Bond strength durability of self-adhesive resin cements to zirconia ceramic: An in vitro study

Bonding Effectiveness of Saliva-Contaminated Monolithic Zirconia Ceramics Using Different Decontamination Protocols

Objective

This research study investigated the effect of new decontamination protocols on the bonding capacity of saliva-contaminated monolithic zirconia (MZ) ceramics cemented with two different monomer-containing self-adhesive resin cements.

Materials and Methods

Standardized tooth preparations (4 mm. axial height) were performed for eighty human maxillary premolars under constant water cooling system. Eighty monolithic zirconia crowns (Whitepeaks Supreme Monolith) (n = 8/10 groups) were manufactured by CAD-CAM. Specimens were kept in the artificial saliva at pH = 7.3 for 1 minute at 37°C except control groups. The specimens have not been prealumina blasted and grouped according to cleaning methods and resin cements: control groups (C) (no saliva contamination + GPDM + 4-META (N) (CN) and 10-MDP (M) containing resin cement (CM), alumina blasted (AL) + GPDM + 4-META (ALN) and 10-MDP containing resin cement (ALM), zirconium oxide containing universal cleaning agent (IC) applied + GPDM + 4-META (N) (ICN) and 10-MDP containing resin cement (ICM), pumice (P) applied + GPDM + 4-META (PN) and 10-MDP containing resin cement (PM), and air-water spray (AW) applied + GPDM + 4-META (AWN) and 10-MDP containing resin cement (AWM)). Monobond Plus was applied to all surfaces for 40 seconds before cementation. The thermal cycle was applied at 5,000 cycles after cementation. The crowns were tested in tensile mode at a speed of 1 mm/min. The mode of failure was recorded. SEM examinations were carried out at different magnifications. Data were analyzed using rank-based Kruskal-Wallis and Mann-Whitney tests.

Results

No significant differences were found between the surface treatments and between the two types of resin cements. Interaction effects between surface treatments and resin cements were found to be significant by two-way ANOVA analysis. ICM group resulted in significantly better bond strength results compared with CN. ICM was found to result in better bond strength results compared with PM. The combination of universal cleaning agent and 10-MDP containing resin cement had significantly the highest cementation bond strength values. The increasing order of mean tensile bond strength values of decontamination protocols was C < AW < P < AL < IC. The mean tensile bond strength of 10-MDP containing resin cement was slightly higher than GPDM + 4-META containing resin cement.

Conclusions

Universal cleaning agents can be preferred as an efficient cleaning method with 10-MDP-containing cement after saliva contamination for better adhesive bond strength of 4 mm crown preparation height of monolithic zirconia ceramics.

Effect of universal adhesive pretreatments on the bond strength durability of conventional and adhesive resin cements to zirconia ceramic

PURPOSE

This study aimed to evaluate the effect of pretreatment of three different universal adhesives (Single Bond Universal [SBU], All-Bond Universal [ABU], and Prime&Bond universal [PBU]) on the bonding durability of an adhesive (Panavia F 2.0, PF) and a conventional (Duo-Link, DL) resin cements to air-abraded zirconia.

MATERIALS AND METHODS

Rectangular-shaped zirconia specimens were prepared. The chemical composition and surface energy parameters of the materials were studied by Fourier transform infrared spectroscopy and contact angle measurement, respectively. To evaluate resin bonding to the zirconia, all the bonding specimens were immersed in water for 24 h and the specimens to be aged were additionally thermocycled 10000 times before the shear bond strength (SBS) test.

RESULTS

The materials showed different surface energy parameters, including the degree of hydrophilicity/hydrophobicity. While the DL/CON (no pretreatment) showed the lowest SBS and a significant decrease in the value after thermocycling (P < .001), the PF/CON obtained a higher SBS value than the DL/CON (P < .001) and no decrease even after thermocycling (P = .839). When the universal adhesives were used with DL, their SBS values were higher than the CON (P < .05), but the trend was adhesive-specific. In conjunction with PF, the PF/SBU produced the highest SBS followed by the PF/ABU (P = .002), showing no significant decrease after thermocycling (P > .05). The initial SBS of the PF/PBU was similar to the PF/CON (P = .999), but the value decreased after thermocycling (P < .001).

CONCLUSION

The universal adhesive pretreatment did not necessarily show a synergistic effect on the bonding performance of an adhesive resin cement, whereas the pretreatment was beneficial to bond strength and durability of a conventional resin cement.

Durability of Resin Bonding to Dental 3Y-TZP Zirconia Using Different Adhesive Systems

This laboratory study was conducted to evaluate and compare the resin bond strength of different adhesive resin systems in different combinations and the durability of their bonds with zirconia ceramic.

MATERIALS AND METHODS

One hundred and twenty-eight specimens were milled from 3Y-TZP zirconia ceramic. The bonding surfaces of all disks were wet polished, steam cleaned, airborne-particle abraded and ultrasonically cleaned in 99% isopropanol. The specimens were randomly divided into four main groups according to the applied resin system; two conventional and two self-adhesive systems were used. Each group was further subdivided into two subgroups; the first was conditioned with the specified primer for conventional luting resins or not conditioned for the self-adhesive systems, whereas the second subgroup of each was conditioned with the same phosphate monomer-containing primer (Alloy Primer). The zirconia specimens were adhesively bonded, using the allocated luting resin, to plexiglass tubes filled with self-curing composite resin (Clearfil FII). Half of the specimens of each subgroup were stored in distilled water at 37 °C for 3 days, whereas the other half were subjected to artificial aging, 150 days of storage and additional thermal cycling. Thereafter, all specimens were subjected to TBS testing using a universal testing machine. Statistical analysis was conducted using two-way ANOVA followed by separate one-way ANOVAs. The Games-Howell post-hoc test was applied for pairwise comparisons.

RESULTS

All specimens survived storage with thermal cycling. The mean TBS values ranged from a minimum of 43.4 ± 5.0 MPa to a maximum of 66.4 ± 3.5 after 3 days and from a minimum of 13.6 ± 2.5 MPa to a maximum of 50.1 ± 9.4 MPa after 150 days.

CONCLUSIONS

Artificial aging had a significantly negative effect on all test groups. The chosen adhesive-resin system had a significant effect on the resulting TBS values. The highest TBS values were achieved for the self-adhesive luting resin G-Cem One but were statistically comparable to the results obtained for the dual-cure luting resin G-Cem LinkForce.

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.

Longevity of Anterior Composite Restorations for Localized Tooth Wear: A Scoping Review

(1) Objective: This scoping review evaluates composite restorations as a treatment modality for anterior tooth surface loss and investigates the longevity of the direct and indirect composites used herein. (2) Method: The search encompassed Medline, Embase, Web of Science, the Cochrane Library, and hand search utilizing the PICO framework. (3) Results: Eight studies were included in this review, comprising one randomized controlled trial, one retrospective, and six prospective studies. Some studies reported favorable outcomes for composite restorations in anterior teeth. Although not statistically significant, evidence supported the anterior composite as a viable short- to medium-term solution for managing tooth wear. Direct resin composites were deemed clinically and cost-effective when managing localized anterior tooth wear. However, limitations and inconsistencies in this scoping review limited definitive clinical recommendations. (4) Conclusions: Further research, including well-managed randomized controlled trials using standardized protocols and longer follow-up periods, is essential to reconfirm the long-term efficacies of anterior composite restorations when managing tooth wear. A robust research design and exacting protocols could facilitate more meaningful clinical conclusions.

Fracture resistance of monolithic translucent zirconia crown bonded with different self-adhesive resin cement: influence of MDP-containing zirconia primer after aging

OBJECTIVES

Successful ceramic restorations depend on the strong bonding with resin cement and even stress distribution. The aim of this study was to evaluate the impact of adding MDP-containing zirconia primer before self-adhesive resin cements with different functional acidic monomers on fracture resistance of monolithic zirconia crown.

MATERIALS AND METHODS

Eighty defect-free human maxillary premolars were divided according to the cement type and application of MDP-containing zirconia primer into eight groups (n = 10): Calibra Universal (C), Calibra Universal combined with zirconia primer (CZ), RelyX U200 (R), RelyXU200 combined with zirconia primer (RZ), Panavia SA Cement Plus (P), Panavia SA Cement Plus combined with zirconia primer (PZ), Multilink Speed (M), and Multilink Speed combined with zirconia primer (MZ). After teeth preparation and fabrication of zirconia crowns, each crown was bonded to its corresponding tooth. All specimens were subjected to 10,000 thermocycles between 5 and 55°C, followed by cyclic load (50 N) for 240,000 cycles. Each specimen was subjected to a static axial load until fracture using universal testing machine and the fracture load was recorded. The fracture mode studied and recorded. The fracture load results were analyzed using two-way ANOVA test (α = 0.05).

RESULTS

A significant interaction (P = 0.038) of combining MDP-containing zirconia primer and cement type on fracture resistance of monolithic zirconia crown was detected. The mean fracture load values of zirconia crown were significantly influenced by the combined application of the MDP-containing zirconia primer with Calibra Universal (P = 0.01), RelyX U200 (P < 0.001), and Multilink Speed (P = 0.038), while there was no significant difference with Panavia SA Cement Plus (P = 0.660). There was significant difference (F = 20.69, P < 0.001) between the mean fracture loads of groups with self-adhesive cements (C, R, P, and M groups). The highest fracture load was recorded with RZ group (2446.90 ± 126.72 N) while the lowest fracture load was recorded with C group (1623.18 ± 149.86 N).

CONCLUSIONS

The self-adhesive resin cement with different acidic functional monomer affects the fracture resistance of monolithic zirconia crown. Application of MDP-containing primer could improve the fracture resistance of monolithic zirconia crown with most self-adhesive cements. The application of an MDP-containing primer had no impact on the fracture resistance of monolithic translucent zirconia crown bonded by MDP-containing self-adhesive resin cement.

Analysis of the effect of thermocycling on bonding cements to zirconia

Objective

The aim of this study was to evaluate the effect of thermocycling on shear bond strength (SBS) of several resin cement materials to different types of zirconia dental ceramics.

Materials and Methods

120 square shaped disc specimens were fabricated using two types of zirconia blocks (Sagemax and Sirona). Each zirconia group was divided into three sub-groups based on the resin cement bonded to the specimens. Three different self-adhesive resin cements were used (Calibra, Breeze and RelyX). The specimens were further grouped into experimental and control groups (n = 10). The experimental specimens were exposed to a thermo-cycling protocol of 1500 cycles in water bath at 5c and 55c. Specimens were then stored at 37c for 24 h then all specimens underwent SBS test with an Instron machine. Mode of failure was inspected visually and microscopically. Data were statistically analyzed using multivariate analysis of variance followed by one-way analysis of variance, Tukey's multiple comparison test, student's t-test for independent samples were used to compare the mean values of SBS in relation to the categorical study variables.

Results

The mean SBS values of experimental groups were significantly lower than control groups for all the 6 combinations of Zirconia and cement types (p < 0.0001). The higher mean difference (14.29 MPa) was observed in the combination of Sagemax and Rely-X. Rely-X displayed the highest SBS among all the cements while no significant difference was found in mean SBS values of Calibra and Breez cements in all groups. The mean SBS values of Sagemax zirconia were significantly higher than the Sirona with all three types of cements (p < 0.0001) within control groups. Microscopic and visual analysis demonstrated a majority of adhesive mode of failure.

Conclusion

Thermocycling significantly reduced the SBS between the zirconia materials and self-adhesive resin cements tested. The amount of reduction varies according to cement and zirconia types.

Use of final irrigant Potassium Titanyl Phosphate laser; Sapindus Mukorossi and Fotoenticine on the bond values of zirconia post-to-canal dentin

AIMS

Assessment of the efficacy of final root canal irrigants Sapindus mukorossi (SM), Potassium titanyl phosphate laser (KTPL), and Fotoenticine (FTC) on the push-out bond strength (PBS) of zirconia post.

MATERIALS AND METHODS

The root canal procedure was initiated using the 10 K file and the working length was determined on single-rooted human premolar teeth after decoration. The canals were then enlarged using ProTaper universal system and filled using single cone gutta-percha (GP) and AH Plus resin sealer. Post space was prepared by removing 10mm of GP from the canal. All the teeth were then allocated into four groups based on the final irrigating regime used (n=10) Group 1: 5.25% NaOCl+17% EDTA, Group 2: 5.25% NaOCl + KTPL, Group 3: 5.25% NaOCl + FTC and Group 4: 5.25% NaOCl+ SM. Zirconia posts were cemented in the canal space. The specimens were sectioned and implanted in auto-polymerizing acrylic resin. A universal testing machine and stereomicroscope at 40x magnification were used for PBS and failure mode analysis. ANOVA and Tukey post hoc test were used to make group comparisons(p=0.05).

RESULTS

Group 4 (5.25% NaOCl+ SM) coronal section displayed the highest PBS (9.29±0.24 MPa). However, group 3 (5.25% NaOCl+ FTC) apical third (4.08±0.14 MPa) showed the lowest bond values. Group 2 (5.25% NaOCl+ KTP laser) and Group 3 at all three-thirds unveiled no significant difference in PBS(p>0.05). However, Group 1 (5.25% NaOCl+17%EDTA) and Group 4 displayed comparable outcomes of bond strength(p>0.05) CONCLUSION: Sapindus mukorossi has the ability to be used as a final root canal irrigant alternative to EDTA. However, future studies are still required to conclude the outcomes of existing research.

The Effect of Surface Treatments on Zirconia Bond Strength and Durability

To evaluate the effects of airborne particle abrasion (APA) combined with MDP-containing resin cement, a glass-ceramic spray deposition (GCSD) method on the shear bond strengths (SBSs) and durability of 3 mol% yttrium oxide-stabilized zirconia ceramic (3Y-TZP) compared with lithium disilicate glass ceramics (LDGC). 3Y-TZP disks were randomly treated as follows: for Group APA+MDP, 3Y-TZP was abrased using 50 μm Al₂O₃ particles under 0.1 Mpa and bonded with MDP-containing resin cement; for Group GCSD, 3Y-TZP was treated with the GCSD method, etched by 5% HF for 90 s, silanized and bonded with resin cement without MDP. Group LDGC was bonded as the Group GCSD. X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray detector (EDX) were used to analyze the surface chemical and micro-morphological changes of the ceramics before bonding. The bonded ceramic specimens were randomly divided into subgroups, and the SBSs were determined before and after 10,000 thermocycling. The SBSs were analyzed with a one-way ANOVA analysis. Failure modes were determined with optical microscopy and SEM. The XRD, ATR-FTIR and XPS results identified the formation of lithium disilicate and zirconium silicate on 3Y-TZP after GCSD. The SEM micrographs revealed that 3Y-TZP surfaces were roughened by APA, while 3Y-TZP with GCSD and LDGC surfaces could be etched by HF to be porous. The APA treatment combined with MDP-containing resin cement produced the high immediate zirconia shear bond strengths (SBSs: 37.41 ± 13.51 Mpa) that was similar to the SBSs of the LDGC (34.87 ± 11.02 Mpa, p > 0.05), but, after thermocycling, the former dramatically decreased (24.00 ± 6.86 Mpa, maximum reduction by 35.85%) and the latter exhibited the highest SBSs (30.72 ± 7.97 Mpa, minimum reduction by 11.9%). The 3Y-TZP with GCSD treatment displayed the lower zirconia SBSs before thermocycling (27.03 ± 9.76 Mpa, p < 0.05), but it was similar to the 3Y-TZP treated with APA and MDP containing resin cement after thermocycling (21.84 ± 7.03 vs. 24.00 ± 6.86 Mpa, p > 0.05). The APA combined with MDP-containing resin cement could achieve the high immediate zirconia SBSs of those of the LDGC, but it decreased significantly after thermocycling. The GCSD technique could yield the immediate zirconia SBSs similar to those of LDGC before thermocycling, and long-term zirconia SBSs were similar to those of 3Y-TZP treated with APA followed by MDP-containing resin cement after thermocycling. Hence, the GCSD technique could enrich zirconia surface treatments and is an alternative to zirconia surface pretreatment for 3Y-TZP bond durability.

The effects of applying a novel cleaner on the bonding strength of zirconia surfaces

This study evaluates how pre-treatment with an MDP-containing cleaning agent (Katana Cleaner, Kuraray) influences the micro-shear bond strength (µSBS) of saliva-contaminated zirconia when used with universal adhesive (UA) systems. Rectangular specimens (2 mm × 12 mm × 15 mm) were obtained (IPS, e.max ZirCAD, MO, B65L17, Ivoclar Vivadent) and divided into three groups; a non-contaminated group (control group)(CON), a contaminated and cleaned with isopropyl alcohol group(ISP), and lastly, a group contaminated and cleaned with an MDP-containing cleaning agent(KAC). Each group was then subdivided into three subgroups according to the UAs used (n = 12). Composite cylinders were prepared and bonded to each surface with Panavia V5 (Kuraray, Noritake Dental). A µSBS test was performed and the data were evaluated with the two-way analysis of variance (two-way ANOVA) and multiple comparisons test (α = 0.05). The highest µSBS values were obtained in the non-contaminated group (p < 0.001), regardless of UAs. All subgroups showed lower µSBS values after saliva contamination, but KAC resulted in significantly higher µSBS values than 99% isopropanol (p < 0.001). Overall, the lowest µSBS value was obtained with 99% isopropanol. The KAC-Clearfil UA subgroup resulted in statistically significantly higher µSBS values than the other UAs (p = 0.035 and 0.007), although all three UAs resulted in sufficient µSBS values. This study revealed that applying KAC followed by a UA containing phosphate monomers produces promising results for improving µSBS values of zirconia, greater than results using 99% isopropanol.Clinical relevance: An MDP-containing cleaning agent followed by a phosphate monomer containing a universal adhesive is a promising method to obtain acceptable bonds with saliva-contaminated zirconia ceramics.

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.

Effect of Different Cleaning Methods on Shear Bond Strength of Resin Cement to Contaminated Zirconia

The aim of this study was to evaluate the effect of different cleaning methods on the shear bond strength (SBS) of resin cement to contaminated zirconia specimens. Eighty rectangular-shaped specimens (2 × 5 × 10 mm) were fabricated from Zirconia blocks (IPS e.max ZirCAD) and randomly divided into 8 groups (n = 10). Group A (control) was not exposed to contaminants. The following tests specimens were contaminated with saliva and silicone indicating paste. Group B was coated with ceramic primer, then subjected to contamination. Groups C, D, E, F, G, and H were contaminated; cleaned with water rinse, Ivoclean, air particle abrasion, hydrofluoric acid, KATANA^TM Cleaner and ZirClean^TM, respectively, and then coated with ceramic primer and bonded to dual cure resin cement cylinders. All the specimens were subjected to artificial aging and surviving specimens were subjected to the SBS test. For statistical analysis, ANOVA and multiple comparison methods at the 0.05 significance level were used. There was no statistically significant difference among Ivoclean (21.48 ± 2.90 MPa), air particle abrasion (21.92 ± 2.85 MPa), and the control group (24.68 ± 5.46). The application of ceramic primer before contamination did not preserve the SBS of resin cement to zirconia. Cleaning the contaminated zirconia surface with hydrofluoric acid (15.03 ± 3.63) or KATANA^TM Cleaner (17.27 ± 7.63) did not restore SBS to the uncontaminated state, but it was significantly higher than simply rinsing with water (12.46 ± 5.17) or the use of ZirClean^TM (11.59 ± 5.53). The bond strength of resin cement to zirconia was influenced by cleaning methods.

Effect of Thermocycling on the Bond Strength of Self-Adhesive Resin Cements Used for Luting CAD/CAM Ceramics to Human Dentin

The aim of the study was to evaluate the influence of thermocycling on the shear bond strength of self-adhesive, self-etching resin cements luted to human dentin and computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Three modern self-adhesive dental cements (Maxcem Elite, RelyX U200, Panavia SA) were used to lute three CAD/CAM ceramics (IPS Empress CAD, IPS e.max CAD, IPS e.max ZirCAD) onto the dentin. One conventional cement (Panavia V5) served as a control. After preparation, the samples were subjected to thermocycling as a method of artificial aging of dental materials applied to simulate long-term use in oral conditions. Shear bond strength was evaluated according to PN-EN ISO 29022:2013-10 and failure modes were observed under a light microscope. Statistical analysis was performed. The study demonstrated that a combination of ceramics and cements directly impacts the bond strength. The highest bond strength was observed in Panavia V5, lower in Panavia SA and Maxcem Elite and the lowest–in RelyX U200. Adhesive failure between human dentin and cements was the most common failure mode. Moreover, thermocycling highly decreased bond strength of self-adhesive, self-etching cements.

Adhesion between zirconia and resin cement: A critical evaluation of testing methodologies

This study aimed to analyze different methodologies (tensile, microtensile, shear, microshear, and interfacial toughness) for evaluation of the bond strength between zirconia (Y-TZP) and resin cement. Zirconia ceramic blocks (VITA in-Ceram® YZ, VITA Zahnfabrik, Germany) were obtained, substrate surfaces were air-abraded with aluminum oxide (50 μm) for 10 s (2 bar pressure, distance: 10 mm, angle: 90°). Then, the specimens were washed with distilled water, dried, and coated with Clearfil Ceramic Primer that was actively applied with a microbrush for 20 s. The specimens were then cemented with resin cement under a load of 750 g, followed by photo-polymerization (40 s on each surface). After cementation, the specimens were aged in thermocycling (8000 cycles, 5-55 °C, 30 s for each bath) and subjected to tensile, microtensile, shear, microshear or interfacial toughness tests. All specimens were inspected for failure modes. The microtensile test showed the highest bond value (18.29 N/mm²). The microshear tests showed the highest coefficient of variation (0.59) and highest number of pre-test failures. The interfacial energy to fracture test showed that as the shear stress increased its interaction in the adhesive interface, the coefficient of variation also increased. The bond strength of Y-TZP showed different results according to the methodology, as well as its interfacial energy to fracture varied according to the angulation/type of stress specimen was submitted. The lower the shear stress at the adhesive interface of the mixed tests (interfacial energy to fracture), the lower was the variability of the test.

Influence of the application of a pre-sintered surface augmentation on zirconia and lithium disilicate bonding using an adhesive composite resin cement

OBJECTIVE

The purpose of this laboratory study is to evaluate the application of a pre-sintered surface augmentation to zirconia (Zir) and lithium disilicate (LDS) ceramics on the delamination strength of adhesive resin cement. The applied surface augmentation was the ruling of lines to the pre-sintered surface of the ceramics.

METHODS

Ninety milled Zir and sixty pressed LDS specimens (3mm×0.5mm×25mm) were created and divided into five groups (n=30). Group 1: Zir no surface treatment (control Zir-NT); Group 2: Zir airborne particle abraded (Zir-APA) with 30μm CoJet; Group 3: Zir pre-sintered surface augmentation (Zir-SA); Group 4: LDS etched (control LDS-etched) and; Group 5: LDS with pre-sintered surface augmentation and etching (LDS-SA). A resin adhesive cement (3mm×1mm×8mm) was then applied and cured to the ceramic specimens. The delamination strength values of the resin cement from the ceramic were recorded. The delamination strength data were analysed statistically using one-way ANOVA and Turkey post hoc analysis.

RESULTS

The mean delamination strength and standard deviation, when comparing only the Zir-SA to the resin cement were statistically different (p<0.001); Zir-SA 63.42±11.85, Zir-NT 26.82±12.07, and Zir-APA 48.11±17.85MPa. Comparison between LDS groups were not significantly different (p=0.193); LDS-etched 33.49±16.07 and LDS-SA 28.83±10.15MPa. The delaminated Weibull modulus was highest for surface augmentation Zir specimens (m=13.56) but decreasing to less than half for Zir-APA (m=6.27) and Zir-NT (m=5.68). The Weibull values for the LDS-SA and LDS-etched specimens was 5.63 and 3.38 respectively.

SIGNIFICANCE

Incorporating the pre-sintered surface augmentation to zirconia improved the delamination strength and reliability of Zir to the resin cement but not for LDS.

Influence of elapsed time between airborne-particle abrasion and bonding to zirconia bond strength

OBJECTIVE

The airborne-particle abrasion of zirconia with alumina particle (APA) has been reported to result in the durable bonding of appropriate adhesive luting systems. However, whether a delay between APA and the application of the adhesive luting material might affect the resulting bond strength and its durability is unknown.

METHODS

A total of 140 disc-shaped zirconia specimens were divided according to the elapsed time between the APA of zirconia and its bonding into 5 test groups (15 min, 1 h, 4 h, 24 h, and 72 h). The specimens were airborne-particle abraded with 50-μm Al₂O₃, and then stored at room temperature according to the test group (n = 28/group). Surface free energy (SFE) was measured for 12 specimens per group using a goniometer. For each group 16 Plexiglas tubes filled with composite resin were bonded to the zirconia specimens with an adhesive luting resin (Panavia 21). Tensile bond strength (TBS) was tested for subgroups of 8 specimens after water storage for 3 days and for 150 days with 37,500 thermal cycles.

RESULTS

SFE decreased significantly within 24 h after APA. TBS after 3 days of water storage ranged from 38.3 (1 h) to 28.4 MPa (24 h) and after 150 days with thermocycling from 38.3 (15 min) to 24.8 MPa (24 h).

SIGNIFICANCE

Based on these results, the time between the APA of zirconia and the application of adhesive materials should be minimized when bonding nonretentive zirconia restorations clinically.

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.

Bonding crowns and bridges with resin cement: An American Dental Association Clinical Evaluators Panel survey

BACKGROUND

Bonding crowns and bridges with resin cement can improve retention and reinforcement of the restoration. However, there is variation in the steps taken by different practitioners to achieve this goal.

METHODS

The authors developed a survey on bonding dental crowns and bridges with resin cement and distributed it electronically to the American Dental Association Clinical Evaluators (ACE) Panel on May 22, 2020. The survey remained open for 2 weeks. Descriptive data analysis was conducted using SAS Version 9.4.

RESULTS

A total of 326 panelists responded to the survey, and 86% of respondents who place crowns or bridges use resin cements for bonding. When placing a lithium disilicate restoration, an almost equal proportion of respondents etch it with hydrofluoric acid in their office or asked the laboratory to do it for them, and more than two-thirds use a silane primer before bonding. For zirconia restorations, 70% reported their restorations are sandblasted in the laboratory, and 39% use a primer containing 10-methacryloyloxydecyl dihydrogen phosphate. One-half of respondents clean their lithium disilicate or zirconia restorations with a cleaning solution. Resin cements used with a primer in the etch-and-rinse mode are the most widely used. The technique used to cure and clean excess resin cement varies among respondents.

CONCLUSIONS

The types of resin cements used, tooth preparation, crown or bridge preparation, and bonding technique vary among this sample.

PRACTICAL IMPLICATIONS

Although many dentists bond crowns and bridges on the basis of best practices, improvement in the process may be achieved by dentists communicating with their laboratory to confirm the steps performed there, ensuring an effective cleaning technique is used after try-in and verifying that the correct primer is used with their chosen restorative material.

The Retentive Strength of Zirconium Oxide Crowns Cemented by Self-Adhesive Resin Cements before and after 6 Months of Aging

The aim of this study was to evaluate the retentive strength of zirconium oxide (yttria-stabilized tetragonal zirconia polycrystals (Y-TZP)) crown-copings treated by combined mechanical and chemical treatments and cemented by four types of self-adhesive resin cements (SARCs) to human prepared teeth, before and after six months of aging in water and thermocycling. A total of 120 molar teeth were mounted, prepared using a standardized protocol and digitally scanned, and Y-TZP copings were produced. Teeth were randomly assigned to four SARC groups. Prior to cementation, the intaglio surfaces of all crowns were sandblasted and then coated with Z-Prime™ Plus (Bisco Dental, Schaumburg, IL, USA). Post cementation, each cement group was subdivided into aged and non-aged groups. After aging, the cemented assemblies were tested for retentive strength using a universal testing machine. Failure analysis was conducted by inspecting all matched debonded surfaces of the teeth and crowns at 3× magnification. Aging treatment did not affect the retentive strength of the Y-TZP crown-copings (p = 0.918). The interaction between cement and aging was statistically significant (p = 0.024). No significant differences in the retentive strengths between the different SARCs were observed pre-aging (p = 0.776), whereas post-aging, Panavia SA (PAN; Kuraray Dental Co Ltd., Osaka, Japan) showed significantly higher strength than RelyX U-200 (RU200; 3M ESPE, Seefeld, Germany). The predominant failure mode was adhesive between the cement and dentin, followed by mixed mode failure.

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.

Color matching of full ceramic versus metal-ceramic crowns - a spectrophotometric study

Background and aims

To verify the color match of metal-ceramic and full ceramic crowns, using instrumental methods.

Methods

A number of 153 teeth (anterior and posterior teeth), in 62 patients, were restored with metal ceramic (MC, n=119), pressed-ceramic (PC, n=28), and zirconia-ceramic (ZC, n=6) full coverage crowns. The shade of a reference natural tooth was recorded instrumentally with a dental spectrophotometer (Vitaeasyshade Advance 4.0) in “single tooth measurement”, which provided the base color in Vita Classic (VC) and Vita 3D Master shades (3D).

For verifying the outcome of the restoration “verify restoration” mode was used, and ΔE values were recorded for both VC and 3D Master shade guides. Moreover, matching symbols were also recorded (***=good, **=fair, *=poor). Descriptive statistics was performed and data were analyzed (One-sample z-Test, α=0.05) for comparison with visual thresholds in dentistry (Perceptibility Threshold – PT=1.2 and Acceptability Threshold – AT=2.7).

Results

The data did not follow a normal distribution (Kolmogorov-Smirnov test, p<0.05). Recorded color difference was significantly higher than PT and AT, for all types of restorations, regardless of the coding system (p<0.05). For MC crowns in 2.52% (4.20% for 3D) of the cases the color difference was smaller than PT, in 19.32% (the same for 3D) of cases was between PT and AT, and in 78.15% (76.47% for 3D) of cases was higher than the AT. For PC crowns in 3.57% (0% for 3D) of the cases the color difference was smaller than PT, in 25% (32.14% for 3D) of cases was between PT and AT, and in 71.42% (67.85% for 3D) of cases was higher than the AT. In the case of ZC crowns none of the restorations had color difference smaller than PT, but in 16.66% of cases was between PT and AT, and in 83.33% of cases was higher than the AT, for both VC and 3D.

Conclusion

Within the limitations of the study, a better color match was achieved in the case of pressed ceramic crowns, made of lithium disilicate. In most of the situations the color difference between the restoration and the reference tooth exceeded the perceptibility thresholds, but the matching was recorded as “fair” by the spectrophotometer.

[Effects of universal adhesives and resin cement on the shear bond strength of zirconia]

OBJECTIVE

To study the effects of universal adhesives and resin cement on the shear bond strength and durability of zirconia ceramics.

METHODS

Zirconia ceramics were sintered into 20 mm×10 mm×10 mm and 10 mm×10 mm×10 mm specimens. The experiment was divided into 12 groups. The two types of specimens were bonded using two variants of resin cement (RelyX Ultimate and Clearfil SAC self-adhesive resin cement), universal adhesives (non-adhesive, Scotchbond uni-versal adhesive, and Clearfil SE One adhesive), and storage conditions (water bath and water bath-thermal cycling). The shear bond strengths were tested, and the fracture morphologies were analyzed.

RESULTS

The cement (F=8.41, P<0.01) and adhesive (F=30.34, P<0.01) exerted a significant effect on the shear bond strength of zirconia, whereas storage condition showed no significant effect on this property (F=1.83, P=0.18). The lowest shear bond strength (14.02 MPa±6.86 MPa) was exhibited by the group treated with RelyX Ultimate resin cement, non-adhesive, and water bath-thermal cycling, whereas the highest shear bond strength (54.12 MPa±8.37 MPa) was displayed by the group treated with RelyX Ultimate resin cement, Scotchbond universal adhesive, and water bath-thermal cycling.

CONCLUSIONS

Universal adhesives can improve the durability of the bonding of resin cement to zirconia. If non-self-adhesive resin cement is used without a universal adhe-sive, the durability of the bond will be greatly reduced.