Surface characterisation and bonding of Y-TZP following non-thermal plasma treatment

Different surface treatments and adhesive monomers for zirconia-resin bonds: A systematic review and network meta-analysis

This review examined the efficacy of surface treatments and adhesive monomers for enhancing zirconia-resin bond strength. A comprehensive literature search in PubMed, Embase, Web of Science, Scopus, and the Cochrane Library yielded relevant in vitro studies. Employing pairwise and Bayesian network meta-analyses, 77 articles meeting inclusion criteria were analyzed. Gas plasma was found to be ineffective, while treatments including air abrasion, silica coating, laser, selective infiltration etching, hot etching showed varied effectiveness. Air abrasion with finer particles (25-53 µm) showed higher immediate bond strength than larger particles (110-150 µm), with no significant difference post-aging. The Rocatec silica coating system outperformed the CoJet system in both immediate and long-term bond strength. Adhesives containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) were superior to other acidic monomers. The application of 2-hydroxyethyl methacrylate and silane did not improve bonding performance. Notably, 91.2 % of bonds weakened after aging, but this effect was less pronounced with air abrasion or silica coating. The findings highlight the effectiveness of air abrasion, silica coating, selective infiltration etching, hot etching, and laser treatment in improving bond strength, with 10-MDP in bonding agents enhancing zirconia bonding efficacy.

Nonthermal Atmospheric Plasma Promotes Bonding Between Adhesive Monomers and Zirconia

OBJECTIVE

To investigate whether nonthermal atmospheric plasma (NTAP) can promote bonding between commonly used adhesive monomers and zirconia.

MATERIALS AND METHODS

The zirconia surface and monomers (HEMA, BisGMA, TEGDMA, and MDP) were treated with different NTAP approaches (10 w, 30 s), and the surface characteristics and chemical structures between the zirconia surface and monomers were verified by the contact angle, scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared (ATR/FT-IR) spectroscopy, and x-ray photoelectron spectroscopy (XPS). Scotchbond Universal adhesive with two different resin cements, RelyX Ultimate and RelyX Unicem 2, was applied, followed by NTAP-aided clinical procedures, and then microtensile bond strength test (μTBS) and failure mode evaluation were tested for preliminary mechanical properties assessment. One-way ANOVA was employed for the statistical analysis.

RESULTS

The contact angle analysis, SEM, and ATR-FTIR confirmed that NTAP can promote the polymerization of BisGMA, TEGDMA, and MDP on the zirconia surface, while XPS confirmed that NTAP can induce a chemical reaction between MDP and zirconia.

CONCLUSIONS

Nonthermal atmospheric plasma can increase the affinity between selected monomers and zirconia and promote the chemical bonding strength between phosphate monomers and zirconia; besides, it can enhance the bonding strength of two different adhesive systems.

CLINICAL SIGNIFICANCE

The mechanism of how NTAP improved common adhesive monomers interacting with zirconia surfaces was revealed in this study. NTAP, as a relatively high energy-boosting method, could not only improve the surface affinity of zirconia and chemical bonding in-between monomers and zirconia but also enhance the polymerization of different monomers onto zirconia, resulting in improved bonding properties. Thus, further exploration of versatile bonding materials and/or onto different dental substrates could take this into account.

Impact of Different Surface Treatments on Shear Bond Strength between Two Zirconia Ceramics and a Composite Material

The purpose of this study was to compare the surface changes and shear bond strength between a resin composite and two zirconia ceramics subjected to sandblasting and forming gas (5% H2 in N2) plasma surface treatment. Two types of zirconia ceramic specimens (3Y-TZP and (Y,Nb)-TZP) were divided into groups based on the following surface treatment methods: polishing (Control), sandblasting (SB), sandblasting and plasma (SB-P), and plasma treatment (P). Subsequently, chemical surface modification was performed using Clearfil SE Bond (Kuraray, Tokyo, Japan), and the Filtek Z-250 (3M, Maplewood, MN, USA) resin composite was applied. Shear bond strengths (SBS) and surface characteristics were determined. Plasma treatment was effective in increasing the wettability. For SBS, there were significant differences among the groups, and the (Y,Nb)-TZP and SB-P groups showed the highest bond strength. Similarly, for the 3Y-TZP specimens, the shear bond strength increased with both plasma and sandblasting treatments, although no statistically significant change was observed. In the P group, both (Y,Nb)-TZP and 3Y-TZP showed a significant decrease in shear bond strength with the resin composite compared to the control group.

Effects of plasma surface treatment on the bond strength of zirconia with an adhesive resin luting agent

The purpose of this study was to evaluate the effect of the atmospheric pressure plasma treatment as a surface treatment method on the contact angle and shear bond strength (SBS) of zirconia ceramics and the failure mode between the self-adhesive resin luting agent and zirconia. The zirconia specimens were divided into eight groups based on the surface treatment method: alumina blasting, air plasma, argon plasma (AP), Katana cleaner, ozonated water, ozonated water+AP, Katana cleaner+AP, and tap water+AP. The contact angles, SBS, and fracture modes were tested. AP treatment significantly reduced the contact angle (p<0.0001). The combination of AP and other cleaning methods showed a higher bond strength and more mixed fractures. Our findings indicate that using atmospheric pressure plasma with argon gas, combined with other cleaning methods, results in a stronger bond than when using alumina blasting alone.

Effects of different plasma treatments on bonding properties of zirconia

This in vitro study was to evaluate the effect of different non-thermal atmospheric pressure plasma (NTP) on shear bond strength (SBS) between yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and self-adhesive resin cement. In this study, The Y-TZP specimens were divided into 4 groups according to the surface treatment methods as follows: Control (no surface treatment), Sb (Sandblasting), AP(argon NTP), and CP(20 % oxygen and 80 % argon combination NTP). Y-TZP specimens were randomly selected from each group to observe and test the following indexes: scanning electron microscope to observe the surface morphology; atomic force microscope to detect the surface roughness; contact angle detector to detect the surface contact angle; energy spectrometer to analyze the surface elements. Then, resin cement (Rely X-U200) was bonded to human isolated teeth with Y-TZP specimens to measure SBS. The results showed that for the SE test, the NTP group was significantly higher than the control group (p < 0.05). The results of the SBS test showed that the SBS values of the NTP group were significantly higher than those of the other groups, regardless of the plasma treatment (p < 0.05). However, there was no significant difference between groups AP and CP in a test of SBS (p > 0.05). This study shows that non-thermal atmospheric pressure plasma can improve the shear bond strength of Y-TZP by increasing the surface energy. The addition of oxygen ratio to argon is more favorable to increase the shear bond strength and is worth further investigation.

Dental silicate ceramics surface modification by nonthermal plasma: A systematic review

OBJECTIVES

Nonthermal atmospheric or low-pressure plasma (NTP) can improve the surface characteristics of dental materials without affecting their bulk properties. This study aimed to systematically review the available scientific evidence on the effectiveness of using NTP for the surface treatment of etchable, silica-based dental ceramics before cementation, and elucidate its potential to replace the hazardous and technically demanding protocol of hydrofluoric acid (HF) etching.

METHODS

A valid search query was developed with the help of PubMed's Medical Subject Headings (MeSH) vocabulary thesaurus and translated to three electronic databases: PubMed, Web of Science, and Scopus. The methodological quality of the studies was assessed according to an adapted version of the Methodological Index for Non-Randomized Studies (MINORS).

RESULTS

Thirteen in vitro study reports published between 2008 and 2023 were selected for the qualitative and quantitative data synthesis. The implemented methodologies were diverse, comprising 19 different plasma treatment protocols with various device settings. Argon, helium, oxygen, or atmospheric air plasma may significantly increase the wettability and roughness of silicate ceramics by plasma cleaning, etching, and activation, but the treatment generally results in inferior bond strength values after cementation compared to those achieved with HF etching. The technically demanding protocol of plasma-enhanced chemical vapor deposition was employed more commonly, in which the surface deposition of hexamethyl disiloxane with subsequent oxygen plasma activation proved the most promising, yielding bond strengths comparable to those of the positive control. Lack of power analysis, missing adequate control, absence of examiner blinding, and non-performance of specimen aging were common methodological frailties that contributed most to the increase in bias risk (mean MINORS score 15.3 ± 1.1).

SIGNIFICANCE

NTP can potentially improve the adhesive surface characteristics of dental silicate ceramics in laboratory conditions, but the conventional protocol of HF etching still performs better in terms of the resin-ceramic bond strength and longevity. More preclinical research is needed to determine the optimal NTP treatment settings and assess the aging of plasma-treated ceramic surfaces in atmospheric conditions.

Atmospheric plasma treatment: an alternative of HF etching in lithium disilicate glass-ceramic cementation

Objectives: This study aimed to investigate whether the atmospheric pressure plasma jet (APPJ) could modify the surface of lithium disilicate glass ceramics (LDC) instead of hydrofluoric acid (HF) in LDC resin cementation. Methods: Two hundred and thirty-two LDC blocks were randomly divided into seven groups: Group 1 (16 specimens) was the blank control group (without HF or APPJ treatment); Group 2 (36 specimens) was etched by HF; Groups 3-7 (36 specimens each) were treated with APPJ, and the relative air humidity (RAH) of the discharge was 22.8%, 43.6%, 59.4%, 75.2%, and 94.0%, respectively. Three LDC blocks in each group were characterized via X-ray photoemission spectroscopy (XPS) analyses, 3 blocks via contact angle measurements, and other 10 blocks via surface roughness measurements. The residual LDC blocks in groups 2-7 were cemented to composite cylinders. Testing the cemented specimens' shear bond strength (SBS) before and after thermocycling (6,500 cycles of 5°C and 55°C) revealed fracture patterns. Data were analyzed by ANOVA (post hoc: Bonferroni) (α = 0.05). Results: After APPJ treatment, the water contact angle values of APPJ treated blocks dropped from 31.37° to 5.66°, while that of HF etched ones dropped to 18.33°. The O/C ratio increased after HF etching or APPJ treatment according to the calculated results, except for the APPJ-treated samples at a RAH of 22.8%. The surface roughness of LDC blocks showed no statistic difference before and after APPJ treatment, but experienced significant difference after HF etching. The O/Si and O/C ratios varied after HF etching or APPJ treatment. No significant difference in SBS values could be found among groups 2-7 before or after artificial aging (p > 0.05). All specimens showed mixed failure patterns. Conclusion: The APPJ treatment method reported in this study is a promising novel strategy for surface modification of the LDC. With acceptable bonding strength, it might be an alternative to HF in LDC-resin cementation.

Effect of Surface Treatments with Low-Pressure Plasma on the Adhesion of Zirconia

The purpose of this study was to investigate the effect of low-pressure plasma on the contact angle, shear bond strength (SBS), and the failure mode of zirconia ceramic. Zirconia specimens were divided into three groups according to the surface treatment methods as follows: sandblasting with aluminum oxide (ZR-C), sandblasting with aluminum oxide and oxygen plasma (ZR-CP), and argon plasma (ZR-P). The contact angle, SBS, and surface characteristics were tested after thermocycling. Data analysis was made using the Kruskal-Wallis test and one-way analysis of variance. Plasma treatment significantly reduced the contact angle (p < 0.001) with the lowest value for the Zr-P group. An increase in oxygen and a decrease in carbon was observed on the zirconia surface in both plasma groups. For the SBS, there were significant differences among the groups (p < 0.018), the Zr-CP group showing the highest bond strength. Mixed failures were the most frequent. Plasma treatment was effective in increasing the wettability, increasing the oxygen/carbon ratio without changing zirconia surface morphology. The sandblasting plus plasma with oxygen group exhibited the highest bond strength.

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.

Effect of Nonthermal Plasma on Shear Bond Strength of Translucent Zirconia in Layering Ceramic

Background

Today, various methods are used to increase the bond strength of zirconia in layering ceramics. This study evaluated the effects of nonthermal argon plasma on zirconia shear bond strength to layering porcelain. Materials and Method. In this experimental study, 42 square blocks of zirconia were prepared and randomly divided into three groups (n = 14) according to the applying surface treatment: (1) the control group (without any surface treatment), (2) the plasma-treated group with argon nonthermal plasma, and (3) the air abrasion group with 50 µm Al₂O₃ particles. All samples were layered with porcelain. One sample from each group was evaluated by electron microscopy (SEM) to examine the cross-sectional area of the zirconia-ceramic bond. The rest of the specimens were subjected to thermocycling with 5,000 baths to imitate the aging process in the mouth and then were tested for shear bond strength. The failure pattern of the samples was examined by stereomicroscope. Bond strength data were analyzed by one-way ANOVA test in three groups and Tamhane post hoc test in pairs. The significance level of p-value was considered 0.05.

Results

The shear bond strength of the plasma-treated group was significantly higher than the control group (p = 0.032) but the shear bond strength between the sandblast and the plasma-treated group was not significantly different (p = 0.656). The shear bond strength between the sandblast and the control group was also not significant (p = 0.202). Regarding the mode of failure, failures were mostly adhesive and then mixed. Examination of the samples under SEM showed that the bond area is the thickest in the sandblast group and also the surface roughness is the highest in the sandblast group and the lowest in the control group.

Conclusion

This study demonstrated that the use of nonthermal argon plasma treatment is an effective way to enhance the quality and quantity of shear bond strength between layering porcelain and zirconia.

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.

Influence of cold atmospheric-pressure-plasma in combination with different pretreatment methods on the pull-off tensile load in two-piece abutment-crowns: an in-vitro study

BACKGROUND

In implant prosthetic dentistry, the adhesive connection of individualized ceramic crowns and prefabricated titanium bases leads to several benefits. However, the durability of the bonding could be a weak point and especially depends on sufficient surface pretreatment. Cold atmospheric-pressure plasma (CAP) is a pretreatment method that should improve the surface properties without physical damage. Thus, the purpose of this study was to investigate the influence of CAP treatment on pull-off tensile load in two-piece abutment crowns.

METHODS

Eighty zirconia crowns and titanium bases were divided into eight groups (n = 10) according to their surface pretreatment prior to cementation with Panavia V5: no treatment (A); sandblasting (B); 10-MDP primer (C); sandblasting and primer (D); CAP (AP); sandblasting and CAP (BP); CAP and primer (CP); sandblasting, CAP and primer (DP). The specimens were thermocycled (5°/55°, 5000 cycles), and then the pull-off tensile load (TL) was measured. Statistical analyses were performed using three-way ANOVA with Tukey post-hoc and Fisher's exact tests.

RESULTS

The results showed that the TL was highest in group D (p < 0.0001). Some combinations of different treatments led to effects that were greater than the sum of the individual effects. These effects were modified by interactions. Only in combination with primer, CAP treatment had a small but positive significant effect (group CP vs. C and CP vs. AP, p < 0.0001) which however did not come close to the strong interaction effect that resulted from the combination of sandblasting and primer.

CONCLUSION

Within the limitations of this study, CAP treatment cannot be recommended in this specific field of indication due to its unreliable influence on TL in combination with other pretreatment methods.

Influence of Lithium disilicate pretreatment using photodynamic therapy, non-thermal plasma, and laser treatment on surface roughness and bond strength

AIMS

To assess the shear bond strength (SBS) and surface roughness (Ra) of lithium disilicate ceramic (LDC) after using different pretreatment methods i.e., Non-Thermal Plasma (NTP), self-etching ceramic primer (SECP), curcumin photosensitizer (CP), Er and Cr: YSGG lasers (ECL) in comparison to hydrofluoric acid + Silane (HF + S) MATERIALS AND METHODS: : A total of fifty LDC discs were prepared. All the discs were arbitrarily divided into five groups based on the surface conditioning used (n=10). Group 1: PDT+S, group 2: HF+ S, group 3: NTP + S, group 4: SECP, and group 5: ECL+ S. A confocal optical microscope was used to calculate Ra for each sample. A self-adhesive resin cement was applied followed by LED light curing. A universal testing machine was used to assess SBS and a stereomicroscope was used to determine the failure mode. Two-way analysis of variance (ANOVA), and a Tukey post hoc test was used to analyze data (p=0.05) RESULTS: : The highest bond integrity of resin luting bonded to conditioned LDS ceramics were presented by group 2 (HF+ S) (21.48±1.39 MPa) and lowest by group 1 (CP+S) (13.01±1.19 MPa) respectively. Intergroup comparison analysis revealed that group 1(13.01±1.19 MPa) and group 3 (14.28±0.62 MPa) displayed comparable outcomes of bond integrity(p>0.05). Similarly, it was observed that group 2 (21.48±1.39 MPa) and group 5 (21.31±1.85MPa) exhibited comparable values of bond strength(p>0.05). Specimens conditioned with HF+ S showed the highest Ra (1445.86±0.019µm). However, discs treated with SECP exhibited the lowest Ra (0139.76±0.081µm) CONCLUSION: Er, Cr: YSGG laser retains the ability to be used as an LDC surface conditioner as an alternative to HF+ S.Both the methods of pretreatment results in high surface roughness of LDC.

The effect of surface treatments on the adhesive bond in all-ceramic dental crowns using four-point bending and dynamic loading tests

The aim of this study was to determine the effect of sandblasting, grinding and plasma treatment on the adhesive bond strength between framework ceramic (Y-TZP) and veneering ceramic (feldspar ceramic). Therefore, four-point bending specimens (n = 180) were cut from densely sintered 3Y-TZP blanks. Subsequently, 80 of these samples received surface treatment by sandblasting and 80 samples by grinding. A reference group (20 samples) was not processed. Half of the specimens that received a surface treatment were additionally exposed to an oxygen plasma treatment. After processing, all specimens were manually veneered with feldspar ceramic and examined with a four-point bending test to evaluate the strain energy release rate G. The surface treatment parameters that achieved the highest and lowest G were transferred to real geometries of a posterior crown (n = 45). The crowns' ceramic framework was sandblasted and veneered by hand. The all-ceramic crowns were tested in a dynamic loading test and Wöhler curves were evaluated. Four-point bending samples blasted at an angle of 90° at 6 bar and a working distance of 1.5 cm without plasma treatment achieved the highest energy release rate. Samples blasted at an angle of 90° at 2 bar and a working distance of 1 cm with plasma treatment achieved the lowest energy release rate. Overall, plasma treatment did not improve bond strength. In the dynamic loading test, the group blasted with 2 bar showed the best results.

Effect of nonthermal argon plasma treatment on the surface properties and phase transformation of zirconia

PURPOSE

This study aims to evaluate the effect of applying different parameters of nonthermal argon plasma (NTAP) on the surface roughness and phase transformation of yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics.

METHODS

A total of 60 zirconia samples were prepared and randomly divided into six groups according to their surface treatments (n = 10). Group 1: control group; Group 2: argon plasma with a flow rate of 5 lt/min for 4 min; Group 3: 8 lt/min for 4 min; Group 4: 8 lt/min for 2 min; Group 5: 5 l/min for 2 min; Group 6: air abrasion with Al2O3 particle. The surface roughness was measured with a profilometer, and surface topography was observed using scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was performed to investigate the phase transformation.

RESULTS

The air abrasion group showed the highest surface roughness. The lowest relative monoclinic phase amount (Xm) was observed in the control group (0.4%), and the highest Xm value was observed in group 6 (7.8%).

CONCLUSION

While the air abrasion group showed the highest average surface roughness, it also caused the highest phase transformation. With a flow rate of 8 lt/min for 2 min NTAP treatment increased the surface roughness without causing significant phase transformation.

Effect of different cleansing methods on the artificially aged bond strength of resin to contaminated zirconia: A systematic review

PURPOSE

The aim of this review was to evaluate studies investigating the effect of cleansing methods on the artificially aged bond strength of resin to contaminated zirconia restorations and determine which cleansing method of contaminated zirconia for resin bonding improvement is more efficient.

METHODS

An electronic search of published studies in English language was carried out until July 2021 on Scopus, Web of Science, and Medline databases. Data from in vitro studies involving the evaluation of the artificially aged bond strength of resin to contaminated zirconia following different cleansing methods were included. In vitro studies in which samples were not subjected to at least 5000 thermocycles, were excluded.

RESULTS

Of 162 articles retrieved initially, 19 were eligible to be included in the systematic review, of which 5 articles were excluded. Therefore, the final sample was 14 in vitro studies. All of the included studies for air abrasion suggested this method as an effective cleansing method, but 6 of 8 included studies reported cleaning paste (Ivoclean) as an effective cleansing method. All of the included studies for NaOCl and a cleaning gel (AD Gel) reported their efficacy. Finally, the results of included studies showed the ineffectiveness of phosphoric acid, water, isopropanol, enzymatic detergents, hydrogen peroxide, and acetone.

CONCLUSIONS

Air abrasion has been reported as an effective cleansing method to improve the bond strength of resin to contaminated zirconia. To improve the effectiveness of cleaning paste in resin bonding, another efficient cleansing method should be followed after this method. However, the superior cleaning potential of air abrasion rather than cleaning paste has been reported. Sodium hypochlorite and cleaning gel seem to be as effective as air abrasion, but extensive water-rinsing is necessary after the application of these cleaning agents.

Effects of argon plasma and aging on the mechanical properties and phase transformation of 3Y-TZP zirconia

To evaluate the flexural strength (FS) and flexural modulus (FM) of a commercial 3Y-TZ0P ceramic after artificial aging and either without or with two application times of non-thermal plasma treatments (NTP). In addition, changes in crystalline phase transformation and surface nano-topography after NTP application, during different aging periods, were evaluated. Ninety 3Y-TZP bars (45x4x3 mm) were made for FS and FM testing, and assigned to nine groups (n=10): no NTP/no aging (Control); no NTP/4h aging; no NTP/30h aging; 10s NTP/no aging; 10s NTP/4h aging; 10s NTP/30h aging; 60s NTP/no aging; 60s NTP/4h aging and 60s NTP/30h aging. Artificial accelerated aging was simulated using an autoclave (134º C at 2 bar) for up to 30h. FS and FM were assessed using a universal testing machine and data analyzed using a ANOVA and Tukey test (α=0.05). The volume change in zirconia monoclinic phase (MPV) was evaluated using X-ray diffraction and surface nano-topography was assessed using atomic force microscopy (baseline until 30h-aging). NTP application did not influence the FS and FM of zirconia. Compared to the Control (no NTP/no aging), the FS of zirconia samples treated for 30 hours in autoclave (“no NTP/30h aging” group) increased. Artificial aging for 30 hours significantly increased the FM of zirconia, regardless of NTP application. MPV tended to increase following the increase in aging time, which might result in the surface irregularities observed at 30h-aging. NTP did not alter the zirconia properties tested, but 30h-aging can change the zirconia FS, FM and MPV.

Enhancing Resin Cement Adhesion to Zirconia by Oxygen Plasma-Aided Silicatization

The combinations of alumina particle air abrasion (AA) and a 10-methacryloyloxyidecyl-dihyidrogenphosphate (MDP) primer and a tribochemical silica coating (TSC) and a silane-base primer are contemporary pre-cementation treatments for zirconia restorations for bonding with resin cements. However, the stability of zirconia resists the mechanical or chemical preparations. The purpose of this study was to develop an atmospheric-pressure oxygen plasma (OP)-aided silicatization method to enhance the adhesion of resin cements to zirconia. Zirconia discs were prepared to receive surface treatments of different combinations: (1) AA or TSC (2) with or without OP treatment, and (3) a chemical primer (no primer, silane, or a silane-MDP mixture). The surface morphology, hydrophilicity, and chemical compositions were characterized, and the resin-zirconia bond strengths were examined either after 24 h or a thermocycling test. The results indicated that the OP treatment after the TSC facilitated the homogeneous distribution of silane and crosslinking of silica particles, and effectively improved the hydrophilicity. The OP increased the O and Si and reduced the C elemental contents, while the combination of TSC, OP, and silane induced SiO_x generation. Among the groups, only the TSC-OP-silane treatment effectively enhanced the bond strength and maintained the adhesion after thermocycling. With these results, the OP aided the silicatization protocol effectively, generated silane crosslinking, and resulted in superior resin-zirconia bond strength and durability compared to the current treatments.

Effect of Non-Thermal Plasma Treatment of Contaminated Zirconia Surface on Porphyromonas gingivalis Adhesion and Osteoblast Viability

Plasma treatment on a zirconia surface prevents bacterial contamination and maintains osteoblast activity. To assess the degree of adhesion of Porphyromonas gingivalis on a zirconia surface after non-thermal plasma (NTP) treatment, specimens were treated with plasma for 60, 300, and 600 s, after which P. gingivalis was inoculated onto the surface and incubated for 48 h. To assess osteoblast activity after NTP treatment, osteoblasts (MC3T3-E1) were dispensed onto the specimens contaminated with P. gingivalis immediately after NTP for 60 and 120 s, followed by incubation for 48, 72, and 96 h. P. gingivalis was cultured after 60 s of NTP treatment of zirconia. The NTP and control groups showed no significant difference (p = 0.91), but adhesion was significantly increased following NTP treatment for 300 s or longer (300, 600 s groups) (p < 0.05). After NTP treatment of P. gingivalis-contaminated zirconia, osteoblast activity significantly increased at 72 and 96 h (I60 and I120 s group) in the groups treated with plasma (p < 0.017). Application of NTP to dental zirconia implants for 60 s not only inhibits the proliferation of P. gingivalis, which causes peri-implantitis but also increases osseointegration on zirconia surfaces contaminated with P. gingivalis.

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.

Effect of the Plasma Gas Type on the Surface Characteristics of 3Y-TZP Ceramic

Plasma surface treatment can be an attractive strategy for modifying the chemically inert nature of zirconia to improve its clinical performance. This study aimed to clarify the effect of plasma gas compositions on the physicochemical surface modifications of 3 mol% yttria-stabilized zirconia (3Y-TZP). The cold, atmospheric plasma discharges were carried out by using four different plasma gases, which are He/O2, N2/Ar, N2, and Ar from an application distance of 10 mm for 60 s. Static contact angles were measured to define the surface free energy. Changes in elemental composition, surface crystallinity, and surface topography were assessed with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM), respectively. A significant decrease in water contact angle was observed in all plasma groups with the lowest value of 69° in the N2/Ar group. CLSM and SEM investigations exhibited no morphological changes in all plasma groups. XPS revealed that a reduction in the surface C content along with an increase in O content was pronounced in the case of N2/Ar compared to others, which was responsible for high hydrophilicity of the surface. XRD showed that the changes in crystallite size and microstrain due to oxygen atom displacements were observed in the N2/Ar group. The N2/Ar plasma treatment may contribute to enhancing the bioactivity as well as the bonding performance of 3Y-TZP by controlling the plasma-generated nitrogen functionalities.

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.

Osseointegration of Zirconia Implants after UV-Light or Cold Atmospheric Plasma Surface Treatment In Vivo

The influence of UV light and non-thermal plasma on the osseointegration of yttria-stabilized zirconia implants (Y-TZP) comparing the two methods is unclear. The aim of this study was to show the influence of these methods on the osseointegration of dental zirconia implants in an animal model. A total of 54 implants were either untreated, treated with UV light (UV), or non-thermal oxygen plasma for 12 min and inserted into the parietal bones of six domestic pigs. The animals were sacrificed after a healing interval of two, four, and nine weeks. The degree of osseointegration was determined using histomorphometric determination of bone-to-implant contact values (BIC) and the bone-to-implant contact values within the retentive parts of the implants (BAFO). BIC values decreased in all groups after four weeks of healing and re-increased after nine weeks in all groups. BAFO increased significantly over time in all groups. However, there were no statistically significant differences in BIC and BAFO values between the control group and the test groups and over time. Clinical studies may follow to confirm the influence of cold plasma and UV light on the healing and survival of zirconia implants.

The effect of adhesive surface with porcelain sintering and two silane coupling agents on the adhesive properties of zirconia

Background

To explore the effect of adhesive surface with porcelain sintering and different silane coupling agents on adhesive properties of zirconia ceramics.

Methods

Zirconia blocks (n=72) were randomly divided into two large groups (n=36) according to whether the adhesive surface was treated with sintered porcelain: N (no porcelain sintering), P (porcelain sintering). Then, according to different silane coupling agents, each group was randomly divided into three small groups, six small groups in total (n=12): NN (no porcelain sintering and agent), NM (no porcelain sintering + Monobond-S), NC (no porcelain sintering + Clearfil Repair); PN (porcelain sintering + no agent), PM (porcelain sintering + Monobond-S), PC (porcelain sintering + Clearfil Repair). After surface treatment, RelyX Unicem Cement was used to make ceramic-resin bonding specimens. Then, each of the six small groups was randomly divided into two subgroups; shear bond strength (SBS) was tested and bond failure mode was analyzed before and after thermal cycling 5,000 times.

Results

(I) SBS analysis: the SBS values of the P groups were significantly higher than those of the N groups (P<0.05). The groups treated with silane coupling agents showed higher SBS values than the control group (P<0.05), and the PC groups showed the highest SBS values (P<0.05). The SBS of each group was significantly decreased after thermal cycling (P<0.05). (II) The microcharacteristics under scanning electron microscopy and energy spectrum analysis: the ceramic blocks being treated by porcelain sintering showed more roughness than the control group. A large amount of silicon (Si) appeared on the surface of the ceramic blocks after porcelain sintering.

Conclusions

(I) Treating the adhesive surface by porcelain sintering can improve the bonding strength between zirconia and RelyX Unicem Cement, and the effect was better in conjunction with silane coupling agent. (II) The two kinds of silane coupling agent (Monobond-S, Clearfil Repair) can improve the bonding strength between zirconia and resin cement. The effect of Clearfil Repair is better than that of Monobond-S. (III) Thermal cycling had a significant adverse effect on SBS between zirconia and RelyX Unicem Cement. Clearfil Repair is helpful in improving the durability of zirconia bonding strength.

Non-thermal plasma for surface treatment of inorganic fillers added to resin-based cements

OBJECTIVES

This study aims to evaluate the effect of non-thermal plasma (NTP) surface treatment in two composite inorganic fillers and evaluate their impact on the chemical-mechanical properties and bond strength ability of experimental resin cements.

MATERIALS AND METHODS

Ytterbium fluoride (YF) and barium silicate glass (BS) were characterized and submitted to different surface treatments: non-thermal plasma (NTP); non-thermal plasma and 3-(trimethoxysilyl) propyl methacrylate silanization; and 3-(trimethoxysilyl) propyl methacrylate silanization. Untreated fillers were used as a control. The fillers were incorporated at 65wt% concentration into light-cured experimental resin cements (50wt% BisGMA; 25wt% UDMA; 25wt% TEGDMA; 1mol% CQ). The degree of conversion, the flexural strength, and the microshear bond strength (μSBS) were evaluated to characterize developed composites.

RESULTS

YF and BS were successfully cleaned with NTP treatment. Nor NTP neither the silanization affected the degree of conversion of resin cements. The NTP predicted an increase in YF-containing resin cements flexural strength, reducing the storage impact in these materials. NTP treatment did not affect the μSBS when applied to YF, while silanization was effective for BS-containing materials.

CONCLUSION

NTP treatment of inorganic particles was possible and was shown to reduce the amount of organic contamination of the particle surface. YF surface treatment with NTP can be an alternative to improve the organic/inorganic interaction in resin composites to obtain materials with better mechanical properties.

CLINICAL RELEVANCE

Surface cleaning with NTP may be an alternative for particle surface cleaning to enhance organic-inorganic interaction in dental composites resulting in improved mechanical strength of experimental resin cements.

Surface characterization of different surface treatments associations with plasma and bonding analysis of Y-TZP and the veneering ceramic

OBJECTIVES

To characterize the surface of zirconia (Y-TZP) submitted to different surface treatments (with and without plasma associations) and to evaluate the shear bond strength (SBS) between veneering ceramic (VC) and Y-TZP after different aging methods.

METHODS

301 Y-TZP specimens were fabricated and distributed into 7 groups: C (control): no treatment; Al: airborne abrasion with 27 μm Al₂O₃ particle; L: liner; P: plasma; Al + L: airborne + liner; Al + P: airborne + plasma; P + L: plasma + liner. The Y-TZP surface was characterized by SEM, EDS, AFM, surface profilometry, surface-free energy (SFE), and XRD. SBS between Y-TZP and VC was verified after three aging protocols: initial, after hydrothermal aging (autoclave for 5 h), or thermal fatigue (30,000 baths - 5-55 °C). One- (profilometry, SFE) and two-way ANOVA (SBS), and Tukey's HSD test were used.

RESULTS

For the plasma groups, a full globular surface coverage was observed (SEM, AFM). Si was found for Al, L, Al + L, and P + L. Roughness was lower for C, P, and Al + P. For SFE, the highest values were found when the liner was applied (>74.59 nm/Nm). The highest monoclinic content was observed for Al + L (6.96%) and Al + P (5.86%). For the initial period, Al and P + L presented the lowest SBS values (<5.85 MPa; P > 0.331). The highest SBS values were found for L, P, and P + L (hydrothermal aging) and for P, L, Al + L, and Al + P (thermal fatigue).

SIGNIFICANCE

Changes in Y-TZP topography and the SBS with the VC were found, according to treatments performed. Plasma treatment improved SBS and did not cause phase transformation.

Evaluation of the bond strengths of restorative materials to primary tooth dentin treated with different pulpotomy techniques

The aim of this study was to investigate the changes of different pulpotomy techniques on the primary tooth dentin and to evaluate the effects of these pulpotomy methods on the shear bond strength of restorative materials to primary tooth dentin. Two hundred and forty dentin specimens were distributed randomly to the study groups as; control, ferric sulphate, Biodentine® , Nd:YAG laser, photobiomodulation, and atmospheric pressure cold plasma (APCP). After the application of pulpotomy methods, samples were again randomly divided to two restorative materials (glass hybrid and composite resin) (n = 20) and shear bond strength (SBS) test was performed. Then, 12 new dentin specimens were prepared for all groups for surface analysis. Surface examination (n = 12) and fracture analyses (n = 240) were carried out with scanning electron microscope (SEM). Statistical significance range was accepted as α <.05 for all data. A statistically significant difference was obtained among all study groups for glass hybrid material as well as composite material (p <.05). While the highest mean SBS value was obtained with Nd:YAG laser (7.58 ± 0.60 MPa), the lowest value was observed with Biodentine® (6.70 ± 0.91 MPa; p = .001) for glass hybrid material. For composite material, the highest mean SBS value was calculated for Nd:YAG laser (13.79 ± 1.24 MPa), while the lowest value was obtained with ferric sulphate (10.17 ± 1.45 MPa; p = .001). Fracture modes were mainly adhesive and mixed type according to SEM analysis. Moreover, morphological changes were observed with SEM on the dentin surfaces of ferric sulphate, Biodentine® and Nd:YAG laser. Within the limitations of this study, Nd:YAG laser increased the shear bond strength values in groups of composite resin. RESEARCH HIGHLIGHTS: In this article, we report the results of the shear bonding strength test of two restorative materials (glass-hybrid vs. composite resin) to primary tooth dentin following the application of five different pulpotomy techniques (ferric sulfate, Biodentine® , Nd:YAG laser, photobiomodulation, and atmospheric pressure cold plasma) were reported. This article will contribute to the literature that there are considerably limited researches concerning the bond strength of glass hybrid to primary dentin and also atmospheric pressure cold plasma in pulpotomies. The SEM examination was performed in two stages in this study; the morphological changes in both treated dentin surfaces and the surfaces of the samples subjected to the shear bond strength test.

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.

Influence of different cleaning procedures on the shear bond strength of 10-methacryloyloxydecyl dihydrogen phosphate-containing self-adhesive resin cement to saliva contaminated zirconia

PURPOSE

To evaluate the effect of different cleaning methods on the shear bond strength (SBS) of a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing self-adhesive resin cement to zirconia after saliva contamination.

METHODS

Sixty zirconia specimens were randomly divided into four groups (n=15) according to treatment surface. Except for the control group, all samples were contaminated with saliva and were then rinsed with water-spray and air-dried. Subsequently, the specimens were either treated with a cleaning paste (CP), with argon plasma (AP), or did not undergo an additional cleaning process (WS). An MDP-containing self-adhesive resin cement was applied onto the ceramic surfaces. Specimens were stored in water (24 hours) followed by thermocycling (5°C to 55°C for 10.000 cycles). SBS tests were performed in a universal testing machine, and the results (MPa ± SD) were statistically analyzed using ANOVA and Bonferroni post-hoc test. Fractured surfaces were examined to identify the failure types using a stereomicroscopy and SEM.

RESULTS

The surface cleaning treatment (p < 0.05) significantly affected the results. The highest SBS values were observed in the control group (12.16 ± 1.22 MPa) and were statistically comparable to values for the CP group (11.38 ± 1.65 MPa). The AP group (9.17 ± 1.06 MPa) showed significantly higher bond strength than the WS group (6.95 ± 1.20 MPa), but it showed significantly lower strength than the control and CP groups.

CONCLUSIONS

The CP application was the most effective method in removing saliva contamination. The AP treatment could not restore the SBS to the same level as uncontaminated specimens.

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.

Piezoelectric Direct Discharge: Devices and Applications

The piezoelectric direct discharge (PDD) is a comparatively new type of atmospheric pressure gaseous discharge for production of cold plasma. The generation of such discharge is possible using the piezoelectric cold plasma generator (PCPG) which comprises the resonant piezoelectric transformer (RPT) with voltage transformation ratio of more than 1000, allowing for reaching the output voltage >10 kV at low input voltage, typically below 25 V. As ionization gas for the PDD, either air or various gas mixtures are used. Despite some similarities with corona discharge and dielectric barrier discharge, the ignition of micro-discharges directly at the ceramic surface makes PDD unique in its physics and application potential. The PDD is used directly, in open discharge structures, mainly for treatment of electrically nonconducting surfaces. It is also applied as a plasma bridge to bias different excitation electrodes, applicable for a broad range of substrate materials. In this review, the most important architectures of the PDD based discharges are presented. The operation principle, the main operational characteristics and the example applications, exploiting the specific properties of the discharge configurations, are discussed. Due to the moderate power achievable by PCPG, of typically less than 10 W, the focus of this review is on applications involving thermally sensitive materials, including food, organic tissues, and liquids.

Influence of Low-Pressure Plasma on the Surface Properties of CAD-CAM Leucite-Reinforced Feldspar and Resin Matrix Ceramics

The introduction of new ceramic materials for dental restorations is currently a reality; however, little information is available on their surface treatment for the bonding process. Furthermore, surface treatment with plasma on ceramic materials has been recently introduced, although not many studies are available. The aim of this study was to evaluate the surface properties of a leucite-reinforced feldspar ceramic (LIC) and resin matrix ceramic (RMC) after low-pressure plasma treatment. From each material, 48 discs were prepared and subject to surface treatment. The LIC group was treated by hydrofluoric acid (HF) (LIC-HF), plasma with oxygen (LIC-O2), and plasma with argon (LIC-Ar). The RMC group was treated by sandblasting with alumina (RMC-SB), plasma with oxygen (RMC-O2), and plasma with argon (RMC-Ar). The groups whose surfaces were not subjected to treatment were considered as the control group. Surface wettability and roughness was analyzed. The results showed significant differences among the treatments for both ceramics regarding wettability and roughness. Plasma treatments increased the wettability and had a very low effect on the roughness. Plasma treatments achieved similar values for both surface properties in each ceramic group with no differences between both treatments. Plasma treatment seems to be a promising alternative for ceramic surface treatments since it increased the surface energy of the ceramics analyzed and hardly affects the roughness. Further studies are necessary to evaluate the effect of plasma treatment on the bond strength of ceramics.

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.

Impact of multiple firings and resin cement type on shear bond strength between zirconia and resin cements

PURPOSE

The aim of this study was to evaluate the effect of multiple firings on the bond strength between yttria-tetragonal zirconia polycrystals (Y-TZP) and 2 types of resin cements.

MATERIALS AND METHODS

Sixty 3Y-TZP specimens (LAVA Frame Multi) were divided into 3 groups depending on the following firing procedures: (1) 2-firing cycles, (2) 5-firing cycles, (3) 10-firing cycles. Two samples from each group were investigated by using SEM to determine the morphological changes. All specimens were treated with 125 µm airborne-particle abrasion and the surface roughness of each specimen was measured. The specimens from each firing group were then further divided into 2 subgroups (n = 9) to apply 2 types of resin cement (MDP-free resin cement: RelyX Unicem-RU, and MDP containing resin cement: Panavia F 2.0-PA). The shear bond strength (SBS) test was performed and failure types of all the debonded specimens were classified by using a stereomicroscope as adhesive, cohesive, and mixed. The statistical analysis of surface roughness and SBS data were performed by using 1-way ANOVA and 2-way ANOVA followed by Tukey-HSD tests (α=.05). Failure modes were calculated as a percentage for each group.

RESULTS

The bond strength of RU and PA to the specimens obtained with 2 firings were not statistically different from each other (P=.1). However, the SBS values of PA were found to be significantly higher than RU for the specimens obtained with 5 and 10 firing cycles (P=.001 and P=.02, respectively). Surface roughness analysis revealed no statistical difference between groups (P=.2). The SEM analysis of samples fired 5- and 10- times showed irregularities and boundary loss in zirconia grains, and empty spaces between zirconia grains.

CONCLUSION

The bond strength of PA cement was higher than that of RU to the zirconia subjected to repeated firings (5 and 10 firing cycles). When zirconia is subjected to multiple firings, using MDP-containing resin cement can be recommended.

Oxygen Plasma Improved Shear Strength of Bonding between Zirconia and Composite Resin

Improving the strength of the bonding of zirconia to composite resins remains a challenge in dental restorations. The purpose of this study was to evaluate the shear strength of the bonding of zirconia to composite resins, thereby verifying the hypothesis that as the power of the non-thermal oxygen plasma increases, the bonding strength of the plasma-treated zirconia is increased. The effects of the oxygen plasma power (100, 200, and 400 W) on the surface structure, chemical composition, and hydrophilicity of the zirconia and the strength of the bonding between zirconia and composite resin were investigated. As a result, after different plasma power treatments, the surface structure and phase composition of zirconia were not different from those of zirconia without treatment. However, the oxygen plasma treatment not only reduced carbon adsorption but also greatly increased the hydrophilicity of the zirconia surface. More importantly, the strength of the bonding between the plasma-treated zirconia and composite resin was significantly higher than that in the corresponding control group without plasma treatment. Regardless of whether the zirconia was pristine or sandblasted, the higher the plasma power, the greater the bond strength obtained. The conclusion is that the oxygen plasma treatment of zirconia can effectively improve the strength of the bonding between the zirconia and composite resin without damaging the microstructure and phase composition of the zirconia.

Effect of zirconia decontamination protocols on bond strength and surface wettability

OBJECTIVE

To evaluate the effects of human saliva decontamination protocols on bond strength of resin cement to zirconia (Y-PSZ), wettability, and microbial decontamination.

MATERIALS AND METHODS

Zirconia plates were sandblasted and divided into (a) not contaminated, (b) contaminated with human saliva and: (c) not cleaned, (d) cleaned with air-water spray, (e) cleaned with 70% ethanol, (f) cleaned with Ivoclean, or (g) cleaned with nonthermal atmospheric plasma (NTAP). The wettability and microbial decontamination of the surfaces were determined after saliva contamination or cleaning. Monobond Plus (Ivoclar Vivadent) was applied after cleaning, followed by Variolink LC (Ivoclar Vivadent). The samples were stored 1 week before shear bond strength (SBS) testing, and data (SBS and wettability) were analyzed by one-way analysis of variance and Tukey test (α = .05).

RESULTS

Saliva contamination reduced SBS to zirconia compared to not contaminated. Both Ivoclean and NTAP produced higher SBS compared to not cleaned and were not significantly different from the not contaminated. Ivoclean produced the highest contact angle, and NTAP the lowest. With the exception of using just water-spray, all cleaning protocols decontaminated the specimens.

CONCLUSIONS

Both Ivoclean and NTAP overcame the effects of saliva contamination, producing an SBS to zirconia comparable to the positive control.

CLINICAL SIGNIFICANCE

Dental ceramics should be cleaned prior to resin cementation to eliminate the effects of human saliva contamination, and Ivoclean and NTAP are considered suitable materials for this purpose.

Evaluation Of The Effect Of Different Surface Treatments, Aging And Enzymatic Degradation On Zirconia-Resin Micro-Shear Bond Strength

Purpose

The purpose of this study was to evaluate the effect of surface treatments on zirconia-resin bonding and the effect of aging on bond durability for one year.

Method

Three hundred and twenty zirconia blocks were divided into 4 equal study groups. Group 1 (control): as-sintered, group 2: (GB): grit-blasted, group 3: (LAS): laser-etched, group 4: (SIE): selective infiltration etching. Composite cylinders were bonded to the zirconia with resin cement and ceramic primer. Aging was performed following 3 different aging protocols: thermocycling, storage in distilled water, or storage in an enzymatic esterase solution. Micro-shear bond strength test (μSBS) was recorded using a universal testing machine. μSBS values were analyzed using two-way Analysis of Variance followed by Tukey post-hoc tests. Level of significance was set at 0.05.

Results

GB, LAS and SIE groups showed significantly higher values when compared to control. Groups GB, LAS and SIE reported a significant decrease up to 50% in μSBS after water storage and enzymatic degradation, while control group reported a 90% decrease. Failure analysis showed mainly adhesive failure for control group, while the percentage of cohesive failure in resin cement was higher in SIE group compared to GB and LAS groups.

Conclusion

Water aging and esterase solutions played a significant role by increasing bond degradation. A minimum of one-year water and esterase storage medium should be used to evaluate the durability of the bond between resin cement and zirconia.

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.

Durability of resin bonding to zirconia ceramic after contamination and the use of various cleaning methods

OBJECTIVES

The aim of the study was to evaluate the influence of contamination and different cleaning methods on the tensile bond strength with a phosphate monomer containing luting resin to zirconia ceramic.

METHODS

After the contamination with saliva or silicone disclosing agent, 228 polished and airborne-particle abraded zirconia discs were ultrasonically cleaned with 99% isopropanol. In a second step, the specimens were either treated with argon-oxygen plasma, air plasma, enzymatic cleaning agent or did not undergo an additional cleaning process. Uncontaminated zirconia specimens were used as the control group. X-ray photoelectron spectroscopy (XPS) was used for chemical analysis of the bonding surfaces of specimens. Plexiglas tubes filled with composite resin were bonded to zirconia specimens with a phosphate monomer containing luting resin. Tensile bond strength (TBS) was tested after 3 days or 150 days water storage with 37,500 thermal cycles.

RESULTS

XPS revealed a decrease of the carbon/oxygen ratio after plasma treatment and an increase after treatment with an enzymatic cleaning agent in all groups. All contaminated specimens showed high and durable TBS after cleaning with a combination of isopropanol and a non-thermal atmospheric plasma. After the cleaning with enzymatic cleaning agent the TBS was significantly reduced in all groups after 150 days thermal cycling.

SIGNIFICANCE

The combination of isopropanol and plasma cleaning was effective in removing salvia and disclosing agent contamination. Enzymatic clearing agent was not able to remove contamination effectively and had a negative impact on the TBS of non-contaminated specimens.

Can Nonthermal Plasma Improve the Adhesion between Acrylic Resin for Ocular Prostheses and Silicone-Based Relining Material?

PURPOSE

To investigate the influence of nonthermal plasma (NTP) treatment on the tensile bond strength between heat-polymerized acrylic resin for ocular prostheses and silicone reliner, with and without the use of an adhesive primer.

MATERIALS AND METHODS

One-hundred and sixty-four acrylic resin specimens were fabricated and randomly distributed into four groups according to the type of surface treatment: Sofreliner Primer, NTP, Sofreliner Primer + NTP, and NTP + Sofreliner Primer. Two specimens interposed with relining material (Sofreliner) formed one test sample to perform the tensile bond strength tests, before (initial) and after storage (final) in saline solution (37°C, 90 days, n = 10). Surface characterization was performed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The failure type was classified as cohesive, adhesive, or mixed. The data were analyzed statistically using the two-way ANOVA and Tukey test, as well as the chi-squared test (α = 0.05), Bonferroni correction (α = 0.005), and Spearman correlation coefficient (α = 0.05).

RESULTS

The SEM and EDS analyses showed the presence of a thin, homogenous organic film in the groups treated with NTP. The NTP + Sofreliner Primer group presented the largest bond strength mean values in the initial period (p < 0.05). Sofreliner Primer and NTP + Sofreliner Primer groups presented the first and second largest tensile bond strength mean values in the final period (p < 0.05), respectively. NTP + Sofreliner Primer group also had the largest number of cohesive (70%, initial) and mixed (90%, final) failures.

CONCLUSIONS

The NTP treatment performed before the primer application enhanced the bond between the acrylic resin ocular prosthesis and the Sofreliner silicone-based reliner, even after 90 days of immersion in saline solution.

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 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.