Objectives: The purpose of this study was to evaluate the effect of Remaining Tooth Thickness (RTT) on resin composite bond strength to mesial and distal wall when using two-step and one-step self-etching adhesive systems.
Methods: The occlusal enamel was ground to expose a flat superficial dentin surface of human molars. Box-form occlusal cavities, 3mm longx4-5mm wide were prepared to a depth of 2mm below the flat dentin surfaces. The buccal and lingal walls of cavities were removed making flat surfaces(mesial wall and distal wall) for bonding. Each specimen was restored with one of two adhesives: one-step self-etching system, Clearfil Tri-S Bond(TS, Kuraray Noritake Dental); or two-step self-etching system, Clearfil SE Bond(SE, Kuraray Noritake Dental); followed by buildup using Z100 resin composite(3M ESPE). After 600mW/cm
2 for 40s light-curing, teeth were stored in the dark for 24 hours in water. The teeth were sectioned perpendicularly to flat mesial and distal wall dentin obtaining approximately 1 mm
2 beams. The micro-tensile bond strength(µTBS, MPa) was determined. Data (n=8) were analyzed using Bonferroni test.
Results: TS showed significantly lower µTBS to RTT<2mm substrates compared with that of RTT>2mm group(p<0.05). However, there was no significantly different µTBS between RTT<2mm group and RTT>2mm group using SE(p>0.05).
Conclusion: Bonding to wall dentin was affected by remaining tooth thickness when using one-step self-etching system, Clearfil Tri-S Bond. However, for two-step self-etching system, Clearfil SE Bond, bond strength to wall dentin was not affected by the influence of remaining tooth thickness. Supported by Grant #22592115 from JSPS.
Table 1. Mean RTT, and mean tensile bond strength of the bonding system to each wall dentin
(Mean(SD))
|
Clearfil SE Bond
|
Clearfil Tri-S Bond
|
RTT(mm)
|
µTBS(MPa)
|
RTT(mm)
|
µTBS(MPa)
|
RTT<2mm
|
2.0(0.2)a
|
76.2(17.5)A
|
1.9(0.3)a
|
30.9(10.6)a, A
|
RTT>2mm
|
2.8(0.2)a
|
83.5(19.9)A
|
2.7(0.3)a
|
52.6(5.0)a, A
|
Intragroup data designated with same superscript small letters each RTT are significantly different(p<0.05). Intergroup data designated with same superscript capital letters each adhesive system are significantly different(p<0.05).