Aim: The aim of this study was to compare time of preparation and canal aberrations in a simulated root canals after using three different rotary systems: Endostar E5, Endostar E3 and T One File Gold. Materials and Methods: A total of 90 endodontic training blocks were used in this study and divided into three groups consisting of 30 each (n = 30). Blocks processing was performed by thirty dentists without any prior experience in rotary instrumentation techniques. In the first group blocks were prepared using Endostar E5, in second one with Endostar E3 and in third one with T One File Gold system. The preparation time was measured. The postoperative image of each block was taken by stereomicroscope and canal aberrations (ledge and instrument fracture) was recorded. Statistical analysis was done by SPSS software. Results: Instrumentation with T One File Gold system is significantly faster compared to instrumentation with Endostar E5 and Endostar E3 systems (p <0.05). There are no statistically significant differences in the type and number of procedural errors between Endostar E5, Endostar E3 and T One File Gold systems when the operators have no previous experience in rotary instrumentation techniques. Conclusion: Under the conditions of this study, the incidence of examined canal aberrations were similar for all tested systems. The preparation time was significantly shorter with single file system.

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.

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