Effect of environmental conditions on wear resistance of lithium silicate glass-ceramic materials

To compare the impact of neutral and acidic environments on wear resistance of lithium silicate glass-ceramics (LSGCs), with and without crystallization firing after manufacturing.

Fifty-six specimens were tested in a two-body wear simulator and divided into seven groups. Four groups consisted of commercially available LSGC materials, each opposed to steatite antagonists. A fifth group included an LSGC material tested additionally in its fired state. A sixth group involved another LSGC material opposed to zirconia antagonists. A seventh group comprised zirconia specimens, opposed to steatite antagonists. All specimens underwent a two-body wear test with 250,000 cycles, a 5 kg load, and 1 mm lateral movement, while immersed in either neutral (pH 7) or acidic (pH 3) buffer solutions. Laser scanning microscopy, optical profilometry, and scanning electron microscopy were used to quantify and/or investigate the wear. Data were analyzed using one-way ANOVA.

LSGC materials exhibited significantly higher wear at pH 7 compared to pH 3 (p < 0.001). The greatest volume loss was observed in an unfired LSGC material (0.138 ± 0.039 mm³ at pH 3 vs. 0.495 ± 0.092 mm³ at pH 7). Steatite antagonists also suffered significantly greater wear at pH 7, with the highest antagonist wear recorded at 1.718 ± 0.068 mm³ . The wear mechanism caused by steatite antagonists differed from zirconia antagonists.

Environmental conditions play a major role in the wear performance of LSGCs. Fully crystallized LSGC materials show similar susceptibility to environmental changes compared to LSGC materials requiring crystallization firing.