S. HEIDE*, M. KERN and J.R. STRUB (Dept. of Prosthodontics, Albert-Ludwigs University, Freiburg, FRG).
The purpose of this laboratory study was to evaluate the influence of different metal cleaning methods on different resin bonding systems and the durability of the bond to a NiCr alloy. Plexiglass tubes (inner diameter 3.3 mm) filled with resin Clearfil F2 (Kuraray, Japan) were bonded to NiCr discs (Wirobond C, Bego, FRG). After sandblasting the NiCr alloy with 110 µm Al2O3 at 2.5 bars pressure the samples were bonded in an alignment apparatus using the following three bonding systems: (RO) silicoating with the Rocatec-system (Espe, FRG)/Twinlook (Heraeus Kulzer, FRG); (KE) conditioning with Kevloc-system (Heraeus Kulzer, FRG)/Twinlook; (PA) Panavia 21 (Kuraray, Japan). For each bonding system, three metal cleaning methods were used after the last sandblasting step: (B) cleaning the metal surface with a stiff brush; (A) ultrasonic cleaning in alcohol; (N) ultrasonic cleaning in a neutral detergent. For each combination 20 samples were bonded. Subgroups of 10 bonded samples were stored in water (37°C) either for (1) 3 days with no thermal cycles or (2) 150 days with 37,500 thermal cycles from 5°C to 55°C to 5°C (dwell time 30 sec). The tensile bond strength was tested at 2 mm/min using a chain loop attachment. The mean tensile bond strengths (TBS) in MPa were: (RO-B1) 42.7 7.3; (RO-82) 43.1 t 7.7; (RO-A1) 48.1 6.7; (RO-A2) 43.0 7.1; (RO-N1) 34.8 6.0; (RO-N2) 37.1 7.8; (PA-B1) 39.5 7.8; (PA-B2) 36.8 7.3; (PA-A1) 49.2 7.5; (PA-A2) 42.2 8.2; (PA-N1) 48.4 6.8; (PA-N2) 35.0 10.9; (KE-B1) 43.6 6.1; (KE-B2) 5.4 3.7; (KE-A1) 39.9 8.9; (KE-A2) 5.8 1.5; (KE-N1) 28.7 5.5; (KE- N2) 5.5 2.0. There were statistically significant differences (SSD) among groups as revealed by the KRUSKAL-WALLIS-test (p< 0.001). Pairwise comparison of groups using the WILCOXON-test modified by BONFERRONI-HOLM showed that 150 day storage time with thermocycling caused a statistically significant reduction in TBS for the Kevloc-system only (p< 0.01). The cleaning methods had no influence on the durability of the resin bond.