Effect of different white-spot lesion treatment on orthodontic shear strength and enamel morphology: In vitro study

Aim: White-spot lesion treatment is required before fixed appliance insertion as caries prevalence increases during orthodontic treatment. The aim of this study was to analyze the effect of fluoride varnish, casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACPF) varnish, and resin infiltration as white-spot lesion treatments on orthodontic shear strength and enamel morphology. Materials and Methods: This is an observational analysis study with posttest-only control group design and blind total sampling methods. Sixty bovine mandible incisors were cleaned and divided into five groups (n = 12). No treatment was applied on Group 1 (control), whereas the four other groups were immersed in demineralization solution for 96h before being stored in artificial saliva (Group 2), treated with fluoride varnish (Group 3), CPP-ACPF varnish (Group 4), and resin infiltration (Group 5). After bracket bonding with resin-modified glass ionomer on all samples, shear bond strength was evaluated. Adhesive remnant index (ARI) was observed by using a digital photo. Enamel morphology was evaluated using a scanning electron microscopy (SEM) before bracket bonding and after polishing. The Kruskal-Wallis test (P > 0.05) followed by Mann-Whitney U test was carried out (P < 0.05). Results: The shear strength in Groups 2 and 5 was slightly increased as compared with control group (P > 0.05), whereas it was significantly decreased in Groups 3 and 4 (P < 0.05). The ARI score was found to be highest after treatment with resin infiltration. Conclusion: Pretreatment with resin infiltration is recommended to be performed before bracket bonding on white-spot lesion; however, it may need to be reapplied after debonding and polishing to conceal enamel morphology damage formed after polishing.