Sy. Lee et al., EFFECTS OF FOOD ORAL SIMULATING FLUIDS ON MICROSTRUCTURE AND STRENGTHOF DENTIN BONDING AGENTS/, Journal of oral rehabilitation, 23(5), 1996, pp. 353-361
This Study evaluated the effect a food simulating solution, 75% v/v et
hanol/water, and an artificial saliva, Moi-Stir, have on the microstru
cture and on the diametral tensile strength (DTS) of three dentine bon
ding agents (Tenure, Scotchbond Multi-Purpose and Optibond). The micro
structure was examined by using a scanning electron microscope (SEM).
The DTS data were analysed using ANOVA and the Tukey LSD test. The mic
rostructural observations were compared with changes in DTS. The SEM o
bservation revealed deterioration of all bonding agents due to conditi
oning in the solutions for 30 days. The different solutions appeared t
o cause different reactions in the bonding agents. However, these effe
cts may be exaggerated due to the presence of an air-inhibited surface
layer. Those conditioned in Moi-Stir showed swelling. The presence of
filler particles in the Optibond bonding agent appears to decrease th
e deterioration resulting from soaking. Materials conditioned in ethan
ol exhibited both dissolution and thinning. Diametral samples of each
bonding material were tested after being conditioned in the above-ment
ioned solutions for 1, 7, 14 and 30 days. Conditioning significantly d
ecreased the DTS of all bonding agents, except Optibond in Moi-Stir. F
illed Optibond maintained its DTS longer than did the two unfilled bon
ding agents. The decrease in DTS of all the ethanol-conditioned groups
is a function of the square root of time (P < 0.001) and conforms to
Fick's laws of diffusion. The filled Optibond showed a lower ethanol d
iffusivity (0.5 x 10(-5) cm(2) s(-1)) than the other two unfilled bond
ing agent systems (average 1 2 x 10(-5) cm(2) s(-1)) (P < 0.05). The h
igh ethanol diffusivities were thought to be due to the presence of HE
MA, a hydrophilic resin, in the bonding agent. These results also sugg
est that solution uptake occurred through the resin matrix. Filler par
ticles may therefore play an important role in weathering resistance o
f these materials to oral environment solutions. The physical appearan
ce and strength of dentine bonding agents are significantly altered by
exposure to oral environment solutions.