Crazing of Acrylic Fillings in Relation to Various Inserting, Finishing, and Polishing Techniques

¹ Tokyo Medical and Dental University, Tokyo, Japan

Crazing was investigated as a factor for clinical discoloration of acrylic fillings. A self-curing, acrylic resin was filled in glass-tube cavities by various inserting, finishing, and polishing techniques. Crazed surfaces of the fillings, produced by ethyl alcohol of various concentrations, were stained with iodine-potassium iodide, sectioned, and observed microscopically. The unfinished surfaces of the fillings made by the pressure technique showed severe crazing with alcohol stronger than 40 per cent. The tinfoil cover produced crazing on the specimens made by the brush-on technique, when treated with alcohol stronger than 60 per cent. The depth of the cracks was less than 50 µ. Those surfaces reduced by approximately 50 µ were, however, never crazed with alcohol weaker than 80 per cent, even when the original surfaces were crazed. No significant difference was found between dry and wet finishings. Dry polishing with a rubber cup lubricated with insufficient paste roughened the surface but did not increasing crazing.