Pii: S0109-5641(00)00077-4

Objectives: To ®nd a predictive formula of stress, considering the surfaces (free, adhered) involved, the volume and characteristics of material and the deformation of the measuring system. Materials and methods: 231 samples of ®ve chemically cured restoratives (Silar (SIL, 23), Clear®l F2 (CLE, 39), P10 (P10, 33), Concise (CON, 30), Isopast (ISO, 28)) and four luting (3M Experimental 241 (EXM, 20), Variolink II (VAR, 13), Vitremer LC (VTM, 20) and Dyract Cem (DYR, 25)) materials were allowed to polymerize until they reached a maximum tension (Tmax, 25 min) between six pairs (B 5.81, 8.5, 11.26, 12.42, 17.02, 23.14 mm) of polished metallic discs (range of distances: 0.02±5.9 mm) mounted in a tension machine. The deformation of the measuring system was measured for the recorded forces. Results: A descriptive non-linear formula Tmax ˆ KVolFSASDef was found that individualizes the material's characteristics (K) that considers volume (Vol), free (FS) and adhered (AS) surfaces and deformation (Def) of the system for each force. This formula renders good correlation (material K (r coef®cient)): SIL 0.9998 (0.995), CLE 1.0062 (0.989), P10 1.0224 (0.990), CON 0.9908 (0.992), ISO 0.9648 (0.974), EXM 1.0083 (0.991), VAR 0.9777 (0.996), VTM 0.9925 (0.993), DYR 0.9971 (0.997) between actual Tmax and calculated Tension. There are statistically signi®cant differences …p ˆ 0:002† between K values of both (restorative and luting) groups. Signi®cance: Predictive parameters have in ̄uence in a different way to what is actually considered, if the system is allowed to have deformation, as occurs naturally and volume and material's characteristics are considered. q 2001 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.