Differences between panoramic and Cone Beam-CT in the surgical evaluation of lower third molars

Preoperative evaluation of lingual cortical plate thickness and the anatomical relationship of the lingual nerve to the lingual cortical plate via 3T MRI nerve-bone fusion

OBJECTIVES

To evaluate the reliability of 3T MRI nerve-bone fusion in assessing the lingual nerve (LN) and its anatomical relationship to the lingual cortical plate prior to the impacted mandibular third molar (IMTM) extraction.

METHODS

The MRI nerve and bone sequences used in this study were 3D T2-weighted fast field echo (3D-T2-FFE) and fast field echo resembling a CT using restricted echo-spacing (FRACTURE), respectively. Both sequences were performed in 25 subjects, and the resulting 3D-T2-FFE/FRACTURE fusion images were assessed by 2 independent observers. Semi-quantitative analyses included assessments of overall image quality, image artefacts, nerve continuity, and the detectability of 5 intermediate points (IPs). Quantitative analyses included measurements of the lingual cortical plate thickness (LCPT), vertical distance (V1* and V2*), and the closest horizontal distance (CHD) between the LN and the lingual cortical plate. Reliability was evaluated using weighted Cohen's kappa coefficient (κ), intraclass correlation coefficient (ICC), and Bland-Altman plots. Differences in LCPT between 3D-T2-FFE/FRACTURE fusion images and cone-beam computed tomography (CBCT) were compared using independent samples t-tests or Mann-Whitney U tests.

RESULTS

The fusion images demonstrated that the LN continuity score was 3.00 (1.00) (good), with 88% (44/50) of LNs displayed continuously at the IMTM level. Intra-reader agreement for nerve continuity was moderate (κ = 0.527), as was inter-reader agreement (κ = 0.428). The intra-reader and inter-reader agreement for LCPT measurements at the neck, mid-root, and apex of the IMTM were all moderate (ICC > 0.60). Intra-reader agreements for V1*, V2*, and CHD were moderate to excellent (ICC = 0.904, 0.967, and 0.723, respectively), and inter-reader agreements for V1*, V2*, and CHD were also moderate to excellent (ICC = 0.948, 0.941 and 0.623, respectively). The reliability of LCPT measurements between 3D-T2-FFE/FRACTURE fusion and CBCT was moderate (ICC = 0.609-0.796).

CONCLUSIONS

The 3D-T2-FFE/FRACTURE fusion technique demonstrated potential feasibility for the identification of the LN and its relationship to the lingual cortical plate, as well as for the measurement of LCPT. This study has generated a dataset that is capable of simultaneously defining the LN and LCPT.

Stepwise multi-stage resection technique for surgical extraction of a partially erupted mandibular third molar with inferior alveolar nerve entrapment: a case report

The removal of lower third molars is one of the most common surgical procedures in routine dental practice. However, perforation of the mandibular third molars by the inferior alveolar nerve (IAN) is a rare occurrence. These cases are considered to carry a heightened risk of IAN injury due to the nerve being entrapped within the tooth. This case report details the experience of a 43-year-old female who visited the clinic for surgical removal of her lower third molar. She reported a six-month history of pain in area of tooth number 38, along with persistent hypersensitivity radiating through the lower lip and chin on the left side of her face, accompanied by abnormal sensations and numbness occurring alongside the pain. The case includes entrapment of IAN within the root of the partially erupted tooth, causing neurosensory disturbances. The associated lower third molar was extracted using a stepwise multi-stage resection technique in order to preserve the entrapped nerve. The patient's pain improved after surgery. This report contributes to current clinical knowledge and practices for extracting teeth with IAN entrapment. It addresses a gap in the limited and outdated literature on such cases.

The Utility of Cone Beam Computed Tomography Scans in Diagnosing and Treating Anterior Lesions of the Maxilla and Mandible

BACKGROUND

The standard screening protocol for radiographic examination in dentistry as per the American Dental Association recommendations is a panoramic radiograph (PAN) and four horizontal bitewings. PAN inherently suffers from several shortcomings like the superimposition of anatomic structures, especially of the cervical spine that obscures a significant portion of the anterior maxilla and mandible. This region has a significant amount of pathology that is not adequately imaged. Three-dimensional (3D) imaging provides circumferential information on the area of interest and adds value to the diagnosis and treatment planning of pathology, especially in the anterior maxilla and mandible. However, there is not an adequate number of well-designed studies that articulate the true value addition of 3D imaging for the evaluation of this region.

OBJECTIVES

The objective of this study is to evaluate the value addition of 3D imaging in diagnosing pathologies in the anterior maxilla and mandible when compared to two-dimensional PAN.

MATERIALS AND METHODS

A total of 25 cases that had a diagnosis of anterior pathology and had both a PAN and a cone beam computed tomography (CBCT) scan were collected for this study. An institutional review board approval to retrospectively evaluate these data was obtained. The PAN and CBCT scans were randomly evaluated by a second-year dental student, an oral and maxillofacial radiology resident in training, and a board-certified oral radiologist. The scans were evaluated using a three-point modified Likert scale, where 1 represents "not visible or clear," 2 represents "visible but not clear," and 3 represents "visible and clear." The lesions were evaluated for characteristics like lesion location, size & shape, internal contents, borders of the lesion, cortical integrity, locularity, and effect on adjacent structures like root resorption. After the evaluation was completed, a comparison of the lesion diagnosis was done with histopathology to confirm the diagnosis. The evaluators were also asked to comment on the specific feature that 3D imaging provided that added value to the case. Kappa analysis was done to evaluate inter-operator reliability.

RESULTS

PAN demonstrated significantly lower efficacy in identifying and diagnosing lesions. Only 56% of cases were analyzed using PAN, with 44% deemed undetectable or poorly visualized. These challenging cases necessitated CBCT scans for accurate diagnosis, which successfully diagnosed all 25 cases. The p-value of 0.0002 for PAN implies a highly significant difference from histopathology, suggesting the distinctions are not due to chance. Conversely, the p-value of 0.3273 for CBCT implies that observed differences may be random, lacking sufficient evidence to reject the null hypothesis. CBCT scans consistently outperformed PAN in visualizing various lesion characteristics, underscoring their superior diagnostic capabilities.

CONCLUSIONS

In this study, with a small sample size, 3D imaging provided a significant value addition to the diagnosis and treatment planning by providing additional information regarding the location, extent, internal content, and effect on adjacent structures. The practical implications for clinical settings, along with comparisons to current literature, underscore the study's distinctiveness.

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.

An Anatomical Study of Dry Mandibles to Determine the Important Surgical Reference Points in Ramus Osteotomy - An Evaluative Study

Introduction

The variable relation and clinical significance of mandibular foramen (MF) and Lingula with inferior alveolar neurovascular bundle (IANB) is important for dental surgeons. Knowing the landmarks on the ramus of the mandible is of paramount importance to perform the surgery without causing damage to the neurovascular bundle.

Materials and Methods

This study was conducted on 85 dry adult mandibles of unknown sex and age. The distances were measured from the anatomical reference points (anti-Lingula, Lingula and MF) using digital callipers.

Results

The distance from the anti-Lingula to the anterior border of the ramus (A) was significantly longer on the right side (14.91 mm) than on the left side (14.5 mm). There was a significant difference in mean distances between the anti-Lingula and MF of both the sides (P ≤ 0.005). No significant difference was noted in the distances between the Lingula and the Anti-Lingula, observed for the posterior (B, P = 0.75) and the inferior margin of the mandible (D, P = 0.54). However we found correlation of vertical distances of anti-Lingula with Lingula and MF exhibited moderate positive correlation.

Discussion

The IANB is prone to damage during mandibular surgery. Using anti-Lingula alone as a reference point is not guaranteed, but it is still an important anatomical landmark for the surgeon to operate.

Correlation between the Mandibular Lingula Position and Some Anatomical Landmarks in Cone Beam CT

BACKGROUND

the position of the mandibular lingula (Li) affects the success rate of the inferior alveolar nerve block (IANB) and ramus osteotomies. This study evaluated the position of the Li, to investigate the anatomical relationship between the Li and some anatomical measurements using cone beam computed tomography (CBCT).

METHODS

201 hemimandibular CBCTs of 111 patients (43 males and 68 females; 18 to 88 years old) were retrospectively evaluated. The Li location was determined from the lingula tip to: the occlusal plane, the anterior and posterior borders of the mandibular ramus, the lower border of the mandible, the distal surface of the mandibular second molar, and the mandibular notch. We evaluated the correlations between the Li and the anteroposterior diameter of the mandibular ramus; the vertical distance between condyle and mandibular angle; the mesial-distal diameter of the first, second, and third mandibular molar, the intercanine distance, the intermolar distances among the first, second, and third mandibular molars; the distance between the intermolar line of the first molar and midline, and the length of the mandibular body.

RESULTS

the vertical distance of the Li from the occlusal plane was 11.22 ± 4.27 mm. Some parameters significantly correlated with the anatomical measurements taken into consideration.

CONCLUSIONS

the present study provides new information concerning the Li and mandibular anatomy in the Italian population. Moreover, by correlating some anatomic measurements to the Li position, the localization of the Li is made possible, indirectly through the measurement of some distances between anatomical landmarks.

Does Mandibular Gonial Angle Influence the Eruption Pattern of the Lower Third Molar? A Three-Dimensional Study

Lower third molars (M3M) are the most frequent impacted teeth. The aim of this study was to evaluate the correlation between M3M position and gonial angle. A retrospective cross-sectional study was conducted. The study population included patients with unilateral or bilateral M3M and underwent Cone Beam Computed Tomography. A morphometric analysis of the mandible was performed after three-dimensional reconstruction, recording gonial angle (GA), ramus high, ramus width, ramus divergency, and retromolar space. GA was the primary predictor variable. The primary outcome variable was the position of M3M analyzed in sagittal, axial, and coronal planes. Descriptive, bivariate, and multiple regression statistics were performed (p < 0.05). Study sample included 172 patients (mean age: 26.3 ± 4.6 years); 266 M3Ms were analyzed. The average GA was 122.6° ± 4.8°. A reduced GA value was significantly associated with a deeply impacted M3M in the ramus. With a progressive decrease of GA, M3M assumed a more horizontal position closer to the mandibular canal (p < 0.05). A lower GA showed a reduced retromolar space with more complex impacted M3M (p < 0.05). The results confirm a statistically significant correlation between GA and the position of M3M. Higher incidence of impacted M3M was related to a reduction of the GA value.

Can narrowing of the mandibular canal on pre-operative panoramic radiography predict close anatomical contact of the mandibular canal with the mandibular third molar? A meta-analysis

PURPOSE

Inferior alveolar nerve injury is a common complication following mandibular third molar extraction. Accurate pre-operative assessment of the anatomical relationship between the mandibular third molar and the mandibular canal could help to avoid this injury. We performed a eta-analysis to investigate whether panoramic radiography could be used to assess the relationship between these two structures.

METHODS

PubMed, EMBASE, SpringerLink, Cochrane Library, and Web of Science databases were searched independently by two researchers from January 2008 to May 2018.

RESULTS

Seven articles were identified. Statistical analyses were performed using Revman 5.3 and Meta-disc 1.4 software tools. The pooled sensitivity and specificity were 0.19 (95%CI:0.16-0.22) and 0.90 (95%CI:0.88-0.92), respectively. The pooled positive likelihood ratio and negative likelihood ratio were 2.34 (95%CI:1.42-3.87) and 0.86 (95%CI:0.78-0.96), respectively. The area under the curve was 0.86 (95%CI:0.78-0.96).

CONCLUSIONS

According to the sign of narrowing of the mandibular canal, panoramic radiology used to assess the relationship between the mandibular third molar and the mandibular canal yielded high specificity, but low sensitivity. The absence of narrowing of the mandibular canal indicated that there was no close contact between these two structures. However, the presence of narrowing of the mandibular canal could not be used to accurately evaluate the relationship between these two structures, although it might indicate a high probability of close anatomical contact between these two structures. Further tests should be performed for providing adequate pre-operative risk assessment while planning for the surgery to reduce the risk of inferior alveolar nerve injury, as well as to enable an open discussion with the patient to decrease the risk of medical disputes.

The assesment of relationship between the angulation of impacted mandibular third molar teeth and the thickness of lingual bone: A prospective clinical study

Background

Our purpose was to investigate the relationship between the angulation of mandibular third molars and the thickness of the lingual bone, which can affect the risk of lingual nerve damage during lower third molars surgical extraction.

Material and Methods

This study consisted of 104 patients (42 males and 62 females), aged between 18-42 years (24.67 ± 6.11 years). Cone Beam Computed Tomography (CBCT) images were taken for preoperative assessment. The teeth were divided into four groups according to their positions: mesioangular, distoangular, vertical and horizontal. Lingual bone thickness around impacted teeth were measured at three points: cementoenamel junction (CEJ) of the mandibular second molar, mid-root of the impacted third molar, and apex of the impacted third molar root. Two predisposing factors of lingual nerve damage were recorded: lingual bone perforated by the impacted tooth and lingual bone thinner than 1 mm. Additionally, buccolingual angulations of the teeth in each group were measured. Impacted mandibular third molars were removed in usual way. One week after surgery, the patients were evaluated regarding lingual nerve paresthesia.

Results

None of the 104 patients experienced paresthesia, including the ones who had teeth with close proximity with lingual nerve. The mean thickness of bone was 1.21±0.63 mm at CEJ of the second molar; 1.25±1.02 mm at the mid-root; and 1.06±1.31 mm at the apex. Horizontally impacted teeth had thinner lingual bone at mid-root level (p=0.016). Buccolingual angulated teeth were more often associated with perforated lingual bone (p=0.002). Buccolingual and mesial/distal angulation had negative correlation with lingual bone thickness (p<0.05).

Conclusions

As the buccolingual and mesiodistal angulations increase, lingual bone thickness decreases. Horizontally impacted teeth seemed to compromise the integrity of the lingual bone more than impacted teeth in other positions. During the surgery, thin or perforated lingual bone may result in displacement of the impacted tooth lingually.

Key words:Lingual bone, impacted third molar, cone beam computed tomography, angulation, paresthesia.

Geometric distortion of panoramic reconstruction in third molar tilting assessments: a comprehensive evaluation

OBJECTIVES:

To evaluate the geometric distortion of tilting of mandibular third molars with respect to second molars on panoramic reconstruction.

METHODS:

Cone-beam CT (CBCT) reconstructions of 160 third molars, obtained due to an indication of risk of inferior alveolar nerve damage during surgery, were used. CBCT-reconstructed panoramic images were used as bi-dimensional (2D) images, to avoid distortions other than geometric distortions. The angle between the second and the third molar was measured in 2D and three-dimensional (3D) images. Student's t-test was used to assess the null-hypothesis of no difference between 2D and 3D measurements.

RESULTS:

A significant mean difference (-2.3° ± 6.3°) between 2D and 3D measurements was found, with an absolute error of 3.6° ± 5.7° and a relative error of 10%. These findings comprehensively explain the geometric distortion on panoramic radiographs.

CONCLUSIONS:

Although a widely used and undoubtedly useful tool for diagnosis and surgical planning of mandibular third molar extractions, panoramic reconstruction are biased from geometric distortion that may influence surgical planning.

Measurement of Lingual Cortical Plate Thickness and Lingual Position of Lower Third Molar Roots Using Cone Beam Computed Tomography

Objective:

The objective of the study was to determine the potential risk of tooth/root displacement into the soft tissue during the third molar surgery. While performing third molar surgeries, one of the many complications is displacement of the tooth into the soft tissues. This can be due perforation of the lingual cortical bone during surgery or the position of the tooth root which may be close to the lingual bone.

Materials and Methods:

Retrospective samples of 251 patients were collected who had undergone cone-beam computed tomography (CBCT) for various reasons. Measurements were performed independently and recorded twice by one surgeon and one radiologist; the average of the two measurements was calculated and evaluated using MyRay CBCT.

Results:

On the right and the left side, the average distances in males for AL were 3.31 and 2.96 mm, respectively, whereas in females was found to be 3.98 and 3.56 mm which were statistically significant. On the right and left side, the average distances in males for RL were 2.03 and 1.78 mm, respectively, whereas in females, it was 2.41 and 1.99 mm, respectively, with the significant P value in the right side.

Conclusion:

Despite the sample size being of 251 patients, a large number of root of the third molar (95.62%) were not in contact with lingual cortical bone, but still practitioner should be careful during surgery as there might be the risk for displacement of the tooth. The images used were of impacted molar used in this study and these teeth were not subjected to surgery. Hence, the results can be only correlated theoretically, i.e., there would be a risk of displacement of the tooth during extraction.