Search

This paper proposes a convolutional neural network (CNN)-based deep learning model for predicting the difficulty of extracting a mandibular third molar using a panoramic radiographic image. The applied dataset includes a total of 1053 mandibular third molars from 600 preoperative panoramic radiographic images. The extraction difficulty was evaluated based on the consensus of three human observers using the Pederson difficulty score (PDS). The classification model used a ResNet-34 pretrained on the ImageNet dataset. The correlation between the PDS values determined by the proposed model and those measured by the experts was calculated. The prediction accuracies for C1 (depth), C2 (ramal relationship), and C3 (angulation) were 78.91%, 82.03%, and 90.23%, respectively. The results confirm that the proposed CNN-based deep learning model could be used to predict the difficulty of extracting a mandibular third molar using a panoramic radiographic image.

The purpose of this study was to evaluate the skeletal units of a normal mandible (class I) and a prognathic mandible (class III), to compare the groups, and to investigate the key functional unit responsible for mandibular prognathism. Hemi-mandibles of 101 cases were evaluated by cone-beam computed tomography. Of these, 50 cases had Class I and 51 had Class III mandibles. The length, volume, and volume/length ratio of each skeletal unit were measured. The ratios of the condyle, body unit, and sum of the hemi-mandible between Class I and Class III showed statistically significant results (P<0.05). However, the ratios of angle, coronoid, and symphysis units did not show any statistical significance on comparison. Dependent on gender, in males the ratio of the condyle of the hemi-mandible showed statistically significant results (P<0.05). Meanwhile in females the ratio of the body and sum of the hemi-mandible showed statistically significant results (P<0.05). Accordingly, the mandibular body and condylar units are thinner in mandibular prognathism. On the basis of the functional matrix theory to determine the aetiology of mandibular prognathism, the key skeletal units are the body and condylar units., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Ameloblastoma is a rare, benign tumor found in the jaw. These tumors have a tendency for locally aggressive expansion, and thus require surgical removal. For the previous 3 decades, autologous bone grafting and free flap surgeries have been most commonly used to correct bone defects after surgical removal of the lesion. In this report, the authors describe a case of unicystic ameloblastoma in a 14-year-old girl who was successfully treated with mandibular regeneration, attained by autologous human bone marrow mesenchymal stem cells without any autologous bone graft and free flap transfer. This case shows that autologous human bone marrow mesenchymal stem cells can be used as an alternative method to autologous bone graft and free flap transfer in a large bone defect of the jaw.

Intraoral Vertical Ramus Osteotomy (IVRO) is one of the operative techniques used for orthognathic surgery. The aim of this study was to assess the posterior displacement of the proximal segment in patients undergoing IVRO at 1-year follow-up. In total, 52 hemimandibles from 26 patients who underwent IVRO in whom the proximal segment was posteriorly displaced without overlap with the distal segment at immediate post-operation (Imm) (30 cases, experimental group), and 26 patients in whom the proximal segment was not posteriorly displaced with overlap with the distal segment (Imm) (22 cases, control group) under three-dimensional computed tomography (3D CT) were included in the study. To analyze the movement of segments, the positions of the mid condyle point (MCP) and angle of condyle line (Con) were determined and the movement of the ramus angle (posterior edge of proximal segments) was measured at the proximal segment. Regression of the proximal segment in sagittal direction of the MCP was observed in both groups and all directions of the ramus angle in the experimental group, and only sagittal direction in the control group. In conclusion, posterior displacement of the proximal segment after IVRO showed tendency to regress its original position., (Copyright © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Purpose: The goal of this study was to understand the three-dimensional (3D) structural characteristics of hemifacial microsomia (HFM) mandible in terms of skeletal units, especially to locate the underdeveloped skeletal regions for treatment. Another goal was to compare the HFM structure of different age groups to understand growth potential relevant to treatment scheduling., Materials and Methods: We reconstructed 3D mandibles from computed tomographic images of French and Korean patients with HFM (N = 28; group II) and normal subjects (N = 27; group I). Each mandible was classified by Pruzansky's HFM types I, II and III, and by age group (child, adolescent, and adult). The mandible was divided into skeletal units, and geometrical representation by skeletal unit line was performed, including the condylar, body, coronoid, and angular units. Their length and angulations were measured and statistically analyzed., Results: The results showed that the affected condylar unit in type II HFM and the condylar/coronoid unit in type III were smaller in young age groups than were other units. The angulation between the skeletal units in type II, though not type III, tended toward normalcy with age, but not to the normal degree of angulations in group I., Conclusion: Our study shows the major involvement of condylar unit and minor involvement of body unit for HFM, improving with age in type II. The mandibular skeletal unit analysis seems to be a useful tool for individualized diagnosis, allowing identification of the major etiopathogenic area and treatment planning, including a simulation to set up a regimen for successful reconstruction of HFM., (Copyright © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Distraction osteogenesis a surgical procedure conducted to improve craniofacial deformities. Compared with conventional operations, this technique has advantages such as the ability to lengthen the soft tissue and hard tissue. Therefore, this method is used to treat severe craniofacial abnormalities.The major disadvantage of distraction osteogenesis is the long treatment period. If the consolidation period is not sufficiently long after the distraction period, complications such as discontinuity or contraction of newly formed bone may occur. Recently, many researchers have attempted to develop methods for enhancing the ossification of newly formed bone, reducing shrinkage, and shortening the overall treatment period.The authors injected autologous bone marrow-derived mesenchymal stem cells during the consolidation phase after distraction osteogenesis surgery in a bilateral mandibular hypoplasia patient. Here, the authors report the treatment results, which were found to be favorable.

Purpose: This article reviews a few of the commonly used types of vascularized osseous free flaps in maxillofacial reconstruction, which still represents the gold standard of restoration. We also discuss the developing concepts in maxillofacial reconstruction., Recent Findings: Most of the literature reconfirms the established patterns of reconstruction with the aid of vascularized osseous free flaps. This method of free-tissue transfer is also feasible in cases of osteoradionecrosis or bisphosphonate-related osteonecrosis of the jaw. These flaps are also suitable for prosthetic restoration using osseointegrated dental implants., Summary: Vascularized osseous free flaps still remain the standard of care. Improvements upon the free-tissue transfer method employing vascularized osseous free flaps, such as distraction osteogenesis, tissue engineering, and imaging techniques, currently require further development, but these technologies could lead to improved outcomes of maxillofacial reconstruction in the near future.

The 3D architecture of the mandible contributes to the functional and morphological characteristics of the lower one third of craniofacial region. The mandible has six distinct functional units, and its architecture is the sum of balanced growth of each functional unit and surrounding matrix. A dentofacial deformity (DFD) with malocclusion can be interpreted as their unbalanced growth. In order to characterize the mandibular 3D architecture, we analyzed the 3D reconstructed computed tomography (CT) images in terms of functional units. We evaluated both sides of 30 datasets of 3D CT scans of normal controls (N = 6) and patients with prognathic (N = 17) or retrognathic (N = 7) mandibles. We first identified and evaluated reference points to define mandibular functional units and compared their linear and angular measurements of DFD with normal group. The condylar and body length, the ratio of condyle/coronoid length, and the condylar head axis angle showed the statistically significant differences between groups. From these results, we could define the 3D reference points for functional units and identify the 3D architectural characteristics of DFD mandibles. These models may help us improve diagnosis and treatment planning to let them return to the normal and balanced architecture for DFD.

Background: Paresthesia is a well-known complication of extraction of mandibular third molars (MTMs). The authors evaluated the relationship between paresthesia after MTM extraction and the cortical integrity of the inferior alveolar canal (IAC) by using computed tomography (CT)., Methods: The authors designed a retrospective cohort study involving participants considered, on the basis of panoramic imaging, to be at high risk of experiencing injury of the inferior alveolar nerve who subsequently underwent CT imaging and extraction of the MTMs. The primary predictor variable was the contact relationship between the IAC and the MTM as viewed on a CT image, classified into three groups: group 1, no contact; group 2, contact between the MTM and the intact IAC cortex; group 3, contact between the MTM and the interrupted IAC cortex. The secondary predictor variable was the number of CT image slices showing the cortical interruption around the MTM. The outcome variable was the presence or absence of postoperative paresthesia after MTM extraction., Results: The study sample comprised 179 participants who underwent MTM extraction (a total of 259 MTMs). Their mean age was 23.6 years, and 85 (47.5 percent) were male. The overall prevalence of paresthesia was 4.2 percent (11 of 259 teeth). The prevalence of paresthesia in group 3 (involving an interrupted IAC cortex) was 11.8 percent (10 of 85 cases), while for group 2 (involving an intact IAC cortex) and group 1 (involving no contact) it was 1.0 percent (1 of 98 cases) and 0.0 percent (no cases), respectively. The frequency of nerve damage increased with the number of CT image slices showing loss of cortical integrity (P=.043)., Conclusions: The results of this study indicate that loss of IAC cortical integrity is associated with an increased risk of experiencing paresthesia after MTM extraction.