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The effect of occlusal reduction and different CAD/CAM materials on stress distribution in endocrown restorations: A 3D finite element analysis

Aim: The aim of this study was to examine the effects of different preparation types and restorative materials on the endocrown restoration applied to endodontically treated maxillary first molar and the stress distribution on the related tissues.
Methodology: A 3-dimensional (3D) image of a previously extracted intact tooth was obtained with CBCT. The resulting .dicom files were imported into the Mimics. Enamel, dentine and pulp were separated and extracted as an STL file. 4 different groups were determined and prepared in SolidWorks. The 3D images were imported into the relevant finite element analysis software (ABAQUS), and a load of 600 N was applied at the occlusal area of each model in the axial direction. Models are divided into 3 groups according to material type: Vita Suprinity (VS; VITA Zahnfabrik), Cerasmart (CS; GC Corp.), and Shofu Block HC (SB; Shofu). There is also a type of cement is used: RelyX ARC (3M ESPE).
Results: Regardless of the results, any stresses on any tissue or restoration were not above the strength limits. In models with cusp preparation, the stress on the dental tissues was lower. In addition, higher stress was generally observed in groups where the lingual area was healthy. On the other hand, the stress occurring in zirconia-reinforced glass ceramics (VS) is higher compared to ceramic materials with a resin matrix (CS, SB). It has been determined that the stress transmitted to the supporting tissues is lower.
Conclusion: As a result, endocrown restorations can be used in the restoration of endodontically treated first molars. In addition, when endocrown restoration is applied to molars with only one healthy area and excessive loss of coronal structure, reducing the cusp will be beneficial in terms of the distribution of stress on the healthy tissues. 