Objective:The present study aims to investigate the influence of presence and shape of cervical lesions on biomechanical behavior of mandibular first premolar, subjected to two types of occlusal loading using three-dimensional (3D) finite element method (FEM).Materials and Methods:3D models of the mandibular premolar are created from a micro computed tomography X-ray image: model of sound mandibular premolar, model with the wedge-shaped cervical lesion (V lesion), and model with saucer-shaped cervical lesion (U lesion). By FEM, straining of the tooth tissues under functional and nonfunctional occlusal loading of 200 (N) is analyzed. For the analysis, the following software was used: CTAn program 1.10 and ANSYS Workbench (version 14.0). The results are presented in von Mises stress.Results:Values of calculated stress in all tooth structures are higher under nonfunctional occlusal loading, while the functional loading is resulted in homogeneous stress distribution. Nonfunctional load in the cervical area of sound tooth model as well as in the sub-superficial layer of the enamel resulted with a significant stress (over 50 [MPa]). The highest stress concentration on models with lesions is noticed on the apex of the V-shaped lesion, while stress in saucer U lesion is significantly lower and distributed over wider area.Conclusion:The type of the occlusal teeth loading has the biggest influence on cervical stress intensity. Geometric shape of the existing lesion is very important in the distribution of internal stress. Compared to the U-shaped lesions, V-shaped lesions show significantly higher stress concentrations under load. Exposure to stress would lead to its progression.

Introduction:An abfraction lesion is a type of a non-carious cervical lesion (NCCL) that represents a sharp defect on the cervical part of tooth, caused by occlusal biomechanical forces. The largest prevalence of the NCCL is found on the mandibular first premolar. The goal of the study is, by means of a numerical method – the finite element method (FEM), in an appropriate computer program, conduct a stress analysis of the mandibular premolar under various static loads, with a special reference to the biomechanics of cervical tooth region.Material and methods:A three-dimensional model of the mandibular premolar is gained from a µCT x-ray image. By using the FEM, straining of the enamel, dentin, peridontal ligament and alveolar bone under axial and paraxial forces of 200 [N] is analyzed. The following software were used in the analysis: CT images processing–CTAn program and FEM analysis–AnsysWorkbench 14.0.Results:According to results obtained through the FEM method, the calculated stress is higher with eccentric forces within all tested tooth tissue. The occlusal load leads to a significant stress in the cervical tooth area, especially in the sub-superficial layer of the enamel (over 50 MPa). The measured stress in the peridontal ligament is approximately three times higher under paraxial load with regard to the axial load, while stress calculated in the alveolar bone under paraxial load is almost ten times higher with regard to the axial load. The highest stress values were calculated in the cervical part of the alveoli, where bone resorption is most commonly seen.Conclusion:Action of occlusal forces, especially paraxial ones, leads to significant stress in the cervical part of tooth. The stress values in the cervical sub-superficial enamel layer are almost 5 times higher in relation to the superficial enamel, which additionally confirms complexity of biomechanical processes in the creation of abfraction lesions.

IntroductionIn Bosnia and Herzegovina, apart from domicile population, there is a certain number of displaced persons. Most of them are situated in the area of Canton Tuzla. These persons are generally at risk of and being watched for various diseases, including the disease of the orofacial area. Dental fear and anxiety (DFA) is also inevitably present in displaced persons, with higher prevalence compared with general population. Therefore, the aim was to evaluate the DFA presence and the most common reasons for dental fear and anxiety in displaced persons in our country.Patients and methods310 interviewed persons were included in this study, aged 35 to 44 years, from several cities of Canton Tuzla. They were divided in the group of displaced persons (n=153), and the group of domicile inhabitants (n=157). The study participants were interviewed about the DFA presence, as well as about the risk factors for DFA, which was subsequently evaluated by the Modified Corah's Dental Anxiety Scale.ResultsA high prevalence of DFA presence was determined in the total sample (38.71%), and particularly in the displaced persons group (57.52%). The results showed that displaced persons rarely visited dentists, mainly when it was necessary (odontalgia), with stronger reactions to factors that could cause DFA appearance.ConclusionDisplaced persons are regarded as one of the highest risk groups for prevalence of DFA. This could be mainly due to poor oral health status, rare dental office visits and the urgent need for dental treatment, which could lead to vicious circle of mutual strengthening between bad oral health and DFA appearance.

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