Association between impacted third molars and position of the mandibular canal: a morphological analysis using cone-beam computed tomography

Radiographic evaluation of mandibular third molars: an ex vivo comparative study between multilayer and conventional panoramic radiography

OBJECTIVES

To compare the multilayer panoramic radiography (MPAN) and conventional panoramic radiography (CPAN) in the evaluation of mandibular third molars using cone-beam computed tomography (CBCT) as a reference.

METHODS

CPAN, MPAN, and CBCT scans from 33 dry human mandibles were acquired using the OP300 Maxio unit, totalizing 56 mandibular third molars to be evaluated. Three examiners evaluated each third molar according to their position, depth of impaction in the mandibular ramus, proximity between the dental root apexes and the mandibular canal, and the presence of radiographic signs of proximity to the mandibular canal. In addition, when there was a distance between the root apexes and the mandibular canal, it was measured. As a reference, these same parameters were assessed in the CBCT scans by a fourth examiner. For the statistical analysis, the weighted Kappa, Bland Altman, and Wilcoxon tests were performed (α = 0.05).

RESULTS

The agreement between the assessments performed in the panoramic modalities with the CBCT ranged from 66.1% to 100.0% for the categorical variables. Overall, the agreement values of CPAN and MPAN with CBCT were similar. The distances between the dental root apex and the mandibular canal for both CPAN and MPAN were significantly underestimated compared to CBCT (p < 0.05). The intra- and interexaminer agreements of the examiners ranged from poor to almost perfect; in general, the agreements were higher in the evaluation performed in the MPAN than in the CPAN.

CONCLUSIONS

The MPAN performs similarly to CPAN for evaluating mandibular third molars and their proximity relationship to the mandibular canal.

CLINICAL RELEVANCE

Preoperative evaluation of lower mandibular third molars is usually performed using CPAN. Recently, a new tool, MPAN, was developed, which has not yet been tested for the evaluation of mandibular third molars and showed similar performance to CPAN in the present study. Future studies using MPAN are encouraged to evaluate other diagnostic tasks.

Cone-Beam Computed Tomography Analysis on the Relationship between the Mandibular Third Molar and the Position of the Mandibular Canal in Koreans from the Yanbian Area and the Han People

OBJECTIVE

To analyze differences in the positional relationships between the mandibular third molar (MTM) and the mandibular canal in Korean and Han patients using cone-beam computed tomography (CBCT) and to provide a basis for preoperative risk assessments.

MATERIALS AND METHODS

The CBCT imaging data of 260 Korean and Han patients were collected. The patients' genders, ages, impaction types and depths, relative positions between the MTMs and the mandibular nerve canals, and the shortest distances and shapes at the root tips and cortical bones were all recorded and analyzed. All data were compared using the nonparametric test, ordered logistic regression analysis, a chi-square test, and Fisher's exact test.

RESULTS

The relationship between the mandibular canal and the relative position of the MTM differed between Korean and Han patients, mainly in the different types of impactions, and the difference was statistically significant (P < 0.05). The shortest distance between the mesioangular and horizontally impacted mandibular canals and the buccal side of the MTM in Korean patients was less than in Han patients, and the difference was statistically significant (P < 0.05). For horizontal impactions, the probability of cortical bone interruption was 1.980 times greater in Korean patients than in Han patients, and the difference was statistically significant (P < 0.05). The significance threshold was set at 0.05.

CONCLUSION

There are some differences in the positional relationship between the mandibular canal in the MTM region and the rate of cortical bone disruption between Koreans from the Yanbian area and the Hans. This should gain clinical attention.

Correlation of Panoramic Radiological and Intra-Operative Findings of Impacted Mandibular 3rd Molar in Relation to Inferior Alveolar Canal: A Prospective Study

Aim

The objective of this study was to correlate the preoperative radiological findings and intraoperative surgical findings during removal of impacted mandibular 3rd molar with respect to the inferior alveolar canal.

Materials and Method

The prospective study design included 100 patients between the age group of 20 years and 50 years who visited the Department of Oral and Maxillofacial Surgery at Vydehi Institute of Dental Sciences and Research Centre, Whitefield, Bengaluru. A preoperative panoramic radiograph was taken and the parameters were assessed and a normal surgical protocol was followed to extract the impacted mandibular 3rd molar with intra-operative assessment as well.

Results

Out of the 100 patients with definitive radiological signs showing close relation of the third molar to the mandibular canal who underwent surgical removal, only 12 patients presented with definitive clinical findings of the association.

Conclusion

A true close relationship between the third molars and mandibular canal increases the risk of inferior alveolar nerve injury, and accurate evaluation of the relationship is essential to avoid the risk of surgery. The accuracy of the plain radiographs to diagnose an intimate relationship between the neurovascular bundle and the third molar root has its limitations, since only 12 of the 100 patients with positive radiological signs showed clinical evidence of involvement. Surgeons should be aware of the limitations of the radiographic markers of panoramic radiography and should consider more detailed imaging in more specific cases in which one or more radiographic marker is present.

Preoperative Anatomic Evaluation of the Relationship Between Inferior Alveolar Nerve Canal and Impacted Mandibular Third Molar in a Population of Bhubaneswar, Odisha, Using CBCT: A Hospital-Based Study

Purpose

To evaluate the correlation between the position of inferior alveolar nerve canal and the angulation of impacted mandibular third molars using cone beam computed tomography (CBCT) in a hospital-based study in the state of Odisha, India.

Materials and Methodology

Three hundred cases of impacted third molars in 200 patients (154 males; 46 females) were included in the study, for whom an initial periapical or panoramic radiograph had revealed that the mandibular canal and the lower third molars were in close proximity. A CBCT scan of each patient was carried out to assess how the canal position influenced the class and position of impaction, angulation of impaction and bone contact.

Results

Class II position B impactions were found in 78.37% cases where the position of ID canal was approximate to the lingual plate and inferior to third molar (73.75%). The results were statistically significant (p = 0.00). 80% of the ID canals showed bone contact. Of these 73.75% ID canals showed lingual bone contact. Mesioangular impactions were most common in mandible and significantly associated with lingual and inferior positioning of the canal.

Conclusions

The study mostly exhibited patients having mesioangular class II position B third molar impactions of the mandible. The position of the canal has a significant influence on the type of impaction and the bone contact.