Shape differences among symmetrically shaped skeletal growth patterns in a panoramic view: a Fourier analysis

Abstract The objective of this study was to apply elliptic Fourier analysis (EFA) to find shape differences among skeletal growth patterns in both radiographic and tomographic panoramic views, controlling for asymmetry. Lateral and panoramic images were obtained from 350 patients. After screening patients with asymmetric linear and angular values and natural asymmetric hemimandibular shape, 240 patients were included in the study: 48 with tomographic information and 192 with radiographic information. The images were classified according to the mandibular plane angle and the ANB angle. Mandibular contours were digitized on the panoramic images and EFA was performed with 20 harmonics, filtering rotation, translation and size properties. As there were no differences between radiographic and tomographic panoramic mandibular contours and normal distribution was found in all groups, MANOVA was conducted to determine differences using a Hotelling's p-values with Bonferroni correction and an XY graph tool was applied to visualize these differences graphically. A 95% confidence level was used. Significative differences were found among hypodivergent, normodivergent, and hyperdivergent patterns in Class I, II, and III (p < 0.05), located mainly in the symphyseal region. The results of this study suggest that EFA is a useful tool to mathematically analyze mandibular contours and their morphological differences given by facial biotypes. This method could improve the precision of the mandibular prediction models.

Dosimetry in CBCT with Different Protocols: Emphasis on Small FOVs Including Exams for TMJ

Abstract This study aimed to estimate the absorbed dose in cone beam computed tomography (CBCT) exams according to different exposure parameters and size and position of the field of view (FOV). In addition was compared the absorbed dose of two smaller FOV scans with that of a larger FOV scan for evaluation of temporomandibular joint (TMJ), as it is a bilateral structure. CBCT scans were obtained on OP300 Maxio unit varying scanning mode (standard, high and endo) as well as size (5x5, 6x8 and 8x15 cm) and positioning of FOV. With a small FOV, different areas were scanned (maxilla or mandible, anterior or posterior and TMJ). Absorbed doses were determined using thermoluminescent dosimeters on the skin surface of sensitive organs of an anthropomorphic phantom. Endo mode showed the highest dose, followed by the high and standard modes in all FOV positions. With small FOV, doses were higher in the posterior region, especially in the mandible. Dose reduction occurred when small FOVs were used, but it was not proportional to FOV size reduction. For TMJ, the dose in a single acquisition with large FOV was greater than two acquisitions with small FOV, but lower than two acquisitions with medium FOV (6x8 cm). In conclusion, scanning mode, size and FOV position have great influence on the absorbed dose. Small FOV decreases the dose, but there is no linear relation between FOV size and dose. For bilateral exams of TMJ, double acquisition with small FOVs produces decrease in absorbed dose relative to a large FOV.

Resumo O objetivo deste estudo foi estimar a dose absorvida em exames de tomografia computorizada de feixe cônico (TCFC) de acordo com diferentes parâmetros de exposição, tamanho e posição do campo de visão (FOV, do inglês field of view). Além disso, comparou-se a dose absorvida em uma única aquisição com FOV grande com aquela em duas aquisições com FOVs menores para avaliação de estruturas bilaterais como a articulação temporomandibular (ATM). As aquisições de TCFC foram obtidas no aparelho OP300 Maxio, variando o modo de aquisição (standard, high e endo), bem como o tamanho (5x5, 6x8 e 8x15 cm) e o posicionamento do FOV. Com o FOV pequeno, foram escaneadas diferentes áreas (maxila ou mandíbula, anterior ou posterior e ATM). As doses absorvidas foram determinadas por meio da utilização de dosímetros termoluminescentes na superfície da pele em órgãos sensíveis de um phantom antropomórfico. O modo endo mostrou a dose mais alta, seguido pelos modos high e standard em todas as posições dos FOVs. Com um FOV pequeno, as doses foram maiores na região posterior, especialmente na mandíbula. A redução da dose ocorreu quando foram utilizados pequenos FOVs; contudo, essa redução não foi proporcional à redução do tamanho do FOV. Para a ATM, a dose em uma única aquisição com FOV grande foi maior que duas aquisições com FOV pequeno, porém inferior à dose de duas aquisições com FOV médio (6x8 cm). Em conclusão, o modo de aquisição, o tamanho e a posição do FOV têm grande influência na dose absorvida. FOVs pequenos apresentaram doses mais baixas em relação aos FOVs grandes, entretanto não há uma relação linear entre o tamanho do FOV e a dose absorvida. Para estruturas bilaterais como a ATM, a dupla aquisição com FOV pequeno representa uma diminuição na dose absorvida em relação a uma aquisição com FOV grande.

Changes in root canal anatomy using three nickel-titanium rotary system: a cone beam computed tomography analysis

AIM: Cone beam computed tomography (CBCT) was used to evaluate the ability of three NiTi rotary systems to maintain the original root canal anatomy. METHODS: Sixty mesiobuccal canals of human mandibular first molars were divided into three groups with 20 root canals each. All teeth were scanned by CBCT before instrumentation. The images were captured digitally for further analysis using the Image Tools Software. The images were sectioned in three points, located at 9 mm, 6 mm and 3mm from the apex. In Group 1, the root canals were instrumented with ProTaper UniversalTM rotary system; in Group 2, with Twisted FileTM rotary system; and in Group 3, with MtwoTM rotary system. Instrumented teeth were scanned again using CBCT and the images of the uninstrumented canals were compared with images of the instrumented canals. The results were statistically analyzed using the one-way ANOVA test. A level of significance of 0.05 was adopted. RESULTS: The means of D1 at distances of 9 mm, 6 mm, and 3 mm from the apex were, respectively: Group 1: 0.88±0.257, 1.00±0.000, and 1.00±0.000; Group 2: 0.79±0.745, 0.65±0.669, and 0.25±0; Group 3: 0.50±0.745, 0.33±0.472, and 0.03±0.104. The means of D2 at distances of 9 mm, 6mm, and 3mm from the apex were respectively: Group 1: 1.00±0.00, 1.00±0.00, and 1.00±0.00; Group 2: 0.41±0.299, 0.30±0.428, and 0.50±0.707; Group 3: 0.58±0.910, 0.85±1.857, and 0.31±0.643. CONCLUSIONS: The CBCT analysis revealed that the ProTaper UniversalTM produced centered preparations and while the Twisted FileTM and MtwoTM rotary systems produced canal deviation.

Study of the Internal Morphology of the Mesiobuccal Root of Upper First Permanent Molar Using Cone Beam Computed Tomography / Estudio de la Morfología Interna de la Raíz Mesiovestibular del Primer Molar Superior Permanente por Medio de Tomografía Computarizada Cone Beam

The aim of this study was to investigate and classify the internal morphology of the mesiobuccal root of upper first permanent molar, using the cone beam computed tomography. A total of 60 first permanent molars, not healthy and with intact pulp cavity, belonging to the Postgraduate dentistry bank, underwent the computed tomography. Axial images of each tooth were analyzed, and results showed that according to the number of conduits, 21 specimens (35 percent) had single conduit and 39 exhibited two conduits (65 percent). In reference to the types of internal configuration most commonly found according to Vertucci classification; type I (single channel that extends from the pulp chamber to the apex) was the most frequent (35 percent), followed by type II (two separate canals leaving the pulp chamber and joining next to the apex forming a single channel) with 30 percent. It was found that the morphology of the variation of mesiobuccal root, of upper first permanent molar is relatively high, and computed tomography proved to be an effective method for diagnosis.

El objetivo de este estudio fue investigar y clasificar la morfología interna de la raíz mesiovestibular del primer molar permanente superior, utilizando la tomografía computarizada cone beam. Fueron utilizados 60 primeros molares permanentes superiores, pertenecientes al Banco de Dientes del Posgrado en Odontología, con cavidad pulpar intacta, los cuales fueron sometidos a TC. Se analizaron las imágenes axiales de cada diente y se obtuvieron los siguientes resultados: 21 muestras (35 por ciento) tenían un solo canal y 39 muestras (65 por ciento) dos canales; los tipos de configuración interna más comunes de acuerdo a la clasificación Vertucci fueron: Tipo I, 35 por ciento, un solo canal que se extiende desde la cámara pulpar hasta el ápice radicular y Tipo II, 30 por ciento dos canales separados que salen de la cámara pulpar y se unen cerca del ápice radicular formando un solo canal. La morfología de la raíz mesiovestibular del primer molar superior era relativamente alta. La tomografía computarizada demostró ser un método eficaz para el diagnóstico.

Relação topográfica entre o canal mandibular e o terceiro molar inferior em tomografias de feixe volumétrico / Relationship between the mandibular canal and third molar in cone beam tomography

O canal mandibular, por onde circunda o nervo alveolar inferior, localiza-se abaixo das raízes dos dentes molares, estendendo-se até o forame mentoniano, onde se bifurca, dando origem ao nervo mentoniano, dificilmente visível nas radiografias. Seu tamanho e localização, em relação aos ápices dentários, são variáveis, podendo apresentar variações anatômicas. O terceiro molar está mais intimamente relacionado com ele, especialmente quando não irrompido. Dessa forma, a correta identificação anatômica do canal mandibular é essencial, quando é preciso praticar-se a exérese desses dentes, dentre outros procedimentos na área odontológica,visto que a lesão nervosa decorrente desse ato cirúrgico pode causar transtornos para o profissional do ponto de vista legal. O objetivo deste estudo foi o de avaliar a topografia anatômica do canal mandibular em relação aos ápices dos terceiros molares através de imagens tomográficas de 25 humanos de um banco de dados bem como a relação do ápice radicular do 3º molar inferior com a cortical superior do canal mandibular. Pode ser classificado como estudo de validação de diagnóstico. Dos pacientes pesquisados, a maioria foi do sexo feminino (68%), predominando a faixa etária dos 20 aos 30 anos de idade, e a média da distância de um dos lados escolhidos aleatoriamente da raiz do terceiro molar inferior à cortical superior do canal mandibular foi de 1,24 milímetros. Com base nos resultados obtidos nesse estudo, é possível concluir que as tomografias de feixe cônico foram eficientes para a realização das mensurações propostas no presente trabalho.

The mandibular canal, which is surrounded by the inferior alveolar nerve, is located below the roots of the molar teeth, extending to the mental foramen, where it divides, giving rise to the mental nerve, and is hardly visible on radiographs. Its size and location in relation to the dental apices are variable and may present anatomical differences. The third molar is more closely related to it, especially when not erupted. Thus, the correct anatomical identification of the mandibular canal is essential when these teeth need to be extracted, among other dental procedures, since the nerve injury resulting from such surgery may have undesirable legal repercussions for the professional. The aim of this study was to evaluate the anatomic topography of the mandibular canal in relation to the apex of third molars through topographic images of 25 men from a database, and the relationship of the root apex of the 3rd molar to the cortical surface of the mandibular canal. It can be classified as a validation study of diagnosis. Of the patients surveyed, the majority were female (68%), predominantly in their twenties, and the mean distance from one of the randomly chosen sides of the root of the lower third molar to the upper cortical surface of the mandibular canal was 1.24 mm. Based on the results of this study we conclude that the cone beam CT scans were efficient for carrying out the measurements proposed in this study.