Clinical Evaluation of Lithium Disilicate Chair-side CAD/CAM Crowns

Methods: One clinician placed 62 crowns in 43 patients. The crown preparation had a minimum of 1.5 mm occlusal reduction, 1.2 mm axial reduction, and rounded shoulder margins. A CEREC 3 unit (Sirona Dental) with software v2.80 was used to fabricate the CAD/CAM crowns chair-side. After milling, the crowns were fired under vacuum to complete the lithium disilicate crystallization process. The crowns were etched internally with 4.9% HF acid, silanated, and then cemented with either a self-etching bonding agent and resin cement (ML = MultiLink Automix; Ivoclar Vivadent) or a self-adhesive resin cement (EC = Experimental Cement; Ivoclar Vivadent).

Results: Tooth sensitivity was evaluated by report to cold stimulus (number of teeth): 2 weeks: ML (5), EC (4) with no sensitivity reported in either group after 3 weeks through 2 years. The crowns were evaluated by two examiners using a modified USPHS rating. There was no difference in the gingival index and plaque index between the test crowns and the control teeth. The percentage alpha scores (baseline, 6 months, 1 year, 2 year) were: color match - ML (100, 96, 96, 96,), EC (97, 95, 95, 97); margin discoloration - ML (100, 96, 87, 83,), EC (100, 97, 97, 97). The percentage of alpha scores for margin adaptation, caries, and crown fracture were 100% for both groups of crowns at all recall intervals. No surface chipping has been identified on any of the crowns after two years. Two crowns cemented with the experimental cement debonded. One occurred at 13 months and one at 20 months.

Conclusions: The lithium disilicate crowns have performed well at 2 years. This study was supported by a grant from Ivoclar Vivadent.