Current management of damage to the inferior alveolar and lingual nerves as a result of removal of third molars

Application of Tinel's test combed with clinical neurosensory test distinguishes spontaneous healing of lingual nerve neuropathy after mandibular third molar extraction

BACKGROUND

Extraction of the mandibular third molar, the most frequent and important surgical procedure in the clinical practice of oral surgery, is associated with the risk of injury of the lingual nerve. Neuropathy of the lingual nerve poses diagnostic challenges regarding the transient or permanent nature of the injury. No consensus or criteria have been established regarding the diagnosis of lingual nerve neuropathy. We applied both Tinel's test and clinical neurosensory testing together, which can be easily used at the bedside in the early stages of injury. Therefore, we propose a new method to differentiate between lesions with the ability to heal spontaneously and those that cannot heal without surgery.

RESULTS

Thirty-three patients (29 women,  4 men; mean age, 35.5 years) were included in this study. For all patients, the median interval between nerve injury and initial examination was 1.6 months and that between nerve injury and the second examination before determining the need for surgical management was 4.5 months. The patients were assigned to either group A or B. The spontaneous healing group (group A, n = 10) revealed a tendency for recovery within 6 months after tooth extraction. In this group, although there were individual differences in the degree of recovery, a remarkable tendency for recovery was observed based on clinical neurosensory testing in all cases. None of the patients were diagnosed with allodynia. In seven cases, the Tinel test result was negative at the first inspection, and in three cases, the result changed to negative at the second inspection. Conversely, in group B(n = 23), no recovery trend was observed with regard to clinical neurosensory testing, and nine patients had allodynia. Further, the Tinel test result was positive for all patients in both examinations.

CONCLUSIONS

Our findings indicate that in case of transient lingual nerve paralysis, clinical neurosensory testing findings deteriorate immediately after tooth extraction and gradually recover, while Tinel's test shows a negative result. Using Tinel's test and clinical neurosensory testing together enabled early and easy identification of the severity of the lingual nerve disorder and of lesions that would heal spontaneously without surgical management.

Early lingual nerve suture under local anesthesia after wisdom tooth extraction: a case report

Introduction: Lingual nerve injury is one of the operative risks of mandibular wisdom tooth avulsion surgery. The anatomical relationship of the nerve to the medial side of the socket of the mandibular third molar must be known when performing the procedure. When a lesion occurs, the diagnosis may be delayed by the effect of anesthesia. In the case of a complete section, repair can be considered by direct suture of the nerve margins. It is recommended to perform this suture as soon as possible. In most cases, the lingual nerve suture is performed remotely and under general anesthesia. Observation: The case presented here describes the early repair of a lingual nerve transection after avulsion of a mandibular third molar. The procedure has been performed under local anesthesia one day after surgery and consisted of a direct suture using the previous surgical approach. Conclusion: This allows for a simplified treatment of this complication, thus shortening the management time.

Post-traumatic Trigeminal Neuropathic Pain: Factors Affecting Surgical Treatment Outcomes

Post-traumatic trigeminal neuropathic pain (PTTNp) is a painful condition that may result from injury to the sensory division of the trigeminal nerve. Treatment of this condition is challenging and consensus on treatment to resolve neuropathic pain has yet to be standardized. Equally as challenging is the identification of surgical outcome variables to guide surgical treatment of PTTNp. This is partly due to the variability in pain characteristics, severity of nerve injury, location, and duration from injury to surgery. In those with neuropathic pain prior to microsurgical intervention, the incidence of neuropathic pain after microsurgical intervention is 67%. It is unclear why nerve repair surgery is effective in resolving or decreasing neuropathic pain in some patients, whereas it has no effect on pain relief in others. Psychological, medical, and age-related factors have been identified as risk factors for developing chronic post-surgical pain due to post-traumatic neuropathic pain. Two factors: injury to surgery time and preoperative visual analog scale score have recently been identified as variables that influence surgical outcomes in the treatment of PTTNp.

Collagenase Administration into Periodontal Ligament Reduces the Forces Required for Tooth Extraction in an Ex situ Porcine Jaw Model

Minimally invasive exodontia is among the long-sought-for development aims of safe dental medicine. In this paper, we aim, for the first time, to examine whether the enzymatic disruption of the periodontal ligament fibers reduces the force required for tooth extraction. To this end, recombinantly expressed clostridial collagenase G variant purified from Escherichia coli was injected into the periodontal ligament of mesial and distal roots of the first and second split porcine mandibular premolars. The vehicle solution was injected into the corresponding roots on the contralateral side. Following sixteen hours, the treated mandibles were mounted on a loading machine to measure the extraction force. In addition, the effect of the enzyme on the viability of different cell types was evaluated. An average reduction of 20% in the applied force (albeit with a large variability of 50 to 370 newton) was observed for the enzymatically treated roots, reaching up to 50% reduction in some cases. Importantly, the enzyme showed only a minor and transient effect on cellular viability, without any signs of toxicity. Using an innovative model enabling the analytical measurement of extraction forces, we show, for the first time, that the enzymatic disruption of periodontal ligament fibers substantially reduces the force required for tooth extraction. This novel technique brings us closer to atraumatic exodontia, potentially reducing intra- and post-operative complications and facilitating subsequent implant placement. The development of novel enzymes with enhanced activity may further simplify the tooth extraction process and present additional clinical relevance for the broad range of implications in the oral cavity.

Comparison of prognosis in two methods for the lingual nerve repair: direct suture with vein graft cuff and collagen allograft method

Background

No studies have compared the outcomes of direct perineurial suture with vein graft cuff repair and indirect collagen allograft repair of the lingual nerve following an injury. Therefore, we evaluated and compared the outcomes of each over a 1-year observation period. We retrospectively assessed 20 patients who had undergone microneurosurgical repair of unilateral lingual nerve injuries at the Wakayama Medical University Hospital between May 2015 and March 2019. We utilized two different methods for lingual nerve repair, i.e., direct perineurial repair with a vein graft cuff and interpositional collagen allograft repair. Sensory and taste function in the lingual nerve were preoperatively evaluated using a static two-point discrimination test, superficial pain/tactile sensation test, tests for the pressure pain threshold (Semmens-Weinstein monofilament), test for thermal discrimination hot and cold sensation, and a taste discrimination test. These tests were performed again at 6 and 12 months postoperatively.

Results

Compared to the preoperative conditions, all patients showed improved sensory reactions. Functional sensory recovery outcomes were defined by Pogrel’s criteria, Medical Research Council Scale grades, and functional sensory recovery. In each group, all patients improved after the operation. However, the operation time was significantly shorter for an interpositional collagen allograft repair as compared to that for a direct perineurial repair with a vein graft cuff.

Conclusions

There were no statistically significant differences between the two repair Methods, except for the operation time. Both methods led to satisfactory results for all criteria. From an economic point of view, direct perineurial repair with a vein graft cuff is meaningful; however, the esthetic effect on the donor site should be considered. Conversely, interpositional collagen allograft repair has the advantage of a greatly shortened operation time.

Anatomical Position of Lower Third Molar in Relation to Mandibular Canal on Cone-Beam Computed Tomography Images in A Tertiary Care Hospital: A Descriptive Cross-sectional Study

INTRODUCTION

The positional relationship between the mandibularcanal with impacted mandibular third molar is the main factor of inferior alveolar nerve injury. The purpose of this study wasto classify the anatomical three dimensional relationship between the proximity of impacted mandibular third molars to the inferior alveolar canal.

METHODS

The descriptive cross-sectional study was conducted inthe Department of Oral and Maxillofacial Surgery of a tertiary care hospital from July 2020 to August 2020 after obtaining ethical approval from the Institutional Review Committee (Reference number 2506202001). Cone-beam computed tomography images of 200 patient's mandibular third molars were used. A convenient sampling method was used. Data were analyzed using Statistical package for the Social Sciences.

RESULTS

Mandibular canal relative to the roots of the mandibular third molar was observed on the apical side in 104 (52.0%) and 173 (86.5%) third molars had direct contact with the mandibular canal. About 36 (97.3%) lingually placed mandibular third molars had contact with the mandibular canal.

CONCLUSIONS

The findings of the study conclude that most of the mandibular third molars situated lingually had a higher occurrence of mandibular nerve involvement. The anatomic structures of the mandibular third molar and the mandibular canal may be helpful to draw upon the adequate surgical plan to avoidor reduce nerve involvement.

Outcomes of Direct Lingual Nerve Repair After an Injury: A Systematic Review

PURPOSE

The purpose of this study was to conduct a systematic review with meta-analysis to investigate the outcomes of direct lingual nerve repair after injury.

MATERIALS AND METHODS

The studies in this review were compiled by using PubMed/Medline and ScienceDirect, which were searched by a single reviewer (M.K.) from their inception until March 10, 2020. Two independent reviewers (M.K. and V.B.Z.) who were blinded to each other's assessments reviewed full-text articles to assess for study inclusion. Outcomes were dichotomized as either functional sensory recovery (FSR) or no FSR. Clinical testing must have been assessed at a minimum of 6 months postoperatively. FSR was defined as grade S3, S3⁺, or S4 on the British Medical Research Council scale of neurosensory function. Studies were only eligible if they provided the number of patients treated with conduits or time from injury to repair and the associated rates of FSR with each intervention.

RESULTS

The initial search using the key terms yielded 4,921 results, which was then eventually filtered down to 6 articles after multiple levels of appraisal. Five articles were retrospective cohort studies and 1 was a randomized controlled study. Four of the 6 studies reported an FSR of grade S3 or higher in 85% or more of the patients. Conduit use was not associated with a significantly greater likelihood of achieving FSR (pooled risk ratio = 1.10; 95% confidence interval, 0.96 to 1.27; P = .17). Repair within 6 months was associated with significantly improved likelihood of achieving FSR (pooled risk ratio = 0.84; 95% confidence interval, 0.71 to 0.99; P = .04).

CONCLUSIONS

The use of conduits during repair was not associated with clinically significant increased FSR. Early repair was associated with a beneficial effect on FSR; however, heterogeneity was an issue with the studies. There is a lack of strong evidence owing to the nature of studies analyzed and the need for further research is required.

Correlation of miRNA expression with intensity of neuropathic pain in man

Background

Peripheral nerve injury causes changes in expression of multiple receptors and mediators that participate in pain processing. We investigated the expression of microRNAs (miRNAs) – a class of post-transcriptional regulators involved in many physiological and pathophysiological processes – and their potential role in the development or maintenance of chronic neuropathic pain following lingual nerve injury in human and rat.

Methods

We profiled miRNA expression in Sprague-Dawley rat and human lingual nerve neuromas using TaqMan® low-density array cards. Expression of miRNAs of interest was validated via specific probes and correlated with nerve injury-related behavioural change in rat (time spent drinking) and clinical pain (visual analogue scale (VAS) score). Target prediction was performed using publicly available algorithms; gene enrichment and pathway analysis were conducted with MetaCore. Networks of miRNAs and putative target genes were created with Cytoscape; interaction of miRNAs and target genomes in rat and human was displayed graphically using CircosPlot.

Results

rno-miR-138 was upregulated in lingual nerve of injured rats versus sham controls. rno-miR-138 and rno-miR-667 expression correlated with behavioural change at day 3 post-injury (with negative (rno-miR-138) and positive (rno-miR-667) correlations between expression and time spent drinking). In human, hsa-miR-29a was downregulated in lingual nerve neuromas of patients with higher pain VAS scores (painful group) versus patients with lower pain VAS scores (non-painful). A statistically significant negative correlation was observed between expression of both hsa-miR-29a and hsa-miR-500a, and pain VAS score.

Conclusions

Our results show that following lingual nerve injury, there are highly significant correlations between abundance of specific miRNAs, altered behaviour and pain scores. This study provides the first demonstration of correlations between human miRNA levels and VAS scores for neuropathic pain and suggests a potential contribution of specific miRNAs to the development of chronic pain following lingual nerve injury. Putative targets for candidate miRNAs include genes related to interleukin and chemokine receptors and potassium channels.

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.

Comparison of two incisions for open reduction and internal fixation of mandibular body fractures: A randomised controlled clinical trial evaluating the surgical outcome

PURPOSE

The purpose of the study is to compare the surgical access and post-operative outcome of two intra-oral incisions used for approaching a mandibular body fracture.

METHODS

This clinical trial involved 60 patients with mandibular body fractures who were randomly allocated to control and study groups. The fractures were approached using the routine vestibular incision in the control group and crevicular incision with vertical release in the study group. The effects of incision design on the post-surgical outcome variables like swelling, trismus, paresthesia, wound healing and gingival recession were statistically analysed with non-parametric tests by using SPSS 22.0 software. Comparison of continuous variables between the groups and time points was done using Mann Whitney test and Friedman test respectively. Chi-square test was used to compare proportions between groups. Dunn's test with Bonferroni correction was used for pair wise comparisons.

RESULTS

The study group demonstrated favourable surgical outcome in the immediate postoperative phase as compared to the control group. The difference in mouth opening, swelling and neurosensory impairment between the two groups was found to be statistically significant (p < 0.05).

CONCLUSION

Crevicular incision was found to be an ideal alternative to vestibular incision in achieving surgical access and fixation of mandibular body fractures with reduction in postoperative patient discomfort and better surgical outcome.

Comparison of Subjective and Objective Assessments of Neurosensory Function after Lingual Nerve Repair

OBJECTIVE

Mandibular third molar extractions are important in oral maxillofacial surgery. Damage to the lingual nerves, although rare, is a possible complication. There are reports of postoperative recovery after lingual nerve repair, but few reports have compared subjective and objective assessments of neurosensory function. Therefore, this study aims to compare subjective and objective assessments of neurosensory function after lingual nerve repair.

SUBJECTS AND METHODS

This retrospective cohort study comprised 52 patients with lingual nerve anesthesia after third molar extraction at the Department of Oral and Maxillofacial Surgery, Wakayama Medical University Hospital, Wakayama, Japan, between December 2008 and December 2015. We recorded pre- and postoperative (6 months and 12 months) neurosensory examinations.

RESULTS

Patient's subjective assessments of neurosensory function suggested improvement between the preoperative period and 12 months postoperation, although this difference was not significant. Objective assessment based on examination and testing, on the other hand, showed a significant difference in improvement (p < 0.05).

CONCLUSIONS

There was no evidence that improvement of subjective preoperative and postoperative assessments was significantly associated with improvement of objective neurosensory assessments after lingual nerve repair. Overall physical condition and background were thought to affect subjective evaluation. Subjective assessment is important in conjunction with objective evaluation because it may reveal dysesthesia that would otherwise be missed. In the future, we will examine those cases in whom subjective assessments showed no improvement although objective assessments showed improvement.

Biomechanical evaluation of two plating configurations for fixation of a simple transverse caudal mandibular fracture model in cats

OBJECTIVE To evaluate biomechanical properties of intact feline mandibles, compared with those for mandibles with an experimentally created osteotomy that was stabilized with 1 of 2 internal fixation configurations. SAMPLE 20 mandibles from 10 adult feline cadavers. PROCEDURES An incomplete block study design was used to assign the mandibles of each cadaver to 2 of 3 groups (locking plate with locking screws [locking construct], locking plate with nonlocking screws [nonlocking construct], or intact). Within each cadaver, mandibles were randomly assigned to the assigned treatments. For mandibles assigned to the locking and nonlocking constructs, a simple transverse osteotomy was created caudal to the mandibular first molar tooth after plate application. All mandibles were loaded in cantilever bending in a single-load-to-failure test while simultaneously recording load and actuator displacement. Mode of failure (bone or plate failure) was recorded, and radiographic evidence of tooth root and mandibular canal damage was evaluated. Mechanical properties were compared among the 3 groups. RESULTS Stiffness, bending moments, and most post-yield energies for mandibles with the locking and nonlocking constructs were significantly lower than those for intact mandibles. Peak bending moment and stiffness for mandibles with the locking construct were significantly greater than those for mandibles with the nonlocking construct. Mode of failure and frequency of screw damage to tooth roots and the mandibular canal did not differ between the locking and nonlocking constructs. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that both fixation constructs were mechanically inferior to intact mandibles. The locking construct was mechanically stronger than the nonlocking construct.

Rat Nerve Regeneration with the Use of a Polymeric Membrane Loaded with NGF

Exogenous neurotrophic factors, delivered by various systems, are used to improve nerve regeneration. This study tested the effectiveness of a polymeric membrane loaded with Nerve Growth Factor (NGF) on mental nerve regeneration after a crush injury in rats. We tested NGF application, known to play a role in afferent fiber repair in dental neurobiology, to see if it could improve the regeneration. Afferent neurogram recordings and histological analyses of the trigeminal ganglion neurons were performed. One month after the crush injury, early regeneration was observed independently of exogenous NGF. However, as compared with the activity level recorded before the injury, the afferent activity was reduced by 28.5% without NGF, and the mean number of labeled neurons decreased. With NGF, activity was increased by 30.8%, with no significant histological difference compared with animals without lesions. NGF application through a polymeric membrane can influence degenerative and/or regenerative processes after a crush injury.

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.

Long-term outcome assessment of closed treatment of mandibular fractures

Mandibular fractures are among the most common trauma injuries of the craniomaxillofacial region. This study evaluated the late results of mandibles fractures treated with arch bar. Forty-nine patients were examined clinically and by questionnaires for late results of arch bar treatment. Demographic data (age, sex, etc), trigeminal nerve sensation (Weber test), temporomandibular joint evaluation, masticatory muscle function, and occlusion were recorded. The data were analyzed by χ test using Sigma Stat 2.0 software. Fifty-one percent of the patients with angular fractures complained of sensory disturbances. Condylar and angular fractures demonstrated higher levels of pain. According to Pearson χ test, a statistically significant relation between angular fracture and tenderness of the internal pterygoid muscles (P = 0.047), angular fracture and cross-bite (P = 0.021), parasymphysial fracture and pain upon wind blowing (P = 0.026), and body fracture and mastication discomfort (P = 0.038) was found. In closed reduction therapy, fracture location of the mandible seems to be more likely correlated in producing particular long-term complications. Regular follow-ups for functional treatments and physiotherapy of chewing muscles and temporomandibular joint, along with removal of occlusal abnormalities, should be considered following arch bar reduction of mandibular fractures.

Coronectomy versus surgical removal of the lower third molars with a high risk of injury to the inferior alveolar nerve. A bibliographical review

Background

Coronectomy is the surgical removal of the crown of the tooth deliberately leaving part of its roots. This is done with the hope of eliminating the pathology caused, and since the roots are still intact, the integrity of the inferior alveolar nerve is preserved.

Objectives

The aim is to carry out a systematic review in order to be able to provide results and conclusions with the greatest scientific evidence possible.

Material and Methods

A literature review is carried out through the following search engines: Pubmed MEDLINE, Scielo, Cochrane library and EMI. The level of evidence criteria from the Agency for Healthcare Research and Quality was applied, and the clinical trials’ level of quality was analyzed by means of the JADAD criteria.

Results

The following articles were obtained which represents a total of 17: 1 systematic review, 2 randomized clinical trials and 2 non-randomized clinical trials, 3 cohort studies, 2 retrospective studies, 3 case studies and 4 literature reviews.

Conclusions

Coronectomy is an adequate preventative technique in protecting the inferior alveolar nerve, which is an alternative to the conventional extraction of third molars, which unlike the former technique, presents a high risk of injury to the inferior alveolar nerve. However, there is a need for new clinical studies, with a greater number of samples and with a longer follow-up period in order to detect potential adverse effects of the retained roots.

Key words: Coronectomy, inferior alveolar nerve, nerve injury, wisdom tooth removal, paresthesia, and systematic review.

[Suture of lingual nerve: Technical note]

INTRODUCTION

Because of its anatomical position, the lingual nerve may be severed during oral surgical procedures, such as third molar removal. Early suturing of the nerve promotes better recovery. We describe the end-to-end suture of this nerve.

OPERATIVE PROCEDURE

The suture is carried-out under general anesthesia. The approach is made in the mouth floor, in the same way as for submandibular gland lithiasis transoral removal. This approach allows good exposure and some laxity to displace the nerve stumps. The latter can then be sutured under microscope assistance before closing the mucosa.

DISCUSSION

Lingual nerve suture is a simple, quick and inexpensive procedure. Unlike other procedures, it cannot be used in case of large loss of substance because of the small amount of laxity of the nerve. Nerve function recovery is better if performed before the 6th post-traumatic month, and in young patients.

Effect of local application of an antibody against brain-derived neurotrophic factor on neuroma formation after transection of the inferior alveolar nerve in the rat

This study aimed to examine the contributions of brain-derived neurotrophic factor (BDNF) at the injury site toward neuroma formation and nerve regeneration after inferior alveolar nerve transection. Histological analysis confirmed neuroma formation at 2 weeks after complete transection of the inferior alveolar nerve. A local administration of an antibody to BDNF inhibited connective tissue proliferation at the injury site and promoted nerve fiber integrity. Fluorogold labeling showed a significantly higher number of labeled cells in the trigeminal ganglion in the anti-BDNF-treated group compared with the vehicle control group. In-situ hybridization histochemistry showed intense signals for tropomyosin receptor kinase B mRNA in the area of the injury site containing fibrous or granular tissue in the anti-BDNF-treated group. In contrast, these signals were close to the detection limit in the area of the perineurium in intact nerve trunks, indicating that the signals were expressed by fibroblasts within the connective tissue. These findings suggest that antagonization of endogenous BDNF induced by nerve injury reduces neuroma formation, without inhibiting damaged axon regeneration.

Analysis and evaluation of relative positions of mandibular third molar and mandibular canal impacts

Objectives

This study used cone-beam computed tomography (CBCT) images to categorize the relationships between the mandibular canal and the roots and investigated the prevalence of nerve damage.

Materials and Methods

Through CBCT images, contact and three-dimensional positional relationships between the roots of the mandibular third molar and the mandibular canal were investigated. With this data, prevalence of nerve damage according to the presence of contact and three-dimensional positional relationships was studied. Other factors that affected the prevalence of nerve damage were also investigated.

Results

When the mandibular third molar and the mandibular canal were shown to have direct contact in CBCT images, the prevalence of nerve damage was higher than in other cases. Also, in cases where the mandibular canal was horizontally lingual to the mandibular third molar and the mandibular canal was vertically at the cervical level of the mandibular third molar, the prevalence of nerve damage was higher than in opposite cases. The percentage of mandibular canal contact with the roots of the mandibular third molar was higher when the mandibular canal was horizontally lingual to the mandibular third molar. Finally, the prevalence of nerve damage was higher when the diameter of the mandibular canal lumen suddenly decreased at the contact area between the mandibular canal and the roots, as shown in CBCT images.

Conclusion

The three-dimensional relationship of the mandibular third molar and the mandibular canal can help predict nerve damage and can guide patient expectations of the possibility and extent of nerve damage.

Visualization analysis of research frontiers and trends in nerve regeneration and osseoperception in the repair of tooth loss

This study analyzed 85 articles indexed by the Web of Science concerning nerve regeneration and osseoperception during tooth loss repair. Using the Web of Science database and Citespace III software, a document co-citation network map was drawn by document co-citation analysis and word frequency analysis methods. Combined with emergent node secondary literature retrieval, subject headings with apparent changing word frequency trends were retrieved so as to identify research frontiers and development trends. Research frontiers and hotspots for neuronal calcium sensor protein were quantitatively explored to forecast future research developments in nerve regeneration and osseoperception during repair of tooth loss.

Lingual nerve injury after third molar removal: Unilateral atrophy of fungiform papillae

BACKGROUND

Pain and sensory changes due to lingual nerve injury are one of the most common alterations that follow surgical removal of third molar. They are usually transient but other less common complications, such as the atrophy of fungiform papillae, have an uncertain prognosis.

CASE DESCRIPTION

We report a case of a 34-year-old woman who presented a unilateral lingual atrophy of fungiform papillae after third molar extraction accompanied by severe dysesthesia that altered her daily life significantly during the following months and how this complication evolved over time. We conducted a literature review on the different factors that can lead to a lingual nerve injury.

CLINICAL IMPLICATIONS

The clinical evolution of temporary and permanent somatosensitve injuries is an important fact to take into consideration during the postoperative management because it will indicate the lesion prognosis. Key words:Lingual nerve, third molar removal, somatosensitive alteration, papillae atrophy, permanent injury, temporary injury.

Correlation of Nav1.8 and Nav1.9 sodium channel expression with neuropathic pain in human subjects with lingual nerve neuromas

Background

Voltage-gated sodium channels Nav1.8 and Nav1.9 are expressed preferentially in small diameter sensory neurons, and are thought to play a role in the generation of ectopic activity in neuronal cell bodies and/or their axons following peripheral nerve injury. The expression of Nav1.8 and Nav1.9 has been quantified in human lingual nerves that have been previously injured inadvertently during lower third molar removal, and any correlation between the expression of these ion channels and the presence or absence of dysaesthesia investigated.

Results

Immunohistochemical processing and quantitative image analysis revealed that Nav1.8 and Nav1.9 were expressed in human lingual nerve neuromas from patients with or without symptoms of dysaesthesia. The level of Nav1.8 expression was significantly higher in patients reporting pain compared with no pain, and a significant positive correlation was observed between levels of Nav1.8 expression and VAS scores for the symptom of tingling. No significant differences were recorded in the level of expression of Nav1.9 between patients with or without pain.

Conclusions

These results demonstrate that Nav1.8 and Nav1.9 are present in human lingual nerve neuromas, with significant correlations between the level of expression of Nav1.8 and symptoms of pain. These data provide further evidence that changes in expression of Nav1.8 are important in the development and/or maintenance of nerve injury-induced pain, and suggest that Nav1.8 may be a potential therapeutic target.

An orthodontic technique for minimally invasive extraction of impacted lower third molar. J Oral Maxillofac Surg. 2013;71:1309-1317. [PMID: 23763903 DOI: 10.1016/j.joms.2013.03.025]

PURPOSE

To present a novel orthodontic approach for minimally invasive extraction of impacted mandibular third molars (M3s) close to the inferior alveolar nerve (IAN).

PATIENTS AND METHODS

Eight patients (8 M3s) requiring extraction of M3s were included in this study; there were 2 cases of horizontal impaction, 4 of mesioangular impaction, and 2 of vertical impaction. Cone-beam computed tomogram showed that the roots of impacted M3s in 2 cases interrupted the cortices of the mandibular canal, and those in the other 6 cases were very close to the IAN. Orthodontic treatment was performed in this study. The crowns of 5 impacted teeth were surgically exposed before the application of the orthodontic device, whereas bonding was performed directly to the occlusal surface of the other 3 M3s, which had partially erupted. The opposing maxillary M3s were removed in 3 cases. One-step orthodontic extraction was applied to vertically impacted M3s and 2-step treatment was applied to horizontally or mesioangularly impacted M3s. Success was defined as the separation of the impacted tooth from the IAN as visualized on cone-beam computed tomogram.

RESULTS

After orthodontic treatment, all impacted M3s were extruded and separated from the IAN (mean, 6.6 months; range, 4 to 10 months), without any neurologic consequences. The average time of extraction was 5 minutes. In all 8 cases, new bone formation occurred distal to the adjacent second molar.

CONCLUSION

This orthodontic technique may be a minimally invasive approach for the extraction of impacted M3s adjacent to the IAN, with a decreased risk of paresthesias and with osteoperiodontal advantages.

Lingual nerve deficit following mandibular third molar removal: review of the literature and medicolegal considerations. Oral Surg Oral Med Oral Pathol Oral Radiol. 2012;113:e10-e18. [PMID: 22669152 DOI: 10.1016/j.tripleo.2011.06.034]

The removal of mandibular third molars is probably the most frequently performed procedure in oral and maxillofacial surgery, and it is the most common surgical procedure associated with lingual nerve deficit. Lingual sensory impairment remains a clinical problem in oral and maxillofacial surgery and has serious medical and legal implications. In fact, damage to the lingual nerve is a common cause of litigation in dentistry. The purpose of this article was to review the literature about lingual nerve deficit following mandibular third molar removal and discuss the associated medicolegal aspects.

Pain Management for Nerve Injury following Dental Implant Surgery at Tokyo Dental College Hospital

By allowing reconstruction of compromised occlusion, dental implants contribute to an improvement in quality of life (QOL) and diet. Injury to a nerve during such treatment, however, can result in a sudden decline in QOL. And once a nerve has been injured, the chances of a full recovery are slim unless the damage is only slight. If such damage causes neuropathic pain severe enough to prevent sleep, the patient's QOL will deteriorate dramatically. While damage to skin tissue or bone invariably heals over time, damage to nerves does not, indicating the need to avoid such injury while performing implant insertion, for example. This means not relying solely on X-ray images, which can be rather unclear, but also using computed tomography to allow preoperative planning and intraoperative execution to be performed as accurately as possible. Moreover, if sensory damage does occur it is essential to avoid breaking the bond of trust between dentist and patient by giving false assurances of recovery. In such cases, appropriate measures must be taken promptly. This paper describes pain management for nerve injury following dental implant surgery at the Orofacial Pain Center of Tokyo Dental College Suidoubashi Hospital.

Treatment modalities of neurosensory deficit after lower third molar surgery: a systematic review

PURPOSE

To conduct a systematic review to answer the clinical question, "What are the available treatment modalities and their outcomes of neurosensory deficit after lower third molar surgery?"

MATERIALS AND METHODS

A systematic search, including a computer search of several databases with specific keywords, a reference search, and a manual search of 3 key maxillofacial journals were performed. Relevant articles were then evaluated and those that fulfilled the 6 predetermined criteria were chosen to enter the final review. The various treatment modalities and their outcomes of neurosensory deficit after lower third molar surgery, in the selected studies in the final review, were analyzed.

RESULTS

Ten articles entered the final review. Six treatment modalities of lingual nerve or inferior alveolar nerve deficit after lower third molar surgery were identified. External neurolysis, direct suturing, autogenous vein graft, and a Gore-Tex tube as a conduit were the 4 surgical treatments. Significant improvement after surgical treatment ranged from 25% to 66.7%. Acupuncture and low-level laser therapy were 2 available nonsurgical treatment modalities that were found to have produced significant improvement in sensation after treatment in more than 50% of subjects. There was insufficient information to determine the best timing of treatment of nerve injury after third molar surgery.

CONCLUSIONS

Four surgical treatments and 2 nonsurgical treatments were identified in the management of neurosensory disturbance after lower third molar surgery. Most treatments showed an improvement in sensation but the outcomes were variable. Complete recovery was uncommon in all kinds of available treatments.

The effect of a monoclonal antibody to calcitonin-gene related peptide (CGRP) on injury-induced ectopic discharge following lingual nerve injury

The development of ectopic neural discharge at a site of peripheral nerve injury is thought to contribute to the initiation of sensory disturbances and pain. We have previously shown that this discharge can be initiated or increased by the neuropeptide calcitonin gene-related peptide (CGRP). We have now studied a potential therapeutic approach to reducing the discharge by evaluating the effect of a systemically administered monoclonal antibody to CGRP on injury-induced activity in the lingual nerve. In 16 anaesthetised adult ferrets the left lingual nerve was sectioned. One day after the injury, the animals received a subcutaneous injection of either a monoclonal antibody to CGRP or a vehicle control. Three days after the injury, under a second anaesthetic, single-unit electrophysiological recordings were made from central to the injury site (469 and 391 units were analysed in antibody and vehicle groups, respectively), and the proportion of units that were spontaneously active was determined. In the vehicle-treated animals 6.4 ± 2.7 [SEM]% of the units were spontaneously active, with conduction velocities of 8.8–40.8 m/s and discharge frequencies of 0.03–2.7 Hz. In the monoclonal antibody-treated animals 5.7 ± 2.0% of the units were spontaneously active, with conduction velocities of 13.9–38.8 m/s and discharge frequencies of 0.07–1.8 Hz. There was no significant difference between these two groups (for spontaneous activity and conduction velocity: p > 0.05, Student's t-test; for discharge frequency: p > 0.05, Mann–Whitney test), suggesting that the spontaneous activity initiated by a nerve injury cannot be modulated by administration of a monoclonal antibody to CGRP.

Pulsed radiofrequency modulation for lingual neuralgia

Pulsed radiofrequency modulation (PRM) is a minimally invasive procedure that has been used successfully to treat neuropathic pain. Its use to treat lingual neuralgia has not to our knowledge been described previously, and we report a case.

Orthodontic extrusion of the lower third molar with an orthodontic mini implant

Neurologic changes owing to damage to the inferior alveolar nerve (IAN) are the most serious complication of lower third molar (M3) extraction because of their close spatial relationship. We adopted the concept of regional orthodontic treatment and extrusion, using skeletal anchorage with an orthodontic mini implant. Two malformed M3s that were closely apposed to the IAN were extruded with the aid of 3 or 4 orthodontic brackets and a mini implant. Both of the M3s were extruded successfully. The patients experienced little discomfort with the orthodontic appliances and there was neither permanent neurologic damage nor fracture of the root fragments following subsequent M3 extraction. Orthodontic treatment using a miniscrew to separate the IAN and M3, or luxation of the M3 may be a good alternative treatment option for extrusion of a vertically impacted lower M3 with fragile roots.

Risk factors associated with injury to the inferior alveolar and lingual nerves following third molar surgery-revisited

OBJECTIVE

Earlier reports, including a preliminary study within our unit, have shown that the surgeon's experience is one of the most influential factors in determining the likelihood of both permanent inferior alveolar nerve (IAN) and lingual nerve (LN) paresthesia, following third molar surgery. The effect of this and other factors influencing such prevalence are assessed in this study.

STUDY DESIGN

This prospective study involved 3236 patients who underwent surgical removal of impacted third molars. Patients' demographics and radiological parameters were recorded along with the grade of the treating surgeon. The prevalence of inferior alveolar and lingual nerves paresthesia at 1 month, 6 months, and 18 to 24 months postoperatively were also traced.

RESULTS

At 1 month postoperatively, the incidence of IAN paresthesia was 1.5% and the LN was 1.8%. These figures decreased over time and 18 to 24 months postoperatively, the incidence of permanent dysfunction of the IAN was 0.6% and LN was 1.1%. With regard to inferior alveolar nerve paresthesia, risk factors included the patient's age (26-30 years), horizontally impacted teeth, close radiographic proximity to the inferior alveolar canal (IAC), and treatment by trainee surgeons. With regard to the lingual nerve, risk factors included male patients, distoangular impactions, close radiographic proximity to the IAC, and treatment by trainee surgeons.

CONCLUSION

One of the main risk factors of developing permanent sensory dysfunction in the distribution of these nerves is related to the surgical skills/experience of the operator. Other factors are associated with the type of impaction and the radiographic proximity of the tooth to the inferior alveolar nerve. Such long-term complications can affect the patient's quality of life; the impact on profession, education, and research is unknown.

The prognostic value of panoramic radiography of inferior alveolar nerve damage after mandibular third molar removal: retrospective study of 400 cases

OBJECTIVE

The aim of the study was to estimate the accuracy of panoramic radiographic signs predicting inferior alveolar nerve (IAN) paresthesia after lower third molar removal.

STUDY DESIGN

In a case-control study the sample was composed of 41 cases with postoperative IAN paresthesia and 359 control cases without it. The collected data included "classic" specific signs indicating a close spatial relationship between third molar root and inferior alveolar canal (IAC), root curvatures, and the extent of IAC-root tip overlap. Bivariate and multivariate logistic regression analyses were completed to estimate the association between radiographic findings and IAN paresthesia.

RESULTS

The multivariate logistic analysis identified 3 signs significantly associated with IAN paresthesia (P < .001): interruption of the superior cortex of the canal wall, diversion of the canal, and darkening of the root. The sensitivities and specificities ranged from 14.6% to 68.3% and from 85.5% to 96.9%, respectively. The positive predictive values, calculated to factor a 1.1% prevalence of paresthesia, ranged from 3.6% to 10.9%, whereas the negative predictive values >99%.

CONCLUSION

Panoramic radiography is an inadequate screening method for predicting IAN paresthesia after mandibular third molar removal.

TRPA1 expression in human lingual nerve neuromas in patients with and without symptoms of dysaesthesia

The TRPA1 receptor is a member of the ankyrin family and is found in both spinal and trigeminal neurones. There is evidence to suggest that this receptor may be a sensor of noxious thermal stimuli in normal animals. After nerve injury, TRPA1 shows increased expression in uninjured axons, and has been implicated in the development and maintenance of hyperalgesia. We examined expression of TRPA1 in lingual nerve neuromas and investigated any potential correlation with the presence or absence of symptoms of dysaesthesia. Thirteen neuroma-in-continuity specimens were obtained from patients undergoing repair of a lingual nerve that had previously been damaged during lower third molar removal. Visual analogue scales (VAS) were used to record the degree of pain, tingling and discomfort. Tissue was processed for indirect immunofluorescence and the percentage area of PGP 9.5-immunoreactive neuronal tissue also labelled for TRPA1 was quantified. No significant difference between levels of TRPA1 in neuromas from patients with or without symptoms of dysaesthesia and no relationship between TRPA1 expression and VAS scores for pain, tingling or discomfort were observed. TRPA1 expression and the time after initial injury that the specimen was obtained also showed no correlation. These data show that TRPA1 is expressed in lingual nerve neuromas, but, it appears that, at this site, TRPA1 does not play a principal role in the development of neuropathic pain.