Wear Potential of Dental Ceramics and its Relationship with Microhardness and Coefficient of Friction.
OBJECTIVE
To evaluate, by means of pin-on-disk testing, the wear potential of different dental ceramic systems as it relates to friction parameters, surface finish, and microhardness.


METHODS
Three groups of different ceramic systems (Noritake EX3, Eris, Empress II) with 20 disks each (10 glazed, 10 polished) were used. Vickers microhardness (Hv) was determined with a 200-g load for 30 seconds. Friction coefficients (μ) were determined by pin-on-disk testing (5 N load, 600 seconds, and 120 rpm). Wear patterns were assessed by scanning electron microscopy (SEM). The results were analyzed using one-way ANOVA and Tukey's test, with the significance level set at α = 0.05.


RESULTS
The coefficients of friction were as follows: Noritake EX3 0.28 ± 0.12 (polished), 0.33 ± 0.08 (glazed); Empress II 0.38 ± 0.08 (polished), 0.45 ± 0.05 (glazed); Eris 0.49 ± 0.05 (polished), 0.49 ± 0.06 (glazed). Microhardness measurements were as follows: Noritake EX3 530.7 ± 8.7 (polished), 525.9 ± 6.2 (glazed); Empress II 534.1 ± 8 (polished), 534.7 ± 4.5 (glazed); Eris, 511.7 ± 6.5 (polished), 519.5 ± 4.1 (glazed). The polished and glazed Noritake EX3 and polished and glazed Eris specimens showed statistically different friction coefficients. SEM image analysis revealed more surface changes, such as small cracks and grains peeling off, in glazed ceramics.


CONCLUSIONS
Wear potential may be related to the coefficient of friction in Noritake ceramics, which had a lower coefficient than Eris ceramics. Within-group analysis showed no differences in polished or glazed specimens. The differences observed were not associated with microhardness.
School of Dentistry, Universidade Luterana do Brasil (ULBRA), Canoas, Brazil.
Rafael Augusto
RA
Freddo
Department of Conservative Dentistry, School of Dentistry, Universidade Federal do Rio Grande do Sul (UFGRS), Porto Alegre, Brazil. mpkapczinski@uol.com.br.
Myriam Pereira
MP
Kapczinski
Exact Sciences and Engineering, Universidade Estadual do Rio Grande do Sul (UERGS), Novo Hamburgo, Brazil.
Eder Julio
EJ
Kinast
Department of Conservative Dentistry, School of Dentistry, Universidade Federal do Rio Grande do Sul (UFGRS), Porto Alegre, Brazil.
Oswaldo Baptista
OB
de Souza Junior
School of Dentistry, Universidade Luterana do Brasil (ULBRA), Canoas, Brazil.
Elken Gomes
EG
Rivaldo
Department of Conservative Dentistry, School of Dentistry, Universidade Federal do Rio Grande do Sul (UFGRS), Porto Alegre, Brazil.
Luis Carlos
LC
da Fontoura Frasca
D002516:Ceramics; D003775:Dental Polishing; D003776:Dental Porcelain; D017276:Friction; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties
D003776:Dental Porcelain
Dental materials; friction; hardness; pin-on-disk