Thermo-mechanical degradation of composite restoration photoactivated by modulated methods-a SEM study of marginal and internal gap formation

Objective. To evaluate the influence of thermal-mechanical degradation on superficial and internal gap formation of composite restorations photoactivated using modulated methods. Materials and methods. An experimental composite was prepared using a resin matrix containing 65wt% Bis-GMA and 35wt% TEGDMA. Camphorquinone (0.5wt%) and dimethylaminoethyl-methacrylate (0.5wt%) were dissolved in the resin as a photo-initiator system and 65wt.% silanized glass fillers were added to the matrix. Ground buccal surfaces of bovine lower incisors were used to make 160 preparations (3 mm x 3 mm x 2 mm in depth). An adhesive system (Adper Single Bond 2) was applied and the specimens were assigned into 16 groups (n = 10), according to the photoactivation method [high intensity (HI), low intensity (LI), soft-start (SS) and pulse-delay (PD)] and the degradation protocol [(control/no degradation; thermal cycling (TC); mechanical loading (ML); thermo-mechanical loading (TC+ML)]. Marginal and internal interfaces of bonded restorations were replicated in epoxy resin and analyzed by SEM. Gaps were expressed as a percentage of the total length of the margins. Data were submitted to 2-way ANOVA and Tukey's test (alpha = 0.05). Results. For the control group no significance was noted among the photoactivation methods. TC had no effect in gap formation. ML and TC+ML increased the incidence of superficial gaps for both HI and SS groups as well as increased the internal gaps for all groups. Conclusion. Although photoactivation methods do not influence gap formation at first, composite restoration photoactivated by low intensity or modulated methods showed improved resistance to thermo-mechanical degradation. Mechanical loading is determinant for interfacial degradation of composite restorations, while thermal cycling has no effect on gap formation.7151341134

Effect of Camphorquinone Concentration in Physical-Mechanical Properties of Experimental Flowable Resin Composites

The aim of this study was to evaluate the effect of camphorquinone concentration in physical-mechanical properties of experimental flowable composites in order to find the concentration that results in maximum conversion, balanced mechanical strength, and minimum shrinkage stress. Model composites based on BISGMA/TEGDMA with 70% wt filler loading were prepared containing different concentrations of camphorquinone (CQ) on resin matrix (0.25%, 0.50%, 1%, 1.50%, and 2% by weight). Degree of conversion was determined by FTIR. Surface hardness was assessed before and after 24 h ethanol storage and softening rate was determined. Depth of cure was determined by Knoop hardness evaluation at different depths. Color was assessed by reflectance spectrophotometer, employing the CIE-Lab system. Flexural strength and elastic modulus were determined by a three-point bending test. Shrinkage stress was determined in a Universal Testing Machine in a high compliance system. Data were submitted to ANOVA and Tukey's test (α = 0.05). The increase in CQ concentration caused a significant increase on flexural strength and luminosity of composites. Surface hardness was not affected by the concentration of CQ. Composite containing 0.25% wt CQ showed lower elastic modulus and shrinkage stress when compared to others. Depth of cure was 3 mm for composite containing 1% CQ and 2 mm for the other tested composites. Degree of conversion was inversely correlated with softening rate and directly correlated with elastic modulus and shrinkage stress. In conclusion, CQ concentration affects polymerization characteristics and mechanical strength of composites. The concentration of CQ in flowable composite for optimized polymerization and properties was 1% wt of the resin matrix, which allows adequate balance among degree of conversion, depth of cure, mechanical properties, and color characteristics of these materials.Peer Reviewe

Clinical performance of a self-etching adhesive at 18 months

Purpose: To test the null hypothesis that beveling and/or etching enamel would not affect the 18-month clinical performance of the self-etching adhesive Clearfil SE Bond (CSEB) in noncarious cervical lesions (NCCL). Methods: With Institutional Review Board approval, 34 patients were enrolled in this study. A total of 120 NCCL was selected and assigned to four groups: (1) CSEB was applied without any cavity preparation; (2) CSEB was applied after beveling enamel; (3) CSEB was applied after etching enamel for 15 seconds with 35% phosphoric acid; (4) CSEB was applied after beveling and etching enamel. A microfilled composite resin was used for all restorations. Resuts: At 6 months after initial placement, 120 restorations (a 100% recall rate) were evaluated. At 18 months, 87 restorations (a 72.5% recall rate) were available for evaluation. A survival rate of 100% was measured for all groups at both 6 and 18 months. Sensitivity to air decreased significantly only for Group 3 (no bevel+acid etch) from baseline to 18 months without statistical changes from 6 months to 18 months. None of the other parameters resulted in significant differences for any of the four groups. However, when data were pooled, both the overall marginal discoloration and the overall marginal adaptation were significantly worse at 18 months than at baseline, while sensitivity to air decreased significantly from baseline to 18 months. The 18-month survival rate of the self-etching adhesive Clearfil SE Bond was not improved by enamel bevel or by enamel etching. Both overall marginal adaptation and overall marginal discoloration were worse at 18 months than at baseline

Effect Of Photoinitiator Concentration On Marginal And Internal Adaptation Of Experimental Composite Blends Photocured By Modulated Methods

Objective: The aim of this study was to evaluate the influence of photoinitiator concentration on marginal and internal adaptation of composites photocured by modulated methods. Materials and Methods: Composites based on BisGMA/triethylene glycol dimethacrylate and 65 wt% of filler were prepared with different concentrations of camphorquinone/amine (C1-0.5%, C2-1%, C3-1.5%). Cavities were prepared (3 mm × 3 mm × 2 mm) on the buccal surface of 120 bovine incisors and the adhesive system Adper Single Bond 2 was applied following manufactures instruction. Specimens were then distributed according to type of composite (C1, C2, C3) and photoactivation method (high-intensity - 750 mW/cm2 for 40 s; low intensity - 150 mW/cm2 for 200 s; soft-start - 150 mW/cm2 for 10 s + 750 mW/cm2 for 38 s; pulse-delay - 150 mW/cm2 for 10 s + 3 min dark + 750 mW/cm2 for 38 s). Superficial and internal margins were analyzed by scanning electron microscopy, using the epoxy replica technique. The length of gaps was expressed as a percentage of the total length of the margins. Data were submitted to two-way analysis of variance and Tukey's test (α =0.05). Results: Modulated curing methods did not influence gap formation regarding both superficial and internal adaptation. The composite with the lower initiator concentration (C1) presented higher gap formation when compared with those with higher concentrations (C2 and C3). Conclusion: Modulated photoactivation methods did not reduce gap formation for the experimental composite restorations evaluated. However, higher photoinitiator concentrations promote better marginal seal. © 2013 Dental Investigations Society.75 SUPPL.S1S8Braga, R.R., Ballester, R.Y., Ferracane, J.L., Factors involved in the development of polymerization shrinkage stress in resin-composites: A systematic review (2005) Dent Mater, 21, pp. 962-970Hilton, T.J., Can modern restorative procedures and materials reliably seal cavities? In vitro investigations (2002) Part 2. Am J Dent, 15, pp. 279-289Hilton, T.J., Can modern restorative procedures and materials reliably seal cavities? In vitro investigations (2002) Part 1. Am J Dent, 15, pp. 198-210Amirouche-Korichi, A., Mouzali, M., Watts, D.C., Effects of monomer ratios and highly radiopaque fillers on degree of conversion and shrinkage-strain of dental resin composites (2009) Dent Mater, 25, pp. 1411-1418Atai, M., Watts, D.C., Atai, Z., Shrinkage strain-rates of dental resin-monomer and composite systems (2005) Biomaterials, 26, pp. 5015-5020Schneider, L.F., Consani, S., Sakaguchi, R.L., Ferracane, J.L., Alternative photoinitiator system reduces the rate of stress development without compromising the final properties of the dental composite (2009) Dent Mater, 25, pp. 566-572Ikemura, K., Endo, T., A review of the development of radical photopolymerization initiators used for designing light-curing dental adhesives and resin composites (2010) Dent Mater J, 29, pp. 481-501Pfeifer, C.S., Ferracane, J.L., Sakaguchi, R.L., Braga, R.R., Photoinitiator content in restorative composites: Influence on degree of conversion, reaction kinetics, volumetric shrinkage and polymerization stress (2009) Am J Dent, 22, pp. 206-210Alonso, R.C., Correr, G.M., Cunha, L.G., Brandt, W.C., Puppin-Rontani, R.M., Correr Sobrinho, L., Photoinitiator concentration and modulated-photoactivation: Influence on polymerization characteristics of experimental-composites (2008) J Dent Res, 87, p. 1801. , AbstractMusanje, L., Ferracane, J.L., Sakaguchi, R.L., Determination of the optimal photoinitiator concentration in dental composites based on essential material properties (2009) Dent Mater, 25, pp. 994-1000Yoshida, K., Greener, E.H., Effect of photoinitiator on degree of conversion of unfilled light-cured resin (1994) J Dent, 22, pp. 296-299Nomura, Y., Teshima, W., Kawahara, T., Tanaka, N., Ishibashi, H., Okazaki, M., Genotoxicity of dental resin polymerization initiators in vitro (2006) J Mater Sci Mater Med, 17, pp. 29-32Asmussen, E., Factors affecting the color stability of restorative resins (1983) Acta Odontol Scand, 41, pp. 11-18Ferracane, J.L., Greener, E.H., The effect of resin formulation on the degree of conversion and mechanical properties of dental restorative resins (1986) J Biomed Mater Res, 20, pp. 121-131Ferracane, J.L., Mitchem, J.C., Condon, J.R., Todd, R., Wear and marginal breakdown of composites with various degrees of cure (1997) J Dent Res, 76, pp. 1508-1516Alvim, H.H., Alecio, A.C., Vasconcellos, W.A., Furlan, M., de Oliveira, J.E., Saad, J.R., Analysis of camphorquinone in composite resins as a function of shade (2007) Dent Mater, 23, pp. 1245-1249Alonso, R.C., Correr, G.M., Cunha, L.G., De Moraes Souto Pantoja, C.A., Puppin-Rontani, R.M., Sinhoreti, M.A., Modulated photoactivation methods - Effect on marginal and internal gap formation of restorations using different restorative composites (2007) J Biomed Mater Res B Appl Biomater, 82, pp. 346-351Cunha, L.G., Alonso, R.C., Pfeifer, C.S., Correr-Sobrinho, L., Ferracane, J.L., Sinhoreti, M.A., Modulated photoactivation methods: Influence on contraction stress, degree of conversion and push-out bond strength of composite restoratives (2007) J Dent, 35, pp. 318-324Cunha, L.G., Alonso, R.C., Pfeifer, C.S., Correr-Sobrinho, L., Ferracane, J.L., Sinhoreti, M.A., Contraction stress and physical properties development of a resin-based composite irradiated using modulated curing methods at two C-factor levels (2008) Dent Mater, 24, pp. 392-398Alonso, R.C., Cunha, L.G., Correr, G.M., De Goes, M.F., Correr-Sobrinho, L., Puppin-Rontani, R.M., Association of photoactivation methods and low modulus liners on marginal adaptation of composite restorations (2004) Acta Odontol Scand, 62, pp. 298-304Brandt, W.C., de Moraes, R.R., Correr-Sobrinho, L., Sinhoreti, M.A., Consani, S., Effect of different photo-activation methods on push out force, hardness and cross-link density of resin composite restorations (2008) Dent Mater, 24, pp. 846-850Souza-Junior, E.J., de Souza-Régis, M.R., Alonso, R.C., de Freitas, A.P., Sinhoreti, M.A., Cunha, L.G., Effect of the curing method and composite volume on marginal and internal adaptation of composite restoratives (2011) Oper Dent, 36, pp. 231-238Cunha, L.G., Alonso, R.C., de Souza-Junior, E.J., Neves, A.C., Correr-Sobrinho, L., Sinhoreti, M.A., Influence of the curing method on the post-polymerization shrinkage stress of a composite resin (2008) J Appl Oral Sci, 16, pp. 266-270Alonso, R.C., Cunha, L.G., Correr, G.M., Cunha Brandt, W., Correr-Sobrinho, L., Sinhoreti, M.A., Relationship between bond strength and marginal and internal adaptation of composite restorations photocured by different methods (2006) Acta Odontol Scand, 64, pp. 306-313Alomari, Q.D., Barrieshi-Nusair, K., Ali, M., Effect of C-factor and LED curing mode on microleakage of class v resin composite restorations (2011) Eur J Dent, 5, pp. 400-408Lindberg, A., Peutzfeldt, A., van Dijken, J.W., Effect of power density of curing unit, exposure duration, and light guide distance on composite depth of cure (2005) Clin Oral Investig, 9, pp. 71-76Lim, B.S., Ferracane, J.L., Sakaguchi, R.L., Condon, J.R., Reduction of polymerization contraction stress for dental composites by two-step light-activation (2002) Dent Mater, 18, pp. 436-444Yoshikawa, T., Burrow, M.F., Tagami, J., A light curing method for improving marginal sealing and cavity wall adaptation of resin composite restorations (2001) Dent Mater, 17, pp. 359-366Sahafi, A., Peutzfeldt, A., Asmussen, E., Effect of pulse-delay curing on in vitro wall-to-wall contraction of composite in dentin cavity preparations (2001) Am J Dent, 14, pp. 295-296Asmussen, E., Peutzfeldt, A., Influence of pulse-delay curing on softening of polymer structures (2001) J Dent Res, 80, pp. 1570-1573Yazici, A.R., Celik, C., Dayangac, B., Ozgunaltay, G., Effects of different light curing units/modes on the microleakage of flowable composite resins (2008) Eur J Dent, 2, pp. 240-246Park, Y.J., Chae, K.H., Rawls, H.R., Development of a new photoinitiation system for dental light-cure composite resins (1999) Dent Mater, 15, pp. 120-127Kemp-Scholte, C.M., Davidson, C.L., Complete marginal seal of Class V resin composite restorations effected by increased flexibility (1990) J Dent Res, 69, pp. 1240-1243Taira, M., Urabe, H., Hirose, T., Wakasa, K., Yamaki, M., Analysis of photo-initiators in visible-light-cured dental composite resins (1988) J Dent Res, 67, pp. 24-28Shintani, H., Inoue, T., Yamaki, M., Analysis of camphorquinone in visible light-cured composite resins (1985) Dent Mater, 1, pp. 124-126Calheiros, F.C., Daronch, M., Rueggeberg, F.A., Braga, R.R., Influence of irradiant energy on degree of conversion, polymerization rate and shrinkage stress in an experimental resin composite system (2008) Dent Mater, 24, pp. 1164-1168Geurtsen, W., Spahl, W., Leyhausen, G., Variability of cytotoxicity and leaching of substances from four light-curing pit and fissure sealants (1999) J Biomed Mater Res, 44, pp. 73-77Moin Jan, C., Nomura, Y., Urabe, H., Okazaki, M., Shintani, H., The relationship between leachability of polymerization initiator and degree of conversion of visible light-cured resin (2001) J Biomed Mater Res, 58, pp. 42-46Larson, T.D., The clinical significance of marginal fit (2012) Northwest Dent, 91, pp. 22-29Irie, M., Suzuki, K., Watts, D.C., Marginal gap formation of light-activated restorative materials: Effects of immediate setting shrinkage and bond strength (2002) Dent Mater, 18, pp. 203-210Marshall Jr., G.W., Marshall, S.J., Kinney, J.H., Balooch, M., The dentin substrate: Structure and properties related to bonding (1997) J Dent, 25, pp. 441-458Bechtold, J., Dos Santos, P.J., Anido-Anido, A., Di Hipólito, V., Alonso, R.C., D'Alpino, P.H., Hardness, polymerization depth, and internal adaptation of Class II silorane composite restorations as a function of polymerization protocol (2012) Eur J Dent, 6, pp. 133-140Frankenberger, R., Pashley, D.H., Reich, S.M., Lohbauer, U., Petschelt, A., Tay, F.R., Characterisation of resin-dentine interfaces by compressive cyclic loading (2005) Biomaterials, 26, pp. 2043-2052Momoi, Y., Iwase, H., Nakano, Y., Kohno, A., Asanuma, A., Yanagisawa, K., Gradual increases in marginal leakage of resin composite restorations with thermal stress (1990) J Dent Res, 69, pp. 1659-1663Correr, G.M., Bruschi Alonso, R.C., Puppin-Rontani, R.M., Correr-Sobrinho, L., Coelho Sinhoreti, M.A., Marginal and internal adaptation of composite restorations using a resin liner on deproteinized substrate (2005) Acta Odontol Scand, 63, pp. 227-232Lopes, M.B., Costa, L.A., Consani, S., Gonini, A.J., Sinhoreti, M.A., SEM evaluation of marginal sealing on composite restorations using different photoactivation and composite insertion methods (2009) Indian J Dent Res, 20, pp. 394-399Amaral, C.M., Peris, A.R., Ambrosano, G.M., Pimenta, L.A., Microleakage and gap formation of resin composite restorations polymerized with different techniques (2004) Am J Dent, 17, pp. 156-160Kinomoto, Y., Torii, M., Takeshige, F., Ebisu, S., Comparison of polymerization contraction stresses between self- and light-curing composites (1999) J Dent, 27, pp. 383-389Davidson, C.L., Feilzer, A.J., Polymerization shrinkage and polymerization shrinkage stress in polymer-based restoratives (1997) J Dent, 25, pp. 435-440Braga, R.R., Ferracane, J.L., Contraction stress related to degree of conversion and reaction kinetics (2002) J Dent Res, 81, pp. 114-118Calheiros, F.C., Kawano, Y., Stansbury, J.W., Braga, R.R., Influence of radiant exposure on contraction stress, degree of conversion and mechanical properties of resin composites (2006) Dent Mater, 22, pp. 799-80

Morphology and topography analysis of mesoporous titania templated by micrometric latex sphere arrays

In this work, mesoporous titania is prepared by templating latex sphere arrays with four different sphere diameters at the micrometric scale (phi > 1 mu m). The mesoporous titania homogeneously covers the latex spheres and substrate, forming a thin coating characterized by N-2 adsorption isotherm, small angle X-rays scattering, atomic force, field emission and transmission electronic microscopies. Mesoporous titania has been templated into different shapes such as hollow particles and monoliths according to the amount of sol used to fill the voids of the close packed latex spheres. Titania topography strongly depends on the adsorption of polymeric segments over latex spheres surface, which could be decreased by changing the dimensions of latex spheres (phi = 9.5 mu m) generating a lamellar architecture. Thus, micrometric latex sphere arrays can be used to achieve new surface patterns for mesoporous materials via a fast and inexpensive chemical route for construction of functional devices in different technological fields such as energy conversion, inclusion chemistry and biomaterials. (C) 2011 Elsevier Inc. All rights reserved.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2008/00463-2]Chemistry Institute of the University of Sao Paulo, BrazilChemistry Institute of the University of Sao Paulo, Brazi