The Preliminary Study Of Customized Brackets On Lingual Orthodontics

ObjectiveThe aim of this study was to discuss the feasibility of custom lingual brackets and its positioning trays designing and manufacturing based on digital dental model with computer-aided technology. The accuracy and bond strength of the brackets were both discussed.Materials and methodsForty extracted human premolars were collected which had been extracted for orthodontic purposes and were divided randomly into two groups (ten pairs each):shear bond strengths (groupâ… ) and tensile bond strengths (groupâ…¡). For each group, the teeth were distributed to two groups according to pair echelon design method:customized base brackets (group A and C) and non-customized base brackets (group B and D). Founded 3D information of each group via Laserdenta, an optical scanning system, and reconstructed the three-dimension digital models. The customized lingual brackets for group A and C and the non-customized lingual brackets for group B and D were both designed by Pro/ENGINEER. The brackets were made of wax by the rapid prototyping technique and changed into metal by casting, and the slot width were measured using the microscope. The indirect bonding technique was applied after digital brackets positioning in the same software and indirect bonding trays making by computer-aided technique, into which the brackets were positioned. The shear bond strengths in group A,B and the tensile bond strengths in group C,D were measured.Results1 The custom lingual brackets were successfully designed with engineering software based on the three-dimension digital models and manufactured by using numerical-control machines. The customized bases of the lingual brackets were fit for the teeth.2 The lingual brackets can be made of metal from the CAD models by rapid prototyping technology and casting. The accuracy of the custom lingual brackets met the design requirements.3 There were no significant differences statistically in the width of the slots, analyzed by one-sample t test(t=1.475,P>0.05). It is suggested that there were consistency between the metal brackets and the computer established.4 The indirect bonding trays, made by computer-aided and rapid prototyping technology, matched both the metal brackets and the tooth model.5 Design of bracket base structure significantly affects the bond strength. There were statistically significant differences in both shear and tensile bond strength between the two kind of lingual brackets (P<0.05).Conclusions1 It is feasible to design and manufacture custom lingual brackets and position bonding trays with CAD/CAM technology.2 The indirect bonding trays can be made by rapid prototyping technology after bracket positioning with computer-aided.3 In vitro, bond strength in customized lingual brackets are significantly higher than the non-customized one.