In vitro testing of shear bond strength of orthodontic brackets bonded to different novel CAD/CAM ceramics

Background. The present study aimed to evaluate the bond strength of metal bracket (MB) and ceramic bracket (CB) bonded to different CAD/CAM ceramic substrates etched with hydrofluoric acid (HFA) vs. phosphoric acid (PA). Methods. A total of 120 CAD/CAM ceramic blocks in 12 groups were fabricated from three different CAD/CAM ceramic materials: VITABLOCS Mark II, VITAENAMIC, and IPS e.max CAD. Each ceramic material group was divided into two etching groups: one treated with 9.5% HFA and the other treated with 37%. Sixty metal and CBs of the upper right central incisor were bonded to the HFA-treated blocks. Another 60 metal and CBs were bonded to the PA treated blocks. All the bonded specimens were thermocycled before shear bond strength (SBS) testing. Then the bond failure mode was recorded Results. There were no significant differences in SBS values between the three CAD/CAM ceramic materials. The HFA-treated specimens exhibited significantly higher SBS values than the PA-treated specimens. Also, the SBS values of CBs were significantly higher than the metal brackets (MBs). The adhesive remnant index (ARI) score was 4 for most of the groups, indicating that almost no adhesive remained on the porcelain surface. Conclusion. The CAD/CAM ceramic type did not influence SBS; however, HFA exhibited significantly higher SBS compared to PA.