Microtensile bond strength of clearfil SE bond to caries-affected dentin and normal dentin

Bonding systems have been traditionally used on normal dentin, even though caries-affected and sclerotic dentin are often the clinically relevant bonding substrates. A self-etching primer adhesive system (Clearfil SE Bond) was evaluated for its ability to bond to caries-affected and normal dentin. In this experimental study, twelve extracted human primary molars with occlusal caries were selected. The enamel and superficial dentin were ground with a diamond disk and stained with a caries detector solution (propylen glycol and 1% acid red). The red-stained soft dentin which was classified as infected dentin was excavated and the affected dentin and surrounding normal dentin were polished with a 600 grit silicon carbide paper under running water to achieve a flat surface. The entire flat surface was bonded with Clearfil SE Bond (Kuraray) according to the manufacturer’s instructions and covered with composite resin Clearfil AP-X (Kuraray) to form a composite crown, approximately 4.5 mm high. The teeth were stored in distilled water at room temprature for 24 hours and were then sectioned with a diamond saw under running water in both X and Y directions, perpendicular to the bonded surface with dimensions of approximately 0.8-1 mm, so that the bonded areas of the affected or normal dentin were isolated. The obtained rods were divided into two groups: Affected and sound dentin. After measuring the cross-sectional areas at the interface, the specimens were mounted in a microtensile tester machine and pulled under tension to failure. The mode of failure was evaluated using a streomicroscope and the data were analyzed by t-test. Statistical analysis indicated that the microtensile bond strength in affected dentin (21.53±6.52 MPa) was significantly lower (p<0.05) than normal dentin (26.98±7.31 MPa). The studied self-etch system, attained lower microtensile bond strength in affected dentin as compared to normal dentin.