Three-dimensional quantitative assessment of surgical stability and condylar displacement changes after counterclockwise maxillomandibular advancement surgery: Effect of simultaneous articular disc repositioning.

INTRODUCTION: In this study, we quantitatively assessed 3-dimensional condylar displacement during counterclockwise maxillomandibular advancement surgery (CMMA) with or without articular disc repositioning, focusing on surgical stability in the follow-up period. METHODS: The 79 patients treated with CMMA had cone-beam computed tomography scans taken before surgery, immediately after surgery, and, on average, 15 months postsurgery. We divided the 142 condyles into 3 groups: group 1 (n = 105), condyles of patients diagnosed with symptomatic presurgical temporomandibular joint articular disc displacement who had articular disc repositioning concomitantly with CMMA; group 2 (n = 23), condyles of patients with clinical verification of presurgical articular disc displacement who had only CMMA; and group 3 (n = 14), condyles of patients with healthy temporomandibular joints who had CMMA. Presurgical and postsurgical 3-dimensional models were superimposed using voxel-based registration on the cranial base. Three-dimensional cephalometrics and shape correspondence were applied to assess surgical and postsurgical displacement changes. RESULTS: Immediately after surgery, the condyles moved mostly backward and medially and experienced lateral yaw, medial roll, and upward pitch in the 3 groups. Condyles in group 1 showed downward displacement, whereas the condyles moved upward in groups 2 and 3 (P ≤0.001). Although condylar displacement changes occurred in the 3 groups, the overall surgical procedure appeared to be fairly stable, particularly for groups 1 and 3. Group 2 had the greatest amount of relapse (P ≤0.05). CONCLUSIONS: CMMA has been shown to be a stable procedure for patients with healthy temporomandibular joints and for those who had simultaneous articular disc repositioning surgery.

Common 3-dimensional coordinate system for assessment of directional changes.

INTRODUCTION: The aims of this study were to evaluate how head orientation interferes with the amounts of directional change in 3-dimensional (3D) space and to propose a method to obtain a common coordinate system using 3D surface models. METHODS: Three-dimensional volumetric label maps were built for pretreatment (T1) and posttreatment (T2) from cone-beam computed tomography images of 30 growing subjects. Seven landmarks were labeled in all T1 and T2 volumetric label maps. Registrations of T1 and T2 images relative to the cranial base were performed, and 3D surface models were generated. All T1 surface models were moved by orienting the Frankfort horizontal, midsagittal, and transporionic planes to match the axial, sagittal, and coronal planes, respectively, at a common coordinate system in the Slicer software (open-source, version 4.3.1; http://www.slicer.org). The matrix generated for each T1 model was applied to each corresponding registered T2 surface model, obtaining a common head orientation. The 3D differences between the T1 and registered T2 models, and the amounts of directional change in each plane of the 3D space, were quantified for before and after head orientation. Two assessments were performed: (1) at 1 time point (mandibular width and length), and (2) for longitudinal changes (maxillary and mandibular differences). The differences between measurements before and after head orientation were quantified. Statistical analysis was performed by evaluating the means and standard deviations with paired t tests (mandibular width and length) and Wilcoxon tests (longitudinal changes). For 16 subjects, 2 observers working independently performed the head orientations twice with a 1-week interval between them. Intraclass correlation coefficients and the Bland-Altman method tested intraobserver and interobserver agreements of the x, y, and z coordinates for 7 landmarks. RESULTS: The 3D differences were not affected by the head orientation. The amounts of directional change in each plane of 3D space at 1 time point were strongly influenced by head orientation. The longitudinal changes in each plane of 3D space showed differences smaller than 0.5 mm. Excellent intraobserver and interobserver repeatability and reproducibility (>99%) were observed. CONCLUSIONS: The amount of directional change in each plane of 3D space is strongly influenced by head orientation. The proposed method of head orientation to obtain a common 3D coordinate system is reproducible.

Cone beam computed tomography-based models versus multislice spiral computed tomography-based models for assessing condylar morphology.

OBJECTIVE: To quantitatively compare condylar morphology using cone beam computed tomography (CBCT) and multislice spiral computed tomography (MSCT) virtual three-dimensional surface models. STUDY DESIGN: The sample consisted of secondary data analyses of CBCT and MSCT scans obtained for clinical purposes from 74 patients treated with condylar resection and prosthetic joint replacement. Three-dimensional surface models of 146 condyles were constructed from each scan modality. Across-subject models were approximated and voxel-based registration was performed between homologous CBCT and MSCT images, making it possible to create average CBCT- and MSCT-based condylar models. SPHARM-PDM software provided matching points on each corresponding model. ShapeAnalysisMANCOVA software assessed statistically significant differences between observers and imaging modalities. One-sample t-tests evaluated the null hypothesis that the mean differences between each CBCT- and MSCT-based model were not clinically significant (<.5 mm). Tests were conducted at a significance level of P < .05. RESULTS: ShapeAnalysisMANCOVA showed no statistically significant difference between the average CBCT- and MSCT-based models (P > .68). During pairwise comparison, the mean difference observed was .406 mm (SD, .173). One sample t-test showed that mean differences between each set of paired CBCT- and MSCT-based models were not clinically significant (P = .411). CONCLUSION: Three-dimensional surface models constructed from CBCT images are comparable to those derived from MSCT scans and may be considered reliable tools for assessing condylar morphology.

Photographic assessment of hyperdivergent skeletal Class II patients / Avaliação fotográfica de pacientes padrão esquelético classe II hiperdivergentes

Desordens temporomandibulares, distúrbios do sono por obstrução das vias aéreas e alterações na postura crânio cervical constituem alguns dos problemas que têm sido relacionados com o paciente padrão esquelético classe II hiperdivergente. Embora as telerradiografias laterais representem o padrão ouro para o diagnóstico da morfologia cranio facial na prática clínica, este exame pode não ser viável para aplicação em estudos epidemiológicos de larga escala. Objetivo: O objetivo deste estudo foi testar a validade de um novo método fotográfico no diagnóstico de pacientes classe II hiperdivergentes para fins de investigação epidemiológica. Material e Métodos: Telerradiografias laterais e fotografias de perfil foram obtidas a partir de 123 indivíduos distribuídos em dois grupos: 51 pacientes compuseram o grupo de pacientes classe II hiperdivergente, enquanto que os outros 72 pacientes formaram um segundo grupo. A análise discriminante descreveu um modelo matemático para melhor diagnosticar pacientes padrão esquelético classe II hiperdivergente através de fotografias. Resultados: Uma função canônica discriminante composta por duas variáveis fotográficas classificou corretamente 85% dos pacientes classe II hiperdivergentes durante a validação interna (p < 0,001). O método mostrou 83% de sensibilidade e 73% de especificidade no processo de validação externa. Conclusão: O método fotográfico pode ser considerado como uma alternativa viável e prática para diagnosticar o paciente classe II hiperdivergente, particularmente se existir a necessidade de um método não invasivo e de baixo custo.

Temporomandibular disorders, sleep disturbances by airway obstruction and craniocervical posture changes constitute some of the problems that have been related to hyperdivergent skeletal Class II patients. Although cephalometric radiographs represent the gold standard for diagnosing craniofacial morphology in clinical practice, it might not be feasible for large-scale epidemiological research. Objectives: The aim of this study was to test the validity of a new photographic method in diagnosing hyperdivergent skeletal Class II patients for epidemiological research purposes. Material and Methods: Lateral cephalograms and profile photographs were obtained from 123 subjects assigned into two groups. 51 patients comprised the hyperdivergent skeletal Class II group and the other 72 composed a second group. Discriminant analysis described a mathematical model to better diagnose hyperdivergent skeletal Class II patients through photographs. Results: A canonical discriminant function composed of two photographic variables correctly classified 85% of the hyperdivergent skeletal Class II patients during internal validation (p < 0.001). The method showed 83% sensitivity and 73% specificity in external validation procedure. Conclusion: The photographic method may be a feasible and practical alternative for diagnosing the hyperdivergent skeletal Class II patient, particularly if there is a need for a low-cost and noninvasive method.