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Objective: To establish an objective method for evaluating facial attractiveness from a set of orthodontic photographs. Materials and Methods: One hundred eight malocclusion patients randomly selected from six universities in China were randomly divided into nine groups, with each group containing an equal number of patients with Class I, II, and III malocclusions. Sixty-nine expert Chinese orthodontists ranked photographs of the patients (frontal, lateral, and frontal smiling photos) before and after orthodontic treatment from "most attractive" to "least attractive" in each group. A weighted mean ranking was then calculated for each patient, based on which a three-point scale was created. Procrustes superimposition was conducted on 101 landmarks identified on the photographs. A support vector regression (SVR) function was set up according to the coordinate values of identified landmarks of each photographic set and its corresponding grading. Its predictive ability was tested for each group in turn. Results: The average coincidence rate obtained for comparisons of the subjective ratings with the SVR evaluation was 71.8% according to 18 verification tests. Conclusions: Geometric morphometries combined with SVR may be a prospective method for objective comprehensive evaluation of facial attractiveness in the near future. [ABSTRACT FROM AUTHOR]

Objective: To determine the accuracy of volumetric analysis of teeth in vivo using cone-beam computed tomography (CBCT). Materials and Methods: The physical volume (Vw) of 24 bicuspids extracted for orthodontic purposes (16 were imaged with the I-CAT and 8 with the CB MercuRay) were determined using the water displacement technique. Corresponding pretreatment CBCT image data were uploaded into Amira 4.0 for segmentation and radiographic volume (Va). All measurements were performed twice by two observers. The statistical difference between Vw and Va was assessed using a paired t-test. The intraobserver and interobserver reliability were determined by calculating Pearson correlation coefficients and intraclass correlation coefficients. Results: The overall mean Vw of teeth specimens was 0.553 ± 0.082 cm3, while the overall mean Va was 0.548 ± 0.079 cm3 (0.529 ± 0.078 cm3 for observer 1 and 0.567 ± 0.085 cm3 for observer 2). There were statistically significant differences between Va and Vw (P < .05). Between observer 1 and observer 2, Va measurements were statistically significantly different (P < .05). The interobserver and intraobserver correlation coefficient for Vw was high. Lastly, surface smoothing reduced the volume by 3% to 12%. Conclusions: In vivo determination of tooth volumes from CBCT data is feasible. The measurements slightly deviate from the physical volumes within -4% to 7%. Smoothing operations reduce volume measurements. Currently, no requirements for accuracy of volumetric determinations of tooth volume have been established. [ABSTRACT FROM AUTHOR]

Objective: To study the inherent relationship between registered and estimated natural head position and further explore the nature of natural head position. Materials and Methods: Thirty-one pretreated patients were included in this study. Both registered natural head position (RNHP) and estimated natural head position (ENHP) were obtained. For RNHP, mirror orientation was used to help to adjust the subject's head position. For ENHP, two approved standard photographs were studied by the assessors before estimation. Correlation analysis was used to analyze the relationship between two angles: Rphoto/Rxray and Ephoto/ Eray. Results: A significant correlation was found between RNHP and ENHP, both on the photographs and on the cephalograms. Conclusion: There is a strong correlation between RNHP and ENHP. RNHP is the subjective perception of the subject and gets some objective meaning by mirror orientation. ENHP is the subjective perception of assessors and gets objective meaning by a standardization session in advance. The mirror orientation of RNHP and the advance standard study of ENHP are crucial for validity and accuracy of NHP as an extracranial reference plane. [ABSTRACT FROM AUTHOR]

Objective: To study the craniofacial changes of adolescents followed longitudinally with their heads oriented in natural head position. Materials and Methods: Longitudinal cephalograms of adolescents (n = 28) with normal occlusion, selected from among 900 candidates, were taken at 13 and again at 18 years of age. Modified elaborate mesh diagrams were developed defined by 90 anatomic landmarks and an additional 172 interpolated points for each cephalogram using a preset computer program. Detailed proportional and disproportional craniofacial changes were showed by both statistical and graphical methods. Results: in females, most craniofacial regions exhibited growth that was proportionate to the mesh core rectangle reference on extracranial true vertical. In males, there was an upward, disproportional enhanced shift of the anterior cranial base and a downward enhanced shift of the mandibular symphysis and inferior border of the corpus. Conclusions: This elaborate mesh analysis, based on mesh core rectangle and referenced on estimated natural head position, provides a novel graphical as well as quantitative method of assessing craniofacial growth. From 13 to 18 years of age, two sexes with normal occlusion displayed different growth patterns referenced on estimated natural head position. In females, most craniofacial regions exhibited growth proportional to the mesh core rectangle. In males, there was an upward, enhanced shift of the anterior cranial base and a downward enhanced shift of the mandibular symphysis and inferior border of the corpus. [ABSTRACT FROM AUTHOR]