Diametral Tensile Strength and Knoop Hardness of Commercial Core Materials

Prefabricated nonmetallic posts are currently available for use in conjunction with resin composite cores, before fabrication of crowns, for endodontically treated teeth. These Core materials require superior mechanical properties to enable them withstand high functional stresses.

Objective: To evaluate the diametral tensile strength and Knoop hardness of five commercial cores materials.

Methods: Five commercial cores, RockCore (Danville Materials), CosmeCore (Cosmedent Inc), ParaCore (Coltene/Whaledent), MultiCore Flow (Ivoclar/Vivadent) and Filtek Supreme (3M/ESPE), were used. Disc specimens (6mm diameter and 2mm thick) were made and soaked in deionised water at 37șC for seven days prior to testing. The diametral tensile strength (DTS) (n=15) was evaluated using an Instron Universal testing machine (model # 3345) at a crosshead speed of 0.5mm/min. Knoop hardness (n=3) was conducted using a Buehler Hardness Tester. Five Knoop indentations were applied on each specimen with a total of fifteen indentations. Statistical analysis of the data was conducted using one way analysis of variance (ANOVA) and a Tukey B rank order test at p=0.05.

Results: The DTS of the five core materials Mean (SE) in MPa were 44.00±1.22 (CosmeCore), 41.07(0.68) (Paracore), 41.07±1.09 (Multicore), 40.50±1.98 MPa (Filtek Supreme) and 38.62±1.22 (RockCore). The Knoop hardness values were 69.87±2.73 (Filtek), 63.34±1.18 (CosmeCore), 47.56±2.18 (RockCore), 47.25±3.18 (ParaCore) and 46.74±2.15 (MultiCore).

Conclusions: The DTS values for the five core materials were not significantly different, p>0.05. Filtek Supreme and CosmeCore exhibited significantly higher Knoop hardness values than the rest of the core materials, p<0.05.