2006 Volume 49 Issue 4 Pages 510-515
New approaches to bonding restorative materials to tooth substrates without phosphoric-acid etching, such as single-step self-etch systems, have recently been introduced. Oral environmental conditions may also influence the bond strength of the single-ap-plication bonding systems, but little information on this is available. The purpose of this study was to investigate the influence of relative humidity on the bond strength produced by these simplified bonding systems. Bonding systems employed in this study were G-Bond (GC), i Bond (Heraeus Kulzer), One-up Bond F Plus (Tokuyama Dental), Fluoro Bond Shake One (Shofu), and Clearfil tri-S Bond (Kuraray Medical). Mandibular incisors were extracted from 2-3 year-old cattle and the dentin surfaces were wet ground with #600 SiC paper. The teeth were transferred to a controlled temperature and humidity chamber and left for 5 min to bring them to the test environmental conditions. Specimens were prepared in 3 different environmental conditions: A) 25±0.5℃, 50±5% RH, B) 25±0.5℃, 80±5% RH and C) 25±0.5℃, 95±5% RH. The resin paster of each bonding system were condensed into a Duracon® mold (φ4×2mm) and then irradiated. The finished specimens were transferred to distilled water at 37℃ for 24h from the start of light exposure. Ten specimens per group were tested with an Instron testing machine (Type 4204, Instron) in a shear mode at a crosshead speed of 1.0 mm/min. The results were as follows: 1. The dentin bond strengths of the single-step self-etch systems decreased with increase of RH, and significant decreases in bond strengths were observed except for G-Bond and One-up Bond F Plus. 2. According to the fracture mode after the test, adhesive failure tended to increase with increase of RH.
