A Comparative Evaluation of Enamel Surface Roughness of Two Different Bonding Adhesives After Debonding With Atomic Force Microscopy

Abstract

Introduction The debonding procedures should restore the enamel surface to its pre-treatment state as much as possible after removing orthodontic attachments and all remaining adhesive remnants from the surface of the tooth. The orthodontic attachments are bonded commonly by a light-cured composite system. Light-cured glass ionomer cement has been developed as an alternative to the composite as a bonding agent for orthodontic brackets. There are different methods for cleaning the residual adhesive after the removal of orthodontic attachments. The study aims to evaluate and compare the enamel surface roughness of teeth between two different adhesive systems - light cure composite and glass ionomer cement adhesives - after debonding followed by the removal of resin remnants with a tungsten carbide (TC) bur. A null hypothesis is proposed that there exists no difference in the enamel surface roughness between the two adhesive systems. Materials and methods The test sample of 40 freshly extracted human premolar teeth (n = 40) for orthodontic purposes was taken up for this in vitro study based on the inclusion and exclusion criteria. The sample was randomly assigned into two equal groups, with metal brackets bonded in Group-I (n = 20) by light cure adhesive (Trans bond XT, 3M Unitek, Monrovia, CA) and Group-II (n = 20) with light glass ionomer cement (GC Fuji Ortho LC, Tokyo, Japan). All samples were stored in water at room temperature for 24 h and brackets were debonded with a debonding plier. The removal of cement adhesive remnants was performed with a TC bur with a low-speed handpiece. The three surface roughness parameters, average roughness (Ra), root mean square roughness (Rq), and maximum roughness depth (Rmax), were measured at T1 (before bonding) and at T2 (after debonding and finishing) and the values were compared. The mode of bond failure was assessed by a modified adhesive remnant index (ARI) and the time required for the clean-up of adhesive was also noted.  Statistical analysis The continuous quantitative data were statistically analyzed using SPSS Statistics v. 25.0 (IBM Corp., Armonk, NY). Student's independent t-test/independent-samples t-test is an inferential statistical test for analyzing the difference between the two groups. Paired t-test was used for comparison within the group. The ARI between the groups was analyzed by a chi-square test. The probability (p) value for statistical significance was 0.05 or less for the difference between any two groups for all the analytical tests. Results A comparison of enamel surface roughness before bonding and after debonding for both groups revealed that there was a statistically significant difference within each group. The surface roughness values of composite resin - Ra (98.75 ± 0.96), Rq (120.38 ± 1.06), Rmax (650.14 ± 1.12) - and glass ionomer cement group - Ra (98.75 ± 0.96), Rq (62.76 ± 1.32), Rmax (434.36 ± 1.60) - show that there was a statistically significant difference between the groups with p <0.01. Conclusion There was a significant increase in the surface roughness of enamel after debonding of brackets and finishing with a TC bur with both the light cure and the glass ionomer cement adhesive systems. The light cure group showed more enamel surface roughness when compared to the glass ionomer cement group. In this study, the null hypothesis was rejected as there is a significant difference between the groups tested.