In vitro assessment of bracket adhesion post enamel conditioning with a novel etchant paste

Abstract

Background: 37% phosphoric acid (PA) is the traditional enamel etching technique prior to bracket ‎adhesion, yet it has been implicated in numerous enamel injuries. The purpose of the current study was to create a calcium phosphate (CaP) etching paste in a ‎‎simplified capsule ‎formula that can underpin clinically ‎adequate bracket bond strength ‎without jeopardizing the ‎integrity of enamel upon ‎the debracketing procedure. Materials and Methods: micro-sized hydroxyapatite (HA) powder was mixed with 40% PA solution to prepare ‎experimental acidic CaP paste. Sixty human premolars were ‎assigned into two groups of 30 each. ‎Enamel conditioning was accomplished using 37% PA-gel‎ for control group and CaP paste for experimental group. Each group was further divided into two subgroups regarding the water storage (WS) period (24 h and 30 days). Shear bond strength (SBS) test conducted with examination of debonded surfaces for adhesive remnants and enamel damage using a digital microscope. Results: CaP paste produced significantly lower SBS values than PA (p < 0.01), yet sufficient for clinical use. PA etching caused often cracked enamel surfaces with excessive ‎retention of adhesive remnants (mainly ARI scores 2 and 3). Contrarily, enamel treated with the experimental CaP paste exhibited smooth, ‎unblemished surfaces mostly clean of adhesives residues (scores 0 and 1). Conclusion: a newly developed CaP paste in a capsule formula fosters ‎clinically adequate bracket ‎adhesion with a sustained bonding performance, allows a harmless bracket removal with ‎minimal or no adhesive residues on debonded surfaces; thus, it can be introduced as a suitable ‎alternative to PA‎.