Comparing the curvature of orthodontic brackets to the buccal lnclination of the second maxillary premolar
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Background: The relationship between the curvature of the tooth and the curvature on the corresponding bracket is of vital importance. The closer the curvature of the base to that of the tooth, the closer adaptation it will assume. It will consequently have better adhesion, retention and distribute the forces on the tooth more efficiently in all dimensions. However, there is a lack of literature relating the buccal curvature of the tooth to the curvature of the corresponding orthodontic bracket. This dissertation investigated this relationship with the help of a novel methodology using Micro- Computed Tomography (Micro-CT). Aim: The aim of the study was to compare the buccal curvatures of the maxillary second premolars with the curvatures of three orthodontic bracket brands using a Micro-CT scanner. Methodology: The study sample included 33 randomly selected maxillary second premolars from archived orthodontic diagnostic models and corresponding orthodontic brackets from three manufacturers: Bioquick (Forestadent), Innovation (GAC) and Victory Series (3M Unitek). The sample was scanned using a Nikon Metrology XTH 225 ST X-ray micro-computer tomography scanner (Yokohama, Japan) at 100kV with a beam current of 200μA with an exposure of 1fps. The images were analysed on Volume graphics VG Studio max 3.2.5. The curvatures of the brackets at the mesial and gingival margin were isolated and the central angle of these curvatures were recorded in degrees. The corresponding curvature angles on the teeth were also recorded of each bracket. The angles of the brackets and the angles on the teeth were analysed to determine which bracket had the lowest angular difference. The angular differences were compared using a two-way ANOVA and a Bonferroni Pairwise Comparison. Results: The results of the study showed there to be no standardisation between angulations of the 3 bracket brands. It also confirmed the results in the literature which states the existence of a great variation in curvature between maxillary second premolars. A statistically significant interaction was found between the angles of the 3 brackets and the angles on the teeth p < 0.0001. The lowest angular difference for the joint 3 and 4 mm prescriptions at the mesial margin of the brackets was that of Victory Series -1.623 (±5.920) and Bioquick had the lowest angular difference for the joint prescriptions at the gingival margin 5.836 (±13.580). The difference at the mesial margin between the Victory series and Innovation was -4.494 (SE±1.681); p = 1 and between Victory series and Bioquick was -5.145 (SE±1.681); p = 1. Both were statistically insignificant. The difference between Bioquick and Innovation at the gingival bracket margin was 0.811(SE±1.681); p = 0, the difference between Bioquick and Victory series was 11.908 (SE±1.681); p = 0, both were statistically significant. Conclusion: The results indicated the best performing bracket at the mesial margin to be that of Victory series. This result was followed by Innovation and Bioquick who were closely matched with no significant difference. The best performing bracket at the gingival margin was Bioquick followed by Victory series and Innovation. The curvature of Innovation greatly underestimated the tooth curvature. The best overall angular difference was that of Victory series.