The effect of a desensitizer and CO2 laser irradiation on bond performance between eroded dentin and resin composite

PURPOSE

This study was aimed to evaluate effect of the desensitizing pretreatments on the micro-tensile bond strengths (µTBS) to eroded dentin and sound dentin.

MATERIALS AND METHODS

Forty-two extracted molars were prepared to form a flat dentin surface, and then they were divided into two groups. Group I was stored in distilled water while group II was subjected to a pH cycling. Each group was then subdivided into three subgroups according to desensitizing pretreatment used: a) pretreatment with desensitizer (Gluma); b) pretreatment with CO₂ Laser (Ultra Dream Pluse); c) without any pretreatment. All prepared surfaces were bonded with Single Bond 2 and built up with resin composite (Filtek Z250). The micro-tensile bond test was performed. Fracture modes were evaluated by stereomicroscopy. Pretreated surfaces and bonded interfaces were characterized by scanning electron microscope (SEM). The data obtained was analyzed by two-way ANOVA (α=0.05).

RESULTS

For both sound and eroded dentin, samples treated with desensitizer showed the greatest µTBS, followed by samples without any treatment. And samples treated with CO₂ laser showed the lowest µTBS. SEM study indicated that teeth with eroded dentin appeared prone to debonding, as demonstrated by existence of large gaps between adhesive layers and dentin.

CONCLUSION

Pretreatment with Gluma increased the µTBS of Single Bond 2 for eroded and sound teeth. CO₂ laser irradiation weakened bond performance for sound teeth but had no effect on eroded teeth.     

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 Tukey''s 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.     

Effect of silica coating and silane surface treatment on the bond strength of soft denture liner to denture base material

Objective

This study investigated the effects of different surface treatments on the tensile bond strength of an autopolymerizing silicone denture liner to a denture base material after thermocycling.

Material and Methods

Fifty rectangular heat-polymerized acrylic resin (QC-20) specimens consisting of a set of 2 acrylic blocks were used in the tensile test. Specimens were divided into 5 test groups (n=10) according to the bonding surface treatment as follows: Group A, adhesive treatment (Ufi Gel P adhesive) (control); Group S, sandblasting using 50-µm Al₂O₃; Group SCSIL, silica coating using 30-µm Al₂O₃ modified by silica and silanized with silane agent (CoJet System); Group SCA, silica coating and adhesive application; Group SCSILA, silica coating, silane and adhesive treatment. The 2 PMMA blocks were placed into molds and the soft lining materials (Ufi Gel P) were packed into the space and polymerized. All specimens were thermocycled (5,000 cycles) before the tensile test. Bond strength data were analyzed using 1-way ANOVA and Duncan tests. Fracture surfaces were observed by scanning electron microscopy. X-ray photoelectron spectrometer (XPS) and Fourier Transform Infrared spectrometer (FTIR) analysis were used for the chemical analysis and a profilometer was used for the roughness of the sample surfaces.

Results

The highest bond strength test value was observed for Group A (1.35±0.13); the lowest value was for Group S (0.28±0.07) and Group SCSIL (0.34±0.03). Mixed and cohesive type failures were seen in Group A, SCA and SCSILA. Group S and SCSIL showed the least silicone integrations and the roughest surfaces.

Conclusion

Sandblasting, silica coating and silane surface treatments of the denture base resin did not increase the bond strength of the silicone based soft liner. However, in this study, the chemical analysis and surface profilometer provided interesting insights about the bonding mechanism between the denture base resin and silicone soft liner.     

EFFECT OF THERMOCYCLING ON THE TENSILE AND SHEAR BOND STRENGTHS OF THREE SOFT LINERS TO A DENTURE BASE RESIN

Statement of problem

In clinical practice, loss of adhesion between the silicone-based denture liner and the denture base resin is always an undesirable event that might cause loss of material softness, water sorption, bacterial colonization and functional failure of the prosthesis.

Purpose

This study evaluated the effect of thermocycling on tensile and shear bond strengths of three soft liner materials to a denture base acrylic resin.

Material and methods

Three resilient liners (Mucopren-Soft, Mollosil-Plus and Dentusil) and a heat-polymerized acrylic resin (QC-20) were processed according to manufacturers’ directions. Sixty specimens (14 x 14 mm cross-sectional area) per bond strength test (20 for each liner) were fabricated and either stored in water at 37°C for 24 hours (control groups; n=10) or thermocycled 3,000 times in water between 5°C and 55°C (test groups; n=10). The specimens were tested in tensile and shear strength in a universal testing machine until fracture. Bond strength means were compared between water-stored and thermocycled groups for each material, as well as among materials for each treatment (water storage or thermocycling). Failure mode (adhesive, cohesive and mixed) after debonding was assessed. Data were analyzed statistically by paired Student’s t-test and ANOVA at 5% significance level.

Results

The water-stored groups had statistically significant higher bond strengths than the thermocycled groups (p<0.05). Without thermocycling, Mucopren-Soft (2.83 ± 0.48 MPa) had higher bond strength than Mollosil-Plus (1.04 ± 0.26 MPa) and Dentusil (1.14 ± 0.51 MPa). After thermocycling, Mucopren-Soft (1.63 ± 0.48 MPa) had the highest bond strength (p<0.05).

Conclusion

The bond strength of the three soft denture liners tested in this study changed with their chemical composition and all of them exhibited higher bond strengths than those usually reported as clinically acceptable.

Clinical Implications

All soft lining materials tested in this study showed a significant decrease in the bond strength to an acrylic denture base resin after thermocycling. In spite of thermocycling, though, the silicone-based liners had satisfactory bond strengths for clinical application.     

Influence of sodium hypochlorite and EDTA on the microtensile bond strength of a self-etching adhesive system

Chemical substances used during biomechanical preparation of root canals can alter the composition of dentin surface and affect the interaction with restorative materials.

Objective

The purpose of this study was to evaluate the microtensile bond strength (µTBS) of a self-etching adhesive system to dentin irrigated with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (eDTA).

Material and Methods

Thirty human third molars were sectioned 3 mm below the occlusal surface, polished with 600- to 1200-grit silicon carbide papers, and randomly divided into 3 groups: G1 (control): no irrigating solution; G2: 1% NaOCl; and G3: 1% NaOCl followed by the application of 17% eDTA. The specimens received the self-etching adhesive system (XeNO III - Dentsply), restored with microhybrid composite resin (Z250 - 3M ESPE), sectioned and trimmed to create 4 hourglass-shaped slabs of each tooth. The slabs were tested in microtensile strength in a universal testing machine (emic DL 2000) at a crosshead speed of 0.5 mm/min until fracture. The results were analyzed statistically by ANOVA and Newman-Keuls test.

Results

Mean µTBS values and standard deviations in MPa were: G1 = 11.89 ± 4.22; G2 = 19.41 ± 5.32; G3 = 11.34 ± 4.73. 1% NaOCl increased the adhesive resistance significantly (p<0.001/ F=22.5763). The application of 1% NaOCl/17% eDTA resulted in statistically similar µTBS to the control group.

Conclusions

None of the irrigants affected negatively the µTBS of XeNO III to dentin. The use of 1% NaOCl alone resulted in higher bond strength than the other treatments. The combination of 1% NaOCl and 17% eDTA produced similar bond strength to that of untreated dentin.     

Shear bond strength of resin cement to an acid etched and a laser irradiated ceramic surface

PURPOSE

To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic.

MATERIALS AND METHODS

Fifty-five ceramic blocks (5 mm × 5 mm × 2 mm) were fabricated and embedded in acrylic resin. Their surfaces were finished with 1000-grit silicon carbide paper. The blocks were assigned to five groups: 1) 9.5% hydrofluoric-acid etching for 60 s; 2-4), 1.5-, 2.5-, and 6-W Er,Cr:YSGG laser applications for 60 seconds, respectively; and 5) no treatment (control). One specimen from each group was examined using scanning electron microscopy. Ceramic primer (Rely X ceramic primer) and adhesive (Adper Single Bond) were applied to the ceramic surfaces, followed by resin cement to bond the composite cylinders, and light curing. Bonded specimens were stored in distilled water at 37℃ for 24 hours. Shear bond strengths were determined by a universal testing machine at 1 mm/min crosshead speed. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (α=0.05).

RESULTS

Adhesion was significantly stronger in Group 2 (3.88 ± 1.94 MPa) and Group 3 (3.65 ± 1.87 MPa) than in Control group (1.95 ± 1.06 MPa), in which bonding values were lowest (P<.01). No significant difference was observed between Group 4 (3.59 ± 1.19 MPa) and Control group. Shear bond strength was highest in Group 1 (8.42 ± 1.86 MPa; P<.01).

CONCLUSION

Er,Cr:YSGG laser irradiation at 1.5 and 2.5 W increased shear bond strengths between ceramic and resin cement compared with untreated ceramic surfaces. Irradiation at 6 W may not be an efficient ceramic surface treatment technique.     

Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

Objective

The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) to dentin of two different restorative systems: silorane-based (P90), and methacrylate-based (P60), using two cavity models.

Material and Methods

Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into two groups (n=10) restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer''s instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2) and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10). The teeth were sectioned into samples with area between 0.85 and 1.25 mm² that were submitted to µTBS testing, using a universal testing machine (EMIC) at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests.

Results

For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p<0.05). No statistical difference between restorative systems was shown for Class I cavity model (p>0.05), or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05). Regarding fracture pattern, there was no statistical difference among groups (p=0.0713) and 56.3% of the fractures were adhesive.

Conclusion

It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor.     

Evaluation of the bond strength between aged composite cores and luting agent

PURPOSE

The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent.

MATERIALS AND METHODS

Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to 55℃) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at α=.05.

RESULTS

Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between 7.07 ± 2.11 and 26.05 ± 6.53 N. The highest bond strength of 26.05 ± 6.53 N was obtained with Group 3. Group 5 showed the lowest value of bond strength.

CONCLUSION

Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.     

BOND STRENGTH DURABILITY OF SELF-ETCHING ADHESIVES AND RESIN CEMENTS TO DENTIN

Objectives:

To evaluate the microtensile bond strength (μTBS) of one- (Xeno III, Dentsply) and two-step (Tyrian-One Step Plus, Bisco) self-etching adhesive systems bonded to dentin and cemented to chemically cured (C&B Metabond) or light-cured paste of a dual-cure resin cement (Variolink II, Ivoclar) within a short (24 h) and long period of evaluation (90 days).

Material and Methods:

Forty recently extracted human molars had their roots removed and their occlusal dentin exposed and ground wet with 600-grit SiC paper. After application of one of the adhesives, the resin cement was applied to the bonded surface and a composite resin block was incrementally built up to a height of 5 mm (n=10). The restored teeth were stored in distilled water at 37°C for 7 days. The teeth were then cut along two axes (x and y), producing beam-shaped specimens with 0.8 mm² cross-sectional area, which were subjected to μTBS testing at a crosshead speed of 0.05 mm/min and stressed to failure after 24 h or 90 days of storage in water. The μTBS data in MPa were subjected to three-way analysis of variance and Tukey''s test (α= 0.05).

Results:

The interaction effect for all three factors was statistically significant (three-way ANOVA, p<0.001). All eight experimental means (MPa) were compared by the Tukey''s test (p<0.05) and the following results were obtained: Tyrian-One Step Plus/C&B/24 h (22.4±7.3); Tyrian-One Step Plus/Variolink II/24 h (39.4±11.6); Xeno III/C&B/24 h (40.3±12.9); Xeno III/Variolink II/24 h (25.8±10.5); Tyrian-One Step Plus/C&B/90 d (22.1±12.8) Tyrian-One Step Plus/VariolinkII/90 d (24.2±14.2); Xeno III/C&B/90 d (27.0±13.5); Xeno III/Variolink II/ 90 d (33.0±8.9).

Conclusions:

Xeno III/Variolink II was the luting agent/adhesive combination that provided the most promising bond strength after 90 days of storage in water.     

Effect of various intraoral repair systems on the shear bond strength of composite resin to zirconia

PURPOSE

This study compared the effect of three intraoral repair systems on the bond strength between composite resin and zirconia core.

MATERIALS AND METHODS

Thirty zirconia specimens were divided into three groups according to the repair method: Group I- CoJet™ Repair System (3M ESPE) [chairside silica coating with 30 µm SiO₂ + silanization + adhesive]; Group II- Ceramic Repair System (Ivoclar Vivadent) [etching with 37% phosphoric acid + Zirconia primer + adhesive]; Group III- Signum Zirconia Bond (Heraus) [Signum Zirconia Bond I + Signum Zirconia Bond II]. Composite resin was polymerized on each conditioned specimen. The shear bond strength was tested using a universal testing machine, and fracture sites were examined with FE-SEM. Surface morphology and wettability after surface treatments were examined additionally. The data of bond strengths were statistically analyzed with one-way ANOVA and Tamhane post hoc test (α=.05).

RESULTS

Increased surface roughness and the highest wettability value were observed in the CoJet sand treated specimens. The specimens treated with 37% phosphoric acid and Signum Zirconia Bond I did not show any improvement of surface irregularity, and the lowest wettability value were found in 37% phosphoric acid treated specimens. There was no significant difference in the bond strengths between Group I (7.80 ± 0.76 MPa) and III (8.98 ± 1.39 MPa). Group II (3.21 ± 0.78 MPa) showed a significant difference from other groups (P<.05).

CONCLUSION

The use of Intraoral silica coating system and the application of Signum Zirconia Bond are effective for increasing the bond strength of composite resin to zirconia.     

Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine?)

Objectives

Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB) composites, silorane-based (SB) composites, and glass ionomer cement (GIC) to Biodentine^® and mineral trioxide aggregate (MTA).

Material and Methods

Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole) were prepared. In 45 of the samples, the holes were fully filled with Biodentine^® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine^® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS) test, each block was secured in a universal testing machine.

Results

The highest (17.7±6.2 MPa) and the lowest (5.8±3.2 MPa) bond strength values were recorded for the MB composite-Biodentine^® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7±6.2) than it did to MTA (8.9±5.7) (p<0.001), the SB composite (SB and MTA=7.4±3.3; SB and Biodentine^®=8.0±3,6) and GIC (GIC and MTA=5.8±3.2; GIC and Biodentine=6.7±2.6) showed similar bond strength performance with MTA compared with Biodentine (p=0.73 and p=0.38, respectively).

Conclusions

The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite.     

Evaluating resin-enamel bonds by microshear and microtensile bond strength tests: effects of composite resin

Objectives

The aims of this study were to evaluate the effect of resin composite (Filtek Z250 and Filtek Flow Z350) and adhesive system [(Solobond Plus, Futurabond NR (VOCO) and Adper Single Bond (3M ESPE)] on the microtensile (µTBS) and microshear bond strength (µSBS) tests on enamel, and to correlate the bond strength means between them.

Material and methods

Thirty-six extracted human molars were sectioned to obtain two tooth halves: one for µTBS and the other one for µSBS. Adhesive systems and resin composites were applied to the enamel ground surfaces and light-cured. After storage (37ºC/24 h) specimens were stressed (0.5 mm/ min). Fracture modes were analyzed under scanning electron microscopy. The data were analyzed using two-way ANOVA and Tukey''s test (α=0.05).

Results

The correlation between tests was estimated with Pearson''s product-moment correlation statistics (α =0.05). For both tests only the main factor resin composite was statistically significant (p<0.05). The correlation test detected a positive (r=0.91) and significant (p=0.01) correlation between the tests.

Conclusions

The results were more influenced by the resin type than by the adhesives. Both microbond tests seem to be positive and linearly correlated and can therefore lead to similar conclusions.     

Adhesive bonding of resin composite to various titanium surfaces using different metal conditioners and a surface modification system

Objective

This study evaluated the effect of three metal conditioners on the shear bond strength (SBS) of a prosthetic composite material to cpTi grade I having three surface treatments.

Material and Methods

One hundred sixty eight rivet-shaped specimens (8.0x2.0 mm) were cast and subjected to polishing (P) or sandblasting with either 50 mm (50SB) or 250 mm (250SB) Al₂O₃. The metal conditioners Metal Photo Primer (MPP), Cesead II Opaque Primer (OP), Targis Link (TL), and one surface modification system Siloc (S), were applied to the specimen surfaces, which were covered with four 1-mm thick layers of resin composite. The resin layers were exposed to curing light for 90 s separately. Seven specimens from each experimental group were stored in water at 37ºC for 24 h while the other 7 specimens were subjected to 5,000 thermal cycles consisting of water baths at 4ºC and 60ºC (n=7). All specimens were subjected to SBS test (0.5 mm/min) until failure occurred, and further 28 specimens were analyzed using scanning electron microscope (SEM) and X-ray energy-dispersive spectroscopy (EDS). Data were analyzed by 3-way ANOVA followed by post-hoc Tukey''s test (α=0.05).

Results

On 50SB surfaces, OP groups showed higher SBS means than MPP (P<0.05), while no significant difference was found among OP, S, and TL groups. On 250SB surfaces, OP and TL groups exhibited higher SBS than MPP and S (P<0.05). No significant difference in SBS was found between OP and TL groups nor between MPP and S groups. The use of conditioners on 250SB surfaces resulted in higher SBS means than the use of the same products on 50SB surfaces (P<0.05).

Conclusion

Sandblasting associated with the use of metal conditioners improves SBS of resin composites to cpTi.     

Porcelain repair - Influence of different systems and surface treatments on resin bond strength

PURPOSE

The purpose of this study was to evaluate the bond strength of composite resin on the fracture surface of metal-ceramic depending on the repair systems and surface roughening methods.

MATERIALS AND METHODS

A total of 30 disk specimens were fabricated, 15 of each were made from feldspathic porcelain and nickel-chromium base metal alloy. Each substrate was divided into three groups according to the repair method: a) application of repair system I (Intraoral Repair Kit) with diamond bur roughening (Group DP and DM), b) application of repair system I with airborne-particle abrasion (Group SP and SM), and c) application of repair system II (CoJet Intraoral Repair System, Group CP and CM). All specimens were thermocycled, and the shear bond strength was measured. The data were analyzed using the Kruskal-Wallis analysis and the Mann-Whitney test with a significance level of 0.05.

RESULTS

For the porcelain specimens, group SP showed the highest shear bond strength (25.85 ± 3.51 MPa) and group DP and CP were not significantly different. In metal specimens, group CM showed superior values of bond strength (13.81 ± 3.45 MPa) compared to groups DM or SM.

CONCLUSION

Airborne-particle abrasion and application of repair system I can be recommended in the case of a fracture localized to the porcelain. If the fracture extends to metal surface, the repair system II is worthy of consideration.     

Effect of the application time of phosphoric acid and self-etch adhesive systems to sclerotic dentin

Objectives:

To evaluate the effect of application time on the resin-dentin bond strength (µTBS) and etching pattern of adhesive systems applied on sclerotic dentine.

Material and Methods:

A total of forty-two bovine incisors had their roots removed. The 1-step self-etch GO (SDI), the 2-step self-etch Adper SE Bond (3MESPE) and the 35% phosphoric acid (3MESPE) from the 2-step etch-and-rinse Adper Single Bond 2 (3MESPE) were applied on the bovine incisal surfaces according to the manufacturer''s instructions or duplicating the recommended conditioning time. After adhesive application, thirty teeth were restored with composite resin, stored for 24 h in distilled water at 37º C, and sectioned into resin-dentin bonded sticks (0.8 mm²⁾ and tested according to the µTBS at 0.5 mm/min. The etching pattern of the remaining twelve teeth (n=4 for each material) was examined under scanning electron microscopy. Each tooth was divided into a buccal-to-lingual direction into three thirds, and each third randomly assigned to the groups: control (no treatment), according to the manufacturers'' instructions and duplicating the recommended application time. The µTBS and the relative percentage of the tubule area opening were evaluated by two-way repeated measures ANOVA and Tukey''s tests (α=0.05).

Results:

The duplication of the conditioning time favored only the GO adhesive (p<0.05). Both application methods significantly increased the tubule area opening (p<0.05) compared to the controls.

Conclusions:

The efficacy of duplicating the conditioning time was only effective for the 1-step self-etch adhesive system tested.     

Comparative evaluation of effects of different surface treatment methods on bond strength between fiber post and composite core

PURPOSE

Debonding of a composite resin core of the fiber post often occurs at the interface between these two materials. The aim of this study was to evaluate the effects of different surface treatment methods on bond strength between fiber posts and composite core.

MATERIALS AND METHODS

Sixty-four fiber posts were picked in two groups (Hetco and Exacto). Each group was further divided into four subgroups using different surface treatments: 1) silanization; 2) sandblasting; 3) Treatment with 24% H₂O₂, and 4) no treatment (control group). A cylindrical plexiglass matrix was placed around the post and filled with the core resin composite. Specimens were stored in 5000 thermal cycles between 5℃ and 55℃. Tensile bond strength (TBS) test and evaluation using stereomicroscope were performed on the specimen and the data were analyzed using two-way ANOVA, Post Hoc Scheffe tests and Fisher''s Exact Test (α=.05).

RESULTS

There was a significant difference between the effect of different surface treatments on TBS (P<.001) but different brands of post (P=.743) and interaction between the brand of post and surface treatment (P=.922) had no significant effect on TBS. Both silanization and sandblasting improved the bonding strength of fiber posts to composite resin core, but there were not any significant differences between these groups and control group.

CONCLUSION

There was not any significant difference between two brands of fiber posts that had been used in this study. Although silanization and sandblasting can improve the TBS, there was not any significant differences between surface treatments used.     

Evaluation of shear bond strength of repair acrylic resin to Co-Cr alloy

PURPOSE

The purpose of this study was to investigate the impact of different surface treatment methods and thermal ageing on the bond strength of autopolymerizing acrylic resin to Co-Cr.

MATERIALS AND METHODS

Co-Cr alloy specimens were divided into five groups according to the surface conditioning methods. C: No treatment; SP: flamed with the Silano-Pen device; K: airborne particle abrasion with Al₂O₃; Co: airborne particle abrasion with silica-coated Al₂O₃; KSP: flamed with the Silano-Pen device after the group K experimental protocol. Then, autopolymerized acrylic resin was applied to the treated specimen surfaces. All the groups were divided into two subgroups with the thermal cycle and water storage to determine the durability of the bond. The bond strength test was applied in an universal test machine and treated Co-Cr alloys were analyzed by scanning electron microscope (SEM). Two-way analysis of variance (ANOVA) was used to determine the significant differences among surface treatments and thermocycling. Their interactons were followed by a multiple comparison'' test performed uing a post hoc Tukey HSD test (α=.05).

RESULTS

Surface treatments significantly increased repair strengths of repair resin to Co-Cr alloy. The repair strengths of Group K, and Co significantly decreased after 6,000 cycles (P<.001).

CONCLUSION

Thermocycling lead to a significant decrease in shear bond strength for air abrasion with silica-coated aluminum oxide particles. On the contrary, flaming with Silano-Pen did not cause a significant reduction in adhesion after thermocycling.     

Evaluation of shear bond strength between dual cure resin cement and zirconia ceramic after thermocycling treatment

PURPOSE

This study was performed to evaluate shear bond strength (SBS) between three dual-cured resin cements and silica coated zirconia, before and after thermocycling treatment.

MATERIALS AND METHODS

Sixty specimens were cut in 15 × 2.75 mm discs using zirconia. After air blasting of 50 µm alumina, samples were prepared by tribochemical silica coating with Rocatec™ plus. The specimens were divided into three groups according to the dual-cure resin cement used: (1) Calibra silane+Calibra®, (2) Monobond S+Multilink® N and (3) ESPN sil+RelyX™ Unicem Clicker. After the resin cement was bonded to the zirconia using a Teflon mold, photopolymerization was carried out. Only 10 specimens in each group were thermocycled 6,000 times. Depending on thermocycling treatment, each group was divided into two subgroups (n=10) and SBS was measured by applying force at the speed of 1 mm/min using a universal testing machine. To find out the differences in SBS according to the types of cements and thermocycling using the SPSS, two-way ANOVA was conducted and post-hoc analysis was performed by Turkey''s test.

RESULTS

In non-thermal aged groups, SBS of Multilink group (M1) was higher than that of Calibra (C1) and Unicem (U1) group (P<.05). Moreover, even after thermocycling treatment, SBS of Multilink group (M2) was higher than the other groups (C2 and U2). All three cements showed lower SBS after the thermocycling than before the treatments. But Multilink and Unicem had a significant difference (P<.05).

CONCLUSION

In this experiment, Multilink showed the highest SBS before and after thermocycling. Also, bond strengths of all three cements decreased after thermocycling.     

The effect of alumina and aluminium nitride coating by reactive magnetron sputtering on the resin bond strength to zirconia core

PURPOSE

Although several surface treatments have been recently investigated both under in vitro and in vivo conditions, controversy still exists regarding the selection of the most appropriate zirconia surface pre-treatment. The purpose of this study was to evaluate the effect of alumina (Al) and aluminium nitride (AlN) coating on the shear bond strength of adhesive resin cement to zirconia core.

MATERIALS AND METHODS

Fifty zirconia core discs were divided into 5 groups; air particle abrasion with 50 µm aluminum oxide particles (Al₂O₃), polishing + Al coating, polishing + AlN coating, air particle abrasion with 50 µm Al₂O₃ + Al coating and air particle abrasion with 50 µm Al₂O₃ + AlN coating. Composite resin discs were cemented to each of specimens. Shear bond strength (MPa) was measured using a universal testing machine. The effects of the surface preparations on each specimen were examined with scanning electron microscope (SEM). Data were statistically analyzed by one-way ANOVA (α=.05).

RESULTS

The highest bond strengths were obtained by air abrasion with 50 µm Al₂O₃, the lowest bond strengths were obtained in polishing + Al coating group (P<.05).

CONCLUSION

Al and AlN coatings using the reactive magnetron sputtering technique were found to be ineffective to increase the bond strength of adhesive resin cement to zirconia core.