|Year : 2020 | Volume
| Issue : 3 | Page : 355-361
The effect of different surface treatments on repair with composite resin of ceramic
K Barutcigil, O Kirmali
Department of Prosthodontics, Faculty of Dentistry, Akdeniz University, Antalya, Turkey
|Date of Submission||03-Aug-2019|
|Date of Acceptance||01-Nov-2019|
|Date of Web Publication||5-Mar-2020|
Dr. K Barutcigil
Department of Prosthodontics, Faculty of Dentistry, Akdeniz University, Antalya
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objectives: This study evaluated the effect of Er, Cr: YSGG laser irradiation at different powers on repair bond strength (RBS) between ceramic restoration and composite resin (CR). Materials and Methods: Sixty ceramic samples were prepared and thermocycled for 2,500 cycles between 5°C and 55°C. Samples randomly divided into six groups (n = 10) according to the different surface treatment: control group (no surface treatment), 9.6% hydrofluoric acid etching, 37% phosphoric acid etching, and irradiations with Er, Cr: YSGG lasers (1 to 3W). The Cimara System was applied to all samples surface according to the manufacturer's instructions. CR resin was built-up on each ceramic surface using a tygon tube. The RBS test was performed at a crosshead speed of 1 mm/min, and one sample of each group was also observed under SEM and EDS was used to measure the elemental profiles of each specimen. Data was analyzed with one-way ANOVA and Tukey HSD test. Results: The lowest RBS was recorded in Group OF, and the highest RBS was recorded in Group HF, followed by Group 3W. There was no statistical difference between Group Control, 1W and 2W. Furthermore, differences in RBSs between Group 3W and the other groups except Group 2W were significant (P < 0.05). In EDS analysis, there are evident differences between surface treated samples and controls. Conclusions: 3W laser irradiation may be an alternative method to acid etching for enhancing the RBS of CR to ceramic.
Keywords: Acid etching, ceramic, composite resin, laser, shear bond strenght
|How to cite this article:|
Barutcigil K, Kirmali O. The effect of different surface treatments on repair with composite resin of ceramic. Niger J Clin Pract 2020;23:355-61
| Introduction|| |
In recent years, the development of reinforced ceramic systems has accelerated due to increased aesthetic expectations. One of the most widely used systems is lithium disilicate glass ceramic, which possesses optimal physical properties because of its increased optical properties and natural translucency. Lithium disilicate glass ceramics are frequently preferred in dentistry, especially for anterior restorations, due to their superior aesthetics, stability, and biocompatibility.
The flexural strength of lithium disilicate glass ceramic (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein) ranges from 360 to 400 Mpa. Although it has adequate strength, fractures are among the most common clinical problems. Occlusal loads, fatigue, trauma, intraceramic defects, and parafunctional habits can cause fractures at ceramic restorations.,,, Fracture restoration is accomplished by changing the restoration or repairing the fracture area. Restoration repair is easier, less costly, and more conservative than changing the whole restoration, which is a costly, laborious procedure that may lead to new dental pulp trauma. During the repair process, the ceramic surface is roughened to establish a proper bond between composite resin (CR) and ceramic. The process is completed by using bonding agents or silane and applying new CR.
Various surface roughening methods, such as diamond burs, air abrasion, etching and dental lasers have been used to increase bond strength.,, In recent years, many studies have been conducted on the roughening of enamel and dentin surfaces with Er:YAG and Er, Cr:YSGG lasers. Energy is absorbed by the water molecules in the tissue, which are then suddenly heated and evaporated. The high vapor pressure causes many microexplosions, which cause a loss of matter. However, lasers function by removing particles from the ceramic surface through microexplosions; this process is called ablation. The resulting craters and pores contribute to micromechanical retention. Due to these properties, various studies have found that roughening can be performed on ceramic surfaces with lasers.,
These applications reduce the surface energy and the surface angle between the resin and the ceramic and increase the ceramic's wettability. Modifying the ceramic's surface structure provides micromechanical retention and contributes to better resin bond formation. This study evaluated the effects of five surface treatment methods on the repair bond strength (RBS) of ceramic to CR. The null hypothesis is as follows: Lasers with different powers will not increase the RBS values between the ceramic and CR.
| Materials and Methods|| |
Sixty lithium disilicate-based glass ceramic specimens (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein) were prepared according to the manufacturer's recommendations using the lost wax technique (diameter = 5 mm, height = 3 mm). All sample surfaces were ground with 600-, 800-, and 1,200-grit silicon carbide papers (English Abrasives, London, England) and polished (Phoenix Beta Grinder/Polisher, Buehler, Germany) to obtain a smooth surface. Cylindrical blocks were ultrasonically cleaned for 15 min in ethanol and deionized water. The samples were then subjected to a thermal change test in heat baths at 5 ± 2°C and 55 ± 2°C, with 2,500 cycles. The prepared samples were randomly divided into six groups (n = 10);
C Group – Control: The samples received no mechanical surface treatment.
HF Group – Hydrofluoric Acid: The ceramic samples' bonding surfaces were etched with 9.6% hydrofluoric acid (Angelus Dental, Londrina, Brazil) for 60 s, then rinsed for 30 s with distilled water and dried with air.
OF Group – Phosphoric Acid: The ceramic samples' bonding surfaces were etched with 37% phosphoric acid (Ketch, Kuraray Co, Japan) for 60 s, then rinsed for 30 s distilled water and dried with air.
Laser Irradiation Groups (1–3W – Er, Cr:YSGG Laser: The ceramic samples' surfaces were irradiated with an Er, Cr: YSGG laser (Waterlase MD, Biolase Technology, Inc., Irvine, CA) (2.78 μm wavelength) at power settings of 1, 2, and 3 W at 10 Hz. The laser's optical fiber was 6 mm in diameter, 4 mm in height, and was placed 10 mm from the ceramic surface. The laser was applied for 20 s with a 50% water/air flow in each case. Dosimetric parameters used for laser application are presented [Table 1].
All samples were then cleaned with the ultrasonic cleaning device for 3 min. One sample from each group was randomly selected to evaluate surface roughness and topography with scanning electron microscope (SEM) analysis (JSM 6060LV; Jeol, Tokyo, Japan). The samples were mounted on an aluminum stub and sputter coated with a gold layer (Polaron Range SC 7620, Quorum Technology, Newhaven, UK), then vacuum packed in argon for 2 min and examined for surface changes with the SEM at a magnification of 500 × with a 15-kV accelerating voltage and a 80-μA beam current.
After surface treatments, a single-bond universal adhesive (3M ESPE Dental Products, St. Paul, MN, USA) was applied to the bonding area as a silane in accordance with the manufacturer's recommendations. A direct composite (Grandio DC; VOCO, Cuxhaven, Germany) was polymerized over the ceramic surface center using a Teflon mold (5 mm in diameter and 2 mm in height) with an Astralis 7 light-curing unit (Ivoclar Vivadent, Schaan, Liechtenstein) for 40 s. Samples were then immersed in distilled water at 37°C for 24 h prior to RBS value measurement. The RBS values were measured with a universal testing device (Lloyd LFPlus; Ametek Inc, Lloyd Instruments, Leicester, UK) at a crosshead speed of 1 mm/min until failure occurred. The fracture patterns were classified as occurring at the interface between the direct composite and the ceramic (adhesive), within the direct composite (cohesive) or a mix (adhesive and cohesive).
Data distribution was examined using the Kolmogorov–Smirnov test. A nonparametric one-way ANOVA test and a Tukey test were used for statistical analysis at a significance level of P < 0.05 using SPSS 21 (SPSS Inc., Chicago, IL, USA).
| Results|| |
The mean and standard deviation of the RBS values are presented in [Table 2]. The highest RBS value was recorded for the HF and 3W groups (12.92 ± 1.17 and 12.30 ± 1.25, respectively), and the OF group (8.15 ± 1.15), which dramatically reduced adhesion, presented RBS values similar to the 1W group (9.64 ± 1.69). Laser irradiation at 2W slightly increased the RBS values of all groups, and significant differences were found between the control group and the 3W group, as well as between the control group and the HF group (P < 0.05). In addition, laser irradiation at 1W and 2W, when applied to the ceramic surface, did not affect the RBS between the ceramic and CR interface. Similarly, the RBS values were found between the control, 1W and 2W groups. The results of the present study indicate that the fracture pattern between the ceramic and the CR was primarily adhesive (control, OF, 1W, and 2W groups) and mixed (HF and 3W groups). SEM analyses showed a significant difference between each laser irradiated group, especially the 3W group, for obtaining a rough area compared to the control, OF and 1W groups, which had smooth, homogenous surfaces. Melted areas, deeper crevices, and small pits were observed in the HF, 2W, and 3W groups and were also detected in the SEM images. The surfaces of samples treated by lasers showed carbonized areas and depressions, which possibly resulted from high energy (2W and 3W). Furthermore, higher laser power settings may cause heat damage to the ceramic surface because of local temperature changes.
Energy dispersive spectroscopy (EDS) was used in the quantitative analysis of the ceramic bonding area's elemental composition after various pretreatments [Figure 1]. Analyzed samples showed, in general, prominent differences in chemical composition between the control group and the treated samples. Differences in elemental composition among groups may be explained by the structure of the ceramic, which is not homogeneous, as well as by etching times for acid etching groups and laser parameters. There was also no correlation between RBS and EDS results in any group.
|Figure 1: EDS images of the specimens with selected area SEM images at 500×. (A) untreated, Group C, (B) Group OF, (C) Group HF, (D) 1W laser irradiated, Group 1W, (E) 2W laser irradiated, Group 2W, (F) 3W laser irradiated, Group 3W|
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| Discussion|| |
In the present study, the results suggest that laser irradiation (1–3 W) led to surface morphology alterations. The RBS values obtained for the control, 1W and 2W groups were statistically similar (P > 0.05), whereas the 3W laser group experienced significantly increased RBS. As a result, the null hypotheses was partially rejected.
Intraoral repair techniques may be less costly, faster, and less traumatic for dentists and patients, especially in cases involving expensive and delicate restorations due to fractures or chips.,, Enhanced bonding between ceramics and CR is a prerequisite for enhanced clinical success, so the bond between them must be solved to obtain strong adhesion., This study demonstrated that laser irradiation at various powers resulted in surface topography alterations, as revealed by SEM evaluation.
The shear bond strength test is a common method applicable to ceramic systems. Because most stresses related to fractures in the bond between the material and the restoration are shear stresses and because the applied forces are perpendicular to the bond surface, the bond surface's small cross-sectional area effectively eliminates the combination of structural defects that significantly affect the test readings. Therefore, the bond strength test was used to assess the bond between ceramic and CR in our study.
HF etching, which is the gold standard in bond strength testing and is a more effective surface roughening technique than various chemical treatments, is the preferred technique for improving micromechanical retention between CR and ceramic restoration.,,,, However, conflicting results also have been observed in related studies in which intraoral use of HF could harm soft tissues and damage the mechanical behavior of some ceramics.,,, According to Shiu et al., who compared three acid agents, the treatment of ceramic surfaces with acid etching enhances surface roughness, resulting in a strong bond between composite resin and ceramic. HF is also a more effective roughening agent than other acids because it partially dissolves the silica phase of the ceramic surface. Previous studies have also found that HF etching promotes morphologic alteration of the ceramic surface, increasing the total surface area and surface energies.,, This mechanical interlocking maintains the ceramic-to-resin bond and improves the bond strength between the resin and the ceramic surface. HF etching of ceramic surfaces resulted in more rough areas and a significant increase in RBS compared with untreated surfaces. These findings are supported by the current study's SEM data. HF etching of the ceramic surface followed by silane application could result in an acceptable bond between the ceramic and CR. In the current study, results agreed with those of Hakimaneg et al., Shiu et al., and Akyıl et al.,, Some researchers also suggested that OF etching on ceramic surface followed by silane use did not improve the CR–ceramic bond., In parallel with Shiu et al.'s results, bond strength values decreased in our study's OF group.
The application of silane coupling agents is preferred for chemical bonding to increase the wettability of ceramic surfaces due to the bond between silicon dioxide groups on the ceramic surface and methacrylate groups in the resin cement. The fact that mechanical treatments and silane coupling agents increase ceramic's bond strength has been demonstrated in previous studies.,, However, previous studies have shown that silane may decrease retention by changing the structure of the composite resin's matrix., This study used a single-bond silane, and RBS values significantly increased in the HF and 3W groups. These results agreed with those of Melo et al., Hayakawa et al., and Kupiec et al.,,
Laser etching is a simple and effective surface treatment technique. To date, numerous studies have been published about the effects of various laser power settings on the bond strength with composite resin, resin cement, and the roughness of ceramic.,,, One study used three pulse durations at 5W for Er: YAG laser irradiation, whereas another assessed surfaces treated with settings of 3 W, 10 Hz, and 1 min. Shiu et al. evaluated Er:YAG laser treatment of feldspathic ceramic using 500 mJ pulses at a frequency of 4 Hz, and Eduardo et al. applied Er, Cr:YSGG laser treatments using different parameters. These studies illustrate the lack of consensus on appropriate power settings for laser irradiation.
Burnett et al. used Er: YAG laser irradiation at 200 mJ and 10 Hz to increase the roughness of ceramic surfaces and increase the tensile bond strength of resin because of the presence of chemical elements on the ceramic surface that increased ablation. Shiu et al. and Akyıl et al. reported that Er:YAG laser irradiation did not significantly affect ceramic bond strength values., Similarly, Eduardo et al. showed that 0.5–5 W Er, Cr: YSGG laser applications at 20 Hz decreased the microtensile bond strength of composite resin to glass-infiltrated alumina compared with the untreated group. Previous studies also observed that different laser systems (Nd:YAG and CO2) produced mild alterations to the ceramic surface, and combined techniques (Nd:YAG and HF, Er:YAG and Al2O3 and Er:YAG and HF) for ceramic surface treatment resulted in increased surface roughness and decreased superficial resistance.,, In the present study, each laser power level resulted in a different surface morphology. For high laser power (3W) with temperature changes, the surface showed more irregularities, including depressions and cracks, whereas the surfaces of the control group and the low-power groups were smooth and homogenous and had little surface roughness. Treatment at 1W and 2W did not cause sufficient roughness on the ceramic's surface. This could be attributed to the vaporization and absorption of the energy effect of laser treatments on the ceramic, resulting in micro- or macro- crack as well as rough areas on the composite surface. Therefore, the present study showed that the RBS on the 3W groups was increased in comparison with the control group, which was statistically significant except in the case of the HF group. This findings is in accordance with Burnett et al.'s study. Contrarily, previous studies have shown that a durable RBS of ceramic is achieved after sandblasting and acid etching., This could be attributed to the damage of ceramic surface as a result of the inefficient irradiation of laser treatment and leaving the filler particles bare of silane. Contrary to the results of the present study, combined techniques (Er:YAG + HF and Nd:YAG + HF) applied to a ceramic surface showed more rough areas (fissures and micro crack formations) and a significant increase in bond strength compared with an untreated surface, and the SEM data support these findings. The fissures, cracks, and melting areas on the 3W surface were larger than those on the other laser group's surface, so it seems that the laser power may affect the adhesion outcome. The RBS values and the surface's SEM images showed significant differences among the low powers amounts tested. However, the effect of combined techniques (various powers + HF or OF) on ceramics have not been investigated yet.
Various factors affect the adhesion of ceramic and CR, including the materials' compositions, wetting properties, surface energy, and surface roughness. Previous studies reported that the surface energy and wettability of an adhesive increases when laser irradiation is used in a process called “ablation,” which is designed to remove the chemical elements, such as water and hydroxyl radicals, on the surface., On the other hand, a correlation was found between the RBS and surface roughness results in the laser group. Hence, the high RBS observed in the ceramic/CR interface can be explained by surface roughness. However, other additional parameters must be evaluated as well. Similar results were obtained in the present study.
In the current study, the fracture type observed was mostly adhesive and cohesive failure (HF and 3W group) at the interface, which is in agreement with the results of Akyıl et al. and Shiu et al. The present study suggests that the laser's other parameters (different pulse durations, application times, etc.) could be preferred as alternative treatment methods to HF etching to prevent macro-crack formation and damage to the surface of ceramic in the bonding area for the longevity of ceramic restorations' repair. No studies have been done on the effects of various laser power amounts on ceramic with RBS, and conflicting results have also been observed in the related studies.,, Thus, the current study's results could enrich existing the literature.
The limitation of the present study is the effect of sandblasting, which could have a significant effect on a ceramic surface, such as temperature changes in the mouth before the surface treatments, as well as surface roughness analyses using a profilometer and AFM evaluation. These effects were not investigated in the current study and could be important for clinical trials. Additionally, other surface treatments before the longer thermal cycles test are needed for RBS analyses.
| Conclusion|| |
Within the limitations of the current study, the following conclusions could be reported:
- HF and Er, Cr:YSGG laser irradiation at 3 W obtained an appropriate bond strength for the ceramic surface, due to significant differences observed among the applied surface treatments in this group.
- Er; Cr:YSGG laser irradiation at 1W and 2W did not deleteriously impact the RBS of the evaluated ceramic. However, it promoted surface topography alterations.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]