Fracture load of zirconia implant supported CAD/CAM resin crowns and mechanical properties of restorative material and cement

Purpose: To test if resin CAD/CAM materials should be considered for zirconia implants and how their mechanical properties affect the fracture load. Methods: Fracture load of molar crowns of CAD/CAM materials (VITA CAD-Temp [CT], Cerasmart [CS], Lava Ultimate [LU], Pekkton Ivory [PK]) on zirconia implants (ceramic.implant, 4.0 mm) fixed either with no cement, temporary cement (Harvard Implant semi-permanent [HIS]), self-adhesive (VITA Adiva S-Cem [VAS]) or either one of two adhesive cements (Multilink Automix [MLA], VITA Adiva F-Cem [VAF]) was analyzed. The restorative materials were characterized by their flexural strength, fracture toughness, elemental composition and organic/inorganic ratio while compressive strength of the cements was measured. Results: For the fracture load significantly highest mean values were found overall for PK (2921 +/- 300 N) > LU (2017 +/- 499 N) > CS (1463 +/- 367 N) = CT (1451 +/- 327 N) (p > 0.05). When analyzing the effect of the cement on the fracture load the overall ranking was VAF (2245 +/- 650 N) >= MLA (2188 +/- 708 N) >= VAS (2017 +/- 563 N) > HIS (1757 +/- 668 N) = no cement (1595 +/- 757 N) (p <0.05), meaning fracture load increased with the compressive strength of the cements. Additionally, a linear trend was found between the fracture load and the fracture toughness of the restorative materials. Conclusions: All restorative materials exhibited fracture load values similar or higher than lithium disilicate tested previously. Fracture load of CT, CS and LU can be significantly increased when an adhesive cement with a high compressive strength is used.