Microleakage Evaluation of All-Ceramic Crowns Bonded Above/Below the CEJ

Objectives: To measure marginal microleakage of bonded IPS e.max lithium disilicate crowns of teeth with marginal preparations above and below the cementoenamel junction (CEJ) between 3 classes of self-adhesive resin luting agents: 1-RelyX (3M ESPE), 2-MultiLink (Ivoclar), and 3-SpeedCEM (Ivoclar).

Methods: Eighteen (18) extracted human molars were prepped for all-ceramic crowns as follows: 1mm circumferential shoulder gingival margin, 2mm occlusal reduction, rounded internal angles, and less than 20° total occlusal convergence. Teeth were placed in full dentate typodonts and scanned with E4D optical laser CAD/CAM system. Crowns were cemented according to manufacturer's instruction, under 100N load. Samples were thermocycled for 2,500 cycles between 5°C-55°C, immersed in 50% w/v ammoniacal silver nitrate solution for three hours, then exposed in photo developing solution for sixteen hours. Samples were embedded in acrylic, sectioned buccal-lingually, and examined under magnification. A microleakage scale of 0–4 was used. 0=no microleakage; 1=up to 25% microleakage to axial wall; 2=up to 50%; 3=up to 75%; 4=100% penetration to axial wall.  The frequency of each microleakage score was tabulated for all combinations of product and leakage location. Generalized estimating equations were used to analyze the results. A P-value<0.05 was considered statistically significant. SAS 9.2 was used in all analyses.

Results: Samples above the CEJ exhibited greater microleakage than below; the difference was statistically significant (P=0.04). The difference between products was not statistically significant (P=0.12).

 

Group	CEJ	0	1	2	3	4	Total
1	Above	1(16.7%)	0(0%)	1(16.7%)	3(50.0%)	1(16.7%)	6(100%)
	Below	2(33.3%)	1(16.7%)	1(16.7%)	0(0%)	2(33.3%)
2	Above	2(33.3%)	2(33.3%)	1(16.7%)	1(16.7%)	0(0%)	6(100%)
	Below	4(66.7%)	2(33.3%)	0(0%)	0(0%)	0(0%)
3	Above	1(16.7%)	1(16.7%)	2(33.3%)	1(16.7%)	1(16.7%)	6(100%)
	Below	4(66.7%)	1(16.7%)	1(16.7%)	0(0%)	0(0%)

Conclusions: With current self-adhesive luting cements, all-ceramic crown marginal preparations should be seated on dentin to prevent marginal leakage.