Shear Bond Strength of Self-Adhesive Cements to CAD/CAM Porcelain Substrates

Shear Bond Strength of Self-Adhesive Cements to CAD/CAM Porcelain Substrates Objective: to test and compare shear bond strengths (SBS) of two self-adhesive resin cements (Maxcem/Kerr and Unicem/3M ESPE), along with a RMGI cement (FujiCem/GC America) to two CEREC CAD/CAM porcelain substrates (Vitablocs Mark II/Vita Zahnfabrik and ProCad/Ivoclar) subjected to two different surface treatments. Methods: All substrates were polished with 600 grit SiC paper and then further subjected to two different surface treatments: (I) recommended treatment (control): 9.5% HF (Gresco Products Inc.) etching + Silane primer (Kerr); and (II) modified treatment: Air-abrasion (AA) with 50µ Al₂O₃ + 9.5% HF etching. Bonding was conducted with an Ultradent jig having a cylindrical mold (D=2.38mm) into which each cement was extruded and allowed to self-cure. The bonded specimens (n=8 per group) were stored in de-ionized water (37ºC) for 24 hours before debonding on an Instron mechanical tester using shear force. Results:

Shear Bond Strength, MPa

CEREC Porcelain Substrates

Surface Treatments

Self-Adhesive Cements

FujiCem

Maxcem

Unicem

VitaBlocs

I (HF + Silane)

9.8±4.4^b

25.0±2.2^a

19.6±4.0^a

II (AA + HF)

10.1±3.2^b

22.2±6.0^a

21.0±3.2^a

ProCAD

I (HF + Silane)

7.5±2.0^D

17.8±2.9^A,B

15.9±3.6^B,C

II (AA + HF)

12.7±2.2^C

22.4±4.2^A

20.3±2.9^A,B

*Means with the same letter for each substrate are not statistically different from each other at p = 0.05. Analysis: ANOVA analysis revealed that both Maxcem and Unicem had significantly higher (p<0.05) SBS's than FujiCem for all substrate/treatment combinations. The SBS's of Maxcem and Unicem are not statistically (p=0.05) different from each other for all substrate/treatment combinations. For both substrates, there are no statistical differences (p=0.05) in SBS between two different surface treatments for each cement with the exception of FujiCem/ProCAD combination. Conclusion: the order of bond strengths to all substrate/treatment combinations is Maxcem followed by Unicem and FujiCem. Both surface treatments yields comparable SBS's for each substrate for the two self-adhesive resin cements studied.