Method: Forty identical composite block tooth replicates of molar MOD-onlay preparations were fabricated. A standardized three-surface Empress CAD (Ivoclar Vivadent Liechtenstein) porcelain onlay was designed and manufactured utilizing Cerec-3D (Sirona Dental Systems,NC.USA) and replicated forty times. Bonding surfaces of porcelain were etched with hydrofluoric acid and silinated. Onlays were randomly cemented with one of two cements Multi-Link (Ivoclar)-(M) and Relyx (3M) St Paul MN, USA)-(R) and immediately polymerized (I) for 20-seconds with a Valo (Ultradent S.Jordan,UT.USA) or allowed to autopolymerize-(A) for five minutes followed by a 20-second light-cure. Ten specimens each MI, MA, RI and RA were cemented-polymerized. Specimens were stored for a minimum of two-weeks prior to 3D microCT (at 100uA) analysis performed with Bruker Skyscan1172 (Madison,WI.USA). MicroCT images were individually reconstructed/analyzed for the presence of voids and software reassembled to determine the volume and number of voids utilizing NRECON and CTAn (Skyscan). Mean void size and percent voids calculated and ANOVA utilized to evaluate significant difference.
Result: Mean number of voids(+s.d.): RI 150(+46), RA 55(+25), MI 7(+8), MA 23(+26) and percent voids(+s.d.) RI 46(+14), RA 52(+11), MI 1.3(+1.4), MA 1.5(+1.0) were calculated for significant differences. Relyx had significantly greater numbers and percent voids than Multi-Link (p<0.01).
Conclusion: Multi-Link showed no difference in number or percentage of voids between the immediate light-curing and chemical-cure followed by light-cure. Relyx chemical-cure followed by light-cure demonstrated smaller size, number, and percentage of voids than immediate light-cure. Size, number, and percent of voids may influence bond strength and performance and require further investigation.