Cone beam computed tomography use in orthodontics

Divergence between CBCT and Optical Scans for Soft Tissue Analysis and Cephalometry in Facial Imaging: A cross-sectional study on healthy adults

BACKGROUND

Facial soft tissue analysis is becoming increasingly emphasized in orthodontic diagnosis and treatment planning. While traditional cephalometry primarily focuses on hard tissues, recent non-invasive imaging techniques offer the potential to comprehensively evaluate three-dimensional (3D) facial soft tissues. The aim of the study was to establish the geometrical 3D and cephalometric divergence between Cone Beam Computed Tomography (CBCT) derived images and scanned soft tissues. Crucial for enhancing orthodontic diagnosis, minimizing patient exposure to ionizing radiation and providing facial cephalometric parameters.

MATERIAL AND METHODS

A cross-sectional study was conducted from January 2020 to May 2023. CBCT and 3D facial scans were obtained simultaneously using a specialized imaging system. Reproducible landmark points were selected for both cephalometric and soft tissue analysis. Angular and linear measurements were recorded, and correlations between CT and facial scans were statistically assessed.

RESULTS

Comparisons between 10 CBCT-derived and 10 facial scan-based soft tissue representations resulted into 1.8mm mean root median square (RMS). Angular measurements, such as ANB, right gonial angle, and left gonial angle, exhibited a 0.9° of difference with their respective soft tissue variables. In contrast, linear measurements of total anterior facial height showed a lower correlation coefficient, equal to 0.51. The correlation between soft tissues and underlying hard tissues was more pronounced for gonial angles.

CONCLUSION

Facial soft tissue analysis using either 3D facial scans or CBCT-derived offers similar results for orthodontic diagnosis and treatment planning. These findings support the use of non-invasive diagnostic tools in orthodontics, although further investigations are needed to comprehensively understand the complexity of hard and soft tissue relationships.

Head motion during cone-beam computed tomography: Analysis of frequency and influence on image quality

Purpose

Image artifacts caused by patient motion cause problems in cone-beam computed tomography (CBCT) because they lead to distortion of the 3-dimensional reconstruction. This prospective study was performed to quantify patient movement during CBCT acquisition and its influence on image quality.

Materials and Methods

In total, 412 patients receiving CBCT imaging were equipped with a wireless head sensor system that detected inertial, gyroscopic, and magnetometric movements with 6 dimensions of freedom. The type and amplitude of movements during CBCT acquisition were evaluated and image quality was rated in 7 different anatomical regions of interest. For continuous variables, significance was calculated using the Student t-test. A linear regression model was applied to identify associations of the type and extent of motion with image quality scores. Kappa statistics were used to assess intra- and inter-rater agreement. Chi-square testing was used to analyze the impact of age and sex on head movement.

Results

All CBCT images were acquired in a 10-month period. In 24% of the investigations, movement was recorded (acceleration: >0.10 [m/s²]; angular velocity: >0.018 [°/s]). In all examined regions of interest, head motion during CBCT acquisition resulted in significant impairment of image quality (P<0.001). Movement in the horizontal and vertical axes was most relevant for image quality (R²>0.7).

Conclusion

Relevant head motions during CBCT imaging were frequently detected, leading to image quality loss and potentially impairing diagnosis and therapy planning. The presented data illustrate the need for digital correction algorithms and hardware to minimize motion artefacts in CBCT imaging.

Evaluation of the relationship between mandibular condyle cortication and chronologic age with cone beam computed tomography

PURPOSE

The aim of the present study is to evaluate the relationship between mandibular condyle cortication and chronologic age and gender via cone-beam computed tomography (CBCT) and to investigate the effectiveness of using the condylar cortication as a new method of age estimation.

METHODS

CBCT images from 433 subjects aged 8 to 31 years were included in this study. The right and left condyle cortication were assessed on the sagittal plane separately for each individual by the same investigator via a new method that describes the cortication of the condyle. Type I: There is no cortication on the condyle. Type II: The bone that is on the superior surface of the condyle is seen less density than the structures around the condyle. Type III: The surface of the condyle is seen similar or higher density than the surrounding cortical areas.

RESULTS

The type of the condyle cortication in the right and left mandible was similar for almost each subject and there was no statistically significant different between them (p = 0.375). When we evaluated the results without including these patients for male, Type I cortication of the condyle was seen at 14.14 ± 2.3 years, Type II cortication of the condyle was seen at 16.11 ± 3.18 years and Type III cortication of the condyle was seen at 19.39 ± 3.96 years. For the female, Type I cortication of the condyle was seen at 13.01 ± 2.16 years, Type II cortication of the condyle was seen at 15.52 ± 2.71 years and Type III cortication of the condyle was seen at 17.95 ± 3.13 years. The minimum age of Type III cortication was 11 and 15 years old for male and female, respectively. However, there are subjects, who are 30 year old man and 31 year old female, have no cortication as much as similar or higher than the surrounding the cortical areas.

CONCLUSION

This study is the first investigation of the relationship between condyle cortication and chronologic age with CBCT in the Turkish population. The type of cortication in the right and left condyle may be different for the same individual. Chronologic age increased as the stages of the cortication process from Type I to Type III in male and female individuals, and all the stages of the cortication in the mandibular condyle of male occur later time according to female.

Indications for cone beam computed tomography in children and young patients in a Turkish subpopulation

BACKGROUND

Cone beam computed tomography (CBCT) imaging is widely used in children; however, it remains controversial because of the health effects of radiation.

AIM

This retrospective study investigated the indications for CBCT and dentomaxillofacial pathologies in paediatric patients.

MATERIALS AND METHODS

CBCT images of 329 paediatric patients (i.e., aged <18 years) were investigated retrospectively. CBCT images were obtained with five fields of view (FOV). CBCT indications were categorised as surgery and orthodontics. The effects of age, sex, and FOV were evaluated. The level of significance was P = 0.05.

RESULTS

The most common orthodontic indications were malocclusion and dentomaxillofacial anomalies (38.5%), followed by the localisation of impacted teeth (33.1%). There was no relationship between sex and indications. There were significant associations between age groups and malocclusion and dentomaxillofacial anomalies, localisation of impacted teeth, and trauma. The face was the most frequently imaged region, followed by the jaws (maxilla and mandible).

CONCLUSION

The most common indication for CBCT was malocclusion and dentomaxillofacial anomalies in the primary and permanent dentition age groups, whereas the localisation of impacted teeth was the most common indication in the mixed dentition age group. Generally, CBCT was indicated in orthodontics and surgery.

Common 3-dimensional coordinate system for assessment of directional changes

INTRODUCTION

The aims of this study were to evaluate how head orientation interferes with the amounts of directional change in 3-dimensional (3D) space and to propose a method to obtain a common coordinate system using 3D surface models.

METHODS

Three-dimensional volumetric label maps were built for pretreatment (T1) and posttreatment (T2) from cone-beam computed tomography images of 30 growing subjects. Seven landmarks were labeled in all T1 and T2 volumetric label maps. Registrations of T1 and T2 images relative to the cranial base were performed, and 3D surface models were generated. All T1 surface models were moved by orienting the Frankfort horizontal, midsagittal, and transporionic planes to match the axial, sagittal, and coronal planes, respectively, at a common coordinate system in the Slicer software (open-source, version 4.3.1; http://www.slicer.org). The matrix generated for each T1 model was applied to each corresponding registered T2 surface model, obtaining a common head orientation. The 3D differences between the T1 and registered T2 models, and the amounts of directional change in each plane of the 3D space, were quantified for before and after head orientation. Two assessments were performed: (1) at 1 time point (mandibular width and length), and (2) for longitudinal changes (maxillary and mandibular differences). The differences between measurements before and after head orientation were quantified. Statistical analysis was performed by evaluating the means and standard deviations with paired t tests (mandibular width and length) and Wilcoxon tests (longitudinal changes). For 16 subjects, 2 observers working independently performed the head orientations twice with a 1-week interval between them. Intraclass correlation coefficients and the Bland-Altman method tested intraobserver and interobserver agreements of the x, y, and z coordinates for 7 landmarks.

RESULTS

The 3D differences were not affected by the head orientation. The amounts of directional change in each plane of 3D space at 1 time point were strongly influenced by head orientation. The longitudinal changes in each plane of 3D space showed differences smaller than 0.5 mm. Excellent intraobserver and interobserver repeatability and reproducibility (>99%) were observed.

CONCLUSIONS

The amount of directional change in each plane of 3D space is strongly influenced by head orientation. The proposed method of head orientation to obtain a common 3D coordinate system is reproducible.

The genial tubercle: A prospective novel landmark for the diagnosis of mandibular asymmetry

INTRODUCTION

Identifying menton (Me) on posteroanterior cephalograms and three-dimensional (3D) cone-beam computed tomography (CBCT) images is difficult, because the midpoint of the symphyseal area is not identifiable after the mandibular symphysis fuses at an early age. The aim of this study was to evaluate the reliability of the identification of the genial tubercle (GT) in patients with mandibular asymmetry and to compare it with that of the traditional landmark, Me.

METHODS

The samples comprised 20 CBCT images of adults with mandibular asymmetry. Two examiners performed the identifications and measurements. Me and GT were marked, and the anteroposterior, vertical, and transverse distances to the three reference planes were measured on 3D-reconstructed CBCT images. The intra- and inter-examiner reliability of landmark identification of Me and GT were assessed using the intraclass correlation coefficient (ICC) and Bland-Altman plots.

RESULTS

The Me and GT landmarks showed excellent reliability (ICC ≥ 0.993) three-dimensionally. In the transverse evaluation, the ICC values of the GT (range, 0.997-0.999) tended to be slightly higher than those of Me (range, 0.993-0.996). In the Bland-Altman plots for the two separate assessments, Me showed a maximum error of 1.76 mm in the transverse direction, whereas the GT showed a maximum error of 0.96 mm in the 95% limit.

CONCLUSIONS

Our results suggest that both Me and GT are clinically reliable and equally useful landmarks for the evaluation of mandibular asymmetry on CBCT images.

The use of three-dimensional imaging to evaluate the effect of conventional orthodontic approach in treating a subject with facial asymmetry

The growth of the craniofacial skeleton takes place from the 3(rd) week of intra-uterine life until 18 years of age. During this period, the craniofacial complex is affected by extrinsic and intrinsic factors which guide or alter the pattern of growth. Asymmetry can be encountered due to these multifactorial effects or as the normal divergence of the hemifacial counterpart occurs. At present, an orthodontist plays a major role not only in diagnosing dental asymmetry but also facial asymmetry. However, an orthodontist's role in treating or camouflaging the asymmetry can be limited due to the severity. The aim of this research is to report a technique for facial three-dimensional (3D) analysis used to measure the progress of nonsurgical orthodontic treatment approach for a subject with maxillary asymmetry combined with mandibular angular asymmetry. The facial analysis was composed of five parts: Upper face asymmetry analysis, maxillary analysis, maxillary cant analysis, mandibular cant analysis, and mandibular asymmetry analysis which were applied using 3D software InVivoDental 5.2.3 (Anatomage Company, San Jose, CA, USA). The five components of the facial analysis were applied in the initial cone-beam computed tomography (T1) for diagnosis. Maxillary analysis, maxillary cant analysis, and mandibular cant analysis were applied to measure the progress of the orthodontics treatment (T2). Twenty-two linear measurements bilaterally and sixteen angular criteria were used to analyze the facial structures using different anthropometric landmarks. Only angular mandibular asymmetry was reported. However, the subject had maxillary alveolar ridge cant of 9.96°and dental maxillary cant was 2.95° in T1. The mandibular alveolar ridge cant was 7.41° and the mandibular dental cant was 8.39°. Highest decrease in the cant was reported maxillary alveolar ridge around 2.35° and in the mandibular alveolar ridge around 3.96° in T2. Facial 3D analysis is considered a useful adjunct in evaluating inter-arch biomechanics.

Use of cone beam CT in children and young people in three United Kingdom dental hospitals

BACKGROUND

There is limited evidence about the use of cone-beam computed tomography (CBCT) in paediatric dentistry. Appropriate use of CBCT is particularly important because of greater radiation risks in this age group.

AIM

To survey the use of CBCT in children and young people in three Dental Hospitals in the United Kingdom (UK), with special attention paid to aspects of justification and optimisation.

DESIGN

Retrospective analysis of patient records over a 24-month period, looking at CBCT examinations performed on subjects under 18 years of age. Clinical indications, region of interest, scan field of view (FoV), incidental findings and exposure factors used were recorded.

RESULTS

There were 294 CBCT examinations performed in this age group, representing 13.7% of all scanned patients. CBCT was used more frequently in the >13 year age group. The most common use was for localisation of unerupted teeth in the anterior maxilla and the detection of root resorption. Optimisation of X-ray exposures did not appear to be consistent.

CONCLUSIONS

When planning a CBCT service for children and young people, a limited FoV machine would be the appropriate choice for the majority of clinical requirements. It would facilitate clinical evaluation of scans, would limit the number of incidental findings and contribute to optimisation of radiation doses.