Assessment of Bioactive Resin-modified Glass Ionomer Restorative as a New CAD/CAM Material Part II: Fracture Strength Study
The objective of this in vitro study was to evaluate and compare the fracture strength of monolithic crowns fabricated from a newly-developed bioactive CAD/CAM resin block and reinforced resin CAD/CAM block with two types of resin cement (adhesive and self-adhesive cement). Bioactive CAD/CAM blocks were fabricated from ACTIVA BioACTIVE-RESTORATIVE (PULPDENT Corporation, USA). Thirty-two human maxillary first premolar teeth were prepared to receive full crowns and then divided into two main groups of 16 teeth each according to the block type that used: Group A: crowns fabricated from the bioactive resin block, Group B: crowns fabricated from reinforced composite block (BRILLIANT Crios, COLTENE). Each group was then subdivided into two subgroups according to the type of resin cement used for cementation: Subgroups (A1, B1): RelyX Ultimate cement, Subgroups (A2, B2): ACTIVA BioACTIVE-cement. The prepared teeth were then scanned using CEREC Omnicam digital intra-oral scanner and crowns were designed using Sirona InLab (version 15.1) and milled using InLab MC XL milling unit. Each crown was cemented on its respective tooth according to manufacturer’s instructions of each cement. All cemented crowns were subjected to compressive axial loading in computer-controlled universal testing machine (LARYEE, China) at crosshead speed of 0.5 mm/ min until fracture occurred. The data were statistically analyzed using student’s t-test at a level of significance of 0.05. The results of this study showed no statistically significant differences between the mean values of fracture strength of both block types with each cement type. Meanwhile, blocks cemented with adhesive cement showed higher mean values of fracture strength than those cemented with the self-adhesive cement with statically highly significant differences. From the results of this study, it could be concluded that the newly-developed bioactive CAD/CAM block can be used clinically as monolithic crowns in the premolar area as the mean values of fracture strength of crowns fabricated from these blocks surpassed the maximum biting force in a premolar area irrespective of cement type.