Stress State of Bonded ‘Restorations' after Shrinkage and Mechanical Loading

Objectives: The aim of this study was to investigate if the stresses provoked by the shrinkage at the interface on different cavity walls are affected as a function of the C-Factor.

Methods: Three-dimmension finite element models of a restored Class I ‘cavity' were performed by MSC.PATRAN/MSC.Marc®, submmiting to a shrinkage of 1% and/or mechanical loading, which was concentrated or uniformly distributed at the restoration occlusal area. Von Mises (VM), maximum principal (MP) and maximum shear (MS) stresses peaks from the different walls were carried out on graphics as a function of the C-Factor.

Results: There was no association between the stresses peaks and the C-Factor and the pulpal wall has presented the lowest peaks. From the shrinkage data MP and MC appears to be coincidents when the axial walls were similar, but higher were the stresses at the smaller wall for the other cases, except for C-Factor 5.4. From the uniform loading data, the axial walls have presented similar peaks, excepts for the C-Factor 5.4 and 13.5, which have presented strict restored occlusal area. From the concentrated loading data, MC were higher than MP and the lowest peaks have occured at the pulpal wall for the highest depth cases and the lowest depth with the highest restored oclusal area. From the highest strict restored occlusal area cases (C-Factor 5.4 and 13.5), greater was the wall greater was MC. The cavities which correspond to C-Factor 2.2 and 5.4 have presented the lowest peaks for the smaller walls. When loading was applied with shrinkage simultaneously, some cases presented increasing (C-Factor 3.8) or decreasing (C-Factor 4.6 and 1.9) on stress or sometimes this condition appears not affect them(Fator C 2,2 e 5,4).

Conclusion: No correlation between the C-Factor and the stresses developed at restored cavities interface after skrinkage and/or mechanical loading was found.