Surface analysis and shear bond strength of zirconia on resin cements after non-thermal plasma treatment and/or primer application for metallic alloys

Effect of non-thermal plasma treatment and resin cements on the bond strength of zirconia ceramics with different yttria concentrations

OBJECTIVES

To investigate the effect of different surface treatments and resin cements on the shear bond strength of zirconia ceramics with different yttria concentrations.

METHODS

Zirconia blocks characterized by different yttria concentrations [Vita YZ HT (HT), Vita YZ ST (ST) and Vita YZ XT (XT)] were used to prepare disc-shaped specimens (n=252). Specimens prepared to investigate shear bond strength (SBS), water contact angle and surface roughness (Ra) were divided into four subgroups; control (C), sandblasting (S), sandblasting + nonthermal plasma treatment (SNTP) and nonthermal plasma treatment (NTP). For SBS testing, specimens were further divided into two groups (n=108) according to the luting cement used [Panavia F2.0 (P) and Rely X U200 (R)]. The water contact angles were determined by sessile drop technique and Ra was analyzed with optical profilometer. SBS tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min. The data sets were statistically analyzed with two and three-way ANOVAs followed by post-hoc comparisons (α=0.05).

RESULTS

The water contact angle and Ra data were significantly affected by surface treatments. The mean Ra values of ST and XT were significantly lower than HT for the surface treatment groups of C and NTP. The SBS values were significantly different among the groups subjected to different surface treatments. The mean SBS values of surface treatment groups (S, SNTP and NTP) when cemented with R were significantly higher than the groups of C (p<0.05).

CONCLUSIONS

For the tested zirconia ceramics with different yttria concentrations, non-thermal plasma activation helps to improve SBS and is a promising tool in practical use.

Advances in zirconia-based dental materials: Properties, classification, applications, and future prospects

OBJECTIVES

Zirconia (ZrO2) ceramics are widely used in dental restorations due to their superior mechanical properties, durability, and ever-improving translucency. This review aims to explore the properties, classification, applications, and recent advancements of zirconia-based dental materials, highlighting their potential to revolutionize dental restoration techniques.

STUDY SELECTION, DATA AND SOURCES

The most recent literature available in scientific databases (PubMed and Web of Science) reporting advances of zirconia-based materials within the dental field is thoroughly examined and summarized, covering the major keywords "dental zirconia, classification, aesthetic, LTD, applications, manufacturing, surface treatments".

CONCLUSIONS

An exhaustive overview of the properties, classifications, and applications of dental zirconia was presented, alongside an exploration of future prospects and potential advances. This review highlighted the importance of addressing challenges such as low-temperature degradation resistance and optimizing the balance between mechanical strength and translucency. Also, innovative approaches to improve the performances of zirconia as dental material was discussed.

CLINICAL SIGNIFICANCE

This review provides a better understanding of zirconia-based dental biomaterials for dentists, helping them to make better choice when choosing a specific material to fabricate the restorations or to place the implant. Moreover, new generations of zirconia are still expected to make progress on key issues such as the long-term applications in dental materials while maintaining both damage resistance and aesthetic appeal, defining the directions for future research.

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.

Argon Plasma Treatment Effects on the Micro-Shear Bond Strength of Lithium Disilicate with Dental Resin Cements

The low bond strength of lithium disilicate (LD) ceramics to dental resin cements remains a critical issue for dental applications because it leads to frequent replacement and causes tooth tissue destruction and consumption. The objective of this study was to examine the effects of atmospheric non-thermal argon plasma (NTP) treatment on LD to improve its micro-shear bond strength (μSBS) with dental resin cements because LD mostly experiences shear stress for its commonly used dental applications as crowns or veneers. Argon plasma treatment was performed on hydrofluoric (HF) acid-etched LD surfaces, and then commercial resin cements were subsequently applied to the treated LD surfaces. The plasma treatment significantly reduced the water contact angle of the LD surface to less than 10° without changing the surface morphology. The μSBS test was performed with cement-bonded LD samples after 24 h and 30 days, as well as after 1000 cycles of thermal cycling. The test results show that, as compared with the untreated controls, 300 s of plasma treatment significantly improved the LD-resin cement bond strength by 59.1%. After 30 days of storage in DI water and 1000 cycles of thermal cycling, the plasma-treated LD samples show 84.2% and 44.8% higher bond strengths as compared to the control samples, respectively. The plasma treatment effect on LD surfaces diminished rapidly as the bond strength decreased to 25.5 MPa after aging in the air for 1 day prior to primer and cement application, suggesting that primers should be applied to the LD surfaces immediately after the plasma treatment. These results demonstrate that, when applied with caution, plasma treatment can activate LD surfaces and significantly improve the SBS of LD with dental resin cements in both short-term and long-term periods.

Ultrashort pulse laser patterning of zirconia (3Y-TZP) for enhanced adhesion to resin-matrix cements used in dentistry: An integrative review

Surface modification of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) using lasers for adhesion enhancement with resin-matrix cement has been increasingly explored. However, Y-TZP is chemically inert and non-reactive, demanding surface modification using alternative approaches to enhance its bond strength to resin-matrix cements. The main aim of this study was to conduct an integrative review on the influence of ultrashort pulse laser patterning of zirconia (3Y-TZP) for enhanced bonding to resin-matrix cements. An electronic search was performed on web of science, SCOPUS, Pubmed/Medline, Google Scholar and EMBASE using a combination of the following search items: zirconia, 3Y-TZP, surface modification, laser surface treatment, AND laser, ultrashortpulse laser, bonding, adhesion, and resin cement. Articles published in the English language, up to January 2022, were included regarding the influence of surface patterning on bond strength of Y-TZP to resin-matrix cements. Out of the 12 studies selected for the present review 10 studies assessed femtosecond lasers while 2 studies assessed picosecond lasers. Ultrashort pulsed laser surface patterning successfully produced different surface morphological aspects without damaging the bulk properties of zirconia. Contrarily, defects such as micro-cracks occurs after surface modification using traditional methods such as grit-blasting or long-pulsed laser patterning. Ultrashort pulsed laser surface patterning increase bond strength of zirconia to resin-matrix cements and therefore such alternative physical method should be considered in dentistry. Also, surface defects were avoided using ultrashort pulsed laser surface patterning, which become the major advantage when compared with traditional physical methods or long pulse laser patterning.

Influence of nonthermal argon plasma on the micro-shear bond strength between resin cement and translucent zirconia

Background

Considering the potential of translucent zirconia for application in esthetic restorations, it is necessary to find effective methods with the least adverse effects to increase its bond strength to resin cement.

Aims

This study aimed to test if different conservative surface treatments and cement types could affect the micro-shear bond strength (μSBS), failure mode, and bonding interface between resin cement and translucent zirconia.

Materials and Methods

In this in vitro experimental study, translucent zirconia blocks were divided into four groups based on the surface treatment they received: no treatment, argon plasma, primer (Pr), and Pr + plasma. Each group was further divided into two subgroups based on the applied cement: PANAVIA F2 and Duo-Link cement. Fourteen cement columns with a diameter of 1 mm were placed on each block (n = 14); all the specimens were immersed in 37°C water for 24 h. Afterward, μSBS was evaluated (P < 0.05), and the mode of failure was determined by a stereomicroscope (×10). The cement-zirconia interface and the surface hydrophilicity (contact angle) were also evaluated.

Statistical Analysis

Two-way analysis of variance (ANOVA) was used to evaluate the effect of surface preparation, cement types, and incubator, simultaneously (P < 0.05). The bond strengths after incubation were analyzed by one-way ANOVA (P < 0.05). Failure mode, contact angle, and cement-zirconia interface were analyzed descriptively.

Results

The highest bond strength was seen in Pr surface treatment for Duo-Link cement; however, this group was not significantly different from Pr and PANAVIA F2 cement and Pr + plasma and Duo-Link cement (P = 0.075) groups. All plasma specimens in the incubator failed prematurely. The mode of failure in all specimens was adhesive. The lowest and highest contact angles were seen in Pr + plasma and the control groups, respectively.

Conclusion

The use of Pr could successfully improve the bond strength of resin cement to translucent zirconia while plasma was not an acceptable and durable substitute.

Effect of Helium Plasma Exposure on Wettability and Shear Bond Strength between the Zirconia Core and Feldspathic Veneering Ceramic: An In Vitro Study

Introduction. The present study aimed to evaluate the effect of helium plasma treatment on the wettability of zirconia surface and on the shear bond strength between the dental zirconia core and feldspathic veneering ceramic. Methods. 128 zirconia specimens were prepared, polished, and then divided into four groups: control, Zr, FC, and Zr/FC. In Zr and Zr/FC groups, the zirconia blocks were treated by helium plasma for 60 s. In FC and Zr/FC, the feldspathic ceramic powder received 60 s of plasma treatment. Then, the feldspathic powder was applied on the zirconia blocks. Half of the specimens in each group were sintered in a tube furnace, and the contact angle between the zirconia core and feldspathic ceramic was measured at different time intervals. The other half were sintered in a ceramic furnace and then subjected to thermocycling. The shear bond strength was measured using a universal testing machine. The failure mode was assessed using a stereomicroscope. Data were analyzed by one-way ANOVA test, and the statistical significance was considered less than 0.05. Results. There was no significant difference in the mean contact angle and the shear bond strength values of the experimental groups ( $P>0.05$ ). The mean contact angle decreased significantly in all groups over time ( $P<0.001$ ). The modes of failure were predominantly mixed in all groups. Conclusion. The helium plasma applied on either dental zirconia core or feldspathic ceramic powder could not improve the zirconia surface wettability and the shear bond strength between the two ceramics.

The effect of nonthermal argon plasma surface treatment on the fracture resistance of monolithic zirconia restorations containing tetragonal and cubic grains

PURPOSE

The aim of this study was to investigate the effect of nonthermal argon plasma (NP) surface treatment on the fracture resistance of monolithic zirconia restorations with different microstructures.

METHODS

Twenty restorations were prepared from each of two tetragonal and two cubic zirconia materials (80 restorations in total). The restorations were then divided into two subgroups (n = 10) for each material according to the surface treatment applied: air abrasion or NP. The surface topography of the treated groups was examined using a scanning electron microscope. All restorations were fixed to metal dies with resin cement, subjected to thermal cycling, and then underwent fracture resistance testing with a universal testing device. Two-way ANOVA and Bonferroni tests were used for statistical analysis of the data (α = 0.05).

RESULTS

The type of surface treatment and the type of zirconia material were shown to significantly affect the fracture resistance of the restorations. The air-abraded groups showed significantly higher fracture resistance (N) than the NP groups (P < 0.001).

CONCLUSION

The results of this study suggest that air abrasion surface treatment has a more favorable effect on the fracture resistance of tetragonal and cubic zirconia restorations than NP surface treatment.

Antibacterial efficacy of non-thermal atmospheric plasma against Streptococcus mutans biofilm grown on the surfaces of restorative resin composites

The aim of this study was to evaluate the antimicrobial efficacy of non-thermal atmospheric plasma (NTAP) against Streptococcus mutans biofilms. Resin discs were fabricated, wet-polished, UV sterilized, and immersed in water for monomer extraction (37 °C, 24 h). Biofilms of bioluminescent S. mutans strain JM10 was grown on resin discs in anaerobic conditions for (37 °C, 24 h). Discs were divided into seven groups: control (CON), 2% chlorhexidine (CHX), only argon gas 150 s (ARG) and four NTAP treatments (30 s, 90 s, 120 s, 150 s). NTAP was applied using a plasma jet device. After treatment, biofilms were analyzed through the counting of viable colonies (CFU), bioluminescence assay (BL), scanning electron microscopy (SEM), and polymerase chain reaction (PCR). All NTAP-treated biofilm yielded a significant CFU reduction when compared to ARG and CON. BL values showed that NTAP treatment for 90 s, 120 s or 150 s resulted in statistically significantly lower metabolic activity when compared to the other groups. CHX displayed the lowest means of CFU and BL. SEM showed significant morphological changes in NTAP-treated biofilm. PCR indicated damage to the DNA structure after NTAP treatment. NTAP treatment was effective in lowering the viability and metabolism of S. mutans in a time-dependent manner, suggesting its use as an intraoral surface-decontamination strategy.

Bond durability and surface states of titanium, Ti-6Al-4V alloy, and zirconia for implant materials

PURPOSE

Screw-retained implant crowns used as dental implants comprise a zirconia coping and titanium base bonded using resin cement. These devices are prone to debonding failures. This study investigated the bond characteristics of implant materials based on shear bond strength (SBS) and surface characteristics.

METHODS

Chemically pure (CP) titanium grade-4 (Ti), Ti-6Al-4V alloy (Ti-6Al-4V), and tetragonal polycrystalline zirconia (zirconia) were evaluated as adherent materials. Plates of each material were polished, primed for the respective resin cements, and cemented using either methyl methacrylate-based resin cement (Super-Bond) or composite-based resin cement (Panavia). The cemented samples were subjected to 10,000 thermocycles alternating between 5 and 55 °C, and the SBS were obtained before and after thermocycling. The sample surfaces were characterized based on surface observations, roughness, and free energy (SFE).

RESULTS

The SBSs of all materials bonded using Panavia were significantly compromised during thermocycling and reached zero. Although the SBSs of Ti and Ti-6Al-4V bonded using Super-Bond were not significantly affected by thermocycling, those of zirconia decreased significantly. The bond durability between zirconia and Super-Bond was improved via alumina air-abrasion, which caused no significant loss of SBS after thermocycling. Surface analyses of the air-abraded zirconia validated these results and confirmed that its surface roughness and SFE were significantly increased.

CONCLUSIONS

The bond durability between resin cement and zirconia was lower than that between Ti and Ti-6Al-4V. The alumina air-abrasion pretreatment of zirconia improved the SFE and surface roughness, thereby enhancing bond durability.

Influence of Non-Thermal Atmospheric Pressure Plasma Treatment on Retentive Strength between Zirconia Crown and Titanium Implant Abutment

The aim of this study is to investigate the effect of non-thermal atmospheric pressure plasma (NTP) on retentive strength (RS) between the zirconia crown and the titanium implant abutment using self-adhesive resin cement. Surface free energy (SFE) was calculated on 24 cube-shaped zirconia blocks, and RS was measured on 120 zirconia crown-titanium abutment assemblies bonded with G-CEM LinkAce. The groups were categorized according to the zirconia surface treatment as follows: Control (no surface treatment), NTP, Si (Silane), NTP + Si, Pr (Z-Prime Plus), and NTP + Pr. Half of the RS test assemblies were aged by thermocycling for 5000 cycles at 5–55 °C. The SFE was calculated using the Owens-Wendt method, and the RS was measured using a universal testing machine at the maximum load until failure. One-way analysis of variance (ANOVA) with post-hoc Tukey honestly significant difference (HSD) was performed to evaluate the effect of surface treatments on the SFE and RS. Independent sample t-test was used to compare the RS according to thermocycling (p < 0.05). For the SFE analysis, the NTP group had a significantly higher SFE value than the Control group (p < 0.05). For the RS test, in non-thermocycling, the NTP group showed a significantly higher RS value than the Control group (p < 0.05). However, in thermocycling, there was no significant difference between the Control and NTP groups (p > 0.05). In non-thermocycling, comparing with the NTP + Si or NTP + Pr group, there was no significant difference from the Si or Pr group, respectively (p > 0.05). Conversely, in thermocycling, the NTP + Si and NTP + Pr group had significantly lower RS than the Si and Pr group, respectively (p < 0.05). These results suggest that NTP single treatment for the zirconia crown increases the initial RS but has little effect on the long-term RS. Applied with Silane or Z-Prime Plus, NTP pre-treatment has no positive effect on the RS.

Effect of cementation delay on bonding of self-adhesive resin cement to yttria-stabilized tetragonal zirconia polycrystal ceramic treated with nonthermal argon plasma

STATEMENT OF PROBLEM

Nonthermal argon plasma (NTAP) has been reported to improve the bond strength of resin cements to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics. However, the effect of the inevitable delay before cementation and after treating Y-TZP ceramics with NTAP is unclear.

PURPOSE

The purpose of this in vitro study was to investigate whether delays of 8, 12, and 24 hours between the Y-TZP ceramic treatment with NTAP and the cementation would affect the surface energy and the bond strength of a self-adhesive resin cement to Y-TZP ceramic.

MATERIAL AND METHODS

Sixty plates and 50 blocks of 3Y-TZP ceramic were divided into 2 groups (n=30 and n=25): as-sintered (AS) and airborne-particle abraded with 50-μm Al₂O₃ (APA). These groups were further divided into 5 subgroups (n=6 and n=5) according to the delay between the NTAP treatment and the measurement of surface energy and microtensile bond strength (μTBS) evaluation: (0, 8, 12, and 24 hours). For both 3Y-TZP surface conditions (AS and APA), a control group without NTAP treatment was used (ASC and APAC). The surface energy (SE) was evaluated with a goniometer and the 3Y-TZP elemental composition with X-ray photoelectron spectroscopy (XPS). For the μTBS test, the 3Y-TZP ceramic blocks were cemented to composite resin blocks with a self-adhesive resin cement. After storage in distilled water at 37 °C for 24 hours, the 3Y-TZP-composite resin blocks were sectioned into beams and submitted to a μTBS test. Data were submitted to 2-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

For the AS group, NTAP increased the SE irrespective of the delay before measurement: ASC<0 hour=8 hours=12 hours=24 hours (P<.05). For the APA group, except after 12 hours, NTAP also increased the surface energy (P<.05). XPS analysis showed an increase in the oxygen/carbon ratio after NTAP treatment for both groups. For the AS group, NTAP increased the μTBS after 0, 8, and 12 hours (P<.05), whereas for the APA group this occurred only after 8 hours (P<.05). For the AS and APA groups, the highest μTBS was reached after 8 hours (P<.05).

CONCLUSIONS

Treatment of 3Y-TZP ceramic with NTAP improved the SE and increased the μTBS of self-adhesive resin cement to 3Y-TZP ceramic. These effects were time dependent, with better results at 8 hours after NTAP treatment.

Effect of Non-Thermal Atmospheric Pressure Plasma (NTP) and Zirconia Primer Treatment on Shear Bond Strength between Y-TZP and Resin Cement

The purpose of this study was to investigate the effect of non-thermal atmospheric pressure plasma (NTP) treatment on the sandblasting of mechanical method and zirconia primer of chemical method used to increase the bond strength between zirconia and resin cement. In this study, Y-TZP was divided into 4 groups according to the surface treatment methods as follows: Zirconia primer (Pr), NTP + Zirconia primer (NTP + Pr), Sandblasting + Zirconia primer (Sb + Pr), Sandblasting + NTP + Zirconia primer (Sb + NTP + Pr). Then, two types of resin cement (G-CEM LinkAce and Rely X-U200) were used to measure the shear bond strength (SBS) and they were divided into non-thermal cycling group and thermal cycling group for aging effect. Statistical analyses were performed using the Kruskal-Wallis test and Mann-Whitney U test. The result of the surface energy (SE), there was no significant difference among the groups (p > 0.05). As a result of the SBS test, the Sb + Pr group had a significantly higher SBS value than the other groups regardless of the resin cement type (p < 0.05), and the decrease rate after thermal cycling treatment was the lowest. On the other hand, the NTP + Pr group showed significantly lower SBS values than the other groups except for the case of using Rely X-U200 (p < 0.05), and the reduction rate after thermal cycling was the highest. The Sb + NTP + Pr group did not differ significantly from the Pr group (p > 0.05). Within the limitations of two successive studies, treatment with NTP after sandblasting used for mechanical bond strength showed a positive effect on initial SBS. However, when NTP was treated before the zirconia primer used for the chemical bond strength, it showed a negative effect on SBS compared to other treatment methods, which was noticeable after the thermal cycling treatment.

Yttria-stabilized tetragonal zirconia polycrystal/resin luting agent bond strength: Influence of Titanium dioxide nanotubes addition in both materials

PURPOSE

To evaluate the shear bond strength (SBS) between Y-TZP and a resin luting agent, after 1 of 2 enhancing strategies with TiO_2--nts was applied, either to the resin luting agent or the Y-TZP mass, in different concentrations.

METHODS

In the Strategy TiO₂-nts on ceramic, the resin luting agent Panavia F2.0™ (Kuraray) and an experimental Y-TZP with added concentrations of TiO_2--nts (0%, 1%, 2%, and 5% vol/vol) and a commercial Y-TZP, comprised 5 different groups (n = 10). In the Strategy TiO₂-nts on cement, the resin luting agent RelyX U200™ (3 M ESPE) was added with different concentrations of TiO_2--nts (0%, 0.3%, 0.6%, 0.9% wt/wt) luted to a commercial Y-TZP, comprising 4 different groups (n = 10). The Y-TZP discs were included in acrylic bases, and a cylinder (3 × 3 mm) of the correspondent luting agent for each respective group was applied over them. After 24 h, specimens were subjected to SBS assessments in a universal testing machine. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy analyses were also performed on Y-TZP surfaces. Data were analyzed via analysis of variance and Tukey tests (α = 0.05).

RESULTS

TiO₂-nts on ceramic influenced the bond strength significantly, but not linearly; TiO₂-nts on cement did not influence bond strength when analyzed separately, nor in comparison with the first.

CONCLUSION

Y-TZP enhancements with TiO₂-nts led to a higher SBS with Panavia F2.0, a 5% TiO_2--nt concentration presented the highest bond strength. Modified Rely X U200 did not improve SBS.

Shear bond strength of zirconia to resin: The effects of specimen preparation and loading procedure

PURPOSE

Shear bond strength (SBS) test is the most commonly used method for evaluating resin bond strength of zirconia, but SBS results vary among different studies even when evaluating the same bonding strategy. The purpose of this study was to promote standardization of the SBS test in evaluating zirconia ceramic bonding and to investigate factors that may affect the SBS value of a zirconia/resin cement/composite resin bonding specimen.

MATERIALS AND METHODS

The zirconia/resin cement/composite resin bonding specimens were used to simulate loading with a shear force by the three-dimensional finite element (3D FE) modeling, in which stress distribution under uniform/non-uniform load, and different resin cement thickness and different elastic modulus of resin composite were analyzed. In vitro SBS test was also performed to validate the results of 3D FE analysis.

RESULTS

The loading flat width was an important affecting factor. 3D FE analysis also showed that differences in resin cement layer thickness and resin composite would lead to the variations of stress accumulation area. The SBS test result showed that the load for preparing a SBS specimen is negatively correlated with the resin cement thickness and positively correlated with SBS values.

CONCLUSION

When preparing a SBS specimen for evaluating bond performance, the load flat width, the load applied during cementation, and the different composite resins used affect the SBS results and therefore should be standardized.

Influence of Non-Thermal Atmospheric Pressure Plasma Treatment on Shear Bond Strength between Y-TZP and Self-Adhesive Resin Cement

The purpose of this study was to evaluate the effect of non-thermal atmospheric pressure plasma (NTP) on shear bond strength (SBS) between yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and self-adhesive resin cement. For this study, surface energy (SE) was calculated with cube-shaped Y-TZP specimens, and SBS was measured on disc-shaped Y-TZP specimens bonded with G-CEM LinkAce or RelyX U200 resin cylinder. The Y-TZP specimens were classified into four groups according to the surface treatment as follows: Control (no surface treatment), NTP, Sb (Sandblasting), and Sb + NTP. The results showed that the SE was significantly higher in the NTP group than in the Control group (p < 0.05). For the SBS test, in non-thermocycling, the NTP group of both self-adhesive resin cements showed significantly higher SBS than the Control group (p < 0.05). However, regardless of the cement type in thermocycling, there was no significant increase in the SBS between the Control and NTP groups. Comparing the two cements, regardless of thermocycling, the NTP group of G-CEM LinkAce showed significantly higher SBS than that of RelyX U200 (p < 0.05). Our study suggests that NTP increases the SE. Furthermore, NTP increases the initial SBS, which is higher when using G-CEM LinkAce than when using RelyX U200.

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.

Different surface modifications combined with universal adhesives: the impact on the bonding properties of zirconia to composite resin cement

OBJECTIVE

The purpose of this study was to analyze the impact of plasma treatment and (universal adhesives) UAs on the bonding properties of zirconia.

MATERIAL AND METHODS

Zirconia specimens (N = 744; n = 186/pretreatment) were prepared, highly polished, and pretreated: (i) plasma (oxygen plasma, 10s, 5 mm), (ii) airborne-particle abrasion (alumina, 50 μm, 0.05 MPa, 5 s, 10 mm), (iii) airborne-particle abrasion + plasma, and (iv) without pretreatment (highly polished surface). Surface roughness (R_a) and surface free energy (SFE) were measured (n = 6/pretreatment). Tensile bond strength (TBS) specimens (n = 180/pretreatment) were further divided (n = 18/conditioning): Clearfil Ceramic Primer (PCG), All-Bond Universal (ABU), Adhese Universal (AU), Clearfil Universal Bond (CUB), G-Premio Bond (GPB), Futurabond U (FBU), iBond Universal (IBU), One Coat 7 Universal (OCU), Scotchbond Universal (SBU), and no conditioning. PCG was luted with Panavia F2.0 and the remaining groups with DuoCem. After storage in distilled water (24 h; 37 °C) and thermocycling (5000×; 5 °C/55 °C), TBS was measured and fracture types (FTs) were determined. Data were analyzed using univariate ANOVA with a partial eta square (ƞ_P²), the Kruskal-Wallis H, the Mann-Whitney U, and the Chi² test (P < .05).

RESULTS

Plasma treatment resulted in an increase of SFE but had no impact on R_a. Airborne-particle abrasion resulted in the highest R_a and a higher TBS when compared with plasma and non-treatment. SBU and AU obtained a higher TBS when compared with PCG. OCU, FBU, ABU, IBU, and GPB indicated comparable TBS to PCG. CUB revealed the lowest TBS.

CONCLUSIONS

Plasma treatment cannot substitute airborne-particle abrasion when bonding zirconia but MDP-containing adhesives are essential for successful clinical outcomes.

CLINICAL RELEVANCE

Airborne-particle abrasion with a low pressure (0.05 MPa) in combination with UAs promotes the clinical success of adhesively bonded zirconia restorations.

Effect of Plasma Treatment and Its Post Process Duration on Shear Bonding Strength and Antibacterial Effect of Dental Zirconia

We have investigated the effect of non-thermal atmospheric pressure plasma (NTAPP) treatment and the post process time on the bonding strength and surface sterilization of dental zirconia. Presintered zirconia specimens were manufactured as discs, and then subjected to a 30-min argon treatment (Ar, 99.999%; 10 L/min) using an NTAPP device. Five post-treatment durations were evaluated: control (no treatment), P0 (immediate), P1 (24 h), P2 (48 h), and P3 (72 h). The surface characteristics, shear bonding strength (SBS) with two resin cements, and Streptococcus mutans biofilm formation of these plasma-treated dental zirconia were tested. Plasma did not change the roughness, and caused surface element changes and surface energy increase. Due to this increase in surface energy, SBS increased significantly (p < 0.05) within 48 h when RelyX^TM U200 was used. However, the increase of surface oxygen significantly decreased (p < 0.05) the SBS of Panavia F 2.0 when using plasma immediately (P0). S. mutans adhesion decreased significantly (p < 0.05) for the P0, P1, and P2 groups compared to the control. The P0 group exhibited lower biofilm thickness than the other experimental groups due to the increased hydrophilicity (p < 0.05). Our study suggests that there is a suitable time window for the post NTAPP treatment regarding bonding strength and antimicrobial growth persist.

Effect of different times of nonthermal argon plasma treatment on the microtensile bond strength of self-adhesive resin cement to yttria-stabilized tetragonal zirconia polycrystal ceramic

STATEMENT OF PROBLEM

Nonthermal argon plasma may increase the surface energy of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) dental ceramics. However, studies that evaluated the effect of increased plasma treatment times on the bond strength of resin cements to Y-TZP ceramics are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of different nonthermal argon plasma (NTAP) treatment times on the surface energy and bond strength of a self-adhesive resin cement to Y-TZP ceramic.

MATERIAL AND METHODS

Forty-eighty Y-TZP plates were divided into 2 groups (n=24): as-sintered (AS) and airborne-particle abrasion (APA) with 50-μm Al₂O₃, which were subdivided into 4 groups (n=6) according to the time of NTAP treatment: 0, 20, 60, and 120 seconds. The surface energy was evaluated with a goniometer. Forty Y-TZP blocks submitted to the same surface treatments (8 groups; n=5) were cemented to composite resin blocks, using a self-adhesive resin cement. After storage in distilled water at 37°C for 24 hours, the Y-TZP-composite resin blocks were cut into beams and submitted to a microtensile bond strength (μTBS) test. Data were analyzed using 2-way ANOVA and the Tukey honestly significant differences test (α=.05).

RESULTS

Treatment with NTAP increased the surface energy for AS and APA groups (P<.05). For both groups, the μTBS was as follows: 0 seconds < 20 seconds < 60 seconds = 120 seconds (P<.05). Only after 120 seconds of NTAP treatment was the μTBS of APA higher than that of AS (P<.05).

CONCLUSIONS

Treatment with NTAP improved the surface energy and increased the μTBS of self-adhesive resin cement to Y-TZP ceramic, with higher times of plasma treatment resulting in higher bond strength.

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.