Shear bond strength of ceramic brackets with various base designs bonded to aluminous and fluorapatite ceramics

This study was conducted to evaluate the shear bond strength (SBS) of various ceramic bracket base designs bonded to glazed aluminous (Vitadur Alpha) and fluorapatite (IPS e.max Ceram) ceramics, to examine the mode of failure, and to determine the debonding characteristics of the brackets and the ceramic surfaces after bond failure. Forty ceramic discs (15 mm in diameter and 1.5 mm thick) of each ceramic were prepared and divided into four equal groups. Ten pieces of each group of different bracket bases (beads, Inspire Ice; large round pits, Crystalline IV; and irregular base, Clarity) and one group of stainless steel brackets (Optimesh XRT, control) were bonded to glazed ceramics under a 200 g load. All specimens were then subjected to SBS evaluation using a universal testing machine at a crosshead speed of 0.2 mm per minute. The data were analysed using analysis of variance and Tukey's test at a significance level of 0.05. The mode of failure was examined under a stereomicroscope. The results demonstrated that for Vitadur Alpha and IPS e.max Ceram, the highest SBS were found with Inspire Ice (25.1 +/- 2.6 and 24.9 +/- 2.1 MPa) and were significantly different than Crystalline IV (21.6 +/- 1.1 and 20.9 +/- 1.5 MPa), Clarity (19.6 +/- 1.5 and 19.3 +/- 2.3 MPa), and Optimesh XRT (14.9 +/- 1.3 and 15.3 +/- 2.2 MPa; P < 0.05). Inspire Ice and Crystalline IV had 100 per cent adhesive failure while Clarity and Optimesh XRT had combination failure. The various base designs gave different SBS, but the SBS of all base designs could withstand normal orthodontic force.