Residents’ journal review

Accuracy of CBCT reconstructions

Maret D, Molinier F, Braga J, Peters OA, Telmon N, Treil J, et al. Accuracy of 3D reconstructions based on cone beam computed tomography. J Dent Res 2010;89:1465-9

Cone-beam computed tomography (CBCT) is increasingly applied in clinical practice. Thus, its accuracy in constructing the 3-dimensional (3D) image must be assessed. Microcomputed tomography (micro-CT) is the current reference standard in 3D dental research because of its high resolution, but it is currently used only in vitro. The researchers hypothesized that high-resolution CBCT and micro-CT data can produce 3D images with similar accuracy and precision. Their specific aims were to assess CBCT accuracy through comparison with micro-CT and to assess geometric deviations between the 2 methods after 3D reconstruction. The sample consisted of 16 mandibles from 8 deceased boys and 8 deceased girls, whose bodies were donated for science. The mandibles contained a total of 120 developing tooth germs. Each mandible was scanned by the micro-CT and CBCT scanners and subsequently reconstructed without smoothing the resulting images. Wilcoxon tests were performed to compare differences in micro-CT and CBCT volumes for each tooth. Significance was set at P ≤0.05. Micro-CT and CBCT 3D volumes were strongly correlated (R 2 = 0.999). CBCT slightly, but not significantly, underestimated the volumes. When anterior and posterior teeth were examined separately, there were significant differences between the 2 scans for anterior teeth but not for posterior teeth. Geometric differences between CBCT and micro-CT reconstructions occurred where thinner tooth structure was present, such as at the incisal edge and the cervical portion of the developing enamel cap. These differences can be explained by the different isotropic voxel sizes between the 2 methods (CBCT, 76 μm; micro-CT, 41 μm). The authors concluded that CBCT accuracy and precision were comparable with those of micro-CT, and that CBCT is an acceptable clinical research tool.

Reviewed by Sheldon Bates

Preliminary findings suggest benefits of miniscrew implants for patients with retrognathia

Buschang PH, Carrillo R, Rossouw PE. Orthopedic correction of growing hyperdivergent, retrognathic patients with miniscrew implants. J Oral Maxillofac Surg 2011;69:754-62

Traditional orthodontic treatment goals are to provide a maximally functional, esthetic, and stable occlusal result. However, a successful dental result could be obtained while ignoring orthopedic and soft-tissue disharmonies accompanying a given malocclusion. In orthodontic treatment of high-angle Class II patients, little to nothing is done to improve the retrognathia, convexity, and “long-face” phenotype. The purpose of this study was to determine whether the use of miniscrews could provide a novel, compliance-free way to modify growth and improve facial balance. In 9 consecutively treated growing patients, intrusion of the posterior maxillary teeth was accomplished by using 2 palatal miniscrews and nickel-titanium closing springs connected to a rigid maxillary expander. Additionally, 2 miniscrews were placed mesially to the mandibular first molars and used to intrude or, minimally, to hold the compensatory eruption of the mandibular posterior teeth. In the first 9 finishes of an ongoing 40-patient study, the mean results showed an increased horizontal chin projection of 2.4 mm, an increase in sella-nasion-basion angle of 2.1°, a mandibular plane angle reduction of 3.9°, and a decrease in facial convexity of 3.2°. The authors hypothesized that patients with increased growth potential will respond more favorably to this treatment because simultaneous tooth intrusion will direct growth in a new forward direction compared with a simple hinge-type rotation of the mandible seen in a nongrowing patient. A subjective patient-satisfaction assessment was given before and after treatment, and rapid maxillary expansion, braces, and miniscrews were all found to be less painful and more comfortable than initially expected. This preliminary report is certainly promising, and it will be exciting to see the rest of the subject outcomes compared with the appropriate controls.

Reviewed by Michael Shoff

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Apr 11, 2017 | Posted by in Orthodontics | Comments Off on Residents’ journal review
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