EVALUATION OF FRACTURE RESISTANCE AND FIT ACCURACY OF THREE TYPES OF CAD/CAM FABRICATED CROWNS USING CONE BEAM COMPUTERIZED TOMOGRAPHY

Aim: The aim of this study was to evaluate the internal and marginal fit accuracy using cone beam computerized tomography as an innovative nondestructive method and to assess the fracture resistance of the recently introduced zirconia reinforced lithium silicate glass ceramic in comparison to lithium disilicate and monolithic zirconia.
Materials and Methods: Three types of CAD/ CAM ceramic blocks were used; zirconia reinforced lithium silicate glass ceramics (Vita Suprinity), lithium disilicate glass ceramic (IPS e.max CAD) and partially sintered translucent zirconia (In-Coris TZI). A ceramic master die was fabricated and scanned using the Cerec Omnicam to produce a total number of 30 crowns, which were divided into 3 groups (n = 10) according to the ceramic material used . Group I: Vita Suprinity. Group II: IPS e.max CAD and Group III: In- Coris TZI. A highly computerized cone beam tomography (CBCT) was used to evaluate the fit accuracy of the crowns on the master die. For fracture resistance test, epoxy resin dies were optically scanned using Omnicam scanner and 30 crowns were fabricated using the CAD/ CAM ceramic materials (n = 10) for each tested material. The crowns were cemented using self-adhesive resin cement. A compressive load was applied at a cross head speed of 1mm/min and the fracture load in Newtons was recorded for each specimen. Fractured crowns were examined to determine the mode of fracture.
Results: Marginal and internal fit evaluation showed that group I (Vita Suprinity) recorded the least mean in respect to all measuring points (103.6±10.4μm), while group III (In Coris TZI) showed the highest mean in respect to all points (146.7±9.23μm). For fracture resistance, In Coris TZI zirconia showed the highest fracture load (4548.9±200.9 N), while the lowest mean value was recorded in Vita Suprinity (3484.8±22.17 N). There was no significant difference between Vita Suprinity and IPS e.max CAD.
Conclusion: Vita Suprinity crowns showed the best marginal and internal fit when compared to the other two materials. In- Coris TZI exhibited the highest fracture strength of all three groups. All values were within a clinically acceptable range for the three ceramic materials tested