Influence of surface treatment on the resin-bonding of zirconia

Zirconia bond strength durability following artificial aging: A systematic review and meta-analysis of in vitro studies

The present study systematically reviewed the literature regarding the bond strength durability of zirconia ceramics to resin-based luting cements after application of different bonding protocols and aging conditions. Electronic searches in PubMed, Scopus, and Web of Science databases were performed for relevant literature published between January 1st 2015 and November 15th 2022. Ninety-three (93) English language in-vitro studies were included. The percentage of the mean bond strength change was recorded prior to and after artificial aging, and the weighted mean values and 95% confidence intervals were calculated. Bonding protocols were classified based on the combination of MDP/non-MDP containing cement/primer and surface pretreatment, as well as the level of artificial aging performed. Alumina sandblasting (SA) was identified as the most frequently used surface pre-treatment while an insufficient number of studies was identified for each category of alternative surface treatments. The combination of MDP cement with tribochemical silica coating (TSC) or SA yielded more durable results after aging, while the application of SA and TSC improved bond durability when a non-MDP cement and a non-MDP primer were used. TSC may lead to increased bond durability compared to SA, whereas MDP cements may act similarly when combined with SA or TSC.

Bonding effect of a Zr/Si coating prepared on zirconia using a sol-gel method

STATEMENT OF PROBLEM

Zirconia has been widely used as a dental prosthetic material. However, bonding to zirconia is challenging, and whether a Zr/Si coating would improve bonding is unclear.

PURPOSE

The purpose of this in vitro study was to prepare a Zr/Si coating on zirconia ceramics using a sol-gel method and to determine whether the bonding to resin is improved.

MATERIAL AND METHODS

Presintered zirconia specimens were prepared and divided into 5 groups: 4 experimental groups with ratios of the binary sol-gel precursor (zirconium oxychloride/tetraethoxysilane) set as 2:1 (Z2), 1:1 (Z1), 0.5:1 (Z0.5), and 0.25:1 (Z0.25) and Group C as the control group. In addition to surface roughness measurements, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD) were carried out to characterize the surface. Each group was divided into 2 subgroups according to whether a silane coupling agent was applied. Half of the bond specimens were stored in deionized water for 24 hours; the remaining half were aged using 5000 thermocycles. The shear bond strength (SBS) of resin bonded to specimens was tested for the initial and durable bond strength, and the bonding interface was also observed by SEM after debonding. Data were subjected to 1-way ANOVA and the post hoc Tukey honestly significant difference test (α=.05).

RESULTS

The Zr/Si coating formed on zirconia ceramics. Z0.5 had the greatest mean ±standard deviation roughness (2.13 ±0.15 μm) and had the highest silicon content (21.7 ±0.21%). t-ZrO₂, m-ZrO₂, c-SiO_2, and ZrSiO₄ were detected by XRD in Z1. The SBS values were decreased by aging but were significantly increased by Zr/Si coating, especially for Z0.5, with the application of silane (initial: 22.92 ±2.79 MPa; aged: 9.91 ±0.92 MPa).

CONCLUSIONS

The Zr/Si coating significantly improved the initial and aged bond strength, and the optimal Zr/Si ratio of the sol-gel appeared to be 0.5:1.

Shear bond strength of different bonding agents to orthodontic metal bracket and zirconia

This study aimed to evaluate the shear bond strength (SBS) of four bonding agents used to bond metal brackets to zirconia under different storage conditions. Four bonding agents were used [FLC: (Fuji ORTHO LC), XT: (Transbond^TM XT), RUC-SBU: (Rely X^TM Ultimate Clicker Adhesive Resin Cement+Single Bond Universal), and RUC-GBU: (Rely X^TM Ultimate Clicker Adhesive Resin Cement+Gluma Bond Universal)] to bond two types of metal brackets (PT/3M) to zirconia surfaces, and they were stored in water at 37ºC for 24 h or thermocycling for 3,000 cycles. The SBS data of RUC-SBU and RUC-GBU using PT brackets were significantly higher than those of 3M brackets before and after thermocycling. It could be concluded that RUC-SBU and RUC-GBU could offer sufficient bond strength between metal brackets and zirconia for the short term compared with FLC and XT. The design of brackets can significantly affect the bond strength to zirconia.

Effects of surface modification techniques on zirconia substrates and their effect on bonding to dual cure resin cement - An in- vitro study

Aim

This study aims to evaluate the effect of different surface treatments of monolithic zirconia on the bond strength of resin to zirconia and, to explore alternative methods to improve this bonding.

Settings and Design

In-Vitro study.

Materials and Methods

Fifty rectangular sintered blocks of Yttria-stabilized Tetragonal Zirconia Polycrystal ceramics of dimensions were milled and sintered. These specimens were further divided into five groups (control, air abrasion, etching with primer application, air abrasion with primer application and novel glass infiltrated zirconia surface group), containing 10 samples each. The specimens were analyzed for surface roughness, tensile bond strength to resin cements, and adhesive and cohesive mode of failures.

Statistical Analysis Used

ANOVA and Post-Hoc Tukey test was perform to evaluate the significant differences in the mean values of the groups.

Results

Air-abraded samples showed the highest surface roughness (4.95 ± 0.65) (P < 0.05). The group with air abrasion followed by primer application showed the highest tensile bond strength (7.12 ± 0.69) (P < 0.05). The lowest surface roughness (0.638 ± 0.8093) and tensile bond strength (2.03 ± 0.58) was seen in samples that were subjected to etchant treatment followed by application of methacryloyloxydecyl di-hydrogen phosphate (MDP) primer. The changes in comparison to the control group were statistically insignificant (P > 0.05). Except Groups A (control) and C (etchant followed by primer), all other groups showed a cohesive failure.

Conclusion

Air abrasion of the zirconia surface with 50 μm alumina particles increases the surface roughness without damaging the surface. Air abrasion followed by MDP primer application is the recommended method of surface treatment to achieve superior bonding. Glass infiltration also showed promising results in terms of tensile bond strength.

Influence of crystalline phase transformation induced by airborne-particle abrasion and low-temperature degradation on mechanical properties of dental zirconia ceramics stabilized with over 5 mol% yttria

Monolithic dental prostheses fabricated from 5 mol% yttria-stabilized zirconia (5YZ) have been developed to improve the translucency of conventional 3 mol% yttria-stabilized zirconia. In this study, we aimed to evaluate the influence of airborne-particle abrasion (APA) and low-temperature degradation (LTD) on the mechanical properties of 5YZ in association with the crystalline phase transformation. In total, 120 disc-shaped specimens of two brands of 5YZ (Lava Esthetic and Katana UTML) were prepared. The specimens were divided into four groups (n = 15 for each group): (i) control, (ii) APA, (iii) LTD, and (iv) APA + LTD groups. APA was performed with 50 μm alumina particles, and LTD was induced by autoclaving at 134 °C for 50 h. The biaxial flexural strength of the specimens was assessed using a piston-on-three-ball test according to ISO 6872:2015, and Vickers hardness was determined using a microhardness tester. The crystalline phase was analyzed by the Rietveld refinement of X-ray diffraction patterns. APA significantly increased the flexural strength of the Lava Esthetic specimens, whereas LTD hardly affected the strength of both materials. APA and APA + LTD significantly increased the Vickers hardness of both materials. According to Rietveld analysis, the pseudocubic phase was predominant in both materials, i.e., 66 mass% and 81 mass% in the Lava Esthetic and Katana UTML specimens, respectively. APA induced the rhombohedral phase at approximately 37 mass% in both materials, while LTD induced the monoclinic phase at 2.8 mass% in the Lava Esthetic specimens and 0.9 mass% in the Katana UTML specimens. APA + LTD weakly affected the amount of the rhombohedral phase but slightly increased the amount of the monoclinic phase. These findings suggest that APA may improve the mechanical properties of 5YZ, particularly hardness, via the generation of the rhombohedral phase. In contrast, the influence of LTD on the mechanical and microstructural properties of 5YZ was limited.

Analysis of bond strength between a nylon reinforcement structure and dental resins

Background

Nylon is a polymer that its use to reinforce dental resins has shown positive results such as increased flexural strength. The aim of this study was to evaluate the bond strength between dental resins and a nylon reinforcement.

Material and Methods

Forty cylindrical nylon blocks with 13 x 23 mm with 0.5% by volume of silica and 40 without were made. Half of the samples of each nylon composition were sandblasted with aluminum oxide (50μm) for 3 s (2.8 bar pressure, distance: 20 mm, incidence angle: 90o). On the nylon blocks, cylinders of chemically activated acrylic resin and indirect composite resin were made, with a bonding area of 6,28 mm2. Eight different groups were obtained according to the material used and the surface treatment (n = 10): Acrylic Resin + Nylon; GAS: Acrylic Resin + Nylon with Silica; GAT: Acrylic Resin + Nylon (Al2O3); GAST: Acrylic Resin + Nylon with Silica (Al2O3); GC: Composite Resin + Nylon; GCS: Composite Resin + Nylon with Silica; GCT: Composite Resin + Nylon (Al2O3); GCST: Composite Resin + Nylon with Silica (Al2O3). The shear test was carried out. The Student’s and the Kruskal-Wallis test was adopted.

Results

There was no statistically difference in the bond strength for nylon with silica for the acrylic resin group. For the composite groups, nylon with silica did not present a statistically difference without surface treatment (p = 0.10) and with surface treatment the bond strength decreased (p = 0.000). The GCT showed a higher bond strength (0.89 MPa). The surface treatment improved the bond strength for the both groups.

Conclusions

The presence of silica in the nylon composition did not influence the bond strength between materials evaluated. However, the surface treatment with aluminum oxide proved to be favorable for this adhesion.

Key words:Nylons - Resins, Synthetic - Structures Strengthening - Dental Research.

Bond strength of conventional, subtractive, and additive manufactured denture bases to soft and hard relining materials

OBJECTIVE

To investigate the tensile and flexural strength of poured, subtractive, and additive manufactured denture base methacrylates bonded to soft and hard relining materials after hydrothermal cycling and microwave irradiation.

METHODS

This study included a conventional (CB), subtractive (SB), and additive (AB) base material as well as a soft (SCR) and hard (HCR) chairside and one hard laboratory-side (HLR) relining material. Reference bodies of the base materials and bonded specimens to the relining materials were produced with a rectangular cross-section. The specimens were either pre-treated by water storage (50 h, 37 °C), hydrothermal cycling (5000 cycles, 5 °C and 55 °C, 30 s each), or microwave irradiation (6 cycles, 640 W, 3 min, wet). A tensile and four-point bending test were performed for a total of 504 specimens. Data were analysed using multivariate analysis of variance (MANOVA) with post-hoc Tukey tests (α = 0.05).

RESULTS

In comparison with the other reference groups SB showed marginally higher tensile and flexural strength (p < 0.047). Bond strength to SCR was affected neither by the base material nor by the pre-treatment (p > 0.085). HCR demonstrated twice the bond strength to AB compared with SB and CB (p ≤ 0.001). HLR showed the highest bond strength to CB (p ≤ 0.001). There was no difference between the specimens after hydrothermally cycling and microwave irradiation (p > 0.318).

SIGNIFICANCE

The bond strength of hard relining materials to subtractive and additive manufactured denture bases differ compared with conventional pouring.

Bond strength of surface-treated novel high translucent zirconia to enamel

Aim: The aim of the present study was to evaluate the shear bond strength of zirconia, stabilised with 5% yttria, luted to enamel and to evaluate the fracture pattern at loss of retention.

Methods: A total of 53 test specimen were manufactured from two partially stabilised zirconia materials, Zirkonzahn Prettau Anterior (ZPA) (n = 16) and Whitepeaks CopraSmile Symphony 5 layer (WCS) (n = 18), and a lithium disilicate (Ivoclar e.Max Press) (n = 19) acting as control. All test specimens were cemented to human enamel with Variolink Esthetic DC and then subjected to a shear bond strength test. Fracture and surface analysis were performed using light and scanning electron microscope.

Results: No significant differences in shear bond strength were detected when analysing the three groups. Dividing them according to the fracture pattern significant difference in shear bond strength between the two zirconia groups could be seen analysing test bodies with failure of adhesion to the test body, but not to enamel. The ZPA had higher shear bond strength (23.68 MPa) than WCS (13.00 MPa). No significant differences were seen compared to the control group (19.02 MPa).

Conclusion: Partially stabilised zirconia shows potential as a material to be used where macro mechanical bonding is not possible, although this study does not reveal how or if the bonding deteriorates over time.

Does the application of surface treatments in different sintering stages affect flexural strength and optical properties of zirconia?

OBJECTIVE

To investigate the influence of surface treatments conducted in presintering and postsintering stages on flexural strength and optical properties of zirconia.

MATERIALS AND METHODS

Specimens were milled from partially sintered zirconia blocks in different geometries and divided into three main groups as presintered, postsintered, and control groups. Test groups were further divided into three subgroups (n = 10) according to the surface treatments conducted (grinding, Er,Cr:YSGG laser irradiation, air-borne particle abrasion [APA]). Four-point flexural strength (σ) test and Weibull analysis were conducted. Color differences (ΔE₀₀ ) and translucency parameter (TP_ab ) were calculated with a spectrophotometer. Surfaces of specimens were scrutinized under FESEM. Data were statistically analyzed.

RESULTS

Postsintered groups exhibited higher σ values (P < .05). Within all groups, highest and lowest σ values were detected at postsintered and presintered APA groups, respectively (P < .05). All ΔE₀₀ values were above the perceptibility threshold (ΔE₀₀  > 0.8). Higher TP_ab values were obtained and deeper scratches were observed in presintered groups.

CONCLUSIONS

Surface treatments performed at postsintering stage had a favorable effect on the flexural strength of all specimens. Surface treatments performed before sintering increased translucency and caused higher ΔE₀₀ values.

CLINICAL SIGNIFICANCE

Surface treatments performed at different sintering stages can alter mechanical and optical properties of zirconia.

Effect of reduced airborne-particle abrasion pressure on the retention of zirconia copings resin bonded to titanium abutments

STATEMENT OF PROBLEM

The optimal conditioning of zirconia is essential for a durable bond between zirconia copings and titanium inserts in 2-piece dental implant abutments. Low-pressure activation of the zirconia surface may be adequate for retention.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of airborne-particle abrasion (APA) of the zirconia surface with different pressures on the retention of zirconia copings bonded to titanium abutments. In addition, 2 luting systems were compared.

MATERIAL AND METHODS

Computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia copings were divided into 3 groups (n=32): 0.1 MPa, 0.25 MPa, and not airborne-particle abraded surfaces with 50-μm alumina (Al₂O₃) particles. Compatible titanium abutments were airborne-particle abraded at a pressure of 0.25 MPa. All specimens were ultrasonically cleaned before bonding. Each group was divided into 2 subgroups (n=16) with different luting composite resins. A 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) containing self-adhesive luting composite resin (Panavia SA Cement Plus) and a conventional luting composite resin (Multilink Hybrid Abutment) in combination with a 10-MDP-containing universal primer (Monobond Plus) was compared. Two storage conditions were tested: in water (37 °C) for 3 days or 150 days with 37 500 thermocycles between 5 °C and 55 °C. After artificial aging, retention was measured in tension, and the failure modes were analyzed by using a light microscope and a scanning electron microscope. Statistical analysis was performed with 1-way ANOVA and the Games-Howell test for post hoc analysis (α=.05).

RESULTS

The mean retention of the airborne-particle abraded groups ranged from 576.0 N to 1049.3 N after 150 days of water storage and 37 500 thermocycles. No significant difference in bond strength was found between the 2 luting composite resin groups with airborne-particle abraded zirconia surfaces after 150 days (P<.05). Both bonding systems provided durable bond strength after 3 and 150 days. Failure mode was mainly cohesive at the titanium surfaces and predominantly adhesive at the zirconia surfaces. The retention was significantly higher if APA was used versus no APA (P<.05), while the APA pressure used made no significant difference.

CONCLUSIONS

The APA of zirconia copings at a pressure of 0.1 MPa in combination with 10-MDP-containing luting composite resins and primers is adequate for the durable bonding of zirconia copings to titanium inserts.

Bond Strength Stability of Self-adhesive Resin Cement to Etched Vitrified Yttria-stabilized Tetragonal Zirconia Polycrystal Ceramic After Thermomechanical Cycling

The purpose of this study was to evaluate the influence of thermomechanical cycling on the bond strength stability of self-adhesive resin cement to vitrified yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. Y-TZP ceramic blocks were divided into four groups according to the surface treatments: AS, as sintered; SB, sandblasted with 50-μm Al2O3 particles; LG, vitrification with a low-fusing glaze and etching with 10% hydrofluoric acid; and HC, vitrification with a ceramic liner and etching with 10% hydrofluoric acid. Lithium disilicate ceramic blocks etched with 10% hydrofluoric acid for 20 seconds (EM) were also tested. Blocks of resin composite were cemented on the ceramic block surfaces using a self-adhesive resin cement. Half of the blocks from each group were cut into beams and submitted to microtensile bond strength (μTBS) testing after immersion in water at 37°C for 24 hours and the other half after mechanical (1,200,000 cycles, 98 N, 2.5 Hz) and thermal (10,000 cycles, 5-55°C, 30-second dwell time) cycling (TMC). Data were analyzed using one-way analysis of variance, Tukey's honest significant difference post hoc test, and Student t-test (α=0.05). After 24 hours, EM and LG presented similar and the highest μTBS, whereas AS showed the lowest μTBS (p&lt;0.05). After TMC, EM presented the highest μTBS, followed by LG (p&lt;0.05). Only EM and LG maintained the stability of μTBS after TMC (p&gt;0.05). The bonding to Y-TZP ceramic vitrified with a low-fusing glaze withstood thermomechanical cycling.

Does the bond strength of highly translucent zirconia show a different dependence on the airborne-particle abrasion parameters in comparison to conventional zirconia?

PURPOSE

To compare the effects of airborne-particle abrasion protocols on the surface morphology, the phase transformation and the resin bond strength of highly translucent zirconia (M) and conventional zirconia (Z).

METHODS

Thirteen groups (N = 12) of Z and M specimens were prepared. Except for the control group, the specimens were sandblasted with conditions involving different grit sizes (50 μm or 110 μm), treatment times (10 s or 20 s) and pressures (0.1 MPa, 0.3 MPa or 0.6 MPa). The surface morphology was analyzed using scanning electron microscope (SEM) and the phase analysis was conducted with X-ray diffraction (XRD). The Ra and the shear bond strength (SBS) were measured and statistically analyzed, and the failure mode was determined by optical microscope.

RESULTS

The surface morphologies were strongly dependent on treatment conditions. Larger particle size and higher pressure resulted in higher Ra for both materials. Longer blasting time resulted in higher Ra for Z but not M. Overall, the SBS increased with increasing Ra; the highest average SBS was achieved by M and exceeded 18 MPa. The monoclinic transformation was not found in any treatment for M, but was found in Z.

CONCLUSIONS

Z and M showed different dependence on the airborne-particle abrasion parameters in terms of Ra, SBS and phase transformation. The conditions for maximizing SBS included a 110 μm particle size and 20 s treatment for both, with pressures of 0.3 MPa and 0.6 MPa for the M and Z, respectively.

Effect of different surface treatments and bonding modalities on the shear bond strength between metallic orthodontic brackets and glazed monolithic zirconia crowns

OBJECTIVE

To evaluate the effect of different surface treatments and bonding modalities on the shear bond strength (SBS) between metallic orthodontic brackets and zirconia crowns.

MATERIALS AND METHODS

Sixty zirconia specimens were computer-aided design/computer-aided manufacturing milled, sintered, glazed, and embedded in acrylic resin. The specimens were divided into three groups according to the surface treatment applied: C: no surface treatment (control), S: sandblasted with 50 μm Al₂O₃, and D: Sof-Lex disc roughening. Each group was further subdivided into two subgroups according to the resin cement used: P: Clearfil Ceramic Primer + Panavia F2.0 (Kuraray) and R: RelyX U200 (3M/ESPE). Metallic orthodontic brackets were bonded to the labial surface of the specimens. All specimens underwent thermocycling. SBS test was applied using a universal test machine at a cross head speed of 1 mm/min. Data were analyzed using Mann-Whitney test (α = 0.05).

RESULTS

Subgroup SP showed the highest SBS (20.8 ± 4.8 MPa), followed by subgroups SR (16.7 ± 4.6 MPa), DP (12.3 ± 2.8 MPa), and DR (11.6 ± 3 MPa). However, all specimens in the control group underwent debonding during thermocycling. The different surface treatment groups showed highly significant differences (P < 0.05), whereas the resin cement subgroups showed no significant differences (P > 0.05).

CONCLUSION

SBS between glazed zirconia crowns and metallic brackets strongly depended on the surface treatment applied. Sandblasting achieved the highest SBS. Roughening with Sof-Lex disc proved to be a reliable surface treatment modality for glazed zirconia. Bonding to untreated glazed zirconia surfaces led to bond failure. Both resin cements yielded strong SBS results.

In vitro shear bond strength between fluorinated zirconia ceramic and resin cements

PURPOSE

The purpose of this study was to evaluate the efficiency of a gas-phase fluorination method under different fluorination periods through using two resin cements.

MATERIALS AND METHODS

84 zirconia specimens in dimensions of 5 mm × 5 mm × 2 mm were prepared and surface treated with 50 µm aluminum oxide particles or gas phase fluorination for 2 min, 5 min, or 10 min. One specimen in each group was surface analyzed under scanning electron microscope. The remaining specimens were bonded to composite cylinders in dimensions of 2 mm diameter and 3 mm high with Panavia SA Plus or Variolink N. Then, the specimens were stored in 37℃ distilled water for 24 hours and shear bond strength test was applied at a speed of 1 mm/min.

RESULTS

The highest shear bond strength values were observed in the samples fluorinated for 5 minutes and cemented with Panavia SA Plus. Variolink N did not elicit any statistical differences between surface treatments. Panavia SA Plus resin cement and Variolink N resin cements featured statistically significant difference in shear bond strength values only in the case of 5 minutes of fluorination treatment.

CONCLUSION

According to the results of this study, application of 5 minutes of fluorination with 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP) containing Panavia SA Plus resin cement increased the resin bond strength of zirconia. Fluorination of the zirconia surface using conventional resin cement, Variolink N, did not lead to an increase in bond strength.

Influence of nano alumina coating on the flexural bond strength between zirconia and resin cement

PURPOSE

The purpose of this in vitro study is to examine the effects of a nano-structured alumina coating on the adhesion between resin cements and zirconia ceramics using a four-point bending test.

MATERIALS AND METHODS

100 pairs of zirconium bar specimens were prepared with dimensions of 25 mm × 2 mm × 5 mm and cementation surfaces of 5 mm × 2 mm. The samples were divided into 5 groups of 20 pairs each. The groups are as follows: Group I (C) – Control with no surface modification, Group II (APA) – airborne-particle-abrasion with 110 µm high-purity aluminum oxide (Al₂O₃) particles, Group III (ROC) – airborne-particle-abrasion with 110 µm silica modified aluminum oxide (Al₂O₃ + SiO₂) particles, Group IV (TCS) – tribochemical silica coated with Al₂O₃ particles, and Group V (AlC) – nano alumina coating. The surface modifications were assessed on two samples selected from each group by atomic force microscopy and scanning electron microscopy. The samples were cemented with two different self-adhesive resin cements. The bending bond strength was evaluated by mechanical testing.

RESULTS

According to the ANOVA results, surface treatments, different cement types, and their interactions were statistically significant (P<.05). The highest flexural bond strengths were obtained in nanostructured alumina coated zirconia surfaces (50.4 MPa) and the lowest values were obtained in the control group (12.00 MPa), both of which were cemented using a self-adhesive resin cement.

CONCLUSION

The surface modifications tested in the current study affected the surface roughness and flexural bond strength of zirconia. The nano alumina coating method significantly increased the flexural bond strength of zirconia ceramics.

Marginal Fit and Retention Strength of Zirconia Crowns Cemented by Self-adhesive Resin Cements

The absolute marginal gap (AMG) precementation and postcementation and the retention of zirconia crowns cemented to standardized molar preparations (4×10) by self-adhesive resin cements (SARCs) were evaluated. The following SARCs were used: RelyX U-200 (RXU200; 3M ESPE, Seefeld, Germany), SmartCem 2 (SC2; Dentsply, Milford, DE, USA), and G-Cem Automix (GCA; GC, Alsip, IL, USA). The control adhesive resin cement was Panavia 21 (PAN; Kuraray Dental Co Ltd, Osaka, Japan). Twenty measuring locations at a constant interval along the margins were marked, and the AMG was measured by an image analysis system connected to a stereomicroscope (20×). The cemented copings were aged 270 days at 100% humidity and 37°C and then underwent 10,000 thermal cycles, 5°C-55°C. After aging, the crowns were tested for retention, and the debonded surfaces were examined at 3× magnification. The mean marginal gaps precementation and postcementation were 34.8 ± 17.4 μm and 72.1 ± 31 μm, respectively, with no statistically significant differences between the cements. A significant difference ( p≤0.001) in retention between the cements was found. The highest values were obtained for SC2 and GCA (1385 Pa and 1229 Pa, respectively), but these presented no statistically significant differences. The lowest values were found for PAN and RXU200 (738 Pa and 489 Pa, respectively), but these showed no statistically significant differences. The predominant mode of failure in all of the groups was mixed, and no correlations were found between marginal gap and retention.

Influence of different surface treatments on bond strength of novel CAD/CAM restorative materials to resin cement

PURPOSE

To evaluate the effects of different surface treatments on the bond strength of novel CAD/CAM restorative materials to resin cement by four point bending test.

MATERIALS AND METHODS

The CAD/CAM materials under investigation were e.max CAD, Mark II, Lava Ultimate, and Enamic. A total of 400 bar specimens (4×1.2×12 mm) (n=10) milled from the CAD/CAM blocks underwent various pretreatments (no pretreatment (C), hydrofluoric acid (A), hydrofluoric acid + universal adhesive (Scotchbond) (AS), sandblasting (Sb), and sandblasting + universal adhesive (SbS)). The bars were luted end-to-end on the prepared surfaces with a dual curing adhesive resin cement (Variolink N, Ivoclar Vivadent) on the custom-made stainless steel mold. Ten test specimens for each treatment and material combination were performed with four point bending test method. Data were analyzed using ANOVA and Tukey's test.

RESULTS

The surface treatment and type of CAD/CAM restorative material showed a significant effect on the four point bending strength (FPBS) (P<.001). For LDC, AS surface treatment showed the highest FPBS results (100.31 ± 10.7 MPa) and the lowest values were obtained in RNC (23.63 ± 9.0 MPa) for control group. SEM analyses showed that the surface topography of CAD/CAM restorative materials was modified after treatments.

CONCLUSION

The surface treatment of sandblasting or HF acid etching in combination with a universal adhesive containing MDP can be suggested for the adhesive cementation of the novel CAD/CAM restorative materials.

An insight into current concepts and techniques in resin bonding to high strength ceramics

BACKGROUND

Reliable bonding between high strength ceramics and resin composite cement is difficult to achieve because of their chemical inertness and lack of silica content. The aim of this review was to assess the current literature describing methods for resin bonding to ceramics with high flexural strength such as glass-infiltrated alumina and zirconia, densely sintered alumina and yttria-partially stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP) with respect to bond strength and bond durability.

METHODS

Suitable peer reviewed publications in the English language were identified through searches performed in PubMed, Google Search and handsearches. The keywords or phrases used were 'resin-ceramic bond', 'silane coupling agents', 'air particle abrasion', 'zirconia ceramic' and 'resin composite cements'. Studies from January 1989 to June 2015 were included.

RESULTS

The literature demonstrated that there are multiple techniques available for surface treatments but bond strength testing under different investigations have produced conflicting results.

CONCLUSIONS

Within the scope of this review, there is no evidence to support a universal technique of ceramic surface treatment for adhesive cementation. A combination of chemical and mechanical treatments might be the recommended solution. The hydrolytic stability of the resin ceramic bond should be enhanced.

The Effect of Ytterbium-Doped Fiber Laser with Different Parameters on Physical Properties of Zirconia Surface

OBJECTIVE

Laser irradiation is an alternative surface treatment method for roughening zirconia surfaces. The aim of this study was to evaluate the effects of ytterbium-doped fiber laser (YbPL) on zirconia.

BACKGROUND

Zirconia surfaces are resistant to many surface treatment methods, but surface roughness is crucial for adhesion of veneering materials and cements to zirconia.

METHODS

The zirconia discs were prepared and divided into four groups according to the power of the laser irradiation (5, 12, 17, and 20 W). These groups were divided into five subgroups according to the frequency (25, 40, 60, 80, and 100 kHz). Surface roughness values were measured with a noncontact profilometer, and the mean Ra values were calculated. Wettability was measured with a goniometer. The surface morphology was observed with a scanning electron microscope (SEM). The changes in the surface crystalline structure were analyzed with X-ray diffractometry.

RESULTS

Ra values of all groups were higher than the control group. The highest surface roughness value was at 20 W and 100 kHz. Best wettability characteristic was observed at 5 W and 60 kHz. The correlations between Ra and wettability were low but significant. SEM examination of 5 W with different frequencies showed no microcracks, however, melted areas were observed. Remaining groups had microcracks and melted layers. A significantly lower T/M-phase transformation was observed in some groups.

CONCLUSIONS

YbPL irradiation was effective at roughening the zirconia surface. Although laser treatment affected zirconia surfaces and provided surface roughness, the power and frequency should be adjusted to achieve optimum results.

Effect of Adhesive Cementation Strategies on the Bonding of Y-TZP to Human Dentin

This study evaluated the effects of different adhesive strategies on the adhesion of zirconia to dentin using conventional and self-adhesive cements and their corresponding adhesive resins. The occlusal parts of human molars (N=80) were sectioned, exposing the dentin. The teeth and zirconia cylinders (N=80) (diameter=3.4 mm; height=4 mm) were randomly divided into eight groups according to the factors “surface conditioning” and “cement type” (n=10 per group). One conventional cement (CC: RelyX ARC, 3M ESPE) and one self-adhesive cement (SA: RelyX U200, 3M ESPE) and their corresponding adhesive resin (for CC, Adper Single Bond Plus; for SA, Scotchbond Universal Adhesive-SU) were applied on dentin. Zirconia specimens were conditioned either using chairside (CJ: CoJet, 30 μm, 2.5 bar, four seconds), laboratory silica coating (RC: Rocatec, 110 μm, 2.5 bar, four seconds), or universal primer (Single Bond Universal-UP). Nonconditioned groups for both cements acted as the control (C). Specimens were stored in water (37°C, 30 days) and subjected to shear bond strength (SBS) testing (1 mm/min). Data (MPa) were analyzed using two-way analysis of variance and a Tukey test (α=0.05). While surface conditioning significantly affected the SBS values (p=0.0001) (C&lt;RC=CJ=UP), cement type did not (p=0.148) (CC=SA). The interaction terms were significant (p=0.014). Failure types were predominantly adhesive. Air-abrasion and the use of the universal primer improved the bond strength of zirconia to dentin compared to the control group, regardless of the type of resin cement used.

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

Zirconia as a Dental Biomaterial

Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different substrates, which has offered a great challenge to dental zirconia research and development. This study characterizes zirconia as a dental biomaterial, presenting the current consensus and challenges to its dental applications.