The effect of light-curing source and mode on microtensile bond strength to bovine dentin.
OBJECTIVE
The purpose of this study was to evaluate the effects of different light-curing techniques on the microtensile bond strength of hybrid and packable resin composite to dentin. The null hypotheses were that different light-curing techniques do not affect the adhesion of resin composites to tooth structure and that different resin composites do not have a similar bond to dentin.


METHODS
One hundred four box-shaped buccal preparations were made and dentin/enamel adhesive was applied according to the manufacturer's instructions (Single Bond 3M ESPE). A hybrid resin composite (Filtek Z250, A2, 3M ESPE) or a packable resin composite (Solitaire 2, A2, Heraeus Kulzer) were inserted in bulk and polymerized using one of these techniques (n = 13): (a) Soft-start (SS) using a halogen lamp (QTH); (b) LED low intensity; (c) Plasma arc (PAC) curing for 6 s for packable resin composite and 3 s for the hybrid resin composite; (d) Conventional (C) QTH curing for 40 s. Afterwards, specimens were thermocycled 1,000 times between 5 degrees C and 55 degrees C in tap water, and were sectioned into beams with a rectangular cross-sectional area of approximately 1 mm2. Microtensile bond strength testing was performed using a universal testing machine at a crosshead speed of 0.5 mm/min.


RESULTS
Bond strength means +/- (SD) in MPa were: Filtek Z250: SSQTH = 17.9 (5.4); LED = 17.9 (6.4); PAC = 16.8 (6.8); CQTH = 16.1 (4.6). Solitaire 2: SSQTH = 12.4 (6.4); LED = 15.5 (4.3); PAC = 16.2 (4.4); CQTH = 13.8 (5.7). The data were structured in a split-plot design and analyzed by a two-way ANOVA and Tukey's tests (alpha = 0.05).


CONCLUSIONS
The light-curing method did not significantly affect bond strengths. However, the bond strengths of the packable resin composite were significantly lower than those of the hybrid resin composite for all polymerization techniques, suggesting that the restorative material itself might be a more critical factor in adhesion than the curing method.
Dental Research and Graduate Studies Division, Department of Restorative Dentistry, Guarulhos University (UnG), Guarulhos, Brazil.
Cristiane Mariote
CM
Amaral
Alessandra Rezende
AR
Peris
Glaucia Maria Bovi
GM
Ambrosano
Edward J
EJ
Swift
Luiz André Freire
LA
Pimenta
D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects*; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D001840:Dental Bonding / Q000379:methods*; D017220:Dentin-Bonding Agents / Q000737:chemistry / Q000528:radiation effects*; D008027:Light; D011140:Polyurethanes / Q000737:chemistry / Q000528:radiation effects*; D013718:Tensile Strength / Q000528:radiation effects
D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D011140:Polyurethanes