The Influence of Cement Spacer Thickness on Retentive Strength of Monolithic Zirconia Crowns Cemented with Different Luting Agents (A Comparative in-vitro Study)
Keywords:cement space, monolithic zirconia, resin-cement, retentive strength, RMGIC.
Aims of Study: to evaluate and compare the retentive strength and the failure-modes of monolithic zirconia
crowns with different cement spacer thickness, cemented with two different types of luting agents.
Materials and Methods: Forty sound maxillary first premolar teeth were divided into two main groups
(n=20): Group A: cement spacer thickness of 80?m; Group B: cement spacer thickness of 120?m. The
groups were further subdivided into two subgroups (n=10): (A1, B1) cemented with Panavia F2.0 resincement; (A2, B2) cemented with Riva luting plus RMGIC. All the teeth were prepared to receive monolithic
zirconia crowns with the following features: (6º convergence angle, 0.8mm deep chamfer finishing line,
4mm axial wall height with planar occlusal reduction). Afterwards, the teeth were scanned and the crowns
were fabricated and cemented. Zirconia crowns were pulled-out along its path of insertion using universal
testing machine. Failure stresses were calculated in MPa. Failure-modes was assessed using magnifyinglens (2.5X).
Results: The highest mean retentive values (in Mpa) was recorded by subgroup B1 (8.651); followed by
subgroup B2 (7.765); subgroup A1 (7.309) and subgroup A2 (6.875). Independent t-test showed a statistically
significant difference between A1 and B1 subgroups. Concerning the failure-mode, the majority of samples
revealed adhesive failure between teeth and cement.
Conclusion: All the tested crowns have mean retentive values within the clinically acceptable limit,
increasing cement space resulted in a significant increase in the retention when Panavia F2.0 used as a luting
agent, while, it has no significant effect on the retention when RIVA luting plus was used.
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