Anatomical characteristics of mandibular bone in skeletal class I, II and III patients by using cone beam computed tomography images in an iranian population / Características anatômicas do osso mandibular em pacientes Classe I, II e III esquelética usando imagens de Tomografia Computadorizada de Feixe Cônico: em uma População Iraniana

Objetive: This study aimed to compare the anatomical characteristics of the mandible in patients with skeletal class I, II and class III disorders using cone beam computed tomography (CBCT). Material and Methods: CBCT scans of patients between 17 to 40 years taken with NewTom 3G CBCT system with 12-inch field of view (FOV) were selected from the archive. Lateral cephalograms were obtained from CBCT scans of patients, and type of skeletal malocclusion was determined (Class I, II or III). All CBCT scans were evaluated in the sagittal, coronal and axial planes using the N.N.T viewer software. Results: The ramus height and distance from the mandibular foramen to the sigmoid notch in class II patients were significantly different from those in skeletal class I (P < 0.005). Distance from the mandibular canal to the anterior border of ramus in class III individuals was significantly different from that in skeletal class I individuals (P < .005). Conclusion: Length of the body of mandible in skeletal class I was significantly different from that in skeletal class II and III patients. Also, ramus height in skeletal class I was significantly different from that in skeletal class II patients. CBCT had high efficacy for accurate identification of anatomical landmarks. (AU)

Objetivo: Este estudo teve como objetivo comparar as características anatômicas da mandíbula em pacientes com desordem esquelética Classe I, II e III usando imagens de tomografia computadorizada de feixe cônico (TCFC). Material e Métodos: Foram selecionadas de arquivo, imagens de TCFC (Sistema NewTon 3G) com FOV (campo de visão) 12 polegadas e incluindo pacientes entre 17 a 40 anos. Cefalometrias laterais foram obtidas a partir das imagens de TCFC e o tipo de maloclusão esquelética foi determinada (Classe I, II ou III). Todas as imagens de TCFC foram avaliadas nos planos sagital, coronal e axial usando o software de visualização N.N.T. Resultados: A altura do ramo e distância do forame mandibular para a incisura da mandíbula em pacientes Classe II foi significativamente diferente daqueles Classe I esquelética (p< 0.005). A distância do canal mandibular até a borda anterior do ramo em indivíduos Classe III foi significativamente diferente daqueles indivíduos Classe I esquelética (p<0.005). Conclusão: O comprimento do corpo da mandíbula na Classe I esquelética foi diferente significativamente daqueles pacientes em Classe II e III esquelética. Além disso, a altura do ramo na Classe I esquelética foi significativamente diferente daqueles pacientes Classe II esquelética. A TCFC apresentou alta eficácia para a identificação precisa de marcos anatômicos. (AU)

Effect of Head Position on Maxillofacial Transverse Measurements Made on the Skull and Cone Beam Computed Tomography Scans

Article Incorrect patient positioning and the resultant image distortion occur in many radiographic examinations. This study aimed to assess the effect of tilting, rotation and tipping of the head on the accuracy of maxillofacial transverse measurements made on cone beam computed tomography (CBCT) scans. The CBCT scans were obtained in central position of 10 dry human skulls. Using three-dimensional (3D) Dolphin software, six positions namely 10° and 20° tilts, rotations and tips were reconstructed of central position. Transverse distances between landmarks were measured on 3D scans and the skulls. The intraclass correlation coefficient (ICC) and the Bland-Altman plot were used to compare the mean values measured by the two observers. For most landmarks, no significant differences were noted between the mean transverse distances measured in the six positions and those measured in central position on 3D scans (p>0.005). In conclusion, all measurements of transverse distances made on 3D scans in different positions were underestimated compared to the actual values measured on the skull.