Category: Laboratory Research
Award Category: Junior Scientist
Importance of Simulating Polymerization Shrinkage of Materials in Finite Element Models
Canan Özcana* (canan.ozcan@univ-reims.fr) | Philippe Lestrieza | Yannick Josseta
aFaculty of Odontology, MATIM, University of Reims Champagne-Ardenne, Reims, France
Objective: This study compared the effect of composite onlay restoration design bonded with different adhesive thickness, with or without omission of polymerization shrinkage of materials, on the Von Mises stress distribution during the chewing stage.
Methods: The analysis used a finite element model of 17 and 47 built from a patient CBCT acquisition and charged with his mandibular motion recorded with Modjaw system. Three groups were constructed. Group A- Reference group. Group B- The adhesive had a greater thickness (0.25 instead of 0.1 mm). Group C- The onlay had a greater depth (2.5 instead of 1.5 mm). In each group, a thermal analogy was used for a numerical simulation of the polymerization shrinkage of adhesive layer and composite for one model, and it was omitted for the other one model. The Von Mises stresses on each structure were measured in the maximum occlusion phase of the chewing stage.
Results: The greatest stresses were measured in the composite under the contact points with the opposing tooth and in the group with the deepest restoration (218 MPa). With the simulation of polymerization shrinkage, the stresses observed on the enamel were 3 to 4.4 times higher (155 MPa) and localized on the proximal zones where the thickness of the material was the lowest. For dentin, stress values were doubled for groups B and C and 5.5 times greater for the reference group (77 MPa). Their location was on the external part of the proximal angles of the cavity. The pulp also presented stresses twice as high despite values remaining very low (0.0028 MPa).
Conclusion: The proximal edges of the restorations were a stress concentration zone. These stresses were induced by the polymerization shrinkage of the materials, which cannot be omitted from the finite element simulation. Without this simulation, the only significant stresses were observed under the contact points with the antagonist tooth and were supported by the composite restoration.
Funding/Conflict of Interest: None
Keywords: finite element analysis, mechanical Stress, motion, onlay, polymerization, restoration
