Effect of two Preparation Designs and Methods of Construction on the Fracture Resistance of Glass Ceramics Laminate Veneers

Document Type : Original Article

Authors

1 Dentist at the Ministry of Health

2 Professor, Department of Crown and Bridge, Faculty of Dental Medicine, Boys, Cairo, Al-Azhar University

3 Lecturer, Department of Crown and Bridge, Faculty of Dental Medicine, Boys, Cairo, Al-Azhar University

Abstract

Purpose: To evaluate the effect of marginal finish line design and fabrication techniques on the fracture resistance of lithium disilicate laminate veneer. Materials and methods: A total of 24 veneers were designed, constructed, and divided into two main groups according to preparation design Chamfer 0.3 mm finish line (n=12) and, Chisel finish line (n=12). Each group was then divided into two subgroups according to the technique of veneer construction, veneers constructed by (CAD/CAM system) out of e max CAD blocks (n=6), and veneers constructed by (press on technology) using e max press ingots (n=6). then the veneers bonded to corresponding epoxy resin dies using resin cement. Finally fracture resistance test was done for all specimens using universal testing machine. Results: The highest fracture resistance values were recorded in the group of chisel marginal design fabricated by CAD/CAM technique. The lowest fracture resistance values were recorded in the group of 0.3mm chamfer margin design fabricated by Press technique. Regardless to margin design there was a significant difference between both processing techniques as indicated by two-way ANOVA test (p=0.0178<0.05) where (CAD/CAM >Press). Irrespective of material type it was found that margin design significantly influenced mean as indicated by two-way ANOVA test (p=0.0001<0.05) where (Chisel ≥ Chamfer). It was found that the Chisel margin design recorded statistically non-significant values between CAD/CAM group (302.64±46.91N) and Press group (297.37±56.5N) as indicated by unpaired t-test (P=0.8892>0.05). It was found that the Chamfer margin design recorded statistically significant higher fracture resistance mean value with CAD/CAM group (245.85±56.37N) than Press group (129.71±19.49 N) as indicated by unpaired t-test (P=0.002<0.05) Conclusions: The technique of fabrication of ceramic laminate veneer restorations has a crucial effect on its performance with the regard to fracture resistance. IPS e.max CAD could be considered as a valid restoration than IPS e.max press.

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