Correlation of panoramic radiography and cone beam CT findings in the assessment of the relationship between impacted mandibular third molars and the mandibular canal

Evaluation of anatomical relationships in the mandibular third molar region based on its angulation and depth of impaction: a CBCT-based study

PURPOSE

The aim of this study is to evaluate the relationship between the inclination/impaction depth and root proximity to the inferior alveolar canal/lingual plate on a millimeter scale using CBCT scans.

METHODS

340 CBCT scans of the mandibular third molar (M3) of 219 patients were evaluated for this cross-sectional study. After adjustment of the 3D orientation of the individual's jaws, the study variables including the angulation between M3 and second molar (M2)/occlusal plane (OP), and the distance of mesial (M)/distal (D) roots of M3 from the inferior alveolar canal (IAC) and lingual plate (LP) were measured. Winter's classification was used for the specification of teeth angulation. The vertical position of each M3 was then evaluated using the 3D view window (based on Pell & Gregory classification). The Spearman correlation coefficient was used for reporting the correlation between quantitative variables. The One-way ANOVA test and the Welch analysis were used for inter-group comparisons. Finally, a multivariant analysis of variances was performed.

RESULTS

Most third molars had a mesioangular inclination (52.1%), and vertical inclination (25.9%) was in second place. There was no significant correlation between angulation and age or the D/LP. A strong positive correlation between M3:M2 and M3:OP was observed (0.983). Furthermore, there was a weak negative correlation between M/IAC or M/LP and angulation (- 0.16 and - 0.13, respectively). Concerning Winter's classification, the relationship between D/IAC and angulation was statistically significant (P = 0.003). Furthermore, teeth in position A had lesser inclination compared to those with B or C positions. Multivariate analysis revealed that there was no statistically significant relationship between particular combinations of inclination-impaction depth and proximity of the M3 roots to the IAC or LP (P = 0.211).

CONCLUSIONS

The findings of the current study revealed that there is a strong correlation between M3:M2 and M3:OP. The D/IAC was the only variable that had a significant relationship with the angulation of these teeth. Moreover, the roots of horizontally inclined teeth with position A were the closest to the LP and the farthermost to the IAC.

Risk factors for impacted lower third molar root perforation through the undercut-shaped lingual plate: preoperative insights from panoramic radiography

This study aimed to identify risk factors associated with perforation of the undercut (U)-shaped lingual plate (LP) by the lower third molar (LM3) root using panoramic radiography (PAN). We retrospectively examined 468 impacted LM3s from 468 individuals, categorizing LM3-LP associations and LP morphology in the coronal section of cone-beam computed tomography as perforation or nonperforation and U-type or non-U-type, respectively. The outcome was the combination of perforation and U-type, and study variables included patient demographics (age and sex) and PAN-associated features (Winter's classification, Pell-Gregory classification, and two major Rood signs). Multivariate logistic regression methods were used for analysis. Perforated and U-type LPs were observed in 205 (43.8%) and 212 (45.3%) cases, respectively. The double-positive outcome was observed in 126 LM3s (26.9%). In the multivariate model, age ≥ 26 years [odds ratio (OR), 2.66; p = 0.002], men (OR, 2.01; p = 0.002), mesioangular (OR, 2.74; p = 0.038) and horizontal impaction (OR, 3.05; p = 0.019), and root darkening (OR, 1.73; p = 0.039) were independently associated with the risk. Class III impaction (OR, 0.35; p = 0.021) and interruption of the white line (OR, 0.55; p = 0.017) were negatively correlated with the risk. In conclusion, this study highlights the importance of identifying the higher probability of U-type LP perforation by the LM3 root in men aged over their midtwenties with Class I/II impaction and mesioangularly or horizontally impacted LM3s, along with root darkening and no interruption of the white line on PAN.

Effect of time-dependent ibuprofen administration on the post operatory after impacted third molar extraction: a cross-over randomized controlled trial

PURPOSE

To evaluate time-dependent administration of ibuprofen in a lower third molar extraction model.

METHODS

Eleven patients requiring bilateral surgical removal of lower third molars were recruited and randomized into a blinded crossover randomized controlled trial. For 3 days after surgery, the control group was prescribed ibuprofen 400 mg every 8 h. On the other hand, the experimental group received also ibuprofen 400 mg at breakfast and lunch, replacing the dinner intake with a placebo. Pain measurements (Visual Analog Scale from 0 to 10) were recorded at baseline, 24, 48, and 72 h postoperatively. Facial swelling and trismus were also measured at baseline, 24, and 72 h postoperatively.

RESULTS

Postoperative swelling and pain perception did not show significative difference between the control and experimental groups at 24, 48, and 72 h. Trismus was significantly lower in the control group than in the experimental group at 72 h postoperatively (p = 0.008). Rescue medication consumption seemed to be comparable between groups.

CONCLUSION

Eliminating night time ibuprofen might be insignificant for pain control after third molar extraction.

Panoramic Radiography vs. CBCT in the Evaluation of the Maxillary Third Molar Roots

Background and Objectives: A comprehensive understanding of the position of third molar roots and adjacent structures, such as the maxillary sinus (MS), is essential for safe extractions. Diagnostic imaging plays a fundamental role in achieving accurate treatment planning. This study aimed to compare panoramic radiography (PR) and cone-beam computed tomography (CBCT) for the evaluation of maxillary third molar roots and their relationship with the MS. Materials and Methods: Two trained radiologists evaluated third molar images. The number of roots, morphology (fused/conical, divergent, dilacerated, or atypical), and their relationship with the MS in PR and CBCT were registered. Descriptive and inferential statistics were performed using the weighted Kappa test. Results: Regarding the number and morphology of the roots, Kappa values showed moderate (κ = 0.42) and fair agreement (κ = 0.38), respectively. Regarding the proximity with the MS, most of the roots showed close contact (30.6%), or 1/3 of root superimposition (35%), in PR evaluation, while in CBCT, the third molars were in contact with the MS floor (32%), and with alveolar domes (27.2%). Conclusions: PR is a moderately reliable image technique to identify the number of roots and root morphology of maxillary third molars. PR, however, does not provide any radiographic signs that clearly indicate the anatomical relationship between the maxillary third molar roots and the maxillary sinus detected in CBCT images.

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.

Investigation of the best effective fold of data augmentation for training deep learning models for recognition of contiguity between mandibular third molar and inferior alveolar canal on panoramic radiographs

OBJECTIVES

This study aimed to train deep learning models for recognition of contiguity between the mandibular third molar (M3M) and inferior alveolar canal using panoramic radiographs and to investigate the best effective fold of data augmentation.

MATERIALS AND METHODS

The total of 1800 M3M cropped images were classified evenly into contact and no-contact. The contact group was confirmed with CBCT images. The models were trained from three pretrained models: AlexNet, VGG-16, and GoogLeNet. Each pretrained model was trained with the original cropped panoramic radiographs. Then the training images were increased fivefold, tenfold, 15-fold, and 20-fold using data augmentation to train additional models. The area under the receiver operating characteristic curve (AUC) of the 15 models were evaluated.

RESULTS

All models recognized contiguity with AUC from 0.951 to 0.996. Ten-fold augmentation showed the highest AUC in all pretrained models; however, no significant difference with other folds were found. VGG-16 showed the best performance among pretrained models trained at the same fold of augmentation. Data augmentation provided statistically significant improvement in performance of AlexNet and GoogLeNet models, while VGG-16 remained unchanged.

CONCLUSIONS

Based on our images, all models performed efficiently with high AUC, particularly VGG-16. Ten-fold augmentation showed the highest AUC by all pretrained models. VGG-16 showed promising potential when training with only original images.

CLINICAL RELEVANCE

Ten-fold augmentation may help improve deep learning models' performances. The variety of original data and the accuracy of labels are essential to train a high-performance model.

Can CBCT change the level of confidence of oral maxillofacial surgeons in mandibular third molar management?

This study analyzed the impact of CBCT on the level of confidence in diagnostic and treatment thinking in mandibular lower molar (M3M) clinical management. Thirty cases for which panoramic radiographs and CBTC images were available were selected and classified according to radiologic signs indicating the proximity of the M3M to the mandibular canal (interruption of the radiopaque borders of the canal of the mandibular canal wall, darkening of the roots, and diversion or narrowing of the canal, n = 10 for each classification). Twelve oral and maxillofacial surgeons (OMS) contributed to this study by answering two questionnaires. The first questionnaire contained a clinical description of the case and a panoramic radiograph. After 30 days, a second questionnaire with the same clinical illustrations and tomographic multiplanar reconstruction images was administered. Both questionnaires asked specialists to rate diagnostic confidence, the surgical complexity, chosen treatment, and surgical confidence. In approximately 40% of answers, CBCT images had a positive impact on ratings of diagnostic confidence and treatment thinking confidence, and in 24.4%, they increased the surgical complexity score. There was no change in the treatment plan following the use of CBCT, but the CBCT examination was a determining factor for diagnosis and treatment planning in 72.8% of the answers CBCT improved the confidence level in diagnostic and treatment thinking of the M3M management while also increasing the perceived level of surgical complexity. The findings of this study support the need to consider using CBCT in diagnosis and treatment planning for M3Ms with radiographic signs such as darkening of the roots, interruption of the radiopaque borders of the mandibular canal, or deviation of the mandibular canal and narrowing of the roots.

Risk factors for external root resorption of maxillary second molars associated with third molars

Purpose

This study aimed to evaluate the diagnostic performance of panoramic images compared to cone-beam computed tomography (CBCT) imaging for maxillary third molar (M3)-associated external root resorption (ERR), and to identify the risk factors of ERR on panoramic images.

Materials and Methods

The study population was composed of all patients who underwent panoramic imaging at Dankook University Dental Hospital from May to October 2019. In total, 397 cases of maxillary M3s in 247 patients (147 men and 100 women) were included. The diagnostic accuracy of ERR in panoramic images compared to CBCT images was evaluated using the chi-square test. To identify risk factors for ERR, dental records and panoramic findings were evaluated by logistic regression analysis.

Results

The diagnostic accuracy of ERR on panoramic images was 0.79 compared to CBCT images (P<0.05). Superimposition of M3s onto second molars (M2) was associated with an approximately 33 times higher risk of ERR than separated M3s (P<0.05). Impacted M3s showed a 5 times higher risk of ERR than erupted M3s (P<0.05).

Conclusion

ERR related to M3s is a common clinical condition, and superimposition of M3 onto M2 on panoramic images was the most important risk factor for ERR. It seemed that CBCT examinations for maxillary M3s might be indicated for ERR diagnosis especially if panoramic radiographs show superimposition of M3 onto M2. Impaction itself was also a risk factor, and it should be carefully examined.

Comparison of Digital OPG and CBCT in Assessment of Risk Factors Associated with Inferior Nerve Injury during Mandibular Third Molar Surgery

Background: Pre-operative radiographic assessment of the anatomical relationship between the roots of the mandibular third molar and the inferior alveolar nerve (IAN) is a must to minimize the risk of IAN injury during surgery. Objectives: To compare the radiographic signs of digital orthopantomogram (OPG) and cone-beam computed tomography (CBCT). An additional objective was to assess the cortex status between the mandibular canal and third molar on CBCT images in relation to the demographic characteristics, region (right or left side), and angulation of mandibular molar. Methodology: In this retrospective study, a total of 350 impacted mandibular third molars with a close relationship between the inferior alveolar canal (IAC) and impacted mandibular third molars on digital OPG were further referred for CBCT imaging for assessment of the position of the mandibular canal. The study was conducted between August 2018 and February 2020. Digital OPGs were evaluated for radiographic signs like interruption of the mandibular canal wall, darkening of the roots, diversion of the mandibular canal, and narrowing of the mandibular canal. The age and sex of patients, site of impacted third molar, Winter’s classification of mandibular third molar, position of IAC relative to impacted molar, and the radiographic markers of OPG were assessed for cortical integrity using CBCT. Chi square testing was applied to study the values of difference and binomial logistic regression was done to assess the factors associated with cortication. Statistical significance was set at p ≤ 0.05. Results: Among 350 patients, 207 (59.1%) were male and 143 (40.9%) were female with a mean age of 36.8 years. The most common OPG sign was interruption of white line, seen in 179 (51.1%) cases. In total, 246 cases (70.3%) showed an absence of canal cortication between the mandibular canal and the impacted third molar on CBCT images. Cortication was observed in all cases with a combination of panoramic signs which was statistically significant (p = 0.047). Cortication was observed in 85 (50.6%) cases where IAC was positioned on the buccal side, 11 (16.9%) in cases of inferiorly positioned IAC, and just 8 (7.6%) for cases of lingually positioned IAC which was statistically significant (p = 0.003). Statistically insignificant (p > 0.05) results were noted for cortex status in CBCT images with regards to the age, sex, site, and angulation of impacted third molars. Conclusion: CBCT imaging is highly recommended for those cases where diversion of the mandibular canal is observed on OPG and when the roots are present between canals.

Correlation of Panoramic Radiography, Cone-Beam Computed Tomography, and Three-Dimensional Printing in the Assessment of the Spatial Location of Impacted Mandibular Third Molars

The development of radiology, rapid prototyping techniques, and the increasingly common use of 3D printing in dentistry inspires the use of these techniques to improve diagnostic and therapeutic processes. This study aimed to conduct a retrospective comparative analysis of dental panoramic radiographs, cone-beam computed tomography, and 3D printing in preoperative assessment of the procedure’s difficulty. Thirty clinical cases with a high degree of difficulty were selected, and based on evaluation with CBCT, a virtual 3D model of the region of surgical procedure was created, which was then printed using a 3D printer. The comparative analysis included the linear measurements performed in dental panoramic radiographs, cone-beam computed tomography, and 3D models in a preoperative assessment of the degree of retention and difficulty of impacted mandibular third molars in the mandible. Linear measurements performed on dental panoramic radiographs were significantly lower than in cone-beam computed tomography and 3D models. No statistically significant differences were obtained in linear measurements between 3D models and cone-beam computed tomography images except for the measurement of the lingual lamina thickness; however, due to the insignificant differences in measurements, with a mean of only 80 µm, the elective procedure of removal of the impacted third molar in the mandible may be safe.

Is it possible to filter third molar cases with panoramic radiography in which roots surround the inferior alveolar canal? A comparison using cone-beam computed tomography

Inferior alveolar nerve (IAN) entrapment in third molar (M3) roots bears a significant risk for nerve injury. The aim of this study was to identify specific panoramic radiographic (PR) signs that can reliably identify IAN entrapment (IANE) root conformations. In a retrospective case-control study, 10 IANE and 218 non-IANE third molar risk cases were examined by PR and CBCT. The collected data included "classic" specific high-risk panoramic signs, number of M3 roots, extent of inferior alveolar canal (IAC)-root tip overlap, rotated position of M3 and impaction pattern. After bivariate analysis, sensitivity, specificity, positive and negative predictive values, positive likelihood ratios (LR+) and accuracy (area under the curve [AUC]) were calculated for the most significant predictive variables. Interruption of both cortical lines (LR⁺: 43.6; AUC: 96.0%) and upward diversion of the IAC (LR⁺: 36.3; AUC: 96.5%) were the most accurate single signs indicating IANE. Upward diversion combined with root darkening and interruption of the IAC (AUC: 97.4%) and the combination of darkening with interruption and with a rotated M3 (LR⁺:130.8; AUC: 97.8%) were the most accurate combinations predicting IANE. IANE may be correctly filtered with PR when focusing on the signs of upward diversion, darkening, interruption and rotated M3 position, especially in cases involving their multiple (≥3) presence. CBCT evaluation is highly recommended in these cases before partial and total tooth removals.

Radiographic Position of Impacted Mandibular Third Molars and Their Association with Pathological Conditions

Objectives

This study aimed to assess the radiographic position of impacted mandibular third molars (IMTMs) and their association with pathological conditions.

Materials and Methods

The impaction depth, relationship with ramus, and angulation of 1600 IMTMs and their association with 2^nd molar distal caries and root resorption, pathological conditions, and proximity to the mandibular canal were evaluated on panoramic radiographs. The IMTM position was determined based on the depth of impaction according to the Pell and Gregory classification, relationship with ramus according to the Pell and Gregory classification, and angulation according to the Winter's classification. The classical and Bayesian logistic regressions were applied to analyze the effect of IMTM position on the associated complications using the odds ratio (OR) and 95% confidence interval (credible interval for Bayesian models). Two-tailed P value < 0.05 was considered statistically significant.

Results

Of 1600 IMTMs evaluated in this study, 195 (12.2%), 252 (15.8%), and 119 (7.4%) had caused second molar distal caries, second molar root resorption, and pathological lesions, respectively, and 872 (54.5%) had contact with the mandibular canal. Impaction angulation was a risk factor for second molar distal caries (maximum OR = 5.01, 95% CI: 3.12-8.18). Changed angulation and greater impaction depth were the risk factors for second molar root resorption (minimum OR = 1.64, 95% CI: 0.58-4.02). Decreased distance between the ramus and distal side of the second molar was a risk factor for associated pathological lesions (minimum OR = 2.73, 95% CI: 1.79-4.25). Mesioangular and horizontal angulations and greater impaction depth were the risk factors for contact with the mandibular canal (maximum OR = 3.44, 95% CI: 2.6-4.57 and minimum OR = 1.3, 95% CI: 094-1.8).

Conclusions

The frequency of complications associated with IMTMs was low, but considerable. The occurrence of these conditions might be affected by the impaction position. Thus, regular follow-ups are recommended in order to be able to surgically intervene when the first signs of pathologies arise.

Alternative Approach to Prevent Inferior Alveolar Nerve Injury in Lower Third Molar Surgery: A Pilot Study on Coronectomy

Context:

Injury to inferior alveolar nerve (IAN) in lower third molar (L3M) surgery may lead to unpleasant sensation or anesthesia of lower lip. Considering the quality of life of the patient and the litigations faced by the dentist, alternative treatment approaches to odontectomy have been studied by various researchers. Coronectomy is one such option to prevent the nerve injury.

Aims:

The aim of this study was to assess the efficacy of coronectomy to reduce nerve injury during L3M surgery in high-risk cases as per radiological signs.

Settings and Design:

A pilot study was conducted in the oral surgery department of Rajah Muthiah Dental College, Annamalai Nagar, Chidambaram, India to evaluate coronectomy and its usefulness.

Materials and Methods:

Sixty-five patients who satisfied the inclusion and exclusion criteria for coronectomy were included in the study. The patients were followed up to 1-year period.

Statistical Analysis Used:

Descriptive statistics was used.

Results:

None of the patients in the study group had IAN impairment.

Conclusions:

Coronectomy is a safe alternative for complete odontectomy in high-risk L3M surgery cases. Root migration, infection, and need for second surgery are potential complication. Further studies with more samples and variables need to be performed.

Reliability of Orthopantamogram in Lower Third Molar Surgery: Inter- and Intra-observer Agreement

Context:

The evaluation of relationship between the roots of impacted lower third molar (IL3M) and inferior alveolar nerve injury (IAN) with orthopantamogram (OPG) is mandatory before performing de-impaction surgery. An investigation is considered reliable if it can be reproduced by various examiners. Assessment of OPG is subjective and varies among examiners. OPG is reliable to clinicians if the interpretation is not a product of guess work.

Aim:

The aim of this study was to evaluate the magnitude of agreement among oral surgeons and oral radiologist in observing intimate relationship between IL3M and mandibular canal.

Materials and Methods:

OPGs were evaluated by two oral surgeons and one oral radiologist for nerve root relationship. All the three were from different institutions with 10–15 years of experience. The three observers were blinded from each other’s findings. A total of 127 OPGs were evaluated for inter-observer agreement. Fifty OPGs were evaluated after 60 days for intra-observer agreement.

The agreement was evaluated based on Cohen’s κ statistics.

Results:

Our results denote that the interpretation of OPG among specialists is not in good agreement. We suggest development of methods to standardize evaluation of OPG and the exposure technique to improve inter-observer agreement among the dental specialists.

Positional Differences of the Mandibular Canal in Relation to Permanent Mandibular First Molars with Eruption Disturbances in Children

Eruption disturbances in permanent mandibular first molars (PM1s) are uncommon. This retrospective study aimed to investigate differences in the position of the mandibular canal in relation to PM1s, with or without, eruption disturbances. Panoramic and cross-sectional views were reconstructed from cone-beam computed tomography imaging of children with PM1 eruption disturbances. Distances from the most inferior margin of the mandible to the center of the mandibular canal (M-C) and from the outer margin of the lingual cortex to the center of the mandibular canal (L-C) were measured for normally erupted PM1s (normal group) and for PM1s with eruption disturbances (ED group) and compared using independent t-tests. The mean M-C was significantly shorter in the ED group (4.86 ± 1.07 mm) than in the normal group (6.56 ± 1.06 mm) (p < 0.05). The mean L-C was also significantly shorter in the ED group (2.74 ± 0.74 mm) than in the normal group (3.09 ± 0.71 mm) (p < 0.05). This study demonstrated that the mandibular canal tended to be positioned more inferiorly in relation to PM1s with eruption disturbances than normally erupted PM1s in children. Clinicians should be aware of this positional deviation when managing children with PM1 eruption disturbances.

Comparison of 3 deep learning neural networks for classifying the relationship between the mandibular third molar and the mandibular canal on panoramic radiographs

OBJECTIVE

The aim of this study was to compare time and storage space requirements, diagnostic performance, and consistency among 3 image recognition convolutional neural networks (CNNs) in the evaluation of the relationships between the mandibular third molar and the mandibular canal on panoramic radiographs.

STUDY DESIGN

Of 600 panoramic radiographs, 300 each were assigned to noncontact and contact groups based on the relationship between the mandibular third molar and the mandibular canal. The CNNs were trained twice by using cropped image patches with sizes of 70 × 70 pixels and 140 × 140 pixels. Time and storage space were measured for each system. Accuracy, sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC) were determined. Intra-CNN and inter-CNN consistency values were calculated.

RESULTS

Time and storage space requirements depended on the depth of CNN layers and number of learned parameters, respectively. The highest AUC values ranged from 0.88 to 0.93 in the CNNs created by 70 × 70 pixel patches, but there were no significant differences in diagnostic performance among any of the models with smaller patches. Intra-CNN and inter-CNN consistency values were good or very good for all CNNs.

CONCLUSIONS

The size of the image patches should be carefully determined to ensure acquisition of high diagnostic performance and consistency.

Preoperative imaging of the inferior alveolar nerve canal by cone-beam computed tomography and 1-year neurosensory recovery following mandibular setback through bilateral sagittal split ramus osteotomy: a randomized clinical trial

Objectives

One of the most common complications of bilateral sagittal split ramus osteotomy (BSSRO) is neurosensory impairment of the inferior alveolar nerve (IAN). Accurate preoperative determination of the position of the IAN canal within the mandible using cone-beam computed tomography (CBCT) is recommended to prevent IAN dysfunction during BSSRO and facilitate neurosensory improvement after BSSRO.

Materials and Methods

This randomized clinical trial consisted of 86 surgical sites in 43 patients (30 females and 13 males), including 21 cases (42 sides) and 22 controls (44 sides). Panoramic and lateral cephalographs were obtained from all patients. In the experimental group, CBCT was also performed from both sides of the ramus and mandibular body. Neurosensory function of the IAN was subjectively assessed using a 5-point scale preoperatively and 7 days, 1 month, 3 months, 6 months, and 12 months post-surgery. Data were analyzed using Fisher's test, Spearman's test, t-test, linear mixed-model regression, and repeated-measures ANCOVA (α=0.05, 0.01).

Results

Mean sensory scores in the control group were 1.57, 2.61, 3.34, 3.73, and 4.20 over one year and were 1.69, 3.00, 3.60, 4.19, and 4.48 in the CBCT group. Significant effects were detected for CBCT intervention (P=0.002) and jaw side (P=0.003) but not for age (P=0.617) or displacement extent (P=0.122).

Conclusion

Preoperative use of CBCT may help surgeons to practice more conservative surgery. Neurosensory deficits might heal faster on the right side.

Assessment of the reliability of radiographic signs on panoramic radiographs to determine the relationship between mandibular third molars and the inferior alveolar canal

OBJECTIVE

To assess the reliability of radiographic signs of the relationship between impacted mandibular third molars (IMTMs) and the inferior alveolar canal (IAC), and the vertical relationship between IMTM and IAC on panoramic radiographs (PRs) as risk indicators for IAC exposure during extraction.

STUDY DESIGN

Seven radiographic signs regarding the appearance of roots and the IAC were assessed as present or absent on PRs. The vertical relationship between IMTM and the IAC was divided into 3 levels. The correlation between radiographic data and IAC exposure during extraction was analyzed by using χ² statistics and logistic regression analysis.

RESULTS

In total, 198 IMTMs were examined. In 46 cases (23.2%), the IAC was exposed during extraction. Four radiographic signs-darkening of the root, narrowing of the root, narrowing of the IAC, and diversion of the IAC-were associated with IAC exposure (P < .05). Concurrence of 2 or more of 7 radiographic signs increased the risk of IAC exposure (P < .001). The vertical relationship between IMTM and the IAC was found to be a risk indicator for IAC exposure (P < .001). No significant correlation was found between IAC exposure and inferior alveolar nerve damage (P = .148).

CONCLUSIONS

Panoramic radiography is useful for assessing the risk of IAC exposure during IMTM extraction.

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.

Diversion of the mandibular canal: Is it the best predictor of inferior alveolar nerve damage during mandibular third molar surgery on panoramic radiographs?

Purpose

The aim of this study was to evaluate the relationship between the mandibular canal and impacted mandibular third molars using cone-beam computed tomography (CBCT) and to compare the CBCT findings with signs on panoramic radiographs (PRs).

Materials and Methods

This retrospective study consisted of 200 mandibular third molars from 200 patients who showed a close relationship between the mandibular canal and impacted third molars on PRs and were referred for a CBCT examination of the position of the mandibular canal. The sample consisted of 124 females and 76 males, with ages ranging from 18 to 47 years (mean, 25.75±6.15 years). PRs were evaluated for interruption of the mandibular canal wall, darkening of the roots, diversion of the mandibular canal, and narrowing of the mandibular canal. Correlations between the PR and CBCT findings were statistically analyzed.

Results

In total, 146 cases (73%) showed an absence of canal cortication between the mandibular canal and impacted third molar on CBCT images. A statistically significant relationship was found between CBCT and PR findings (P<0.05). The absence of canal cortication on CBCT images was most frequently accompanied by the PR sign of diversion of the mandibular canal (96%) and least frequently by interruption of the mandibular canal wall (65%).

Conclusion

CBCT examinations are highly recommended when diversion of the mandibular canal is observed on PR images to reduce the risk of mandibular nerve injury, and this sign appears to be more relevant than other PR signs.

Orthopantomography and Cone-Beam Computed Tomography for the Relation of Inferior Alveolar Nerve to the Impacted Mandibular Third Molars

Context:

Relation of inferior alveolar nerve to the impacted mandibular third molars (IMTMs).

Aims:

The aim of this study was to assess the reliability of seven specific radiographic signs of mandibular third molar root that are observed on orthopantomography (OPG) and to predict the proximity and the absence of corticalization between the mandibular canal and IMTM root on cone-beam computed tomography (CBCT) images.

Settings and Design:

The present study was conducted in the Department of Oral and Maxillofacial Surgery, Raja Rajeswari Dental College and Hospital.

Subjects and Methods:

Data set of 30 panoramic images was retrieved between the year of 2015 and 2016 indicated for extraction of lower third molars. The sample consisted of 30 individuals, who underwent preoperative radiographic evaluation before the extraction of impacted mandibular third molars (IMTM). Patients aged above 18 years with any of the seven specific signs observed on the panoramic radiograph which includes darkening, deflection, narrowing of roots, bifid root apex, diversion, narrowing of canal and interruption in the white line of the canal were included in the study. If any of the above mentioned seven specific sign were present, the patient was subjected to CBCT. On the CBCT images, the canal was traced in three planes. The acquired images were assessed for the presence or absence of corticalization.

Statistical Analysis Used:

Descriptive and inferential statistical analyses were used. Proportions were compared using the Chi-square test and Student's t-test.

Results:

Among the 4 subjects, diagnosed with an absence of corticalization, patients with isolated darkening of root P = 0.001 and patients with isolated interruption in white line P = 0.69. Patients with darkening of root in association with interruption in white lines on OPG showed the absence of corticalization on CBCT findings P = 0.001, respectively.

Conclusions:

This study showed the poor reliability of radiographic signs seen on OPG on predicting the proximity of third mandibular root with mandibular canal related to CBCT finding. Four were diagnosed with the absence of corticalization in CBCT findings.

Evaluation of mandibular odontogenic keratocyst and ameloblastoma by panoramic radiograph and computed tomography

OBJECTIVES:

The purpose of this study was to describe and compare the main imagenological features of mandibular ameloblastomas and odontogenic keratocyst (OKC) using panoramic radiograph (PR) and CT.

METHODS:

The sample consisted of nine cases of ameloblastomas and nine cases of OKC. PR and CT images were analyzed according to shape, internal structure, borders, associated unerupted tooth, root resorption, expansion and perforation of cortical bones.

RESULTS:

PR evaluation allowed the identification of the lesion's location, presence of sclerosis in the periphery, presence of associated non-erupted tooth and expansion of the mandible's lower border cortical bone. CT was more accurate than PR in the assessment of the lesion shape, presence of inner bone septa, root resorption, buccolingual expansion and rupture of cortical bone. Most cases of ameloblastoma and OKC presented buccolingual expansion and erosion of cortical bone. Only ameloblastomas showed tooth root resorption.

CONCLUSIONS:

Although PR is very helpful and widely used, CT provides more precise information on buccolingual expansion, calcification, bone septa, perforation of cortical bones and tooth resorption, features that are frequently underdescribed in the literature, particularly in OKC.

Accuracy of panoramic radiographic predictor signs in the assessment of proximity of impacted third molars with the mandibular canal

OBJECTIVES

This study aimed to validate the accuracy of panoramic radiographic risk signs through detection of presence or absence of corticalization between an impacted mandibular third molar and the inferior alveolar canal on cone beam computed tomography (CBCT).

METHODS

This retrospective study analyzed 210 impacted mandibular third molars from 135 patients (aged 17-51 years) who showed one or more of the seven previously established panoramic radiographic risk signs of inferior alveolar nerve exposure. These patients were referred for CBCT examination. Three-dimensional images were used to assess the canal position relative to the third molar, the proximity between the canal and third molar, and third molar angulation. The correlation of panoramic findings and CBCT was evaluated using a Chi-square test.

RESULTS

Panoramic findings of interruption of inferior alveolar canal wall, isolated or combined with one of these signs (darkening of third molar roots, narrowing of canal, and diversion of canal); darkening of the roots; and narrowing of canal were significantly correlated with direct contact between the inferior alveolar canal and impacted third molars on CBCT (P < 0.001).

CONCLUSION

Preoperative CBCT is recommended for cases showing interruption of canal wall; darkening of the roots or narrowing of the canal; or association between interruption and narrowing, diversion, or darkening of roots in a panoramic view. This study evaluated the risk relationship between the inferior alveolar nerve and impacted mandibular third molars, with the aim of reducing the occurrence of postoperative injury to the inferior alveolar nerve.

The Effect of Original and Invert Enhanced Panoramic Modality on the Assessment of the Relationship Between the Maxillary Posterior Roots and the Maxillary Sinus Floor

Background:

Having knowledge about the anatomical and pathological relationship between the maxillary posterior root tip and the maxillary sinus floor is very significant for preoperative treatment planning.

Aims and Objectives:

The purpose of the present study was to compare the accuracy of original panoramic radiographs and digital panoramic images over cone beam computed tomography (CBCT) images in evaluating the relationship between the maxillary posterior teeth and the maxillary sinus floor, and to verify the accuracy of the signs of the relationship between the roots of the maxillary posterior teeth and maxillary sinus on the panoramic radiographs over CBCT images.

Materials and Methods:

From 106 subjects (47 males and 59 females; mean age = 39 years; range = 18-67 years) referred to our university, a pair of panoramic and CBCT images was selected for further analysis. The relationship between the maxillary posterior teeth, the maxillary sinus, and panoramic radiography signs (root projection into the sinus, interruption of the maxillary sinus floor cortex, absence of lamina dura, darkening of the root apex, and curvature of the sinus floor on the root apex) associated with the protrusion of root apexes into the sinus was evaluated.

Results:

The P values of the data obtained from the original and invert enhanced panoramic images were .53 and .52, respectively, and there was no statistically significant difference in the accuracy of the 2 methods ( P > .05).

Conclusion:

The root projection into the sinus is an indicative sign of root protrusion into the sinus on CBCT.

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.

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.

Analyses of anatomical relationship between mandibular third molar roots and variations in lingual undercut of mandible using cone-beam computed tomography

Background/purpose

Anatomical features of the lingual undercut region is a potential factor that might increase the risk of displacement of a tooth or fragment. The aim of this study was to report the normal anatomical relationship of impacted lower third molar roots to the lingual cortex and soft tissues of mandible and anatomical variations of lingual balcony in the impacted third molar region.

Materials and methods

One hundred impacted third molars (54 males, 46 females) from 65 (31 men, 34 women) patients were evaluated for this study using cone-beam computed tomography. Three measurements [bone thickness, angle (Ang) 1 and Ang 2] were recorded on the coronal section slices of cone-beam computed tomography images; in these images, the impacted third molar root was closest to the lingual soft tissues.

Results

The average distance between the tooth root and the lingual outer cortical bone layer (bone thickness) was 1.03 mm. The averages of Ang 1 and Ang 2 were 140.61° and 153.44°. Ang 1 and Ang 2 of female patients were larger than those of male patients.

Conclusion

The narrow angulation of the lingual balcony region and the relationship between roots and lingual soft tissues should be noted to avoid undesirable complication of displacement of a tooth or fragment into sublingual, submandibular, and pterygomandibular spaces. There was no relation in the floor of the mouth between the position of the impacted third molar roots and different lingual undercut angulation variations.

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.

Accuracy of Panoramic Radiograph in Assessment of the Relationship Between Mandibular Canal and Impacted Third Molars

Background:

The relationship between impacted mandibular third molar and mandibular canal is important for removal of this tooth. Panoramic radiography is one of the commonly used diagnostic tools for evaluating the relationship of these two structures.

Objectives:

To evaluate the accuracy of panoramic radiographic findings in predicting direct contact between mandibular canal and impacted third molars on 3D digital images, and to define panoramic criterion in predicting direct contact between the two structures.

Methods:

Two observers examined panoramic radiographs of 178 patients (256 impacted mandibular third molars). Panoramic findings of interruption of mandibular canal wall, isolated or with darkening of third molar root, diversion of mandibular canal and narrowing of third molar root were evaluated for 3D digital radiography. Direct contact between mandibular canal and impacted third molars on 3D digital images was then correlated with panoramic findings. Panoramic criterion was also defined in predicting direct contact between the two structures.

Results:

Panoramic findings of interruption of mandibular canal wall, isolated or with darkening of third molar root were statistically significantly correlated with direct contact between mandibular canal and impacted third molars on 3D digital images (p < 0.005), and were defined as panoramic criteria in predicting direct contact between the two structures.

Conclusion:

Interruption of mandibular canal wall, isolated or with darkening of third molar root observed on panoramic radiographs were effective in predicting direct contact between mandibular canal and impacted third molars on 3D digital images. Panoramic radiography is one of the efficient diagnostic tools for pre-operative assessment of impacted mandibular third molars.

Comparison of panoramic radiography and CBCT to identify maxillary posterior roots invading the maxillary sinus

OBJECTIVES

Given the limitations of panoramic radiography for assessing topographic relationship of maxillary teeth with sinus floor, the purpose of this study was to assess signs on panoramic radiography that could predict root protrusion into the sinus.

METHODS

A total of 46 individuals (330 maxillary posterior teeth) who underwent panoramic radiography and CBCT were enrolled. The relationship between the posterior teeth and the maxillary sinus and panoramic radiography signs (projection of the root apices, interruption of the maxillary sinus floor, lamina dura, darkening in the root apices, and superiorly curving sinus floor enveloping the associated tooth root) associated with protrusion of root apices into the sinus were evaluated.

RESULTS

There were differences between the imaging modalities about the positioning of the root apices regarding the sinus (p < 0.05). Only the projecting of the root apices and the interruption of the sinus floor on panoramic radiography were predictors for the root protrusion (p < 0.05). No significant association was observed for the other panoramic radiography signs (p > 0.05).

CONCLUSIONS

The root projection into the sinus and the interruption of the sinus floor are indicative signs of root protrusion into the sinus on CBCT.

Potential reformatting errors in cone-beam computed tomography for dentoalveolar surgery: a cautionary tale

We describe the removal of a lower second molar tooth in which preoperative cone-beam computed tomography (CBCT) showed that the inferior alveolar nerve (IAN) was encased in the distal apex of the root of the tooth. During operation the nerve was found to be entirely separate from the apex of the root and not involved. With the wider use of CBCT in the treatment planning of dentoalveolar surgery, this case represents a cautionary tale to the clinician on reliance on clinical imaging and software in guiding the decision making process.

Role of cone-beam computed tomography in the evaluation of a paradental cyst related to the fusion of a wisdom tooth with a paramolar: A rare case report

Fusion is an abnormality of tooth development defined as the union of two developing dental germs, resulting in a single large dental structure. This irregular tooth morphology is associated with a high predisposition to dental caries and periodontal diseases. As a result of recurring inflammatory periodontal processes, disorders such as periodontal pocket, pericoronitis, and paradental cysts may develop. A rare mandibular anatomic variation is the retromolar canal, which is very significant for surgical procedures. The fusion of a paramolar and mandibular third molar associated with a paradental cyst co-occurring with the presence of a retromolar canal is rare, and the aim of the present study is to describe the evaluation of this anatomical configuration using cone-beam computed tomography.

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.

Validity of the vertical tube-shift method in determining the relationship between the mandibular third molar roots and the inferior alveolar nerve canal

OBJECTIVES

To assess the validity of the vertical tube-shift method using intraoral periapical radiography (IOPAR) for determining the relationship between the mandibular third molar roots and the inferior alveolar nerve (IAN) canal in comparison with cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Fifty impacted mandibular third molars were analyzed using the IOPAR vertical tube-shift method and CBCT. The relationship of the IAN canal to the impacted mandibular third molar was recorded as buccal, lingual or in line with the apex and was compared with CBCT findings. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the vertical tube-shift method in depicting the relationship (buccal/lingual/in line with the apex) of the IAN canal to the third molar root apex was calculated.

RESULTS

The sensitivity and specificity PPV and NPV of the IOPAR vertical tube-shift technique was found to be highest for a lingual relationship (100%) followed by buccal (94.4%, 92.3%, 97.1%, and 85.7%) and in line with the apex relationship (88.9%, 95.0%, 80.0%, and 97.4%) of the IAN canal with the third molar root apex, respectively. A statistically significant association was observed between the IOPAR vertical tube-shift method and the CBCT with a P-value <0.01.

CONCLUSION

The vertical tube-shift method can be used as an effective diagnostic tool in assessing the relationship of the IAN canal to the third molar root apex with high sensitivity, specificity, PPV, and NPV.

Diagnostic accuracy of cone-beam CT compared with panoramic images in predicting retromolar canal during extraction of impacted mandibular third molars

OBJECTIVES

The clinical significance of the existence of a retromolar canal and of its neurovascular content is not yet clear.The aim of the present study was to assess the visibility, diameter and course of the mandibular retromolar canal (MRC) using cone beam computed tomography (CBCT) scan--had been taken for pre-operative radiographic evaluation of impacted mandibular third molars--compared to panoramic radiographs.

STUDY DESIGN

Subjects eligible for study enrollment were those who underwent preoperative CBCT scan for the extraction of impacted mandibular third molars were determined to be extremely close to the mandibular canal on panoramic radiographs. Radiographs were screened for the presence and course of retromolar canals, and linear measurements.

RESULTS

947 hemimandibles in 632 patients were examined.A total of 253 MRCs (144 left, 109 right) were detected with CBCT images (26.7%). Only 29 of these canals were also seen on the corresponding panoramic radiographs. Most MRCs had a vertical course (type VI, 28.46%), followed by slightly curved (type I, 26.09%). The visibility of the MRC on the OPGs, according to the increase in the diameter, was not statistically significant for both sides (p >.05).Statistically difference were found for the width at the point of origin from the mandibular canal (p: .037), the mean distance from the MRC to the second molar (p: .042) and height of MRC when compared the gender.

CONCLUSIONS

The findings suggest that the MRC isn't a rare anatomical structure. This study therefore clearly establishes the incidence and importance of the MRC. The detection of the presence of the MRC using CBCT may be crucial for extraction of mandibular third molars.

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.

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.

Reproducibility of mandibular third molar assessment comparing two cone beam CT units in a matched pairs design

The aim of this study was to evaluate the reproducibility of the third molar assessment, comparing five observers and two cone beam CT (CBCT) units. 28 patients, each with two impacted mandibular third molars, were included. Each patient was randomly examined with a Scanora(®) 3D (Soredex, Helsinki, Finland) CBCT unit in one mandibular third molar region and with a Cranex(®) 3D (Soredex) CBCT unit in the other region. Five observers with varying CBCT experience assessed all third molars and recorded the following variables: number and morphology of the roots, relation to the mandibular canal in two directions, shape of the canal and whether there was a direct contact between the roots of the molar and the mandibular canal. The radiographic assessments were compared pairwise among all observers for all variables. Wilcoxon's signed-rank test was used to test the differences in observer accordance percentages among the recorded variables in the images from the two units, and kappa statistics expressed interobserver reproducibility. The mean percentages for observer accordance ranged from 65.4 to 92.9 for Scanora 3D and 60.3 to 94.8 for Cranex 3D. There was no significant difference between the observer accordance in the two CBCT units (p > 0.05), except for assessing root flex in the mesiodistal direction, for which the observer accordance was higher for Scanora 3D (p < 0.05). Kappa values ranged from 0.1 to 1.0 for Scanora 3D and from 0.2 to 0.9 for Cranex 3D. For the variable "direct contact", the interobserver reproducibility was excellent for the two trained radiologists. The two units had almost similar interobserver reproducibility for mandibular third molar assessment. Observer variation existed, and experienced radiologists demonstrated the highest interobserver reproducibility for canal-related variables.