Iatrogenic injury to oral branches of the trigeminal nerve: records of 449 cases

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

Objectives

The purpose of this study was to systematically review the comprehensive overview of literature data about injury to the inferior alveolar nerve after lower third molar extraction to discover the prevalence of injury, the risk factors, recovery rates, and alternative methods of treatment.

Material and Methods

Literature was selected through a search of PubMed electronic databases. Articles from January 2009 to June 2014 were searched. English language articles with a minimum of 6 months patient follow-up and injury analysis by patient’s reporting, radiographic, and neurosensory testing were selected.

Results

In total, 84 literature sources were reviewed, and 14 of the most relevant articles that are suitable to the criteria were selected. Articles were analyzed on men and women. The influence of lower third molar extraction (especially impacted) on the inferior alveolar nerve was clearly seen.

Conclusions

The incidence of injury to the inferior alveolar nerve after lower third molar extraction was about 0.35 - 8.4%. The injury of the inferior alveolar nerve can be predicted by various radiological signs. There are few risk factors that may increase the risk of injury to the nerve such as patients over the age of 24 years old, with horizontal impactions, and extraction by trainee surgeons. Recovery is preferable and permanent injury is very rare.

Endoscopic-assisted infraorbital nerve release

Endoscopic-assisted techniques in plastic and craniofacial surgeries are limited. We present a patient with infraorbital nerve entrapment following traumatic facial injury that failed conservative management. Compression of the nerve was treated with an endoscopic-assisted nerve release of the surrounding soft tissue with a circumferential foraminal osteotomy.

The Inferior Alveolar Nerve of the Horse: Course and Anatomical Relationship with Mandibular Cheek Teeth

The precise location of neurovascular structures within the relatively long mandibular canal of the horse is of paramount importance in surgical procedures of the area. The inferior alveolar nerve (IAN) enters the mandibular canal on the medial (lingual) surface of the mandible and innervates all the mandibular teeth. During its course, the nerve moves laterally, crossing the roots of the inferior cheek teeth. However, the exact anatomical relationships occurring between the IAN and the roots of the equine mandibular cheek teeth have not been described in detail. In this study, the mandibles of 40 horses were examined with CT scans and then used for bilateral detailed anatomical dissection, to assess the path of the IAN and its relationship to the roots of the lower cheek teeth. The data obtained show that the equine IAN is located ventral to the apices of the molar teeth (311/411, 310/410, 309/409 according to the Triadan numerical system). At the level of PM(4) (308/408), the IAN is located on the lingual side of the roots and coronally to its apices. At the level of PM(3) (307/407), the IAN is then found on the lingual side of the roots but in proximity to the apices. In 2 of 40 horses (=5%), the IAN moves towards the lingual side between the mesial and the distal root of PM(4). Our observations are valuable for planning a surgical approach to the ventral side of the mandible in the horse and to avoid potential post-operative complications.

Panoramic radiography and cone-beam computed tomography findings in preoperative examination of impacted mandibular third molars

BACKGROUND

Preoperative radiographic examination of impacted mandibular third molars (IMTM) is essential to prevent inferior alveolar nerve injury during extraction. The purpose of this study was to evaluate the correlation between cone-beam computed tomography (CBCT) and digital panoramic radiography (DPR) findings in preoperative examination of IMTM.

METHODS

This retrospective study included 298 teeth in 191 individuals. The relationship between the inferior alveolar canal (IAC) and the IMTM (buccal, lingual, interradicular or inferior), the position of the IMTM with respect to the IAC (contact, no contact), the morphologic shape of the mandible in the IMTM region (round, lingual extended, lingual concave), the type of IMTM (vertical, horizontal or angular) and the number of roots of the IMTM were evaluated on CBCT images. DPR images were evaluated for the number of roots of the IMTM and for the most common radiographic findings indicating a relationship between the IAC and the IMTM (darkening of the roots, diversion of the IAC, narrowing of the IAC and interruption of the white line). Data were statistically analyzed with Cramer V coefficient, Kappa statistic, chi-square and Fisher's exact test.

RESULTS

There was a significant difference in number of roots detected on DPR versus CBCT images. There was a significant association between the type of IMTM and the morphologic shape of the mandible on CBCT images. Darkening of the roots and interruption of the white line on DPR images were significantly associated with the presence of contact between the IMTM and the IAC on CBCT images.

CONCLUSIONS

Panoramic radiography is inadequate, whereas CBCT is useful to detect multiple roots of IMTM. When darkening of the roots and interruption of the white line are observed on panoramic images, there is increased likelihood of contact between the IMTM and the IAC. CBCT is required in these cases.

Low risk of neurosensory dysfunction after mandibular third molar surgery in patients less than 30 years of age. A prospective study following removal of 1220 mandibular third molars

OBJECTIVE

The study aims were to estimate the prevalence of neurosensory dysfunction (NSD) and identify risk factors for NSD after mandibular third molar (M3) removal.

STUDY DESIGN

In this prospective cohort study 864 patients had their M3 removed. Age, gender, surgeon's experience, and radiographic findings were recorded and the outcome variables were NSD and data analyses.

RESULTS

In 884 patients, 1220 M3 were removed. Fourteen patients reported NSD postoperatively; 10 inferior alveolar nerve (IAN) injury, 3 lingual nerve (LN) and 1 had injury to both. After 5 years the number of patients with NSD of the IAN had decreased to 5, but no change in the LN.

CONCLUSION

Age and cortical line interruption were significantly associated with the risk of developing sensory dysfunction. All patients younger than 30, and 3 of 8 patients older than 30, had full recovery of the IAN injury. NSD of the LN persisted in all patients.

Conservative surgical and microsurgical techniques for the management of dental implants that impinge on the inferior alveolar nerve

Loss of sensation in the lip after insertion of an implant is annoying. The aim of this paper was to describe two techniques for management of osseointegrated dental implants that impinge on the mandibular nerve, the purpose of which is to improve sensation without unscrewing the dental implant.

Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population

OBJECTIVE

To study the correlation between the position of the inferior dental (ID) nerve canal and the angulation of impacted mandibular third molars using dental cone beam computed tomography (CBCT).

MATERIALS AND METHODS

The study considered 100 impactions in 85 patients (60 males, 25 females), for whom an initial panoramic radiographic assessment had revealed that the ID canal and the lower 3rd molar were in close proximity. A CBCT scan of each patient was carried out to assess how the ID nerve canal position influenced the class and position of impaction, angulation of impaction, and bone contact.

RESULTS

Class I position B impactions were found in the majority of cases, where the position of the ID canal was approximate to the lingual plate and inferior to the 3rd molar (85.7%). The results were statistically significant (p = 0.001). 96% of the ID canals showed bone contact. Of these, 77.1% of ID canals exhibited lingual bone contact, inferior to impaction. The results were statistically significant (p = 0.001). Horizontally angulated impactions were most common in the mandible, and significantly associated with lingual and inferior positioning of the ID canal (76.2%).

CONCLUSIONS

Our sample population most commonly exhibited horizontally angulated class I position B impactions of the mandible. The position of the ID canal significantly influenced the type of impaction and bone contact.

Clinical outcome of conservative treatment of injured inferior alveolar nerve during dental implant placement

OBJECTIVES

Infererior alveolar nerve (IAN) damage may be one of the distressing complications occurring during implant placement. Because of nature of closed injury, a large proportion is approached non-invasively. The purpose of this study was to analyze the outcomes of conservative management of the injured nerve during dental implant procedure.

MATERIALS AND METHODS

Sixty-four patients of implant related IAN injury, who were managed by medication or observation from January 1997 to March 2007 at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, were retrospectively investigated. The objective tests and subjective evaluations were performed to evaluate the degree of damage and duration of sensory disturbance recovery. Tests were performed on the day of the first visit and every two months afterward. Patient's initial symptoms, proximity of the implant to the IAN, time interval between implant surgery and the first visit to our clinic, and treatment after implant surgery were analyzed to determine whether these factors affected the final outcomes.

RESULTS

Among the 64 patients, 23 had a chief complaint of sensory disturbance and others with dysesthesia. The mean time until first visit to our hospital after the injury was 10.9 months.One year after nerve injury, the sensation was improved in 9 patients, whereas not improved in 38 patients, even 4 patients experienced deterioration. Better prognosis was observed in the group of patients with early visits and with implants placed or managed not too close to the IAN.

CONCLUSION

Nearly 70% of patients with IAN injury during implant placement showed no improvement in sensation or dysesthesia with the conservative management. Earlier decision for active treatment needs to be considered because of possibility of deterioration of symptoms and unsatisfactory recovery.

Postprocedural inflammatory inferior alveolar neuropathy: an important differential diagnosis

Lingual or inferior alveolar nerve (IAN) injury after dental procedures may result from direct trauma or local anesthetic agent and presents with immediate onset of typically nonprogressive symptoms, including pain and sensory changes. We report a case of delayed-onset pain and progressive sensory symptoms after IAN block for amalgam restoration. A 54-year-old man presented with progressive right-sided facial pain 48 hours after IAN block for amalgam restoration, followed 1 week later by hypoesthesia and allodynia in IAN distribution. The presentation is more consistent with inflammatory neuropathy, as is well recognized in brachial plexopathy. Imaging was used to exclude local and central causes, following which the clinical diagnosis was made. Inflammatory neuropathies may be distinguished from iatrogenic causes on the basis of delayed symptom onset, early severe pain, and progressive sensory symptoms. Awareness of this condition is important, because early steroid therapy followed by medications for neuropathic pain may provide benefit.

Evaluation of trigeminal nerve injuries in relation to third molar surgery in a prospective patient cohort. Recommendations for prevention

Trigeminal nerve injury is the most problematic consequence of dental surgical procedures with major medico-legal implications. This study reports the signs and symptoms that are the features of trigeminal nerve injuries caused by mandibular third molar (M3M) surgery. 120 patients with nerve injury following M3M surgery were assessed. All data were analysed using the SPSS statistical programme and Microsoft Excel. 53 (44.2%) inferior alveolar nerve (IAN) injury cases and 67 (55.8%) lingual nerve injury (LNI) cases were caused by third molar surgery (TMS). Neuropathy was demonstrable in all patients with varying degrees of paraesthesia, dysaesthesia (in the form of burning pain), allodynia and hyperalgesia. Pain was one of the presenting signs and symptoms in 70% of all cases. Significantly more females had IAN injuries and LNIs (p<0.05). The mean ages of the two groups of patients were similar. Speech and eating were significantly more problematic for patients with LNIs. In conclusion, chronic pain is often a symptom after TMS-related nerve injury, resulting in significant functional problems. Better dissemination of good practice in TMS will significantly minimize these complex nerve injuries and prevent unnecessary suffering.

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.

Minimising and managing nerve injuries in dental surgical procedures

The most significant complications from dental surgical interventions are iatrogenic trigeminal nerve injuries, which can result in permanent altered sensation and pain, causing considerable functional and psychological disability. This paper provides some useful tips on minimising the risks of these injuries. By understanding the risk factors and modifying the resulting intervention, more of these injuries may be prevented.

Necessity of 3D visualization for the removal of lower wisdom teeth: required sample size to prove non-inferiority of panoramic radiography compared to CBCT

The availability of cone beam computed tomography (CBCT) and the numbers of CBCT scans rise constantly, increasing the radiation burden to the patient. A growing discussion is noticeable if a CBCT scan prior to the surgical removal of wisdom teeth may be indicated. We aimed to confirm non-inferiority with respect to damage of the inferior alveolar nerve in patients diagnosed by panoramic radiography compared to CBCT in a prospective randomized controlled multicentre trial. Sample size (number of required third molar removals) was calculated for the study and control groups as 183,474 comparing temporary and 649,036 comparing permanent neurosensory disturbances of the inferior alveolar nerve. Modifying parameter values resulted in sample sizes ranging from 39,584 to 245,724 respectively 140,024 to 869,250. To conduct a clinical study to prove a potential benefit from CBCT scans prior to surgical removal of lower wisdom teeth with respect to the most important parameter, i.e., nerval damage, is almost impossible due to the very large sample sizes required. This fact vice versa indicates that CBCT scans should only be performed in high risk wisdom tooth removals.

Risk factors of neurosensory deficits in lower third molar surgery: an literature review of prospective studies

This literature review assessed the risk factors linked to inferior dental nerve (IDN) and lingual nerve (LN) deficits following lower wisdom tooth surgery. A computer search of several databases with specified key words was performed. 32 articles were selected; the risk factors for IDN deficit were reported in 4 articles, LN in 9 and both IDN and LN in 19. Data were analysed statistically to evaluate the potential risk factors. Literature review showed specific radiographic signs and intra-operative IDN exposure increased the risk of IDN deficit. Raising the lingual flap significantly increased the risk of LN deficit. Unerupted tooth and lingual split technique increased IDN and LN deficit risks significantly. Age was linked to IDN and LN deficits, and deep impaction was related to IDN deficit, but no statistical tests were performed on these two risk factors owing to the heterogeneity of data from the studies. This literature review found increased age, unerupted tooth, deep impaction, specific radiographic signs, intra-operative IDN exposure and lingual split technique were risk factors for IDN deficit; increased age, unerupted tooth, distal impaction, raising of lingual flap and lingual split technique were risks factors for LN deficit in lower wisdom tooth surgery.

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.

Interindividual differences in the perception of dental stimulation and related brain activity

For identical diagnoses in the trigeminal innervation territory, individual differences have been clinically observed among the symptoms reported, such as dysesthesia and pain. Different subjective perceptions of unpleasantness and pain intensity may have different cortical substrates. The aim of this study was to identify brain areas in which activation depends on the subjective perception (intensity and unpleasantness) of electric dental stimulation. Electrical stimuli of increasing intensity were applied to maxillary canines in 14 healthy volunteers. Ratings for stimulus intensity and unpleasantness perceived across the stimulation session were reported postscan on 11-point numerical scales. The rating values were then included as covariates in the functional magnetic resonance imaging (fMRI) group analysis. Interindividual differences of intensity ratings were reflected in differential activity of the following brain areas: superior parietal lobule, superior temporal gyrus/anterior insula, inferior and middle temporal gyrus, lingual gyrus, anterior cingulate, and caudate nucleus. Differences related to unpleasantness ratings were reflected in the lingual gyrus. In conclusion, differences of perceived intensity between individuals are reflected in the differential activity of a set of brain areas distinct from those regions, reflecting rating differences of unpleasantness.

Lingual nerve injury in third molar surgery

The aim of this study was to investigate the healing potential of damaged lingual nerves with some remaining function at least 3 months post injury. Forty-six patients were monitored at different time intervals after injury. A simple neurosensory examination included the perception of tactile, thermal stimuli and location of stimulus, as well as two-point discrimination, pain and the presence of a neuroma at the lesion site. Neurogenic signs and symptoms related to the injury and their variation over time were registered. Females were more often referred than males. Most lingual nerve injuries exhibited a significant potential for recovery, but only a few patients made a full recovery with absence of neurogenic symptoms. The recovery rate was highest during the first 6 months. Recovery was not influenced by gender, and only slightly by age. The presence of a neuroma was associated with a more severe injury. Patients should be monitored repeatedly for at least 3 months, and not operated on until neurosensory function no longer improves, and is less than what might be rendered by microsurgical repair. Through proper training and mastery of the surgical approach, every effort should be focused on sparing the lingual nerve, considering its proximity to the field of surgery.