Shear bond strength of different cements to printed resins and zirconia

Abstract

OBJECTIVES: This in-vitro study aimed to measure bonding of multi and single step cements to printed resins and Layzir zirconia. Evaluate the effect of different material combinations on shear bond strength, and to evaluate the effect of thermocycling on shear bond strength of different materials combinations. MATERIALS AND METHODS: Rectangular specimens (N= 384) were prepared from PacDent Rodin Sculpture 2.0 (RS), SprintRay Ceramic Crown (SCC), Rodin Titan (RT), and Layzir Zirconia (LZ), and were divided into 16 groups according to material combinations, static or thermal aging process. Stainless-steel rods (Shofu Dental Corporation) of 4 mm diameter were used for this in-vitro study. Shear bond strength (SBS) test was performed on all static and thermocycled groups. The final dimension of each plate was about 15 mm in length, 2mm thick, and 15 mm in width. 3D printing of resins was done using the Asiga 3D printer. Layzir Zirconia specimens were prepared by sectioning the zirconia disc using the Isomet 5000 sectioning machine. Zirconia specimens were dried in the oven and sintered using a high temperature furnace (Zircar). All materials were surface treated based on material recommendations. All stainless-steel rods and Layzir Zirconia were sandblasted, PacDent Rodin Sculpture 2.0 and Rodin Titan were etched with hydrofluoric acid 5%, and SprintRay Ceramic Crown was sandblasted and etched using 5% Hydrofluoric acid. In the last stage of specimen preparation, the framework plate was placed on a flat surface, then the adhesive resin cement was injected to fill the bonding area. Excess cement was removed around the rod border with a plastic instrument and a micro brush, and the bonded plate/rod was kept under a static load of 1.4 kg for 10 minutes. Half of the specimens were tested in a control/static condition, and another half were thermal aged for 5000 cycles before shear bond testing was done. A shear bond test was performed on all static and thermocycled specimens by using the universal testing machine (Instron Model 5566A). The crown material was secured into a jig and a flat shear blade was used to shear the pins. The blade had a perpendicular contact at the interface between the rod and the plate. A load was applied at the adhesive interface between the plate/rod during the testing. The shear bond strength was calculated in MPa by load of failure over the area of the bond. The maximum shear load was recorded at debonding. Specimens were examined to determine failure location, load to failures values were also analyzed as well as the mode of failures. RESULTS: This study showed a significant difference in shear bond strength between the printed resin groups compared to Layzir Zirconia group (P<.0002). Layzir Zirconia group showed the lowest SBS mean values among the tested groups (16.18 MPa). SprintRay bonded with Panavia SA materials produced the highest shear bond strength mean values (32.07MPa), followed by Rodin Titan bonded with Panavia V5 and Clearfil (30.91MPa) and Panavia SA (29.50 MPa), and PacDent Rodin Sculpture 2.0 Bonded with Panavia SA (25.51 MPa). The lowest shear bond strength mean values were recorded in SprintRay bonded with Clearfil and Panavia V5 (17.26 MPa), Layzir Zirconia bonded with Rodin bond and Panavia V5 (15.06 MPa), and Pacdent Sculpture 2 bonded with Clearfil and Panavia V5 (13.62 MPa). There was a significant difference in SBS between control and treated (thermal cycle) groups (decrease in treated group than control group) (P<.0001). There’s a significant difference between SBS values for specimens bonded with Panavia SA compared to other resin cements used (P<.0001). CONCLUSION: Significant differences were found between 3D printed resins compared to Layzir Zirconia groups. Layzir Zirconia groups showed the lowest SBS among all tested groups. Thermal aging significantly decreased SBS values of thermocycled groups. Adhesive failure was the primary mode of failure among all SBS tested groups. Material surface topography, filler content, surface pretreatment and adhesive techniques, as well as thermal aging impact the bonding and as a result SBS values of specimens.