Trial data for precision analysis of a three-dimensional mandibular mechanical advantage.

The data presented in this manuscript describe craniofacial landmark coordinate values, muscle and load moment arm lengths, and mechanical advantage rates for constructing a three-dimensional model of masticatory muscles. Cone-beam computed tomography scans from 30 subjects (aged 12-19 years, 16 females) were used. Thirty-six craniofacial landmarks were identified. Subsequently, the moment arms for 7 muscles and their corresponding load moment arms at incisor and molar positions were determined. Then, the three-dimensional mechanical advantage for each muscle and tooth position was calculated as the ratio of muscle moment arm to load moment arm. This procedure was repeated three times by a main examiner and once by two other examiners. The Friedman test and the square root of the 'method of moments' variance estimator were used to compare data among examiners and calculate random errors, respectively. Although the values for the craniofacial landmark coordinates and biomechanical variables are very close, differences were found between measurements, especially in the interexaminer comparisons. Values served as the basis for reliability (intraclass correlation coefficient) and errors (average mean of absolute differences) analysis in the research paper titled "A three-dimensional method to calculate mechanical advantage in mandibular function: Intra- and interexaminer reliability study," published in the Journal of Orofacial Orthopedics.

A three-dimensional method to calculate mechanical advantage in mandibular function : Intra- and interexaminer reliability study.

PURPOSE: Masticatory muscles are physically affected by several skeletal features. The muscle performance depends on muscle size, intrinsic strength, fiber direction, moment arm, and neuromuscular control. To date, for the masticatory apparatus, only a two-dimensional cephalometric method for assessing the mechanical advantage, which is a measure for the ratio of the output force to the input force in a system, is available. This study determined the reliability and errors of a three-dimensional (3D) mechanical advantage calculation for the masticatory system. METHODS: Using cone-beam computed tomography images from teenage patients undergoing orthodontic treatments, 36 craniofacial landmarks were identified, and the moment arms for seven muscles and their load moment arms (biomechanical variables) were determined. The 3D mechanical advantage for each muscle was calculated. This procedure was repeated by three examiners. Reliability was verified using the intraclass correlation coefficient (ICC) and the errors by calculating the absolute differences, variance estimator and coefficient of variation (CV). RESULTS: Landmark coordinates demonstrated excellent intra- and interexaminer reliability (ICC 0.998-1.000; p < 0.0001). Intraexaminer data showed errors < 1.5 mm. Unsatisfactory interexaminer errors ranged from 1.51-5.83 mm. All biomechanical variables presented excellent intraexaminer reliability (ICC 0.919-1.000, p < 0.0001; CV < 7%). Interexaminer results were almost excellent, but with lower values (ICC 0.750-1.000, p < 0.0001; CV < 10%). However, the muscle moment arm and 3D mechanical advantage of the lateral pterygoid muscles had ICCs < 0.500 (p < 0.05) and CV < 30%. Intra- and interexaminer errors were ≤ 0.01 and ≤ 0.05, respectively. CONCLUSIONS: Both landmarks and biomechanical variables showed high reliability and acceptable errors. The proposed method is viable for the 3D mechanical advantage measure.

Correlation between cervical vertebrae maturation and midpalatal suture fusion in patients aged between 10 and 20 years: A cross-sectional and 3D study.

OBJECTIVE: This study aimed to correlate the cervical vertebrae maturation (CVM) stages with the bone fusion stages of the midpalatal suture (MPS). MATERIALS AND METHODS: The sample consisted of 351 cone-beam computed tomographies (CBCTs) of patients divided into two groups: 10-15 years old and 16-20 years old. Both CVM and MPS stages were correlated using Spearman's correlation analysis. To assess the diagnostic performance of the CVM stages in identifying the bone fusion stages of the MPS, the likelihood ratio (LHR) test was applied. RESULTS: In the whole sample, a low positive correlation was found between CVM and MPS bone fusion level (P<0.001; Rho=0.395). In the younger age group, the correlation was moderate in the male (P<0.001; Rho=0.616) and low in the female (P<0.001; Rho=0.394) patients. In the 16-20 years age group, there was no correlation between CVM and MPS fusion. A moderate increase in the probability of determining CS1 for stage A (38%) and CS2 for stage B (42.2%) of MPS ossification was found among the 10-15 year old female patients. CONCLUSION: A low and moderate positive correlation was found between CVM and MPS level of bone fusion in female and male patients respectively, but the diagnostic performance of the CVM stages in the identification of MPS bone fusion stages did not have a high correlation. Therefore, the CVM stages indicated no conclusive probability of determining the MPS bone fusion stage.