Evaluation of shear bond strength of failed ceramic brackets which are rebonded with silica coating technique

The aim of this study is to evaluate rebonding shear bond strength of different mechanically retantive ceramic brackets and to determine the most reliable way of rebonding with different base treatment techniques.In this study, a kind of singlecristal ceramic bracket (60 pieces of Inspire Ice) and two kinds of policristal ceramic brackets (60 pieces of Clarity, 60 pieces of Mystique), as a total 180 pieces of upper premolar brackets were used. All type of brackets divided into 4 subgroups including 15 brackets in each. Fifteen brackets from each kind of bracket were kept as a control group and nothing was done as a base treatment. Remaining 45 brackets which were previously bonded and then debonded, from each bracket group were divided into 3 groups for different base treatments. Sandblasting, sandblasting+silane and silica coating methods were applied to the groups respectively. New brackets and treated brackets were bonded with a light-cured adhesive. All teeth were stored in distilled water for 24 hours in 37°C and then thermocycled for 1000 times between 5°C-55°C. The shear bond test was performed with a universal testing device. Failure types were classified according to ARI scores. SEM examination was held on representative bracket bases from all groups.While the lowest bond strengths were achieved in sandblasting group with singlecristal brackets, bonding couln?t achieved with policristal brackets. The highest bond strengths were achieved in silica coating group for all types of brackets. Bond strength of sandblasting+silane group was as high as new brackets. According to ARI scores failure side was between bracket-adhesive interface in new brackets but it was shifted to the enamel-adhesive interface in sandblasting+silane and slicacoating groups. Enamel fracture was seen in silica coating groups.Its attained that Sanblasting+silane and silica coating are appropriate techniques in application of rebonding ceramic brackets but nevertheless enamel damage risk shouldn?t be ignored.