Correlation of the radiological predictive factors of inferior alveolar nerve injury with cone beam computed tomography findings

Artificial intelligence in positioning between mandibular third molar and inferior alveolar nerve on panoramic radiography

Determining the exact positional relationship between mandibular third molar (M3) and inferior alveolar nerve (IAN) is important for surgical extractions. Panoramic radiography is the most common dental imaging test. The purposes of this study were to develop an artificial intelligence (AI) model to determine two positional relationships (true contact and bucco-lingual position) between M3 and IAN when they were overlapped in panoramic radiographs and compare its performance with that of oral and maxillofacial surgery (OMFS) specialists. A total of 571 panoramic images of M3 from 394 patients was used for this study. Among the images, 202 were classified as true contact, 246 as intimate, 61 as IAN buccal position, and 62 as IAN lingual position. A deep convolutional neural network model with ResNet-50 architecture was trained for each task. We randomly split the dataset into 75% for training and validation and 25% for testing. Model performance was superior in bucco-lingual position determination (accuracy 0.76, precision 0.83, recall 0.67, and F1 score 0.73) to true contact position determination (accuracy 0.63, precision 0.62, recall 0.63, and F1 score 0.61). AI exhibited much higher accuracy in both position determinations compared to OMFS specialists. In determining true contact position, OMFS specialists demonstrated an accuracy of 52.68% to 69.64%, while the AI showed an accuracy of 72.32%. In determining bucco-lingual position, OMFS specialists showed an accuracy of 32.26% to 48.39%, and the AI showed an accuracy of 80.65%. Moreover, Cohen’s kappa exhibited a substantial level of agreement for the AI (0.61) and poor agreements for OMFS specialists in bucco-lingual position determination. Determining the position relationship between M3 and IAN is possible using AI, especially in bucco-lingual positioning. The model could be used to support clinicians in the decision-making process for M3 treatment.

Hard Tissue Preservation and Recovery in Minimally Invasive Alveolar Surgery Using Three-Dimensional Printing Guide Plate

BACKGROUND

For completely impacted teeth, it is of great significance to locate teeth accurately, preserve hard tissue and recovering the height of alveolar ridge. This can be effectively solved by the digital three-dimensional printing guide technology.

METHODS

Ten patients with completely impacted tooth were selected in this experiment. After cone-beam computed tomography scan, the dicom formal computed tomography data was analyzed for three-dimensional reconstruction by mimics 17.0 software. Then determining the surgical plan and making surgical guide plate. Three-dimensional printing guide plate assisted piezosurgery was used to remove bone and extract impacted teeth. After that, the removed bone cap was back to the original position. Cone-beam computed tomography was used for each operated patients after 1 week and 6 months.

RESULT

The surgical guide plates can locate teeth accurately and the surgery time was reduced for all patients. A week later, all patients healed well and removed the stitches on time. Cone-beam computed tomography showed that the retention of bone caps was good and there was no displacement. All patients showed a normal parameter of pain. Six months later, cone-beam computed tomography showed good bone formation in the extraction area, which filled with new bones completely. The recovery of bone outline and height of alveolar crest at the surgical site were basically consistent with those before the operation.

CONCLUSIONS

Three-dimensional printing guide plates combining with fenestration and bone-cap restoration can locate impacted teeth accurately, reduce the extraction volume of bone, shorten surgery time, and alleviate complications. This was conducive to preserve and restore hard tissue and had great prospective.

Novel strategy to predict high risk of inferior alveolar nerve injury during extraction of lower third molars based on assessment of computed tomographic images of multiple anatomical features

Preoperative assessment is essential to prevent inferior alveolar nerve (IAN) injury during surgical extraction of the lower third molar (LM3). Here, we aimed to establish an assessment system to predict IAN injury during surgical extraction of the LM3. We conducted a retrospective cohort study on 115 patients diagnosed as 'high-risk' based on our previous risk assessment method involving three anatomical features of the inferior alveolar canal using computed tomographic (CT) images. We evaluated the occurrence of neurosensory impairment in these high-risk patients, and its association with novel anatomic features based on CT images. Neurosensory impairments were observed in 19 patients (16.5%). The inferior alveolar canal major diameter (p < 0.0001) and lingual bone thickness (p = 0.0039) were significantly associated with the occurrence of neurosensory impairment during LM3 extraction. Receiver operating characteristic curves were used to determine cut-off values of these quantitative factors to specifically predict IAN injury. Preoperative risk assessment with quantitative factors based on anatomical features observed on CT images may facilitate more appropriate surgical planning for patients at a high risk of IAN injury.

Evaluating the presence of IAN injury in patients with juxta-apical radiolucency after third molar surgery: a retrospective cohort study

Background

Juxta-apical radiolucency (JAR) has been presented as a radiographic sign, suggestive of the IAN injury through third molar surgery. This study aimed to evaluate the relation of JAR with IAN injury in cone-beam computed tomography (CBCT) images and to determine whether the presence of JAR is related to tooth angulation, proximity to the mandibular canal, position to the IAN, and thinning of the cortical plates.

Methods

Of an initial sample of 545 mandibular third molars, a total of 75 JAR⁺ and 75 JAR⁻ teeth were evaluated by CBCT. We assessed the relationship between the presence of JAR in cone-beam computed tomography (CBCT) images and the presence of IAN injury after mandibular third molar surgeries. Moreover, we investigated whether the presence of IAN injury is related to tooth angulation, proximity to the mandibular canal, position to the IAN, and thinning of the cortical plates. Descriptive statistics, Chi-square test, and Fisher’s exact test were performed for statistical analysis.

Results

A significant relationship was found between JAR and temporary IAN injury (P = 0.036). However, there was no case of permanent IAN injury. IAN injury showed no significant relationship with the tooth angulation, position to IAN and proximity to the mandibular canal, lingual cortical plate thinning, sex, and age.

Conclusions

JAR is generally in contact with the mandibular canal, and some degree of cortical thinning can be found in most cases. In this study, JAR was significantly related to temporary IAN injury. JAR may increase the risk of nerve injury during the surgical removal of third molars.

Retrospective evaluation of sensory neuropathies after extraction of mandibular third molars with confirmed "high-risk" features on cone beam computed topography scans

OBJECTIVES

The objective of this study was to identify the incidence of inferior alveolar nerve (IAN) injury after extraction of mandibular third molars with confirmed "high-risk" features on cone beam computed topography scans and establish any risk factors that significantly increase the chances of sustaining an IAN injury.

STUDY DESIGN

This study is a retrospective analysis of outcomes after surgical extraction of 500 mandibular third molars over a 5-year period. All teeth showed signs of contact with or compression of the IAN on cone beam computed topography scans.

RESULTS

The overall incidence of IAN injury was 6.6%, with permanent neuropathies accounting for 1.8% within this high-risk cohort. Statistically significant factors shown to increase the risk of nerve injury included increasing age (P = .002), compression of the nerve evident on cone beam computed topography scan (P = .005), and buccal or interradicular position of the nerve (P = .042).

CONCLUSIONS

Results indicate a low incidence of IAN injury, particularly given the high-risk nature of all teeth that were extracted. It highlights the benefits of cone beam computed topography scans in surgical planning. These data are an important contribution to the existing literature and valuable in the consent procedure for patients undergoing surgical removal of mandibular third molars in contact with the IAN.

Anatomical Risk Factors of Inferior Alveolar Nerve Injury Association with Surgical Extraction of Mandibular Third Molar in Korean Population

The purpose of this study was to analyze the incidence and risk factors of possible inferior alveolar nerve (IAN) injury after extraction of the mandibular third molars. A total of 6182 patients were examined for 10,310 mandibular third molar teeth. Panoramic radiography and patients’ medical records were used to analyze age, gender, and impaction pattern of the mandibular third molar. Cone beam computed tomography (CBCT) was used to investigate the detailed pathway of the inferior alveolar nerve and evaluated the presence of symptoms of nerve damage after tooth extraction. In CBCT, 6283 cases (61%) of the inferior alveolar nerve were actually in contact with the root of the mandibular third molar. The correlation with the panoramic signs of root darkening (p < 0.001), root deflection (p < 0.001), interruption of the IAN (p < 0.001), diversion of the IAN (p < 0.001), and narrowing of the IAN (p < 0.001) had statistical significance. Of the 4708 patients who underwent surgical extraction, 31 (0.658%) complained of nerve damage. Among them, 30 patients (0.637%) complained of symptoms of inferior alveolar nerve damage, and 1 patient (0.02%) complained of symptoms of lingual nerve damage. There was a significant correlation with IAN injury in cases where the roots became dark at the IAN area (p = 0.018) and there was diversion of the IAN at the root area (p = 0.041). When the narrowing of the IAN and the lingual driving pathway of the inferior alveolar nerve appeared simultaneously in CBCT, the risk of IAN injury was high.

Orthodontic-related nerve injuries: a review and case series

Trigeminal neuropathy secondary to orthodontic tooth movement is reported as a rare occurrence. Risk assessment is possible to prevent or immediately treat these injuries and clinicians should be aware of the risk factors. Increasingly, orthodontics is provided by non-specialists and orthodontic therapists. This paper presents cases and a review of orthodontic-related nerve injuries, where early diagnosis of orthodontic nerve injuries was misdiagnosed, preventing early or immediate treatment that would have likely optimised neural recovery and prevented permanent sensory neuropathic pain in these patients. We present two cases of trigeminal neuropathy following orthodontic tooth movement that highlight some key issues relating to improving pre-orthodontic risk assessment during treatment planning and early identification of developing neuropathy requiring urgent cessation/reversal of orthodontic treatment. The cases presented demonstrate the importance of thorough pre-orthodontic assessment before treatment planning. Traditionally, two-dimensional imaging such as panoramic and periapical radiographs have been the gold standard for predicting the relationship of the dentition to the mandibular canal. However, cone beam computed tomography imaging is now accepted as providing a more accurate image of the position of the teeth in relation to vital structures, such as neurovascular supply.

Risk management in oral surgery

Complex oral surgery procedures are occurring more commonly in primary care, performed by both specialist oral surgeons and non-specialists/tier 2 providers. Practitioners in the UK are working in an increasingly litigious environment which is often at the forefront of a practitioner's mind and prevention of complaints and claims of negligence is vital in maintaining confidence in our practise. In this ever-increasing litigious environment practitioners need to be aware of the risks associated with oral surgery procedures and have to be able to assess and treatment plan patients effectively and safely. Consent is critical to all procedures, and the recent Montgomery case reinforces the importance of this process which must be individual to each patient. It is vital that as practitioners we are aware of our scope of practice and are able to fully inform patients of the risks and benefits of treatment. Practitioners must know their limits and when to refer on to secondary care. This paper discusses the essentials of risk management in oral surgery and describes key stages in the management of patients undergoing an oral surgery procedure. Initial assessment of the patient, which includes medical and dental history will be discussed followed by investigations to support the clinical diagnosis. Once diagnosis has been confirmed, the process of obtaining consent and the legal implications of this are discussed. Finally, a discussion on the appropriate evidence-based management of common complications which may arise when performing oral surgery will complete the paper.

Panoramic versus CBCT used to reduce inferior alveolar nerve paresthesia after third molar extractions: a systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review was to verify whether CBCT in comparison with panoramic radiography reduced the cases of temporary paresthesias of the inferior alveolar nerve (IAN) associated with third molar extractions.

METHODS

The literature search included five databases (PubMed, Scopus, Web of Science, Cochrane, SciELO), in addition to gray literature and hand search of reference list of included studies. Two reviewers independently screened titles/abstracts, and full texts according to eligibility criteria, extracted data and evaluated risk of bias through Revised Cochrane Risk of Bias Tool for Randomized Trials (RoB 2.0). Data were meta-analyzed by comparing CBCT versus panoramic radiographs for number of events (temporary paresthesia after third molar surgery). Fixed effect model was used for non-significant heterogeneity; relative risk (RR) and 95% CI were calculated. The certainty of evidence was evaluated by Grading of Recommendations, Assessment, Development, and Evaluation (GRADE).

RESULTS

Four randomized controlled trials (RCTs) were included in meta-analysis, and for the majority of domains they presented low risk of bias. RR was 1.23 (95% IC: 0.75-2.02; I²: 0%; p = 0.43) favouring panoramic radiography, but without significant effect, and with moderate certainty of evidence.

CONCLUSIONS

We concluded that both interventions had a similar ability to reduce temporary paresthesia of the IAN after third molar surgery with moderate certainty of evidence.

Correlation of panoramic high-risk markers with the cone beam CT findings in the preoperative assessment of the mandibular third molars

Background/purpose

Preoperative radiographic examination of mandibular third molars (MTM) is essential to prevent inferior alveolar nerve (IAN) injury. The aim of this study was to assess the panoramic radiography (PAN) signs considered as indicators of increased risk of IAN injury and to correlate them with the cone beam CT (CBCT) findings.

Materials and methods

58 patients who had MTMs extraction between January 2012 and January 2018. OPG were evaluated for the following signs: interruption of the roof of the canal, root darkening, roots deflection and narrowing, canal deviation, superimposition between the MTM roots and mandibular canal. Loss of canal cortication, root grooving, thinning and perforation of lingual cortex were assessed in CBCT images. Chi-square test and multivariate logistic regression tests were used to test the relationship between PAN signs and CBCT findings.

Results

A total of 79 MTMs were examined. Loss of canal cortication in CBCT was seen in 22 (27.8%) of the cases. Root darkening in PAN images was the most frequent radiographic sign. Canal deviation and interruption of white line in PAN demonstrated a statistically significant correlation with the loss of canal cortication between the MTM and the mandibular canal on CBCT images (p = 0.004 and p = 0.012, respectively). No statistically significant association was observed for the other PAN signs and CBCT findings.

Conclusion

Canal deviation and interruption of white lines were associated with loss of canal cortication on CBCT, indicating a direct contact between the roots and the mandibular canal which required a further assessment prior to the extraction.

Is juxta-apical radiolucency a reliable risk factor for injury to the inferior alveolar nerve during removal of lower third molars?

The aim of this study was to find out if juxta-apical radiolucency (JAR) is a reliable risk factor for injury to the inferior alveolar nerve (IAN) during removal of lower third molars. We designed a cohort study of patients whose dental panoramic tomograms (DPT) had shown JAR before complete removal of lower wisdom teeth. The outcome variable was postoperative permanent neurosensory disturbance of the IAN. A total of 39 patients (50 lower third molars) were identified and screened for permanent neurosensory disturbance. None reported any permanently altered sensation 18 months after the operation. Based on our group, the presence of JAR does not seem to be a reliable predictor of the risk of permanent injury to the IAN during removal of lower third molars.

Comparison of panoramic radiography and cone beam CT in the assessment of juxta-apical radiolucency

OBJECTIVES

To compare the performance of panoramic radiography (PAN) and cone beam CT (CBCT) in the detection of juxta-apical radiolucency (JAR), as well as to investigate, in CBCT images, if there are factors associated with the detection of JAR on PAN.

METHODS

Two oral radiologists assessed the presence of JAR in PAN and CBCT images of 175 individuals (308 mandibular third molars). The cortical plates involvement and the JAR size and location were assessed on CBCT to evaluate if these factors were related to JAR detection on PAN. McNemar's test and multiple logistic regression were performed.

RESULTS

PAN and CBCT differed significantly in the detection of JAR (p = 0.001). On PAN, JAR was identified on 24% of the patients while on CBCT its detection increased to 32.6%. JAR was detected only on CBCT and only on PAN in 26 and 7 cases, respectively. Distal/mesial surfaces of dental roots were where JAR was mostly located (84.5%), cortical thinning was found in 59.2% of cases and the mean (SD) of JAR size was 5.03 (±1.8) mm. However, these factors were not associated with JAR detection on PAN (p > 0.05). On the other hand, the location of the cortical involvement (if buccal or lingual) was associated with JAR detection on PAN, which was more detectable when the thinning was on buccal cortical.

CONCLUSIONS

Juxta-apical radiolucency is more often detected on CBCT than on PAN. JAR detection on PAN was improved when it was related to the buccal cortical plate of the mandible.

Combined preoperative measurement of three inferior alveolar canal factors using computed tomography predicts the risk of inferior alveolar nerve injury during lower third molar extraction

A retrospective cohort study was performed to assess the clinical usefulness of combination assessment using computed tomography (CT) images in patients undergoing third molar extraction. This study included 85 patients (124 extraction sites). The relationship between cortication status, buccolingual position, and shape of the inferior alveolar canal (IAC) on CT images and the incidence of inferior alveolar nerve (IAN) injury after third molar extraction was evaluated. IAN injury was observed at eight of the 124 sites (6.5%), and in five of 19 sites (26.3%) in which cortication was absent+the IAC had a lingual position+the IAC had a dumbbell shape. Significant relationships were found between IAN injury and the three IAC factors (cortication status, IAC position, and IAC shape; P=0.0001). In patients with the three IAC factors, logistic regression analysis indicated a strong association between these factors and IAN injury (P=0.007). An absence of cortication, a lingually positioned IAC, and a dumbbell-shaped IAC are considered to indicate a high risk of IAN injury according to the logistic regression analysis (P=0.007). These results suggest that a combined assessment of these three IAC factors could be useful for the improved prediction of IAN injury.

Diagnostic value of cone beam computed tomography and panoramic radiography in predicting mandibular nerve exposure during third molar surgery

The aim of this study was to evaluate the diagnostic accuracies of cone beam computed tomography (CBCT) and panoramic techniques in predicting inferior alveolar nerve (IAN) exposure. The sample size was determined based on a pilot study. This prospective clinical series study included 59 third molar extraction sites with any of seven previously suggested panoramic signs of IAN exposure. The diagnosis of nerve exposure was done on panoramic and CBCT images. Molars were extracted and nerve exposure was evaluated clinically. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CBCT method, and sensitivity and PPV of panoramic method were estimated). The panoramic and CBCT methods correctly classified 67.7% and 93.3%, respectively, of 60 cases. This difference was statistically significant (χ²=13.333, P=0.000). The sensitivity, specificity, PPV, and NPV for CBCT were 97.4%, 85.7%, 92.7%, and 94.7%, respectively. The sensitivity and PPV of panoramic radiography were 67.8% and 97.6%, respectively. The signs with the highest sensitivity were interruption of the mandibular canal border and abrupt canal narrowing. None of the Pell and Gregory criteria, molar angulations, or three-dimensional canal-apex relationships was significantly associated with clinically confirmed IAN exposure. Panoramic radiography may miss about one-third of exposure cases, but a positive panoramic diagnosis is most likely to be a real exposure and should be taken seriously.

A multivariate statistical analysis on variables affecting inferior alveolar nerve damage during third molar surgery

AIM

The risk factors associated with inferior alveolar nerve damage during third molar surgery were investigated.

MATERIAL AND METHODS

Surgeries performed during a period of 50 months by a single expert surgeon were reviewed. Only those surgeries that met the selected inclusion criteria were considered for this study. The following tests were applied for the statistical analysis: the Kolmogorov-Smirnov test, the principal components analysis, the Mann-Whitney U test, the two-tailed exact Fisher test and the Bonferroni sequential correction.

RESULTS

The surgical difficulty index, multi-rooted third molars and changes in the inferior alveolar nerve running in relation to the tooth roots are predictors of nerve damage.

CONCLUSIONS

Computed tomography is mandatory when the nerve is superimposed on the tooth root on the ortopantomography. SCIENTIFIC RATIONALE FOR STUDY: Lower third molar extraction is one of the most common procedures in oral and maxillofacial surgery, and it is burdened by the risk of inferior alveolar nerve damage. Understanding which factors are able to predict this complication is therefore essential in correctly programming surgery.

PRINCIPAL FINDINGS

Surgical difficulty index, multi-rooted third molars and changes in inferior alveolar nerve running in relation to the tooth roots are predictors of nerve damage.

PRACTICAL IMPLICATIONS

If, on the orthopantomography, the nerve is superimposed on the tooth root, a computed tomography is mandatory to define all of these variables.

Evaluation of the relationship between mandibular third molar and mandibular canal by different algorithms of cone-beam computed tomography

OBJECTIVES

Exact location of the inferior alveolar nerve (IAN) bundle is very important. The aim of this study is to evaluate the relationship between the mandibular third molar and the mandibular canal by cone-beam computed tomography.

STUDY DESIGN

This was a cross-sectional study with convenience sampling. 94 mandibular CBCTs performed with CSANEX 3D machine (Soredex, Finland) and 3D system chosen. Vertical and horizontal relationship between the mandibular canal and the third molar depicted by 3D, panoramic reformat view of CBCT and cross-sectional view. Cross-sectional view was our gold standard and other view evaluated by it.

RESULTS

There were significant differences between the vertical and horizontal relation of nerve and tooth in all views (p < 0.001).

CONCLUSION

The results showed differences in the position of the inferior alveolar nerve with different views of CBCT, so CBCT images are not quite reliable and have possibility of error.

Clinical significance of computed tomography assessment for third molar surgery

Surgical extraction of the third molar is the most commonly performed surgical procedure in the clinical practice of oral surgery. Third molar surgery is warranted when there is inadequate space for eruption, malpositioning, or risk for cyst or odontogenic tumor formation. Preoperative assessment should include a detailed morphologic analysis of the third molar and its relationship to adjacent structures and surrounding tissues. Due to developments in medical engineering technology, computed tomography (CT) now plays a critical role in providing the clear images required for adequate assessment prior to third molar surgery. Removal of the maxillary third molar is associated with a risk for maxillary sinus perforation, whereas removal of the mandibular third molar can put patients at risk for a neurosensory deficit from damage to the lingual nerve or inferior alveolar nerve. Multiple factors, including demographic, anatomic, and treatment-related factors, influence the incidence of nerve injury during or following removal of the third molar. CT assessment of the third molar prior to surgery can identify some of these risk factors, such as the absence of cortication between the mandibular third molar and the inferior alveolar canal, prior to surgery to reduce the risk for nerve damage. This topic highlight presents an overview of the clinical significance of CT assessment in third molar surgery.

Evaluation of juxta-apical radiolucency in cone beam CT images

OBJECTIVES

The aim of this study was to analyse the position and relationship of juxta-apical radiolucency (JAR) to the mandibular canal and buccal and/or lingual cortical plates using cone beam CT (CBCT).

METHODS

A retrospective study was carried out to analyse the JAR on CBCT for 27 patients. These findings were compared with 27 age- and sex-matched patients without the presence of JAR, which acted as the control group. The CBCT images were analysed according to a checklist, to evaluate the position of the JAR and its relationship to the mandibular canal. Then, any thinning or perforation of either the buccal or lingual cortical plate due to JAR was noted, and a classification to quantify the thinning of cortical plates was proposed. The findings in the two groups were analysed using a paired comparison by McNemar test.

RESULTS

A statistical increased thinning of cortical plates was seen in the JAR group compared with the control group, and most of the cases were in the J3 group. None of the patients in either the JAR or the control group showed perforation of the buccal and/or lingual cortical plate on CBCT images.

CONCLUSIONS

A classification to quantify the thinning of cortical plates was proposed, which may be used for objective evaluation of the thinning of the cortical plates in future studies. The present study gives an insight into the relationship of the juxta-apical area with the mandibular canal and cortical plates in the mandible using CBCT.

Relationships between third-molar juxta-apical radiolucencies and mandibular canals in panoramic and cone beam computed tomography images

OBJECTIVE

This study aimed to determine the relationship between third-molar juxta-apical radiolucencies and mandibular canals on panoramic and cone beam computed tomography (CBCT) images.

STUDY DESIGN

Forty-two patients were included in this retrospective study. The root apices and the relationships of the juxta-apical radiolucencies to the mandibular canals were evaluated on both panoramic and CBCT images. The McNemar test (P < .05) was used to compare panoramic with CBCT findings.

RESULTS

Root apices were visualized clearly with CBCT in most cases for which the apices were not seen clearly on panoramic images. Similarly, juxta-apical radiolucencies were separate from the mandibular canals with CBCT in most cases.

CONCLUSIONS

The present study found that there is no consistent intimate relationship between juxta-apical radiolucencies and the mandibular canals. Similar studies with larger sample sizes are required to further confirm these findings.

Assessment of the shape of the inferior alveolar canal as a marker for increased risk of injury to the inferior alveolar nerve at third molar surgery: a prospective study

PURPOSE

Morphologic evaluation of computed tomographic images is an important assessment tool before surgical removal of the lower third molar (LM3). The aim of this study was to ascertain whether the shape of the inferior alveolar canal (IAC) is a reliable predictor for inferior alveolar nerve (IAN) injury during M3 surgery.

MATERIALS AND METHODS

This prospective study assessed samples with a high risk of IAN injury during M3 surgery based on orthopantomographic examination. The predictor variables were demographic factors (patient's age and gender), anatomic factors (angulation of the tooth), and radiographic factors (cortication status, buccolingual position, shape of the IAC, number of roots, and root shape). The outcome variable was IAN injury. The relation between predictor and outcome variables was analyzed using the Fisher exact test and a logistic regression model.

RESULTS

One hundred sixty-nine LM3s (115 patients) were analyzed. IAN injury was observed in 12 of 115 patients and 13 of 169 LM3s (7.7%). All 13 cases with IAN injury exhibited absence of cortication. A dumb-bell-shaped IAC was considered a useful predictor for IAN injury (sensitivity, 69.2%; specificity, 84.6%). In cases with absence of cortication, logistic regression analysis indicated that a dumb-bell-shaped IAC was closely related to IAN injury (P = .005).

CONCLUSION

The cortication status and shape of the IAC are reliable predictors for IAN injury at M3 surgery. Cases exhibiting absence of cortication and a dumb-bell-shaped IAC should be recognized as presenting a high risk of IAN injury at M3 surgery.

Update on coronectomy. A safer way to remove high risk mandibular third molars

Decoronation of high risk mandibular third molars (M3Ms) has become common practice in parts of UK and USA. With the introduction of Cone Beam CT scanning, there has been an evolution in the practice, with avoidance of unnecessary coronectomies based on CBCT findings. Also, additional anatomical features found only on CBCTs have introduced possible additional indications to undertake intentional coronectomy. Trigeminal nerve injury is the most problematic consequence of dental surgical procedures with major medico-legal implications. Iatrogenic injuries to the third division of the trigeminal nerve remain a common and complex clinical problem. Altered sensation and pain in the orofacial region may interfere with speaking, eating, kissing, shaving, applying make-up, toothbrushing and drinking; namely just about every social interaction we take for granted. Usually after oral rehabilitation, the patient expects and experiences significant improvements, not only regarding jaw function, but also in relation to dental, facial, and even overall body image. Thus these injuries have a significant negative effect on the patient's self-image and quality of life and the iatrogenesis of these injuries lead to significant psychological effects.

CLINICAL RELEVANCE

Coronectomy is an alternative procedure to complete removal of a mandibular third molar in situations where there is high risk of damage to the inferior alveolar nerve.

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.

Proximity of impacted mandibular third molars to the inferior alveolar canal and its radiographic predictors: a panoramic radiographic study

PURPOSE

To assess the radiographic proximity of impacted mandibular third molars to the inferior alveolar canal on panoramic radiographs. The radiographic distance between the impacted mandibular third molars and inferior alveolar canal and the reliable radiographic risk predictor signs that indicate close proximity between these two structures were evaluated.

METHODS

The study comprised of 64 subjects with 68 symptomatic impacted mandibular third molars for whom panoramic radiographs were made. The radiographs were interpreted for type of impaction, radiographic distance between impacted mandibular third molars to inferior alveolar canal and presence of one or more of the seven radiographic risk predictor signs. Further, these teeth were surgically removed and the proximity was assessed based on the exposure of inferior alveolar canal/nerve which was considered as Gold standard.

RESULTS

The overall mean distance from the impacted mandibular third molars to inferior alveolar canal was -0.50 mm. Most of the samples (61.8 %) extended beyond the superior border of the inferior alveolar canal with a mean distance of -1.40 mm. Mesioangular impactions were found to be in the close proximity (-1.14 mm) to inferior alveolar canal than any other type. Interruption of the white line was the only statistically significant radiographic risk predictor sign p = 0.006 (< 0.05) that indicated close proximity of impacted mandibular third molars to inferior alveolar canal.

CONCLUSION

It can be concluded that panoramic radiographs are reliable in assessing the proximity of impacted mandibular third molars to inferior alveolar canal. Mesioangular impactions are more closely placed to inferior alveolar canal and interruption of the white line is the most reliable risk predictor sign on the panoramic radiographs.

Clinical significance of computed tomographic assessment and anatomic features of the inferior alveolar canal as risk factors for injury of the inferior alveolar nerve at third molar surgery

PURPOSE

To assess the clinical features of the inferior alveolar canal (IAC) using computed tomography (CT) and to analyze the significance of CT examination at third molar surgery.

MATERIALS AND METHODS

A retrospective cohort study was performed involving 99 patients (145 teeth). The relationship between cortication status, buccolingual position, and shape of the IAC on the CT image and inferior alveolar nerve (IAN) injury after third molar surgery were statistically analyzed.

RESULTS

The shape of the IAC was categorized into 3 groups: round/oval, teardrop, and dumbbell. IAN injury was observed in 7 of 145 cases (4.8%). All 7 cases exhibited absence of cortication; 3 were dumbbell shape and 4 were round/oval. According to logistic regression analysis of cases with absence of cortication, IAC shape was closely related to IAN injury.

CONCLUSIONS

These results suggest that assessment of the IAC shape and cortication status at third molar surgery may be clinically useful.