Intraoral ultrasonography image registration for evaluation of partial edentulous ridge: A methodology and validation study.

OBJECTIVES: Ultrasound (US) reveals details for diagnosing soft- and hard-tissue dimensions around teeth, implants, and the edentulous ridge, not seen in 2D radiographs. Co-registering free-hand US scans with other 3D modalities presents reliability challenges. This study first aims to develop and validate a registration method to longitudinally reproduce US images of the jawbone on a simulator. In addition, it also evaluates the degree of the anatomical match in humans between US images acquired by the proposed registration method and the commonly used freehand acquisitions in comparison to cone beam computed tomography (CBCT) and intra-oral optical scan (IOS), used as references. METHODS: A previously introduced ultrasound phantom was employed as a CBCT-US hybrid, suitable for training and technique development of US guides in edentulous ridges. After establishing feasibility in the phantom, the methodology was validated in a cohort of 24 human subjects (26 cases). Soft tissues were delineated on US and IOS, and hard tissues on US and CBCT. US accuracy and repeatability from both guided and freehand scans (non-guided) was assessed as the average distance between US and the references. RESULTS: Guided US images resembled the references more closely than freehand (non-guided) scans. Notably, delineation of soft and hard tissues was significantly more accurate when employing guides. In the phantom, guided scans exhibited an absolute mean deviation of 81.8 µm for gingiva and 90.4 µm for bone, whereas non-guided scans showed deviations of 150.4 µm and 177.2 µm, respectively. Similarly, in vivo, guided US outperformed non-guided US, with gingiva deviations of 125 µm and 196 µm, and bone deviations of 354 µm and 554 µm, respectively. CONCLUSIONS: By using a registration method, guided US scans improved repeatability and accuracy of mapping hard and soft tissue of the edentulous ridge when compared to non-guided scans. CLINICAL RELEVANCE: This guided US imaging method could lay the foundation for longitudinal evaluation of tissue behavior and dimensional changes with improved accuracy.

Quantitative and qualitative comparisons of pulp cavity volumes produced by cone beam computed tomography and micro-computed tomography through semiautomatic segmentation: An ex vivo investigation.

OBJECTIVE: The aim of this study was to measure the volume and visually assess 3-dimensional (3D) virtual models of pulp cavities obtained through semiautomatic segmentation on images from 6 cone beam computed tomography (CBCT) units compared with the reference standard of micro-CT. STUDY DESIGN: Fifteen mandibular premolar teeth were scanned with 6 CBCT units: Prexion 3D Elite, i-CAT Next Generation, NewTom 5G, Cranex 3D, 3Shape X1, and Orthophos SL 3D, using the smallest available field of view and highest resolution settings. Pulp cavity volumes were quantitatively assessed by 2 calibrated examiners. The volumes from each CBCT unit were compared with micro-CT. Qualitative assessment of the 3D reconstructions was also performed. Repeated-measures analysis of variance and the Friedman test compared the CBCT reconstructions to micro-CT. Intra- and interexaminer agreements were calculated with the intraclass correlation coefficient and kappa statistic. RESULTS: The CBCT-based volumes were all significantly larger than micro-CT (P ≤ .0061). Prexion, X1, and Orthophos provided the segmentations that most closely resembled the reference standard. Intra- and interexaminer agreements ranged from good to excellent for quantitative measurements. Interexaminer agreement for qualitative evaluation was substantial. CONCLUSIONS: Semiautomatic segmentation of CBCT images is a feasible method to produce virtual 3D models of the pulp cavity. Prexion, X1, and Orthophos were the CBCT units that resulted in 3D reconstructions most similar to the reference standard.

Jaw tracking integration to the virtual patient: A 4D dynamic approach.

This dental technique describes a novel cost-effective workflow for integrating mandible kinematics into a static virtual patient. Computed tomography data are segmented and merged with intraoral surface scans and a target tracking video reproducing the mandible movements. A 4-dimensional dynamic virtual patient is created by using an open-source software program, and all patient-specific parameters can be exported for individualization of a virtual or analog articulator.

Lingual Lateral Canal Mimicking Mandible Fracture.

Lingual lateral canal is a rare variation in the trajectory of the mandibular canal, and is usually detected as an incidental finding on radiographic exams, especially on cone-beam computed tomography. Due to its radiographic characteristics, this anatomical variation might be confused with a mandible fracture. Therefore, the knowledge of its presence is essential not only to differentiate it from a fracture, but also for the success of surgical procedures performed in the mandible, making it easier to avoid clinical complications such as swelling, bruising, bleeding, and neurovascular disorders. This report shows the case of a lingual lateral canal mimicking a fracture on the mandibular body.

Can Mental Index be used on CBCT images to determine sexual dimorphism? / O Índice Mentual aplicado em imagens de TCFC pode ser utilizado para determinação do Dimorfismo Sexual?

ABSTRACT Objective: Radiomorphometric indices (RI) vary according to gender and age. The objective of this study was to assess bone quality in men and women, using tomographic images Methods: A total of 78 Cone Beam Computed Tomography (CBCT) images of female and male patients were analyzed. The images were obtained from LAPI-FOUSP database, São Paulo, Brazil, and the Mental Index, which is a quantitative index, was evaluated on those images. The images were divided into 2 groups: Group M - Men and Group W - Women and evaluated by one examiner in two different times (T1 and T2). The data was submitted to a statistical analysis with a 95% level of significance (p <0.05) Results: The ICC tests showed an average to good intra-examiner agreement. The age averages were: 48.46 ± 15.3 for group W and 53.87 ± 13.09 for group M. On the MI evaluation, statistically significant differences were observed between the two groups Conclusion: We concluded that MI can be used to determine sexual dimorphism, once the thickness of the mandible cortex in women is smaller than the thickness found in men.

RESUMO Objetivo: Avaliar o dimorfismo sexual, por meio da aplicação de IR em imagens tomográficas. Métodos: Foram analisados 78 exames de tomografia computadorizada de feixe cônico (TCFC), de pacientes do sexo feminino e masculino. As imagens foram obtidas do banco de dados do LAPI-FOUSP, São Paulo, Brasil, e por meio delas o Índice Mentual, que é um IR quantitativo, foi avaliado. As imagens foram divididas em 2 grupos: Grupo M - Homens e Grupo W - Mulheres e avaliadas por um examinador em dois tempos diferentes (T1 e T2). Os dados foram submetidos a análise estatística com nível de significância de 95% (p<0,05). Resultados: O teste ICC mostrou uma concordância intra-examinador média a boa. As médias de idade foram: 48,46±15,3 para o grupo M e 53,87±13,09 para o grupo H. Na avaliação do IM, foram observadas diferenças estatisticamente significantes entre os dois grupos. Conclusão: Concluímos que o Índice Mentual pode ser utilizado para determinar o dimorfismo sexual, uma vez que a espessura da cortical da mandíbula nas mulheres é menor que a espessura encontrada nos homens.

Patient movement characteristics and the impact on CBCT image quality and interpretability.

OBJECTIVES: To assess the impact of patient movement characteristics and metal/radiopaque materials in the field-of-view (FOV) on CBCT image quality and interpretability. METHODS: 162 CBCT examinations were performed in 134 consecutive (i.e. prospective data collection) patients (age average: 27.2 years; range: 9-73). An accelerometer-gyroscope system registered patient's head position during examination. The threshold for movement definition was set at ≥0.5-mm movement distance based on accelerometer-gyroscope recording. Movement complexity was defined as uniplanar/multiplanar. Three observers scored independently: presence of stripe (i.e. streak) artefacts (absent/"enamel stripes"/"metal stripes"/"movement stripes"), overall unsharpness (absent/present) and image interpretability (interpretable/not interpretable). Kappa statistics assessed interobserver agreement. χ2 tests analysed whether movement distance, movement complexity and metal/radiopaque material in the FOV affected image quality and image interpretability. Relevant risk factors (p ≤ 0.20) were entered into a multivariate logistic regression analysis with "not interpretable" as the outcome. RESULTS: Interobserver agreement for image interpretability was good (average = 0.65). Movement distance and presence of metal/radiopaque materials significantly affected image quality and interpretability. There were 22-28 cases, in which the observers stated the image was not interpretable. Small movements (i.e. <3 mm) did not significantly affect image interpretability. For movements ≥ 3 mm, the risk that a case was scored as "not interpretable" was significantly (p ≤ 0.05) increased [OR 3.2-11.3; 95% CI (0.70-65.47)]. Metal/radiopaque material was also a significant (p ≤ 0.05) risk factor (OR 3.61-5.05). CONCLUSIONS: Patient movement ≥3 mm and metal/radiopaque material in the FOV significantly affected CBCT image quality and interpretability.