Abstract
To characterize the surface roughness of human dentin prepared with different rotary instruments and its influence on the micro-tensile bond strength (microTBS) of self-etch adhesives.
Dentin surfaces were created from mid-coronal sound dentin in extracted, human third molars. The teeth were ground with high-speed diamond, tungsten carbide finishing, and cross-cut carbide rotary instruments. Morphological changes obtained were investigated with a surface texture analyzer. Two additional specimens from each group were treated and prepared for scanning electron microscopy. Resin composite (Z 100) was bonded to the surfaces using Optibond FL (control), Adper Prompt L-Pop (strong), Clearfil SE Bond (mild), or Clearfil S3 Bond (ultra-mild). Rectangular micro-specimens were prepared using the slow-speed diamond saw and tested in tensile to determine the microTBS. The data were analyzed with one-way analysis of variance and Tukey's HSD test (alpha= 0.05).
Surface preparation resulted in significant differences for surface topography and micro-tensile bond strength (P< 0.001). The cross-cut carbide burs had significantly higher mean roughness readings (SD) for all parameters: Ra [8.6 (1.9) microm], Rq [10.9 (2.2) microm], and Ry [41.1 (2.1) microm], except for the mean Rz [12.1 (3.1) microm] value, which was recorded for diamonds. The other roughness parameters for the diamond rotary instruments were intermediate. Dentin surfaces completed with tungsten carbide finishing burs produced a smoother surface Ra [1.2 (0.5) microm)] Rq ([1.6 (0.6) microm], Ry [6.4 (2.6) microm)] and Rz [1.9 (0.6) microm)]. The etch-and-rinse adhesive (OptiBond FL) yielded high micro-tensile values (58.1-68.3 MPa), irrespective of the rotary instruments used. The micro-tensile bond strength values were comparable for self-etch adhesives (Adper Prompt L-Pop, Clearfil SE Bond, Clearfil S3 Bond) irrespective of the burs used. The microTBS values were significantly higher with tungsten carbide finishing burs and smooth dentin surfaces.