Inferior alveolar nerve injury after mandibular third molar extraction: a literature review

Automatic mandibular canal detection using a deep convolutional neural network

The practicability of deep learning techniques has been demonstrated by their successful implementation in varied fields, including diagnostic imaging for clinicians. In accordance with the increasing demands in the healthcare industry, techniques for automatic prediction and detection are being widely researched. Particularly in dentistry, for various reasons, automated mandibular canal detection has become highly desirable. The positioning of the inferior alveolar nerve (IAN), which is one of the major structures in the mandible, is crucial to prevent nerve injury during surgical procedures. However, automatic segmentation using Cone beam computed tomography (CBCT) poses certain difficulties, such as the complex appearance of the human skull, limited number of datasets, unclear edges, and noisy images. Using work-in-progress automation software, experiments were conducted with models based on 2D SegNet, 2D and 3D U-Nets as preliminary research for a dental segmentation automation tool. The 2D U-Net with adjacent images demonstrates higher global accuracy of 0.82 than naïve U-Net variants. The 2D SegNet showed the second highest global accuracy of 0.96, and the 3D U-Net showed the best global accuracy of 0.99. The automated canal detection system through deep learning will contribute significantly to efficient treatment planning and to reducing patients’ discomfort by a dentist. This study will be a preliminary report and an opportunity to explore the application of deep learning to other dental fields.

Envisioning Post-treatment Occlusions after Space Closure Using Temporary Skeletal Anchorage Devices

Missing posterior teeth and posterior tooth extractions are commonly seen and needed within orthodontic practices. With the invention of temporary skeletal anchorage devices (TSADs), clinicians can now effectively close posterior tooth spaces. Various molar occlusions are discussed to help clinicians envision post-treatment occlusions after posterior teeth space closure using TSADs.

An analysis of the first and second mandibular molar roots proximity to the inferior alveolar canal and cortical plates using cone beam computed tomography among the Saudi population

Objectives:

To evaluate the relationship of the first and second mandibular molar roots to the inferior alveolar canal (IAC) and cortical plates using cone beam computed tomography (CBCT) in the Saudi population.

Methods:

Scans of 60 patients were collected retrospectively from the dental hospital database in King Saud University, Riyadh, Kingdom of Saudi Arabia. Measurements of the right and left first and second mandibular molars for each dental root and the mandibular bone thickness were determined. The position of the IAC was estimated using axial, coronal, and sagittal views. Three examiners performed the measurements independently.

Results:

The mean distance between the root apices of the mandibular molars and the IAC ranged from 1.68-4.79 mm, whereas the mean distance from the outer surface of the buccal cortical plate to the buccal root surface ranged from 2.33-6.72 mm. Similarly, the mean distance from the outer surface of the lingual cortical plate to the lingual root surface ranged from 2.62-4.80 mm. Finally, the mean distance from the outer surface of the lingual cortical plate to the outer surface of the buccal cortical plate was 11.93-13.19 mm.

Conclusion:

The measurements reported in this study may be of value to practitioners treating Saudi patients, as they need to be familiar with the distance of the mandibular first and second molars in relation to the IAC and surrounding cortical plates to accurately assess and plan endodontic surgeries, surgical extractions, and implant placements.

A Novel Orthodontic Extraction Method for Removal of Impacted Mandibular Third Molars in Close Proximity to Inferior Alveolar Nerve

PURPOSE

The present study has proposed a novel orthodontic extraction method with a removable appliance to avoid inferior alveolar nerve (IAN) injury during impacted mandibular third molar removal.

PATIENTS AND METHODS

In the present study, 16 patients were enrolled and divided into 2 groups per patient choice. In the orthodontic extraction group (n = 8), a removable appliance was first applied to move the root tips away from the IAN, and the tooth was subsequently removed. In the traditional extraction group (n = 8), each patient had the tooth removed immediately by the same surgeon.

RESULTS

All teeth were extracted successfully. All 8 patients in the orthodontic extraction group had had their impacted mandibular third molar removed without IAN injury after surgery. In contrast, 4 patients in the traditional extraction group had experienced transient IAN injury, and the symptoms persisted for 2 to 8 weeks. None of the patients experienced permanent IAN damage.

CONCLUSIONS

Orthodontic extraction with a removable appliance to separate the IAN and impacted mandibular third molar could be a good alternative treatment option to avoid IAN injury in high-risk cases.

Nerve Injury After Surgical Excision of Mandibular Third Molars Under Local Anesthesia: An Audit

Background

Injury of the inferior alveolar nerve (IAN) sustained during surgical removal of an impacted lower third molar may cause paresthesia of the lower lip, chin, lower gingivae and anterior teeth. Lingual nerve (LN) injuries may result in ipsilateral paresthesia of the anterior two thirds of the tongue, mucosa of floor of mouth and lingual gingivae. A close anatomic relationship between the roots of the third molar and mandibular canal places the IAN at risk of damage.

Purpose

The primary aim of this retrospective audit was to ascertain the incidence of IAN and LN damage after mandibular third molar surgery in National Dental Centre Singapore. A secondary aim was to identify the contributory factors for the risk of IAN and LN nerve injury on the basis of the data collected.

Methods

This retrospective audit included 1276 mandibular third molar surgical removals performed in the local anesthesia operating theatre (LAOT) at the National Dental Centre Singapore (NDCS) from April to December 2013. Data included patient details, clinical characteristics, and 1 week postoperative presence/absence of sensory alteration as reported by the patient.

Results

Summary of results- Out of 1276 third molar sites audited, 8 (0.62%) sites had altered sensation of the IAN and 1 (0.078%) had altered sensation of the LN at 1 week postoperative review.

Conclusion

The incidence of IAN injury (0.62%) and lingual Nerve injury (0.08%) after one week from surgery in our audit was low compared to similar studies. This retrospective audit did not show any correlation of nerve injury to age, gender, race, site, angulation of tooth, grade of operator, removal of bone or tooth division. There was no single radiological sign associated with paresthesia, although the most common radiological signs were interruption of the canal line and darkening of the roots.

An analysis of the first and second mandibular molar roots proximity to the inferior alveolar canal and cortical plates using cone beam computed tomography among the Saudi population

OBJECTIVES

To evaluate the relationship of the first and second mandibular molar roots to the inferior alveolar canal (IAC) and cortical plates using cone beam computed tomography (CBCT) in the Saudi population. Methods: Scans of 60 patients were collected retrospectively from the dental hospital database in King Saud University, Riyadh, Kingdom of Saudi Arabia. Measurements of the right and left first and second mandibular molars for each dental root and the mandibular bone thickness were determined. The position of the IAC was estimated using axial, coronal, and sagittal views. Three examiners performed the measurements independently.

RESULTS

The mean distance between the root apices of the mandibular molars and the IAC ranged from 1.68-4.79 mm, whereas the mean distance from the outer surface of the buccal cortical plate to the buccal root surface ranged from 2.33-6.72 mm. Similarly, the mean distance from the outer surface of the lingual cortical plate to the lingual root surface ranged from 2.62-4.80 mm. Finally, the mean distance from the outer surface of the lingual cortical plate to the outer surface of the buccal cortical plate was 11.93-13.19 mm. Conclusion: The measurements reported in this study may be of value to practitioners treating Saudi patients, as they need to be familiar with the distance of the mandibular first and second molars in relation to the IAC and surrounding cortical plates to accurately assess and plan endodontic surgeries, surgical extractions, and implant placements.

Computer-Aided Design/Computer-Aided Manufacturing Cutting Guides for Odontectomy of Deeply Impacted Mandibular Third Molars

AIM:

To evaluate a new technique for surgical removal of deeply impacted mandibular third molars (DIMTM), using computer-guided cutting guide to maintain inferior alveolar nerve (IAN) integrity and the covering buccal bone.

PATIENTS AND METHODS:

Eighteen cases indicated for removal of DIMTM. Cone-beam Computed Tomography (CBCTs) used to determine the tooth’s relation to the IAN. Computer-guided software used for fabrication of surgical cutting guide stent to expose the impacted tooth and repositioning of bone after odontectomy without fixation. Clinical assessment included a neurosensory deficit of IAN, pain using a visual analogue scale (VAS), facial swelling, and maximal mouth opening (MMO). CBCTs were taken immediately and six months postoperatively to evaluate position and healing of bone.

RESULTS:

None of the patients showed a permanent neurological deficit of IAN while all patients showed normal parameters of pain, facial swelling and MMO.

CONCLUSION:

this technique has shown the accurate determination of the bony window cuts with subsequent preservation of IAN and external oblique ridge.

Delayed paresthesia of inferior alveolar nerve after dental surgery: case report and related pathophysiology

Paresthesia is an altered sensation of the skin, manifesting as numbness, partial loss of local sensitivity, burning, or tingling. The inferior alveolar nerve (IAN) is the third branch of the trigeminal nerve and is very important in dental treatment. IAN paresthesia may occur after various dental procedures such as simple anesthetic injections, surgical procedures, and endodontic treatment, and is reported to range from 0.35% to 8.4%. The altered sensation usually follows immediately after the procedure, and reports of late onset of nerve involvement are rare. This report presents a rare case of delayed paresthesia after dental surgery and discusses the pathophysiology of IAN delayed paresthesia.

Is The Late Mandibular Fracture From Third Molar Extraction a Risk Towards Malpractice? Case Report with the Analysis of Ethical and Legal Aspects

Objectives

The present study reports a case of late mandibular fracture due to third molar extraction and highlights the inherent clinical, ethical and legal aspects related to this surgical complication.

Material and Methods

A female patient underwent surgical procedure for the extraction of the mandibular right third molar. Two days after the surgery the patient reported pain and altered occlusion in the right side of the mandible. After clinical and radiographic re-examination, the diagnosis of late mandibular fracture was established. A second surgery, under general anaesthesia, was performed for the fixation of the mandibular bone.

Results

The fractured parts were reduced and fixed with locking plate systems and 2 mm screws following load-sharing principles. The masticatory function showed optimal performance within 7 and 21 days after the surgery. Complete bone healing was observed within 1 year of follow-up.

Conclusions

For satisfactory surgical outcomes, adequate surgical planning and techniques must be performed. Signed informed consents explaining the risks and benefits of the treatment must be used to avoid ethical and legal disputes in dentistry.

The horizontal inclination angle is associated with the risk of inferior alveolar nerve injury during the extraction of mandibular third molars

The extraction of mandibular third molars can lead to injury to the inferior alveolar nerve. Hence, it is important to assess the proximity of the root to the inferior alveolar canal before extraction. The classification system of Pell and Gregory and the Winter classification are commonly used to evaluate the positional relationship of the third molar based on radiographs. This retrospective study involving 105 mandibular third molars was performed to assess whether these systems reflect the proximity of the root to the canal (based on computed tomography images), and to identify risk factors for nerve injury. Regarding the prediction of computed tomography-verified canal invasion, the sensitivity, specificity, and positive and negative predictive values were high for each Pell and Gregory category when there was radiographic evidence. The mean distance of invasion was significantly greater in class III than in class I. However, there were no significant differences between the Winter inclination categories. The mean distance differed significantly between a horizontal inclination angle to the buccal side of >5° and an angle of ≤5°. Thus, a horizontal inclination angle >5° represents a novel risk factor for nerve injury.

A case report of unusual anatomical variation: externalisation of inferior alveolar nerve

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Incidence of permanent IAN damage ranges from 0.35% to 8.4%.

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Timely, accurate pre-operative visualisation of nerve is paramount in a safe clinical practice and reduces the risk of unnecessary litigations.

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CT imaging has better sensitivity and specificity in demonstrating nerve and tooth relationships compared to plain film radiographs.

Introduction

The risks of third molar surgery have been well documented with damage to the inferior alveolar nerve (IAN) being one of the largest concerns.

Presentation of case

This case report presents an impacted third molar with associated dentigerous cyst in which the IAN is externalised and runs along the lateral surface of the mandible.

Discussion

This is an extremely rare anatomical variation with most IANs lying inferior and lingually to third molars. This case reiterates the limitations of standard radiographic techniques such as the orthopantomogram (OPG).

Conslusion

We would advocate the use of cone beam computed tomography (CBCT) in cases which have adverse plain radiographic features to allow appropriate surgical planning.

Temporal Evaluation of Neurosensory Complications After Mandibular Third Molar Extraction: Current Problems for Diagnosis and Treatment

Objective:

This retrospective study aimed to report the incidence of neurosensory complications after third molar extraction and also to identify current problems and discuss appropriate management of these complications.

Method:

Patients who underwent extraction of deeply impacted mandibular third molars under general anesthesia were included. The following epidemiological data were retrospectively gathered from medical charts: type of neurosensory complication, treatment for complication, and outcome.

Results:

A total 369 mandibular third molars were extracted in 210 patients under general anesthesia during this study period. Thirty-one of the 369 teeth (8.4%) in 31 patients had neurosensory complications during the first postoperative week resulting from inferior alveolar nerve damage. Neurosensory complications lasting from 1 to 3 months postoperatively included 17 cases of hypoesthesia and 8 of dysesthesia in 19 patients. Five cases of hypoesthesia and 4 of dysesthesia in 5 patients persisted over 1 year postoperatively. Sixteen of 369 teeth (4.3%) in 16 patients had persistent neurosensory complications after third molar extraction under general anesthesia. Stellate ganglion block was performed in 4 patients. Early initiation of stellate ganglion block (within 2 weeks postoperatively) produced better outcomes than late stellate ganglion block (over 6 months postoperatively).

Conclusion:

Refractory neurosensory complications after third molar extraction often combine both hypoesthesia and dysesthesia. Current problems in diagnosis and treatment included delayed detection of dysesthesia and the lack of uniform timing of stellate ganglion block. In the future, routinely inquiring about dysesthesia and promptly providing affected patients with information about stellate ganglion block might produce better outcomes.

Retention of Asymptomatic Third Molars May be Unwise

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION

What is the risk of future extraction of asymptomatic third molars? A systematic review. Bouloux GF, Busaidy KF, Beirne OR, Chuang S-K, Dodson TB. J Oral Maxillofac Surg 2015;73(5):806-11.

SOURCE OF FUNDING

No external funding source is identified although all 5 authors appear to be on the American Association of Oral and Maxillofacial Surgery 3rd Molar Task Force

TYPE OF STUDY/DESIGN

Systematic review.

Neurosensoric disturbances after surgical removal of the mandibular third molar based on either panoramic imaging or cone beam CT scanning: A randomized controlled trial (RCT)

OBJECTIVE

Pre-surgical CBCT has been suggested before removal of the mandibular third molar. Currently, the standard-of-care is two-dimensional (2D) panoramic imaging. The aim of this randomized controlled trial was to analyse possible differences in neurosensoric disturbances of the inferior alveolar nerve between patients undergoing either panoramic imaging or CBCT before surgical removal of the mandibular third molar. Furthermore, the aim was to perform a sensitivity analysis to assess the statistical significance of different assumptions related to sample size calculations.

METHODS

230 patients were randomized to a scan group and a non-scan group. All patients were referred from practicing dentists in the Copenhagen area. Inclusion criteria were overlap of the root complex and the mandibular canal on a 2D radiographic image. Central allocation of the randomization code and double blind settings were established. The surgical removal was performed in a specialized surgical practice geographically and personally separated from the study practice. Registration of neurosensoric anomalies was performed with a Semmes-Weinstein test and a visual analogue scale questionnaire pre- and post-surgically.

RESULTS

In the scan group (n = 114), 21 episodes of neurosensoric disturbances were registered and in the non-scan group (n = 116), 13 episodes of neurosensoric disturbances were registered. There was no statistically significant difference between the two groups (p = 0.14). Performing a sensitivity analysis confirmed that CBCT was not superior to panoramic imaging in avoiding neurosensoric disturbances.

CONCLUSIONS

The use of CBCT before removal of the mandibular third molar does not seem to reduce the number of neurosensoric disturbances.

Coronectomy of Deeply Impacted Lower Third Molar: Incidence of Outcomes and Complications after One Year Follow-Up

Objectives

The purpose of present study was to assess the surgical management of impacted third molar with proximity to the inferior alveolar nerve and complications associated with coronectomy in a series of patients undergoing third molar surgery.

Material and Methods

The position of the mandibular canal in relation to the mandibular third molar region and mandibular foramen in the front part of the mandible (i.e., third molar in close proximity to the inferior alveolar nerve [IAN] or not) was identified on panoramic radiographs of patients scheduled for third molar extraction.

Results

Close proximity to the IAN was observed in 64 patients (35 females, 29 males) with an impacted mandibular third molar. Coronectomy was performed in these patients. The most common complication was tooth migration away from the mandibular canal (n = 14), followed by root exposure (n = 5). Re-operation to remove the root was performed in cases with periapical infection and root exposure.

Conclusions

The results indicate that coronectomy can be considered a reasonable and safe treatment alternative for patients who demonstrate elevated risk for injury to the inferior alveolar nerve with removal of the third molars. Coronectomy did not increase the incidence of damage to the inferior alveolar nerve and would be safer than complete extraction in situations in which the root of the mandibular third molar overlaps or is in close proximity to the mandibular canal.