Assessment and Correlation of Variation in Lingual Cortical Plate Thickness with Different Angulations of Impacted Mandibular Third Molar Using Cone Beam Computed Tomography in North Indian Population

Purpose

The extraction of impacted mandibular third molar is associated with various types of intraoperative and postoperative complications, one of them is injury to lingual nerve. The present study aims to assess and correlate the variation in lingual cortical plate thickness with different angulations and determine the topographic relationship between the root apex of impacted mandibular third molar and lingual cortical plate using Cone Beam Computed Tomography (CBCT).

Methods

This prospective cohort study enrolled 140 patients with impacted mandibular third molars who underwent preoperative CBCT imaging. The CBCT images were used to evaluate the outcome variables such as lingual cortical plate thickness and topographical relationship between root apex of impacted mandibular third molar and lingual cortical plate. The predictor variables included age, gender, inclination of third molar, mesiodistal angle, buccolingual angle and lingual plate morphology.

Results

The temporary lingual nerve paresthesia was reported by 1 patient (0.71%) out of 140 patients. The lingual bone in distoangular and vertical impacted third molar was found to be 1.20 times thicker than mesioangular and horizontal teeth. Lingual bone thinning at mid-root level was observed in maximum number of cases with mesioangular teeth (68.5%), whereas horizontal impacted teeth showed lingual bone thinning (90.9%) at root apex level. The mean buccolingual angle of impacted mandibular third molar was found to be significantly associated with lingual bone perforation (p value = 0.0258). The morphology of lingual plate was observed as undercut type (37.14%) followed by slanted (36.43%), parallel (19.29%) and round type (7.14%).

Conclusion

Increase in buccolingual angle of impacted mandibular third molar decreases lingual bone thickness which is the natural barrier for protecting injury to lingual nerve. Also undercut and slanted lingual plate shapes were recognised as risk factors for contact/perforation between root apex and lingual plate. Therefore, proper screening and planning of high risk patients before third molar extraction is crucial.

Proximity of mandibular third molar root(s) to surrounding cortical bone: cone beam computed tomography (CBCT) and panoramic findings

PURPOSE

We evaluated the relationship between mandibular third molar roots (M3Ms) and surrounding cortical bone using cone beam computed tomography (CBCT) and panoramic findings. We studied (a) the location of mandibular third molar roots in relation with cortical bone in terms of contact, penetration, and perforation on CBCT; (b) the relationship between characteristics of a root in panoramic findings and the CBCT image (entire and segmentally); and (c) the relationship of the root plane in panoramic findings vs. CBCT.

MATERIAL AND METHODS

One hundred five teeth with 224 roots of mandibular third molar from 73 patients were evaluated by using cone beam computed tomography and panoramic image.

RESULT

The relationships were assessed using 105 images of impacted M3Ms: 104/105 (99%) showed cortical bone involvement (30.4% penetration and 68.6% perforation). The more apical the segment, the higher the proportion of perforation. Most (79.9%) of the M3M roots involved a lingual cortex with 46.9% penetration and 49.2% perforation. The panoramic signs of segmental root images-viz. clear and blurred-were not associated with cortical penetration or perforation. Panoramic signs of individual root images-in the same and different planes-could be used to predict root plane M3M roots. The same appearance in the panoramic image was significantly related to the same plane of the root in CBCT (p-value 0.048).

CONCLUSION

These findings could contribute to enhanced radiological assessment and surgical planning.

Assessment of lower third molar space: A comparative radiographic study

Objective:

The aim of this study was to assess lower third molar space using four different radiographic reconstructed Cone Beam Computed Tomography (CBCT) images: orthopantomogram, lateral cephalogram, multiplanar CBCT and a newly introduced three-dimensional (3D) simulation technique.

Methods:

The CBCT scans of 32 individuals (20.97 ± 2.152 years) with a total of 50 lower third molars were collected and analyzed. The ratio between the necessary space and available space for lower third molars was calculated on each radiographic reconstructed image. Repeated-measure analysis of variance followed by multiple comparison tests were used.

Results:

The mean ratio was significantly smaller with cephalograms (0.611 ± 0.263), followed respectively by orthopantomograms (0.756 ± 0.221), multiplanar CBCT (0.789 ± 0.191) and 3D simulation technique (0.807 ± 0.193) (p < 0.001). The lowest mean difference was recorded between multiplanar CBCT and 3D simulation technique (0.017). Intra class correlation coefficient was strong (>0.90) for all techniques except cephalograms.

Conclusions:

The assessment of the lower third molar space differs according to the adopted imaging technique. 3D simulation technique is a useful novel technology that allows an exploration of the crown in many different dimensions and orientations, giving more predictable results than the conventional methods.

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.

Role of Panoramic Imaging and Cone Beam CT for Assessment of Inferior Alveolar Nerve Exposure and Subsequent Paresthesia Following Removal of Impacted Mandibular Third Molar

Objectives

Pre-operative radiographic evaluation of impacted mandibular third molar and inferior alveolar canal (IAC) is important in preventing a possible nerve exposure and damage during surgical removal. The present study analysed the relation of the mandibular third molar with inferior alveolar canal using panoramic radiography (PAN) and cone beam CT (CBCT) and evaluated the radiographic features suggestive of IAN exposure and post-operative paresthesia.

Materials and Methods

PAN and CBCT findings of 53 impacted mandibular third molars having a close relation with IAC undergoing extraction were analysed. Further, all cases were evaluated for any sensory loss in relation to IAN 1 week post-operatively.

Results

The most common PAN feature was combination of darkening of roots (DR) and interruption of white line (IWL), seen in 35.86% (19) cases. The most common CBCT feature was thinning of lingual cortex in 81.14% (43) cases. The most common location of IAC in CBCT was inferior in 47.16% (25) cases, followed by buccal 26.41% (14). On comparison of PAN and CBCT findings, DR and IWL both exclusively 92.86% (13); 80% (12) cases and in combination 75% (15) were most commonly associated with thinning of lingual cortex. IAN exposure was seen in 7.55% (4) cases, and 3.77% (2) cases reported with paresthesia. Absence of corticalisation and IWL was associated with all cases of nerve exposure, inter-radicular location of IAC seen in three out of the four cases. Cases with paresthesia had DR and deflection of roots (DEFR) with thinning of lingual cortex by roots.

Conclusion

DR with DEFR or IWL in PAN as combination and inter-radicular location of IAC with thinning of lingual cortex by root tips in CBCT are highly predictive of nerve exposure and subsequent paresthesia.

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.

Efficacy of CBCT for assessment of impacted mandibular third molars: a review - based on a hierarchical model of evidence

A radiographic examination of mandibular third molars is meant to support the surgeon in establishing a treatment plan. For years panoramic (PAN) imaging has been the first choice method; however, where an overprojection is observed between the third molar and the mandibular canal and when specific signs suggest a close contact between the molar and the canal, CBCT may be indicated. The present review provides an evaluation of the efficacy of CBCT for assessment of mandibular third molars using a six-tiered hierarchical model by Fryback and Thornbury in 1991. Levels 1-3 include studies on low evidence levels mainly regarding the technical capabilities of a radiographic method and the diagnostic accuracy of the related images. Levels 4-6 include studies on a higher level of evidence and assess the diagnostic impact of a radiographic method on the treatment of the patient in addition to the outcome for the patient and society including cost calculations. Only very few high-evidence studies on the efficacy of CBCT for radiographic examination of mandibular third molars exist and, in conclusion, periapical or PAN examination is sufficient in most cases before removal of mandibular third molars. However, CBCT may be suggested when one or more signs for a close contact between the tooth and the canal are present in the two-dimensional image-if it is believed that CBCT will change the treatment or the treatment outcome for the patient. Further research on high-evidence levels is needed.

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.