Effect of curing strategies on bonding of deep cavity floor

Objectives: Resin composites have recently been widely used with a great variety of cavities. There has been no proven scientific evidence to show the effectiveness of using resin composites on deep cavities. The purpose of this study is to evaluate the micro-tensile bond strength using two kinds of curing light units upon deep cavities.

Methods: Black ABS resin molds, each with a cylindrical cavity, were used for this study. Each cavity was 5mm diameter and 5mm in depth. The cavity floors were made uniform with #600 silicon carbide paper. Each cavity was treated with a bonding system (Clearfil SE Bond, Kuraray) and was restored with a resin composite (Clearfil Photo Core, Kuraray). A conventional QTH light, New Light VLII (GC), and a high intensity GTH light, Cure Master (experimental, Yoshida) were used for curing. Irradiation times on bonding agents were 10 seconds and 20 seconds with each curing light units. Resin composite was filled in the cavity and was cured for 40 seconds with each curing light unit. Specimens were sectioned into thin slabs, trimmed into an hourglass shape with the area of the interface being approximately 1mm², and subjected to micro-tensile testing at a cross-head speed of 1mm/min.

Results: The data were analyzed by one-way ANOVA and Fisher's PLSD test (p<0.05).

Conclusions: The group, using New Light VLII for 10 seconds of irradiation, showed significantly lower micro tensile bond strength than the groups of Cure Master.