In vitro comparison of shear bond strengths of ceramic orthodontic brackets with ceramic crowns using an aluminium oxide air abrasion etchant.

OBJECTIVE: The aim of this study was to determine if there are differences between the shear bond strengths of 3 types of ceramic brackets when bonded to different ceramic substrates using an aluminium oxide air abrasion etchant protocol. MATERIALS AND METHODS: Substrate groups consisting of thirty-six lithium disilicate (e.max® CAD) samples and thirty-six lithium silicate infused with zirconia (CELTRA® DUO) samples were fabricated to replicate the facial surface of a left maxillary central incisor. The surface of all samples was prepared with an aluminium oxide air abrasion etchant protocol. Each substrate group was split into three test groups (n=12). Each test group was bonded using a different brand of ceramic orthodontic bracket. Shear bond strength (SBS) testing was conducted and the mean SBS values for each group were calculated and recorded in MPa. An Adhesive Resin Index (ARI) score was also assigned to each sample to assess the location of bond failure. RESULTS: Mean SBS of the e.max® CAD groups were significantly less than the CELTRA® DUO groups. Symetri brackets showed significantly higher shear bond strengths to both substrates than both of the other brackets tested. ARI scores of the e.max® CAD groups were significantly less than the CELTRA® DUO groups. CONCLUSION: The Symetri bracket was the only bracket that was effective for both substrates (mean SBS>6mPa). The Etch Master protocol does not appear effective for e.max® CAD.

Porcelain surface conditioning protocols and shear bond strength of orthodontic brackets.

AIM: The objective of the present study was to determine which of six bonding protocols yielded a clinically acceptable shear bond strength (SBS) of metal orthodontic brackets to CAD/CAM lithium disilicate porcelain restorations. A secondary aim was to determine which bonding protocol produced the least surface damage at debond. METHODS: Sixty lithium disilicate samples were fabricated to replicate the facial surface of a mandibular first molar using a CEREC CAD/CAM machine. The samples were split into six test groups, each of which received different mechanical/chemical pretreatment protocols to roughen the porcelain surface prior to bonding a molar orthodontic attachment. Shear bond strength testing was conducted using an Instron machine. The mean, maximum, minimal, and standard deviation SBS values for each sample group including an enamel control were calculated. A t-test was used to evaluate the statistical significance between the groups. RESULTS: No significant differences were found in SBS values, with the exception of surface roughening with a green stone prior to HFA and silane treatment. This protocol yielded slightly higher bond strength which was statistically significant. CONCLUSION: Chemical treatment alone with HFA/silane yielded SBS values within an acceptable clinical range to withstand forces applied by orthodontic treatment and potentially eliminates the need to mechanically roughen the ceramic surface.