Evaluation of anthropometric measurements of musculus masseter and os mandibula of patients referred to the otorhinolaryngology outpatient clinic of a university hospital using MR images

Objective: Bones are not static structures in the human body; they continue to change throughout a lifetime. The German anatomist and surgeon Julius Wolff developed a law that explains the nature of bone remodeling due to stress. Wolff's law states that bones will adapt to the degree of mechanical loading, so that an increase in loading will result in strengthening of the architecture of the internal cancellous bone and subsequent strengthening of the cortical layer. This law indicates that the internal structure and shape of bone is closely related to function and describes the relationship between bone shape and muscle function. The importance of masticatory muscle function on the basic mechanisms of craniofacial growth has been demonstrated in a variety of animal and human experimental studies. Clinical studies are mostly done by force, by measuring the electromyographic (EMG) activity of these muscles or by measuring their cross-sectional thickness by computed tomography, magnetic resonance imaging (MRI) and ultrasonography. Masseter muscle thickness enhances sagittal growth and limits vertical growth of the jaws. It tends to enlarge the face in a more horizontal arrangement. Age, gender and ethnicity also produce differences in mandibular structure. This thesis aims to understand the functional importance of these anatomical structures by examining the relationship between the thickness and volume of the masseter muscle and the mandibular bone and the morphological features of the mandible in detail. Material and Methods: For this reason, head and neck MR images of 46 adults (23 females and 23 males) aged 18-65 years were obtained from KTU Radiology Department and examined restrospectively. The images were taken from the PACS system in DICOM format and transferred to the ITK-SNAP program for measurement. Here, both masseter thickness and volume were calculated separately and parameters such as "condyle angle", "condyle area", "condyle area", "intergonial distance", "distance between condyles" of the mandibular bone were measured. Results: Statistical analyses revealed a positive, moderate and significant correlation between masseter thickness measurements and intergonial distance measurements (p<.05). A positive, moderate and significant relationship was obtained between masseter volume measurements and intergonial distance measurements (p<.05). In addition, a positive, low and significant relationship was obtained between the masseter volume measurements and condyle area measurements of the patients (p<.05). A significant difference was obtained between the condyle area, intergonial distance masseter thickness and volume measurements of the patients according to gender (p<.05). Conclusion: Based on our results, we observed that masseter muscle thickness and volume are correlated with intergonial distance, one of the mandibular development parameters.There is also a positive correlation between masseter muscle volume and condyle area measurements.In addition, the mean values of all parameters were higher in males than females.We think that this study will contribute to the literature by shedding light on the factors affecting mandibular bone development and by evaluating masseter muscle volume in addition to masseter muscle thickness. Key Words: Eye Dominance, Grey Matter, Handedness, Magnetic Resonance, Serebral Dominance, White Matter