Ahmed Attia

Influence of surface conditioning and cleaning methods on resin bonding to zirconia ceramic

OBJECTIVES The purpose of this laboratory study was to evaluate the influence of different surface conditioning, new ceramic primers and cleaning methods on the bond strength of luting resin to zirconia ceramic (e.max ZirCAD). METHODS A total of 96 zirconia ceramic discs were divided into six groups (n=16) according to surface conditioning, cleaning methods and ceramic primers. Zirconia ceramic discs were either air-abraded with 110 μm alumina particles or tribochemically silica-coated (Rocatec). Visible dust resulting from air-borne particle abrasion or silica coating was removed either by oil-free air stream or by ultrasonic cleaning in alcohol. Then either a conventional silane (Espe Sil) or a universal primer containing a silane and a phosphate monomer (Monobond Plus) were applied to the conditioned surface. Transparent plastic tubes filled with composite resin were bonded to the zirconia ceramic discs using a luting resin (MultiLink Automix). The bonded specimens were stored in water at 37°C for 3 days and for 30 days with 7500 thermal cycles between 5°C and 55°C prior to tensile test. Statistical analyses were conducted with three-, two- and one-way ANOVAs followed by comparison of means with Tukeys HSD test. RESULTS Tensile bond strength ranged from 31.5 to 45.2 MPa after 3 days and from 10.6 to 38.8 MPa after 30 days storage in water with thermal cycling. After artificial aging the decrease in bond strength was significant when the conventional silane was applied after silica coating or when the universal primer was used after air-borne particle abrasion without ultrasonic cleaning (P<.05). However after artificial aging, the decrease in bond strength was not significant (P>.05) when the universal primer was used after air-borne particle abrasion with ultrasonic cleaning or after silica coating. SIGNIFICANCE A new universal primer improved bonding to zirconia ceramic while the cleaning method had little or no effect.

Bond strength of three luting agents to zirconia ceramic - influence of surface treatment and thermocycling.

Objective This 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 Methods A 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 Tukeys HSD test at (α=0.05). Results µTBS 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. Conclusions Silica coating followed by silane application together with adhesive resin cements significantly increased µTBS, while thermocycling significantly decreased µTBS.

Long-term resin bonding to zirconia ceramic with a new universal primer

STATEMENT OF PROBLEM Different surface conditioning, cleaning methods, and ceramic primers are used to improve bonding to zirconia ceramic. However, maintaining a durable bond with zirconia ceramic under various clinical conditions remains a challenge. PURPOSE This in vitro study investigated the durability of the bond strength of adhesive luting cement to zirconia ceramic after the application of a new universal primer. MATERIAL AND METHODS Ninety-six disks were fabricated from zirconia ceramic (e.max ZirCAD). Disks were conditioned either with airborne-particle abrasion with 110 μm Al(2)O(3) (AB) or silica-coated (SC). Thereafter, disks were cleaned either with oil-free air (A) or by ultrasonic cleaning (U) in alcohol. A conventional silane (S) (EspeSil) or a universal primer (P) (Monobond Plus) was applied to the conditioned surface. Six groups (n=16) were tested: SC-A-S; SC-U-S; SC-A-P; SC-U-P; AB-A-P, and AB-U-P. Transparent plastic tubes filled with composite resin were bonded to pretreated zirconia disks with adhesive luting cement (Multlink Automix). Each group was divided into 2 subgroups (n=8). Subgroups of 8 specimens each were either stored in 37°C water for 3 days without thermal cycling or in 37°C water for 150 days and exposed to 37,500 thermal cycles. Tensile bond strength (TBS) values were recorded with a universal testing machine. Statistical analyses were conducted with 3-way, 2-way, and 1-way ANOVAs and Tukeys HSD test (α=.05). RESULTS Long-term water storage and thermal cycling produced significantly lower (P<.05) means (TBS) in MPa than 3 days storage in water for the following groups SC-A-S, (38.3 ± 9.7/11.3 ± 5.1); SC-U-S, (31.5 ± 8.5/4.8 ± 6.9), and AB-A-P, (42.5 ±7/21.7 ±6). However, long term water storage and thermal cycling did not decrease TBS for groups SC-A-P, (44 ±6.4/36 ±7.3; P = 0.6); SC-U-P, (45.2 ±4.7/38.1 ±6.2; P=0.8); and AB-U-P, (44.1 ±8.9/33 ±9; P=.2). CONCLUSIONS A new universal primer provided significantly better long-term resin bonding to zirconia ceramic than a conventional silane. Cleaning methods had little effect on long-term resin bonding to zirconia ceramic.

Influence of surface treatment and cyclic loading on the durability of repaired all-ceramic crowns

Objective This study investigated the durability of repaired all-ceramic crowns after cyclic loading. Material and methods Eighty In-ceram zirconia crowns were fabricated to restore prepared maxillary premolars. Resin cement was used for cementation of crowns. Palatal cusps were removed to simulate fracture of veneering porcelain and divided into 4 groups (n = 20). Fracture site was treated before repair as follows: roughening with diamond bur, (DB); air abrasion using 50 µm Al2O3, (AA) and silica coating using Cojet system followed by silane application, (SC). Control group (CG) 20 specimens were left without fracture. Palatal cusps were repaired using composite resin. Specimens were stored in water bath at 37°C for one week. Ten specimens of each group were subjected to cyclic loading. Fracture load (N) was recorded for each specimen using a universal testing machine. Two-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) test (α=.05) were used for statistical analysis. Results There was statistically significant difference between control and tested groups, (p<0.001). Post Hoc analysis with the Tukey HSD test showed that cyclic loading fatigue significantly decreased means fracture load of control and test groups as follows (CG, 950.4±62.6 / 872.3±87.4, P = 0.0004), (DB, 624.2 ±38 / 425.5± 31.7, P <.001), (AA, 711.5 ±15.5 / 490 ± 25.2, p <0.001) and (SC, 788.7 ± 18.1 / 610.2 ± 25.2, P <.001), while silica coating and silane application significantly increased fracture load of repaired crowns (p<0.05). Conclusion Repair of fractured Inceram zirconia crowns after chairside treatment of the fracture site by silica coating and silane application could improve longevity of repaired In-ceram zirconia crowns.

Effect of cleaning methods after reduced-pressure air abrasion on bonding to zirconia ceramic.

PURPOSE To evaluate in vitro the influence of different cleaning methods after low-pressure air abrasion on the bond strength of a phosphate monomer-containing luting resin to zirconia ceramic. MATERIALS AND METHODS A total of 112 zirconia ceramic disks were divided into 7 groups (n = 16). In the test groups, disks were air abraded at low pressure (L) 0.05 MPa using 50-μm alumina particles. Prior to bonding, the disks were ultrasonically (U) cleaned either in isopropanol alcohol (AC), hydrofluoric acid (HF), demineralized water (DW), or tap water (TW), or they were used without ultrasonic cleaning. Disks air abraded at a high (H) pressure of 0.25 MPa and cleaned ultrasonically in isopropanol served as positive control; original (O) milled disks used without air abrasion served as the negative control group. Plexiglas tubes filled with composite resin were bonded with the adhesive luting resin Panavia 21 to the ceramic disks. Prior to testing tensile bond strength (TBS), each main group was further subdivided into 2 subgroups (n=8) which were stored in distilled water either at 37°C for 3 days or for 30 days with 7500 thermal cycles. Statistical analyses were conducted with two- and one-way analyses of variance (ANOVA) and Tukeys HSD test. RESULTS Initial tensile bond strength (TBS) ranged from 32.6 to 42.8 MPa. After 30 days storage in water with thermocycling, TBS ranged from 21.9 to 36.3 MPa. Storage in water and thermocycling significantly decreased the TBS of test groups which were not air abraded (p = 0.05) or which were air abraded but cleaned in tap water (p = 0.002), but not the TBS of the other groups (p > 0.05). Also, the TBS of air-abraded groups were significantly higher than the TBS of the original milled (p < 0.01). Cleaning procedures did not significantly affect TBS either after 3 days or 30 days storage in water and thermocycling (p > 0.05). CONCLUSION Air abrasion at 0.05 MPa and ultrasonic cleaning are important factors for improving bonding to zirconia ceramic.