Ebrahim Maghami1, Ehsan Homaei2, Khalil Farhangdoost3, Edmond Ho Nang Pow4, Jukka Pekka Matinlinna5, James Kit-Hon Tsoi6. 1. Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran. 2. Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran; Toos Dental Lab- Sahebkar, Mashhad, Iran; Dental Materials Science, Discipline of Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. 3. Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran. Electronic address: farhang@um.ac.ir. 4. Oral Rehabilitation, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. 5. Dental Materials Science, Discipline of Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. 6. Dental Materials Science, Discipline of Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. Electronic address: jkhtsoi@hku.hk.
Abstract
PURPOSE: The aim of this study was to investigate and quantify the effect of preparation design parameters on a premolar restored with two different CAD/CAM ceramic crowns by three-dimensional finite element analysis (FEA). METHODS: A restored human first premolar was digitized by a micro-CT scanner and a 3D model was created by a medical image processing software (Mimics). Following segmentation, dentine and ceramic were extracted by a surface meshing software (3-matic). Models with different preparation designs with three convergence angles (6°, 12° and 20°) and two preparation heights (3.1mm and 4.1mm) were produced. Mesh generation for models was performed in IA-FEMesh software with a lithium disilicate glass ceramic (LD, E=95.9GPa) and a polymer-infiltrated ceramic (PIC, E=30.1GPa) as the restorative materials. A 5-mm diameter stainless steel hemisphere was employed as an indenter. Twelve models were analyzed numerically in Abaqus™. RESULTS: The results indicated that preparation height was found to be a major factor affecting stress distribution in different components. In all models, the maximum principal stress of the ceramic crowns was found in contact area against the indenter. This stress was lesser in the longer abutment than the shorter one and it was greater for LD ceramic. Convergence angle had limited effect on stress distribution of ceramic crown in all models. CONCLUSIONS: The preparation height appeared to play a more important role in the stress distribution of ceramic crown than the convergence angle.
PURPOSE: The aim of this study was to investigate and quantify the effect of preparation design parameters on a premolar restored with two different CAD/CAM ceramic crowns by three-dimensional finite element analysis (FEA). METHODS: A restored human first premolar was digitized by a micro-CT scanner and a 3D model was created by a medical image processing software (Mimics). Following segmentation, dentine and ceramic were extracted by a surface meshing software (3-matic). Models with different preparation designs with three convergence angles (6°, 12° and 20°) and two preparation heights (3.1mm and 4.1mm) were produced. Mesh generation for models was performed in IA-FEMesh software with a lithium disilicate glass ceramic (LD, E=95.9GPa) and a polymer-infiltrated ceramic (PIC, E=30.1GPa) as the restorative materials. A 5-mm diameter stainless steel hemisphere was employed as an indenter. Twelve models were analyzed numerically in Abaqus™. RESULTS: The results indicated that preparation height was found to be a major factor affecting stress distribution in different components. In all models, the maximum principal stress of the ceramic crowns was found in contact area against the indenter. This stress was lesser in the longer abutment than the shorter one and it was greater for LD ceramic. Convergence angle had limited effect on stress distribution of ceramic crown in all models. CONCLUSIONS: The preparation height appeared to play a more important role in the stress distribution of ceramic crown than the convergence angle.