Moisture spectrum of demineralized dentin for adhesive systems with different solvent bases.
OBJECTIVE
To determine the effects of different surface moisture on the bond strength of an ethanol/water-based (Single Bond [SB]), an acetone-based (One-Step [OS]), and a water-based (Syntac Single Component [SC]) adhesive system to dentin.


METHODS
On 90 human third molars, a flat superficial dentin surface was exposed by abrasion with 600-grit SiC paper. The adhesives were applied to a delimited area of 52 mm2 according to the manufacturers' instructions on either dry (oil-free air/30 s) or rewetted surfaces (1.5, 2.5, 3.5, 4.0 or 4.5 microl of distilled water), and composite crowns were constructed incrementally. After storage in distilled water at 37 degrees C for 24 h, the teeth were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks with a cross-sectional area of 0.8 mm2. The specimens were tested in tension at 0.5 mm/min and the fracture mode analyzed. Resultant bond strength was expressed as an index that includes bond strength values of the different fracture patterns and the specimens that failed during preparation for the microtensile testing. The data was analyzed by two-way ANOVA, Tukey's multiple comparison, and regression analysis.


RESULTS
Highly significant main effects and interaction (p < 0.0001) were detected. A quadratic relationship between the bond strength index and the surface moisture was identified (R2 = 0.95, p < 0.001). SB showed a maximum bond strength (42.2 +/- 6.7 MPa) that was statistically similar (p = 0.4996) to the maximum bond strength of OS (40.1 +/- 4.6 MPa), although obtained at a different degree of moisture (ca 1.5 microl for SB and 3.5 microl for OS). SC showed its maximum bond strength (27.7 +/- 3.9 MPa) with 1.5 microl moisture. SB presented its highest bond strength at 1.5 microl of water, which was significantly higher than the bond strength obtained at any other degree of moisture (p < 0.05). OS achieved its maximum bond strength at 3.5 microl of water; however, that value was not statistically different (p > 0.05) from the values obtained with 1.5 microl to 4.0 microl of water. Similarly, highest bond strengths obtained with SC were not different (p > 0.05) within the range of 0 microl to 3.5 microl of water.


CONCLUSIONS
All adhesive systems tested had a different moisture spectrum in which higher bond strengths were obtained. SB and SC performed better on a drier substrate, while OS showed better performance on wetter substrates. OS and SC had a broader range of moisture within which maximal bond strength could be achieved.
Reis
Alessandra
A
Department of Dental Materials and Operative Dentistry, University of Oeste de Santa Catarina, SC, Brazil. reis_ale@hotmail.com
Loguercio
Alessandro Dourado
AD
Azevedo
Caio Lucidius Naberezny
CL
de Carvalho
Ricardo Marins
RM
da Julio Singer
Motta
M
Grande
Rosa Helena Miranda
RH
D000096:Acetone / Q000737:chemistry; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D001840:Dental Bonding; D003804:Dentin / Q000737:chemistry / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D012044:Regression Analysis; D019279:Resin Cements / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry*
C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; D012997:Solvents; C078484:Syntac dentine adhesive; C115612:single bond; D014867:Water; D000096:Acetone; D000431:Ethanol; D017438:Bisphenol A-Glycidyl Methacrylate