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: The purpose of the current study was to estimate the biocompatibility of endodontic sealers with different bases on L929 mouse fibroblasts permanent cell line using Multiscan EX Spectrophotometer. Materials and Methods: Endodontics sealers used in this study were GuttaFlow (Roeko) silicone based sealer, AH plus (De Tray-DENTSPLY) epoxy resin based, Apexit (Vivadent) calcium hydroxide based and Endorez (Ultradent) methacrylate based sealer. Sealer were tested trough time, freshly mixed 24 h, 48h and 7 days after setting. Biocompatibility was determinate on permanent cell lines L929 mouse fibroblasts trough cytotoxicity using MTT assay. Level of absorption was measured with multi scan EX spectrophotometer on length 420-600 nm. Results: Sealer based on calcium hydroxide Apexit Plus, GuttaFlow silicone based sealer and AH plus epoxy resin based sealer, have shown a low cytotoxicity through the all periods of time on culture of L292 mouse fibroblasts. Methacrylate based sealer, Endorez showed moderate cytotoxicity when freshly mixed and after 7 days. After 24 hours the visibility of the cells was 74,0% and after 48 hours 65,1%. which is slightly cytotoxic. Conclusions: According to results of this study there is a statistically significant difference among the groups p<0,05 for all the tested sealers. Apexit Plus, GuttaFlow and AH plus can be considered as biocompatibile. EndoREZ sealer which is based on methacrylate, after 7 days shows 50,1% of visible live cells which is considered as moderate cytotoxicity.

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.

Introduction: Impaction may be defined as the failure of complete eruption into a normal functional position of one tooth within normal time due to lack of space in the dental arch, caused by obstruction byanother tooth or development in an abnormal position. The mandibular third molar is the most frequently impacted tooth. The incidence varies from 9.5% to 68% in different populations.Methods: The study was conducted in Department of Oral Surgery, Faculty of Dentistry, University in Sarajevo. Study represents retrospective analysis of panoramic radiographs (orthopantomograms) of patientsreferred to Department of Oral Surgery from January 2010 to February 2013 with indication for surgical removal of impacted third molars.Results: Of the 2000 radiographs, 761 presented with at least one impacted third molar (38%). A total of 1034 impacted mandibular third molars were present (51.7%). The most common age group was thirddecade (61.2%). Signifi cant statistical difference in incidence of third molar impaction was found between females and males (p<0.05), but there was no statistical difference in incidence in urban and suburbanpopulation (p=0.374). Vertical angulation was the most common pattern of impaction (65%). Frequency of third molars erupted into their normal position (class IA) was 42%. Impacted mandibular molars wereassociated with periodontal pockets in 134 (6.5%) cases and with dentigerous cysts in 5 cases (0.2%).Conclusion: The present study provides useful data regarding the clinical status of third molars in population of Bosnia and Herzegovina.

Adresa za dopisivanje Samra Korać DMD, MSc Sveučilište u Sarajevu Stomatološki fakultet Zavod za restorativnu stomatologiju i endodonciju Bolnička 4 a 1000 Sarajevo, Bosna i Hercegovina samragk@gmail.com Sažetak Svrha istraživanja bila je izmjeriti i usporediti unutarnju stabilnost boje triju svjetlosnopolimerizirajućih materijala i jednoga kemijski stvrdnjavajućeg nakon njihova ubrzanog starenja. Materijali i metode: Testovi za stabilnost boja obavljeni su na svjetlosnopolimerizirajućim kompozitima – nanopunjenju Filtek Supreme XT (3M ESPE), nanohibridu Tetric Evo Ceram (Ivoclar Vivadent) i mikrohibridu Herculite XRV (Kerr) te na samopolimerizirajućem kompozitu Bisfil II (Bisco). Svi uzorci bili su uronjeni u destiliranu vodu (37°C) i držani u tamnoj posudi 24 sata. Nakon toga podijeljeni su u tri skupine. Postupak ubrzanog starenja proveden je prema dvama protokolima – u vodenoj kupelji na 60°C i prema ISO-u 7491. Uzorci iz kontrolne skupine držani su u destiliranoj vodi 30 dana na temperaturi od 37°C. Razlike u boji – ∆E, računale su se iz koordinata CIE L*a*b* izmjerenih spektrofotometrom nasuprot bijeloj pozadini prije postupka starenja uzoraka i poslije njega. Razina osjetljivosti boje postavljena je na 1, a prihvatljivi šum na 3,5. Statistička analiza obavljena je uparenim t-testom i ANOVA-om (p≤0,05). Rezultati: Svi ispitani materijali pokazali su klinički neprihvatljive promjene boje nakon ubrzanog starenja u vodenoj kupelji, a fotostarenjem nastala je vidljiva promjena boje kod svih svjetlosnopolimerizirajućih kompozita. Nanokompozitni materijali značajno su promijenili boju i u kontrolnoj skupini. Zaključak: Unutarnja stabilnost boje testiranih materijala ovisi o uvjetima starenja i vrsti dentalnog kompozita. Kemijski stvrdnjavajući kompoziti pokazali su tijekom fotostarenja bolju stabilnost. Ključne riječi kompozitne smole; starenje; materijali, testiranje; boja 1 Katedra za restorativnu stomatologiju i endodonciju Stomatološkog fakulteta Sveučilišta u Sarajevu Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, University of Sarajevo 2 Odjel za ispitivanje dentalnih materijala Akademskog centra za stomatologiju, Amsterdam (ACTA), Nizozemska Dental Materials Science Department, Academic Centre for Dentistry Amsterdam (ACTA) 3 Katedra za pretkliničku stomatologiju Stomatološkog fakulteta Sveučilišta u Sarajevu Departmet of Preclinical Dentistry, Faculty of Dentistry, University of Sarajevo