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.     

Comparative study of the shear bond strength of various veneering materials on grade II commercially pure titanium

PURPOSE

To compare the shear bond strength of various veneering materials to grade II commercially pure titanium (CP-Ti).

MATERIALS AND METHODS

Thirty specimens of CP-Ti disc with 9 mm diameter and 10 mm height were divided into three experimental groups. Each group was bonded to heat-polymerized acrylic resin (Lucitone 199), porcelain (Triceram), and indirect composite (Sinfony) with 7 mm diameter and 2 mm height. For the control group (n=10), Lucitone 199 were applied on type IV gold alloy castings. All samples were thermocycled for 5000 cycles in 5-55℃ water. The maximum shear bond strength (MPa) was measured with a Universal Testing Machine. After the shear bond strength test, the failure mode was assessed with an optic microscope and a scanning electron microscope. Statistical analysis was carried out with a Kruskal-Wallis Test and Mann-Whitney Test.

RESULTS

The mean shear bond strength and standard deviations for experimental groups were as follows: Ti-Lucitone 199 (12.11 ± 4.44 MPa); Ti-Triceram (11.09 ± 1.66 MPa); Ti-Sinfony (4.32 ± 0.64 MPa). All of these experimental groups showed lower shear bond strength than the control group (16.14 ± 1.89 MPa). However, there was no statistically significant difference between the Ti-Lucitone 199 group and the control group, and the Ti-Lucitone 199 group and the Ti-Triceram group. Most of the failure patterns in all experimental groups were adhesive failures.

CONCLUSION

The shear bond strength of veneering materials such as heat-polymerized acrylic resin, porcelain, and indirect composite to CP-Ti was compatible to that of heatpolymerized acrylic resin to cast gold alloy.     

Effect of silane activation on shear bond strength of fiber-reinforced composite post to resin cement

PURPOSE

Among the surface treatment methods suggested to enhance the adhesion of resin cement to fiber-reinforced composite posts, conflicting results have been obtained with silanization. In this study, the effects of silanization, heat activation after silanization, on the bond strength between fiber-reinforced composite post and resin cement were determined.

MATERIALS AND METHODS

Six groups (n=7) were established to evaluate two types of fiber post (FRC Postec Plus, D.T. Light Post) and three surface treatments (no treatment; air drying; drying at 38℃). Every specimen were bonded with dual-curing resin cement (Variolink N) and stored in distilled water for 24 hours at 37℃. Shear-bond strength (MPa) between the fiber post and the resin cement were measured using universal testing device. The data were analyzed with 1-way ANOVA and by multiple comparisons according to Tukey''s HSD (α=0.05). The effect of surface treatment, fiber post type, and the interactions between these two factors were analyzed using 2-way ANOVA and independent sample T-tests.

RESULTS

Silanization of the FRC Postec Plus significantly increased bond strength compared with the respective non-treated control, whereas no effect was determined for the D.T. Light Post. Heat drying the silane coupling agent on to the fiber-reinforced post did not significantly improve bond strength compared to air-syringe drying.

CONCLUSION

The bond strength between the fiber-reinforced post and the resin cement was significantly increased with silanization in regards to the FRC Postec Plus post. Bond strength was not significantly improved by heat activation of the silane coupling agent.     

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 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.     

The effect of different fiber reinforcements on flexural strength of provisional restorative resins: an in-vitro study

PURPOSE

The aim of this study was to compare the flexural strength of polymethyl methacrylate (PMMA) and bis-acryl composite resin reinforced with polyethylene and glass fibers.

MATERIALS AND METHODS

Three groups of rectangular test specimens (n = 15) of each of the two resin/fiber reinforcement were prepared for flexural strength test and unreinforced group served as the control. Specimens were loaded in a universal testing machine until fracture. The mean flexural strengths (MPa) was compared by one way ANOVA test, followed by Scheffe analysis, using a significance level of 0.05. Flexural strength between fiber-reinforced resin groups were compared by independent samples t-test.

RESULTS

For control groups, the flexural strength for PMMA (215.53 MPa) was significantly lower than for bis-acryl composite resin (240.09 MPa). Glass fiber reinforcement produced significantly higher flexural strength for both PMMA (267.01 MPa) and bis-acryl composite resin (305.65 MPa), but the polyethylene fibers showed no significant difference (PMMA resin-218.55 MPa and bis-acryl composite resin-241.66 MPa). Among the reinforced groups, silane impregnated glass fibers showed highest flexural strength for bis-acryl composite resin (305.65 MPa).

CONCLUSION

Of two fiber reinforcement methods evaluated, glass fiber reinforcement for the PMMA resin and bis-acryl composite resin materials produced highest flexural strength.

Clinical implications

On the basis of this in-vitro study, the use of glass and polyethylene fibers may be an effective way to reinforce provisional restorative resins. When esthetics and space are of concern, glass fiber seems to be the most appropriate method for reinforcing provisional restorative resins.     

Effects of coloring procedures on zirconia/veneer ceramics bond strength

PURPOSE

The most common failure seen in restorations with a zirconia core is total or layered delamination of the ceramic veneer. In the present study, the shear bond strengths between veneering ceramics and colored zirconia oxide core materials were evaluated.

MATERIALS AND METHODS

Zirconia discs (15 × 12 × 1.6 mm) were divided into 11 groups of 12 discs each. Groups were colored according to the Vita Classic scale: A3, B1, C4, D2, and D4. Each group was treated with the recommended shading time for 3 s, or with prolonged shading for 60 s, except for the control group. Samples were veneered with 3 mm thick and 3.5 mm in diameter translucent ceramic and subjected to shear test in a universal testing machine with a crosshead speed of 1 mm/min. One-way analysis of variance (ANOVA) and Tukey''s HSD tests were used for comparisons of the groups having the same shading times. A paired t-test was used for groups of the same color (3 s/60 s).

RESULTS

Among the 11 groups investigated C4 (3 s) had the highest bond strength with a value of 36.40 MPa, while A3 (3 s) showed the lowest bond strength with a value of 29.47 MPa.

CONCLUSION

Coloring procedures can affect zirconia/ceramic bond strength. However, the results also showed that bond strengths of all the investigated groups were clinically acceptable.     

Shear bond strength of one-step self-etch adhesives with different co-solvent ingredients to dry or moist dentin

Objective

To evaluate the shear bond strength of one-step self-etch adhesives with different co-solvent ingredients to dry or moist dentin.

Materials and methods

A total of 60 extracted teeth were used in this study, and were divided according to the adhesive systems and dentin conditions into 6 groups of 10 teeth each [Xeno III – dry dentin, Xeno III – moist dentin, Adper Prompot L-Pop – dry dentin, Adper Prompot L-Pop – moist dentin, iBond – dry dentin, and iBond – moist dentin]. Resin composite cylinder was built up on each specimen, and then thermocycled. A shear load was applied to the specimens using universal testing (Instron machine) at a cross-head speed of 0.5 mm/min until failure occurred. Data were statistically analyzed by one-way ANOVA and Bonferroni multiple comparison test at 95% confidence level.

Results and conclusion

Based on the findings of this study: The highest mean shear bond strength to dry dentin was seen when Xeno III containing ethanol co-solvent ingredient was used. The highest mean shear bond strength to moist dentin was seen when iBond which contains acetone co-solvent ingredient was used. In the absence of a co-solvent ingredient in self-etch adhesive (Adper Prompot L-Pop), the mean shear bond strengths to dry and moist dentin were low with no significant difference between them.     

In vitro study of fracture strength of provisional crown materials

PURPOSE

The purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns.

MATERIALS AND METHODS

A master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at 37℃ for 24 hours, and then they were thermocycled (TC, 5000×, 5-55℃) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (α=.05).

RESULTS

Fmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01).

CONCLUSION

Composite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CAD-CAM technique offers more advantages than the direct technique.     

Factors affecting the bond strength of denture base and reline acrylic resins to base metal materials

Objective

The shear bond strengths of two hard chairside reline resin materials and an auto-polymerizing denture base resin material to cast Ti and a Co-Cr alloy treated using four conditioning methods were investigated.

Material and Methods

Disk specimens (diameter 10 mm and thickness 2.5 mm) were cast from pure Ti and Co-Cr alloy. The specimens were wet-ground to a final surface finish of 600 grit, air-dried, and treated with the following bonding systems: 1) air-abraded with 50-70-µm grain alumina (CON); 2) 1) + conditioned with a primer, including an acidic phosphonoacetate monomer (MHPA); 3) 1) + conditioned with a primer including a diphosphate monomer (MDP); 4) treated with a tribochemical system. Three resin materials were applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles.

Results

The strengths decreased after thermocycling for all combinations. Among the resin materials assessed, the denture base material showed significantly (p<0.05) greater shear bond strengths than the two reline materials, except for the CON condition. After 10,000 thermocycles, the bond strengths of two reline materials decreased to less than 10 MPa for both metals. The bond strengths of the denture base material with MDP were sufficient: 34.56 MPa for cast Ti and 38.30 for Co-Cr alloy.

Conclusion

Bonding of reline resin materials to metals assessed was clinically insufficient, regardless of metal type, surface treatment, and resin composition. For the relining of metal denture frameworks, a denture base material should be used.     

Effect of light-curing units in shear bond strength of metallic brackets: an in vitro study

Objective

To determine the influence of the light curing units on the shear bond strength of orthodontic brackets.

Material and Methods

Seventy-two premolars were divided into six groups (n=12): Group I: brackets bonded with Transbond and polymerization with halogen light; Group II: Transbond and LED; Group III: Fuji Ortho and halogen light; Group IV: Fuji Ortho and LED; Group V: Fuji Ortho, without acid and halogen light; Group VI: Fuji Ortho, without acid and LED. The groups were tested to shear strength in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey’s test.

Results

The composite resin presented higher shear bond strength than the resin-modified glass ionomer cement (p<0.05). The halogen light and LED sources produced similar shear bond strength (p>0.05).

Conclusion

The shear bond strength was influenced by the material but not by the light-curing unit. The use of LED reduced the experimental time by approximately 60%, with the same curing efficiency.     

Shear bond strength of composite resin to titanium according to various surface treatments

STATEMENT OF PROBLEM

When veneering composite resin-metal restoration is prepared, the fact that bond strength between Ti and composite resin is relatively weak should be considered.

PURPOSE

The purpose of this study is to evaluate the shear bond strength between the veneering composite resin and commercial pure (CP) Ti / Ti-6Al-4V alloy according to the method of surface treatment.

MATERIAL AND METHODS

The disks were cast by two types of metal. Their surfaces were treated by sandblasting, metal conditioner, TiN coating and silicoating respectively. After surface treatment, the disks were veneered by composite resin (Tescera™, Bisco, USA) which is 5 mm in diameter and 3 mm in thickness. The specimens were stored in water at 25℃ for 24 hours, and then evaluated for their shear bond strength by universal testing machine (STM-5®, United Calibration, USA). These values were statistically analyzed.

RESULTS

1. All methods of surface treatment were used in this study satisfied the requirements of ISO 10477 which is the standard of polymer-based crown and bridge materials. 2. The metal conditioner treated group showed the highest value in shear bond strength of CP Ti, silicoated group, TiN coated group, sandblasted group, in following order. 3. The silicoated group showed the highest value in shear bond strength of Ti-6Al-4V alloy, metal conditioner treated group, sandblasted group, TiN coated group, in following order.

CONCLUSION

Within the limitations of this study, all methods of surface treatment used in this study are clinically available.     

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.     

SHEAR BOND STRENGTH OF METALLIC BRACKETS: INFLUENCE OF SALIVA CONTAMINATION

Objective:

To evaluate the influence of saliva contamination on shear bond strength and the bond failure pattern of 3 adhesive systems (Transbond XT, AdheSE and Xeno III) on orthodontic metallic brackets bonded to human enamel.

Material and Methods:

Seventy-two permanent human molars were cut longitudinally in a mesiodistal direction, producing seventy-two specimens randomly divided into six groups. Each system was tested under 2 different enamel conditions: no contamination and contaminated with saliva. In T, A and X groups, the adhesive systems were applied to the enamel surface in accordance with manufacturer''s instructions. In TS, AS and XS groups, saliva was applied to enamel surface followed by adhesive system application. The samples were stored in distilled water at 37°C for 24 h, and then tested for shear bond strength in a universal testing machine (Emic, DL 2000) running at a crosshead speed of 1 mm/min. After bond failure, the enamel surfaces were observed under an optical microscope at 40x magnification.

Results:

The control and contaminated groups showed no significant difference in shear bond strength for the same adhesive system. However, shear bond strength of T group (17.03±4.91) was significantly higher than that of AS (8.58±1.73) and XS (10.39±4.06) groups (p<0.05). Regarding the bond failure pattern, TS group had significantly higher scores of no adhesive remaining on the tooth in the bonding area than other groups considering the adhesive remnant index (ARI) used to evaluate the amount of adhesive left on the enamel.

Conclusion:

Saliva contamination showed little influence on the 24-h shear bond strength of orthodontic brackets.     

Push-out bond strengths of fiber-reinforced composite posts with various resin cements according to the root level

PURPOSE

The aim of this study was to determine whether the push-out bond strengths between the radicular dentin and fiber reinforced-composite (FRC) posts with various resin cements decreased or not, according to the coronal, middle or apical level of the root.

MATERIALS AND METHODS

FRC posts were cemented with one of five resin cement groups (RelyX Unicem: Uni, Contax with activator & LuxaCore-Dual: LuA, Contax & LuxaCore-Dual: Lu, Panavia F 2.0: PA, Super-Bond C&B: SB) into extracted human mandibular premolars. The roots were sliced into discs at the coronal, middle and apical levels. Push-out bond strength tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min, and the failure aspect was analyzed.

RESULTS

There were no significant differences (P>.05) in the bond strengths of the different resin cements at the coronal level, but there were significant differences in the bond strengths at the middle and apical levels (P<.05). Only the Uni and LuA cements did not show any significant decrease in their bond strengths at all the root levels (P>.05); all other groups had a significant decrease in bond strength at the middle or apical level (P<.05). The failure aspect was dominantly cohesive at the coronal level of all resin cements (P<.05), whereas it was dominantly adhesive at the apical level.

CONCLUSION

All resin cement groups showed decreases in bond strengths at the middle or apical level except LuA and Uni.     

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.     

Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy

STATEMENT OF PROBLEM

The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive failure and increases microleakage.

PURPOSE

This study evaluated the shear bond strengths of a heat cure denture base resin to commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers.

MATERIAL AND METHODS

Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the controls. The shear bond strengths were measured on a screw-driven universal testing machine.

RESULTS

The primers significantly (P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy primer® (MDP monomer) showed higher bond strength than those primed with the MR bond® (MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure.

CONCLUSIONS

The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy primer®, which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to titanium than a MR bond®, which contains the carboxylic acid monomer, MAC-10.     

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.     

BOND STRENGTH OF HARD CHAIRSIDE RELINE RESINS TO A RAPID POLYMERIZING DENTURE BASE RESIN BEFORE AND AFTER THERMAL CYCLING

Purpose:

This study assessed the shear bond strength of 4 hard chairside reline resins (Kooliner, Tokuso Rebase Fast, Duraliner II, Ufi Gel Hard) to a rapid polymerizing denture base resin (QC-20) processed using 2 polymerization cycles (A or B), before and after thermal cycling.

Materials and Methods:

Cylinders (3.5 mm x 5.0 mm) of the reline resins were bonded to cylinders of QC-20 polymerized using cycle A (boiling water–20 minutes) or B (boiling water; remove heat-20 minutes; boiling water–20 minutes). For each reline resin/polymerization cycle combination, 10 specimens (groups CAt e CBt) were thermally cycled (5 and 55 °C; dwell time 30 seconds; 2,000 cycles); the other 10 were tested without thermal cycling (groups CAwt ad CBwt). Shear bond tests (0.5 mm/min) were performed on the specimens and the failure mode was assessed. Data were analyzed by 3-way ANOVA and Newman-Keuls post-hoc test (α=.05).

Results:

QC-20 resin demonstrated the lowest bond strengths among the reline materials (P<.05) and mainly failed cohesively. Overall, the bond strength of the hard chairside reline resins were similar (10.09±1.40 to 15.17±1.73 MPa) and most of the failures were adhesive/cohesive (mixed mode). However, Ufi Gel Hard bonded to QC-20 polymerized using cycle A and not thermally cycled showed the highest bond strength (P<.001). When Tokuso Rebase Fast and Duraliner II were bonded to QC-20 resin polymerized using cycle A, the bond strength was increased (P=.043) after thermal cycling.

Conclusions:

QC-20 displayed the lowest bond strength values in all groups. In general, the bond strengths of the hard chairside reline resins were comparable and not affected by polymerization cycle of QC-20 resin and thermal cycling.     

Mechanical,antibacterial and bond strength properties of nano-titanium-enriched glass ionomer cement

The use of nanoparticles (NPs) has become a significant area of research in Dentistry.

Objective

The aim of this study was to investigate the physical, antibacterial activity and bond strength properties of conventional base, core build and restorative of glass ionomer cement (GIC) compared to GIC supplemented with titanium dioxide (TiO₂) nanopowder at 3% and 5% (w/w).

Material and Methods

Vickers microhardness was estimated with diamond indenter. Compressive and flexural strengths were analyzed in a universal testing machine. Specimens were bonded to enamel and dentine, and tested for shear bond strength in a universal testing machine. Specimens were incubated with S. mutans suspension for evaluating antibacterial activity. Surface analysis of restorative conventional and modified GIC was performed with SEM and EDS. The analyses were carried out with Kolmogorov-Smirnov, ANOVA (post-hoc), Tukey test, Kruskal-Wallis, and Mann Whitney.

Results

Conventional GIC and GIC modified with TiO₂ nanopowder for the base/liner cement and core build showed no differences for mechanical, antibacterial, and shear bond properties (p>0.05). In contrast, the supplementation of TiO₂ NPs to restorative GIC significantly improved Vickers microhardness (p<0.05), flexural and compressive strength (p<0.05), and antibacterial activity (p<0.001), without interfering with adhesion to enamel and dentin.

Conclusion

GIC supplemented with TiO₂ NPs (FX-II) is a promising material for restoration because of its potential antibacterial activity and durable restoration to withstand the mastication force.