Evaluation of masseter muscle in different vertical skeletal patterns in growing patients.

AIM: The present study aimed to evaluate the relationship between masseter size, maxillary intermolar width and craniofacial vertical skeletal pattern. STUDY DESIGN: The study followed a prospective longitudinal design and enrolled 61 subjects (30 males and 31 females), 9-14 years of age (mean age 11.5) at 2-3 CVM stage. The participants were divided into three groups based on their vertical skeletal pattern which was estimated using the Frankfurt-mandibular plane angle: low-angle group (L-A), normal-angle group (N-A), high-angle group (H-A). An additional gender-based distinction was made. Maxillary intermolar width was measured on the maxillary cast of each patient by means of an electronic caliper; masseter volume was estimated by using magnetic resonance (MR) and masseter thickness was measured by means of ultrasonography (US). The US registrations were performed during the relaxation state (RS) and the maximum voluntary contraction (MVC) of the muscle. The indipendent samples T- test was used for sex comparisons; the analysis of variance test (ANOVA) was used to evaluate the differences between the three groups in males and females, and the Pearson r correlation coefficient was employed to assess the correlation between maxillary intermolar width and masseter volume. RESULTS AND CONCLUSION: Maxillary intermolar width, masseter volume and thickness showed significant gender differences; all the tested variables decreased significantly according to the facial vertical pattern, with greater values in females, especially in low- and normal-angle subjects; maxillary intermolar width and masseter volume showed significant correlations, higher in females.

Clinical value of 12 occlusal features for the prediction of disc displacement with reduction (RDC/TMD Axis I group IIa).

The purpose of this study is to quantify the clinical value of 12 occlusal variables for the prediction of disc displacement with reduction diagnosed according to research diagnostic criteria (RDC)/temporomandibular disorder (TMD). Twelve occlusal features were clinically assessed by the same three operators. The sample consisted of 165 TMD patients (65 males, 100 females; mean age: 32.55 +/-11.685 years) with only disc displacement with reduction (RDC/TMD Axis I group IIa) and a control sample of 145 healthy subjects (65 males, 80 females; mean age:31.24+/-12.436 years) diagnosed with RDC/TMD Axis I group 0. A stepwise multiple logistic regression model was used to identify the significant correlation between occlusal features and disease. The odds ratio for disc displacement was 2.84 for absence of canine guidance, 2.14 for mediotrusive interference and 1.75 for retruded contact position (RCP)/maximum intercuspation (MI) slide >or=2 mm. Other occlusal variables did not reveal to be statistically significant. The percentage of the total log likelihood for disc displacement explained by the significant occlusal factors was acceptable with a Nagelkerke's R(2) = 0.124. The final model including the significant occlusal features revealed an optimal discriminant capacity to predict patients with disc displacement with a sensitivity of 63.6% or with a specificity of 64.8% for healthy subjects and an accuracy of 64.2%. Occlusal features showed a low predictive value for detecting disc displacement. Multifactorial complex pathologies such as TMD should be investigated using a multivariate statistical analysis; moreover,the future of aetiopathogenic research in this matter requires a multifactorial approach.

Sample size calculation for studies on temporomandibular disorders.

Sample size calculation is a fundamental step for the validity and the usefulness of results from a study. Nevertheless, as demonstrated by some papers in the literature, such calculation is often ignored. Despite the lack of papers on this topic, it is probable that this shortcoming also affects studies on temporomandibular disorders. Therefore, the aim of this paper was to provide some basic rules to calculate the sample size necessary for different types of studies, both longitudinal and transversal, on those pathologies. Some examples of the application of such rules for different types of studies have also been provided, in order to make a full comprehension easier. In fact, the systematic application of those rules is strongly requested for the effective usefulness of results. Furthermore, an analysis of the statistical power of past studies on temporomandibular disorders could be useful to evaluate if our epidemiological and clinical-therapeutic knowledge of temporomandibular disorders is effectively based upon studies conducted with the appropriate sample size.