Effect of Preparation and Storage on Adhesive Monomer Conversion
Objectives: To study the effect of sample preparation and storage conditions on the degree of conversion (DC) of two adhesive systems using micro-Raman spectroscopy.Methods: Sixty samples each of an etch-and-rinse (Excite) and a self-etch (Clearfil 3S) adhesive were prepared on glass slides and allocated to groups G1-G6 (n=10). Thirty samples of each adhesive were prepared on dentine discs according to manufacturer's instructions and allocated to groups D1-D6 (n=5). In groups G1 and D1, each sample was covered with a Mylar strip and cured for 10 s with a bluephase LED unit. In groups G2 and D2, samples were cured without the Mylar strip. Micro-Raman spectra were taken 5 min post-curing. Groups G3-G6 and D3-D6 were covered with Mylar strips, cured according to the same protocol and stored for 24 h: G3 and D3 at 22±2ºC and 45±3% humidity; G4 and D4 at 37±1ºC and 90±2% humidity; G5 and D5 in distilled water at 37±1ºC; G6 and D6 in buffered incubation medium at 37±1ºC. Micro-Raman spectra were taken 5 min post-curing and after storage. Data were analyzed using t-tests and repeated measures ANOVA and the level of significance was α=0.05.
Results: Higher DC values were found on dentine than glass for both adhesives (p<0.05). Higher DC values were found for both adhesives when cured on dentine with than without Mylar strips (p<0.05). Higher DC values were found for Excite cured on glass with than without Mylar strips (p<0.05), but there was no difference for Clearfil 3S (p>0.05). Both adhesives cured on dentine gave higher DC after 24 h storage irrespective of the medium (p<0.05). Excite G3 group and Clearfil 3S G3 and G4 groups showed higher DC values after storage (p<0.05).
Conclusions: Sample preparation methods and storage conditions significantly affected the DC of Excite and Clearfil 3S.
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