Indeed, cementation of zirconia restorations remains a major challenge in clinical situations, and many cementation options discussed in the literature may remain controversial. The purpose of this study was to evaluate the performance of zirconia pretreated with alumina and glass beads using two different primers compared with conventional resin cements and cements containing 10-methacryloyl oxydecyl dihydrogen phosphate (MDP). Bond strength of self-adhesive resin cements (no primer required). ). Fully sintered highly transparent zirconia samples (n = 160) were divided into 2 pretreatment groups (n = 80): alumina sandblasting (AB) and glass beads (GB). Each group was then divided into 4 groups (20 people each) based on the primer and cement used: regular self-adhesive resin cement, MDP-silane primer, MDP primer using regular self-adhesive resin cement, and MDP primer containing MDP. cement. Shear bond strength (SBS) was measured after thermal cycling. Failure modes were analyzed using a stereo microscope. Contact angle and surface morphology were studied using additional fully sintered samples (n = 30) created specifically for this purpose and divided into control groups (no pretreatment [unmodified], alumina group, and glass bead blasting group). Perform two-way ANOVA on SBS and analyze failure modes. Aluminum oxide sandblasting showed higher levels of SBS compared to MDP silane primer (p = 0.034) and MDP primer glass bead pretreatment (p < 0.001). While cement containing MDP showed higher but not significant SBS when pretreated with glass beads. Alumina sandblasting and glass bead pre-treatment improve the bond strength of zirconia using a combination of primers before bonding with conventional polymer cement. In addition, self-adhesive MDP containing cement as well as a prepared surface showed the highest achievable bond strength. It was concluded that both alumina sandblasting and glass bead blasting improved the bond of SBS to MDP-containing self-adhesive resin cement, reducing the number of clinical steps required during the luting process of zirconia restorations.
Today, due to the rapid development and innovation of digital dentistry, there is an increasing demand for highly esthetic restorations in everyday dental practice. Dental zirconia is considered one of the most commonly used restorative materials due to its superior mechanical properties than glass ceramics. This led to an expansion of indications in the field of fixed and indirect restorations, however, the earlier generation of zirconia was less transparent and more opaque and therefore, by comparison, was a dense polycrystalline structure and did not contain a glass matrix and therefore less esthetic. . Glass ceramic limits the use of the back2. To improve optical properties, the yttrium content was increased to 5 mol% yttria-stabilized polycrystalline tetragonal zirconia (5Y-TZP), resulting in 50% cubic zirconia compared to conventional yttria-stabilized tetragonal zirconia containing 3. 4.5 mol. , thereby improving the overall aesthetics and leading to the use of new ultra-transparent zirconia.
Compared to silica-based ceramic materials, the bonding of zirconia to dental tissue or other synthetic materials is controversial due to its chemical inertness and resistance to aggressive chemical agents (strong acids, bases, organic and inorganic solvents6). Over a 5-year follow-up period, the bone loss rate of zirconia restorations was 4.7%7, which was a direct result of delamination between the various bonding boundaries within the structure8.
Several methods have been studied in the literature to improve the bond strength between zirconia ceramics and resin cements, including mechanical, chemical and/or chemomechanical surface pretreatment methods9,10,11. Two published meta-analyses have confirmed the importance of combining mechanochemical surface treatments to improve the bond strength of zirconia to resin-cement12,13. Mechanical, aerodynamic wear, tribochemical aerodynamic wear, application of low-melting porcelain, thermochemical etching solutions, selective penetrating etching, laser irradiation, plasma spraying and zirconium dioxide powder coatings, as well as primers based on 10-zirconium oxide with methacryloxydecyl dihydrogen phosphate (10-MDP) are proposed. . ) molecules and their salts to change the chemical properties of the zirconium oxide surface9,14,15,16,17.
The air abrasive method using aluminum oxide particles showed the highest adhesion strength compared to other surface treatment methods18. However, air abrasive machining of alumina can result in surface defects such as defects, plastic deformation, embedded abrasive alumina and microcracks, which deteriorate the mechanical properties of zirconia and reduce the fracture toughness19. To reduce defects on the surface of zirconia, Hanlar et al., 2022 suggested using glass beads as a softer material than the sharp and hard alumina, followed by the use of 10-MDP and a silane primer, which does not create a surface. Desirable adhesion properties. reported for microcracks in zirconia20.
There are few reports on the effectiveness of glass bead blasting as a mechanical bonding method alone or in chemical combination with various zirconia primers. Therefore, this in vitro study was conducted to evaluate the effects of alumina sandblasting and glass bead blasting on highly transparent (5Y-TZP) zirconia alone or with different formulations of zirconia primers and self-adhesive resin cements containing MDP. The connection strength of the connection does not require subsequent activation. Null hypotheses tested: 1. Zirconia sandblasted with alumina and/or glass beads will show the same bond strength, 2. Different MDP primers will not affect the bond strength of zirconia 3. Containing MDP with self-adhesive resin cement will show the same adhesion strength. . showed similar results to other MDP primers tested.
The substrate tested was a highly transparent polycrystalline yttrium-stabilized tetragonal zirconia sample (5Y-PSZ; Liaoning Youci Co., Ltd., Liaoning, China). MDP-silane primer (Visalys retoration primer, Kettenbach GmbH & Co. KG, Eschenburg, Germany) and MDP-BPDM primer (Z-prim, Bisco Inc., IL, USA) were used. Conventional resin cement (Visalys CemCore, Kettenbach GmbH & Co. KG) and self-adhesive resin cement (Z-prim, Bisco Inc.) were used for bonding in this study. The full composition of the materials used is given in Table 1.
A total of 160 square 5Y-PSZ specimens (10 × 10 × 3 mm before sintering) were prepared using a low-speed precision saw (Isomet 4000, Buehler, Lake Bluff, IL, USA) under dry conditions without water coolant. A further 160 disc-shaped specimens with a diameter of 4 mm and a thickness of 3 mm were used to glue them together to evaluate the shear bond strength. To measure surface roughness and contact angle, another 30 square samples of the specified sizes were used. All samples were sintered in a zirconia furnace (Lindberg/Blue M, Asheville, NC, USA) using a 7-step cycle at 1450°C according to the manufacturer’s instructions. The parameters of the sintering process are given in Table 2.
For joint shear strength analysis, fully sintered specimens [square and disc-shaped (n = 160 each)] were equally divided into two groups (n = 80 each) according to the alumina sandblasting (AB) and glass bead (GB) pretreatment protocol. group. According to the bone cement fixation protocol, each group was divided into 4 subgroups (n = 20 in each group 1. No primer + conventional polymer cement, 2. MDF-silane primer + conventional polymer cement, 3. MDP-BPDM); Primer + ordinary polymer cement, 4. Contains MDP polymer cement, no subsequent primer is required. A graphical representation of the method is shown in Figure 1.
Schematic representation of the methods used in the present study. (A–F) Indicates the steps of shear bond strength testing. Answer: Prepare 160 square samples and 160 disk samples. B: Perform sintering according to Table 2. C: Pre-treatment by sandblasting with aluminum oxide (AB) and glass beads (GB). D: According to the bone cement fixation scheme, each group is divided into 4 subgroups (n = 20 in each group 1. Without primer + ordinary polymer cement, 2. MDP-silane primer + ordinary polymer cement, 3. MDP -); BPDM primer + regular resin cement, 4. Contains MDP resin cement, no subsequent primer required. E: After gluing, thermal cycle 10,000 times. F. Attach the specimen to the universal testing machine according to the shear bond strength chart. (G–J) represent surface parameters and contact angle measurements. G: Follow the instructions in Table 2 to pre-lay 30 square samples and sinter them. H: The samples are divided into three groups: control (no pre-treatment), alumina sandblasting (AB) and glass beads (GB). I: Use 3D-CLSM to check the surface roughness parameters of the sample. J: Check the sample using a contact angle measuring device.
Before bonding, all samples were polished on 600-grit silicon carbide paper. Groups AB and GB were sandblasted with 50 μm Al2O3 particles (Kulzer, GmbH, Germany) and 75 μm glass beads, respectively. Sandblasting time for both groups was 20 seconds, 25 psi pressure, 10 mm distance, and 90° angle using a sandblaster (Microetcher IIA, Danville Materials, San Ramon, CA, USA). All samples were then cleaned using an ultrasonic cleaner (Easyclean MD, Renfert, GmbH, Germany) filled with distilled water for two minutes and then dried completely with oil-free air.
Glue each large square sample to a smaller disc-shaped sample. For conventional resin cement sets, use dual-cure resin cement (Visalys Cem-Core, Kettenbach GmbH & Co. KG, Eschenburg, Germany). For the MDP Silane Primer Set: Apply MDP Silane Primer (Visalys Restorative Primer, Kettenbach GmbH & Co. KG, Eschenburg, Germany) with a microbrush, dry for 60 seconds and air dry, then apply regular resin cement. For the MDP-BPDM primer set, samples were coated with 2 coats of MDP-BPDM primer (Z-Prime Plus, BISCO Inc., IL, USA) for 5 seconds, followed by a gentle blast of air, followed by the application of regular resin. cement. In the group of self-adhesive resin cements containing MDP, all samples were cemented using self-adhesive dual-cure resin cement containing MDP (TheraCem, Bisco Inc., Illinois, USA) without prior application of a primer. During the gluing process, a static standard load of 5 kg was applied to all samples using loading device 12, and an LED lamp with a curing intensity of 1500 mW/cm2 (Eighteen Curing Pen) was used to begin curing of the adhesive. , Xifarui Medical Technology, Jiangsu Province, China) ) 40 seconds.
All samples were conditioned using a thermal cycler (SD Mechatronik, Germany) to create hydrothermal stress at the interface between the test material and the cement. Bonded specimens were immersed in a distilled water bath at 5°C and 55°C for 10,000 cycles with a holding time of 20 seconds and a dwell time of 10 seconds to simulate one year of oral clinical practice13. Shear bond strength values were measured and recorded using a universal testing machine (Instron, model 3345, UK) with a crosshead speed of 1 mm/min. For failure analysis, the detached interface was examined using a stereomicroscope (Olympus, Tokyo, Japan) at 20× magnification, and the failures were classified as: adhesive failure “A,” cohesive failure “C,” and mixed failure “M.” .
Based on surface roughness, 30 square fully sintered samples were divided into 3 groups (10 per group) based on the type of pretreatment: control (sandblasting without alumina or glass beads), alumina blasting (AB), and glass beads (GB). ). Analysis was performed using a 3D confocal laser scanning microscope (CLSM, Keyence VK-X100, Keyence, Japan) and MultiFile analyzer software (V.1.3.3) at 50× magnification (scanning area 205 × 273.3 μm). 1.120, Keyence) is used to analyze the scan results obtained. Arithmetic mean height (Sa), expanded interface area ratio (Sdr), and texture aspect ratio (Str) values were recorded and analyzed.
After measuring the surface roughness parameters, the surface wettability was measured using the saddle method using a contact angle measuring device (DSA25B, Krüss GmbH, Germany) using deionized water using the same samples. For each sample, record 3 readings for 3 different drops and take the average as the average reading for each test sample. All average values are provided for statistical analysis.
The sample size was calculated based on data obtained by Hanlar et al. et al. 202220. When α = 0.05, at least 20 samples per group are sufficient for 95% power to detect. The control mean is 9.2, the AB mean is 11.7, and the standard deviation is 2, resulting in an effect size (d) of 1.2. Sample size was calculated using G*Power version 3.1.9. Normality of data was examined using the Shapiro-Wilk test. Two-way ANOVA was used to compare the tested pretreatments and primers/cements, followed by pairwise comparisons using Tukey’s HSD test. In addition, shear bond strength data were analyzed using Weibull analysis (R4, R Foundation for Statistical Computing, Vienna, Austria). Weibull parameters were calculated using Wald estimates, and 95% confidence intervals were calculated using Monte Carlo simulations. Compare feature strengths of different groups (probability of failure 63.2% and 10%). For surface roughness parameters and contact angle measurements, comparisons were made between test groups using one-way ANOVA followed by pairwise comparisons using Tukey’s HSD test. (α = 0.05). Statistical analyzes were performed using IBM SPSS Statistics for Windows version 26.0. Armonk, New York: IBM Corporation
Pretreatment group and primer/cement group had a significant effect on shear bond strength: p = 0.003 and p < 0.001, respectively. The interaction between the two variables had a significant effect on shear bond strength (p = 0.002) as shown in Table 3. The results of pairwise comparisons show that alumina sandblasting (AB) exhibits higher shear bond strength than glass beads (GB). ) for the base group MDP-silane (p = 0.034) and MDP-BPDM (p < 0.001). While for the group of conventional resin cements and self-adhesive resin cements containing MDP, they showed little difference between AB and GB pretreatments. For the AB pretreatment group, conventional resin cement showed the least significant shear bond strength compared to all other groups, and the differences between MDP silane primer, MDP-BPDM primer, and MDP-containing cement were negligible. For the GB pretreatment group, conventional polymer cement showed the lowest significant shear bond strength, whereas MDP-containing polymer cement showed the highest significant shear bond strength compared to all other groups. There are no significant differences between the MDP-silane primer and the MDP-BPDM primer. The shear bond strength values of the various test groups are given in Table 4.
The results of the Weibull analysis are shown in Table 5 and Figure 2. The characteristic Weibull strength of conventional polymer cement is significantly lower than all other primer/cement groups, with AB and GB not significantly different from each other. For AB pretreatment, there is no significant difference in the characteristic Weibull strength between MDP-silane + conventional cement, MDP-BPDM + conventional cement, and cement containing MDP resin. For GB pretreatment, resin cement containing MDP showed significantly higher intrinsic Weibull strength compared to all other groups. AB+MDP-BPDM+conventional cement and GB+MDP-containing polymer cement showed the highest Weibull modulus. Both ANOVA and Weibull analysis showed similar results except that in case of Weibull analysis there was no significant difference between AB and GB in case of MDP-silane primer + regular cement.
Weibull survival plot for shear bond strength (MPa) of test group. The horizontal dotted line with a 63.2% failure rate helps compare the strengths of the features. Vertical control dotted lines at pressures of 20 MPa and 40 MPa to compare the survival curves of the test groups. The resin cement containing MDP showed the highest inherent strength compared to all other primer/cement options.
When pretreated with glass beads (GB), all test groups showed 100% adhesion failure. While with aluminum oxide (AB) pretreatment, mixed failure and adhesion failure were observed in all groups. Neither GB nor AB faced a cohesion problem. The failure analysis diagram is shown in Figure 3, and representative images of the failure diagram are shown in the supplementary file.
Loft diagram showing failure modes for different groups of tests. A Adhesive failure, (M) Mixed failure, C Cohesive failure.
The results of surface roughness and contact angle parameters are shown in Figure 4. For Ca, control (0.82 ± 0.04) and GB (0.84 ± 0.07) showed the lowest significant values of Ca compared to AB (0.97 ± 0.05), p < 0.001. While for Sdr, control (1.20 ± 0.11) and AB (1.36 ± 0.70) showed the highest significant values of Sdr compared to GB (0.74 ± 0.14), p < 0.001 . For Str, the control group (0.85 ± 0.03) showed the least significant str value compared to AB (0.77 ± 0.10), p = 0.044. The Str GB values (0.79±0.07) did not differ significantly from the control and AB values. Contact angle measurements showed that the control group (50.53 ± 4.29) had the highest significant value, p = 0.038, compared to the AB group (44.94 ± 2.12). GB (47.60 ± 2.34) did not differ significantly from control and AB in terms of contact angle measurements.
The charts show surface topography parameters (arithmetic mean height (Sa), developed interface area ratio (Sdr), and texture aspect ratio (Str)) and contact angle (CA) measurements for different test groups.
Over the past few decades, zirconia has been introduced into dentistry as a stronger alternative to weaker silica-based ceramics and to expand its range of indications as a restorative alternative. However, even if more translucent monolithic alternatives are developed, bonding to zirconia will always be a major challenge since most bonding protocols rely on bonding to glass matrices, which can be exposed to strong acids and corrode in a way that strong acids cannot. acid. Zirconium, due to its polycrystalline nature, does not have a glassy matrix.
This study examined the zirconia bond strength of two different MDP primers with conventional resin cement and a self-adhesive resin cement containing MDP without primer in combination with alumina and sandblasted glass beads. The null hypothesis tested was rejected because sandblasting using alumina and glass beads combined with a primer before consolidation and compared to the sandblasting group that was consolidated using conventional polymer cement without primer, using only MDP cement shows higher adhesion strength.
The strength of the bond created between zirconia and cement plays an important role in the success and longevity of dental restorations. Poor adhesion can be a major cause of cracks in the repair material, which can reach the cement interface and cause repair failure21.
The results of this study show that alumina or glass bead blasting combined with a chemical surface treatment (primer) significantly improves the shear strength of 5Y-PSZ zirconia joints. Previous studies have found that air grinding using alumina particles is the most preferred and reliable surface treatment method for high strength ceramics as it increases surface roughness, thereby increasing surface energy, improving wettability and potentially cleaning the bonding surface 22 . 23 For glass beads, the increase in bond strength can be attributed to the introduction of silica into the bonded surface, thereby creating a stable bond between the hydroxyl groups (OH) of the silica on the glass surface and the primer/resin. chemical bonds. Another study evaluated the effect of different siliconization schemes (glass beads and tribochemical coatings) with different silane treatments on the bond strength of translucent zirconia and found that both alumina and glass bead blasting improved bond strength. Their findings were confirmed by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses, which confirmed high levels of silica deposited on the surface of cement samples even when they were not washed away by ethanol or ultrasonic cleaning10.
The surface roughness of the sintered zirconia may play a role in adhesion by increasing the surface area of the sintered substrate. The surface roughness after alumina sandblasting is higher compared to the surface treated with glass beads. The results of this study are consistent with those of Khanlar et al.20 who showed that air abrading of alumina particles could increase the surface roughness, whereas glass beads had no effect. Moreover, their SEM/EDS study showed that alumina formed grooves and protrusions on the surface, and glass beads caused the precipitation of silica particles without affecting the surface roughness20. On the other hand, Mehari et al.25 found that alumina increased the bond strength, while glass beads and untreated three different types of zirconia showed almost the same results, which can be attributed to the increase in surface roughness of alumina.
Alumina sandblasting showed the smallest significant contact angle and the highest surface roughness compared to glass beads and controls, two factors that we found resulted in high bond strength. Translucent zirconia has a larger grain size, which makes the grains easily pulled out during the alumina sandblasting process, resulting in surface defects and in turn increasing the surface roughness of zirconia26. In addition, alumina sandblasting creates micromechanical devices that increase roughness, increase surface energy, and provide greater resin fluidity in these microretaining elements, resulting in higher bond strength 27. Previous studies have suggested that sandblasting may be responsible for the formation of hydroxyl groups on the surface of zirconia, which leads to an increase in the reactivity of zirconia with phosphate monomers in MDP, thereby affecting the strength of the joint28,29. This does not apply to glass beads because the low hardness of glass beads cannot change the surface roughness of zirconia. On the contrary, its effect is limited because the incorporation of silica particles into the zirconia surface leads to a decrease in contact angle and an increase in surface energy, thereby improving adhesion10,20.
The results of this study show that MDP-containing self-adhesive resin cement has the highest bond strength regardless of pretreatment method, followed by MDP-BPDM primer and then MDP-silane airfoil primer Alumina. For the glass bead pretreated group, primers containing MDP-silane and MDP-BPDM had similar binding strengths. Pure MDP has better adhesion properties to zirconia surfaces, and adding silane to the MDP bottle reduces adhesion16. However, there are no pure MDP primers on the market yet, and commercially available primers combine more than one primer to provide versatility and compatibility with a variety of substrates.
Theoretically, the phosphate group in the MDP molecule reacts with one or two zirconium atoms to form two bond configurations: “double coordination” or “single coordination”30. MDP-containing primers have hydrophobic phosphate groups that react with hydroxyl groups on the surface of translucent zirconia, thereby increasing bond strength31. In addition, MDP prevents water from penetrating between the hydrophobic phosphate layer and the zirconium oxide layer due to the role of the decyl group in MDP32.
According to the literature, MDP present in the resin diluent forms stable bonds with pretreated zirconia in air even after thermal cycling33. This can be explained by the fact that MDP contains polymerizable methacrylate ends that adhere to the resin and hydrophilic phosphate ends that chemically attach to the zirconia to increase bond strength21.
According to previous studies15,34,35, the use of primers containing MDP silane improved the bond strength between resin cement and zirconia ceramics. In addition, for the GB group, higher bond strength values were justified by the chemical interaction between silane and silica. Glass beads 20 are left on the surface of the zirconia. However, its adhesive strength is lower than that of self-adhesive polymer cement containing MDP. This may be due to the presence of silanol in the MDP silane primer, which may result in a decrease in the bond strength between MDP and zirconia surfaces 11,36.
In previous studies, primers containing MDP-BPDM were found to have a positive effect on the bond strength of sintered zirconia37,38,39. A previous study disagreed with our findings and attributed the reason to the presence of carboxylic acid monomers in BPDM, which may have a critical influence on the bond between this primer and the self-adhesive polymer cement methacrylate40.
Therefore, according to the study, the use of air abrasive alumina has always been considered the gold standard for zirconia bonding. It is worth noting that glass beads may be a promising alternative used in combination with cement-containing primers or MDPs. improve adhesion to zirconium dioxide. Due to the limitations of this study, the masticatory forces and anatomical designs of fixed partial dentures should be evaluated to mimic the oral condition rather than the simplified designs implanted in the current work. In addition, further in vivo studies are required to evaluate the effectiveness of the proposed combination regimen.
Considering the limitations of this study, the following conclusions can be drawn based on the results obtained:
1. Aluminum oxide sandblasting and glass bead pre-treatment can improve the adhesive strength of zirconia, use MDP primer, or simply use MDP self-adhesive cement without pre-priming.
2. MDP containing self-adhesive resins that do not require pre-priming can be used as a successful cementation solution, while fewer clinical steps are required for successful zirconia cementation.
3. Sandblasting should be combined with appropriate chemical treatment to improve the bond strength to the zirconia.
Post time: Oct-29-2024