Effect of irradiation mode and filling technique on resin/dentin bonding strength in class I cavities

Abstract

Factors such as light-curing mode, filling technique and cavity configuration may affect the bonding strength to dentin. This study evaluated the effect of irradiation mode and filling technique on resin/dentin bonding strength on the buccal wall of class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Occlusal cavities (4 x 3 x 3 mm) were prepared in dentin. The adhesive Single Bond was applied according to the manufacturer's instructions and TPH Spectrum composite resin was placed using the following: oblique incremental, horizontal incremental or bulk filling techniques. The composite resin was light-cured either by continuous (600 mW/cm² for 40 s) or Soft-Start (250 mW/cm² for 10 s + 600 mW/cm² for 30 s) modes. Specimens of the control group were obtained by bonding the material to the flat exposed buccal wall of the cavity (C-factor = 1). The teeth were stored in water at 37 o C for 24 h and prepared for microtensile testing. Bonded beams of approximately 0.8 mm² were obtained from the buccal wall and tested with a tension of 0.5 mm/min. Results were analyzed by two-way ANOVA, Tukey's test and Dunnett's test (α = 0.05). Incremental placement techniques with both irradiation modes produced higher bonding strength values than the bulk technique (p < 0.05). Bonding strength tested in the cavities had lower values than those obtained in flat dentin surfaces (control group) (p < 0.05), except for incremental fillings using stepped irradiation. Bonding strength to the cavity walls depends on the filling technique and on the irradiation mode of composite resins. DESCRIPTORS: Composite resins; Dentin; Dental cements; Dental enamel. RESUMO:Fatores como o modo de ativação, a técnica restauradora e a configuração cavitária podem afetar a resistência adesiva à dentina. Este estudo avaliou os efeitos dos modos de ativação e das técnicas restauradoras na resistência de união compósito/dentina na parede vestibular de restaurações classe I. O esmalte oclusal dos dentes foi removido para expor uma superfície dentinária planificada. Cavidades oclusais (4 x 3 x 3 mm) foram preparadas em dentina. O adesivo Single Bond foi aplicado de acordo com as instruções do fabricante, e o compósito TPH Spectrum, inserido através de três diferentes técnicas: oblíqua incremental, horizontal incremental ou incremento único. O compósito foi ativado utilizando o método contínuo (600 mW/cm² por 40 s) ou "Soft-Start" (250 mW/cm² por 10 s + 600 mW/cm² por 30 s). O grupo controle foi obtido pela união somente à parede vestibular planificada (fator C = 1). Os dentes foram armazenados por 24 h em água a 37 o C e preparados para o ensaio de microtração (0,5 mm/min). Os espécimes apresentaram na secção transversal uma área de união de aproximadamente 0,8 mm². Os resultados foram analisados pela ANOVA (dois fatores), pelos testes de Tukey e Dunnett (α = 0,05). A técnica incremental seguida da ativação com ambas as formas de fotopolimerização produziu maiores valores de resistência de união que a técnica...

Effect of Incremental Filling Technique on Adhesion of Light-cured Resin Composite to Cavity Floor

“…Santos, et al 16) , for example, reported that an incremental technique resulted in higher bond strength than a bulk filling technique. On the other hand, other studies on different filling techniques have not detected any difference in bond strength 12,17) which implies that further studies are required in this field.…”

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“…It was observed that stresses increased with a lowelasticity modulus base, and it therefore seems appropriate to use high-elasticity base materials. 59 Cusp deformation and recovery under load proved to be influenced by cavity extent and restorative material (composite or porcelain).…”

“…Once again, these findings were product specific. 59 Other authors concluded again that the use of a FRC liner alone did not improve MTBS underneath bulk-filled restorations with a high C-factor, while the presence of fibers or a combination or FRC together with fibers did increase MTBS. 66 Incorporation of glass fibers also showed stable BS values regardless of the C-factor.…”

“…31, [56][57][58][59] Under load, interfacial stresses were mainly of a tensile nature in inlay restorations, while they were of a compressive nature in onlay restorations. 56 Rigid porcelain restorations, compared to less rigid composite, featured more stress at the occlusal surface but reduced crown deformation and stress magnitude at the adhesive interface.…”

“…They all concluded that a bulk-fill technique did lead to lower bond strength compared to restorations placed incrementally. [58][59][60][61] The results regarding the influence of different layering approaches proved rather controversial, with some studies 59 showing higher bond strength values for the horizontal technique, while two other studies 58,60 concluded that there was no difference between horizontal and oblique or vertical layering techniques. When combining three to four horizontal and oblique layers in different geometries, the highest microtensile bond strength (MTBS) values were observed with the four increments.…”