Comparison of Fracture Resistance and Bond Strength of e.max Crowns Restored with Fiber Post and Core with ENDO Crowns

Objective: This study evaluated the Fracture Resistance and Bond strength of e.max crowns made with CAD/CAM technology on teeth restored with fiber post and core and compare them to Endo crowns. Materials and Methods: 32 extracted premolars were collected from the department of periodontics and oral surgery. These teeth were assigned in 2 groups. 16 teeth were assigned to test compressive load resistance and the other 16 were assigned to test tensile strength. These groups were subdivided into 2 groups. One group with 8 teeth received post and core followed by crown placement and the other group of teeth were prepared to receive Endo crown. After teeth preparation, samples were scanned and e.max crowns were milled. These crowns were then bonded using resin cement. Cyclic loading was done before testing for fracture resistance or bond strength. Mode of failure was also observed for all groups. Results To compare differences for the outcome measure tensile strength and compressive force two Welch ANOVA models were created. The mean compressive force required for conventional and Endo crowns were 737.9 N and 410.9 N respectively. The mean tensile force required for conventional and Endo crowns were 166.4 N and 205.4 N respectively. There was a significant difference in the measurement of bond strength and fracture resistance by group Discussion In our study we found that conventional crowns needed more compressive force for dislodgement/breaking compared to Endo crowns. Additionally, we found that Endo crowns required more tensile force for dislodgement/breakage when compared to conventional crowns. When mode of failure was observed for fracture resistance, the tooth fractured 100% of the time for Endo crowns compared to 75% of the time for conventional crowns. During Tensile testing, fracture of the restoration was seen 75% for Endo crowns, and debonding was the most common failure (87.5%) for conventional crowns. Conclusion This study concluded that Endo crowns have higher bond strength compared to conventional crowns. However, they have a reduced fracture resistance compared to conventional crowns