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Conclusions: ES achieved significantly lower shear bond strength to enamel than the other splinting materials and the resin composite. No statistically significant differences emerged in the distribution of failure modes among the groups. QS, TX, CNS, and ES significantly increased flexural strength of the resin composite. QS yielded significantly higher flexural strength than THM and CNN. doi:10.1016/j.dental.2010.08.051 44 Effect of resin shade and LED light intensity on microhardness K. Tolidis, P. Gerasimou, C. Boutsiouki Aristotle University of Thessaloniki, Greece Objectives: The clinical performance of light cured dental composites is greatly influenced by light intensity of the light curing unit and the shade of the resin composite used, affecting microhardness values. The purpose of the present study was to control multiple combinations of LED curing devices with different light intensities and various composite resin shades. Materials and methods: A nanohybrid resin composite in shades A3, B2 and C2 was used along with higher and lower light intensity modes from LED curing devices (Radii, Elipar S10, Valo in standard and plasma mode). Four groups were formed for each shade and five specimens were made for each group, which were 4 mm thick. Specimen were evaluated with Vickers microhardness (100 gr for 15 s) both at the top and bottom surface to assess microhardness values. Data were analyzed with ANOVA and Tukey–Kramer test. Results: No significant differences were found for A3 shade at top surface and at the bottom surface for most of the curing modes used. Shade B2 on top, exhibited no significant difference in comparison between Elipar S10 and Valo standard mode (p > 0.05) and within Valo modes (p > 0.05). Shade B2 at bottom surface exhibited extremely significant difference for Radii and Elipar S10 (p < 0.001), Elipar S10 and Valo standard mode (p < 0.001). As for shade C2 at the top surface, it exhibited significant differences (p < 0.05) in comparison between Radii and Elipar S10 and for every curing unit at the bottom except for Valo modes (p > 0.05). Conclusions: Top surfaces exhibited greater microhardness values compared to bottom as expected. A3 exhibited acceptable microhardness values with all the LED curing devices. Higher power LEDs generally result in lower microhardness values when curing shade C2, but there is no difference between Valo modes, which represent the lowest and high- dental materials 26S (2010) e1–e84 e21 est light intensity of this experiment. Elipar S10, with an average light intensity, seems to polymerize efficiently all shades. doi:10.1016/j.dental.2010.08.052 45 Temperature increase during composites polymerisation using two LED curing lights E. Armellin 1 , G. Bovesecchi 1 , P. Coppa 1 , G. Pasquantonio 1 ,L. Breschi 2 , L. Cerroni 1 1 University of Rome Tor Vergata, Italy 2 University of Trieste, Italy Light intensity Pulp chambre Occlusal surface M = 3 mm below occlusal surface VALO Starlight PRO VALO Starlight PRO Objectives: The aim of curing light technology has been the development of lights that would result in faster curing of resin composites and less heat generation (Aravamudhan et al., Dent Mater 2006). The purpose of this in vitro study was to evaluate thermal changes on the tooth structures during the exposure of two different light emitting diode-curing units (LED). Materials and methods: Caries-free human first molar were randomly selected and pulp residues were removed after root resection. Four thermocouples were positioned according to a Hannig and Bott modified method (Dent Mater, 1999). The experimental set-up was composed by Keithley data acquisition system (model 2700 with 7700 card) and by a set of type J-thermocouples with cold junction in ice. The thermocouples were hand made with a thin-coated wire (0.5 mm in diameter) fitted in the tooth capable of a fast time-response. The precision of the thermocouples was ±0.1 ◦ C. Two LED lamps were tested: A: VALO (ultradent), tested at light intensity of 1000 mW/cm 2 (for 20 s) or 4500 mW/cm 2 (for 3 s); B: Starlight PRO (Mectron) tested at light intensity of 1000 mW/cm 2 (for 20 s). Maximum temperature rises among the two LED light tested were analyzed using one-way analysis of variance (ANOVA). Results: When composite was light cured the temperature values increased rapidly reacting the plateau in 0.7–1 s. Thermal flux generated by monomer conversion was added to light curing heat. Means and standard deviations of maximum temperature increase (expressed in ◦ C) measured at different site of tooth during composite polymerization with VALO or Starlight PRO are reported in the table. VALO Starlight PRO Composite VALO Starlight PRO 1000 mW/cm2 1.58 ± 0.12a,d 1.08 ± 0,13a 7.34 ± 4.40 3.92 ± 1.73 1,99 ± 0.22b,e 1.26 ± 0.11b 20.56 ± 0.48c 12.77 ± 3.07c 4500 mW/cm2 0.87 ± 0.16d – 5.07 ± 0.05 – 1.08 ± 0.08 e – 21.76 ± 4.58 – Different superscript letters indicate different groups: a, b, d, e (p < 0.005); c (p < 0.01). Conclusions: Differences in temperature raises during composite polymerization were found between the two LED light tested, regardless the selected sites. Further studies are needed to clarify in vivo the clinical relevance of temperature increase during light-activated polymerization. doi:10.1016/j.dental.2010.08.053
e22 dental materials 26S (2010) e1–e84 46 Is pre-heated microhybrid composite effective as a inlay luting agent? F. Cerutti 1 , M. Gagliani 2 , A. Cerutti 1 1 University of Brescia, Italy 2 University of Milan, Italy Objectives: The long-term outcomes of composite inlays are influenced by adhesive luting; dual-curing and light curing materials are available for this procedure, however light contribution still plays a key-role when luting thick inlays. To obtain a high degree of conversion (DC), good handling and marginal quality, pre-heating of micro-hybrid light-curing composites was introduced. Aim of this study was to evaluate the DC of a pre-heated composite compared to a standard dual-curing luting material, both cured below inlays by means of a traditional Halogen curing lamp (QTH) and two LED curing devices. The null hypothesis was to find no difference among the materials DC, independently from the curing source employed, the inlay thickness and the power/time combinations of light-curing units. Materials and methods: 90 inlays 1 of increasing thickness (2 mm × 3mm× 4 mm) were prepared in a custom template, then randomly split into 3 groups (n = 5) and luted on glass slides with two different composites: a dualcure luting cement 2 and a 54 ◦ C pre-heated microhybrid composite. 3 Light-curing was performed with three LCUs 4,5,6 providing a constant energy density (48J). DC was assessed with a micro-Raman Dilor-HR-Labram spectrometer, then ANOVA and post hoc Student–Neumann test were performed (˛ = 0.05). Results: Mean DC and SD are shown. QTH 800 mW/cm2 for 60 s Venus Variolink II LED 800 mW/cm 2 for 60 s Venus Variolink II LED 1200 mW/cm2 for 40 s Venus Variolink II 2 mm 69.6 (2.12) 73.6(5.7) 69.6 (2.12) 82.3 (3.38) 71.8 (5.55) 85.1 (3.57) 3 mm 66.8 (2.56) 65.9 (11.7) 64.8 (4.99) 78 (2.74) 70.4 (4.05) 80.9 (1.74) 4 mm 59.4 (3.66) 63.9 (6.54) 59 (6.09) 71.2 (5.11) 66.6 (2.9) 76.5 (2.11) As expected, DC decreases as the inlay thickness increases. At the same power LED performed better than QTH in dualcuring cement; increased power got better results both in composite and in dual-cure luting cement. Conclusions: Pre-heated micro-hybrid composite could be reliably converted under composite inlays of increasing thickness and could be effective for composite inlays luting procedure. doi:10.1016/j.dental.2010.08.054 1 Signum, Heraeus (shade A2). 2 Variolink II, Ivoclar-Vivadent. 3 Venus, Heraeus. 4 SwissMaster Light, EMS. 5 Bluephase C8, Ivoclar-Vivadent. 6 Bluephase G2, Ivoclar-Vivadent. Table 1 Tested flowable composites Low compliance (MPa) High compliance (MPa) Degree of conversion (%DC) Filtek Supreme XT Flowable Restorative 3.39 ± 0.39d 1.58 ± 0.26c 64 ± 3AB Venus Diamond flow 1.17 ± 0.35bc 0.58 ± 0.20a 69 ± 2B Revolution Formula 2 1.03 ± 0.23b 0.61 ± 0.08a 64 ± 3AB Means followed by same superscript (small letter for stress values, capital letter for DC values) indicate no statistical difference at the 95% confidence level (p < 0.05). 47 Evaluation of polymerization stress correlated with the extent of polymerization of flowable composites B. Codan, L. Breschi, E. de Stefano Dorigo, M. Cadenaro University of Trieste, Italy Objectives: The aim of this study was to measure the contraction stress and degree of conversion (DC) of three flowable resin composites using a halogen curing-light. Stress values were analyzed using two measurement systems of varying compliance and correlated with the DC of each composite. Materials and methods: Materials tested were: Venus Diamond flow (Heraeus Kulzer), Revolution Formula 2 (Kerr Corporation, Orange, CA, USA); Filtek Supreme XT Flowable Restorative (3M ESPE, ST Paul, MN, USA). Composites were polymerized with a halogen curing unit (Elipar 2500, 3M ESPE, 500 mW/cm2 ) for 40 s. Contraction stress was measured using a universal testing machine with an extensometer as a feedback system and a stress-analyzer with no feedback. The contraction force (N) generated during polymerization was continuously recorded for 300 s after photo-initiation. Contraction stress (MPa) was calculated at 300 s. Micro-Raman was used to calculate the DC of the tested materials. Data were statistically analyzed by two-way ANOVA and Tukey’s post hoc test (˛ = 0.05). Results: Stress values scored as follows: Venus Diamond flow = Revolution Formula 2 < X-flow (Table 1; p < 0.05), with both measuring systems. The universal testing machine gave higher contraction stress than the stress-analyzer for each flowable (p < 0.05). Venus diamond flow showed the highest DC among the tested materials, however no correlation between DC and stress values was observed. Conclusions: Despite a high DC, the flowable composite Venus diamond flow showed the lowest stress value irrespective from the measurement system. Further investigations are needed to clarify if the use of low-shrinkage nano-hybrid flowable can be clinically effective in the long lasting of the restoration. doi:10.1016/j.dental.2010.08.055
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