title: Step-cure polymerization: effect of initial light intensity on resin/dentin bond strength in class I cavities.
abstract: This in vitro study assessed the effect of a step-cure light curing method on resin/dentin bond strength on the buccal wall of Class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Twenty four box-shaped cavities (C-factor = 4.5) were prepared in dentin. Prime&Bond 2.1 was applied and TPH Spectrum (Dentsply) was inserted using a bulk-filling increment. The composite was light-cured using either a step-cure photoactivation technique or a one-step continuous curing method. For step-cure polymerization, the initial cure intensity was varied by changing the distance between the light source and the resin surface. The light-cured resins were cured using four low light intensities: 150(G1), 200(G2), 250(G3) and 300(G4) mW/cm2. In the continuous exposure curing method, the samples were light-activated for 40 seconds at 740 mW/cm2 and irradiation was applied in a box-shaped cavity and a flat cavity (exposed buccal wall, C-factor = 0.22). Samples were prepared for TBS testing by creating bonded beams (of approximately 0.8 mm2) obtained from the buccal wall. The data were analyzed using one-way ANOVA, Tukey Test and Dunnett's Test at a significance level of 0.05. The mean TBS values for the continuous exposure group in the flat and box-shaped cavities were 24.31 and 10.23 MPa, respectively. The corresponding TBS for step-cure polymerization was 23.13 (G3), 18.83 (G2), 14.87 (G1) and 13.26 MPa (G4). Bond strength values to the cavity wall were lower in the three-dimensional cavities and dependent on the light curing method (p < 0.05). The use of a low initial light intensity (200-250 mW/cm2) for 10 seconds followed by high irradiation intensity provided the best bond strengths, similar to bonding in a flat cavity.
authors.affiliation: Potiguar School of Dentistry, Potiguar University-UnP, RN, Brazil. alexjss@yahoo.com
authors.forename: Alex José Souza
authors.initials: AJ
authors.lastname: Santos
authors.forename: Carlos Frederico
authors.initials: CF
authors.lastname: Sarmento
authors.forename: Abuabara
authors.initials: A
authors.lastname: Abuabara
authors.forename: Flávio Henrique Baggio
authors.initials: FH
authors.lastname: Aguiar
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Lovadino
mesh_terms: D000096:Acetone / Q000737:chemistry / Q000528:radiation effects; D000268:Adhesiveness; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification*; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry / Q000528:radiation effects; D006801:Humans; D008027:Light; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D011829:Radiation Dosage; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D011108:Polymers; D011109:Polymethacrylic Acids; C467914:TPH spectrum; C444444:prime and bond 2.1; D000096:Acetone