Comparison of the Enamel Cracks in Different Mechanical Debonding Methods

Objectives: The purpose of this study was to evaluate and compare enamel cracks after five different mechanical debonding methods.
Methods: 100 healthy extracted premolar teeth were collected and divided into five groups. In each group, enamel cracks were evaluated macroscopically by two orthodontists, and microscopically by stereomicroscope. All teeth were bonded with AO standard brackets by Transbond^TM XT light cure adhesive and then debonded by bracket debonding plier, which was fixed on the UTM machine, through five methods: OG wing (occlusogingival), MD wing (mesiodistal), Oblique, OG base (occlusogingival) and Cusp-base. Adhesive Remnant Index (ARI) was evaluated by an electron microscope and scored according to Artun and Bregland classification. Removal of residual adhesive was done by tungsten carbide bur and then samples were evaluated macroscopically and microscopically for length and number of enamel cracks after mechanical debonding. Statistical analysis was carried out using the SPSS software version 20.0. In this regard, ANOVA analysis was performed, and also Kruskal-Wallis test was used due to non-normal distribution of data.
Results: OG wing method had the highest required stress for debonding the brackets (17.13±8.98 MPa). Except Cusp-base method, others were correlated with increased number of cracks (total mean of crack number change: 0.48±0.850). So, Cusp-base method can be considered as the best method for debonding brackets. The length of the cracks was increased in all groups (total mean: 2.39±3.10 mm), but it wasn’t significantly different between the groups (P. value> 0.05). Oblique method had the least ARI (18.80), beside the highest ARI in MD wing (43.04) and OG base method (43.39).
Conclusions: There was not a significant correlation between ARI and characteristics of cracks. Eventually, the correlation between ARI and increase of enamel cracks with different methods of debonding was not statistically significant. Also, macroscopic and microscopic methods had a moderate relationship in detecting cracks.