JOURNAL OF PROSTHETIC DENTISTRY THE

Vol. 99 No. 5      May - 2008

ISSN: 0022-3913      UBIC: 171

RESUMEN

Statement of problem: Reliable bonding between zirconia posts and composite resin core materials is difficult to achieve because of the smooth surface texture and lack of silica content of zirconia posts. Purpose: The purpose of this study was to evaluate the effect of different surface treatments on the short-term bond strength and durability between a zirconia post and a composite resin core material. Material and methods: Eighty zirconia posts were divided into 4 groups (n=20). Specimens received 1 of4 different surface treatments: group AIRB, airborne-particle abrasion; group TSC-SIL, tribochemical silica coating (CoJet system) and silanization (ESPE Sil); group AIRB-BSIL, airborne-particle abrasion and MDP-containing primer (Clearfil SE Bond Primer)/silane coupling agent (Clearfil Porcelain Bond Activator) mixture application; and group TSC-BSIL, tribochemical silica coating and MDP-containing primer/silane coupling agent mixture application. Average surface roughness (Ra) of zirconia posts produced by airborne-particle abrasion or silica coating was measured using an optical profilometer. Composite resin core foundations (Build-it FR) were formed using transparent acrylic resin tubes (12 mm in length and 7 mm in diameter). Each group was further divided into 2 subgroups of 10 specimens and stored in distilled water at 37°C, either for 24 hours or for 150 days with 37,500 thermal cycles between 5°C and 55°C, with a dwell time of 3O seconds. Following water storage, the specimens were sectioned perpendicular to the bonded interface into 2-mm-thick post-and-core specimens under water cooling. Push-out tests were performed with a universal testing machine at a crosshead speed of0.5 mm/mi Debonded post surfaces were examined with SEM. Data were analyzed with 1- and 2-wayANOVA and Tukey multiple comparison tests (α=.05). Results: No significant differences were detected between the R values of airborne-particle-abraded and silica-coated specimens (P=.781 ). The short-term mean bond strengths for group TSC-BSIL (27.1 ±3.2 MPa) and TSC-SIL (25.2 ±2.4 MPa) were statistically higher (P<.001) than AIRB-BSIL (23.3 ±2.2 MPa). The relatively high bond strengths for groups TSC-BSIL and TSC-SIL decreased significantly after 150 days of water storage to 13.5 ±1.6 and 11.8 ±1.2 MPa, respectively (P<.001). Durable bonding was obtained only in group AIRB-BSIL (21.8 ±2.7 MPa), which was also the only group demonstrating predominantly cohesive failures in the core material after long-term water storage. Conclusions: Data suggest that the short-term high bond strength obtained with a silane coupling agent or MDP containing primer/silane coupling agent mixture to silica-coated zirconia posts was decreased with water storage and thermal cycling, whereas a durable bond could be obtained when an MDP-containing primer/silane coupling agent mixture was applied to the airborne-particle-abraded post surface. (J Prosthet Dent 2008;99:388-399)

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