Abstract
ObjectiveThis in vitro study aimed to evaluate the influence of different surface treatments, 3 luting agents and thermocycling on microtensile bond strength (µTBS) to zirconia ceramic. Material and MethodsA total of 18 blocks (5x5x4 mm) were fabricated from zirconia ceramic (ICE Zirkonia) and duplicated into composite blocks (Alphadent). Ceramic blocks were divided into 3 groups (n=6) according to the following surface treatments: airborne-particle abrasion (AA), silica-coating, (SC) (CoJet) and silica coating followed by silane application (SCSI) (ESPE Sil). Each group was divided into 3 subgroups (n=2) according to the 3 luting agents used. Resin-modified glass-ionomer cement (RMGIC, Ketac Cem Plus), self-adhesive resin cement (UN, RelyX Unicem) and adhesive resin cement (ML, MultiLink Automix) were used for bonding composite and zirconia blocks. Each bonding assembly was cut into microbars (10 mm long and 1±0.1 mm2). Seven specimens of each subgroup were stored in water bath at 37ºC for 1 week. The o ther 7 specimens were stored in water bath at 37ºC for 30 days then thermocycled (TC) for 7,500 cycles. µTBS values were recorded for each specimen using a universal testing machine. Statistical analyses were performed using a 3-way ANOVA model followed by serial 1-way ANOVAs. Comparison of means was performed with Tukey's HSD test at (α=0.05). ResultsµTBS ranged from 16.8 to 31.8 MPa after 1 week and from 7.3 to 16.4 MPa after 30 days of storage in water and thermocycling. Artificial aging significantly decreased µTBS (p<0.05). Considering surface treatment, SCSI significantly increased µTBS (p<0.05) compared to SC and AA. Resin cements (UN and ML) demonstrated significantly higher µTBS (p<0.05) compared to RMGIC cement. ConclusionsSilica coating followed by silane application together with adhesive resin cements significantly increased µTBS, while thermocycling significantly decreased µTBS.
Highlights
High mechanical properties, chemical stability, and biocompatibility make zirconia an attractive core material for fabrication of all-ceramic restorations . 4,7,15-19 Bonding techniques of allceramic restorations are dependent on chemical compositions of each ceramic system12 +\GURÀXRULF acid etching and silanization are mandatory steps to achieve a durable resin bonding to silica ceramics12
Zirconia ceramic blocks were ultrasonically cleaned in distilled water for 3 min and dried with oil-free air stream; Group 3 Silica coating and silane application (SCSI), same as Group SC followed by silane application26 (ESPE Sil, 3-methacryloxyprophyltrimethoxysilane in ethanol, 3M ESPE)
Mean ± standard deviation, minimum and maximum μTBS without and with thermocycling of test groups in MPa and P values are summarized in (Table 1). μTBS means were compared across all test groups using 3-way ANOVA model including the following factors
Summary
Chemical stability, and biocompatibility make zirconia an attractive core material for fabrication of all-ceramic restorations . 4,7,15-19 Bonding techniques of allceramic restorations are dependent on chemical compositions of each ceramic system12 +\GURÀXRULF acid etching and silanization are mandatory steps to achieve a durable resin bonding to silica ceramics. Zirconia ceramic blocks were ultrasonically cleaned in distilled water for 3 min and dried with oil-free air stream; Group 2: Silica coating (SC), airborneparticle abrasion using 50-μm Al2O3 particles at 0.28 MPa for 13 s at a distance of 10 mm followed by airborne-particle abrasion with 30-μm SiO particles (CoJet sand, 3M ESPE, Seefeld, Germany) at a pressure of 0.25 MPa for 20 s at a distance of 10 mm (Ney Blastmate II). Bonding zirconia and composite blocks Each main group was divided into 3 subgroups (n=2) according to the following 3 luting agents, Ketac Cem Plus, RelyX Unicem and MultiLink Automix. Equal amounts of adhesive resin cement were extruded, mixed for 20 s and applied to the intaglio surfaces of the zirconia ceramic blocks. AA: Air borne particle abrasion SC: Silica coating SCSI: Silica coating and silane application
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