Effect of CPP-ACP and CPP-ACP with Fluoride on the Shear Bond Strength of Orthodontic Brackets Bonded with Two Different Adhesive Systems: An In Vitro Study

Abstract

Introduction: White spot lesions are a frequent problem during fixed orthodontic treatment, mainly because plaque tends to accumulate around brackets and makes oral hygiene difficult. CPP-ACP and CPP-ACP with fluoride (CPP-ACPF) are commonly used to promote enamel remineralization and reduce mineral loss. However, their use before bracket bonding may alter the enamel surface and could influence both bond strength and colour characteristics. Aim: To evaluate the effect of CPP-ACP and CPP-ACPF pre-treatment on the shear bond strength of orthodontic brackets bonded with light-cure and chemical-cure adhesive systems and to compare their colour characteristics. Materials and Methods: Ninety extracted human premolars were randomly divided into three groups of 30 teeth each: CPP-ACP, CPP-ACPF, and control. Each group was further divided into light-cure and chemical-cure subgroups (n = 15). After standardised enamel pre-treatment and bracket bonding, shear bond strength was measured using a universal testing machine at a crosshead speed of 4 mm/min. Colour parameters were recorded using a spectrophotometer. Statistical analysis was performed using one-way ANOVA, Tukey HSD post-hoc test, and independent samples t-test. Results: The control group showed the highest mean shear bond strength with both adhesive systems, followed by CPP-ACPF and CPP-ACP. However, these differences were not statistically significant (p>0.05). Light-cure adhesives showed higher mean bond strength than chemical-cure adhesives, although the difference was also not significant. Colour assessment showed more consistent colour values with light curing, while chemical-cure groups showed greater variation, particularly towards yellow discolouration. Conclusion: CPP-ACP and CPP-ACPF pre-treatment did not significantly affect the shear bond strength of orthodontic brackets. CPP-ACPF showed slightly better mean bond strength than CPP-ACP, while light-cure adhesives showed more favourable and consistent colour characteristics. These findings suggest that both remineralizing agents can be used before orthodontic bonding without significantly compromising bond strength. Further clinical studies are needed to confirm these findings under actual oral conditions.

Keywords: CPP-ACP, CPP-ACPF, shear bond strength, orthodontic brackets, light-cure adhesive, chemical-cure adhesive, colour characteristics