Comparative Mechanical and Morphological Properties of Bio-Ceramics Coated Orthodontic Brackets/Enamel

Objectives: The aim is to coat orthodontic brackets with two different bioactive materials and to compare the mechanical and morphological properties of coated brackets and tooth surfaces.
Methods: A total of 120 stainless-steel brackets was divided equally into three groups i.e., control group: uncoated brackets and experimental groups: underwent application of a thin coat of nano-hydroxyapatite (n-HA) and nano-bioactive glass (n-BG) using spin coater machine. The brackets were bonded on enamel surface of extracted human premolars. The samples were underwent remineralization/demineralization cycles for 30 days with periodic interval of days 1, 7, 14, and 30. At each time interval, the bond strength of brackets were assessed using mechanical loading. Optical microscope and Scanning electron microscope (SEM) were used for surface evaluation at the baseline and after remineralizationldemineralization cycles for each group. Adhesive remanent index (ARI) values were obtained and quantified. For statistical analysis one-way ANOVA using Tukey's test was used to compare the differences among the groups.
Results: A uniform distribution of coating occurred on the surfaces of brackets. The shear bond strength showed no significant differences in any of the tested groups (control, n-HA, and n-BG) at days 1, 7, and 14. However, control and n-BG showed significant difference than n-HA at day 30. At days 7, 14, and 30 n-HA group showed highest shear bond strength values among the groups. For ARI, most of the samples have a score 1 (1 = Less than 50% of the adhesive left on enamel) with an adhesive nature of failure at enamel-brackets interface. Optical microscope and SEM images confirmed the presence of coated particles on brackets and remnants of adhesives after shear bond strength.
Conclusions: This study confirmed that the n-HA and n-BG coated brackets have high potential for application in orthodontic regrading the structural and mechanical properties.