Title : Comparative evaluation of fracture resistance and internal fit of endocrowns using lithium disilicate and polyether ether ketone materials - an in vitro study
Statement of the problem: An end crown is a novel type of onlay. Nevertheless, dentists have not still fully understand the clinical implications of the selection of end crown material. Inherited brittleness of etchable ceramics containing glass is claimed to be the major limitation of these materials as it leads to catastrophic fracture and excessive wear on opposing natural teeth. To overcome this problem the use of material that has the potential of stress distribution as PEEK. Yet clinical studies are needed to evaluate their mechanical properties and clinical performance.
Purpose: This study compared the fracture strength and the internal fit of PEEK end crowns to that of lithium disilicate end crowns with different occlusal preparation designs.
Materials and methods: 32 end crowns were fabricated on prepared mandibular molars and divided into 2 main groups (N=16) according to the material. Group A: lithium disilicate end crowns and Group B: PEEK end crowns. Each group was further subdivided into 2 subgroups (N=8) according to the occlusal preparation design (full occlusal coverage and partial occlusal coverage end crowns). Samples were evaluated using µCT imaging with a voxel size of 6 µm to evaluate internal fit and a universal testing machine was used to evaluate fracture resistance. Data were collected, tabulated, and statistically analyzed using commercially available software (SPSS Chicago, IL, USA). Numerical data were described as mean and standard deviation and compared using the ANOVA test. The level of significance was set at P≤0.05.
Results: PEEK end crowns showed remarkable results compared to lithium disilicates endocrownsin.
Clinical significance: evaluation of mechanical properties and clinical performance of PEEK end crowns as an alternative restorative material to overcome the limitations of widely used etchable glass ceramics in the restoration of endodontically treated teeth.