS:Differences in microhardness for treated vs. untreated enamel surface were not statistically significant at any time interval. For 6.5% and 9.5% HP, there was a decrease in surface microhardness values during treatment, but at the end of treatment the microhardness values were not statistically different from the baseline values. For the enamel subsurface values, no differences were observed between treated vs. untreated specimens at each depth. Trayless and tray-based tooth whitening treatments do not significantly affect surface or subsurface enamel microhardness.

This study evaluated the influence of (1) different dentin treatments and (2) storage time on dentin shear bond strengths. Two hundred and twenty-five bovine incisors were collected, ground to expose a flat dentin surface and randomly divided into three groups according to dentin surface treatment: (1) Total etch + Single Bond; (2) Total etch + collagen depletion with 10% NaOCl + Single Bond and (3) No etch + experimental self-etching adhesive. Composite was applied to the treated surfaces using a 3 x 5 mm cylindrical Teflon matrix and was light-cured. Each group was further stratified in five subgroups according to storage time in water at 37 degrees C: 1 day, 7 days, 30 days, 6 months and 12 months. Shear bond strengths (SBS) were determined and expressed in MPa. Data was analyzed for statistical significance with two-way ANOVA and Tukey's test (p=0.05). No interaction was observed between surface treatment and storage time. Storage time did not significantly affect bond strengths. Statistically significant differences were observed among the different surface treatments. Single Bond applied after total-etch presented higher mean SBS when compared to the other surface treatment methods. Collagen removal negatively influenced SBS, and the experimental self-etching adhesive presented intermediate values.

This study investigated the effect of topical antibiotic treatment on pulp revascularization in replanted teeth. Thirty-four immature teeth were selected from three young dogs. Baseline radiographs and laser Doppler flowmetry (LDF) readings were obtained. Specimens were randomly divided into four groups: Thirty-eight teeth were extracted, kept dry for 5 min, and either (Group 1) covered with minocycline mixture (G1, n = 11), (Group 2) soaked in doxycycline (G2, n = 11), or (Group 3) soaked in saline (G3-negative control, n = 6), and replanted. Teeth in Group 4 were not extracted (positive control, n = 6). Postoperative radiographs and LDF readings were obtained for 2 months after replantation. After sacrifice, the jaws were collected and processed for light microscopy. Pre- and postreplantation LDF readings and radiographs, and histologic findings were analyzed to assess revascularization. Pulp revascularization occurred in 91% (G1), 73% (G2), and 33% (G3) of the specimens. In conclusion, minocycline facilitates pulp revascularization in replanted immature teeth after replantation.

PURPOSE/OBJECTIVE:This pilot study used a novel study design to evaluate the effect of a 10% carbamide peroxide bleaching gel on the bond strength of a resin-based composite system to dentin. MATERIALS AND METHODS/METHODS:Dentin disks were obtained from human third molars, polished to 600 grit, and mounted on the palatal aspect of a removable orthodontic retainer. Two disks were exposed to a 10% carbamide peroxide bleaching gel for 2 h/d for 21 days, whereas two disks were not treated and served as controls. A retainer was worn by the participant regardless of whether bleaching was used, simulating the action of the saliva/oral fluids on the dentin specimens. After the treatment phase, the dentin disks were retrieved and a resin-based composite system was applied to the specimens following manufacturer's instructions. Composite dentin "sticks" were obtained and tested in microtensile mode. Bond strength values were obtained for treated (n = 20) versus nontreated (n = 26) dentin and were analyzed statistically. RESULTS:Mean bond strengths values (SD) were 29.9 MPa (6.2) and 39.2 MPa (5.8) for treated and nontreated dentin specimens, respectively (p < .001). CONCLUSION/CONCLUSIONS:The results of this study suggest that nightguard (home) bleaching with 10% carbamide peroxide for 2 h/d for 21 days significantly affects resin-dentin bond strengths when dentin is exposed to bleaching material. CLINICAL SIGNIFICANCE The findings of this novel pilot study imply that dentin bonding, such as to exposed root surfaces and cervical areas of the teeth, should not be performed immediately after bleaching with 10% carbamide peroxide.

The restoration of proximoincisal (Class IV) defects with direct resin-based composites requires attention to many technical and artistic details. This article is the first of a series of two articles that aim at presenting clinical strategies for optimal success when direct resin-based composites are used for the restoration of moderate or large proximoincisal defects. Concepts of natural anatomy, color as it relates to dental structures, and composite selection are discussed in this article and are illustrated with a preclinical exercise and two clinical cases in which these concepts are applied.