CM cement capable of retaining lithium disilicate crowns, Finds study

The study is published in the Journal of Esthetic and Restorative Dentistry.

Kerry R. Streiff and colleagues from the Department of Restorative Dentistry, University of Washington School of Dentistry, Seattle, Washington, USA conducted the present study with the objective to determine if a recent bioactive cement provides acceptable lithium disilicate crown retention after long‐term aging with monthly thermocycling.

The authors included extracted molars which were prepared with flat occlusal, 20° taper, ~4 mm axial. The prepared teeth were assigned to two groups for equal mean surface areas per group. Lithium disilicate crowns were fabricated with the occlusal bar to facilitate removal. Crowns were etched with 9.5%HF and cleaned.

Cements included in the study were Ceramir Crown & Bridge QuikCap (CM) and Ketac Cem Maxicap (KC). Before cementation, specimens were stored in 37°C water. Crowns were cemented with 196 N force, placed in 37°C, 100% humidity oven for the setting. Specimens were then thermocycled (5–55°C) 5000 cycles monthly for 6 months; otherwise stored in phosphate-buffered saline solution. Crowns were removed axially at 0.5 mm/min. Removal forces recorded and stress calculated using areas. Independent t‐test (α = 0.05).

It was observed that CM removal stresses and forces (P < 0.001) were higher (1.93 MPa, 261.4 N) compared to KC (1.06 MPa, 139.4 N). CM cement found principally on crown intaglio, KC found with most cement on the prepared tooth. Chi‐square significant (P < 0.001).

Hence, the authors concluded that "following long‐term aging with monthly thermocycling, lithium disilicate crowns were best retained by CM cement, however, both types of cement are capable of retaining lithium disilicate crowns with preparations of ideal taper and length."

Without optimal axial length, the taper of preparation or retentive features, Ceramir Crown and Bridge QuikCap offers a bioactive cement with improved long‐term retention when compared to Ketac Cem Maxicap for lithium disilicate crowns, they further added.