OBJECTIVES: This study aimed to establish a new treatment of the mandibular second molars with external root resorption caused by impacted teeth to preserve the affected teeth and their vital pulps. METHODS: For mandibular second molars clinically diagnosed as external root resorption caused by impacted teeth, debridement and removal of the root at the resorption site via micro-apical surgery and direct capping of the pulp with bioactive material on the surface of the root amputation via vital pulp therapy were performed immediately after the impacted teeth were extracted. RESULTS: The external root resorption of the affected tooth was ceased. It was asymptomatic with intact crown, normal pulp, periapical alveolar bone reconstruction, normal periodontal ligament, continuous bone sclerosis, and no periapical translucency in radiographic examination at the 1-year postoperative follow-up, thus showing good prognosis. CONCLUSIONS Simultaneous combination of micro-apical surgery and vital pulp therapy after extraction of impacted teeth could successfully preserve mandibular second molars with ERR caused by impacted teeth and their vital pulps.
Humans ; Tooth, Impacted/surgery* ; Molar ; Mandible ; Dental Pulp ; Root Canal Therapy ; Root Resorption/etiology* ; Tooth Extraction

OBJECTIVE: To evaluate the decompensation effectiveness and alveolar bone remodeling of mandibular anterior teeth after preoperative orthodontic treatment in high-angle patients with skeletal class Ⅱ malocclusion using lateral cephalogram and cone-beam computed tomography (CBCT). METHODS: Thirty high-angle patients with skeletal class Ⅱ malocclusion who had received preoperative orthodontic treatment and orthognathic surgery in Peking University School and Hospital of Stomatology between Ja-nuary 2017 and August 2022 and had taken lateral cephalogram and CBCT before and after preoperative orthodontic treatment were selected. Items were measured with lateral cephalogram including: The lower central incisor (L1)-Frankfort plane angle (L1-FH), the L1-mandibular plane angle (L1-MP), the L1-nasion-supramental angle (L1-NB) and the vertical distance from the incisal edge of lower central incisor to NB line (L1-NB distance), etc. The incidence of dehiscence/fenestration and the length of dehiscence at labial side (d-La) and lingual side (d-Li) were measured using CBCT. Pearson correlation analysis was used to evaluate the correlation between the changes of d-Li of L1 and age, duration of preoperative orthodontic treatment and the cephalometric measurements before preoperative orthodontic treatment to screen out risk factors affecting the periodontal risk of preoperative orthodontic treatment in high-angle patients with skeletal class Ⅱ malocclusions. RESULTS: After preoperative orthodontic treatment, L1-FH, L1-MP, L1-NB and L1-NB distances changed by 11.56°±5.62°, -11.13°±5.53°, -11.57°±5.43° and (-4.99±1.89) mm, respectively, and the differences were all statistically significant (P < 0.05). Among the 180 measured mandibular anterior teeth, 45 cases with labial dehiscence/fenestration before preoperative orthodontic treatment (T0) had no longer labial dehiscence/fenestration after preope-rative orthodontic treatment (T1); 142 cases without lingual dehiscence/fenestration at T0 had lingual dehiscence/fenestration at T1. After preoperative orthodontic treatment, the d-La of lower lateral incisors (L2), lower canines (L3) and lower anterior teeth (L1+L2+L3) decreased by (0.95±2.22) mm, (1.20±3.23) mm and (0.68±2.50) mm, respectively, and the differences were statistically significant (P < 0.05); the d-Li of L1, L2, L3 and L1+L2+L3 increased by (4.43±1.94) mm, (4.53±2.35) mm, (3.19±2.80) mm and (4.05±2.46) mm, respectively, and the differences were statistically significant (P < 0.05). The increase of d-Li of L1 was positively correlated with L1-FH (r=0.373, P=0.042). CONCLUSION This study showed that high-angle patients with skeletal class Ⅱ ma-locclusion could achieve ideal decompensation effect of mandibular anterior teeth after preoperative orthodontic treatment with bilateral mandibular first premolars extracted, but the lingual periodontal risk of mandibular anterior teeth was increased. This risk could be correlated to L1-FH before preoperative orthodontic treatment, which should be paid more attention in the design of orthodontic-orthognathic surgical treatment.
Humans ; Malocclusion, Angle Class III ; Malocclusion, Angle Class II/surgery* ; Facial Bones ; Incisor ; Orthognathic Surgical Procedures ; Cone-Beam Computed Tomography ; Mandible

The mandibular metastatic spread of carcinoma from the thyroid gland is exceedingly rare. Follicular thyroid carcinoma is the second most common type of thyroid carcinoma，accounting for approximately 10% to 15% of all thyroid cancers. The prognosis of FTC is relatively satisfactory. Due to its rich blood transport, it is easy to metastasize hematological, with the main sites of metastasis are bone and lung. However，mandibular metastasis of thyroid follicular carcinoma is rare. We report a case of thyroid follicular carcinoma that metastasized to the ascending ramus of the mandible 21 years after surgery.The operation was successfully completed, and there was no recurrence during postoperative follow-up. Due to the absence of obvious clinical symptoms in the patient, the diagnosis and treatment were challenging. We have provided detailed radiographic and pathological images to facilitate understanding and discussion of the disease.
Humans ; Adenocarcinoma, Follicular/pathology* ; Thyroid Neoplasms/surgery* ; Prognosis ; Mandible

Epidermoid cysts are generally benign neoplastic lesions, the etiology of which is unclear and is mainly related to epithelial cells left in the tissues during the embryonic period and traumatically implanted in the tissues. The most common intraosseous sites are the phalanges and the skull. Epidermoid cysts occurring in the jaws are clinically rare. In this paper, we report a case of epidermoid cyst occurring in the mandible with embedded teeth and discuss the etiology, clinical manifestations, diagnosis, and treatment of epidermoid cysts in the jaws in the context of the relevant literature.
Humans ; Epidermal Cyst/surgery* ; Skull ; Mandible ; Diagnosis, Differential ; Epithelial Cells

OBJECTIVE: To preliminarily verify the effectiveness of self-designed artificial condyle-mandibular distraction (AC-MD) complex in the treatment of Pruzansky type ⅡB and Ⅲ hemifacial microsomia (HFM) through model test. METHODS: Five children with Pruzansky type ⅡB and Ⅲ HFM who were treated with mandibular distraction osteogenesis (MDO) between December 2016 and December 2021 were selected as the subjects. There were 3 boys and 2 girls wih an average age of 8.4 years (range, 6-10 years). Virtual surgery and model test of AC-MD complex were performed according to preoperative skull CT of children. The model was obtained by three-dimensional (3D) printing according to the children's CT data at a ratio of 1∶1. The occlusal guide plate was designed and 3D printed according to the children's toothpaste model. The results of the model test and the virtual surgery were matched in three dimensions to calculate the error of the residual condyle on the affected side, and the model test was matched with the actual skull CT after MDO to measure and compare the inclination rotation of the mandible, the distance between the condylar of the healthy side and the residual condyle of the affected side, and the lengthening length of the mandible. RESULTS: The error of residual condyle was (1.07±0.78) mm. The inclination rotation of the mandible, the distance between the condylar of the healthy side and the residual condyle of the affected side, and the lengthening length of the mandible after 3D printing model test were significantly larger than those after MDO ( P<0.05). CONCLUSION In the model test, the implantation of AC-MD complex can immediately rotate the mandible to the horizontal position and improve facial symmetry, and the residual condyle segment can be guided close to the articular fossa or the preset pseudoarticular position of the skull base after operation.
Male ; Child ; Female ; Humans ; Goldenhar Syndrome/surgery* ; Mandible/surgery* ; Osteogenesis, Distraction/methods* ; Printing, Three-Dimensional ; Facial Asymmetry/surgery*

Objective:To explore the perioperative airway management and treatment of newborns with micrognathia and laryngomalacia. Methods:From January to December 2022, a total of 6 newborns with micrognathia and laryngomalacia were included. Preoperative laryngoscopy revealed concomitant laryngomalacia. These micrognathia were diagnosed as Pierre Robin sequences. All patients had grade Ⅱ or higher symptoms of laryngeal obstruction and required oxygen therapy or non-invasive ventilatory support. All patients underwent simultaneous laryngomalacia surgery and mandibular distraction osteogenesis. The shortened aryepiglottic folds were ablated using a low-temperature plasma radiofrequency during the operation. Tracheal intubation was maintained for 3-5 days postoperatively. Polysomnography（PSG） and airway CT examination were performed before and 3 months after the surgery. Results:Among the 6 patients, 4 required oxygen therapy preoperatively and 2 required non-invasiveventilatory support. The mean age of patients was 40 days at surgery. The inferior alveolar nerve bundle was not damaged during the operation, and there were no signs of mandibular branch injury such as facial asymmetry after the surgery. Laryngomalacia presented as mixed type: type Ⅱ+ type Ⅲ. The maximum mandibular distraction distance was 20 mm, the minimum was 12 mm, and the mean was 16 mm. The posterior airway space increased from a preoperative average of 3.5 mm to a postoperative average of 9.5 mm. The AHI decreased from a mean of 5.65 to 0.85, and the lowest oxygen saturation increased from a mean of 78% to 95%. All patients were successfully extubated after the surgery, and symptoms of laryngeal obstruction such as hypoxia and feeding difficulties disappeared. Conclusion:Newborns with micrognathia and laryngomalacia have multi-planar airway obstruction. Simultaneous laryngomalacia surgery and mandibular distraction osteogenesis are safe and feasible, and can effectively alleviate symptoms of laryngeal obstruction such as hypoxia and feeding difficulties, while significantly improving the appearance of micrognathia.
Humans ; Infant, Newborn ; Infant ; Micrognathism/surgery* ; Laryngomalacia/surgery* ; Treatment Outcome ; Mandible/surgery* ; Airway Obstruction/surgery* ; Intubation, Intratracheal ; Laryngeal Diseases ; Osteogenesis, Distraction ; Oxygen ; Retrospective Studies

At present, mandibular defect repair and reconstruction is not only a simple sense of mandibular continuity restoration, but also a restoration of the physiologically positional relationship and movement balance of the upper and lower jaws. Eventually, the implantation of osseointegrated dental implants and implant-supported dental restoration should be accomplished to complete the reconstruction of the functional mandible. The technique can integrate multiple procedures such as fibular bone grafting, simultaneous dental implants and traction osteogenesis, and the perfect integration with digital technology can significantly improve the accuracy of digital dental implant traction technique. This paper will summarize and conclude the key points of the application of digital dental implant traction technique in mandibular defect reconstruction, in order to provide new ideas for the development of digital technique.
Humans ; Mandibular Reconstruction ; Dental Implants ; Dental Implantation, Endosseous/methods* ; Mandibular Neoplasms/surgery* ; Fibula/transplantation* ; Bone Transplantation/methods* ; Mandible/surgery*

Objective: To compare cusp and U-tube registration methods of dynamic navigation system in dental implant placement. Methods: Twenty resin mandible models and 40 implants were utilized, with implants being placed by a single researcher using one of the two registration methods selected at random. Accuracy was measured through the superimposition of the final and planned implant positions. Angular deviation, three-dimensional (3D) entry deviation, and 3D apex deviation were analyzed. Results: The 3D entry deviation, and 3D apex deviation and angular deviation of cusp group and U-tube group were (1.07±0.46) and (0.93±0.54) mm, (1.16±0.55) and (1.03±0.53) mm, 2.06°±0.98°and 1.62°±0.97°. No significant differences (t=0.91, P=0.368; t=0.79, P=0.436; t=1.42, P=0.164) were observed when comparing these two registration methods. Conclusions: Both the cusp and U-tube registration methods are highly accurate when implemented in vitro. The cusp registration technique can also overcome several of the limitations of the U-tube approach, and it is convenient for clinic.
Dental Implantation, Endosseous/methods* ; Dental Implants ; Surgery, Computer-Assisted/methods* ; Mandible/surgery* ; Imaging, Three-Dimensional ; Cone-Beam Computed Tomography ; Computer-Aided Design

Mandibular defects caused by injuries, tumors, and infections are common and can severely affect mandibular function and the patient's appearance. However, mandible reconstruction with a mandibular bionic structure remains challenging. Inspired by the process of intramembranous ossification in mandibular development, a hierarchical vascularized engineered bone consisting of angiogenesis and osteogenesis modules has been produced. Moreover, the hierarchical vascular network and bone structure generated by these hierarchical vascularized engineered bone modules match the particular anatomical structure of the mandible. The ultra-tough polyion complex has been used as the basic scaffold for hierarchical vascularized engineered bone for ensuring better reconstruction of mandible function. According to the results of in vivo experiments, the bone regenerated using hierarchical vascularized engineered bone is similar to the natural mandibular bone in terms of morphology and genomics. The sonic hedgehog signaling pathway is specifically activated in hierarchical vascularized engineered bone, indicating that the new bone in hierarchical vascularized engineered bone underwent a process of intramembranous ossification identical to that of mandible development. Thus, hierarchical vascularized engineered bone has a high potential for clinical application in mandibular defect reconstruction. Moreover, the concept based on developmental processes and bionic structures provides an effective strategy for tissue regeneration.
Bone Regeneration ; Bone Transplantation/methods* ; Hedgehog Proteins ; Humans ; Mandible/surgery* ; Osteogenesis

OBJECTIVE: To evaluate the relevant indicators affecting difficulty in the extraction of impacted mandibular third molars and score difficulty of different operation and risk indicators, so as to build an intuitive and accurate scale to help operators make more accurate analysis and prediction of difficulty before the operation. METHODS: Based on literature and the clinical review, the difficulty indicators of tooth extraction were summarized. Firstly, 10 doctors from Peking University School and Hospital of Stomatology who had been engaged in alveolar surgery for a long time established an expert nominal group, and then rated whether the summarized indicators needed to be retained in the form of face-to-face questionnaires. A level 1 and 2 item frame for evaluating difficulty in the tooth extraction was formed after discussion; Then Delphi method was used to send a questionnaire to 30 experts by e-mail. After two rounds of scoring and modification, the scale of difficulty in the extraction of impacted mandibular third molars was formed. RESULTS: The recycling rate of two rounds of questionnaires was 100.0%, which showed that the experts were very enthusiastic about the study; The authority coefficients (Cr) of the two rounds of Delphi expert consultation were both 0.92, which showed that the results were representative and authoritative. After two rounds of grading and revision, the variable coefficient (CV) decreased and the Kendall's concordance coefficient (W) increased, which were statistically significant: In the first round, the CV was 0.24 and W was 0.56 (P < 0.001), and in the second, the CV was 0.19 and W was 0.72 (P < 0.001), which indicated that there was a good convergence among the expert opinions. Finally, a scale of difficulty in the tooth extraction containing 12 items at level A and 37 items at level B was formed, including operation difficulty indicators, risk difficulty indicators and common difficulty indicators. CONCLUSION Based on comprehensive literature retrieval, the study has put forward the concept that difficulty in the extraction of impacted mandibular third molars is composed of operation difficulty and risk difficulty. Using Delphi method, the long-term clinical experience and professional knowledge of experts are transformed into quantitative indicators as a scoring scale. The scale has certain representativeness and authority.
Delphi Technique ; Humans ; Mandible/surgery* ; Molar, Third/surgery* ; Tooth Extraction ; Tooth, Impacted/surgery*