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Does overlay preparation design affect polymerization shrinkage stress distribution? A 3D FEA study.
Guilherme Schmitt de Andrade1, Alana Barbosa Alves Pinto1, João Paulo Mendes Tribst2
1Department of Dental Materials and Prosthodontics, Institute of Science and Technology, São Paulo State University (UNESP), São José dos Campos, Brazil.
Computer Methods in Biomechanics and Biomedical Engineering
|January 7, 2021
Summary
Non-retentive preparation (nRET) for indirect ceramic overlays significantly reduces polymerization shrinkage stress in the cement layer and abutment teeth compared to isthmus preparation (IST) and without isthmus preparation (wIST). This finding suggests nRET offers a more favorable stress distribution for dental restorations.
Area of Science:
- Dental Materials Science
- Biomaterials Engineering
- Computational Dentistry
Background:
- Polymerization shrinkage stress in dental cements can compromise the longevity of indirect ceramic restorations.
- Understanding the influence of tooth preparation design on stress distribution is crucial for optimizing restoration success.
Purpose of the Study:
- To evaluate and compare the polymerization shrinkage stress in three different tooth preparation designs for indirect ceramic overlays using finite element analysis.
- To determine which preparation design minimizes stress in the restoration, cement layer, and abutment teeth.
Main Methods:
- Finite element analysis (FEA) was employed to model three preparation designs: isthmus preparation (IST), without isthmus preparation (wIST), and non-retentive preparation (nRET).
- Digital impressions of prepared typodonts were used to create the models, assuming perfect bonding and homogeneous, linear, isotropic material properties.
- Polymerization shrinkage of a 100 µm cement layer was simulated, and maximum principal stress was evaluated.
Main Results:
- The highest stress peaks were observed in the restoration for IST (13.4 MPa) > wIST (9.3 MPa) > nRET (9 MPa).
- For the cement layer, stress followed IST (16.9 MPa) > wIST (12.6 MPa) > nRET (10-7.5 MPa), with nRET showing the most homogeneous distribution.
- Abutment teeth experienced the highest stress with IST (10.7 MPa) > wIST (10.5 MPa) > nRET (9 MPa), with IST concentrating stress at specific angles.
Conclusions:
- Non-retentive preparation (nRET) demonstrates the lowest polymerization shrinkage stress in the cement layer, leading to a more uniform stress distribution.
- The isthmus preparation (IST) design results in significantly higher shrinkage stress in both the cement layer and abutment teeth.
- Non-retentive preparation appears to be a superior design choice for minimizing polymerization shrinkage stress in indirect ceramic overlay restorations.
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