Evaluation of bone changes in the temporomandibular joint using cone beam CT

Objective

The aim of this study was to assess bone changes and mobility in temporomandibular joints (TMJs) using cone beam CT (CBCT) in a population sample in Recife, PE, Brazil.

Methods

The TMJ images of patients treated by a radiologist at a private dental radiology service over a period of 1 year were retrieved from the computer database and assessed using a computer with a 21-inch monitor and the iCAT Cone Beam 3D Dental Imaging System Workstation program (Imaging Sciences International, Hatfield, PA). The Pearson χ² test was used to analyse the differences in percentage of bone changes among the categories of mobility (p ≤ 0.05). The McNemar test was used to compare the presence of bone changes in TMJs on the right and left sides (p ≤ 0.05).

Results

An adjusted logistic regression model was used to assess the effect of age and gender on the occurrence of bone changes (p ≤ 0.05). Bone changes were present in 227 (71%) patients. Age group and gender showed a statistically significant association with presence of bone changes (p ≤ 0.05). There was no significant difference between the right and left sides (p = 0.556) and in condylar mobility (p = 0.925) with regard to the presence of degenerative bone changes.

Conclusions

There is a high prevalence of degenerative bone alteration in TMJs, which is more frequent in women and mostly located in the condyle. The prevalence of degenerative bone changes increases with age. There is no correlation between condylar mobility and the presence of degenerative bony changes in TMJs.     

Diagnostic performance of magnetic resonance imaging for detecting osseous abnormalities of the temporomandibular joint and its correlation with cone beam computed tomography

Objective

With cone beam CT (CBCT) as the reference standard, the objective of this study was to determine the diagnostic accuracy of MRI for assessing osseous abnormalities of the temporomandibular joint (TMJ).

Methods

106 TMJs from 55 patients with temporomandibular disorder were examined by CBCT and MRI. CBCT images were evaluated by two experienced oral radiologists with regard to the presence or absence of each of the following eight types of osseous abnormalities: Type 1, destructive and erosive osseous changes of the condyle; Type 2, flattening of the articular surface of the condyle; Type 3, deformity of the condyle; Type 4, sclerosis of the condyle; Type 5, osteophyte formation; Type 6, ankylosis; Type 7, erosion of the articular fossa and/or eminence; and Type 8, sclerosis of the articular fossa and/or eminence. For detection of these osseous abnormalities by MRI, proton density-weighted images and T₂ weighted images were evaluated independently by three observers. Using CBCT findings as the reference standard, the diagnostic performance of MRI for detecting various types of osseous abnormalities was evaluated by calculating its sensitivity and specificity.

Results

Out of 106 joints, CBCT revealed Types 1, 2, 3, 4, 5, 6, 7 and 8 abnormalities in 25, 19, 26, 20, 14, 5, 19 and 22 joints, respectively. The mean sensitivities of MRI among the three observers for detecting Types 1, 2, 3, 4, 5, 6, 7 and 8 abnormalities were 61%, 30%, 82%, 40%, 48%, 34%, 61% and 41%, respectively, whereas the mean specificities were 86%, 92%, 91%, 95%, 84%, 98%, 89% and 91%, respectively.

Conclusions

Although high specificity (84–98%) was obtained with MRI, this modality showed relatively low sensitivity (30–82%) for detecting osseous abnormalities of the TMJ. The value of MRI for the detection of TMJ osseous abnormalities is considered to be limited.     

Small field of view cone beam CT temporomandibular joint imaging dosimetry

Objectives:

Cone beam CT (CBCT) is generally accepted as the imaging modality of choice for visualisation of the osseous structures of the temporomandibular joint (TMJ). The purpose of this study was to compare the radiation dose of a protocol for CBCT TMJ imaging using a large field of view Hitachi CB MercuRay™ unit (Hitachi Medical Systems, Tokyo, Japan) with an alternative approach that utilizes two CBCT acquisitions of the right and left TMJs using the Kodak 9000^® 3D system (Carestream, Rochester, NY).

Methods:

25 optically stimulated luminescence dosemeters were placed in various locations of an anthropomorphic RANDO^® Man phantom (Alderson Research Laboratories, Stanford, CT). Dosimetric measurements were performed for each technique, and effective doses were calculated using the 2007 International Commission on Radiological Protection tissue weighting factor recommendations for all protocols.

Results:

The radiation effective dose for the CB MercuRay technique was 223.6 ± 1.1 μSv compared with 9.7 ± 0.1 μSv (child), 13.5 ± 0.9 μSv (adolescent/small adult) and 20.5 ± 1.3 μSv (adult) for the bilateral Kodak acquisitions.

Conclusions:

Acquisitions of individual right and left TMJ volumes using the Kodak 9000 3D CBCT imaging system resulted in a more than ten-fold reduction in the effective dose compared with the larger single field acquisition with the Hitachi CB MercuRay. This decrease is made even more significant when lower tube potential and tube current settings are used.     

Correlating cone beam CT results with temporomandibular joint pain of osteoarthritic origin

Objectives

The purpose of this study was to determine whether bony changes in temporomandibular joint (TMJ) osteoarthritis (OA) is correlated with pain and other clinical signs and symptoms.

Methods

Clinical data and cone beam CT (CBCT) images of 30 patients with TMJ OA were analysed. The criteria of Koyama et al (Koyama J, Nishiyama H, Hayashi T. Follow-up study of condylar bony changes using helical computed tomography in patients with temporomandibular disorder. Dentomaxillofac Radiol 2007; 36: 472–477.) and Ahmad et al [Ahmad M, Hollender L, Anderson Q, Kartha K, Ohrbach R, Truelove EL, et al. Research diagnostic criteria for temporomandibular disorders (RDC/TMD): development of image analysis criteria and examiner reliability for image analysis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: 844–860.] were used to classify the condyles observed on the CBCT. Clinical measures included self-reported pain, mandibular range of motion, TMJ sound, pain on palpation of the TMJ and masticatory muscles, and pain on jaw function. Generalized linear modelling was used to correlate the clinical and radiographic findings and Spearman''s rho was used to correlate the two classification systems.

Results

There was poor correlation between the maximum condyle change and pain rating (Koyama: r² = 0.1443, p = 0.3995; Ahmad: r² = 0.0273, p = 0.9490), maximum mouth opening (Koyama: r² = 0.2910, p = 0.0629; Ahmad: r² = 0.2626, p = 0.0951), protrusion (Koyama: r² = 0.0875, p = 0.7001; Ahmad: r² = 0.1658, p = 0.3612), right lateral motion (Koyama: r² = 0.0394, p = 0.9093; Ahmad: r² = 0.0866, p = 0.6877) and left lateral motion (Koyama: r² = 0.0943, p = 0.6494; Ahmad: r² = 0.1704, p = 0.3236). Strong correlation was observed between Koyama et al''s and Ahmad et al''s classifications for average (r = 0.9216, p < 0.001) and maximum (r = 0.7694; p < 0.0001) bony change.

Conclusions

There was poor correlation between condylar changes (as observed on CBCT images), pain and other clinical signs and symptoms in TMJ OA.     

Evaluation of the effective dose of cone beam CT and multislice CT for temporomandibular joint examinations at optimized exposure levels

Objectives:

To compare the effective dose to patients from temporomandibular joint examinations using a dental CBCT device and a multislice CT (MSCT) device, both before and after dose optimization.

Methods:

A Promax^® 3D (Planmeca, Helsinki, Finland) dental CBCT and a LightSpeed VCT^® (GE Healthcare, Little Chalfont, UK) multislice CT were used. Organ doses and effective doses were estimated from thermoluminescent dosemeters at 61 positions inside an anthropomorphic phantom at the exposure settings in clinical use. Optimized exposure protocols were obtained through an optimization study using a dry skull phantom, where four observers rated image quality taken at different exposure levels. The optimal exposure level was obtained when all included criteria were rated as acceptable or better by all observers.

Results:

The effective dose from a bilateral examination was 184 µSv for Promax 3D and 113 µSv for LightSpeed VCT before optimization. Post optimization, the bilateral effective dose was 92 µSv for Promax 3D and 124 µSv for LightSpeed VCT.

Conclusions:

At optimized exposure levels, the effective dose from CBCT was comparable to MSCT.     

Usefulness of cone beam computed tomography in temporomandibular joints with soft tissue pathology

Objective

The aim of the study was to evaluate the usefulness of cone beam CT (CBCT) in temporomandibular joints (TMJs) with soft tissue pathology.

Methods

106 TMJs of 55 patients with temporomandibular disorder (TMD) were examined by MRI and CBCT. MR images were used for the evaluation of disc displacement, disc deformity, joint effusion and obscurity of temporal posterior attachment (TPA). CBCT images were evaluated for the presence or absence of osseous abnormalities. The χ² test was used to analyse the association between MRI and CBCT findings.

Results

MRI of 106 TMJs revealed disc displacement, disc deformity, joint effusion and obscurity of the TPA in 68, 73, 28 and 27 joints, respectively. Of the 68 TMJs with disc displacement, anterior disc displacement without reduction (ADDWR) was seen most frequently (47/68). CBCT imaging found 65 TMJs were characterized by the presence of osseous abnormalities and were significantly associated with disc deformity and ADDWR (P < 0.05). There was no statistically significant association between the presence of joint effusion and obscurity of TPA and TMJ osseous abnormalities.

Conclusions

TMD patients with confirmed ADDWR or disc deformity on MRI are at risk of having osseous abnormalities in the TMJ and further examination with CBCT is recommended.     

The use of arthrography in the diagnosis of temporomandibular joint synovial chondromatosis

Synovial chondromatosis (SC) involving the temporomandibular joint (TMJ) is very rare and can occur in either or both cavities. Differentiation of the affected cavity in SC is therefore as important as making the diagnosis. This report presents a case of SC in which both cavities were thought to be affected, but arthrography using cone beam CT (CBCT) allowed us to see that involvement was limited to the superior joint cavity. In addition, we describe the usefulness of arthrographic CBCT for diagnosis and treatment planning in SC of the TMJ.     

A comparative study of the diagnostic capabilities of 2D plain radiograph and 3D cone beam CT sialography

Objective

The aim of this study was to compare the diagnostic capabilities of two-dimensional sialography with a novel three-dimensional technique using cone beam CT (CBCT).

Methods

47 subjects underwent parotid or submandibular gland sialography over a 2 year period using both plain imaging and CBCT. Both image sets were anonymized and independently reviewed by three certified oral and maxillofacial radiologists blinded to the clinical data. McNemar''s χ² test was used to determine differences between the two modalities for feature visualization and interpretation.

Results

CBCT outperformed plain imaging with respect to visualization of the gland parenchyma (p < 0.001) and identification of sialoliths (p = 0.02). Plain imaging outperformed CBCT for the identification of strictures (p = 0.04); however, the negative per cent agreement (“specificity”) between the two imaging modalities was 100%. Although both imaging modalities performed equally in identifying normal and abnormal sialographic examinations, CBCT demonstrated a high negative per cent agreement for normal glands and a high positive per cent agreement (“sensitivity”) for abnormal glands with inflammatory changes.

Conclusion

CBCT sialography allowed better visualization of gland parenchyma and identification of sialoliths. The high negative per cent agreement for strictures suggests that, if strictures are identified on CBCT images, then obstruction can be ruled in. Relative to plain images, the high negative per cent agreement for normal glands suggests that, if an abnormal finding is detected on CBCT images, then disease can be ruled in, and the high positive per cent agreement for glands with inflammatory changes suggests that inflammation can be ruled out if these changes are not seen on CBCT images.     

Detection accuracy of condylar defects in cone beam CT images scanned with different resolutions and units

Objectives:

To assess the impact of spatial resolution and cone beam CT (CBCT) unit on CBCT images for the detection accuracy of condylar defects.

Methods:

42 temporomandibular joints were scanned, respectively, with the CBCT units ProMax® 3D (Planmeca Oy, Helsinki, Finland) and DCT PRO (Vatech, Co., Ltd., Yongin-Si, Republic of Korea) at normal and high resolutions. Seven dentists evaluated all the test images with respect to the presence or the absence of condylar defects. Receiver operating characteristic curve analysis was employed to define the detection accuracy. Two-way analysis of variance was used to analyse the values under the receiver operating characteristic curves for the differences among imaging groups and observers. Intraobserver variation was analysed using the Wilcoxon test.

Results:

Macroscopic anatomy examination revealed that, of the 42 temporomandibular joint condylar surfaces, 18 were normal and 24 had defects on the surface of condyles. No significant differences were found between the images scanned with normal and high resolutions for both CBCT units ProMax 3D (p = 0.119) and DCT PRO (p = 0.740). Significant differences exist between image groups of DCT PRO and ProMax 3D (p < 0.05). Neither the inter- nor the intraobserver variability were significant.

Conclusions:

The spatial resolution per se did not have an impact on the detection accuracy of condylar defects. The detection accuracy of condylar defects highly depends on the CBCT unit used for examination.     

The influence of exposure parameters on jawbone model accuracy using cone beam CT and multislice CT

Objective

The main purpose of this study was to investigate the influence of exposure parameters on jawbone model accuracy when using cone beam CT (CBCT) and multislice CT (MSCT).

Methods

A lower and an upper edentulous human cadaver jaw were scanned using micro-CT (Skyscan 1173 high energy spiral scan micro-CT; Skyscan NV, Kontich, Belgium) at 35 μm to serve as true reference. The in vitro samples were exposed using six CBCT units and one MSCT system. CBCT exposure protocols were chosen according to clinically available settings. The variables were kilovoltage, milliamperage, voxel size and/or scan time. Image segmentation was based on local thresholds using profile lines. The resulting jawbone segmentations were registered with the reference and image processing was done to internally fill the segmentations. A point-based distance calculation was performed between the three-dimensional objects and reference scans and deviation percentages were calculated for 2 mm, 1 mm and 0.5 mm intervals.

Results

All points of the MSCT surface models lay within a 1 mm deviation range and 98.5% within 0.5 mm compared with micro-CT. For the different CBCT systems, accuracy came close to MSCT with mean percentages of 98.9% within 1 mm deviation and 92.8% within 0.5 mm. A difference of approximately 1% between lower and upper jaws could be perceived. For the specific CBCT exposure protocols, only scan time and voxel size revealed certain significant differences.

Conclusion

Jawbone model accuracy using CBCT was comparable with MSCT. The surface models of the upper jaws deviated slightly more than those for lower jaws. CBCT exposure settings had a limited influence on accuracy with scan time and voxel size as the main factors.     

The importance of cone beam CT in the radiological detection of osteomalacia

Although osteomalacia is one of the most common osteometabolic diseases among the elderly, there is no case in the literature that presents the effects of osteomalacia in detail using cone beam CT (CBCT). While thin and porous bones are the most common radiographic sign of the disease, the radiological hallmarks are pseudofractures (Looser's zone). We coincidentally detected osteomalacia in a 23-year-old female and we showed the pseudofracture on CBCT images. In the present case, we aim to present the images of osteomalacia that were detected by CBCT in detail. CBCT has an important value in screening for osteomalacia.     

Radiological examination of the articular eminence morphology using cone beam CT

Objective

The purpose of the present study was to investigate the articular eminence inclination and height according to age and gender in patients with temporomandibular joint (TMJ) dysfunction and healthy controls using cone beam CT (CBCT).

Methods

The measurements were performed on CBCT records of 52 TMJ dysfunction patients (11 males and 41 females) and 41 control patients (17 males and 24 females). The eminence inclination and height were measured on the CBCT images.

Results

The eminence inclination and height values were higher in males than in females in both TMJ dysfunction patient and control groups; however, these differences were not statistically significant (p>0.05). While no statistically significant differences were found in the eminence inclination and height values between the age groups (p>0.05) in the TMJ dysfunction patient group, there were statistically significant differences in the control group. The eminence inclination was highest between the ages of 21 and 30 years and showed a decrease after the age of 30 years. Additionally, the eminence inclinations of the control patients were statistically higher than those of the TMJ dysfunction patients.

Conclusion

There were no statistically significant differences in eminence inclination and height according to gender. The eminence inclination reaches its highest value between the ages of 21 and 30 years and shows a decrease after the age of 31 years in healthy patients. The eminence inclination was steeper in healthy control patients than in patients with TMJ dysfunction.     

Metal artefact reduction with cone beam CT: an in vitro study

Background

Metal in a patient''s mouth has been shown to cause artefacts that can interfere with the diagnostic quality of cone beam CT. Recently, a manufacturer has made an algorithm and software available which reduces metal streak artefact (Picasso Master 3D® machine; Vatech, Hwaseong, Republic of Korea).

Objectives

The purpose of this investigation was to determine whether or not the metal artefact reduction algorithm was effective and enhanced the contrast-to-noise ratio.

Methods

A phantom was constructed incorporating three metallic beads and three epoxy resin-based bone substitutes to simulate bone next to metal. The phantom was placed in the centre of the field of view and at the periphery. 10 data sets were acquired at 50–90 kVp. The images obtained were analysed using a public domain software ImageJ (NIH Image, Bethesda, MD). Profile lines were used to evaluate grey level changes and area histograms were used to evaluate contrast. The contrast-to-noise ratio was calculated.

Results

The metal artefact reduction option reduced grey value variation and increased the contrast-to-noise ratio. The grey value varied least when the phantom was in the middle of the volume and the metal artefact reduction was activated. The image quality improved as the peak kilovoltage increased.

Conclusion

Better images of a phantom were obtained when the metal artefact reduction algorithm was used.     

Intracranial physiological calcifications evaluated with cone beam CT

Objectives

The purpose of this study was to evaluate cone beam CT (CBCT) scans for the presence of physiological and pathological intracranial calcifications.

Methods

CBCT scans from male and female patients that met our ascertainment criteria were evaluated retrospectively (n = 500) for the presence of either physiological or pathological intracranial calcifications.

Results

Out of the 500 patients evaluated, 176 had evidence of intracranial physiological calcification (35.2% prevalence), and none had evidence of pathological calcification. There was a 3:2 male-to-female ratio and no ethnic predilection; the ages of affected patients ranged from 13 years to 82 years with a mean age of 52 years. The majority of calcifications appeared in the pineal/habenular region (80%), with some also appearing in the choroid plexus region bilaterally (12%), and a smaller subset appearing in the petroclinoid ligament region bilaterally (8%).

Conclusions

Intracranial physiological calcifications can be a common finding on CBCT scans, whereas pathological intracranial calcifications are rare.     

Cervical vertebral column morphology in patients with obstructive sleep apnoea assessed using lateral cephalograms and cone beam CT. A comparative study

Objectives:

Few studies have described morphological deviations in obstructive sleep apnoea (OSA) patients on two-dimensional (2D) lateral cephalograms, and the reliability of 2D radiographs has been discussed. The objective is to describe the morphology of the cervical vertebral column on cone beam CT (CBCT) in adult patients with OSA and to compare 2D lateral cephalograms with three-dimensional (3D) CBCT images.

Methods:

For all 57 OSA patients, the cervical vertebral column morphology was evaluated on lateral cephalograms and CBCT images and compared according to fusion anomalies and posterior arch deficiency.

Results:

The CBCT assessment showed that 21.1% had fusion anomalies of the cervical column, i.e. fusion between two cervical vertebrae (10.5%), block fusions (8.8%) or occipitalization (1.8%). Posterior arch deficiency occurred in 14% as partial cleft of C1 and in 3.5% in combination with block fusions. The agreement between the occurrence of morphological deviations in the cervical vertebral column between lateral cephalograms and CBCT images showed good agreement (κ = 0.64).

Conclusions:

Prevalence and pattern in the cervical column morphology have now been confirmed on CBCT. The occurrence of morphological deviations in the cervical vertebral column showed good agreement between lateral cephalograms and CBCT images. This indicates that 2D lateral cephalograms (already available after indication in connection with, e.g. treatment planning) are sufficient for identifying morphological deviations in the cervical vertebral column. For a more accurate diagnosis and location of the deviations, CBCT is required. New 3D methods will suggest a need for new detailed characterization and division of deviations in cervical vertebral column morphology.     

Effective doses from cone beam CT investigation of the jaws

Objectives

The purpose of the study was to calculate the effective dose delivered to the patient undergoing cone beam (CB) CT of the jaws and maxillofacial complex using the i-CAT Next Generation CBCT scanner (Imaging Sciences International, Hatfield, PA).

Methods

A RANDO® phantom (The Phantom Laboratory, Salem, NY) containing thermoluminence dosemeters were scanned 10 times for each of the 6 imaging protocols. Effective doses for each protocol were calculated using the 1990 and approved 2007 International Commission on Radiological Protection (ICRP) recommended tissue weighting factors (E1990, E2007).

Results

The effective dose for E1990 and E2007, respectively, were: full field of view (FOV) of the head, 47 μSv and 78 μSv; 13 cm scan of the jaws, 44 μSv and 77 μSv; 6 cm standard mandible, 35 μSv and 58 μSv; 6 cm high resolution mandible, 69 μSv and 113 μSv; 6 cm standard maxilla, 18 μSv and 32 μSv; and 6 cm high resolution maxilla, 35 μSv and 60 μSv.

Conclusions

Using the new generation of CBCT scanner, the effective dose is lower than the original generation machine for a similar FOV using the ICRP 2007 tissue weighting factors.     

Ex vivo comparison of Galileos cone beam CT and intraoral radiographs in detecting occlusal caries

Objective

The aim of this study was to compare the accuracy of cone beam CT (CBCT) with intraoral radiographs for detection of occlusal caries.

Methods

A set of 60 extracted teeth were imaged using a Sirona Galileos CBCT system (Sirona Dental Systems, Bensheim, Germany) and an intraoral Planmeca® system (Planmeca OY, Helsinki, Finland). Six observers looked at both modalities and used a five-point confidence scale to evaluate presence or absence of occlusal caries. Histology was used as the gold standard. Receiver operating characteristic analysis and weighted kappa statistics were used for statistical analysis. Differences in the area under the curve (AUC) values between observers and modalities were analysed using analysis of variance (ANOVA). Differences in sensitivity and specificity were analysed using the Wilcoxon test. Interobserver and intraobserver reliability was assessed by weighted kappa scores.

Results

The mean value and standard deviation of AUC was 0.719 ± 0.038 for CBCT and 0.649 ± 0.062 for the intraoral radiographs. The ANOVA results demonstrated that there was no significant difference between the modalities and the observers. The interobserver kappa for pairs of observers ranged from fair to substantial for bitewings (0.244–0.543) and CBCT (0.152–0.401). Four out of six observers reported higher sensitivity but lower specificity with CBCT. The Wilcoxon exact p-value showed no difference in sensitivity (0.175) or specificity (0.573) between the two modalities.

Conclusion

Based on the results we conclude that the Sirona CBCT unit cannot be used for the sole purpose of looking at occlusal caries.     

A comparative study of the effective radiation doses from cone beam computed tomography and plain radiography for sialography

Objectives

As a first step in developing a protocol for multidimensional sialography using cone beam CT (CBCT), the objective of this study was to compare the effective radiation doses from sialography of the parotid and submandibular glands using plain radiography and CBCT.

Methods

The effective doses were calculated from dose measurements made at 25 selected locations in the head and neck of a radiation analogue dosimeter (RANDO) phantom, using International Commission on Radiological Protection 2007 tissue weighting factors.

Results

The effective dose (E) changed in relationship to changes in CBCT field of view (FOV), peak kilovoltage (kVp) and milliamperage (mA). Specifically, E decreased from a maximum of 932 μSv (30 cm FOV, 120 kVp, 15 mA) to 60 μSv (15 cm FOV, 80 kVp, 10 mA) for a parotid gland study and to 148 μSv (15 cm FOV, 80 kVp, 10 mA) for a submandibular study. The collective series of plain radiographs made during sialography of the parotid and submandibular glands yielded effective doses of 65 μSv and 156 μSv, respectively. The plain parotid gland series included one panoramic, two anterior–posterior skull and four lateral skull radiographs, whereas the submandibular gland series included one panoramic, one standard mandibular occlusal and four lateral skull radiographs.

Conclusion

The effective doses from CBCT examinations centred on the parotid and submandibular glands were similar to those calculated for plain radiograph sialography when a 15 cm FOV was chosen in combination with exposure conditions of 80 kVp and 10 mA.     

Evaluation of juxta-apical radiolucency in cone beam CT images

Objectives:

The aim of this study was to analyse the position and relationship of juxta-apical radiolucency (JAR) to the mandibular canal and buccal and/or lingual cortical plates using cone beam CT (CBCT).

Methods:

A retrospective study was carried out to analyse the JAR on CBCT for 27 patients. These findings were compared with 27 age- and sex-matched patients without the presence of JAR, which acted as the control group. The CBCT images were analysed according to a checklist, to evaluate the position of the JAR and its relationship to the mandibular canal. Then, any thinning or perforation of either the buccal or lingual cortical plate due to JAR was noted, and a classification to quantify the thinning of cortical plates was proposed. The findings in the two groups were analysed using a paired comparison by McNemar test.

Results:

A statistical increased thinning of cortical plates was seen in the JAR group compared with the control group, and most of the cases were in the J3 group. None of the patients in either the JAR or the control group showed perforation of the buccal and/or lingual cortical plate on CBCT images.

Conclusions:

A classification to quantify the thinning of cortical plates was proposed, which may be used for objective evaluation of the thinning of the cortical plates in future studies. The present study gives an insight into the relationship of the juxta-apical area with the mandibular canal and cortical plates in the mandible using CBCT.