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.

Temporomandibular disorders (TMD) are among the most challenging diseases of modern populations in diagnostic, therapeutic and prognostic terms. Diverse symptomatology requires teamwork and a multidisciplinary approach to this problem, therefore many researchers and clinicians in dentistry, otolaryngology, orthopaedics, neurology, radiology, rheumatology, and other areas deal with this disorder. Temporomandibular disorders is the common name for a number of pathological conditions that can have similar signs and symptoms, which lead to an imbalance of the normal functions of the stomatognathic system (1). Many epidemiological studies have examined the incidence of temporomandibular disorders in certain populations. It is now known that 60-70% of the population has at least one sign of temporomandibular disorder and that the ratio of temporomandibular disorders prevalence between women and men is Uvod

Adresa za dopisivanje Alma Kamber-Ćesir Sveučilište u Sarajevu Stomatološki fakultet Zavod za protetiku Bolnička 4a, Sarajevo, B&H almakamber@yahoo.com Sažetak Svrha istraživanja bila je odrediti utjecaj dentalnog statusa, dobi i spola na mentalni (MI) i mandibularni kortikalni indeks (MCI). Oba su određena na temelju 120 ortopantomograma. Rezultati: Srednja vrijednost indeksa MI bila je najviša kod pacijenata s potpunom denticijom, niža kod onih s djelomičnom ozubljenošću (Kennedyjeva klasa I), a najniža kod potpuno bezubih. Post-hoc testovi pokazali su statistički značajnu razliku za indeks MI na objema stranama između Kennedyjeve klase I i potpuno ozubljenih pacijenata (p≤0 ,001) te između potpuno ozubljenih i bezubih pacijenata (p≤0,001), ali ne i između Kennedyjeve klase I i potpuno bezubih pacijenata (p=0,470). Potpuno ozubljeni pacijenti ujedno su bili i najmlađa skupina pacijenata. Pacijentice su imale mnogo niže vrijednosti indeksa od pacijenata. Chi-square test pokazao je statistički značajnu razliku za indeks MCI između skupina pacijenata različitog dentalnog statusa, ali ne i između onih grupiranih prema spolu. Zaključak: Dentalni status i godine mogu utjecati na MI i MCI. Ključne riječi DMF indeks; zdravstveni status, pokazatelji; zubne proteze, djelomične, mobilne Zavod za stomatološku protetiku, Stomatološki fakultet Sveučilišta u Sarajevu Department of Prosthodontics, School of Dentistry University of Sarajevo

Introduction Temporomandibular dysfunction (TMD) denotes diseases of the muscles and the mandibular joint, muscular and skeletal diseases, and frequently also parts of systemic diseases of a generalized fibromy-algia, or a form of rheumatoid arthritis. In addition, fear, tension and stressful situations contribute to the overall condition of the masticatory system. (1) Some authors believe that TMD includes pathological diseases primarily affecting the function of muscles and the mandibular muscle, with a possible alteration to the tooth surface. (2) After a cause has crossed the level of individual physiological tolerance of the masticatory system, the system itself starts to respond with certain signs of change. Changes usually happen on the temporomandibular joints (TMJ), supportive tooth structures, and the teeth themselves. (3) The most frequent symptoms of TMD are found in the area of the temporomandibular joint, a sensation of fatigue in the jaw area, a sensation of stiffness of the jaw upon waking up or when opening the mouth, luxation or locking of the mandible when opening the mouth, pain when opening the mouth, and pain in the region of the temporomandibular joint or in the area of the masticatory muscles (cheeks). The most frequent signs of TMD include restricted mandibular movement , lower TMJ function, painful mandibular movement , muscle pain, and pain in the TMJ. (4) TMD causes are complex and multi-factori-al. Numerous factors may lead to TMD. The influence of psychosocial stressors, parafunctions and other psychological and behavioral processes onT-MD pain has been examined in a number of studies. For example, war-related stress has been linked to TMD (5), and stressors as mild as performing mental arithmetic and solving five-letter anagrams can also increase masticatory muscle activity thought to be associated with TMD. (6, 7) Similar relationships between stress and TMD have been reported in children, adolescents and adults. (8, 9, 10) The American Psychiatric Association (11) defines post-traumatic stress disorder (PTSD) as a form of pathological response to stress, in which the patient, through intrusive thoughts and dreams, regularly experiences the trauma suffered, and is consequently placed in a state of permanent increased tension. As a result of increased motor activity and the neu-rotransmitter disruptions which accompany PTSD, particularly with regard to noradrenalin, serotonin, endogenic opiates, and the hypothalamic-pituitary-adrenal axis (12, 13, 14), marked manifestations of symptoms and signs of TMD can be expected. (5)