|Year : 2019 | Volume
| Issue : 10 | Page : 1441-1447
Effect of surface treatments to remove temporary cement remnants on the bond strength between the core composite and resin cement
SH Altintas1, K Hamiyet2, S Kilic3
1 Department of Prosthodontics, Faculty of Dentistry, Karadeniz Technical University, Trabzon, Turkey
2 Department of Prostodontics, Faculty of Dentistry, Abant Izzet Baysal University, Bolu, Turkey
3 Department of Prosthodontics, Faculty of Dentistry, Kocaeli University, Kocaeli, Turkey
|Date of Acceptance||03-Jun-2019|
|Date of Web Publication||14-Oct-2019|
Dr. S H Altintas
Department of Prosthodontics, Faculty of Dentistry, Karadeniz Technical University, Trabzon - 61080
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: There was no enough data about the appropriate surface cleaning of core composite material after temporary cementation. Aim: To evaluate the effects of surface cleaning techniques on initial shear bond strength (SBS) between core composite material and resin nanoceramic crown materials after temporary cementation. Material and Methods: Cubic specimens were prepared from prosthetic materials, including Lava Ultimate. Cylinder-shaped composites were cemented to glass slides with eugenol-free temporary cement, resulting in a total of 44 cylinders (n = 11). The surfaces of composite cylinders were then cleaned with an Er, Cr:YSGG laser, 37% orthophosphoric acid, yellow tape diamond bur, or dental explorer. Cleaned cylinders were bonded to cubic specimens with resin cement. Initial SBS tests were performed with a universal testing machine at 0.5 mm/min crosshead speed. One-way ANOVA and post hoc Tukey tests were used to analyze the obtained data (P =0.05). Results: Initial SBS values were significantly affected by the different surface cleaning methods (P <.05). The highest SBS value was obtained with the laser group (SBS = 17.14), while the lowest was obtained with dental explorer group (SBS = 5.95). There was no significant difference between the diamond bur group and the laser group (P =0.982). Conclusions: Laser irradiation or yellow tape diamond bur cleaning of the core composite surface could be recommended to strengthen bond strength between the resin luting cement and the core composite. Before adhesive or conventional cementation of prosthetic restoration, the core composite surface should be cleaned.
Keywords: Core composite, dimond bur, Er, Cr:YSGG laser, surface treatment, temporary cement
|How to cite this article:|
Altintas S H, Hamiyet K, Kilic S. Effect of surface treatments to remove temporary cement remnants on the bond strength between the core composite and resin cement. Niger J Clin Pract 2019;22:1441-7
|How to cite this URL:|
Altintas S H, Hamiyet K, Kilic S. Effect of surface treatments to remove temporary cement remnants on the bond strength between the core composite and resin cement. Niger J Clin Pract [serial online] 2019 [cited 2020 May 26];22:1441-7. Available from: http://www.njcponline.com/text.asp?2019/22/10/1441/269009
| Introduction|| |
When completing bonding a resin to a tooth in a single session, it is possible to ensure a contaminant-free bonding surface of prepared tooth. However, in cases of restoration that could not be completed on the same day, usually a temporary prosthesis is made and cemented with a temporary cement material to satisfy the functional and esthetic demands of patients and to prevent sensitivity of the tooth.,
It has been reported in several previous studies that the temporary cement remnant remaining on the abutment surface adversely affects the connection quality between restoration and dental structures, resulting in bonding failure. Removal of temporary cement improves the bond strength and protects the dental and gingival structure by reducing microleakage., Thus, proper cleaning of the prepared tooth surface is an important issue that should be given consideration.
Teeth with insufficient hard tissue in the coronal region are generally prepared for crown restoration. These teeth, regardless of whether they were vital, may contain large amounts of resin composite material as core build-up. A variety of procedures that typically require multiple appointments have been suggested for such cases. During these appointments, the surface of the core composite is contaminated by saliva and temporary luting agents. As temporary cementation is required between these appointments, it is important to know the effects of surface cleaning techniques on the resin composite material as well as the dentinal structure. Several studies have reported different techniques to improve bond strength to contaminated and polymerized composite resin.,,,,,
Many cleaning techniques used for the abutment tooth surface have been examined by several previous studies, and they are mainly based on mechanical and/or chemical patterns.,, Great efforts are being made to strengthen the connection between the abutment tooth and the restoration, which is created by alternative mechanical and chemical modifications of the bonding surface. The most common methods for mechanical cleaning include the use of carving instruments, yellow tape diamond burs, and airborne-particle abrasion. In addition, conditioning of the abutment surface with orthophosphoric acid, which was used as chemical surface treatment by earlier studies, could be clinically beneficial to the formation of a durable connection between the restoration and abutment tooth by penetration of the cement into surface pits., It has also been reported that the use of laser therapy with adhesive materials was effective in improving bond strength. Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet (Er, Cr:YSGG) laser pretreatment enhances the bonding properties of resin containing materials by creating microretentive areas, as shown by previous studies.,,
Several studies that investigated the efficiency of cleaning methods for the dentinal surface are available in the literature.,,, However, most recent investigations are limited to comparing the effects of different cleaning techniques on the core composite material, and only a few studies have an experimental group using Er, Cr:YSGG laser as a surface cleaning technique. As there are insufficient data about the appropriate surface cleaning of core composite material after temporary cementation, further assessment is still needed. Therefore, the purpose of this in vitro study was to evaluate the effects of four surface cleaning techniques on initial shear bond strength (SBS) between the core composite material and resin cement after temporary cementation. The hypothesis was: differences would be found among the effects of different surface cleaning methods on the bond strength of temporary cement contaminated core composite to resin cement.
| Material and Methods|| |
[Table 1] presents the brand names, composition and manufacturers of the materials used in the present study.
Cubic specimens (6 × 6 × 6 mm 3; n = 44) were prepared from prosthetic material: resin nanoceramic (Lava Ultimate, 3M ESPE, St. Paul, MN, USA). Resin nanoceramic specimens were cut with a low-speed precision cutting device (Micracut 125 Low Speed Precision Cutter; Metkon, Bursa, Turkey) and a diamond blade under water cooling. Surfaces of all cubic specimens were wet-polished with 800 and 1200 grit silicon carbide papers for 2 minutes to create a baseline roughness for all prosthetic materials. They were then ultrasonically cleaned in distilled water for 10 minutes and air dried.
To prepare composite cylinders, rubber cylinder tubes were filled with resin composite material (Tetric EvoFlow, Ivoclar Vivadent, Austria) using a layering technique, and then the cylinders were photopolymerized (Hilux Ultra Curing Unit, Benlioglu Dental Inc., Ankara, Turkey) at 550 mW/cm 2 for 40 seconds. The composite cylinders (3 mm diameter and 5 mm height; n = 44) were removed from the tubes and repolymerized from all sides. They were wet-polished with 340 grit silicon carbide paper, cleaned ultrasonically in distilled water for 10 minutes and air dried. The composite cylinders were cemented to glass slides with eugenol-free temporary cement (Dycal, Dentsply Caulk, DE, USA) under finger pressure, as in clinical practice, for 2 minutes. They were stored in an incubator at 37 ± 2°C for 24 hours. After composite cylinders were separated from the glass slides, they were divided into four subgroups by simple randomization (n = 11). All procedures were carried out by one clinician following recommendations of the manufacturer.
Surface cleaning techniques
The surfaces of the composite cylinders were cleaned with four cleaning techniques as follows:
Group 1: Applying Er, Cr:YSGG laser (Waterlase MD, Biolase, Irvine, CA, USA) irradiation with 2780 nm wavelength, 20 mHz frequency, 3 W power, 15 mJ energy and 119.42 J/cm 2 energy density with 50% water and 60% air in contact mode. The distance from the surface was minimal, and the hand piece was moved with a sweeping motion. The quartz mz tip with 800 μm diameter (Waterlase MD, Biolase, Irvine, CA, USA) was used. Group 2: Etching with 37% orthophosphoric acid (Total Etch; Ivoclar Vivadent, Schaan, Liechtenshein) for 15 seconds according to the manufacturer's instructions. Group 3: Treating with a yellow tape diamond bur (Komet Dental Gebr. Brasseler GmbH and Co. KG, Lemgo, Germany) at 10,000 rpm for 3 seconds placed tangential to the surface under water cooling. Group 4: Mechanically cleaning with a dental explorer until the surface was macroscopically clean.
Forty-four cubic resin nanoceramic blocks were used for the experiments in this study. A cleaned composite cylinder was bonded to each experimental surface of cubic specimens. All bonding procedures were carried out using a resin cement kit (Panavia F 2.0 Complete Kit, Kuraray Medical Inc., Japan). Cementation of resin nano ceramic and core composite specimens with Panavia F 2.0 were performed according to manufacturer instructions. All specimens were stored in an incubator at 37 ± 2°C for 24 hours until SBS test.
A custom-made specimen holder was produced for cubic specimens [Figure 1]. SBS tests were performed with a universal testing machine (Instron Corp., Canton, MA, USA) at 0.5 mm/min crosshead speed. The shear force was applied to the cubic specimen-composite interface with a knife-edge shearing rod until bonding failure occurred. The load at the time of failure was recorded digitally in Newton (N) for each composite cylinder. The initial SBS value was then calculated in MPa according to the following formula:
Stress = Failure load (N)/Adhesive surface area (mm 2).
Scanning electron microscopy evaluation
The randomly selected composite resin specimens, which were cleaned with surface cleaning techniques, were positioned on the aluminum plate using a double-sided adhesive conductive carbon band. Specimens were gold sputter-coated and observed under a field emission SEM (Zeiss Evo LS10, Bruker, Bremen, Germany) equipped with a SE (secondary electron) detector by a single operator.
Failure modes of initial SBS of all specimens were evaluated by a single operator under a field emission SEM described as above and categorized into one of two types: adhesive (at the core composite/resin cement or resin nanoceramic/resin cement) or cohesive (within core composite, resin cement or resin nanoceramic).
Statistical analyses were performed using statistical software (SPSS Statistics for Windows v17.0; SPSS Inc). The normality of data was analyzed using the Mann-Whitney Test. Because of the parametric distribution of the dataset, one-way ANOVA was used to analyze the differences among materials and among the different cleaning methods. A post hoc Tukey test was applied to determine statistically significant differences between materials and cleaning methods. P <.05 was considered to be statistically significant in all tests.
| Results|| |
The means and standard deviations for SBS values and statistical significance among groups cleaned with different techniques were presented in [Table 2] and [Figure 1]. Initial SBS values were significantly affected by the surface cleaning methods (P <.001), as shown in [Table 3].
|Table 3: The means and standard deviations for SBS values (MPa) and statistical significance among groups|
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The highest mean SBS value was obtained in the Er, Cr:YSGG laser group (SBS = 17.14), while the lowest was obtained in the dental explorer group (SBS = 5.95; P = 0.00) [Table 3].
There were no statistically significant differences among the Er, Cr:YSGG laser and yellow tape diamond bur groups (P = 0.982). There were no statistically significant differences between groups E and C (P = 0.063).
[Figure 2] presents micrographs of the core composite surfaces formed by the four surface treatments. Except for the Er, Cr:YSGG laser and yellow tape diamond bur groups, which showed surface roughness, the groups had temporary cement remnants on the surfaces of the core composite [Figure 2].
|Figure 2: SEM images of the surfaces of composite cylinders after cleaning procedures. Core composite resin surfaces; (a) applied Er, Cr: YSGG Laser, (b) ground with yellow tape diamond bur (c) cleaned with dental explorer, temporary cement remnant is indicated by white arrow, (d) etched with orthophosphoric acid|
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The modes of failure for the specimens after the initial SBS test are presented in [Table 4]. Cohesive failures were more prevalent in the laser and bur groups. On the other hand, adhesive failures were more prevalent in the acid and dental explorer groups. However, only adhesive failures were seen in the dental explorer group [Figure 3].
|Figure 3: SEM images of the failure modes for the specimens; (a) adhesive failure (b) cohesive failure|
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| Discussion|| |
Based on the findings in the current study, SBS values were significantly affected by the different resin surface cleaning methods. Therefore, the results of this study support the hypothesis that differences would be found among the effects of different surface cleaning methods on the bond strength of temporary cement contaminated resin to prosthetic materials. Group C resulted in the lowest SBS (=5.95) for all surface cleaning procedures. This study clearly showed that using the laser was the most effective method for cleaning composite resin surfaces and creating appropriate physiochemical conditions.
The composite cylinders were prepared to represent the abutment tooth surface, and the cubic specimens were prepared to represent prosthetic restoration in this in vitro study. Therefore, two interfaces need to be considered: the composite resin-definitive cement and the definitive cement-prosthetic restoration interface. For the surface preparation of prosthetic materials, the recommendations of the related studies and manufacturer's instructions were followed., The surface cleaning methods tested by this study were used for the composite cylinders. The results of the current study have shown that the quality of the abutment surface has an important role in the longevity of the durable bond strength.
It has been reported that eugenol-containing cements have negative effects, which cause a weak interface, including changes in wettability and reactivity of the bonding surface. Altintas et al. evaluated the effect of three provisional cements and two cleaning techniques on the final bond strength of porcelain laminate veneers. They reported that calcium hydroxide based cement promoted higher bond strength than other temporary cements such as eugenol-free temporary cement and light-cured temporary cement for cleaning of dentin surface especially with dental explorer. However, Fonseca et al. stated that the calcium hydroxide cement promote a higher retentive strength between dentin and conventional provisional restoration. Higher retentive strength yields greater difficulty in later cement removable. This higher retentive strength of calcium hydroxide cement may produce greater difficulty of removing cement. Since the contradictory information on cleaning of calcium hydroxide cement, the calcium hydroxide cement was used as provisional cement in the current study.
When luting extracoronal restoration on prepared teeth or core composite, the surface of the core composite is contaminated by saliva and temporary luting agents. Thus, the choice of surface treatment type is essential for the long-term success of dental prosthetic restoration regarding the bond strength between luting agents and composite core material. Most previous studies evaluated the effects of mechanical and chemical surface treatments, such as diamond bur use, carving instrument implementation, airborne particle abrasion, and acid etching.,, Laser irradiation was another surface cleaning technique proposed by previous studies.,, In addition to caries removal and cavity preparation, the Er, Cr:YSGG laser was also used to increase surface roughness to enhance retention of resin restorative materials. However, limited data have been found about its use to remove the temporary cement remnants from the composite resin surface in post core restorations. In the present study, the SBS value obtained between resin composite and core composite specimens was found to be better with laser irradiation (SBS = 17.14). This result agreed with Ghavam et al., who reported that Er, Cr:YSGG laser irradiation improved the resin composite to resin composite repair bond strength when core composite was thought to be a composite containing material. Kimyai et al. reported that the Er, Cr:YSGG laser could be effective and was the best method in composite to composite bond compared to bur and sandblasting.
Surface treatment by diamond bur increases the bond strength compared to other techniques for tooth and composite materials due to increased surface roughness. In the present study, the bur group showed the best results with the laser group. This result is supported by the studies of Fawzy et al. and Cotes et al.. Using diamond burs is easy for removal of temporary cement remnants; however, it produced greater damage on the surface of the tooth or composite compared to the other mechanical methods. Although it is frequently used to roughen the surface of core and other composite materials, one must be careful to avoid internal misfit due to excessive grinding. On the other hand, several studies reported that grinding the composite with a bur resulted in smear layer formation.,,,,
Phosphoric acid etching is commonly used in adhesive dentistry during the repair of resin-based composite restorations. In addition, the usage of phosphoric acid etching is much safer than other etching materials, such as hydrofluoric acid, for intraoral use. Cotes et al. reported that there was no difference between the use of phosphoric acid for cleaning temporary cement remnants and the control group from core composite. This was the result of phosphoric acid etching that was limited to the superficial cleaning effect of composite surface, and it did not significantly change the morphological pattern of the aged composite resin. This was in agreement with our results; there was no difference between the dental explorer group and etching with phosphoric acid surface treatment group. We used the dental explorer group as a control group to simulate common clinical usage.
The laser and bur group showed the best SBS values and presented more cohesive failures. This type of failure usually indicates the clinical reliability of the bond strength. However, the dental explorer and etching groups showed more adhesive failures compared to the other groups. The fracture patterns revealed that laser treatment and use of the bur produced high SBS values, which are observed as cohesive failure.
The surface area can be increased with airborne-particle abrasion by forming microporosities, and definitive cement can penetrate and interlock these areas. However, during surface cleaning with airborne-particles, dust could be inhaled by the patient and dentist, leading to silicosis, a slowly regressive fibrotic disease of the lung, or the dust could be swallowed by patients. Therefore, we used other surface cleaning techniques, instead of silanated Al2O3 particles, to test less invasive options. Fawzy et al. investigated the effects of surface treatments on the tensile bond strength of repaired water-aged anterior restorative microfine hybrid resin composite.
The specimens used in this study had flat surfaces, and only one type of temporary and definitive cement was used, which are limitations of this study. The obtained results might be different with use of different luting materials and after aging processes. There were no available data in the literature regarding survival in occlusal function. Further studies are necessary to evaluate the effects of different luting materials on the bond strength of final restoration. Additionally, it would be beneficial to perform surface roughness and contact angle measurements in addition to shear tests in future investigations.
| Conclusions|| |
Within the limitations of this in vitro study, it might be concluded that the effect of surface treatment procedures for cleaning temporary cement remnants from the surface of a core composite is dependent on the type of surface treatment. Before adhesive cementation of prosthetic restoration, the core composite surface should be cleaned. Laser irradiation or yellow tape diamond bur cleaning of the core composite surface could be recommended to strengthen bond strength between the resin luting cement and the core composite.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]