Resistance of bonded premolars to four artificial ageing models post enamel conditioning with a novel calcium-phosphate paste

Ali I Ibrahim; Noor R Al-Hasani; Van P Thompson; Sanjukta Deb

doi:10.4317/jced.56764

Resistance of bonded premolars to four artificial ageing models post enamel conditioning with a novel calcium-phosphate paste

J Clin Exp Dent. 2020 Apr 1;12(4):e317-e326. doi: 10.4317/jced.56764. eCollection 2020 Apr.

Authors

Ali I Ibrahim^{1

2}, Noor R Al-Hasani^{3

4}, Van P Thompson¹, Sanjukta Deb¹

Affiliations

¹ Centre for Oral, Clinical and Translational Sciences, Faculty of Dentistry, Oral & Craniofacial Sciences, King's College London, London, UK.
² Department of Orthodontics, College of Dentistry, University of Baghdad, Baghdad, Iraq.
³ Institute of Pharmaceutical Science, King's College London, London, UK.
⁴ Department of Basic Sciences, College of Dentistry, University of Baghdad, Baghdad, Iraq.

Abstract

Background: This in vitro study compares a novel calcium-phosphate etchant paste to conventional 37% phosphoric acid gel for bonding metal and ceramic brackets by evaluating the shear bond strength, remnant adhesive and enamel damage following water storage, acid challenge and fatigue loading.

Material and methods: Metal and ceramic brackets were bonded to 240 extracted human premolars using two enamel conditioning protocols: conventional 37% phosphoric acid (PA) gel (control), and an acidic calcium-phosphate (CaP) paste. The CaP paste was prepared from β-tricalcium phosphate and monocalcium phosphate monohydrate powders mixed with 37% phosphoric acid solution, and the resulting phase was confirmed using FTIR. The bonded premolars were exposed to four artificial ageing models to examine the shear bond strength (SBS), adhesive remnant index (ARI score), with stereomicroscopic evaluation of enamel damage.

Results: Metal and ceramic control subgroups yielded significantly higher (p < 0.05) SBS (17.1-31.8 MPa) than the CaP subgroups (11.4-23.8 MPa) post all artificial ageing protocols, coupled with higher ARI scores and evidence of enamel damage. In contrast, the CaP subgroups survived all artificial ageing tests by maintaining adequate SBS for clinical performance, with the advantages of leaving unblemished enamel surface and bracket failures at the enamel-adhesive interface.

Conclusions: Enamel conditioning with acidic CaP pastes attained adequate bond strengths with no or minimal adhesive residue and enamel damage, suggesting a suitable alternative to the conventional PA gel for orthodontic bonding. Key words:Enamel etching, calcium phosphate, bracket bond strength, adhesive residue, enamel damage.