EFFECT OF COMPOSITE BASING ON THE RESISTANCE TO BULK FRACTURE OF INDUSTRIAL PORCELAIN INLAYS

Objectives. Bases are used in restorative dentistry for several reason s (i.e. isolation, elimination of undercuts, etc). Glass ionomers are the standard materials used as bases for porcelain inlays, despite the disadvantages of their mechanical properties. An alternative basing m aterial is composite: a generous layer of posterior composite is cured and shaped in the cavity before an impression is taken. The composite basing technique has several clinical advantages. The aim of this stu dy was to investigate the effect of the thickness of a composite base on the bulk fracture resistance of industrial porcelain, and to descri be the procedure. Methods. Fifteen porcelain (P) and 15 composite (C) bars, 1-, 2-, and 3-mm thick were joined to form 15 CIP bars, all 4-mm thick. Three groups were created: C 1 mm/P 3 mm (group 1), C 2 mm/P 2 mm (group 2), and C 3 mm/P 1 mm (group 3). The pairs were joined usin g Twinlook cement, subjected to a three-point bending test and loaded to fracture. The beam theory was used to support and explain the resul ts. Results: The fracture load means were: group 1, 197.7+/-18.7 N; gr oup 2, 234.3+/-63.3 N, group 3, 336.3 +/- 31.3 N. Group 3 was signific antly stronger than group 1 (P=0.01) and group 2 (P=0.03). Groups 1 an d 2 were not statistically different. Conclusion: Composite basing is a tissue conserving method which may significantly increase the resist ance to bulk fracture of adhesive porcelain inlays. (C) 1998 Elsevier Science Ltd. All rights reserved.