Efeitos do posicionamento sagital da mandíbula na morfometria das vias aéreas superiores / Efects of sagital positioning of the mandibule in upper airway morphometry

O objetivo do presente estudo foi analisar as dimensões das vias aéreas superiores (VAS) em indivíduos com diferentes posicionamentos sagitais da mandíbula, bem como a sua relação com o comprimento efetivo mandibular (CoGn). A amostra foi constituída por 63 exames de tomografia computadorizada de feixe cônico (TCFC) de indivíduos com idade entre 13 e 35 anos, alocados em três grupos conforme os valores angulares de SNB: grupo com retrognatismo mandibular (RMand); grupo com posicionamento normal da mandíbula (NMand) e grupo com prognatismo mandibular (PMand). Com o auxílio do programa Dolphin Imaging® (versão 11.95 Premium), as VAS foram subdivididas em Nasofaringe (NF), Orofaringe (OF) e Hipofaringe (HF), e o volume (Vol) e área axial mínima (Axmin) de cada região mensurados, assim como a altura (Alt) da OF e HF. A medida linear CoGn também foi averiguada e sua influência sobre as dimensões das VAS avaliada. MANCOVA foi utilizada para comparar o conjunto de variáveis das VAS entre os grupos de acordo com o padrão mandibular. Além disso, modelos de regressão linear foram implementados para estimar, independentemente, o efeito x do SNB e CoGn nas dimensões das VAS. Indivíduos com prognatismo mandibular apresentaram medidas significativamente maiores para NF-Axmin e OF-Vol, quando comparados aos indivíduos que mostraram normalidade e retrognatismo mandibular (P < 0,05). Não foram observadas diferenças entre os grupos para quaisquer das outras medidas consideradas no estudo. A variável CoGn foi relacionada às medidas de volume de todas as regiões avaliadas das VAS e também à HF-Alt. Concluiu-se que indivíduos com prognatismo mandibular apresentaram, de modo expressivo, maior área axial mínima da Nasofaringe e maior volume da Orofaringe quando comparados àqueles com normalidade e retrognatismo mandibular; destacando-se que o comprimento efetivo mandibular demonstrou ser um preditor mais relevante nas dimensões das VAS em comparação ao SNB. (AU)

The aim of the present study was to analyze the dimensions of the upper airways (UA) in individuals with different sagittal positioning of the mandible, as well as its relationship with the effective mandibular length (CoGn). The sample consisted of 63 cone beam computed tomography (CBCT) scans of individuals aged between 13 and 35 years, allocated into three groups according to the angular values of SNB: Group with Mandibular Retrognathism (RMand); Group with Normal Jaw and Group with Mandibular Prognathism (PMand). Using Dolphin Imaging® program (version 11.95 Premium), the UA were subdivided into Nasopharynx (NP), Oropharynx (OP) and Hypopharynx (HP), and the volume (Vol) and minimum axial area (Axmin) of each region measured, as well as the total height (Ht) of the OP and HP. The linear measure CoGn was also investigated and its influence on the dimensions of the VAS evaluated. MANCOVA was used to compare the set of VAS variables between the groups according to the mandibular pattern. In addition, linear regression models were implemented to independently estimate the effect of SNB and CoGn on UA xii dimensions. Individuals with mandibular prognathism had significantly higher measurements for NP-Axmin and OP-Vol, when compared to individuals with harmony and mandibular retrognathism (P < 0.05). No differences were observed between groups for any of the other measures considered in the study. The CoGn variable was related to the volume measurements of all the evaluated regions of the UA and also to the HP-Ht. It was concluded that individuals with mandibular prognathism significantly presented a greater minimum axial area of the Nasopharynx and greater volume of the Oropharynx when compared to those with harmony and mandibular retrognathism; highlighting that the effective mandibular length proved to be a more relevant predictor in the dimensions of the UA compared to the SNB. (AU)

The internal anatomy of danger zone of mandibular molars: A cone-beam computed tomography study.

AIM: The aim of this study was the assessment of the anatomical thickness of danger zone in the cervical third of mesial canals of mandibular molars. MATERIALS AND METHODS: Fifty mandibular molars were selected and scanned with cone-beam computed tomography. Data were compared using a length tool provided by scanner software. The measured areas were the mesial and distal walls of the cervical third of the mesial roots, which correspond to the safety and danger zones, respectively. In addition, dentin thickness at the furcation was evaluated. RESULTS: Dentin thicknesses of the safety zone were higher than in the danger zone in all teeth examined. The thinnest dentin of the safety zone was found at a point located 4 mm below the canal orifice, with a mean value of 1.03 mm; conversely, in the danger zone, the thinnest point was located 3 mm below the orifice, with a mean value of 0.81 mm. As for the distance from the pulp chamber floor to the furcation, the average value was 2.23 mm. CONCLUSION: These results show that mean thicknesses at the danger zone of mandibular molar mesial roots were <1.0 mm. These data reinforce the importance of understanding anatomy and the need for conservative preparations when assessing and instrumenting these root canals.