Magnetic Resonance Imaging Assessment of Articular Disc Position in Temporomandibular Disorder Subjects with various Bite Registrations

Objective: This study aimed to evaluate the validity and reliability of three bite registrations on articular disc position in temporomandibular disorder patients using magnetic resonance imaging (MRI). Materials and Methods: Fifteen clinically symptomatic and orthodontically untreated temporomandibular disorder patients within the age range of 17–40 years (mean age: 28.5 years) were examined. Each patient was subjected to three bite registrations, namely maximum intercuspation, initial contact bite and Roth power centric bite, and evaluated with MRI. Results: On the right side, the mean vertical and horizontal measurement values of the point in the most posterior aspect of the posterior band of the articular disc in relation to horizontal reference line (HRL) and vertical reference line (VRL) in the sagittal view in the Roth power centric bite were lesser (2.720 ± 1.239 mm and 2.380 ± 1.185 mm, respectively), in comparison with the other two bites, and on the left side too, it was lesser in the Roth power centric bite (2.293 ± 0.979 mm and 2.360 ± 1.078 mm, respectively), when compared to the other two bites. Statistical analysis also showed the significance of Roth power centric bite over the other two bites. Conclusions: Favourable articular disc positional changes were observed in the Roth power centric bite followed by the initial contact bite and that maximum disc recapture was observed in most patients with the Roth power centric bite rather than in initial contact bite and maximum intercuspation positions. The Roth power centric bite could be assumed to be the ideal method for articulation and fabrication of gnathological splints for treating patients with temporomandibular disorders.

Comparison of condylar displacement between three biotypological facial groups by using mounted models and a mandibular position indicator / 대한치과교정학회지

OBJECTIVE: Facial-type-associated variations in diagnostic features have several implications in orthodontics. For example, in hyperdivergent craniofacial types, growth imbalances are compensated by displacement of the condyle. When diagnosis and treatment planning involves centric relation (CR), detailed knowledge of the condylar position is desirable. The present study aimed to measure condylar displacement (CD) between CR and maximum intercuspation in three facial types of an asymptomatic orthodontic population. METHODS: The study was conducted in 108 patients classified into three groups of 36 individuals each (27 women and 9 men; mean age, 20.5 years), based on the following facial patterns: hyperdivergent, hypodivergent, and intermediate. To quantify CD along the horizontal and vertical axes, the condylar position was analyzed using mounted casts on a semi-adjustable articulator and a mandibular position indicator. The Student t-test was used to compare CD between the groups. RESULTS: Vertical displacement was found to be significantly different between the hyperdivergent and hypodivergent groups (p < 0.0002) and between the hyperdivergent and intermediate groups (p < 0.0006). The differences in horizontal displacement were not significant between the groups. In each group, vertical CD was more evident than horizontal displacement was. CONCLUSIONS: All facial types, especially the hyperdivergent type, carried a significantly high risk of CD. Therefore, the possibility of CD should be carefully evaluated and considered in the assessment of all orthodontic cases in order to accurately assess jaw relationships and avoid possible misdiagnosis.

Análise oclusal de pacientes com má-oclusão de classe II, tratados com extrações de 4 pré-molares / Occlusal analysis of patients with malocclusion of class II, treated with extractions to 4 bicuspid

Para determinar a estabilidade dos resultados oclusais, após tratamento ortodôntico, realizou-se um estudo comparativo do número de pontos de contato oclusais na posição de máxima intercuspidação habitual em uma amostra composta por 14 pacientes leucodermas, sendo 9 do sexo feminino e 5 do sexo masculino, com má-oclusão de Classe II, divisão 1ª de Angle, tratados ortodonticamente com a técnica de Edgewise, e extração dos 4 primeiros pré-molares. Estes pontos foram registrados em dois tempos: T1 - ao final da fase de contenção superior e T2 - após um período médio de 5,2 anos. A contagem dos contatos oclusais foi realizada, separadamente, no arco superior e inferior, na região anterior e posterior. Depois da análise estatística, pôde-se concluir que não houve diferença estatisticamente significante entre o número médio de contatos oclusais nos diferentes períodos estudados.

A study comparing the number of occlusal contact points in maximum habitual intercuspation in a sample composed by 14 leucoderm patients, 9 female and 5 males, Angle Class II division 1 mallocclusion, treated using Edgewise technique, with extrations of the 4 first pre-molars. These points were registered in two times: T1 – at the end of superior retainer phase and T2 - after an average period of 5,2 years. The analysis verified the total points of contact of the upper and lower arches, separately. After the statistic analysis, it can be concluded that there were no significant differences between the average number of occlusal contacts in T1 and T2.