Assessment of vertical facial and dentoalveolar changes using panoramic radiography

Automatic segmentation of inferior alveolar canal with ambiguity classification in panoramic images using deep learning

Background

Manual segmentation of the inferior alveolar canal (IAC) in panoramic images requires considerable time and labor even for dental experts having extensive experience. The objective of this study was to evaluate the performance of automatic segmentation of IAC with ambiguity classification in panoramic images using a deep learning method.

Methods

Among 1366 panoramic images, 1000 were selected as the training dataset and the remaining 336 were assigned to the testing dataset. The radiologists divided the testing dataset into four groups according to the quality of the visible segments of IAC. The segmentation time, dice similarity coefficient (DSC), precision, and recall rate were calculated to evaluate the efficiency and segmentation performance of deep learning-based automatic segmentation.

Results

Automatic segmentation achieved a DSC of 85.7% (95% confidence interval [CI] 75.4%-90.3%), precision of 84.1% (95% CI 78.4%-89.3%), and recall of 87.7% (95% CI 77.7%-93.4%). Compared with manual annotation (5.9s per image), automatic segmentation significantly increased the efficiency of IAC segmentation (33 ms per image). The DSC and precision values of group 4 (most visible) were significantly better than those of group 1 (least visible). The recall values of groups 3 and 4 were significantly better than those of group 1.

Conclusions

The deep learning-based method achieved high performance for IAC segmentation in panoramic images under different visibilities and was positively correlated with IAC image clarity.

Is There Any Difference Between Gonial Angle Values Measured on Digital Lateral Cephalograms and Orthopantomograms?

Objective

To determine whether there is a difference between the gonial angle (GoAng) values measured on digital lateral cephalograms (Lat Cephs) and orthopantomograms (OPGs) using a software.

Methods

This study was conducted by examining the digital Lat Cephs and OPGs of 51 patients (9 males, 42 females) who received orthodontic treatment. The mean age of the patients was 19.51±4.92 years. All digital radiographs were acquired with the same machine. The GoAng measurements were performed digitally using TotalCeph software. In order to evaluate the difference between the GoAngs measured on the digital Lat Cephs and OPGs, a paired t-test was used. To compare the two techniques (digital Lat Ceph and OPG) in terms of GoAng measurement, Bland-Altman analysis was used. The differences between the right and left GoAngs measured on the digital OPGs were evaluated using a paired t-test. The intraobserver reliability was assessed with the intraclass correlation coefficient (ICC) for repeated measurements.

Results

The intraobserver reliability was 0.99 for repeated measurements. There were no statistically significant differences between the GoAngs measured on digital Lat Cephs and OPGs (p=0.1). Bland-Altman analysis showed high levels of agreement between digital Lat Cephs and OPGs with a bias value of -0.4° for GoAng measurement. Moreover, the differences between the right and left GoAngs measured on the digital OPGs were not statistically significant (p=0.73).

Conclusion

The results of this study demonstrated that the digital OPGs were as reliable as the digital Lat Cephs for measuring Go angles using a software.

Radiographic evaluation of remodeling of mandible in adult South Indian population: Implications in forensic science

INTRODUCTION

Panoramic X-ray is an imagiological examination produced by a technique that exhibits images of the facial structure present in the upper and lower dental arches, as well as the support structures in the diagnosis of problems that require a broad view of the oral-maxillofacial complex, such as the assessment of traumatisms, extensive lesions, dental development, tooth retention, and growth anomalies. Many morphological and anatomical changes are exhibited by the mandible with the advancement of age and changes in gender, as well as dentoalveolar condition of the patient, and it can be assessed with the help of such radiograph, thus playing an important role in personal identification in forensic dentistry.

AIMS

This study aimed to evaluate the changes in gonial angle (GA), antegonial angle (AGA), and antegonial depth (AGD) in adult mandible with regard to age, gender, and dental status using panoramic radiographs.

SETTINGS AND DESIGN

This cross-sectional retrospective study was done using hospital records.

SUBJECTS AND METHODS

A total of 100 panoramic radiographs were evaluated. The images were grouped into three age groups (40-70) of 10 years each. GA, AGA, and AGD were digitally measured from the radiographs.

STATISTICAL ANALYSIS USED

Descriptive statistics of the variables were expressed in percentage, frequencies, mean, and standard deviations. Statistical differences between the variables were explored using independent sample t-test and one-way ANOVA. The significant level was set as 0.05.

RESULTS

There were no significant changes in GA, AGA, and AGD with age and dental status of the patients. Males had significantly smaller GA and AGA than females. Understandably, AGD was significantly greater in males than females.

CONCLUSIONS

Remodeling changes of the mandible with respect to the age groups and dental status studied were minimal. However, gender-related differences in ante AGA, depth, and GA were significant, which can be used as a tool in forensic identification.

Comparison of Orthopantomogram and Lateral Cephalogram for Mandibular Measurements

Aim:

The aim of the present study is to clarify the possible application of orthopantomogram (OPG) for evaluating craniofacial specifications such as angular and linear measurements of the mandible by comparing with lateral cephalogram.

Materials and Methods:

OPG and lateral cephalogram were taken from 100 patients of age group 16–35 years from Chettinad Dental College and Research Institute. Linear measurements (body length and ramus height) and angular measurement (gonial angle) were assessed both in lateral cephalogram and OPG. Independent t-test was performed for comparison of OPG and lateral cephalogram using SPSS with a probability level of P < 0.05 considered to be statistically significant.

Results:

The results of the present study show that there is no statistically significant difference in ramus height and gonial angle when compared between OPG and lateral cephalogram while statistically significant difference exists for body length between OPG and lateral cephalogram.

Conclusion:

It may be concluded that panoramic radiography can be used to determine the gonial angle and ramus height as accurately as a lateral cephalogram. However, clinicians should be vigilant when predicting horizontal measurement from OPGs.

Dilemma of gonial angle measurement: Panoramic radiograph or lateral cephalogram

Purpose

The purpose of this study was to evaluate the accuracy of panoramic imaging in measuring the right and left gonial angles by comparing the measured angles with the angles determined using a lateral cephalogram of adult patients with class I malocclusion.

Materials and Methods

The gonial angles of 50 class I malocclusion patients (25 males and 25 females; mean age: 23 years) were measured using both a lateral cephalogram and a panoramic radiograph. In the lateral cephalograms, the gonial angle was measured at the point of intersection of the ramus plane and the mandibular plane. In the panoramic radiographs, the gonial angle was measured by drawing a line tangent to the lower border of the mandible and another line tangent to the distal border of the ascending ramus and the condyle on both sides. The data obtained from both radiographs were statistically compared.

Results

No statistically significant difference was observed between the gonial angle measured using the lateral cephalograms and that determined using the panoramic radiographs. Further, there was no statistically significant difference in the measured gonial angle with respect to gender. The results also showed a statistically insignificant difference in the mean of the right and the left gonial angles measured using the panoramic radiographs.

Conclusion

As the gonial angle measurements using panoramic radiographs and lateral cephalograms showed no statistically significant difference, panoramic radiography can be considered in orthodontics for measuring the gonial angle without any interference due to superimposed images.

Age and gender correlation of gonial angle, ramus height and bigonial width in dentate subjects in a dental school in Far North Queensland

Background

This study aimed to determine if mandibular parameters (gonial angle, bigonial width and ramus height) measured from panoramic radiographs, can be used to determine a correlation with an individual’s age and gender in dentate subjects in Far North Queensland.

Material and Methods

The study utilised 2699 randomly selected panoramic radiographs of patients between the ages of 19-69 years, from which 220 fulfilled the inclusion criteria. Each panoramic radiograph was analysed and the above three parameters recorded and measured. These values were collated into appropriate age and gender groups and subjected to statistical analysis.

Results

The mean age of the participants was 44.1±14.41, with males being shown to have a statistically significant larger ramus height and bigonial width than females (P<0.0001 for both). Females, on the other hand, were shown to have a significantly larger gonial angle than males (P<0.0002). General trends revealed gonial angle to increase with age, whilst bigonial width and ramus height were shown to decrease with age.

Conclusions

The assessment of mandibular morphology through radiographic measurements may be useful in estimating an individual’s age and gender when comparing to a known population standard.

Key words:Bigonial width, gonial angle, panoramic radiograph, ramus height.

Agreement between panoramic and lateral cephalometric radiographs for measuring the gonial angle

Background

The gonial angle is one of the most important measurements required for orthodontic treatment and orthognathic surgery. It is difficult to determine the accurate measurement of each gonial angle on cephalometric radiographs because of superimposition of the left and right angles.

Objectives

The aim of the present study was to determine the right and left gonial angles on panoramic radiographs and to compare them with an evaluated cephalometric sample.

Patients and Methods

A total of 80 panoramic and 80 cephalometric radiographs were obtained from 6 to 12-year-old children and the gonial angle was determined by the tangent of the inferior border of the mandible and the most distal aspect of the ascending ramus and the condyleon both panoramic and cephalometric radiographs. We used Pearson’s correlation coefficient and paired t-test for comparison.

Results

The mean gonial angle was 127.07 ± 6.10 and 127.5 ± 6.67 degrees on panoramic and cephalometric radiographs, respectively. There was no statistically significant difference between the measured gonial angles on panoramic and cephalometric radiographs and also no difference between the right and left (both Ps = 0.18)

Conclusion

The value of the gonial angle measured on panoramic radiography was the same as that measured on the routinely used cephalometric radiography.

Influence of the intergonial distance on image distortion in panoramic radiographs

OBJECTIVES

The aim of this study was to evaluate the influence of the intergonial distance during the formation of panoramic radiographic images by means of horizontal and vertical measurements.

METHODS

30 macerated mandibles were categorized into 3 different groups (n = 10) according to their intergonial distances as follows: G1, mean distance 8.2 cm, G2, mean distance 9.0 cm and G3, mean distance 9.6 cm. Three metal spheres 0.198 cm in diameter and placed at an incline using an isosceles triangle were separately placed over the internal and external surfaces of the mandibles before radiographic exposure for the purpose of taking the horizontal and vertical measurements. The occlusal planes of the mandibles were horizontally placed on the chin rest of the panoramic machine Orthopantomograph® OP 100 (Instrumentarium Imaging, Tuusula, Finland) and were then radiographed. In the panoramic radiographs, an expert radiologist measured the distances between the metal spheres in the horizontal and vertical directions using a digital caliper. The data were tabled and statistically analysed by Student's t-test and analysis of variance with Tukey post-test (α = 0.05).

RESULTS

In all three groups magnification of the distances between spheres was observed when compared with the real distance in both horizontal and vertical measurements (p < 0.05). Differences in both horizontal and vertical measurements were observed between the different regions (p < 0.05), however there were no differences between groups in the same region (p > 0.05). Differences between horizontal and vertical measurements were observed in different regions in all evaluated groups (p < 0.05).

CONCLUSION

The intergonial distance is a factor that had no influence on image formation in the panoramic radiograph.

Evaluation of the panoramic image formation in different anatomic positions

The aim of this study was to determine size, shape and position of the image layer by evaluation of the radiographic image formation in different anatomic positions. A customized phantom was made of a rectangular acrylic plate measuring 14 cm² and 0.3 cm thick, with holes spaced 0.5 cm away and arranged in rows and columns. Each column was separately filled with 0.315 cm diameter metal spheres to acquire panoramic radiographs using the Orthopantomograph OP 100 unit. The customized phantom was placed on the mental support of the device, with its top surface kept parallel to the horizontal plane, and was radiographed at three different heights from the horizontal plane, i.e., the orbital, occlusal and mandibular symphysis levels. The images of the spheres were measured using a digital caliper to locate the image layer. The recorded data were analyzed statistically by the Student'-t test, ANOVA and Tukey' test (?=0.05). When the image size of spheres in horizontal and vertical axes were compared, statistically significant differences (p<0.05) were observed in all areas, portions of the image layer and heights of horizontal plane evaluated. In the middle portion of the image layer, differences in the image size of spheres were observed only along the horizontal axis (p<0.05), whereas no differences were observed along the vertical axis (p>0.05). The methodology used in this determined the precise size, shape and position of the image layer and differences in magnification were observed in both the horizontal and vertical axes.