The accidental displacement of tooth roots into the mandibular canal is a serious complication during tooth extractions in oral and maxillofacial surgery, often resulting in direct damage to the structural and functional integrity of the inferior alveolar neurovascular bundle (IANB). This article reviews the anatomical features of the mandibular canal, the IANB, and adjacent tooth roots; identifies high-risk factors and anatomically vulnerable sites for root displacement; and outlines the clinical manifestations and radiographic characteristics of intraoperative root intrusion into the mandibular canal. Furthermore, management principles, surgical approaches and techniques, inferior alveolar nerve injury treatment, and prognostic considerations are discussed. The aim of this review is to provide a comprehensive clinical reference for improving surgical outcomes, and reducing postoperative complications.
Humans ; Tooth Extraction/adverse effects* ; Mandible/surgery* ; Tooth Root ; Mandibular Nerve/anatomy & histology* ; Postoperative Complications/prevention & control* ; Intraoperative Complications ; Mandibular Nerve Injuries/etiology*

Resection of oral and maxillofacial tumors is often accompanied by the inferior alveolar nerve neurectomy, resulting in abnormal sensation in lower lip. It is generally believed that spontaneous sensory recovery in this nerve injury is difficult. However, during our follow-up, patients with inferior alveolar nerve sacrifice showed different degrees of lower lip sensory recovery. In this study, a prospective cohort study was conducted to demonstrate this phenomenon and analyze the factors influencing sensory recovery. A mental nerve transection model of Thy1-YFP mice and tissue clearing technique were used to explore possible mechanisms in this process. Gene silencing and overexpression experiments were then conducted to detect the changes in cell morphology and molecular markers. In our follow-up, 75% of patients with unilateral inferior alveolar nerve neurectomy had complete sensory recovery of the lower lip 12 months postoperatively. Patients with younger age, malignant tumors, and preservation of ipsilateral buccal and lingual nerves had a shorter recovery time. The buccal nerve collateral sprouting compensation was observed in the lower lip tissue of Thy1-YFP mice. ApoD was demonstrated to be involved in axon growth and peripheral nerve sensory recovery in the animal model. TGF-β inhibited the expression of STAT3 and the transcription of ApoD in Schwann cells through Zfp423. Overall, after sacrificing the inferior alveolar nerve, the collateral compensation of the ipsilateral buccal nerve could innervate the sensation. And this process was regulated by TGF-β-Zfp423-ApoD pathway.
Mice ; Animals ; Lip/innervation* ; Prospective Studies ; Mandibular Nerve/pathology* ; Sensation/physiology* ; Trigeminal Nerve Injuries/pathology*

Objective: To evaluate the risk factors of inferior alveolar nerve injury (IANI) after surgical removal of the mandibular third molars (M3) and present a new risk scoring system to predict the probability of IANI. Methods: Patients who underwent extraction of M3 in the Stomatology Hospital, Zhejiang University School of Medicine from April 2017 to December 2019 were involved. The investigators enrolled a sample composed of 949 mandibular third molars. Prediction model was used for univariate and multivariate analysis of gender, age, M3, inferior alveolar canal (IAC), and the contact between M3 and IAC, to assess the risk factors of IANI. Combined with the risk factors determined by the outcomes of prediction model, the risk scoring system was constructed. The diagnostic performance of each cut-off score was examined to conduct a risk stratification of IANI risk scores. The predictive ability and reliability of the model were evaluated. Results: In prediction model, twenty nine cases (4.4%, 29/664) experienced postoperative IANI. Number of root (P<0.01), depth of impaction (P<0.05), contact between M3 and IAC (P<0.01) and their contact position (P<0.05) were statistically significant as contributing risk factors of IANI. Specifically, the incidence of temporary IANI was higher in those who aged under 25 years (P<0.001), while female suffer more permanent injury (P<0.05). Based on the IANI risk scoring system, patients were stratified into low-risk, middle-risk and high-risk groups at cutoff scores of 3 and 4. The area under the receiver operator characteristic curve of the risk scoring system were 0.81 [95%CI (0.70-0.90), P=0.002] and 0.80 [95%CI (0.68-0.92), P=0.007] towards good discrimination. Conclusions: Age, gender, number of root, depth of impaction, and contact between M3 and IAC were risk factors of IANI. IANI risk scoring system might help in preoperative assessment, recognition of high-risk cases and decision-making to reduce IANI.
Aged ; Female ; Humans ; Mandible/surgery* ; Mandibular Nerve ; Molar, Third/surgery* ; Reproducibility of Results ; Risk Factors ; Tooth Extraction/adverse effects* ; Trigeminal Nerve Injuries/etiology*

Trigeminal nerve injury as a consequence of lower third molar surgery is a notorious complication and may affect the patient in long term. Inferior alveolar nerve (IAN) and lingual nerve (LN) injury result in different degree of neurosensory deficit and also other neurological symptoms. The long term effects may include persistent sensory loss, chronic pain and depression. It is crucial to understand the pathophysiology of the nerve injury from lower third molar surgery. Surgery remains the most promising treatment in moderate-to-severe nerve injuries. There are limitations in the current treatment methods and full recovery is not commonly achievable. It is better to prevent nerve injury than to treat with unpredictable results. Coronectomy has been proved to be effective in reducing IAN injury and carries minimal long-term morbidity. New technologies, like the roles of erythropoietin and stem cell therapy, are being investigated for neuroprotection and neural regeneration. Breakthroughs in basic and translational research are required to improve the clinical outcomes of the current treatment modalities of third molar surgery-related nerve injury.
Chronic Pain ; Depression ; Erythropoietin ; Humans ; Lingual Nerve ; Mandibular Nerve ; Molar, Third ; Neuroprotection ; Postoperative Complications ; Regeneration ; Stem Cells ; Translational Medical Research ; Trigeminal Nerve Injuries ; Trigeminal Nerve

A sialocele is a subcutaneous cavity containing saliva, most often caused by facial trauma or iatrogenic complications. In subcondylar fractures, most surgeons are conscious of facial nerve injury; however, they usually pay little attention to the parotid duct injury. We report the case of a 41-year-old man with a sialocele, approximately 5×3 cm in size, which developed 1 week after subcondylar fracture reduction. The sialocele became progressively enlarged despite conservative management. Computed tomography showed a thin-walled cyst between the body and tail of the parotid gland. Fluid leakage outside the cyst was noted where the skin was thin. Sialography showed a cutting edge of the inferior interlobular major duct before forming the common major duct that seemed to be injured during the subcondylar fracture reduction process. We decided on prompt surgical treatment, and the sialocele was completely excised. A duct from the parotid tail, secreting salivary secretion into the cyst, was ligated. Botulinum toxin was administrated to block the salivary secretion and preventing recurrence. Treatment was successful. In addition, we found that parotid major ducts are enveloped by the deep lobe and extensive dissection during the subcondylar fracture reduction may cause parotid major duct injury.
Adult ; Botulinum Toxins ; Facial Nerve Injuries ; Humans ; Intraoperative Complications ; Mandibular Fractures ; Parotid Gland ; Recurrence ; Saliva ; Sialography ; Skin ; Surgeons ; Tail

BACKGROUNDThe treatment of the condylar fractures is difficult. Factors that result in the fractures are complex. The objective of this morphometric study was to investigate the relationship between condylar fracture patterns and condylar morphological characteristics.

METHODSWe conducted a retrospective analysis of 107 patients admitted to the West China Hospital of Stomatology for bilateral condylar fractures caused by parasymphyseal impact. The patients were divided into five groups according to the type of condylar fracture. Ten parameters were evaluated on three-dimensional (3D) reconstruction mandible models through the Mimics 16.0 (Materialize Leuven, Belgium) anthropometry toolkit. Each parameter of the 3D models was analyzed using multivariate analysis. Multinomial logistic regression analyses were used to examine the relationships between the five groups.

RESULTSThe results showed that the differences of condylar head width (M1), condylar neck width (M3), the ratio of condylar head width to condylar anteroposterior diameter (M1/M2), the ratio of condylar head width to condylar neck width (M1/M3), the ratio of condylar height to ramus height (M8/M7), and mandibular angle (M10) were statistically significant (p < 0.05). Type A condylar head fractures were positively associated with M1 (compared to Type B: OR =1.627, 95% CI: 1.123, 2.359; compared to Type C: OR = 1.705, 95% CI: 1.170, 2.484) and M1/M2 (compared to Type B: OR =1.034, 95% CI: 0.879, 2.484). Type B condylar head fractures were negatively associated with M10 (compared to Type C: OR = 0.909, 95% CI: 0.821, 1.007). Condylar neck fractures were negatively associated with M3 (compared to condylar head: OR = 0.382, CI: 0.203, 0.720 ; compared to condylar base: OR = 0.436, 95% CI: 0.218, 0.874), and positively associated with M1/M3 (compared to condylar head: OR = 1.229, 95% CI: 1.063, 1.420 compared to condylar base: OR = 1.223, 95% CI: 1.034, 1.447). Condylar base fractures were positively associated with M10 (OR = 1.095, 95% CI: 1.008, 1.189) and negatively associated with M8/M7 (OR = 0.855, 95% CI: 0.763, 0.959) as compared with condylar head fractures.

CONCLUSIONSCondylar fracture pattern is associated with the anatomical features of the condyles when a fracture occurs from parasymphyseal impact.

Adult ; Female ; Fractures, Bone ; surgery ; Humans ; Male ; Mandibular Condyle ; injuries ; surgery ; Mandibular Fractures ; surgery ; Middle Aged ; Multivariate Analysis ; Retrospective Studies ; Young Adult

This article summarized the advances in treatment and research of temporomandibular joint surgery in the last 5 years which was presented in "The 2nd Condyle Fracture and Temporomandibular Joint Ankylosis Symposium". The content includes 5 parts: non-surgical treatment of children condyle fracture and long-term follow-up, the improvement of operative approach for condyle fracture and key techniques, the importance and the method for the simultanesous reduction of disc in condylar fracture treatment, the development of traumatic temporomandibular joint ankylosis similar to hypertrophic non-union and the improved safety and accuracy by applying digital surgery in joint surgery.
Ankylosis ; etiology ; Humans ; Mandibular Condyle ; injuries ; Mandibular Fractures ; complications ; therapy ; Temporomandibular Joint ; surgery ; Temporomandibular Joint Disorders ; etiology

OBJECTIVETo establish a miniature pig model of mandibular osteoradionecrosis (ORN).

METHODSA single dose of irradiation (IR25 Gy, 28 Gy) was delivered via an electronic linear accelerator to the right mandible of 24 miniature pigs by utilizing three dimensional conformal radiotherapy (3D-CRT). The first molar of the mandible was extracted 2 months after radiation. Mandibular ORN was diagnosed through gross observation, X-ray film, CT, and histopathologic examination.

RESULTSAt 3-4 months after radiation, all animals suffered from mandibular ORN after dental extraction. The symptoms of ORN were more severe in the 28 Gy group than in the 25 Gy group.

CONCLUSIONA miniature pig model of mandibular ORN can be established through 25 Gy irradiation + dental extraction.

Animals ; Mandible ; Mandibular Diseases ; pathology ; Molar ; Osteoradionecrosis ; pathology ; Particle Accelerators ; Radiation Injuries, Experimental ; pathology ; Radiotherapy, Conformal ; adverse effects ; Swine ; Swine, Miniature ; Tooth Extraction

BACKGROUND: Osteoradionecrosis is a delayed complication from radiation therapy which causes chronic pain, infection and constant deformity after necrosis. Most of the osteoradionecrosis occurs spontaneously or after the primary oncologic surgery, dental extraction or by trauma of prosthesis. The treatment of osteoradionecrosis relies on both conservative measures and surgical measures. The fibular osteocutaneous free flap has become more popular choice for reconstruction of maxillofacial defects as a treatment of osteoradionecrosis. METHODS: We presented our experiences from 7 patients with osteoradionecrosis who have had reconstruction surgery with fibular osteocutaneous free flap at National Cancer Center during the recent 5 years. We performed segmental mandibular resection with fibular osteocutaneous free flap for all 7 patients of advanced osteoradionecrosis who were not controlled by conservative treatment such as wound irrigation, debridement, and antibiotics. RESULTS: A wide range of techniques were available for the reconstruction of composite defects resulted from the treatment of advanced mandibular osteoradionecrosis. Significant improvement was noted in relieving pain and treating trismus after the surgery however difficulty in swallowing and xerostomia showed less improvement. CONCLUSIONS: We concluded that fibular osteocutaneous free flap can be performed safely in patients with osteoradionecrosis and yields positive outcomes with significantly increased success rate. The fibular osteocutaneous free flap was our preferred choice for the mandibular reconstruction due to its versatility and predictability.
Anti-Bacterial Agents ; Chronic Pain ; Congenital Abnormalities ; Debridement ; Deglutition ; Free Tissue Flaps* ; Humans ; Mandible ; Mandibular Reconstruction ; Necrosis ; Osteoradionecrosis* ; Prostheses and Implants ; Trismus ; Wounds and Injuries ; Xerostomia

It has recently been reported that long-standing post-traumatic open bite can be successfully corrected with botulinum toxin type A (BTX-A) injection into the anterior belly of the digastric muscle (ABDM). The report documented an individual with bilaterally symmetrical and otherwise unremarkable anterior digastric musculature. However, the existence of variant anterior digastric musculature is common and may complicate the management of anterior open bite with BTX-A injection. Screening for variant ABDM can be accomplished via ultrasound, computed tomography, and magnetic resonance imaging. Screening for variant ABDM should be performed prior to BTX-A injection in order to account for musculature that may exert undesired forces, such as inferolateral deviation, on the anterior mandible in patients with anterior open bite.
Anatomy, Regional ; Botulinum Toxins, Type A* ; Humans ; Magnetic Resonance Imaging ; Malocclusion ; Mandible ; Mandibular Injuries ; Mass Screening* ; Nerve Block ; Open Bite* ; Orthognathic Surgery ; Ultrasonography