Effect of sandblasting, etching and resin bonding on the flexural strength/bonding of novel glass-ceramics

Objectives: To process novel leucite glass-ceramics and test the effects of surface treatment and resin bonding on the biaxial flexural strength (BFS) and shear bond strength (SBS). Methods: Alumino-silicate glasses were ball-milled, and heat treated to form leucite glass-ceramics (LG-C, OLG-C), then sintered into ingots. Ingots were heat extruded into a refractory mould to form disc specimens (1.3 x 14 mm diameter). IPS e.max (R) was used as a commercial comparison. Glass-ceramic test groups were sandblasted (Groups. 1, 4, 6), sandblasted, etched and adhesively bonded (Groups. 2, 5, 7) or lapped, etched and adhesively bonded (Groups. 3, 8). Specimens were adhesively bonded with Monobond S, followed by the application of Variolink II (R) cement and light curing. BFS testing was at 1 mm/min and SBS testing at 0.5 mm/min. Samples were characterised using XRD, SEM and profilometry. Results: XRD confirmed tetragonal leucite in LG-C/OLG-C and lithium disilicate/lithium orthophosphate in IPS e.max (R). Mean BFS (MPa (SD)) were: Gp1 LG-C; 193.1 (13.9), Gp2 LG-C; 217.7 (23.0), Gp3 LG-C; 273.6 (26.7), Gp4 OLG-C; 255.9 (31); Gp5 OLG-C; 288.6 (37.4), Gp6 IPS e.max (R); 258.6 (20.7), Gp7 IPS e.max (R); 322.3 (23.4) and Gp8 IPS e.max (R); 416.4 (52.6). The Median SBS (MPa) were Gp1 LG-C; 14.2, Gp2 LG-C (10s etch); 10.6 and Gp3 IPS e.max (R); 10.8. Mean surface roughness was 5-5.1 mu m (IPS e.max (R)) and 2.6 mu m (LG-C). Significance: Novel leucite glass-ceramics with reduced flaw size and fine microstructures produced enhanced BFS and SBS by resin bonding. These properties may be useful for the fabrication of minimally invasive aesthetic and fracture resistant restorations. Crown Copyright (C) 2018 Published by Elsevier Inc. on behalf of The Academy of Dental Materials. All rights reserved.