Clinical evaluation and microstructural analysis of a direct placement gallium restorative alloy

Objectives: The objective of this study was to assess the clinical performa nce of a direct placement gallium alloy sealed with an established dentine adhesive system. In addition, microanalysis of a few gallium restorations t hat failed in clinical service was performed. Clinical factors such as pulp al sensitivity, fracture of the restoration and of the tooth, marginal dete rioration, and tarnish were assessed. Methods: Sixty-ive restorations of Galley and 62 of Tytin (49 and 51 Class II restorations, respectively) were placed according to a predetermined sch eme for randomisation in 37 patients by two operators using rubber dam isol ation. For the Galley restorations, the enamel and dentine were etched, and then sealed with PAAMA 2 dentine adhesive according to the manufacturer's instructions. After carving, PAAMA 2 was applied to the Galley and light-cu red. Cavity preparations for Tytin received no adhesive sealer. All restora tions were polished at least 24 h post-operatively. Microstructural analysi s of retrieved fragments of failed restorations was conducted using electro n probe microanalysis. Results: At 1 year, only one Tytin restoration was found to have failed due to an isthmus fracture. The remaining restorations of Tytin were intact wi th no reported sensitivity. Of the 65 Galley restorations placed, 28 had to be removed, including restorations in teeth, which were symptomatic, non-v ital and/or fractured, and teeth with fractured restorations. Tarnish was p resent on many of the Galley restorations. Retrieved fragments of failed Ga lley restorations exhibited a dark surface at the pulpal wall interface and small cracks were observed in that surface. Internal cracks and extensive corrosion was observed using the microprobe. Gallium oxides and chlorides w ere identified as the predominant corrosion products. Conclusions: The gallium alloy, Galley, sealed with PAAMA 2 dentine adhesiv e system demonstrated a high clinical failure rate. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.