Mechanical Cycling in Ultra-thin Occlusal Restorations By Lithium Disilicate

Objectives: To evaluate the mechanical cycling of ultrafine occlusal veneers restorations made by two lithium disilicate glass-ceramic press systems (LD). Additionally, the ceramic occlusal wear pattern was compared.

Methods: Sixteen human upper premolars (n=8) were collected and randomly assigned to 2 groups according to LD used: IPS e.max Press (Ivoclar Vivadent) and GC Initial LiSi Press (GC Co.). All specimens received a 0.5 mm-depth bur-preparation on occlusal surface. Specimens were submitted to erosive process simulation and ultra-thin occlusal LD restorations with a thickness of 0.5 mm were made. The specimens were positioned on a loading machine (Chewing Simulator CS-4- SD Mechatronik), submitted to mastication simulator for 250,000 cycles with a constant load of 100 N, and a frequency of 1.6 Hz. After loading, ceramic/tooth fracture surviving and the ceramic occlusal wear pattern were classified with a 1-to-5 severity score using standardized 120-mm macro (Nikon Medical Lens and D5300) photographs and under a scanning electron microscopy (JSM-6390LV, JEOL, EUA). Median resistance to fracture scores and occlusal wear pattern were analyzed using Mann-Whitney test and Shapiro-Wilk test. Fisher exact test was used to verify association between LD and the occlusal presence of failure (significance level of 5%).

Results: The medians (1-to-5 score) failure scores were: IPS e.max Press = 3.00, and GC Initial LiSi Press = 3.00. The medians ceramic occlusal wear pattern scores were: IPS e.max Press = 3.00, and GC Initial LiSi Press = 3.50. There was no statistically significant difference between the groups regarding the type of fracture (p= 0.265), and ceramic occlusal wear pattern (p= 0.569).


Conclusions: Ultra-thin occlusal restorations made by two lithium disilicate glass-ceramic press systems presented limited performance after mechanical cycling in upper premolars.