Comparative Volume Analysis of Alveolar Defects by 3D Simulation.

A precise volumetric assessment of maxillary alveolar defects in patients with cleft lip and palate can reduce donor site morbidity or allow accurate preparation of bone substitutes in future applications. However, there is a lack of agreement regarding the optimal volumetric technique to adopt. This study measured the alveolar bone defects by using two cone-beam computed tomography (CBCT)-based surgical simulation methods. Presurgical CBCT scans from 32 patients with unilateral or bilateral clefts undergoing alveolar bone graft surgery were analyzed. Two hands-on CBCT-based volumetric measurement methods were compared: the 3D real-scale printed model-based surgical method and the virtual surgical method. Different densities of CBCT were compared. Intra- and inter-examiner reliability was assessed. For patients with unilateral clefts, the average alveolar defect volumes were 1.09 ± 0.24 and 1.09 ± 0.25 mL (p > 0.05) for 3D printing- and virtual-based models, respectively; for patients with bilateral clefts, they were 2.05 ± 0.22 and 2.02 ± 0.27 mL (p > 0.05), respectively. Bland-Altman analysis revealed that the methods were equivalent for unilateral and bilateral alveolar cleft defect assessment. No significant differences or linear relationships were observed between adjacent different densities of CBCT for model production to obtain the measured volumes. Intra- and inter-examiner reliability was moderate to good (intraclass correlation coefficient (ICC) > 0.6) for all measurements. This study revealed that the volume of unilateral and bilateral alveolar cleft defects can be equally quantified by 3D-printed and virtual surgical simulation methods and provides alveolar defect-specific volumes which can serve as a reference for planning and execution of alveolar bone graft surgery.

Customized Three-Dimensional Printing Spacers for Bone Positioning in Orthognathic Surgery for Correction and Prevention of Facial Asymmetry.

Orthognathic surgery is a powerful tool for correction of facial asymmetry and malocclusion. The goal is to achieve good dental function and facial aesthetics. Three-dimensional simulation is used for surgical planning, and bone gaps could be created to achieve facial balance. In this study, customized "spacers" were made using computer-aided design and three-dimensional printing for guides for use during surgery. With the final three-dimensional plan, the skull images were exported to 3-Matic software, where spacers were designed according to the bone gaps. Three-dimensionally-printed spacers were made and used to facilitate positioning and fixation. Consecutive patients with facial asymmetry were recruited in this prospective study. The postoperative outcome was assessed using a visual analogue scale and the three-dimensional facial surface area discrepancy index for subjective and objective evaluation. There were 12 patients and a total of 19 spacers for the Le Fort I and mandibular ramus segments. The spacers worked nicely during the bone fixation process. Mean preoperative and postoperative visual analogue scale scores were 4.83 and 7.14, with a statistically significant improvement for facial symmetry (p = 0.018). Mean preoperative and postoperative facial surface area discrepancy index was 0.95 and 0.98, and the correction of asymmetry was significant (p = 0.009). There were no related surgical complications. All patients were satisfied with the correction of facial asymmetry and malocclusion. The custom-made, three-dimensionally-printed spacers help to achieve surgical precision to correct and prevent facial asymmetry in orthognathic surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Therapeutic, IV.

Perception of Lip Cant as a Sign of Facial Deformity: Assessment by Laypersons and Professionals on Composite Face Photographs.

OBJECTIVE: Lip cant is a feature of facial deformity and commonly seen in patients with facial asymmetry. Because of its importance in aesthetic assessment, it is necessary to define the perceptions of lip cant and investigate differences in perception between laypersons and professionals. These data were insufficient in the literature. METHODS: Photographs of 30 male and 30 female individuals with normal faces were collected, and the lip line angles were measured. A composite facial photograph was generated from superimpositions of the normal faces. Lip line angles from 0° to 9° were made, with other facial features remaining unchanged. The test photographs were arranged in random fashion and evaluated by 64 laypersons and 30 professionals. Comparisons and cumulative frequency were performed. RESULTS: The lip line angle from the 60 normal persons was 1.20° ± 0.94°. From the composite test photographs, the average first perception of lip cant was 3.25° 1± 1.36° in the laypersons and 1.70° ± 0.69° in the professionals. The average first perception of unacceptable lip cant was 6.40° ± 1.79° in the laypersons and 4.40°1. ± 1.65° in the professionals. Significant differences were found between the first perception and perception as unacceptable lip cant, as well as between the laypersons and the professionals. Cumulative data showed that 82.8% of the laypersons perceived lip cant at 4°, and 17.2% of them felt it aesthetically unacceptable. Few laypersons (1.6%) considered less than 4° unacceptable. CONCLUSIONS: The data in this study provide helpful information in the evaluation of lip cant. A lip cant of 4° or more could be considered an indication for clinical management.

The pterygomaxillary junction: An imaging study for surgical information of LeFort I osteotomy.

Maxillary osteotomy is a common surgical procedure and often involves separation of the pterygomaxillary junction (PMJ), which is a "blinded" procedure with inherent risks. Knowledge of the PMJ structure is essential. It remains unclear whether patients with different facial types have different PMJ structures, or different surgical outcome. This study evaluated the computed tomographic images of 283 consecutive patients who received orthognathic surgery. Patients were classified into Angle class I, II, III and cleft lip/palate groups. The results showed that the PMJ was 5.1 ± 1.4 mm in thickness, 9.7 ± 1.7 mm in width, and 102.0 ± 4.0 degrees relative to the sagittal plane in the level of posterior nasal spine. There were no statistically significant differences in these measurements among the groups. The class III group demonstrated significantly smaller angle relative to the maxillary occlusal plane. The cleft group showed significantly longer vertical distance between the posterior nasal spine and the lower border of PMJ, shorter distance between the second molar and PMJ, and longer distance between the descending palatine artery and PMJ. With regard to postoperative outcome, the cleft group showed higher incidence of pterygoid plate fracture. The results in this study provide additional surgical anatomic information.