Influence of surface finishing on fracture load and failure mode of glass ceramic crowns.
BACKGROUND
Ceramic restorations often require adjustments using diamond rotary instruments, which damage the glazed surface. The effect of these adjustments on the fracture behavior of these restorations is unclear.


OBJECTIVE
The purpose of this in vitro study was to evaluate the influence of induced surface defects on the fracture load and mode of failure of lithium disilicate-based (LDS) glass ceramic restorations.


METHODS
Premolar crowns were obtained from LDS computer-aided design and computer-aided manufacturing blocks (n=60) and glazed. The crowns were bonded to dentin analog dies and divided into 5 groups (n=12), as follows: glaze; abrasion (diamond rotary instrument 2135); abrasion and reglaze; abrasion and polishing (diamond rotary instrument 2135F, 2135 FF, and polishing devices); and polishing. The topography of the crowns was examined by scanning electron microscopy, and roughness was measured. A compressive load (0.5 mm/min) was applied by a piston to the center of the lingual cusp until fracture. The fracture load was recorded and data were statistically analyzed by ANOVA and the Tukey HSD test (α=.05). Fractured crowns were examined to determine the fracture origin.


RESULTS
Polishing and/or reglazing resulted in lower roughness than for the abraded group (P<.05), which did not affect the fracture loads (P=.696). Catastrophic fracture with origin at the intaglio surface was the mode of failure for all the crowns.


CONCLUSIONS
The experiment design successfully submitted the crowns to a clinical stress state, resulting in a clinically relevant failure. Reglazing or polishing were effective in reducing surface defects. Surface treatments had no effect on the immediate catastrophic failure of LDS crowns.
Predoctoral student, Post-Graduation Program in Dentistry, Dental School, University of Passo Fundo, Rio Grande do Sul, Brazil.
Rafael Tagliari
RT
Mores
Professor, Post-Graduation Program in Dentistry, Dental School, University of Passo Fundo, Rio Grande do Sul, Brazil.
Márcia
M
Borba
Professor, Post-Graduation Program in Dentistry, Dental School, University of Passo Fundo, Rio Grande do Sul, Brazil.
Pedro Henrique
PH
Corazza
Senior Professor, Post-Graduation Program in Dentistry and Dean, Dental School, University of Passo Fundo, Rio Grande do Sul, Brazil.
Álvaro
Á
Della Bona
Professor, Post-Graduation Program in Dentistry, Dental School, University of Passo Fundo, Rio Grande do Sul, Brazil. Electronic address: benetti.paula@gmail.com.
Paula
P
Benetti
D002516:Ceramics; D003442:Crowns; D003764:Dental Materials; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D013499:Surface Properties
D003764:Dental Materials; C493120:lithia disilicate; D003776:Dental Porcelain; C023506:Glass ceramics