Mechanical properties and repair bond strength of polymer-based CAD/CAM restorative materials
International Journal of Applied Ceramic Technology. 2021;18(2):312-318.
ABSTRACT
Information on the mechanical properties and repairability of computer-aided design/computer-aided manufacturing (CAD/CAM) blocks is scarce. Five CAD/CAM blocks with similar indications were evaluated, including four resin nanoceramics, one polymer-infiltrated ceramic network (PICN), and one feldspathic ceramic. CAD/CAM blocks were sectioned into 4 mm × 1.2 mm × 13 mm bars for flexural strength (FS), and 4 mm thick blocks were prepared for elastic modulus (EM), nanohardness (NH), and microshear bond strength (µSBS) testing. FS of the CAD/CAM blocks was determined using a three-point bending test, whereas EM and NH values were measured using a nanoindenter. The reparability of the tested block materials was determined by the µSBS test. One-way ANOVA was conducted for FS, EM, NH, and µSBS followed by Tukey's pairwise comparison (α < 0.05). FS ranged from 115 to 207 MPa, EM from 8.21 to 44 GPa, NH from 0.76 to 7.24, and µSBS from 24.9 to 30.6 MPa. The findings of the present study revealed that resin nanoceramic blocks exhibited higher FS values than PICN and feldspathic ceramic, and they have acceptable mechanical properties for the fabrication of single-unit restorations according to the ISO 6872:2008. Furthermore, all CAD/CAM blocks tested can be successfully repaired regarding their recommended repair protocol.
KEYWORDS
CAD/CAM · dentistry · elastic modulus · flexural strength · microshear bond strength · nanohardness
STUDY SUMMARY
This in vitro study measured flexural strength, elastic modulus, nanohardness and repair bond strength for six CAD/CAM blocks comprising resin nanoceramics, a polymer-infiltrated ceramic network and a feldspathic ceramic. Flexural strength ranged from 115 to 207 MPa, elastic modulus from 8.21 to 44 GPa and repair bond strength from 24.9 to 30.6 MPa, with the resin nanoceramic blocks showing higher flexural strength than the other two material types. All blocks met the ISO 6872:2008 requirement for single-unit restorations and could be repaired following their recommended protocol under laboratory conditions.