Kenji Takada

Objectives: (1) To identify any differences in the accuracy of the prediction of the summed widths of unerupted permanent canines and premolars for males vs females and, if differences are identified, (2) to examine the sex differences in the best combination of independent variables and (3) to evaluate the practical accuracy using our models for both sexes, respectively. Materials and Methods: Records for 200 orthodontic patients (100 males and 100 females) with discernible tooth crowding in the permanent dentition were selected. Mesiodistal tooth crown widths, dental arch widths, and basal arch lengths were measured. Predicted sum widths of permanent canines and premolars in both dental arches were calculated using stepwise regression analysis. Results: Among male subjects, the best combinations of independent variables were the widths of the upper central and lateral incisors (U1, U2) and the first molar (U6) for the maxilla (R² = 0.615) and the mandible, lower central and lateral incisors (L1, L2), and the first molar (L6) (R² = 0.685), whereas in females, the best combinations for prediction were found to be U1, U2, U6, and the maxillary arch width for the maxilla (R² = 0.429) and L1, L2, L6, and the basal arch length for the mandible (R² = 0.426). Correlation coefficients between each independent and dependent variable in the female subject group were found to be weaker than those for the male subject group. Conclusions: We found the sex differences in the accuracy of prediction and the best combination of independent variables for predicting the summed widths of unerupted canines and premolars. These new models should be clinically useful, providing highly accurate prediction.

Objective: To develop a system that automatically recognizes the dentoskeletal traits on cephalograms recorded for preadolescent children and to examine performance reliability. Materials and Methods: We obtained 859 lateral cephalograms and divided them into group P (400 films taken from orthodontic patients having permanent dentition) and group M (459 films taken from those having mixed dentition). Fifty-nine cephalograms in group M were reserved for system test, and the remaining cephalograms in groups M and P were used for system development. Using a previously reported method (Yagi and Shibata, 2003), systems S_M and S_P+M were developed with the knowledge generated from groups M and P+M (combined sample of groups M and P), respectively. The system S_P that had been developed for cephalograms of permanent dentition in our previous report was also employed for comparison. To evaluate performance reliability, the systems examined the 59 reserved cephalograms. The areas of each system-identified anatomic structure surrounding the anatomic landmarks and the positions of each system-identified landmark were compared with the norms in the form of confidence ellipses. The success rates were calculated for S_P, S_M, and S_P+M. Results: The systems successfully identified all of the specified anatomic structures in all of the images. The systems S_P, S_M, and S_P+M determined the landmark positions with a mean success rate of 69% (range, 38–98%), 82% (range, 50–100%), and 82% (range, 58–100%), respectively. Conclusions: Systems S_M and S_P+M were confirmed to be accurate and reliable in recognizing the anatomic features on the cephalograms of preadolescent children.

Objectives: To examine (1) the laterality of asymmetry in movements of the right and left corners of the mouth in space during voluntary smile and (2) the laterality of asymmetry in relation to the difference between the right and left hemiface size and the handedness. Materials and Methods: Participants were 155 volunteer Japanese female adults. They were categorized into the symmetric group (n = 120) and the right-side hemiface dominant group (n = 26) according to the hemiface size. In addition, the symmetric group was categorized into the right-handed group (n = 98) and the left-handed group (n = 22) according to the Edinburgh Handedness Inventory. Position vectors of the right and left corners of the mouth were obtained from the three-dimensional facial images for the rest, the maximal lip corner retraction, and the portrait smile. The displacements of the right and left corners of the mouth for each expression and the proportions of the subjects with the right- and left-sided laterality were compared. Results: The left corner of the mouth showed significantly greater displacement (P < .01) than the right in the symmetric group for the portrait smile. The left-sided laterality was found regardless of the handedness. Conclusions: Displacements of the right and left corners of the mouth during voluntary smile were asymmetric, and the left-sided laterality was found. Also, the laterality of the facedness differed in relation to the hemiface size, but was not related to the handedness.

Objective: To investigate whether individuals with malocclusion show less skillfulness, as represented by kinematic parameters that characterize masticatory jaw movement, compared with those having normal occlusion and, if so, to examine whether more skilled movements are achieved after completion of orthodontic treatment. Materials and Methods: Lower incisor point movement in space during gum chewing was recorded, and the kinematic traits of such movement were compared among four subject groups: a Control Group (36 females with good occlusion), a Malocclusion Group (24 females with dental malocclusions), an Extraction Group (31 females who had received orthodontic treatment with premolar extraction) and a Nonextraction Group (27 females who had been treated orthodontically without tooth extraction). Before treatment, all subjects in the three experimental groups exhibited dental malocclusions and skeletal class I jaw-base relationship. Results: Compared with the Malocclusion Group, the lower normalized jerk-cost, the shorter phase durations, the more symmetric property of the velocity profile, and the smaller variance of lateral jaw-closing trajectories near the tooth intercuspation position were determined in the Extraction Group and the Nonextraction Group as well as in the Control Group. Conclusions: As measured by kinematic parameters such as normalized jerk-costs, velocity profile, and variance of movement trajectories near the endpoint of movement, dental malocclusions were associated with significantly lower skillfulness of masticatory jaw motion, whereas good occlusion and orthodontically improved occlusion (either with or without premolar extraction) were both associated with more skillful motion.

Objective: The purpose of the present study was to evaluate reliability of a system that performs automatic recognition of anatomic landmarks and adjacent structures on lateral cephalograms using landmark-dependent criteria unique to each landmark. Materials and Methods: To evaluate the reliability of the system, the system was used to examine 65 lateral cephalograms. The area of each system-identified anatomic structure surrounding the landmark and the position of each system-identified landmark were compared with norms using confidence ellipses with α = .01, which were derived from the scattergrams of 100 estimates obtained according to the method reported by Baumrind and Frantz. When the system-identified area overlapped with the norm area, anatomic structure recognition was considered successful. In addition, when the system-identified point was located within the norm area, landmark identification was considered successful. Based on these judgment criteria, success rates were calculated for all landmarks. Results: The system successfully identified all specified anatomic structures in all the images and determined the positions of the landmarks with a mean success rate of 88% (range, 77%– 100%). Conclusion: With the incorporation of the rational assessment criteria provided by confidence ellipses, the proposed system was confirmed to be reliable.

Objectives: To objectively classify shapes of the human lip vermilion in the lateral view, and to examine whether any morphologic characteristics of dentoskeletal patterns are specific to each classified lip profile pattern. Materials and Methods: Pretreatment, lateral facial photographs of 234 Japanese women were selected. Investigators with expert knowledge of the anatomic traits of the lip vermilion in the lateral view extracted from images of the face a 13-dimensional feature vector that represented lip vermilion profile shapes. The vector quantization technique was applied to the feature vectors to mathematically optimize the number of lip vermilion profile patterns. Dentoskeletal patterns that corresponded to each classified lip shape were compared statistically. Results: Seven patterns were found, and differences between patterns were notably maximized by the flatness of the anterior portion of the lip vermilion for the upper and lower lip, the position of the most protruded point of the lip vermilion, lip fissure inclination, and differences between the horizontal positions of the upper and lower lip vermilions. The dentoskeletal forms showed significant differences between classified lip vermilion profile patterns (P < .01). Conclusions: (1) Vector quantization revealed that classifying lip vermilion profiles into seven representative patterns was optimal for maximizing differences in the configuration of the lip vermilion. (2) Lip vermilion profile shapes were found to be associated with horizontal lengths of the anterior cranial base, horizontal/vertical positions, inclination and length of the mandible, and horizontal positions and labio-lingual inclinations of the upper and lower incisors.

Objective: To develop a mathematical model that simulates optimum site(s) for tooth extraction and to examine what kinds of dentoskeletal traits, in the model, influence optimizing decisions for extraction site(s). Materials and Methods: Conventional orthodontic records were obtained for 193 women who had received orthodontic tooth-extraction treatments judged as excellent treatment outcomes. The feature vector-elements that represented dentoskeletal traits, and weights of their contributions to achieving optimum simulation in the model, were determined. Results: The rate of coincidence between recommendations made by the optimized model and the actual judgments was found to be 86.0%. The elements that were sensitive to increasing the rate of coincidence and corresponding weights in judging the site(s) of tooth extraction were: protrusiveness of the upper and lower incisors (2.0), overjet and overbite (1.5), the membership grade for the skeletal Class II jaw relationship, molar relationship in the sagittal direction, the mandibular plane angle, and the severity of tooth crowding in the lower dentition (1.0). The remaining 10 feature vector-elements were also found to be indispensable for the model. Conclusions: A mathematical model that simulates optimum site(s) for orthodontic tooth extraction, with a high agreement rate (86.0%) between the system's recommendations and the actual judgments given by orthodontists, was developed. The dentoskeletal structural traits that affected optimizing decisions for orthodontic tooth-extraction site(s) were formulated and subdivided into five major categories, ie, the sagittal dentoskeletal and soft tissue relationship, the vertical dentoskeletal relationship, the transverse dental relationship, the intra-arch conditions, and the pathological conditions.

Objective: To develop a mathematical model that simulates whether or not to extract teeth in optimizing orthodontic treatment outcome and to formulate the morphologic traits sensitive to optimizing the tooth-extraction/nonextraction decisions. Materials and Methods: A total of 188 conventional orthodontic records of patients with good treatment outcomes were collected, and dentofacial morphologic traits, along with their degrees of influence in the optimized model, were determined. Results: The rate of coincidence between the recommendations given by the optimized model and the actual treatments performed was found to be 90.4%. The major morphologic traits and their corresponding influences in improving the simulation accuracy of the model were the incisor overjet (3.0) and the size of the basal arch relative to the sum of the mesiodistal crown diameters of the upper dentition (2.4) and the lower dentition (2.0). The remaining 22 morphologic-trait variables were also found to be indispensable in achieving robust simulation readings. Conclusion: A mathematical model that simulates whether or not to extract teeth in optimizing orthodontic treatment outcomes with a success rate of 90.4% at its prediction performance was developed. This model has 25 morphologic traits with four major categories (sagittal dentoskeletal and soft tissue relationship, vertical dentoskeletal relationship, transverse dental relationship, and intra-arch conditions) that affected the accuracy in determining optimal tooth extractions/nonextractions.

In patients with malocclusion and tooth-size discrepancy, the management of the tooth-size discrepancy is important. The present case report describes orthodontic treatment in a patient with moderate tooth crowding, a protruded lower lip and a high overall ratio that was caused by the large upper and lower first premolar teeth. We extracted the upper second premolar teeth and the lower first premolar teeth. After completion of active treatment, tight intercuspation of the teeth was obtained and the soft tissue profile was improved. The occlusion and the facial profile remained almost stable during the retention phase.

Objective: To investigate the laterality of the normal asymmetry of the human face, examining differences in laterality in relation to sex, growth stage, and skeletal classification. Materials and Methods: A total of 1800 Japanese subjects (651 males and 1149 females; mean age, 15 years 3 months; range, 4 years 2 months to 59 years 11 months) were selected. Individuals in the sample were categorized according to sex, one of three growth stages, and one of three skeletal patterns. Differences in length between distances from the points at which ear rods were inserted to the facial midline and the perpendicular distance from the soft-tissue menton to the facial midline were measured on a frontal facial photograph. Subjects with a discrepancy of more than 3 standard deviations of the measurement error were categorized as having left- or right-sided laterality. Results: Of subjects with facial asymmetry, 79.7% had a wider right hemiface, and 79.3% of those with chin deviation had left-sided laterality. These tendencies were independent of sex, age, or skeletal jaw relationships. In this regard, during pubertal growth, the proportion of subjects with wider right hemiface decreased (P < .0001), whereas the proportion of those with a wider left hemiface increased (P < .01), despite a consistent tendency for right-sided dominance. Conclusion: These results suggest that laterality in the normal asymmetry of the face, which is consistently found in humans, is likely to be a hereditary rather than an acquired trait.