|Year : 2012 | Volume
| Issue : 3 | Page : 164-169
Comparative evaluation of microleakage in Class V cavities using various glass ionomer cements: An in vitro study
Sunil Kumar Gupta1, Jaya Gupta2, Vidya Saraswathi1, Vasudev Ballal1, Shashi Rashmi Acharya1
1 Department of Conservative Dentistry and Endodontics, Melaka Manipal Medical College, Manipal, Manipal University, Karnataka, India
2 Faculty of Dentistry, Melaka Manipal Medical College, Manipal, Manipal University, Karnataka, India
|Date of Web Publication||11-Jun-2013|
Faculty of Dentistry, Melaka Manipal Medical College, Manipal, Manipal University, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: The study aimed to evaluate the microleakage of nano-filled resin-modified glass ionomer restorative (nano-filled RMGI) in comparison with that of conventional glass ionomer cement (CGIC), and resin-modified glass ionomer cement (RMGIC). Materials and Methods: Forty-five standardized Class V cavity preparations were prepared on sound extracted human molar teeth. Teeth were randomly assigned to three experimental groups of 15 teeth each and restored as follows: Group 1, CGIC; Group 2, RMGIC; and Group 3, nano-filled RMGI. The specimens were placed in a solution of 2% Rhodamine-B dye for 24 h at room temperature under vacuum. Staining along the tooth restoration interface was recorded. Results were analyzed using Kruskal-Wallis and Wilcoxon tests. Results: There were no statistically significant differences in dye leakage between all the three restorative materials for occlusal margins (P = 0.464). Group 3 showed significantly less microleakage compared to Group 1 (P = 0.007) and Group 2 (P = 0.040) at the gingival margins. The degree of microleakage in the gingival margins of each group was more than that found in occlusal margins. Conclusions: No material was able to completely eliminate microleakage at enamel, dentin, or cementum margin. Nano-filled RMGI showed least microleakage compared to other two cements at gingival margins.
Clinical Relevance to Interdisciplinary Dentistry
- Cervical lesions have been a restorative challenge for dentists for many years.
- An interdisciplinary treatment approach is the appropriate choice in cases where there is gingival recession and cervical lesions.
- Glass ionomer cements have been commonly used for restoration of cervical lesions.
- Nano-filled resin-modified glass ionomer cement can be used for the restoration of cervical lesions, as it has a better marginal sealing ability compared to conventional glass ionomer and resin-modified glass ionomer cements.
Keywords: Conventional glass ionomer cement, class V cavity, microleakage, nano-filled resin-modified glass ionomer, resin-modified glass ionomer cement
|How to cite this article:|
Gupta SK, Gupta J, Saraswathi V, Ballal V, Acharya SR. Comparative evaluation of microleakage in Class V cavities using various glass ionomer cements: An in vitro study. J Interdiscip Dentistry 2012;2:164-9
|How to cite this URL:|
Gupta SK, Gupta J, Saraswathi V, Ballal V, Acharya SR. Comparative evaluation of microleakage in Class V cavities using various glass ionomer cements: An in vitro study. J Interdiscip Dentistry [serial online] 2012 [cited 2019 May 27];2:164-9. Available from: http://www.jidonline.com/text.asp?2012/2/3/164/113245
| Introduction|| |
Over the past years, esthetic dentistry has shown considerable progress, leading to the development of a number of improved restorative materials. Currently, the main concerns regarding the performance of these materials refer to their durability and the integrity of marginal sealing, especially in cavities that involve the cementum region, where clinical problems are aggravated.
Microleakage is the movement of bacteria, fluids, molecules, or ions, and even air between the prepared cavity walls and the subsequently applied restorative materials. 
Cervical lesions have been a restorative challenge for dentists for many years. The complex morphology of Class V cavities with margins partly in enamel and partly in dentin presents a challenging scenario for the restorative material. The primary problem associated with the restoration of this kind of cavity is leakage at the gingival margin located in dentin. 
Bonded composites have been the common choice for the esthetic restoration of Class V lesions. However, one disadvantage of resin composite is polymerization shrinkage, which can result in marginal discrepancies leading to microleakage.  This shrinkage has clinical repercussions such as postoperative sensitivity, marginal discoloration, and secondary caries. 
Since the introduction of glass ionomer cements (GIC) in 1972, they have been widely used as restorative materials, luting cements and base materials.  These materials have widened the armamentarium of tooth-colored restorative materials, and in particular, they have been successfully used for restoration of cervical lesions.  Their main advantages are relative ease of use, bonding potential to enamel and dentin, and fluoride ion release.  Among the disadvantages are sensitivity to desiccation and moisture contact during the early setting stages. Glass ionomers are alternative materials to composites for the cervical lesions because of their chemical adhesion to tooth structure, fluoride release, biocompatibility, lower shrinkage values, reduced microleakage, and acceptable esthetics. ,
Resin-modified glass ionomer cements (RMGIC) were introduced to overcome the problems of moisture sensitivity and low early mechanical strengths associated with the conventional GIC (CGIC), which contain hydroxyethylmethacrylate (HEMA) or bisphenol-glycidyl methacrylate (BIS-GMA). 
Recently, nano-filled resin-modified glass ionomer (nano-filled RMGI; Ketac N100 nano light-curing glass ionomer restorative) was developed that combines the benefits of a resin-modified light-cured glass ionomer and bonded nanofiller technology. Nano-filled RMGI contains a unique combination of two types of surface-treated nanofillers (approximately 5-25 nm) and nanoclusters (approximately 1.0-1.6 μm). Nano-filled RMGI contains fluoroaluminosilicate glass, together with nanomers and nanoclusters in the filler loading, which is approximately 69% by weight.
The aim of the present study was to evaluate the microleakage of CGIC, RMGIC, and nano-filled RMGI at the occlusal and gingival margins of Class V cavities.
| Materials and Methods|| |
Forty-five extracted human molar teeth, free of visible caries, cracks, and restorations, were used in this study. All teeth were collected after obtaining ethical approval from Manipal University, Manipal. Surface debridement was done with hand-scaling instrument, cleaned with a rubber cup and slurry of pumice, disinfected in 0.5% chloramine, and subsequently stored in distilled water at 4°C until use. A standardized Class V cavity preparation was done on the buccal surface of each tooth. Preparations were made with an 835-010-4 ML cylindrical diamond bur (Diatech Dental, Coltène Whaldent AG, Alstδtten, Switzerland) under air-water cooling. The bur was replaced after every four preparations. The dimensions of the preparations measured 5 mm in length, 3 mm in width, and 2 mm in depth with the occlusal margin in enamel and the gingival margin in dentin. A William's graduated periodontal probe (Hu-friedy, Chicago, IL, USA) was used to gauge the dimensions of the cavity.
Subsequently, teeth were randomly assigned into three experimental groups (n = 15).
Group 1 - Restored with CGIC
Group 2 - Restored with RMGIC
Group 3 - Restored with nano-filled RMGI
In all cases, the manufacturer's instructions for dentin conditioning, powder/liquid proportioning, and mixing were strictly followed. The teeth were prevented from dehydration by immersing in distilled water at room temperature when not being prepared for restoration.
The commercial name, composition, and manufacturer of the materials used in this study are listed in [Table 1].
|Table 1: The commercial name, composition, and manufacturer of the materials used|
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For groups 1 and 2, the cavity wall was conditioned for 20 seconds with dentin conditioner (GC Corp., Tokyo, Japan). Both the cements were mixed according to the manufacturer's directions and were inserted into the cavity. Immediately after the restorations were placed, a transparent mylar matrix (Clear Thru; Premier Dental Products, Norristown, PA, USA) was adapted over GIC Fuji II restorations during the initial setting for 2 min, and for Fuji II LC, it was cured with an LED curing unit (Star Light Pro; Mectron Medical Technology, GE, Italy) for 20 seconds. The matrix was then removed and the unfinished restorations were immediately coated with GC Fuji varnish (GC Corp.) according to manufacturer's instructions. Excess material was removed with a BP knife (Magnia Marketing, Kanpur, India). Once the varnish was dried, the teeth were stored in distilled water for 24 h at 37°C. Then the restorations were finished to contour with finishing bur (SS White burs Inc., New Jersey, USA) with air-water spray in a high-speed handpiece. Later, medium, fine, and superfine Sof-Lex discs (3M ESPE, St. Paul, MN, USA) were used in sequence with air-water spray in a slow-speed handpiece. Teeth were then stored in distilled water at 37°C.
For Group 3, Ketac N100 nano-ionomer primer was applied for 15 seconds to moist enamel and dentin surfaces of the cavity. The primer was dried using an air syringe for 10 seconds. Primed surfaces were light cured for 10 seconds using the LED curing unit (Star Light Pro; Mectron Medical Technology). Cement was mixed according to the manufacturer's directions and was inserted into the cavity. Immediately after the restorative material was placed, a transparent mylar matrix (Clear Thru; Premier Dental Products) was adapted over the cement restoration and it was cured with a visible light-curing device (Star Light Pro; Mectron Medical Technology) for 20 seconds. The matrix was then removed. Restorations were finished in the same fashion as in groups 1 and 2. Teeth were then stored in distilled water at 37°C. Then all the teeth were subjected to a thermocycling regimen of 500 cycles between 5°C and 55°C, dwell time of 1 min, and 3-second transfer time between the baths. 
Preparation of samples for microleakage
The teeth were dried after thermocycling. The specimens were coated with two layers of nail varnish, leaving a 1 mm window around the cavity margins. During the process of placement of nail varnish, a moist cotton pellet was placed over the restoration to prevent desiccation. Teeth were inverted and placed in a solution of 2% Rhodamine-B dye (Reachem Laboratory Chemical Pvt Ltd, Chennai, India) for 24 h at 37°C under vacuum. In order to prevent leakage through the root apices, only the coronal portion of teeth was covered with the dye. After removal of the specimens from the dye solution, the surface-adhered dye was rinsed in tap water and nail varnish was removed with a BP blade. The teeth were sectioned longitudinally in a bucco-lingual direction through the center of the restorations using a water-cooled low-speed diamond disc (Horico, Berlin, Germany). The section with the greater leakage was evaluated with a stereomicroscope (M9; Wild Heerbrugg, Switzerland) at ×25 magnification to determine the extent of dye penetration at the occlusal and gingival margins by two evaluators who were blinded to the experimental groups.
Dye scoring criteria
The depth of dye penetration was analyzed according to a 0-3 scale scoring system as suggested by Silveira de Araϊjo C. 
Score 0 = No evidence of dye penetration
Score 1 = Dye penetration along the occlusal/gingival wall to less than half of the cavity depth
Score 2 = Dye penetration along the occlusal/gingival wall to more than half of the cavity depth, but not extending on to the axial wall
Score 3 = Dye penetration along the occlusal/gingival wall to the full cavity depth and extending on to the axial wall
All the above-mentioned dye scoring criteria for microleakage have been depicted in [Figure 1],[Figure 2],[Figure 3] and [Figure 4].
|Figure 2: Dye penetration along the occlusal/gingival wall to less than half of the cavity depth (score 1)|
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|Figure 3: Dye penetration along the occlusal/gingival wall to more than half of the cavity depth, but not extending on to the axial wall (score 2)|
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|Figure 4: Dye penetration along the occlusal/gingival wall to the full cavity depth and extending on to the axial wall (score 3)|
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Occlusal and gingival scores for each group of restoration were compared using Kruskal-Wallis one-way analysis of variance (ANOVA) to identify if any there was any statistical significant difference between the materials, and the Wilcoxon test was performed to compare each matched pair of restorative materials. Significance was considered at the ≤0.05 level.
| Results|| |
Microleakage scores for all the tested materials are presented in [Table 2].
Intergroup comparison [Table 3]
Kruskal-Wallis one-way ANOVA showed no statistically significant differences in dye leakage between all the restorative materials for occlusal margins (P = 0.464). However, there was statistically significant difference at gingival margins (P = 0.007).
Group 3 showed significantly less leakage than groups 1 and 2 at gingival margins (P = 0.007 and P = 0.040). Between groups 1 and 2, there was no significant difference (0.317).
Wilcoxon test (to compare occlusal and gingival scores of each material) revealed that the occlusal and gingival scores for each matched pair of restorative materials showed statistically significant differences (for Group 1, P < 0.001; Group 2, P < 0.001; Group 3, P < 0.006).
| Discussion|| |
Microleakage is an important property that has been used in assessing the success of any restorative material used in restoring a tooth. The current study examined the microleakage of different types of glass ionomer restorations placed in Class V cavities using a dye penetration test.
Cervical lesions due to caries, erosion, or abrasion present a special challenge to any restorative dentist because in such cavities, the restorative material is usually required to adhere to different types of tooth tissues. The coronal margins of cervical restorations are usually in enamel, while the cervical margins are in dentin or cementum. 
GIC undergo a complex acid-base setting reaction in which polyacrylic acid attacks aluminosilicate glass particles. Calcium and aluminium ions released from the glass initiate gelation and hardening of the cement. When the glass ionomer is applied to enamel or dentin, polyacrylic acid forms complexes with the calcium ions on the tooth surface, resulting in a chemical interaction between the substrate and cement. 
RMGI contains the components similar to conventional glass ionomer, but in addition, it also contains polymerizable resin monomers in liquid (HEMA) along with initiators and activators. When the powder and liquid are mixed, both the acid-base reaction of conventional glass ionomer and the polymerization reaction of resin components take place resulting in the formation of two separate matrices, i.e. metal polyacrylate matrix and poly HEMA matrix. 
Nano-filled RMGI is a new technical development that combines the benefits of a resin-modified light-cure glass ionomer and bonded nanofiller technology. Infrared (IR) analysis clearly demonstrates that nano-filled RMGI is a true RMGI material that undergoes both glass ionomer and free radical reactions similar to other RMGI.
There are several methods to detect microleakage. These include the use of dyes, chemical tracers, and radioactive tracers, scanning electron microscopy, neutron activation analysis, and fluid filtration. 
In this study, the dye leakage method was used because it is a simple, inexpensive, fast technique and does not require the use of complex laboratory equipments.  Dye leakage studies are amongst the most frequently used methods for detecting microleakage.  Several dye penetration studies have been performed using methylene blue, India ink, basic fuschin, crystal violet, as well as fluorescin.  Rhodamine-B dye was used in this study since its molecular size is as low as 1 nm which is smaller than the diameter of a dentinal tubule and can thus penetrate through even the smallest of gaps between the restoration tooth interfaces. , It is an organic dye compounded by a red-violet powder, classified as a xanthene dye,  and presents greater diffusion on human dentin than methylene blue. 
The validity of dye leakage studies has been questioned because of the possible effect of entrapped air on ingress of dye solution.  Spanberg et al.  and Goldman et al.  have reported that entrapped air can inhibit the penetration of dye into the gap between filling materials and dentinal walls when utilizing passive dye penetration.
In the present study, dye penetration under vacuum was used because vacuum pressure decreases the volume of entrapped air and allows complete dye penetration. ,
In this study, thermocycling was done because it is a widely used method in dental research to simulate temperature changes that take place in the oral environment. 
The results obtained in this study showed that all the three restorative materials that were investigated exhibited more microleakage on the gingival margins than on the occlusal margins. However, no material was able to completely eliminate microleakage at the enamel, dentin, or cementum margin. This finding is in agreement with other studies which concluded that cavity preparations with enamel margin result in consistently stronger bonds. Unique challenges are encountered with dentin surface bonding due to enamel that is 92% inorganic hydroxyapatite and dentin that is 45% inorganic by volume. ,
In this study, there was no statistically significant difference in the microleakage of groups 1 and 2 at both occlusal and gingival margins. This finding is in accordance with previous studies. , However, few studies have shown that there is statistically significant difference in microleakage of these materials. , This could be due to difference in experimental designs and testing methods used in these studies.
The groups 1 and 2 in this study showed high levels of dye penetration in gingival margins. It extended to full depth of the cavity and also on to the axial wall. Similar finding was seen in previous study, but dye penetrated to a lesser extent.  Vacuum used in this study could be the reason for the difference in severity of dye penetration in the present and previous study, as it eliminates the entrapped air that may inhibit dye penetration.
Nano-filled RMGI showed less leakage than CGIC and RMGIC at gingival margins. This may be due to the higher filler loading in the nano-filled type that may result in lower polymerization shrinkage and lower coefficient of thermal expansion, thus improving the long-term bonding to tooth structure.
Abd El Halim  reported that higher magnification of the bond interface of nano-filled RMGI showed an indistinct interface between the margin of the tooth structure and the restoration, suggesting that a chemical bond had formed between the GIC and tooth.
The higher leakage produced by the CGIC and RMGIC may be due to the fact that no primer was used with these type of glass ionomers, while nano-filled RMGI gets the benefit of using primer that is acidic in nature. The function of primer is to modify the smear layer and adequately wet the tooth surface to facilitate adhesion of the material to the hard tissue.
| Conclusions|| |
Within the limitations of this study, it is concluded that none of the three GIC were free from microleakage. The degree of microleakage in the gingival margins of each group was more than that in the occlusal margins. There were no statistically significant differences between all the restorative materials at occlusal margins. Nano-filled RMGI showed less leakage than CGIC and RMGIC at gingival margins. Therefore, nano-filled RMGI is a better restorative material for restoring cavities with gingival margins. The non-rinsing approach and specific delivery device favors the ease of use and reduces the technique sensitivity. Apart from the user friendliness, the major innovation of this material involves the incorporation of nanotechnology.
The occlusal stress generated in the cervical region during normal function and parafunction may increase microleakage or deteriorate the margins of Class V restorations.  Hence, studies have to be performed using nano-filled RMGI to evaluate the microleakage under occlusal loading.
| Acknowledgments|| |
The authors would like to thank Dr. Srinivas Reddy, HOD, Department of Pharmaceutics, and Dr. Raghu, Professor and Head, Department of Oral Pathology for their valuable support.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]