Bond Strength Survival of a Novel Calcium Phosphate-Enriched Orthodontic Self-Etching System after Various Ageing Protocols: An In Vitro Study

Abstract

Objective. This study aimed to evaluate the orthodontic bond strength and enamel-preserving ability of a hydroxyapatite nanoparticles-containingself-etch system following exposure to various ageing methods. Materials and Methods. Hydroxyapatite nanoparticles (nHAp) were incorporated into an orthodontic self-etch primer (SEP, Transbond™ plus) in three different concentrations (5%, 7%, and 9% wt) and tested versus the plain SEP (control) for shear bond strength (SBS), adhesive remnant index (ARI) scores, and enamel damage in range-finding experiments using premolar teeth. The best-performing formulation was further exposed to the following four artificial ageing methods: initial debonding, 24 h water storage, one-month water storage, and one-month acid challenge. A field-emission scanning electron microscope (FE-SEM) was used to examine the integrity of debonded enamel surfaces and calcium-phosphates (CaPs) reprecipitation. Results. The best-performing formulation (7% nHAp-SEP) resulted in significantly lower SBS ( p < 0.001 ) than the control SEP following the four artificial ageing methods. Nevertheless, it survived the ageing protocols and yielded clinically acceptable SBS with the advantages of leaving minimal adhesive residue, preserving enamel integrity and smoothness, and inducing CaP reprecipitation as confirmed by FE-SEM images. Conclusions. A newly developed SEP produced adequate orthodontic bond strengths and left unblemished debonded enamel surfaces with minimal remnant adhesive and remineralisation potential, thereby suggesting simpler and safer bonding/debonding procedures.

Bioceramic micro-fillers reinforce antibiofilm and remineralization properties of clear aligner attachment materials

“…The significant reduction in bond strength observed after 28 days of storage in a pH 4 demineralization solution for the Filtek SF and Filtek SF + 10% BRT groups aligns with findings from studies that highlight the susceptibility of certain adhesive systems to acidic challenges ( Fan et al, 2022 ; Garma and Ibrahim, 2022 ). In contrast, the 30% BAG and 30% BRT groups exhibited significantly higher shear bond strength than the Filtek SF control under the same acidic conditions, suggesting a potential protective effect conferred by the higher concentration of bioceramic micro-fillers to enhance bond durability in acidic environments.…”