We want to thank you for your valuable comments on our article (El-Timamy AM, El-Sharaby FA, Eid FH, Mostafa YA. Three-dimensional imaging for indirect-direct bonding. Am J Orthod Dentofacial Orthop 2016;149:928-31).
Interest in cone-beam computed tomography (CBCT) from all fields of dentistry is currently unprecedented, particularly since third-party software applications have expanded the role of imaging from diagnosis to image guidance of operative and surgical procedures. Since its implementation in orthodontics, CBCT imaging has experienced a great enhancement, which up until now did not justify its use as a routine pretreatment diagnostic tool, especially for children. This is mainly due to 2 major flaws: radiation dose and metallic artifacts. Accordingly, we totally agree that using this technique in contemporary CBCT machines would be indefensible. However, the main intent of our article was to introduce a novel technique for bracket positioning that could be adopted if acceptable CBCT exposure parameters can be attained in the future.
Despite the fact that the results were less than optimum, the 3D models for the brackets in our article were obtained through CBCT scanning. The images were satisfactory for the presented technique of bonding. Yet, in a project we are working on now, a more enhanced and reliable 3D bracket model has been obtained using laser scanning technology. As we mentioned in our article, having 3D images of brackets from different manufacturers could facilitate their implementation for virtual bonding with this technique without prior need for their 3D scanning step.
Computer-aided bracket positioning presented in our article requires an accurate 3D virtual model of dental structures and occlusion. Unfortunately, the major obstacle with CBCT imaging is that it cannot provide detailed dental surface morphology and accurate interocclusal relationships, owing to the limited scanning resolution and streak artifacts caused by radiopaque dental restorations. Although it was not mentioned in the published article, this problem was overcome by substituting the dental portion of 3D CBCT images with precise dental images of an orthodontic 3D digital model. Surface superimposition was based on the palatal vault and the medial portions of the palatal rugae by surface-to-surface matching (best-fit method). This method has proved to be simple, reproducible, and reliable. Moreover, the accuracy of the integration of laser-scanned dental models into CBCT images was reported to be higher with a high threshold setting in 0.20 to 0.40-mm voxel sizes.