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0.625 mm. A 3D solid model was prepared and exported into a 3D-FE program (Solid Works Office Premium, 2009). Additionally eight models of Class I and Class II cavity preparations (classical and minimal-invasive types) and restorations were simulated by a proper choice of mesh volumes. A validation procedure of the FE model was executed based on comparison of theoretical calculations and experimental data according to literature. The polymerization shrinkage was modelled using temperature dependent expansion. The adhesive layer was produced in the FE program with a thickness of 30 �m. FE simulations of thermal loading (5 ◦ C and 55 ◦ C) were carried out for each combination of cavity geometry, boundary conditions and material properties. Results: Thermal stress distributions of tooth-adhesivecomposite interfaces of restored premolars have been observed in a series of experiments and depended on the configuration and size of the restoration. In all cavity types, enamel-adhesive interfaces and cavity angles were more stressed than composite-adhesive ones. The low temperatures caused higher stress in the tooth-adhesive interface than high temperatures in the mouth. Conclusions: The low temperatures have a major impact on marginal integrity of composite restorations in posterior teeth and increase the unfavourable effects of polymerization shrinkage. doi:10.1016/j.dental.2010.08.078 71 SS-OCT as alternative to micro-CT for composites internal adaptation evaluation J.R. Mayoral 1 , A. Sadr 2 , Y. Shimada 2 , E. Cho 2 , Y. Sumi 3 ,I. Krejci 3 , L. Giner 1 , M. Roig 1 , J. Tagami 2 1 Universitat Internacional de Catalunya, Spain 2 Tokyo Medical & Dental University, Japan, National Center for Geriatrics and Gerontology, Japan 3 University of Geneva, Switzerland Objectives: The aim of this study was to evaluate the internal adaptation at dentin cavity floor of resin composites using swept source optical coherence tomography (SS-OCT) and Xray micro-tomography. Materials and methods: Eight extracted human molars were horizontally sectioned at a buccal-lingual direction occlusally bellow dentine–enamel junction using a low speed saw (Isomet, Buehler LTD, USA). From these specimens dentin discs (Ø: 6 mm; n =4× 2) with cavities (Ø: 3 mm; h: 1 mm) where prepared, randomly divided in two experimental groups and single-layer bulk filled with micro-hybrid composite Clearfil AP-X/APX, and nano-filled Clearfil Majesty Posterior/MP without any conditioning, priming or bonding treatment. The dental materials 26S (2010) e1–e84 e33 composites were photopolymerized for 40 s at 750 mW/cm 2 using an LED curing unit (Dentaport, Morita, Japan). All specimens were cross-sectional imaged using an SS-OCT unit (Santec, Japan) with 1319 nm laser center wavelength. Forty-eight B-scan image slices per-group were obtained and processed with Image J analysis software (NIH, USA) to quantify interfacial gap area fraction resulting from polymerization shrinkage, dimensional contraction and structural voids at dentin cavity floor. Thereafter all samples were imaged by high resolution micro-XCT (Shimadzu, Japan) and were recorded using the 2D and 3D software. Identification of the limits between composites and dentinal micro-voids were made. Confocal laser scanning microscope (CLSM) analysis at 500× and 2500× magnification was made to confirm SS-OCT findings. Data were statistically analyzed by two-way ANOVA to determine interfacial gap differences between groups. Results: Image analysis obtained from SS-OCT revealed significant differences of interfacial gaps between groups (P < 0.05). The optical contrast between the material and air helped in detection of interfacial gaps. CLSM analysis confirmed that SS-OCT was capable of detecting interfacial gaps and structural voids on submicron-scale. MicroCT images were not able to assess direct detection of interfacial gap at composite-dentin cavity floor. Conclusions: SS-OCT can be used to provide nondestructive assessment between restoratives materials and internal tooth interfaces for gap detection at the bottom of resin composites restorations. Micro-CT was not capable to detect direct gap interface at dentin cavity floor. doi:10.1016/j.dental.2010.08.079 72 Curing depth of restorative composites achieved with QTH and LED units W.G. Miranda Jr, S.W. Kim, B. Pick, A.O. Lopes, F.A. Maeda University of São Paulo, Brazil Objectives: The aim of this study was to evaluate the curing ability of different light units in polymerizing popular restorative composites. Materials and methods: Five blocks (2 mm × 2mm× 5 mm) were built using four commercial composites (A2, Vita Shade). Composites were light-activated for 40 s with four curing units and kept dry for 24 h at 37 ◦ C in the dark. The Knoop microhardness (50 g/15 s) was assessed at four depths (HMV-2T, Shimadzu, Kyoto, Japan). Results were analyzed by three-way ANOVA/Tukey test (˛ = 0.05). Results: The light unit × composite interaction was statistically significant (p < 0.001).
e34 dental materials 26S (2010) e1–e84 Composites Depth LED QTH Translux Power Blue a FLASHlite 1401 b Ultra-Lume Led 5 c XL 2500 d Z-250 e 0.2 mm 81(0.8)Aa 62(9.7)ABb 67.8(3.6)Aab 68.2(5.9)Aab 1 mm 78.4(2.5)Aa 68.8(6.2)Aa 66(1.9)Aa 68.2(7.1)Aa 2 mm 69.6(4)Aa 63.6(5.8)ABa 63.8(2.9)Aa 62.4(7.5)Aa 4 mm 52(0.6)Ba 54.2(5.8)Ba 48.6(9.7)Ba 42.8(12.3)Ba TPH f 0.2 mm 49.2(3)Ab 55.2(5)Aa 51.4(10.8)ABb 51(6.9)Ab 1 mm 47(3.3)Aa 52(5.1)Aa 53.4(1.8)Aa 46.8(7.6)Aa 2 mm 41.8(1.6)ABa 52(2.4)Aa 48(4)ABa 43(4.4)ABa 4 mm 28.1(1.2)Bb 36(3.9)Bab 39.2(4.1)Ba 29.8(3.9)Bb Tetric g 0.2 mm 42.4(5.7)Aa 41.2(3.8)Aa 49.4(3.1)Aa 40(2,3)Aa 1 mm 41.2(5.8)Aa 38.2(6.1)Aa 49.8(8.3)Aa 38.8(4.5)Aa 2 mm 35.2(4.4)Aa 39.2(6.1)Aa 43.4(6.7)ABa 33.2(5.1)Aa 4 mm 18.9(3)Bc 22.6(5.1)Bb 30.6(5.6)Ba 17.6(2.7)Ba Charisma h 0.2 mm 29.4(4.8)Ab 35.8(5.4)Aab 46.6(11.3)Aa 34.2(4.4)Aab 1 mm 27.8(3.5)Aa 36.8(3.9)Aa 41.6(3.6)ABa 31.6(6.2)Aa 2 mm 22.4(4.4)ABa 30.6(4.9)ABa 35.6(2.1)ABa 27.6(4.5)ABa 4 mm 9.5(1.1)Bb 22.8(2.9)Bab 31.4(0.9)Ba 13.8(6.1)Bb For each composite and light unit, capital letters compare KHN among depths. Within the same line, values followed by the same letters are statistically similar (p > 0.05). a Translux Power Blue, Heraeus. b FLASHlite 1401, Discus. c Ultra-Lume Led 5, Ultradent. d XL 2500, 3M. e Z-250, 3M. f TPH, Dentsply. g Tetric, Ivoclair/Vivadent. h Charisma, Heraeus. Conclusions: For all composites, Ultra-Lume 5 resulted in higher KHN at 4 mm. Also, no differences in KHN were found up to 2 mm depth for each composite/light unit association. doi:10.1016/j.dental.2010.08.080 73 Influence of fiber post on degree of conversion of a luting cement C.O. Navarra 1 , C. Goracci 2 , G. Corciolani 2 , A. Vichi 2 ,L. Breschi 1 , M. Cadenaro 1 , M. Ferrari 2 1 University of Trieste, Italy 2 University of Siena, Italy Objectives: to assess the degree of conversion achieved at different levels of a simulated dowel space by a dualcure resin cement in combination with different fiber posts. Materials and methods: Similarly sized posts of different shape and composition were selected: GC Fiber Post (GC, GC); FibreKleer Serrated Post (Jeneric/Pentron, FK); DT Light SL (VDW, SL); RelyX Fiber Post (3 M ESPE, RX); Reforpost (Angelus, RE); DT Light Post Illusion (RTD, LPI); FRC Postec Plus (Ivoclar-Vivadent, FP); Radix (Dentsply, RA); Snowpost (Abrasive Technology, S); Dentin Post X (Komet, DP); Macrolock Illusion (RTD, MI); Composipost (RTD, C). A metal guide was used to position the post centered within a cylindrical metal mould simulating the dowel space and filled with Variolink II (Ivoclar-Vivadent). The cement was light-cured (Trilight, 3M ESPE), placing the light tip on the post coronal end for 20 s with the metal guide in position and for additional 40 s after removing the metal guide. After 24 h, degree of conversion of the cement was assessed through Raman analysis at the coronal (C), middle (M), and apical (A) third of the simulated dowel space. Degree of conversion data were statistically analyzed (Two-Way ANOVA, Tukey test, p < 0.05).
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