Immediate restoration after mineral trioxide aggregate pulpotomy with amalgam condensation: an in vitro study.

Mineral trioxide aggregate (MTA) pulpotomy may be an alternative to root canal therapy, with reported success rates as high as 85%. However, little technique-specific information has been reported regarding MTA placement in 1 visit. The purpose of this study was to evaluate different placement methods for MTA and resin-modified glass ionomer (RMGI) cement before immediate restoration with amalgam. Forty pulpotomized extracted third molars were randomly divided into 4 groups, and moist cotton was used to simulate pulp tissue in all teeth. In group 1, cotton was placed over the entire pulp chamber floor and in each canal orifice, and MTA was placed over the cotton. The procedure for group 2 was the same as that for group 1 except that a layer of RMGI was placed over the MTA. In group 3, cotton was placed in the canal orifices only, a layer of MTA was placed only over the cotton in the orifices, and RMGI was layered over the MTA and pulp chamber floor. The procedure for group 4 was the same as that for group 3 except that RMGI was placed over the MTA but not on the pulpal floor. Each of these procedures was followed by amalgam condensation. After a 7-day setting period, restored teeth were sectioned mesiodistally, photographed, measured, and evaluated for disturbance of the MTA-restoration junction. The study findings showed that the MTA layer was disturbed in 40% of the specimens in group 1, whereas 10%-20% of specimens in groups 2 through 4 demonstrated disturbed MTA. Analysis with a Pearson chi-square test indicated that the difference between group 1 and groups 2 through 4 was statistically significant (P < 0.05), but there was no significant difference (P > 0.05) between groups 2, 3, and 4. Group 3, in which MTA was placed over each canal orifice and RMGI was placed over the entire pulpal floor, performed best--only 10% of specimens exhibited deformed MTA. The findings suggest that RMGI may protect initially placed MTA during amalgam condensation.

Effects of Alpha-tocopherol Antioxidant on Dentin-composite Microtensile Bond Strength after Sodium Perborate Bleaching.

It has been reported that bond strength can be reversed to prebleached levels with the application of 10% alpha-tocopherol in a 2-hour time frame or by delaying bonding for 2 weeks. This study evaluated the effectiveness of a 5-minute application of 20% alpha-tocopherol to reverse the deleterious effects of nonvital bleaching on consequent bond strength. Thirty third molars were assigned to the following 3 groups: unbleached, bleached, and bleached followed by treatment with alpha-tocopherol. The bleached groups were exposed to sodium perborate (2 g/mL) for 7 days. The postbleach treatment group was subsequently treated with 20% alpha-tocopherol for 5 minutes, and then all groups were restored with composite resin. After 24 hours of storage at 37°C and 100% humidity, restored tooth specimens were sectioned into 1-mm2 dentin-composite beams. Six beams from each tooth were subjected to microtensile bond strength testing. Representative beams were further evaluated with Raman microspectroscopy and scanning electron microscopy. The mean bond strength values (MPa) for each group were as follows: unbleached control group = 26.2, bleached control group = 20.3, and post-bleach treatment group = 18.5. A 1-factor analysis of variance and Tukey post hoc test (α = 0.05) indicated that bleaching had a detrimental effect on bond strength and that short-term alpha-tocopherol treatments did not improve postbleach bond strength. Raman microspectroscopy and scanning electron microscopy revealed no noted improvement for the post-bleach treatment group.The application of 20% alpha-tocopherol in a clinically relevant time frame was not effective in counteracting the deleterious effect of bleaching on bond strength. Bonding procedures should be delayed after tooth bleaching.

Comparison of Accuracy of Calibration Ring Placement on 4 Different Endodontic Files.

INTRODUCTION: The purpose of the current study was to evaluate the accuracy and consistency of the placement of calibration rings on 4 file types: K3 (SybronEndo, Orange, CA), Vortex Blue (Tulsa Dentsply, Tulsa, OK), Kontrol Flex (Brasseler USA, Savannah, GA), and Lexicon (Tulsa Dentsply, Tulsa, OK). METHODS: Forty endodontic files, 10 of each type, were measured using a measuring microscope (Model W122; Gaertner Scientific Corp, Skokie, IL). Measurements were made from the file tip to the leading edge of 2 calibration rings and to the handle of each file. Each file measurement was performed 3 times by the same operator to ensure internal validity, and the 3 measurements were used to generate a mean for each file measurement. RESULTS: Based on a 1-factor analysis of variance and Tukey post hoc test (α = 0.05), K3 files displayed significantly greater accuracy and consistency in calibration ring and handle position. In contrast, Vortex Blue files were the least accurate, whereas both Kontrol Flex and Lexicon files were marked with similar precision. CONCLUSIONS: Calibration rings have been used by some operators to measure files during canal instrumentation. This study showed there was variation in placement of calibration rings and handles. Reliance on calibration rings and file handles as the sole means of measuring endodontic files may lead to inaccuracy in canal instrumentation.

Effect of 35% sodium ascorbate treatment on microtensile bond strength after nonvital bleaching.

UNLABELLED: According to previous reports, adverse effects of tooth bleaching on bond strength can be reversed by delaying bonding for 1-3 weeks or by applying 10% sodium ascorbate (SA) for 3 hours or more. This study evaluated the effectiveness of the short-term application of 35% SA to counteract the effects of a 7-day 35% hydrogen peroxide (H2O2) bleaching regimen on bond strength. METHODS: Forty extracted third molars were mounted and sectioned to obtain a flat dentin surface and then randomly assigned into 4 groups: group 1: restored, no bleach; group 2: bleached, bonded immediately; group 3: bleached, treated with two 1- minute 35% SA applications before bonding; and group 4: bleached, treated with two 5-minute 35% SA applications before bonding. For bleach treatment in groups 2-4, flattened dentin surfaces were exposed to H2O2 for 7 days at 37°C. Subsequent to respective treatments, dentin surfaces were built up with composite (TPH3 and Prime &Bond NT, Dentsply Caulk, Milford, DE). After 24 hours of storage (100% humidity, 37°C), the specimens were sectioned into 1-mm(2) dentin-composite beams. Four beams from each tooth (n = 40/group) were subjected to microtensile bond strength testing. RESULTS: Results were as follows: group 1: 18.1 ± 8.1MPa, group 2: 11.3 ± 5.7MPa, group 3: 11.2 ± 5.2MPa, and group 4: 12.6 ± 6.1MPa. A 1-factor analysis of variance and the Tukey post hoc test (α = 0.05) indicated that bleaching had a detrimental effect on bond strength and that short-term SA treatments after bleaching did not significantly improve bond strength. CONCLUSIONS: The application of 35% SA in a clinically relevant timeframe was not effective at reversing bleaching effects on bond strength. Bonding procedures should be delayed following tooth bleaching.