Alveolar ridge preservation of two-wall bone defects using mineralized dentin matrix: An experimental pre-clinical study.

OBJECTIVES: To study bone healing of two-wall bone defects after alveolar ridge preservation using mineralized dentin matrix. MATERIALS AND METHODS: After distal roots extraction of second and fourth premolars (P2, P4) on one lateral mandible in 12 beagles, two-wall bone defects (5 × 5 × 5 mm) were surgically created distally to the remaining mesial roots of P2 and P4. A total of 24 sites were randomly allocated to three groups (implant material- time of execution): mineralized dentin matrix (MDM)-3 m (MDM + collagen membrane; 3 months), MDM-6 m (MDM particles + collagen membrane; 6 months), and C-6 m (collagen membrane only; 6 months). Clinical, radiographic, digital, and histological examinations were performed 3 and 6 months after surgery. RESULTS: The bone healing in MDM groups were better compared to Control group (volume of bone regenerated in total: 25.12 mm3 vs. 13.30 mm3, p = .046; trabecular volume/total volume: 58.84% vs. 39.18%, p = .001; new bone formation rate: 44.13% vs. 31.88%, p = .047). Vertically, the radiological bone level of bone defect in MDM-6 m group was higher than that in C-6 m group (vertical height of bone defect: 1.55 mm vs. 2.74 mm, p = .018). Horizontally, no significant differences in buccolingual bone width were found between MDM and C groups at any time or at any level below the alveolar ridge. The percentages of remaining MDM were <1% in both MDM-3 m and MDM-6 m groups. CONCLUSIONS: MDM improved bone healing of two-wall bone defects and might be considered as a socket fill material used following tooth extraction.

Prediction of jaw opening function after mandibular reconstruction using subject-specific musculoskeletal modelling.

BACKGROUND: Mandibular reconstruction patients often suffer abnormalities in the mandibular kinematics. In silico simulations, such as musculoskeletal modelling, can be used to predict post-operative mandibular kinematics. It is important to validate the mandibular musculoskeletal model and analyse the factors influencing its accuracy. OBJECTIVES: To investigate the jaw opening-closing movements after mandibular reconstruction, as predicted by the subject-specific musculoskeletal model, and the factors influencing its accuracy. METHODS: Ten mandibular reconstruction patients were enrolled in this study. Cone-beam computed tomography images, mandibular movements, and surface electromyogram signals were recorded preoperatively. A subject-specific mandibular musculoskeletal model was established to predict surgical outcomes using patient-averaged muscle parameter changes as model inputs. Jaw bone geometry was replaced by surgical planning results, and the muscle insertion sites were registered based on the non-rigid iterative closest point method. The predicted jaw kinematic data were validated based on 6-month post-operative measurements. Correlations between the prediction accuracy and patient characteristics (age, pathology and surgical scope) were further analysed. RESULTS: The root mean square error (RMSE) for lower incisor displacement was 31.4%, and the error for peak magnitude of jaw opening was 4.9 mm. Age, post-operative infection and radiotherapy influenced the prediction accuracy. The amount of masseter detachment showed little correlation with jaw opening. CONCLUSION: The mandibular musculoskeletal model successfully predicted short-range jaw opening functions after mandibular reconstruction. It provides a novel surgical planning method to predict the risk of developing trismus.

Evaluation of joint kinematics in patients with condylar reconstruction using mandibular motion simulation based on intraoral scanning registration.

AIM: To summarize the features of condylar kinematics in patients with condylar reconstruction using a mandibular motion simulation method based on intraoral scanning registration. MATERIALS AND METHODS: Patients undergoing unilateral segmental mandibulectomy and autogenous bone reconstruction as well as healthy volunteers were enrolled in the study. Patients were grouped based on whether the condyles were reconstructed. Mandibular movements were recorded using a jaw tracking system, and kinematic models were simulated after registration. The path inclination of the condyle point, margin of border movement, deviation, and chewing cycle were analyzed. A t test and one-way analysis of variance (ANOVA) were carried out. RESULTS: A total of 20 patients, including 6 with condylar reconstruction and 14 with condylar preservation as well as 10 healthy volunteers were included. The patients with condylar reconstruction showed flatter movement paths of the condyle points. The mean inclination angle of the condylar movement paths of the patients with condylar reconstruction (0.57 ± 12.54 degrees) was significantly smaller than that of those with condylar preservation (24.70 ± 3.90 degrees, P = 0.014) during both maximum opening and protrusion (7.04 ± 12.21 degrees and 31.12 ± 6.79 degrees, respectively, P = 0.022). The inclination angle of the condylar movement paths of the healthy volunteers was 16.81 ± 3.97 degrees during maximum opening and 21.54 ± 2.80 degrees during protrusion; no significant difference compared with the patients. The condyles of the affected side tended to deviate laterally in all patients during mouth opening and protrusion. Patients with condylar reconstruction showed more severe symptoms of mouth opening limitation and mandibular movement deviation as well as shorter chewing cycles than patients with condylar preservation. CONCLUSION: Patients with condylar reconstruction showed flatter movement paths of the condyle points, greater lateral motion range, and shorter chewing cycles than those with condylar preservation. The method of mandibular motion simulation based on intraoral scanning registration was feasible to simulate condylar movement.

[Left mandibular osteonecrosis following herpes zoster of the third branch of left trigeminal nerve: A case report].

Herpes zoster of trigeminal nerve was a common skin disease caused by varicella-zoster virus infection. Simple involvement of the third branch of trigeminal nerve was rare, and so were oral complications such as pulpitis, periodontitis, spontaneous tooth loss, bone necrosis, etc. This article presented a case of herpes zoster on the third branch of the left trigeminal nerve complicated with left mandibular osteonecrosis. We reported the case of a 64-year-old man with sudden pain in the left half of the tongue 1 month ago, and then herpes on the left facial skin appeared following with acute pain.The local hospital diagnosed it as herpes zoster and treated it with external medication. A few days later, he developed gum pain in the left mandibular posterior tooth area. He was admitted to Peking University School and Hospital of Stomatology one week ago with loose and dislodged left posterior tooth accompanied by left mandibular bone surface exposure. Clinical examination showed bilateral symmetry and no obvious restriction of mouth opening. Visible herpes zoster pigmentation and scarring on the left side of the face appeared. The left mandibular posterior tooth was missing, the exposed bone surface was about 1.5 cm×0.8 cm, and the surrounding gingiva was red and swollen, painful under pressure, with no discharge of pus. The remaining teeth in the mouth were all Ⅲ degree loosened. Imageological examination showed irregular low-density destruction of the left mandible bone, unclear boundary, and severe resorption of alveolar bone. The patient was diagnosed as left mandibular osteonecrosis. Under general anesthesia, left mandibular lesion exploration and curettage + left mandibular partial resection + adjacent flap transfer repair were performed. The patient was re-exmained 6 months after surgery, there was no redness, swelling or other abnormality in the gums and the herpes pigmentation on the left face was significantly reduced. Unfortunately, the patient had complications of postherpetic neuralgia. This case indicate that clinicians should improve their awareness of jaw necrosis, a serious oral complication of trigeminal zoster, and provide early treatment. After the inflammation was initially controlled, surgical treatment could be considered to remove the necrotic bone, curettage the inflammatory granulation tissue, and extraction of the focal teeth to avoid further deterioration of the disease.

[Application of double-layer soft tissue suture closure technique in the surgical treatment of patients with mandible medication-related osteonecrosis of the jaw of early and medium stages].

OBJECTIVE: To investigate the clinical application effect of double-layer soft tissue (DLST) suture closure technique in patients with mandible medication-related osteonecrosis of the jaw (MRONJ) of early and medium stages resulted in application of anti-bone-resorptive drugs. METHODS: Early to medium stage mandible MRONJ patients who underwent surgical treatment in the fourth ward of Peking University School and Hospital of Stomatology from October 2021 to September 2022 were included. Clinical information of the patients were collected, including primary disease, concomitant disease, medication regimen (drug type, duration of medication), MRONJ stage, clinical symptoms, imaging manifestations, etc. During surgery, after using marginal mandibulae resection to remove the necrotic bone, the wound was closed using DLST closure technique. Regular post-operative follow-up was performed to evaluate the therapeutic effect and complications of the DLST technique, the pain score and functional status of the patiens were evaluated. RESULTS: This study totally included 13 patients, 12 women and 1 man, aged (66.69±13.14) years. Seven patients had osteoporosis, 2 had lung cancer, 3 had breast cancer and 1 had prostate cancer among their primary diseases; 7 had no concomitant diseases, 2 had diabetes mellitus, 2 had cardiovascular disease and 1 had dry syndrome. Intravenous zoledronic acid were used in 9 patients, the average duration was (37.7±20.0) months, and other drugs, such as letrozole tablets were taken in 7 patients at the same time; Denosumab injection was used in 3 patients for an average of (10.3±11.9) months; Alendronate sodium tablets were taken in 5 patients for an average of (55.20±27.20) months, and prednisone acetate tablets or acarbose tablets were taken to varying degrees in 2 patients. The average post-operative follow-up was 11.9 months (9 to 17 months), and all the 13 patients were cured without complications, such as pus overflow and so forth. The pre-operative score of Karnofsky performance status (KPS) in the patients was 68.46±14.05, and the post-operative score was 82.31±15.36, and the difference was statistically significant (P < 0.05). The pre-operative score of visual analogue scale (VAS) in the patients was 5.77±0.73 and the post-operative score was 0.38±0.51, and the difference had statistical significance (P < 0.001). CONCLUSION: The double-layer soft tissue suture closure technique can achieve good clinical results in patients with MRONJ of the mandible using anti-bone-resorptive drugs alone, and can provide clinical treatment ideas for MRONJ patients with more complicated drug use.

Vascularized Free Fibular Flap in Oral and Maxillofacial Reconstruction: A 20-year Experience at a Single Institution Using 2640 Flaps.

BACKGROUND: This retrospective study reviewed all patients who underwent oral and maxillofacial reconstruction with fibular flaps in the last 2 decades at a single hospital. MATERIALS AND METHODS: We reviewed all patients with fibular flaps from 1999 to 2018. The following data were collected: sex; age; reconstruction region; diagnosis; the number of days spent in the hospital after surgery; time spent using a tourniquet for harvesting a fibula flap; vessels at the recipient site; the prevalence of unplanned reoperations; the prevalence of flap failure; history of preoperative radiotherapy; virtual surgical planning; segments of the fibula. RESULTS: In total, 2640 patients were included. The mean age was 45.5 years. The most prevalent region of reconstruction was the mandible (n=2347, 88.9%). The most common diagnosis was squamous cell carcinoma (n=1057, 40.0%). The mean number of days spent in the hospital after surgery decreased year-by-year from 18.3 days to 10.4 days. The first choice of recipient artery was the facial artery (n=1643, 62.2%) and that of the recipient vein was the external jugular vein (n=1196, 45.3%). The prevalence of surgical success was 97.6%. Prevalence of unplanned reoperations was 7.5%. CONCLUSIONS: The fibular flap was a good choice for oral and maxillofacial bony reconstruction in most cases.

Endoscopic visualization of the inferior alveolar nerve associated with somatosensory changes after impacted mandibular third molar extraction.

The aim of this study is to assess the relationship between somatosensory functional changes and inferior alveolar nerve (IAN) exposure after impacted mandibular third molars (M3M) removal. We recruited 35 patients who underwent impacted M3M extraction near the IAN. The M3Ms were extracted by combined endoscopy, piezosurgery, and contra-angle high-speed turbine handpiece. All IAN canal perforations and exposed regions were recorded and measured by endoscopy after extraction and on cone-beam computed tomography (CBCT) images before extraction. The patients were followed up 1, 7, and 35 days after surgery. A standardized quantitative sensory testing (QST) battery was performed on the lower lip skin. All of 35 cases had exposed IAN on CBCT images, 5 of which had no exposed IAN under endoscopy. For the other 30 cases, the endoscopy-measured IAN length and width were shorter than the CBCT measurements (P < 0.001). The warm and mechanical detection thresholds (MDT) on the operation side were significantly higher than the contralateral side after surgery (P < 0.05). Thermal sensory limen, MDT, and cold pain threshold were strongly correlated with the exposed IAN length and MDT also with the exposed IAN width one day after surgery. In conclusion, it was found that not all exposed IAN in CBCT images were real exposure after surgery. The intraoperative exposed IAN endoscopic measurements were smaller than by CBCT and strongly correlated with some QST parameters.

Anti-angiogenic drug aggravates the degree of anti-resorptive drug-based medication-related osteonecrosis of the jaw by impairing the proliferation and migration function of gingival fibroblasts.

BACKGROUND: Long-term use of anti-resorptive or anti-angiogenic drugs in cancer patients with odontogenic infections may lead to medication-related osteonecrosis of the jaw (MRONJ). This study investigated whether anti-angiogenic agents aggravate MRONJ occurrence in anti-resorptive-treated patients. METHODS: The clinical stage and jawbone exposure of MRONJ patients caused by different drug regimens were analyzed to ascertain the aggravation effect of anti-angiogenic drugs on anti-resorptive drug-based MRONJ. Next, a periodontitis mice model was established, and tooth extraction was performed after administering anti-resorptive and/or anti-angiogenic drugs; the imaging and histological change of the extraction socket were observed. Moreover, the cell function of gingival fibroblasts was analyzed after the treatment with anti-resorptive and/or anti-angiogenic drugs in order to evaluate their effect on the gingival tissue healing of the extraction socket. RESULTS: Patients treated with anti-angiogenic and anti-resorptive drugs had an advanced clinical stage and a bigger proportion of necrotic jawbone exposure compared to patients treated with anti-resorptive drugs alone. In vivo study further indicated a greater loss of mucosa tissue coverage above the tooth extraction in mice treated with sunitinib (Suti) + zoledronate (Zole) group (7/10) vs. Zole group (3/10) and Suti group (1/10). Micro-computed tomography (CT) and histological data showed that the new bone formation in the extraction socket was lower in Suti + Zole and Zole groups vs. Suti and control groups. In vitro data showed that the anti-angiogenic drugs had a stronger inhibitory ability on the proliferation and migration function of gingival fibroblasts than anti-resorptive drugs, and the inhibitory effect was obviously enhanced after combining zoledronate and sunitinib. CONCLUSION: Our findings provided support for a synergistic contribution of anti-angiogenic drugs to anti-resorptive drugs-based MRONJ. Importantly, the present study revealed that anti-angiogenic drugs alone do not induce severe MRONJ but aggravate the degree of MRONJ via the enhanced inhibitory function of gingival fibroblasts based on anti-resorptive drugs.

Bone morphogenetic protein receptor 1α promotes osteolytic lesion of oral squamous cell carcinoma by SHH-dependent osteoclastogenesis.

Oral squamous cell carcinoma (OSCC) is an aggressive tumor that usually invades the maxilla or mandible. The extent and pattern of mandibular bone invasion caused by OSCC are the most important factors determining the treatment plan and patients' prognosis. Yet, the process of mandibular invasion is not fully understood. The following study explores the molecular mechanism that regulates the mandibular invasion of OSCC by focusing on bone morphogenetic protein receptor 1α (BMPR1α) and Sonic hedgehog (SHH) signals. We found that BMPR1α was positively correlated to bone defect of OSCC patients. Mechanistically, BMPR1α signaling regulated the differentiation and resorption activity of osteoclasts through the interaction of OSCC cells and osteoclast progenitors, and this process was mediated by SHH secreted by tumor cells. The inhibition of SHH protected bone from tumor-induced osteolytic activity. These results provide a potential new treatment strategy for controlling OSCC from invading the jawbones.

Lateral Pterygoid Muscle Ossification After Intraoral Condylectomy.

PURPOSE: Lateral pterygoid muscle ossification has not been reported in condylectomy patients. This study aimed to explore the incidence, risk factors, and imaging characteristics of 38 cases with lateral pterygoid muscle ossification among 54 patients after condylectomy via intraoral approach. METHODS: This retrospective study included 54 patients following simultaneous orthognathic surgery and condylectomy with coronoid process resection via intraoral approach. The authors evaluated the preoperative, 1 week, 6 months, and 1 year or more postoperative computed tomographic (CT) scans for the presence of lateral pterygoid muscle ossification and its characteristics. Sex, age at the time of surgery, disease course, affected side, preoperative alkaline phosphatase, pathology diagnosis, the height of the removed condyle, condylar shape, operator, preoperative temporomandibular joint movement, and clinical symptoms were assessed as risk factors for ossification. RESULTS: No incidence of lateral pterygoid muscle ossification was found on preoperative CT images. Various small-size osseous masses were observed in the lateral pterygoid muscles on postoperative 6 months CT images in 38/54 patients (70.37%) after condylectomy. But no apparent enlargement of the osseous masses was found. No patients complained of clinical discomfort or functional disorder during the follow-up period (23.11 ± 13.16 months). No significant risk factors for ossification were found. CONCLUSIONS: Lateral pterygoid muscle ossification is relatively common in patients after condylectomy via intraoral approach. However, its enlargement is self-limited and remains stable 6 months after surgery. it has no adverse effects on the temporomandibular joint functional movement.

Reconstruction of Complete Bilateral Maxillary Defects With Free Flaps.

ABSTRACT: Reconstruction of complete bilateral maxillary defects (CBMDs) can be challenging due to the extensive loss of bone and soft tissues. This is a retrospective case series of 46 consecutive patients with CBMDs that were reconstructed with different micro-vascular free flaps. The authors aimed to evaluate the surgical outcomes and discuss the different reconstruction options in this case series. Thirty-six patients underwent reconstruction following ablation surgery for malignant tumors, 6 for benign tumors, 3 patients were treated for osteomyelitis, and 1 patient underwent free flap reconstruction for posttraumatic defects. Free fibula flap (n = 26) is the most commonly used reconstruction method in this case series, which was used in all defect types. This is followed by anterolateral thigh flap (n = 10), 5 rectus abdominis myocutaneous free flap, 3 radial forearm free flaps, and 2 composite free flaps. In this series, 44 free flaps survived, whereas only 2 flaps were lost. All patients could resume a soft diet postoperatively. Reconstruction of CBMDs with vascularized free flaps is a safe and reliable procedure.

Navigation in bone-impacted premaxillary supernumerary tooth removal: a preliminary clinical trial.

AIM: The present clinical trial aimed to preliminarily assess whether navigation could help to position impacted supernumerary teeth (STs) and reduce surgical trauma. MATERIALS AND METHODS: Subjects with an impacted supernumerary tooth (ST) in the premaxillary area were enrolled in the study and randomly distributed into a navigation group and a control group. In the navigation group, STs were positioned and extracted under real-time optic navigation. In the control group, STs were extracted depending on the surgeon's experience. Subjects were followed up for 12 to 24 weeks postsurgery. Operating time, futile bony trauma, and the positioning precision of the STs were the major outcomes assessed. Multivariate correlation analysis was performed. RESULTS: In 24 subjects, 32 STs were removed and no severe complications occurred in either group. The proportion of ST exposure at the planned access point was 100% in the navigation group and 68.75% in the control group (χ² = 5.926, P = 0.015). Futile length, futile width, and the distance between the point where the ST was initially exposed and the bony point planned for accessing it were related to both navigation/control grouping and bone thickness in the access side. For challenging STs with bone thickness of > 0.5 mm in the access side (N = 22), the futile length in the navigation group (0.0 [0.0, 4.0] mm) was significantly smaller than that in the control group (3.0 [0.0, 8.0] mm, P = 0.028). Similarly, the futile width in the navigation group (0.0 [0.0, 2.0] mm) was significantly smaller than that in the control group (2.0 [0.0, 4.0] mm, P = 0.018). CONCLUSIONS: Navigation helped to position impacted STs precisely and reduced surgical bony trauma to some extent, especially in challenging cases in which the bone in the access side was thicker than 0.5 mm.

Double-Barrel Fibula Flap Versus Vascularized Iliac Crest Flap for Mandibular Reconstruction.

PURPOSE: The double-barrel fibula flap and vascularized iliac crest flap are both commonly used for mandibular reconstruction. The present study compared the usage and reconstruction outcomes of transplanted bone with these 2 methods. PATIENTS AND METHODS: The data from 30 patients who had undergone mandibular osteotomy and reconstruction were retrospectively reviewed. Of the 30 patients, 20 received a vascularized iliac crest flap (group A) and 10 received a double-barrel fibula flap (group B). The following variables were compared between the 2 groups: volume of bone flap (VBF), volume of effective bone flap (VEBF; ie, overlap between the volume of the ideal mandible [VIM] and the VBF), usage of the bone flap (VEBF divided by the VBF), mandibular reconstruction rate (VEBF divided by the VIM), volume of needless bone flap (VNBF; ie, VBF minus VEBF; the VNBF included the volume of needless buccal bone flap [VNBBF] and the volume of needless lingual bone flap [VNLBF]), percentage of alveolar crest restoration (PACR; ie, effective bone flap width divided by ideal alveolar crest width), and height of the bone flap (HBF). The independent-samples t test and the χ2 test were used to compare the variables between the 2 groups. Statistical significance was at P ≤ .05. RESULTS: Usage of the bone flap and the length of the mandibular defect were significantly greater in group B than in group A (P = .039 and P < .001, respectively). The VBF, VNBF, and VNLBF were significantly greater in group A than in group B (P < .001 for both). The mandibular reconstruction rate, VNBBF, PACR, HBF, and tooth implantation rate were comparable between the 2 groups. CONCLUSIONS: The double-barrel fibula flap can effectively restore the height of the alveolar crest, reconstruct longer mandibular defects, and provide a better buccal and lingual appearance compared with the vascularized iliac crest flap. Although the vascularized iliac crest flap can provide sufficient bone quantity, it must be contoured to the mandible.

Regeneration of the Neocondyle After Free Fibular Flap Reconstruction of the Mandibular Condyle.

PURPOSE: Shifting of the flap position after condylar reconstruction with free fibular flaps is known to occur, but its long-term effects on postoperative esthetic outcomes have not been sufficiently reported. Therefore, in this study, we evaluated the long-term morphologic stability of the free fibular flap neocondyle. PATIENTS AND METHODS: This was a retrospective cohort study. The primary outcome variables were neocondyle regeneration and neocondyle position including the distance between the glenoid fossa and the initial neocondyle (Fo-Co), the distance between the glenoid fossa and the stable neocondyle (Fo-Co'), and shifting of the neocondyle (defined as the distance between the stable neocondyle and the initial neocondyle). The primary predictor variable was time. The other variables were age, gender, diagnosis, and number of fibular segments. Correlation analysis between the predictor variables and outcome variables was performed. RESULTS: The sample was composed of 26 patients (11 male and 15 female patients) with a mean age of 31 years. Diagnosis and number of fibular segments were significantly associated with Fo-Co and Fo-Co' (P < .05). Among the 26 patients, only 11 showed neocondyle regeneration at follow-up (group A) whereas 15 did not (group B). Neocondyle regeneration was significantly associated with patient age (P < .01). Stable Fo-Co and stable time were significantly associated with neocondyle regeneration (P < .05). The mean stable time was significantly shorter in group A (3.64 ± 1.12 months) than in group B (6.67 ± 3.85 months) (P < .05), and the mean Fo-Co' was significantly shorter in group A (13.65 ± 3.94 mm) than in group B (20.68 ± 8.87 mm) (P < .05). CONCLUSIONS: The possibility of neocondyle regeneration is higher in pediatric patients than in adults. Neocondyle regeneration could result in the movement of the neocondyle toward the glenoid fossa with a shorter stable time, which could improve neocondyle repositioning. Repositioning of the neocondyle with free fibular flaps for mandibular condyle defects is a self-adaption process for temporomandibular joint function.

Somatosensory changes in Chinese patients after coronectomy vs. total extraction of mandibular third molar: a prospective study.

OBJECTIVES: This study aimed to quantitatively compare the somatosensory function changes of inferior alveolar nerve (IAN) after mandibular third molar extraction with a surgery protocol of coronectomy, as opposed to the conventional method. MATERIALS AND METHODS: Patients with a lower third molar directly contacting IAN were recruited and assigned either to a test group (coronectomy group) or a control group (conventional extraction). A standardized quantitative sensory testing (QST) battery was performed for four times: one week before surgery and the second, seventh, and 28th days after surgery. Z-scores and the loss/gain coding system were applied for each participant. RESULTS: A total of 140 molars (test group: n = 91, control group: n = 49) were enrolled. The sensitivity of the mechanical detection threshold (MDT) and pressure pain threshold (PPT) significantly increased after surgery more than before surgery in both groups (P ≤ 0.001). After the surgery, the sensitivities of the cold detection threshold (CDT), cold pain threshold (CPT), and heat pain threshold (HPT) were significantly higher in the test group than in the control group (P ≤ 0.027). The risk of IANI was significantly larger (P = 0.041) in the test group than in the control group. CONCLUSIONS: QST was a sensitive way to detect somatosensory abnormalities even with no subjective complaint caused by surgery. Coronectomy had less influence on IAN function than conventional total extraction. CLINICAL RELEVANCE: The somatosensory function changes after mandibular third molar extraction were quantitatively studied, and coronectomy was proved a reliable alternation to reduce IAN injury rate.

Selection of Guiding Plate Combined With Surgical Navigation for Microsurgical Mandibular Reconstruction.

PURPOSE: The present study summarized selection of guiding plate combined with surgical navigation for microsurgical mandibular reconstruction. METHODS: Data from preoperative maxillofacial enhanced computed tomography (CT) scans were imported to ProPlan CMF. The authors performed virtual mandibulectomy and superimposed 3-dimensional (3D) iliac images on mandibular defects. Guiding plates including mandibular fixation device, reconstruction plate, guiding model, and occlusal splint for various mandibular hemimandibular central lateral (HCL) defects were fabricated to fix bilateral residual mandible. The model was scanned, and data were imported into ProPlan CMF and the intraoperative navigation system. Through landmark points upon the guiding plate, position of the residual mandible was determined during surgical navigation. Intraoperative navigation was used to implement the virtual plan. Sagittal, coronal, axial, and 3D reconstruction images displayed by the navigation system were used to accurately determine osteotomy sites and osteotomy trajectory during surgery. Surgical probe guidance was used to mark the osteotomy line and transfer the virtual procedure to real-time surgery. Accuracy was evaluated using chromatographic analysis. RESULTS: Different guiding plates combined with surgical navigation could be used for various mandibular defects, including mandibular fixation devices for LCL defects, reconstruction plates for LC/L/C defects, and guiding models and occlusal splints for H/L/LC defects (including mandibular ramus). In our study, average and largest shift of the mandible and osteotomy site was <5 mm. CONCLUSION: The authors summarized different ways of combining guiding plates with surgical navigation for reconstruction of various mandibular defects, which could improve clinical outcomes of this procedure with high accuracy.

Development and validation of nomogram for prediction of malignant transformation in oral leukoplakia: A large-scale cohort study.

PURPOSE: Oral leukoplakia (OL) is the well-known disorder of oral mucosa, which has potential to be malignant and can lead to squamous cell carcinoma (OSCC). In the following study, we developed a comprehensive nomogram for predicting the malignant progression of OL, based on analysis of clinicopathological variables. METHODS: A retrospective analysis of patients diagnosed with OL was performed between 1998 and 2017 at the Peking University School and Hospital of Stomatology. OL was confirmed by pre-treatment biopsy. The candidate risk factors for OL malignant transformation were screened from clinicopathological variables using the Cox proportional hazard regression analysis. The nomogram model was generated based on the COX regression results and was validated through Harrell concordance index (c-index) and calibration plots RESULTS: The incidence of OL malignant transformation (MT) was 12.2% (107/875), and the mean follow-up time was 4.5 years. The risk factors (age, histologic grade, site of lesion and smoking habit) derived from Cox proportional hazard regression analysis were incorporated in a novel nomogram model for prediction of MT severity. The c-index value of the nomogram model was 0.752, which confirmed the prediction ability; and was further confirmed by calibration plots results. CONCLUSION: Our data suggest that patients with OL who are over 50 years old, non-smokers with dysplasia, and OL lesions involving the lip, the floor of mouth, and tongue have an enhanced risk of MT. The established nomogram model has the predictive value of malignant progression, which is conductive to screen high-risk patients and guide treatment strategy.

Reconstruction of Bilateral Post-Traumatic Midfacial Defects Assisted by Three-Dimensional Craniomaxillofacial Data in Normal Chinese people-A Preliminary Study.

PURPOSE: To provide reference data for reconstruction of bilateral midfacial defects for which "mirror technique" cannot be applied. METHODS: The present study included 4 patients (3 males and 1 female) with post-traumatic bilateral midfacial fractures and defects. The most similar model was retrieved from a database of 552 normal Chinese people and used to guide preoperative virtual surgery planning. All patients underwent open reduction, internal fixation, and reconstruction surgery in 1 stage. A custom-made titanium prosthesis was used to repair the defects of frontal and naso-orbital-ethmoid (NOE) region in 1 patient. Two fibular flaps were used to repair the maxillary defects. A deep circumflex iliac artery flap was used to reconstruct large midfacial defects involving the right zygoma. A surgical navigation system was applied in 3 patients. RESULTS: The 4 patients were followed for 6 to 42 months. Two patients had finished all therapies and had satisfactory functional and cosmetic results. The appearance of 1 patient was obviously improved; that patient was still receiving treatment for denture prostheses. One patient had undergone first-stage reconstructive surgery and had normal occlusion at 6 months of follow-up. For 3 patients whose treatment had been assisted by navigation, the average surgical deviation was less than 3 mm (range, 1.5 to 2.2). For the patient whose treatment had not been assisted with navigation, the deviations differed in different areas: 3.47 mm in the right zygomaticomaxillary complex, 5.48 mm in the NOE area, and 5.91 mm in the maxillary area. CONCLUSIONS: For patients with bilateral post-traumatic midfacial defects across the midline, the use of a 3-dimensional craniomaxillofacial database can be considered a feasible method for providing reference data for preoperative planning.

Outcomes of Zygomatic Complex Reconstruction With Patient-Specific Titanium Mesh Using Computer-Assisted Techniques.

PURPOSE: Zygomatic complex defects after extensive maxillectomy can cause severe esthetic and functional deformities. Patient-specific titanium mesh fabricated using a computer-assisted technique is a promising method for such midface reconstruction. The aim of this study was to evaluate the application and clinical outcomes of this technique. PATIENTS AND METHODS: This was a retrospective study that included 9 patients with zygomatic complex defects after extensive maxillectomy from 2015 through 2017 at the authors' institution. A 3-dimensional stereo model was obtained based on mirror images of the unaffected side to fabricate a patient-specific titanium mesh using computer-assisted design and manufacturing. Titanium mesh was used to restore the contour of the zygomatic complex with free flap reconstruction after tumor resection. Anterolateral thigh flaps were used in 8 cases and a myocutaneous fibula flap was used in 1 case. Symmetry of the zygomatic complex was evaluated by measuring the zygomatic eminence on the postoperative computed tomogram, and complications were recorded during follow-up visits. Facial symmetry was self-evaluated and scored. RESULTS: Mean duration for follow-up was 27.3 months (range, 15 to 39 months). Mean deviation of the zygomatic eminence between the reconstructed and unaffected sides was 1.4 ± 0.5 mm. No significant difference was noted in the zygomatic eminence between the reconstructed and unaffected sides (P = .591). Titanium mesh exposure occurred in only 1 patient after radiotherapy. There were no other remarkable complications. All patients were satisfied with their postoperative facial symmetry. CONCLUSION: Patient-specific titanium mesh fabricated using a computer-assisted technique was an alternative option for extensive zygomatic complex reconstruction, resulting in acceptable clinical outcomes. A study with a larger sample and long-term follow-up is needed for the observation of long-term outcomes and risk of titanium mesh-related complications.

A Giant Aneurysmal Bone Cyst in the Mandibular Condyle.

Aneurysmal bone cyst (ABC) is a rare, rapidly expanding, locally destructive, and easily misdiagnosed lesion. An ABC of the condyle is rare. This report presents a 25-year-old female with a giant ABC in the left mandibular condyle. This patient was treated with surgical resection of the affected bone and immediate mandibular reconstruction using autologous bone. Follow-up to date showed no signs of recurrence. The clinical feature, imaging finding, pathogenesis, and treatment methods of ABCs are discussed.