Effect of light-activation methods and water storage on the flexural strength of two composite resins and a compomer

Abstract

ABSTRACT:The present study evaluated the flexural strength of three composite resins recommended for direct esthetic restorations: a polyacid modified composite (Dyract AP), a unimodal composite resin (Filtek Z250) and a hybrid composite resin (Point 4). The variation factors, apart from the type of composite resin, were the light activation method and the water storage period. The composite resins were light-cured in continuous mode (40 s, 500 mW/cm²) or in ramp mode (0-800 mW/cm² for 10 s followed by 30 s at 800 mW/cm²) and stored for 24 hours or 30 days in distilled water at 37°C. The data were analyzed by ANOVA and Tukey test for multiple comparisons RESUMO:O presente estudo analisou a resistência à flexão de três compósitos recomendados para restaurações estéticas diretas: um compósito poliácido-modificado (Dyract AP), uma resina composta unimodal (Filtek Z250) e uma resina composta híbrida (Point 4). Os fatores de variação, além do tipo de compósito, foram o método de fotoativação e o período de armazenagem em água. Os materiais foram fotoativados continuamente por 40 s (500 mW/ cm²) ou com intensidade de luz crescente (0-800 mW/cm² por 10 s seguidos de 30 s a 800 mW/cm²). Os períodos de armazenagem foram de 24 horas ou 30 dias em água destilada a 37°C. Os dados foram submetidos à análise de variância e ao teste de Tukey para comparações múltiplas (α = 0,05). A resina composta Z250 apresentou a maior média de resistência à flexão (166,74 MPa) e a Dyract AP, a menor (129,76 MPa). A armazenagem por 30 dias diminuiu a resistência à flexão para o método de fotoativação crescente (24 h: 156,64 MPa; 30 dias: 135,58 MPa). O método de fotoativação isoladamente não conduziu a diferentes valores de resistência à flexão. DESCRITORES: Compômeros; Materiais dentários; Resinas compostas. INTRODUCTIONLight-cured composite resins have become an almost universal material in current dental practice. Although many studies concerning earlier generations of composite resins still emphasize their lower mechanical properties, the most recent composites have achieved wear resistance similar to that of amalgam restorations at the critical occlusal contact area 11,17 .A variety of light activation methods and different sources were proposed aiming to improve the quality of the cure, which would assure the physical properties of the resulting composite resin restorations 4,15,25 . Additionally, a slower polymerization rate could optimize the stress relief by flow at the early stages of the reaction 7 and contribute to minimize the adverse effects related to polym-* PhDs, Professors; ****MSc, PhD Student; *****Full Professor -Department of Dental Materials, School of Dentistry, University of São Paulo. ** MSc, Assistant Professor, Planalto Central Educational Union. *** PhD, Private Practice, São Paulo, SP, Brazil. 2006;20(2):143-7 Effect of light-activation methods and water storage on the flexural strength of two composite resins and a compomer Efeito da fotoativação e da armazenagem em água na resistência à flexão de duas resi...

Influence of Curing Mode on the Surface Energy and Sorption/Solubility of Dental Self-Adhesive Resin Cements

“…On the contrary, MCE and MLS did not demonstrate significant differences in Δ G sws between the two curing modes. These findings imply that, in some cured SARCs, different arrangements of functional groups of the acidic monomers during polymerization (depending on the curing mode used) may result in differences in the surface energy characteristics between the two curing modes [9]. Since the influence of curing mode on surface energy parameters was found to be material-dependent, the first hypothesis has to be partially rejected.…”

“…Therefore, dual-cured resin cements—including SARCs—should achieve their maximum DC and, if possible, high surface hydrophobicity to withstand such intraoral challenges [29]. Increased water sorption of a resin cement can degrade its mechanical properties by the plasticizing effect and also by dissolving and leaching out of unreacted monomers and filler particles [9,19,29,30]. Changes in bulk properties of the resin-based composite after immersion in a solution were not included in this study; further investigation is needed.…”

“…In addition, the curing protocol of SARCs may affect the surface energy, when considering possible differences in the polymer network and residual monomers [9], thus also potentially affecting the degradation of the materials. However, there are few studies regarding the influence of SARC curing methods on the surface energy characteristics and, as a result, sorption/solubility.…”

The Evaluation of Flexural Strength of Composite Resin Materials with and without Fiber

“…Sideridou et al [25] stated that no significant difference between the 1st and 30th days was observed in stored distilled water and artificial saliva. Rodrigues Filho et al [37] stated that there was no significant decrease in the flexural strength of two different type of composite resins when they were kept in water. Gohring et al [6] reported that flexural strength of glass fiber was affected by neither keeping in water nor thermocycling.…”

Effect of Food Stimulated Liquids and Thermocycling on the Monomer Elution from a Nanofilled Composite

“…Rode and Kawano found that the degree of conversion of a dental composite (Z250) cured with high intensity halogen, LED, or argon laser curing unites varies between 35-70% [5]. It has shown than unreacted monomers remain in the mass of restoration and release into the surrounding area (dentine, pulp, or oral cavity) which can negatively affect the biocompatibility of the material [6, 7]. …”