Effectiveness of metal surface treatments in controlling microleakage of the acrylic resin-metal framework interface

Statement of problem. Microleakage at the junction between the metal alloy and acrylic resin in a removable partial denture may result in discoloratio n, fluid percolation, and acrylic resin deterioration. The junction between a metal alloy and acrylic resin is an area of clinical concern. Failure of a removable partial denture may be linked to this interface. Enhancing res istance to microleakage at this interface may improve the long-term union b etween the 2 materials. Purpose. This investigation was designed to determine the effects of variou s metal surface treatment protocols on microleakage and bond strength betwe en the metal alloy and acrylic resin used in the fabrication of a removable partial denture. Material and methods. Ninety-sh nickel-chromium-beryllium alloy specimens w ere randomly divided into 8 groups. After adaptation of baseplate was, each specimen was invested. Subsequent to was removal, each specimen was divide d into a control half and an experimental half. Air abrasion, tinplating/ox idation, and silanation were evaluated individually and in all combinations . Heat-polymerized acrylic resin was processed against all specimens before storage in distilled water at 37 degreesC for 72 hours. Each specimen then was thermocycled in distilled water (3000 cycles) before immersion in sodi um fluorescein dye for 24 hours. Counting grids that exhibited dye penetrat ion under ultraviolet light exposure allowed assessment of microleakage. Results. Air abrasion resulted in a significant decrease in microleakage wh en used individually and in all combinations (P<.05). All experimental comb inations that did not involve air abrasion demonstrated no significant redu ction in measured microleakage between the experimental and control sides. Tukey's pair wise comparison of the difference in the mean number of square s exhibiting microleakage between the control and treated sites for each ex perimental group revealed a significant difference, based on the involve: m ent of air abrasion. Groups involving air abrasion did not differ significa ntly from each other (P<.05). In addition, no significant difference was de tected between groups not involving air abrasion (P<.05). Conclusion. Air abrasion, alone and in combination with tinplating/oxidatio n and with silanation, resulted in a significant reduction in microleakage between the metal alloy and acrylic resin.