Effect of topical fluorides and citric acid on heat-pressed all-ceramic material.

The effects of citric acid and acidulated phosphate fluoride on the surface roughness of autoglazed and overglazed all-ceramic IPS Empress materials were analyzed. Atomic force microscopy was used to measure the roughness. Citric acid solution (2.00%) was applied for 8 hours, simulating 2 years of exposure. Acidulated phosphate fluoride gel (1.23%) was applied for 32 minutes, simulating 2 years of fluoride therapy. Acidulated phosphate fluoride caused a significant roughening effect on both autoglazed and overglazed specimens.

Effects of attachment design on strains around implants supporting overdentures.

The objective of this study was to compare strain magnitudes around implants supporting ball-retained, bar-retained, and distal cantilevered bar-retained mandibular overdentures subjected to vertical and oblique loads. Twelve edentulous mandibular acrylic resin casts with 2 implants in the parasymphyseal region were randomly divided into 3 groups (n = 4). Ball-retained, bar-retained, and distal cantilevered (8 mm) bar-retained overdentures were fabricated. A linear strain gauge was bonded distal to each supporting implant on the surface of the cast. As static loads of 20, 40, and 60 N vertically were applied 20 degrees obliquely and unilaterally to the overdenture, the generation of strains was recorded by a data acquisition system and corresponding software at a sample rate of 1,000 Hz. The absolute strain data of each group were compared within each loading condition by Kruskal-Wallis test followed by post hoc tests (a = .05). Under vertical and oblique loading conditions, strain magnitudes around implants supporting ball-retained overdentures were higher than those induced around bar-retained and distal cantilevered bar-retained overdentures (P <.01). On the contralateral side from load application, strains around implants supporting ball-retained overdentures were lower than those around bar-retained and distal cantilevered bar-retained overdentures (P <.01). Force distribution does not occur for implants supporting ball-retained overdentures, and such implants are subjected to more load than those supporting bar-retained and distal cantilevered bar-retained overdentures.

Microleakage study of 3 porcelain repair materials by autoradiography.

OBJECTIVE: The purpose of this investigation was to test the microleakage of 3 porcelain repair systems intended for intraoral resin-to-porcelain and resin-to-metal bonding by autoradiography. METHOD AND MATERIALS: Sixty alloy and 60 porcelain disks (10-mm diameter and 2-mm thickness) were prepared. Manufacturer's directions were followed for surface treatment of specimens. Each repair material was applied on 20 alloy specimens and 20 porcelain specimens. Specimens were thermocycled by dipping them in water for 1 minute at 4 +/- 2 degrees C and 58 +/- 2 degrees C for 500 cycles. Leakage was demonstrated by the presence of radioactive isotope at the interface between the repair material and the alloy (or porcelain) as registered by autoradiography. Before testing, specimens were stored in distilled water at 37 degrees C for 24 hours and then thermocycled. Mann-Whitney U test was used to identify the differences. RESULTS: For the alloy groups, differences between Newbond/Clearfil Lustre and GoldLink 2/Ultrabond were significant (P <.05). For the ceramic groups, differences between Cerinate Prime/Ultrabond, Clearfil Lustre/Newbond, Cerinate Prime/Ultrabond, and Silibond/Charizma were significant (P <.05). CONCLUSIONS: For the porcelain groups, the amount of microleakage in Ultrabond/Cerinate Prime was significantly higher than the other groups. For the alloy groups, all samples showed leakage.