Effect of different enamel preconditioning protocols on the adhesion of ceramic brackets

This study aimed to compare the adhesion of clarity advanced ceramic brackets bonded with APC Flash Free (APC FF) and Transbond XT (TXT) using different enamel conditioning protocols. Brackets were bonded to extracted bovine incisors, which were divided into 6 groups: (1) Transbond Plus Self Etching Primer (TSEP)/APC FF, (2) Etching/TSEP/APC FF, (3) Polishing/TSEP/APC FF, (4) TSEP/TXT, (5) Etching/TSEP/TXT and 6)Polishing/TSEP/TXT. Shear bond strength was measured using a universal testing machine. After debonding, each tooth was assigned an Adhesive Remnant Index score. The enamel was observed using a scanning electron microscope (SEM). The penetrability of TSEP and composites was determined using confocal microscopy. The bond strength of Etching/TSEP/TXT and Polishing/TSEP/TXT groups was significantly higher than that of the remaining groups, with Etching/TSEP/TXT being significantly higher than Polishing/TSEP/TXT (p < 0.05). With APC FF, there was a tendency for an increase in residual adhesive when etching and with TXT when polishing. SEM showed that etching produced the most porous enamel surface. For both APC FF and TXT bonded brackets, TSEP penetration was similar and significantly higher after etching (p = 0.000). APC FF and TXT had similar and significantly higher penetration in the etched groups (p = 0.000). Ceramic brackets bonded with TXT pre-etching the enamel before applying TSEP showed the most favourable adhesive characteristics.