Microleakage of Panavia bonded cast metal

Abstract

Panavia resin cement has an anaerobic polymerization reaction. When cast restorations are luted using this material oxygen must be excluded at the margins or inadequate polymerization will occur resulting in increased microleakage. This investigation evaluated the ability of different materials to exclude oxygen at the marginal area of castings. Forty extracted maxillary incisors were selected and placed into four equal groups. The labial enamel surface was flatted, taking care not to expose dentine. Wax patterns were made directly on the flattened enamel and cast in a base metal alloy. After divesting and fitting the castings, the enamel was etched with phosphoric acid and rinsed. Panavia was mixed following the man ufacturer directions and used to lute the castings onto the etched enamel surface. The excess cement was removed from the marginal area which was completely cover using one of the following materiaIs : Oxyguard (control group), a light cured unfill resin, vaseline, and a low viscosity impression material. Panavia was aIlowed to set for 7minutes ' and covering material was removed. The specimens were placed in 37°C distilled water for 24 hours. Twocoatings ofnail polish were applied on the specimens except for a 2 mm window around the castings. The specimens were placed into 2%methylene blue dye solution, thermocycled for 1700cycleswith a 30 seconddweIltime between 6-60 "C.The specimens were low speed sectioned using a Buehler sectioriing machine. Dye penetration was measured using a MM22 microscope. The mean dye penetration was calculated and compared using ANOV A. The groups do not show a difference at the 0.05 significance level. Under the conditions of this study, any of the materials used function as an oxygen barrier allowing complete polymerization of Panavia at the margins and prevent microleakage under castings. Key words :microleakage, cast metal, adhesion, Panavia.