Reduced contraction stress formation obtained by a two-step cementation procedure for fiber posts

Area of Science:

• Biomaterials Science
• Dental Materials Science
• Computational Mechanics

Background:

• A previous in vitro study demonstrated a 60% increase in push-out strength for fiber posts using a two-step cementation technique.
• This technique is analogous to the layering method used for composite restorations.

Purpose of the Study:

• To investigate the underlying reasons for the enhanced push-out strength observed with two-step cementation of fiber posts.
• To utilize finite element analysis (FEA) to understand the stress distribution and its impact on restoration integrity.

Main Methods:

• Finite element analysis (FEA) models were developed to simulate the push-out test setup for both one-step and two-step cementation procedures.
• Models included fiber posts cemented within a root canal, considering cement shrinkage and applied loads.
• Stresses were analyzed for the push-out test specimens and a complete root model.

Main Results:

• Despite a 60% higher load in the two-step model, the overall stresses were comparable to the one-step model.
• Cement shrinkage alone generated stresses in the complete root model that approached or surpassed the bond strength of resin cements to dentin.

Conclusions:

• FEA provides a rationale for the in vitro findings, explaining the increased push-out strength with two-step cementation.
• The two-step method reduces internal stresses within the fiber post restoration, leading to higher failure loads and potentially mitigating microleakage.