Effect of silica coating and silanization on flexural and composite-resin bond strengths of zirconia posts: An in vitro study.
BACKGROUND
The bond strength of composite resin cores to the smooth surface of prefabricated zirconia-based ceramic posts is problematic because it might not be sufficient to ensure stability of the post-and-core system. It is also not clear whether any alteration of the post surface to provide additional mechanical or chemical retention would compromise flexural strength of the posts.


OBJECTIVE
This study tested the effect of a tribochemical treatment on the bond strength (BS) between zirconia-based ceramic posts and composite resin and on the flexural strength (FS) of the posts.


METHODS
For the BS test, 2 groups of specimens (n = 10) were prepared as follows: In the experimental (E) group, zirconia-based ceramic posts (Cosmopost), 21 mm long and 1.7 mm in diameter, were treated with a tribochemical silica coating and silanization system (Rocatec). For the control (C) group, zirconia-based ceramic posts were used as supplied by the manufacturer. For the 2 groups, posts were centered and vertically positioned in a metal mold, and composite resin (Tetric Ceram) was polymerized around the posts to form rings (6 mm diameter x 4 mm height). All specimens were positioned in a universal testing machine, and a load was applied axially on the protruding heads of posts in a shear push-out mode test until bond failure (MPa). Fracture mode was assessed as cohesive, cohesive/adhesive, or adhesive. Following this, the FS of the posts was measured in MPa using a 3-point bending test. Data were recorded and statistically analyzed using the Student t test for both tests (alpha = .01).


RESULTS
Mean fracture load values +/- SDs for the BS test were 28.1 +/- 2.3 MPa and 8.9 +/- 3.97 MPa for the E and C groups, respectively. The mean FS values were 1544.9 +/- 214.1 MPa and 844.8 +/- 50.8 MPa for the E and C groups, respectively. The tribochemically treated posts exhibited significantly higher values for both bond strength to composite resin and resistance to fracture when compared to posts in the control group (P < .001). Fracture analysis showed 100% cohesive/adhesive fractures for group E specimens and 100% adhesive fractures for group C specimens.


CONCLUSIONS
The use of a tribochemical silica coating process and silanization on zirconia-based ceramic posts increased both the bond strength to composite resin as well as the fracture strength of posts.
Xible
Anuar Antonio
AA
Department of Prosthodontics, Bauru Dental School, University of Sao Paulo, Brazil. axible@uol.com.br
de Jesus Tavarez
Rudys Rodolfo
RR
de Araujo
Carlos Dos Reis Pereira
Cdos R
Bonachela
Wellington Cardoso
WC
D000268:Adhesiveness; D002516:Ceramics / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D011176:Post and Core Technique / Q000295:instrumentation*; D012821:Silanes / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
D020099:Coated Materials, Biocompatible; D003188:Composite Resins; D003738:Dental Cements; C076811:Rocatec; D012821:Silanes; C121818:Tetric ceram; D012822:Silicon Dioxide; D015040:Zirconium; C028541:zirconium oxide