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168 Fatigue testing and fractographic analysis of a NiTi rotary instrument C. Pirani, C. Prati, P.P. Cirulli, S. Chersoni, O. Ruggeri University of Bologna, Italy Objectives: To examine the topographic features of the surface of fractured NiTi instrument after cyclic fatigue failure. Materials and methods: Twelve EasyShape (Komet/Gebr. Brasseler, Lemgo, Germany) 25/.06 rotary files were subjected to rotational-bending test at 45 ◦ and 60 ◦ curvatures until fracture occurred. Time to fracture was recorded. Four representative samples were chosen and the fracture surface of the fragments was examined by SEM (EVO50 EP; Carl Zeiss NTS GmbH, Oberkochen, Germany) to identify the crack origin and the surface features. A SEM analysis was also conducted for details on two instruments in the “out-of-the-box” condition, to have comparison samples for the fractographic analysis. Results: The average (±SD) of the time and number of cycles for fatigue fracture to occur was respectively 141.4 ± 20.5 s and 707.8 ± 101.4 cycles for instruments rotated in the artificial canal with the curvature of 60 ◦ . In the curvature of 45 ◦ was 601.8 ± 28.8 s and 3011.6 ± 143.66 cycles. In all samples the crack initiation site was identified. A deeper analysis revealed the presence of a region occupied by microscopic parallel striations, and an area with signs of plastic deformation (presence of dimples). The presence of voids and inclusions was also found. Fig. 1 (left): SEM micrograph (5000×) of the cutting edge of a new TiN coated instrument. Presence of debris dental materials 26S (2010) e1–e84 e79 (black arrow) and metal strips (white arrow) was noticed. Fig. 2 (right): SEM micrograph (400×) of a fracture surface. The region of fatigue crack propagation (white arrow) and the region of dimpled fracture (black arrow) were identified. Conclusions: The results confirmed the angle of curvature and the presence of superficial defects as important predictors for instrument separation. doi:10.1016/j.dental.2010.08.176 169 Bioinspired remineralization of dentine by designed lightcuring calcium-silicate material C. Prati 1 , M.G. Gandolfi 1 , F. Siboni 1 , P. Taddei 1 , E. Dorigo De Stefano 2 1 University of Bologna, Bologna, Italy 2 University of Trieste, Trieste, Italy Objectives: Bioactive calcium-releasing composites able to remineralize dentine surface represent attractive preventive and therapeutic materials in restorative dentistry. The hypothesis of the study was that experimental restorative/composite materials containing tailored calcium-silicate particles are able to remineralize artificially demineralized dentine. Materials and methods: Calcium-aluminosilicate powder (wTC-Ba) consisting of tri- and dicalcium-silicate, tricalcium aluminate, calcium sulphate, barium sulphate, was mixed with an experimental resin (HTP-M) containing HEMA, TEGDMA and polyacrylic acid. Gradia Direct LoFlo (GC, Japan) and Vitrebond (3M ESPE, Germany) were tested as controls. Dentin disks (0.8 mm ± 0.2 mm thick and 5.0 mm ± 1.0 mm length) were prepared from human third molars following extraction by using a saw microtome. Dentin disks were demineralized by immersion in sterile 17% EDTA solution (Ogna, Italy) for 2 h, standing in vertical position using a PVC support to demineralize both the major surfaces. FTIR analysis was performed on each demineralized dentine to confirm the occurred demineralization. Each demineralized dentin disk was placed in close contact with a cement sample and stored in 20 mL of simulated body fluid (DPBS) at 37 ◦ C. After 7 days of soaking, all dentine disks were separated from the cement, washed with 5 mL of deionized water to remove the cement deposit, and analyzed by FTIR and ESEM/EDX. Results: The experimental composite released calcium (500 ppm at 3 h) and formed carbonated apatite (Ap) on its surface, and induced the in situ formation of a different carbonated apatite (Ap) on the surface of demineralized dentine. Control materials did not support apatite formation or dentine remineralization.
e80 dental materials 26S (2010) e1–e84 Conclusions: The released calcium was adsorbed on the dentine surface and enhances its mineralization in simulated body fluid. The study supports the concept that a calciumsilicate filled composite is a smart material able to induce apatite formation for remineralization of caries-like dentine lesions. These properties may extend the range clinical applications of composite materials. doi:10.1016/j.dental.2010.08.177 170 Effect of DLC film on C. albicans biofilm formation J.R.C. Queiroz 1 , S.F. Fissmer 2 , C.Y. Koga Ito 1 , A.C.R.D. Salvia 1 , M. Massi 2 , L. Nogueira Junior 1 1 Universidade Estadual Paulista, Brazil 2 Instituto Tecnológico de Aeronáutica, Brazil Objectives: Diamond-like carbon (DLC) films have been used with successfully for several biomedical applications (Grill. Diamond Relat Mater 2003; 12: 166–70), however little is known about the use in dentistry. The purpose of this study was to investigate the antifungal activity of a-C, a-C:H and a- C:H:Ag films (DLC) on Candida albicans biofilm formation onto acrylic resin and to describe the film features. Materials and methods: 60 disks (diameter 10 mm × 2.5 mm) of acrylic resin (LUCITONE, Dentsply) were obtained according to the manufacturer’s recommendation, polished at 1200 SiC paper and divided in 4 groups (n = 15): G1 without film, (G2) a:C, (G3) a:C-H, (G4) a:C-H with Ag nanoparticles. Different DLCs films were deposited on acrylic resin surface using plasma method (physical vapor deposition-PVD) with reactive magnetron sputtering technique. After �-ray irradiation, C. albicans (ATCC 18804) biofilms were formed by immersion into 2 ml Sabouraud dextrose broth inoculated with standardized fungal suspension. After 24 h of incubation, the number of colony-forming units (cfu) was counted and the values of cfu/cp were calculated. Data were analyzed using ANOVA and Tukey’s test (˛ = 0.05). Film deposition rate, RAMAN, RBS and AFM analyses was performed. Results: Groups 1 2 3 4 cfu (Candida albincans) 69.4 × 106 (a) 29.1 × 106 (b) 18.1 × 106 (b) 26.1 × 106 (b) Deposition rate (nm/min) – 2.0 ± 0.2 1.9 ± 0.3 2.3 ± 0.4 Letters in parentheses = homogeneous subsets (Tukey test level = 0.05). Chemical composition (%) C Ag H O N G2 film 75.5 – 8.5 4.2 11.7 G3 film 63.1 – 18.4 5.4 13.0 G4 film 67.6 9.6 9.0 3.0 10.8 The images from AFM illustrated the different topography patterns. Conclusions: All films decreased significantly C. albicans biofilm formation in relation to the control. No differences among the films were observed. doi:10.1016/j.dental.2010.08.178 171 Electrospun collagen/hyaluronic acid nanofibers improve osteoblastic differentiation onto titanium surfaces I. Foltran 1,2 , S. Mele 1 , N. Roveri 2 , L. Rimondini 1 1 University of Piemonte Orientale, Italy 2 University of Bologna, Italy Objectives: Electrospinning technique (ES) is an efficient processing method to manufacture nano-sized fibrous structures by electrostatic force for different applications. In biomaterial field, ES has been successfully utilized to prepare new drug delivery materials and tissue engineering scaffolds. In the present investigation collagen/hyaluronic acid nanofibers were used to coat the surface of titanium used for oral implant manufacturing with the aim to assess the potential improvement of cell responses on these materials. Materials and methods: The nanofibers were electrospun onto titanium disks. For the process of ES a suspension, 2.5% (w/w), of telopeptides-free type I collagen molecules dissolved
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