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

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.

Pathologic conditions associated with impacted third molars: A retrospective study of panoramic radiographs in a Southern Brazilian population

Purpose

This study investigated the prevalence of developmental and acquired pathologic conditions associated with impacted third molars (3Ms) in a Southern Brazilian population and evaluated whether demographic and tooth characteristics were correlated with the presence of bone or tooth lesions.

Materials and Methods

Panoramic radiographs were assessed for developmental (bone-related) or acquired (tooth-related) pathoses associated with impacted upper or lower 3Ms. Data on tooth positioning, tooth development, and patient demographics were collected. A trained, calibrated postgraduate student evaluated all images. Binary and multivariate logistic regression models were used to assess associations between outcomes and the demographic and radiographic variables. The threshold for statistical significance was set at 5% (P<0.05).

Results

The sample comprised panoramic radiographs from 2054 patients, predominantly female (59.2%), with a mean age of 27.2 ± 11.5 years. Overall, 4066 impacted 3Ms were evaluated, revealing 471 (11.6%) developmental and 710 (17.5%) acquired pathoses. Among the developmental pathoses, 460 (95.2%) were indicative of dentigerous cysts. Male sex, lower 3M location, vertical or distoangular positioning, and incomplete root formation were associated with an elevated likelihood of developmental pathology. Lower tooth position, complete root formation, and partial eruption were linked to an increased probability of an acquired pathology in the third or second molar.

Conclusion

The prevalence of pathologic conditions associated with impacted 3Ms was low. Male sex, lower 3M placement, horizontal or distoangular positioning, and incomplete root formation were associated with developmental pathoses, while lower tooth position, complete root formation, and partial eruption were related to acquired pathoses.

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.

Conduction of Third Molar Extraction with the Presence of Retromolar Canal: A Case Report

Introduction:

The retromolar canal is a structure rarely identified in clinical practice. The content of this canal is composed of nerves, arteries and venous plexus that give innervation and irrigation to the third molar region and the vestibular mucosa of molars and lower premolars. Thus, knowledge of the presence of this structure is important in dental procedures, due to the complications that damage to this structure can cause.

Methods:

In this report, a 19-year-old patient sought dental care at a clinic, Dentistry course at the Federal University of Santa Maria for the extraction of third molars due to hygiene difficulties. On radiographic examination, a retromolar canal was identified at the distal of the left mandibular third molar. With the identification of this structure, preventive measures were performed during the procedure to avoid complications.

Results:

With adequate planning and prevention measures, the trans and postoperative periods occurred without any complications.

Conclusion:

The foramen and the retromolar canal may occasionally appear in the clinic radiographic routine of the Dentist, and the professional should be attentive to the management of these anatomical structures during surgical procedures to avoid accidents and complications.

Positive Predictive Value of Panoramic Radiography for Assessment of the Relationship of Impacted Mandibular Third Molars with the Mandibular Canal Based on Cone-Beam Computed Tomography: A Cross-Sectional Study

The aim of the present study was to assess the positive predictive value (PPV) of panoramic radiographic signs in the assessment of the relationship between impacted mandibular third molars (IMTMs) and the mandibular canal (MC). This cross-sectional study was conducted by reviewing 102 cone-beam computed tomography (CBCT) and panoramic radiographs of patients with IMTMs and radiographic signs of the contact of the IMTMs with the MC on panoramic radiographs (i.e., root apex darkening and interference with the white line). A positive relationship of the IMTM roots with the MC based on CBCT findings was recorded as the gold standard. The PPV of panoramic radiographic signs was calculated for the detection of the relationship of the IMTM root with the MC. The IMTMs were in contact with the MC on CBCT scans in 90.1% of the cases. The PPV of root apex darkening and the interference with the white line was found to be 89.09% (95% CI: (77.75, 95.88)) and 91.48% (95% CI: (79.62, 97.63)), respectively. The MC had a buccal position in 63.7%, and a lingual position in 35.2%, of the cases. The contact of IMTMs with the MC was more commonly seen in patients with a lingual position (100% of the samples). The IMTM root apex darkening and interference with the white line of the MC on panoramic radiographs had a high PPV for determination of the contact of IMTMs with the MC. Thus, presence of the above-mentioned risk factors indicates the need for subsequent 3D radiographic assessments.

The association of mandibular third molar impaction with the dental and periodontal lesions in the adjacent second molars

BACKGROUND

It is a consensus that symptomatic impacted mandibular third molars (MTMs) need to be removed. Although the prophylactic extraction of asymptomatic impacted MTMs remains controversial. This study aims to investigate the effects of MTMs on themselves and adjacent teeth pathophysiology and provide the evidence for prophylactic extraction of impacted MTMs.

METHODS

A retrospective study of panoramic radiographs of patients visited the Affiliated Stomatology Hospital of Guangzhou Medical University from April 2014 to May 2018 was conducted to investigate the dental and periodontal lesions in MTMs and adjacent mandibular second molars (MSMs), as well as the correlation of tooth lesion severity with patient age.

RESULTS

Among the 2650 impacted MTMs, 6.98% dental lesions and 37.81% periodontal lesions were found, as well as 24.63% dental lesions and 35.30% periodontal lesions in the distal of adjacent MSMs. 9.27%, 2.02%, 0.47%, and 13.33% dental lesions and 48.81%, 17.31%, 5.19%, and 10% periodontal lesions were observed in MTMs with mesioangular, horizontal, inverted and distoangular impaction types, respectively. For the adjacent MSMs, 31.98%, 11.82%, 1.94%, and 13.33% distal dental lesions and 45.74%, 16.95%, 2.91%, and 23.33% distal periodontal lesions were found in mesioangular, horizontal, inverted and distoangular impaction types, respectively. In mesioangular MTMs, the severity of the distal dental and periodontal lesions in the adjacent MSMs showed a high-positive correlation with patient age (P < 0.05) CONCLUSION: Early prophylactic extraction of MTMs with mesioangular-impaction and close monitoring of MTMs with horizontal/inverted-impaction could prevent impacted MTMs-associated lesions in MTMs/MSMs.

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.

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.

External root resorption of second molars caused by impacted third molars: an observational study in panoramic radiographs

Abstract Objective This research investigate the presence of external root resorption (ERR) in second molars caused by impacted third molars in panoramic radiographs, relating to the position of third molars according to classification of Winter, Pell and Gregory. Material and method A cross-sectional, retrospective study using panoramic radiographs obtained from January 2014 to December 2015. The inclusion criterion was the presence of a second molar adjacent to an impacted third molar. Data were analyzed using descriptive and inferential statistics. Pearson's Chi-Square Test and Fisher's Exact Test (p≤0.05) were performed. Result The sample consisted of 584 panoramic radiographs, 356 (60.95%) of women, and 228 (39.05%) of men, the mean age was 25.31 years. The prevalence of ERR was 12.5%, and the group of 14-24 year olds was the most affected (p = 0.46). The presence of ERR was statistically higher in the mandible (42.1%) with p=0.01. The ERR located in the cervical (57.1%) and medium (58.8%) thirds was proportionally higher in the teeth with B2 (p=0.02) and mesio-angular positions (p=0.26). Conclusion The prevalence of ERR in second molars, caused by impacted third molars, was shown to be similar to results found in the literature, with no gender preference, this affects young patients, occurring frequently in mandible teeth, and presents greater severity in the cervical and middle thirds. The B2 and mesio-angular positions were more prone to ERR.