Comparison of using calcium hydroxide or a dentine primer for reducing dentinal pain following crown preparation: a randomized clinical trial with an observation time up to 30 months.

The purpose of this study was to evaluate effect of a calcium hydroxide suspension [Ca(OH)2] or glutaraldehyde based dentine primer (GDP) to reduce tooth sensitivity after full crown preparation. Thirty-six patients were treated with Ca(OH)(2) on one tooth and with GDP on another. Patients completed a questionnaire regarding sensitivity during crown preparation, when the not-anaesthetized abutments were irritated [cotton pellet (20 degrees C)]. The teeth were tested before (T(0)) and after using the desensitizer (T(1)), again after 7 days (T(2)), 6 months (T(3)) and 30 months (T(4)). The results were registered on a visual analogue scale [0 (no pain)-100 (severe pain)]. The changes of tooth sensitivity between different testing times were analysed. The median and the (interquartile range) for the different time intervals for Ca(OH)(2) were DeltaT(0)-T(1): 5 (6-17), DeltaT(0)-T(2): 17 (14-32), and for GDP, DeltaT(0)-T(1): 9 (7-18) DeltaT(0)-T(2): 18 (16-33), the decreases in sensitivity were lower for DeltaT(0)-T(1) than for DeltaT(0)-T(2) for both desensitizers (P < 0.001). There was no statistical difference (P > 0.05) between the agents (DeltaT(0)-T(1), DeltaT(0)-T(2), DeltaT(3)-T(4)). Both substances might be useful in reducing tooth sensitivity after crown preparation, but no differences in the efficacy were found when comparing the materials.

Long-term resin bond strength to zirconia ceramic.

PURPOSE: The aim of this in vitro study was to evaluate the long-term bond strength of adhesive bonding systems to yttrium-oxide-partially-stabilized zirconia ceramic (YPSZ). MATERIALS AND METHODS: Plexiglas tubes filled with resin composite were bonded to industrially manufactured zirconia ceramic disks (96% ZrO2 stabilized by 4% Y2O3). After air abrading the ceramic and ultrasonic cleansing, groups of 16 samples were bonded in an alignment apparatus using 7 different bonding methods. Subgroups of 8 bonded samples were tested for tensile strength following storage in distilled water at 37 degrees C either for 3 days or 2 years. In addition, the 2-year samples were thermocycled 37,500 times. The statistical analyses were conducted with the Kruskal-Wallis test followed by multiple pair-wise comparison of the groups using the Wilcoxon rank sum test. RESULTS: A moderate to relatively high initial bond strength was achieved by air abrasion alone, the additional use of a silane, or acrylizing the YPSZ surface in combination with a conventional bis-GMA resin composite. However, these methods failed spontaneously over storage time. The use of the bis-GMA resin composite after tribochemical silica coating of YPSZ and the use of a polyacid-modified resin composite after air abrasion of YPSZ resulted in a high initial bond strength which decreased significantly over storage time. A durable resin bond strength to YPSZ was achieved only after air abrasion of YPSZ and using one of two resin composites containing a special phosphate monomer. CONCLUSION: A durable bond strength to YPSZ was achieved only by using resin composites containing a special adhesive monomer.

Bonding to zirconia ceramic: adhesion methods and their durability.

OBJECTIVES: Resin bonding to yttrium-oxide--partially-stabilized zirconia ceramic (YPSZ) cannot be established by standard methods that are utilized for conventional silica-based dental ceramics. It was our hypothesis that adhesive bonding methods suitable for glass-infiltrated alumina ceramic can also be used to bond successfully to YPSZ. To prove this hypothesis, bonding methods suitable for alumina ceramic were used on YPSZ and the tensile bond strength and their durability evaluated in vitro. METHODS: Plexiglass tubes filled with resin composite were bonded to YPSZ discs following various adhesion protocols. Groups of 16 samples were bonded using seven different bonding methods. Subgroups of eight bonded samples were tested for tensile strength following storage in distilled water (37 degrees C) for either 3 or 150 days. In addition, the 150 day samples were thermal cycled 37,500 times as a method to stress the bond interface. The statistical analysis was made with the Kruskal-Wallis test followed by multiple pair-wise comparisons of the groups using the Wilcoxon rank sum test. RESULTS: Sandblasting alone, the additional use of a silane or acrylizing resulted in an initial bond of a conventional BisGMA resin composite to YPSZ which failed spontaneously over storage time. The use of the BisGMA resin composite after tribochemical silica coating of YPSZ and the use of a polyacid-modified resin composite after sandblasting of YPSZ resulted in an initial bond which decreased significantly over storage time (p = 0.05). A durable resin bond to YPSZ was achieved only after sandblasting the ceramic and using one of two resin composites containing a special phosphate monomer. SIGNIFICANCE: A durable bond to YPSZ was achieved only by using resin composites with a special adhesive monomer. Therefore, the hypothesis of the study was partially proved as a durable bond to alumina ceramic is achieved with the same resin composites. However, it was partially disproved as tribochemical silica coating of YPSZ did not result in a durable resin bond as it does on glass-infiltrated alumina ceramic.