|Year : 2022 | Volume
| Issue : 1 | Page : 37-43
The Effect of Different Surface Roughening Systems on the Micro-Shear Bond Strength of Aged Resin Composites
OI Karadaglioglu, L Gulec Alagoz, A Caliskan, G Aksoy Vaizoglu
Department of Restorative Dentistry, Near East University, Faculty of Dentistry, Nicosia, Turkish Republic of Northern Cyprus, Turkey
|Date of Submission||25-Feb-2021|
|Date of Acceptance||22-Jul-2021|
|Date of Web Publication||19-Jan-2022|
Dr. O I Karadaglioglu
Near East University Faculty of Dentistry, Department of Restorative Dentistry, Near East Boulevard, Nicosia, Mersin, 10
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: There are controversies regarding the most effective surface treatment method to be applied for the effective repair of resin composites. Aims: This study aimed to compare the effects of surface roughening processes on repair bond strength of different types of aged composites. Water aging was applied to 60 nanohybrid and 60 micro-hybrid resin composite samples for 1 year. Samples were randomly divided into five groups and four types of roughening processes. Bur, OPTIDISC, SUPERSNAP, and BISCO were applied to the water-aged resin composite samples. Micro-shear test method was used to measure the repair bond strength. Materials and Methods: Data were analyzed with IBM SPSS V23. Compliance with normal distribution was examined by Kolmogorov–Smirnov test. Two-way analysis of variance (ANOVA) and Tukey HSD test for multiple comparisons were used. Results: The main effect of the type of resin composites and surface roughening methods were found to be significantly different. The MPa values of surface roughening groups were similar while the lowest mean value was obtained for the untreated group of the nanohybrid resin composite (P < 0.001). The bond strength for both resin composites was generally considered within acceptable limits except for no treatment group of nanohybrid resin composite. Conclusions: This study showed that surface roughening method is mandatory for effective bond strength and the type of fillers in resin composite affects the micro-shear bond strength.
Keywords: Bond strength, repair, resin composite, surface roughness, water aged
|How to cite this article:|
Karadaglioglu O I, Alagoz L G, Caliskan A, Vaizoglu G A. The Effect of Different Surface Roughening Systems on the Micro-Shear Bond Strength of Aged Resin Composites. Niger J Clin Pract 2022;25:37-43
|How to cite this URL:|
Karadaglioglu O I, Alagoz L G, Caliskan A, Vaizoglu G A. The Effect of Different Surface Roughening Systems on the Micro-Shear Bond Strength of Aged Resin Composites. Niger J Clin Pract [serial online] 2022 [cited 2023 Jan 26];25:37-43. Available from: https://www.njcponline.com/text.asp?2022/25/1/37/335997
| Introduction|| |
One of the goals of modern restorative dentistry is to make life-long restorations while preserving sound dental tissue as much as possible. However, this is not the case in clinical practice. The duration of restoration is affected by several factors such as the clinical aspect, the ability of the operator, and the properties of the materials used. A clinician should know the fact that almost every restoration performed may deteriorate.
It was reported that dentists commonly renovate failed restorations 10 years after placement. However, the replacement of restorations can cause significant damage to sound tooth tissue if the preparation is expanded. In this case, the longevity of the tooth vitality is negatively affected and can cause injury of the dentin-pulp complex. Additionally, this application is time-consuming.
Modern dental treatment approaches suggest repair procedures for suspicious restorations as alternative methods., Repair is a part of the “Minimally Invasive Dentistry” concept that aims to preserve sound tooth tissue, reduce invasive attempts, and keep the teeth in function. In this case, the bond strength between restorative material and repair material becomes important.
The interface between old restorations and repair materials can be defined as “the weakest link” that can create fragility to the intraoral forces. For this reason, it is necessary to increase the bond strength to prevent microleakage and provide ideal adaptation.
To ensure bonding between layers of composite materials, an oxygen-free polymerized resin layer must present. Since aged restorations do not contain this layer, various methods are suggested to increase the bond strength of materials. Surface roughening is one of these treatment methods. Surface roughening methods stated as; roughening with diamond bur, and grinding with silicon paper, sandblasting, roughening with discs, air abrasion with aluminum oxide or silica particles and chemical applications with phosphoric acid or hydrofluoric acid.,
In light of the general information given above, this study aims to evaluate the effect of surface roughening with coarse diamond bur and discs on the bond strength of two different aged composite resins. The first hypothesis about the study is that the micro-shear bond strength of resin composites with different filler types will be different. The second hypothesis is that the most abrasive disc of three different sets made of different materials will provide more effective micro-shear bond strength compared to a diamond bur.
| Material and Methods|| |
In this study, a total of 120 resin composite specimens including 60 microhybrid resin composite (Filtek Z250, 3M ESPE, St. Paul, MN, USA) and 60 nanohybrid resin composite (Clearfil Majesty Esthetic, Kuraray, Japan) were used. A metal mold in 8 mm diameter and 2 mm height was fixed on a glass slab with a transparent mylar strip (Universal Strip, DML, Germany) below it and the microhybrid and nanohybrid resin composite materials were condensed in it. After condensation, another transparent mylar strip was placed on the top of the surface before curing to obtain a smooth surface. The specimens were then polymerized with a light-emitting diode (LED) unit (Woodpecker, Led.B, Curing Light, China) for 40 s at 1000 mW/cm2 and then removed from the mold. All of the specimens were polished with Super-Snap Rainbow Kit (Shofu, Tokyo, Japan) as instructed. The prepared samples were incubated (FN 400, Nuve, Ankara, Turkey) at 37°C for 1 year in distilled water. Care was taken to ensure that the samples were covered with water. Water was changed once a week to prevent bacterial growth. After 1 year all of the samples were then glued on acrylic blocks. Then each composite group (n = 60) was further divided into 5 groups (n = 12) according to their surface roughening methods. The groups were as follows;
Scotchbond Universal Adhesive (3M ESPE, St. Paul, MN, USA) was applied on each specimen by rubbing the micro-brush for 20 s, gently air-dried for approximately 5 s to evaporate the solvent and light-cured for 10 s.
In this group, a diamond coarse brown disc of BISCO (Schaumburg, IL, USA) was used with a low-speed hand-piece under water-cooling for surface roughening. The discs were applied to each specimen as three strikes and a new disc was used in every four composite resin specimens. Scotchbond Universal Adhesive was then applied for 20 s, gently air-dried for approximately 5 s to evaporate the solvent and light-cured for 10 s.
In this group, aluminum oxide extra coarse disc of OPTIDISC (Kerr, Bioffio, Switzerland) was used with low-speed hand-piece under water cooling for surface roughening. The disc was applied to each specimen as three strikes and a new disc was used in every four resin composite discs. Scotchbond Universal Adhesive was applied for 20 s, gently air-dried for 5 s. and light-cured for 10 s.
In this group, silicon carbide and aluminum oxide coarse disc of Super-Snap Rainbow Kit was used with low-speed handpiece under water-cooling. Then, Scotchbond Universal Adhesive was applied as specified in previous groups.
In this group, green-banded diamond bur with coarse grain size (Meisinger Dental, Germany) was used for surface roughening. Then, the same procedures were applied as in the previous groups.
After adhesive application, three cylindrical polyethylene Tygon tubes were placed on each specimen at three different locations and light cured. The diameter and height of polyethylene Tygon tubes were 1 mm. Then, nanohybrid resin composites (Clearfil Majesty Esthetic) were applied into cylindrical tubes and light-cured for 20 s. After curing, tubes are removed carefully with a sharp lancet obtaining resin composite cylinders. All specimens were stored in distilled water at 37°C for 24 h.
A micro-shear bond strength (μSBS) test was accomplished with a universal test machine (EZ-test-500N Shimadzu, Kyoto, Japan) at a crossed speed of 1 mm/min. A thin wire (0,2 mm in diameter) was looped around each cylindrical-shaped resin cylinder in contact with the cylinder base. Force was directly applied to the resin cylinders until the occurrence of failure. The center of the load cell and the wire loop was positioned as straight as possible to ensure the desired orientation for micro-shear test stress. Micro-shear bond strengths were expressed in Megapascale (MPa), as derived from dividing the maximum load (N) at the time of failure by the adhesion area (mm2).
Data were analyzed with IBM SPSS V23. Compliance with normal distribution was examined by Kolmogorov–Smirnov test. Two-way analysis of variance (ANOVA) and Tukey HSD test for multiple comparisons were used to compare MPa values according to resin composite type and surface roughness. The results of the analysis were presented as mean ± s deviation for quantitative data. The significance level was taken as P < 0.05.
| Results|| |
The two-way ANOVA results showed that the main effect of the type of resin composite on MPA values was observed significantly different (P < 0,001) [Table 1]. The mean value of Filtek Z250 (26.05 MPa) was higher than the mean value of Clearfil Majesty Esthetic (19.7 MPa) indicating a significant difference. Additionally, the main effect of the surface treatment procedures were found to be significantly effective on MPA values (P < 0,001) [Table 1]. This difference could be due to the fact that the mean value of the no treatment group is lower than the average of surface roughening groups [Table 2].
|Table 1: Two-way ANOVA results for the comparison of the MPA values of resin composite types and surface roughening methods|
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|Table 2: The mean values±standard deviations of the groups and multiple comparisons of MPA values|
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The interaction of resin composite and surface roughening method was found to be statistically significant on MPA values (P = 0.001) [Table 1]. While the highest MPa mean value (29,47 MPa) was obtained in the BISCO group of the Filtek Z250, the lowest mean value (12,84 MPa) was obtained for the No Treatment group of Clearfil Majesty Esthetic [Table 2].
Number of failure modes of the tested materials is shown in [Table 3]. According to the results, the most observed fracture patterns were cohesive type failures for both Filtek Z250 (42%) and Clearfil Majesty Esthetic (54%). In no treatment groups, Filtek Z250 exhibited equal rates of failures (33%) for all three types and Clearfil Majesty Esthetic showed 61% of adhesive type failure.
|Table 3: Fracture modes of specimens after micro-shear bond strength test|
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| Discussion|| |
Resin composites, introduced in the 1960s, have become more popular over time and nowadays, they are the most preferred materials for direct restorations of both anterior and posterior teeth. Studies evaluating the clinical life of posterior and anterior composite restorations showed that their clinical performance was sufficient and additionally, it was stated that the ratios of their annual clinical failure differed from 1% to 4%., The most common causes of failure for resin composites have been reported as fractures of restorative materials and formation of secondary caries.
With the introduction of adhesive systems in dentistry, minimally invasive techniques have been preferred and in recent years, instead of removing the whole restoration, it has been suggested to repair only the defective part. Thus, it has been aimed to prevent problems such as redundant extension of preparation, pulpal damage, prolongation of treatment time, and increase of treatment cost. The most important factor that affects the repair success for a defective restoration is providing a safe bonding between pre-existing restoration and the repair material.
Several surface treatment methods have been used for obtaining macro-mechanic, micro-mechanic, or chemical bonding between pre-existing restoration and repair material. Nowadays, various studies conducted about repair procedures are related to convenient surface treatment methods that are applied to defective restorations. There is not a clear consensus concerning the best surface treatment method to be applied for the repair procedures and this situation makes the subject debatable. Therefore, the aim of this study was to investigate the effect of various surface roughening methods on the repair bond strength of two types of resin composites.
Modern adhesive dentistry offers important advantages such as preserving the sound tooth tissue and increasing the durability of the restoration. A strong adhesion between restorative resin and the tooth structure is the main goal of adhesive dentistry. Strong evidence has been obtained that the bond strength between new and old resin composite increases when dentin bonding agents are used in the repair procedure. In clinical practice, a variety of materials are required to be used in the repair of aged composite restorations to ensure adequate adhesion strength. “Universal adhesives” are one of the newest categories in adhesive dentistry. Universal adhesives are produced to bond to the tooth structure and restorative materials with several techniques without requiring additional primer application. These adhesives are easy to use, they can be applied faster and are less technique sensitive compared with multi-step adhesives. Several researchers reported the benefits of universal adhesives on the bond strength of resin composites., It has also been stated that the silane, incorporated in universal adhesives, increases the bond between the organic resin matrix and the fillers and is effective in obtaining durable restorations by increasing adhesion., Thus, a universal adhesive, Scotchbond Universal Adhesive was used in this study.
The effect of different types of resin composites for repair procedures has been studied for years., The properties of the composite material used in pre-existing restorations are one of the important factors that affect the success of the repair procedure to be applied. Microhybrid resin composites are a combination of universal composites containing 0.04 μm sized silica fillers and 0.4–0.7 μm sized glass fillers. These materials have wear resistance and high strength. Also, they can be polished very well. When evaluated clinically, they perform well in terms of surface texture, marginal integrity, anatomical form, and color match.
Esthetic features and ease of use made micro-hybrid resin composites a good alternative to the prior composite restorative materials. Increased esthetic demands of patients have led to the production of nanohybrid composites that increase the surface properties of restorations with changes in the formulation of fillers. Nanohybrid resin composites with nano-sized fillers present some advantages such as strength, low polymerization shrinkage, high polishability and high esthetic properties, due to their increased filler contents. In this study, microhybrid composites (Filtek Z250), which are durable materials as well as acceptable esthetic properties, and nanohybrid composites (Clearfil Majesty Esthetic) with esthetically superior properties were used as pre-existing restorative materials. In a study, Özcan et al., compared the shear bond strength of microhybrid and nanohybrid resin composites and reported that they showed similar bond strength values in early repairs. However, Junior et al. stated that the aged microhybrid composites exhibited higher micro-tensile bond strength values compared to aged nanohybrid composite resins. Similar to the results of Junior et al's study, the micro-hybrid composite (26,05 MPa) exhibited higher micro-shear bond strength values than nano-hybrid resin composite (19,7 MPa) in our study. Thus, the first hypothesis is accepted. The difference between Özcan et al's and our results can be related to the aging process. Özcan et al., concluded that their results are effective in early repairs but in our study, we aged the samples for 1 year.
Some researchers preferred different repair materials from pre-existing restorative materials because it is often not possible to know the type of pre-existing resin composite to be repaired under clinical conditions., In the literature repair procedures of nanohybrid resin composites stated. In a study conducted in 2015, nanohybrid cylinder specimens were aged in distilled water for 24 hours and treated with several surface treatment methods. After the surface treatments, repair applications were demonstrated on these samples with nanohybrid, microhybrid and microfilled composites. The results showed that nanohybrid resin composites showed the highest shear bond strength. Nano-hybrid resin composites were used as repair material in our study. Repair bond strength of nanohybrid resin composite to the tested specimens was between 19,88 MPa and 29,47 MPa except for no treatment group of Clearfil Majesty Esthetic (12.84 MPa). Acceptable bond strength threshold values for repairability are specified in the literature as 15 to 25 MPa. Since the values of all tested specimens except no treatment group of Clearfil Majesty Esthetic were above the specified limit, it can be interpreted that nanohybrid resin composite can be suitable as a repair material except for no treatment group of Clearfil Majesty Esthetic.
Surface treatment methods applied to old restorations significantly affect the bond strength. The purpose of the surface treatments performed was to increase the surface roughness. Roughening with diamond bur is the most commonly used surface treatment method and its use is suggested clinically in the repair of resin composite restorations since it is more effective than other treatment methods. However, there is not a standardized grain size for the diamond bur to be used. It is only known that particle size should be between 25 to 100 μm for roughening. The fact that the diamond bur is an effective surface roughening method has led us to question the effect of roughening with the most abrasive discs of 3 types of finishing and polishing systems. To the best of our knowledge, the information about the effect of surface treatment with discs was very limited. In this study, the effect on the micro-shear bond strength of diamond bur, diamond discs, aluminum oxide abrasive particles containing discs and silicon carbide abrasive particles containing discs with coarse or extra-coarse grain sizes were compared. The results of the study showed that the “no treatment” groups exhibited statistically lower micro-shear bond strength values than the other surface treatment groups. These results highlight the necessity of surface roughening for the repair of resin composites. Since there is not a significant difference between surface roughening groups, it can be interpreted that discs can be used as effectively as diamond bur in case of surface treatment. Also, it can be concluded that the grain size and the material of the grain are not important for the surface roughening procedures. Thus, the second hypothesis is rejected.
Artificial aging methods allow the deterioration of materials that can be observed in longer periods to be evaluated in a short time. Researchers used several methods to duplicate the aging process of resin composites, such as immersion in artificial saliva, storage of the material in acids at 37°C, thermocycling, water immersion., Some researchers chose the thermal method for aging,, while most researchers chose the water aging method., In this study, the samples were stored in distilled water for 1 year and the water aging technique was simulated as many researchers do., Water aging method may cause some alterations in the resin composite samples as the absorption of water by the resin matrix makes the composite resin more flexible.
In No Treatment groups that the lowest micro-shear bond strength values were obtained, the highest frequency of failure seen for nanohybrid resin composite was adhesive and the lowest frequency seen was cohesive whereas equal failure frequencies were seen in micro-hybrid groups. In surface-treated groups, that had significantly higher bond strength values than control groups but similar bond strength values among each other, cohesive failure types were seen mainly for both resin composites. In a study in which the microshear and microtensile bond strengths of the same samples were measured, it was reported that less adhesive failure was found in the microshear test method, and more adhesive failure was observed in the microtensile test method. Observation of more cohesive failures in our study may be due to the microshear test method used. The microshear test method was chosen in this study because of its advantages such as being a simple test method, having lower incidence of pre-testing failures and ease in the specimen preparation. However, as the failure occurs at a different location from the interface due to the concentration of stress on the substrate material may affect the results that can be specified as a limitation for this study. It can be recommended to support the study with different bond strength tests in order to get effective results.
The other limitations of this study can be attributed to the use of one type resin composite as repair material. Since each type of resin composite has different physical properties, using a different resin composite as a repair material may affect the results. Apart from that, using different types of aging methods combined with the water aging method will simulate the clinical conditions better and this could lead to more reliable results.
| Conclusions|| |
When the data obtained from the study are evaluated it can be concluded that the filler type of resin composite affects the bond strength, the micro-shear bond strength values of both types of composites are within repairable limits except no treatment group of nanohybrid composite and surface roughening is mandatory for an effective repair bond strength.
Key Messages: Surface roughness would be required for the repair process in aged resin composites, and the use of finishing discs for roughening will be as effective as using a bur.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]