System for automatically assessing the likelihood of inferior alveolar nerve injury

Inferior alveolar nerve (IAN) injury is a severe complication associated with mandibular third molar (MM3) extraction. Consequently, the likelihood of IAN injury must be assessed before performing such an extraction. However, existing deep learning methods for classifying the likelihood of IAN injury that rely on mask images often suffer from limited accuracy and lack of interpretability. In this paper, we propose an automated system based on panoramic radiographs, featuring a novel segmentation model SS-TransUnet and classification algorithm CD-IAN injury class. Our objective was to enhance the precision of segmentation of MM3 and mandibular canal (MC) and classification accuracy of the likelihood of IAN injury, ultimately reducing the occurrence of IAN injuries and providing a certain degree of interpretable foundation for diagnosis. The proposed segmentation model demonstrated a 0.9 % and 2.6 % enhancement in dice coefficient for MM3 and MC, accompanied by a reduction in 95 % Hausdorff distance, reaching 1.619 and 1.886, respectively. Additionally, our classification algorithm achieved an accuracy of 0.846, surpassing deep learning-based models by 3.8 %, confirming the effectiveness of our system.

Extraction of impacted mandibular third molars in close proximity to the inferior alveolar canal with coronectomy-miniscrew traction to avoid nerve injury

OBJECTIVES

Extraction of impacted mandibular third molars (IMTMs) is the most common surgery performed in the Department of Oral and Maxillofacial Surgery. Inferior alveolar nerve (IAN) injury is a rare but severe complication, and the risk is significantly higher in cases of IMTM near the inferior alveolar canal (IAC). The existing surgical method to extract such IMTMs is either not safe enough or is time-consuming. A better surgical design is needed.

MATERIALS AND METHODS

From August 2019 to June 2022, 23 patients underwent IMTM extraction by Dr. Zhao at Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Nanjing University, and were found to have IMTMs in close proximity to the IAC. Due to high IAN injury risk, these patients underwent coronectomy-miniscrew traction to extract their IMTMs.

RESULTS

The time between coronectomy-miniscrew insertion and complete removal of the IMTM was 32.65 ± 2.110 days, which was significantly shorter than that of traditional orthodontic traction. Two-point discrimination testing revealed no IAN injury, and no injury was reported by patients during follow-up. Other complications, such as severe swelling, severe bleeding, dry socket, and limited mouth opening, were not observed. Postoperative pain levels were not significantly higher in the coronectomy-miniscrew traction group than in the traditional IMTM extraction group.

CLINICAL RELEVANCE

For IMTMs that are in close proximity to the IAC and must be extracted, coronectomy-miniscrew traction is a novel approach to minimize the risk of IAN injury in a less time-consuming way with a lower possibility of complications.

The inferior alveolar nerve at the proximal fragment during bilateral sagittal split osteotomy - Is there need to reposition to distal fragment?

Inferior alveolar nerve (IAN) injury is most common in bilateral sagittal split osteotomy (BSSO) cases. The present standard is to always reposition the IAN from the proximal fragment to the distal fragment during surgery. This study aims to assess the severity and incidence of postoperative injury and the recovery of the inferior alveolar nerve in proximal fragment entrapment.

Methods

- A total of 35 patients (70 BSSO osteotomies) with mandibular deformities requiring movements equal to or less than 6 mm were selected. Twenty out of 70 osteotomies had IAN on the proximal fragment (Group 1) while splitting. Group 2 included 20 osteotomies with IAN on the distal segment in the same patients. Therefore, 15 patients who had IAN on distal segments on both sides were excluded from this study. All the BSSO procedures were performed by the same surgeon. Postoperative recovery and follow-up were performed on the immediate 1st postoperative day and at 3-, 6- and 12-month intervals. The nociception (pin-prick discrimination) test and mechanoreceptive tactile skin test with cotton fibrils were performed by a third clinician who was blinded to the procedure to assess IAN sensation.

Conclusion

There was no significant difference between the groups in the recovery of IAN sensation after 6 months and the 1-year period. Hence reposition of IAN from the proximal segment to the distal segment during BSSO surgery may not be mandatory if the required movement is within 6 mm. This avoids unnecessary manipulation of the IAN over the proximal fragment.

Inferior alveolar nerve damage secondary to orthodontic treatment: A systematic scoping review

BACKGROUND

Neurosensory impairment is a common complication following inferior alveolar nerve (IAN) damage.

OBJECTIVE

To document and report the various causes, diagnosis, and management of IAN damage secondary to orthodontic treatment.

METHODS

An electronic search for studies that reported IAN damage in patients undergoing orthodontic treatment was performed up to July 15, 2020 using MEDLINE, Embase, and PubMed databases. Descriptive analyses and linear regression model were performed.

RESULTS

A total of 15 case reports were identified including 16 patients with an overall mean age of 23.3. All the included studies reported temporary sensory alterations which manifested as anesthesia (19%, n = 3), paresthesia (75%, n = 12), or combined (6%, n = 1). The majority of cases managed by stopping the orthodontic force (75%, n = 12), followed by appliance adjustments (19%, n = 3), providing a bite plate (13%, n = 2), and/or providing pharmacological management (38%, n = 6). Full recovery median duration reported in all cases following the aforementioned managements was 17.5 days.

CONCLUSIONS

IAN damage secondary to orthodontic treatment is emerging in the literature in recent years. Identifying high risk patients with close proximity to the IAN canal is a must to formulate a proper treatment plan to avoid such complications.

The Trigeminal Nerve Injury

Trigeminal nerve branches are never far from the operating field of the oral and maxillofacial surgeon. Increasingly the surgeon is required to provide accurate diagnosis and grading of trigeminal nerve injury, and surgical management by oral and maxillofacial surgeons will become common. Although trauma and ablative procedures for head and neck pathology can cause injuries, dentoalveolar surgical procedures remain an important cause of injury to the fifth cranial nerve, with the third division being the main branch affected. Oral and maxillofacial surgeons should be aware of strategies of avoiding iatrogenic injury, and know when referral and surgical management are appropriate.

A systematic review of the complications of high-risk third molar removal and coronectomy: development of a decision tree model and preliminary health economic analysis to assist in treatment planning

Coronectomy is an alternative surgical technique for the management of high-risk third molars. It involves the removal of the crown of a tooth and the deliberate retention of the roots, thereby avoiding injury to the inferior alveolar nerve (IAN). Previous studies have suggested that it reduces the risk of nerve injury when compared with surgical extraction. The purpose of this study was to systematically review the incidence of complications following coronectomy such as IAN injury, pain, dry socket, infection, root migration, and need for re-operation. A comparative cost analysis of coronectomy and surgical extraction was done based on the results of the review. This provides an insight into the economic implications of the two procedures. A search through the MEDLINE database via Ovid, PubMed, Scopus, EMBASE via Ovid, and Web of Science, was carried out to extract randomised and non-randomised controlled trials. Four studies fulfilled the inclusion criteria. A meta-analysis was conducted to measure the overall effect of each outcome. The pooled odds ratio (OR) for IAN injury was 0.16 (95% CI 0.01 to 0.39). Coronectomy reduced this risk by 84%. Dry socket may occur less frequently following coronectomy whereas infection did not show a higher incidence with either intervention. Root migration was found to occur in 13%-85% of cases and the average incidence of re-operation was 2.2%. The ratio of the average costs was 1.12 favouring coronectomy if cone-beam computed tomography (CBCT) was not done prior to the procedure. If a scan was taken routinely for coronectomy, the cost ratio marginally favoured extraction. Coronectomy reduced the risk of nerve injury in high-risk third molars. Definitive conclusions, however, cannot be made for outcomes such as the need for re-operation, which may alter the cost ratio of coronectomy:extraction, as higher quality studies with longer follow-up are needed.

Photobiomodulation therapy for management of inferior alveolar nerve injury post-extraction of impacted lower third molars

Purpose

Inferior alveolar nerve (IAN) injury is one of the most serious complications after extraction of impacted lower third molars. Photobiomodulation (PBM) therapy has been noted to reduce pain and inflammation while promoting tissue healing. This study examined the efficacy of PBM therapy tested in a case series of patients with postoperative IAN injury.

Material and methods

20 patients with post-extraction IAN injury were involved in this study and divided into two groups. In the study group, PBM therapy (808-nm laser, 16 mW, 3 J/cm²) was used every other day for 2 weeks solely on post-extraction sockets in 10 patients diagnosed with IAN injury. In the control group, mecobalamine was prescribed to 10 patients with IAN injury. Objective and subjective recovery of IAN paresthesia was evaluated using clinical neurosensory testing and visual analog score.

Results

All patients showed improvement in both objective and subjective examination. Notably, the visual analog score was significantly improved after PBM treatment compared to the mecobalamine treatment (p < 0.05).

Conclusion

PBM therapy with 808-nm laser appears to be an effective approach to manage paresthesia post-IAN injury following impacted third molar surgery. Given the limited sample size in this study, large-scale, placebo-controlled, multi-center randomized controlled trials are needed for further validation of this innovative treatment.

Neurosensory deficit following mandibular sagittal split osteotomy: A comparative study between positional screws and miniplates fixation

This retrospective study compared the incidence of long-term inferior alveolar nerve injury for positional screws and miniplate fixation of bilateral sagittal split osteotomies carried out in 2 hospitals in Scotland. The study involved a mixture of mandibular setback and advancement surgery. The outcome of neurosensory deficit (NSD) was solely based on subjective assessment by the surgeons and patients' reported alteration in sensation. Numbness, tingling and any alterations in sensation beyond 6 months were considered long-term inferior alveolar nerve injury. This study was conducted on 28 sagittal split osteotomies (group 1) which were fixed with three upper border fixation screws and 36 sagittal split osteotomies (group 2) which were fixed with upper border sliding plate. The reported and documented neurosensory deficits were analysed. The difference in the number of cases of long-term inferior alveolar nerve injury between the 2 methods was 10.3%; the 95% confidence interval for the difference was [-2.94 to 23.5], p = 0.1612. Upper border plate was associated with more long-term NSD but there is insufficient evidence to prove that one method was more superior to the other. The need for a prospective randomized trial was highlighted.

Protocol for Removal of Third Molar Root Tips from the Inferior Alveolar Canal-Crossing the line

INTRODUCTION

The safe removal of third molars involved with the inferior alveolar canal (IAC) has been an area of concern since long. Many times we hesitate for the removal of third molars, fearing injury to the inferior alveolar nerve.

MATERIALS AND METHODS

The authors here describe a simple technique which can be used to remove third molars showing evidence of proximity to IAC on presurgical radiographic evaluation, as well as those root tips which, during removal, accidentally enter the IAC space.

CONCLUSION

A step-by-step protocol is presented along with necessary precautions during the operative procedure.

Diagnostic value of panoramic radiography in predicting inferior alveolar nerve injury after mandibular third molar extraction: a meta-analysis

BACKGROUND

The aim of this study was to evaluate the predictive value of panoramic radiography on inferior alveolar nerve (IAN) injury after extraction of the mandibular third molar.

METHODS

Relevant studies up to 1 June 2014 that discussed the association of panoramic radiography signs and post-mandibular third molar extraction IAN injury were systematically retrieved from the databases of PubMed, Embase, Springerlink, Web of Science and Cochrane library. The effect size of pooled sensitivity, specificity, positive likelihood ratios (PLR), negative likelihood ratios (NLR) and diagnostic odds ratio (DOR) with their 95% confidence intervals (CI) were statistically analysed with Meta-disc 1.4 software.

RESULTS

Nine articles were included in this meta-analysis. The pooled estimates of sensitivity and specificity were 0.56 (95% CI: 0.50-0.61) and 0.86 (95% CI: 0.84-0.87), respectively. The overall PLR was 3.46 (95% CI: 2.02-5.92) and overall NLR was 0.58 (95% CI: 0.45-0.73). The pooled estimate of DOR was 6.49 (95% CI: 2.92-14.44). The area under the summary receiver operating characteristic curve was 0.7143 ± 0.0604.

CONCLUSIONS

The meta-analysis indicated that interpretation of panoramic radiography based on darkening of the root had a high specificity in predicting IAN injury after mandibular third molar extraction. However, the ability of this panoramic radiography marker to detect true positive IAN injury was not satisfactory.