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Table of Contents
ORIGINAL ARTICLE
Year : 2016  |  Volume : 6  |  Issue : 3  |  Page : 110-115

Comparative evaluation of microleakage using three variables of glass-ionomer cement in primary and permanent teeth: An in vitro study


1 Department of Pedodontics and Preventive Dentistry, Sibar Institute of Dental Sciences, Guntur, AndhraPradesh, India
2 Department of Pedodontics and Preventive Dentistry, SVS Institute of Dental Sciences, Mahbubnagar, Telangana, India
3 Department of Orthodontics, Sibar Institute of Dental Sciences, Guntur, AndhraPradesh, India

Date of Web Publication7-Mar-2017

Correspondence Address:
A J Sai Sankar
Department of Pedodontics and Preventive Dentistry, Sibar Institute of Dental Sciences, Guntur, AndhraPradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2229-5194.201646

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   Abstract 

Background and Objective: Since their invention in 1970, glass-ionomer cements (GICs) have been widely used in pediatric dentistry. They have undergone many modifications in composition till the recent nano cement which claims to have superior properties compared to their primal versions. One of the important requisites of restorative material is adhesion to the tooth structure, failure of which leads to microleakage. Hence, the main objective of this study was to compare the microleakage of three variables (Ketac Molar, Ketac Silver, Ketac N100) of GIC in primary and permanent posterior teeth. Materials and Methods: Class I occlusal cavities were prepared on 60 extracted, noncarious primary molars and premolars. Each set of dentition (primary and permanent teeth) was divided into three groups of 10 specimens each to restore with the selected restorative material - Group A (Ketac Molar), Group B (Ketac Silver), and Group C (Ketac N100). These teeth were subjected to thermocycling, dye immersion, sectioning, and examination was done under a stereomicroscope to assess the degree of microleakage. The scoring was done according to the scoring criteria put forward by Khera and Chan, which were further tabulated and statistically analyzed. Results: There was no significant difference in microleakage between primary and permanent teeth in all the three groups. In both primary and permanent teeth, Group B showed significantly higher dye penetration scores followed by Groups A and C. Conclusion: The nano-filled resin-modified GIC (Ketac N100) proved to be the better restorative material than the other cements used in the study.
Clinical Relevance To Interdisciplinary Dentistry
Microleakage is the most common cause of failure for all restorative materials, since it is a major contributing factor to secondary caries and early pulpal involvement. Consequently, an interest arises in finding a restorative material which has better bonding with the dental tissues thereby minimizing the chances of microleakage. Nano-filled RMGIC is found to be a good restorative material in maintaining the longevity of the restoration both in primary and permanent dentition.

Keywords: Dye penetration, microleakage, nano-filled resin-modified glass-ionomer cement


How to cite this article:
Nandana K L, Sai Sankar A J, Manoj Kumar M G, Naveen K, Pranitha K, Manjula B S. Comparative evaluation of microleakage using three variables of glass-ionomer cement in primary and permanent teeth: An in vitro study. J Interdiscip Dentistry 2016;6:110-5

How to cite this URL:
Nandana K L, Sai Sankar A J, Manoj Kumar M G, Naveen K, Pranitha K, Manjula B S. Comparative evaluation of microleakage using three variables of glass-ionomer cement in primary and permanent teeth: An in vitro study. J Interdiscip Dentistry [serial online] 2016 [cited 2019 Dec 8];6:110-5. Available from: http://www.jidonline.com/text.asp?2016/6/3/110/201646


   Introduction Top


The art of restorative dentistry has undergone lots of progression with the advent of nanosciences. Technology has modified esthetic restorations such as glass-ionomer cement (GIC), composites according to the need, to a near perfect level. GIC is being used in pediatric dentistry through the ages for both primary and permanent dentition since its introduction to dentistry in 1970 by Wilson and Kent [1] with the goal of combining the advantages of silicate and polycarboxylate cements. However, difficulty with manipulation and poor mechanical properties compared with other materials jeopardized their initial success. The advantages of GICs such as chemical bonding to tooth structure and lower microleakage compared with resins prompted researchers to continue working for the further improvement of this material.[2]In the 1980s, with the goal of creating stronger and more durable glass-ionomer materials, one manufacturer added silver amalgam powder to the glass powder. Another combined the glass powder with elemental silver (cermet) by a process of high heat fusion (sintering).[3] Even though the wear resistance was improved, fracture resistance, fracture toughness, and esthetics of the metal-modified materials are still too low. Despite its disadvantages, this material did establish a modest niche for itself in pediatric dentistry as a substitute to silver amalgam in certain cases.[2],[3]

The physical properties of traditional GICs have improved dramatically with the introduction of high powder-to-liquid ratio, which enables rapid setting of the material, thereby significantly reducing early moisture sensitivity. The faster hardening of the material has been achieved by altering the particle size and particle size distribution of the glass powder, thus providing a denser material which gives a “condensable” feel, facilitating its use in posterior teeth.[3],[4]

Later, light cure GICs were well recognized, the most obvious one being the cure-on-demand feature. Nanotechnology is used in further development of these materials to provide additional benefits of improved esthetics, high wear resistance, and super polish. In general, GICs contain a broad range of filler particles, the size of which can influence strength, optical properties, and abrasion resistance. By using bonded nanofillers and nanocluster fillers along with fluoroaluminosilicate glass, these materials have been improved and introduced as nano-filled resin-modified GICs (RMGICs).[5]

One of the important requisites of good restorative cement is adhesion to tooth structure, failure of which leads to microleakage. Microleakage is defined as “the leakage of microorganisms and toxins between the restoration and walls of cavity preparation.” In the clinical situation, this may lead to marginal breakdown, postoperative hypersensitivity, recurrent caries, which are considered as major problems in restorative dentistry.[6]

The purpose of this study was to assess and compare the microleakage of three variables of GICs – conventional (Ketac Molar), metal reinforced (Ketac Silver), and nano-filled RMGIC (Ketac N100) by restoring extracted primary molars and premolars in laboratory conditions.


   Materials and Methods Top


Of the total 60 teeth, 30 noncarious retained primary molars and 30 premolars extracted for orthodontic reasons were selected for this study. After mechanical debridement, the teeth were cleaned with pumice water slurry and stored in normal saline until further use. Class I cavities standardized to a size of 3 mm × 2 mm × 2 mm dimensions were prepared in all specimens with ISO #010 straight fissured diamond bur. Dimensions of the cavity were measured using a William's graduated periodontal probe to maintain uniformity. Each set of dentition (primary and permanent) was divided into three groups of 10 specimens each to restore with the selected restorative material - Group A (Ketac Molar), Group B (Ketac Silver), and Group C (Ketac N100) [Table 1].
Table 1: The details of the materials investigated in the study

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Specimens of Groups A and B were conditioned with 10% polyacrylic acid for 10 s, rinsed with water, air-dried, and restored with the respective cements according to the manufacturer's guidelines, whereas in Group C, the specimens were coated with primer, air-dried for 10 s, and light cured for 10 s. The aqueous (acidic polyalkenoic acid, reactive resins, and nanofillers) and nonaqueous pastes (fluoroaluminosilicate glass, reactive resins, and nanofillers) were mixed (according to manufacturer's guidelines) and the mixture was placed into the cavity following two-step incremental techniques, where the first small increment was placed in the most inaccessible area of the preparation, and subsequent additions were made and light cured for 30 s each. All the restored teeth were stored in normal saline till further use to prevent dehydration.

To simulate the oral environment, the test specimens were subjected to thermocycling at temperatures of 5°C ± 1°C and 55°C ± 1°C with a dwell time of 30 s. This procedure was alternatively repeated for 100 times.

Following thermocycling procedure, the test specimens were coated with two layers of varnish except for 1 mm around the restoration and root apices were sealed with sticky wax and immersed in 2% methylene blue dye for 24 h. Later, the samples were rinsed under tap water and sectioned buccolingually with the help of a safe-sided diamond disk [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d,[Figure 1]e.
Figure 1: (a) Materials used in the study, (b) Teeth samples of the three groups, (c) Thermostatically controlled water bath, (d) Teeth immersed in Methylene Blue dye, (e) Tooth sectioning

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The specimens thus obtained were observed under stereomicroscope, and photomicrographs were taken at ×20 magnification. The degree of microleakage was evaluated by the dye penetration from the occlusal margin to the base of the cavity on the photomicrographs using the evaluation criteria put forward by Khera and Chan [7] [Figure 2]. The values thus obtained were tabulated and statistically analyzed using Mann–Whitney U-test and Kruskal–Wallis ANOVA test.
Figure 2: Stereomicroscope and photomicrographs at ×20

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   Results Top


There was no significant difference in microleakage between primary teeth and permanent teeth in all the groups (A, B, C) [Table 2]. However, significant difference among the three groups in primary teeth was noticed (H = 12. 2647, P < 0.05) at the 5% level of significance, with higher dye penetration scores in Group B (3.00 ± 0.0000) as compared to Group A (2.40 ± 0.5164) and Group C (1.50 ± 1.1785). Similarly, the three groups in permanent teeth showed statistically significant differences in the dye penetration scores (H = 22. 3152, P < 0.05) with higher dye penetration scores in Group B (2.90 ± 0.3162) followed by Group A (2.20 ± 0.4216) and Group C (1.10 ± 0.5676), respectively [Graph 1].
Table 2: Comparison of microleakage of three groups (A, B, C) in primary teeth and permanent teeth by Mann-Whitney U-test

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As H-test showed significant difference among the three groups (A, B, C), the Mann–Whitney U-test was applied to know the pair-wise differences between the groups.

In primary teeth, there was statistically significant difference in microleakage scores between Groups A and B (Z = −2.2678, P < 0.05) at the 5% level of significance, with higher microleakage in Group B, whereas Group A and C did not show significant differences (Z = −1.7386, P > 0.05). Groups B and C also showed significant difference in microleakage (Z = −2.6458, P < 0.05) with higher microleakage in Group B [Table 3].
Table 3: Pair-wise comparison of microleakage of three groups (A, B, C) in primary teeth by Mann-Whitney U-test

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In permanent teeth, Groups A and B exhibited statistically significant difference (Z = −2.6458, P < 0.05) with higher microleakage in Group B, whereas between Groups A and C, significantly higher microleakage seen in Group A compared to Group C (Z = −3.1749, P < 0.05). Groups B and C also showed significant difference (Z = −3.7041, P < 0.05) with higher microleakage in Group B (2.90 ± 0.3162) compared to Group C (1.10 ± 0.5676) [Table 4].
Table 4: Pair-wise comparison of microleakage of three groups (A, B, C) in permanent teeth by Mann-Whitney U-test

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   Discussion Top


There is a continuous search for the restorative material and technique that will provide optimal adhesion to tooth structure to minimize microleakage as well as have excellent mechanical and physical properties. Different microleakage test methods have been used for years to predict the performance of restorative materials at the tooth-restoration interface.[8]

The present in vitro study utilized the dye penetration technique to study the microleakage using conventional GIC (Ketac Molar), metal-modified GIC (Ketac Silver), and nano-filled RMGIC (Ketac N100) with recommended dentin pretreatments in primary and permanent teeth. Microleakage can be assessed by various methods such as radioisotopes, dyes, air pressure, neutron activation analysis, pH changes, and scanning electron microscopy; however, dyes and radioisotopes are most commonly used. In the present study, 2% methylene blue dye was selected as a measure of microleakage because of its low cost, ease of manipulation, convenience, and also the low molecular weight of the dye is smaller than bacteria that could detect leakage where bacteria could not penetrate.[9],[10]

Thermocycling is a method widely used in dental research, particularly while testing the performance of adhesive materials in conditions which mimic intraoral temperature variations by subjecting the restorations to temperature extremes comparable with the oral cavity.[11] Degree of dye penetration is not influenced by number of thermal cycles.[12] Therefore, in the present study, the samples were subjected to 100 cycles with a dwell time of 30 s.

For the total sample, Class I cavities were prepared as they were easy to standardize. Research showed that the smear layer on the prepared cavity walls can affect the bond between GIC and dentin. If the smear layer is not removed, it can act as a weak point leading to cohesive failure during polymerization shrinkage and episodes of thermal expansion and contraction.[13] Several researchers reported improved bond strength when the smear layer was removed using polyacrylic acid before the use of RMGIC.[14],[15] Regardless of the agent used, it must be remembered that GICs form a chelation bond to dentin and enamel and the elimination of the smear layer improves the bonding of the cement to the actual tooth structure.

In the present study, no statistically significant differences in microleakage scores were noticed between primary and permanent teeth in all the three tested materials. Studies by Schmitt and Lee [16] and Pair et al.[17] have also found similar results. The mean values of the three materials are different and comparable. This can be attributed to the enamel structure of primary and permanent teeth. The fact that there is a prismless layer of enamel in primary teeth which interferes with the bonding of restorative materials occupies high significance over here. Other reasons such as enamel thickness in permanent teeth and dentin being softer in primary teeth also seem to influence the bonding, which inadvertently increases the microleakage of primary teeth.[18]

In primary teeth, all the groups showed statistically significant difference with respect to the degree of microleakage, with high score in Group B. Studies by Fuks et al.[19] and Kilpatrick et al.[20] also observed greater microleakage in Ketac Silver whereas Stratmann et al.[21] found that silver-reinforced glass ionomer is a good material in restoring primary teeth contradicting the results of the present study.

Microleakage scores were slightly more in Group A than Group C samples in the current study. This could be attributed to the fact that materials with a coefficient of thermal expansion significantly different than that of the teeth generate a negative interfacial pressure at reduced temperatures which promotes ingress of fluids.[22] Similar results were found by Abo-Hamar et al. in a 2-year clinical trail.[23]

In relation to permanent teeth, all the three groups showed statistically significant difference with respect to microleakage scores. The values were significantly higher in Group B compared to Group A. Study by Welsh and Hembree, Wadenya and Mante found that conventional GIC showed less microleakage than other materials.[24],[25]

Group B specimens showed significant microleakage when compared to the specimens of Group C which is in concord with study conducted by Robbins and Cooley.[26]

Results of the present study revealed that both primary and permanent teeth showed maximum microleakage when restored with Ketac Silver, with mean values of 3.0 and 2.9, respectively. This can be due to the interference of metal (silver) particles with the adhesion of material to the tooth structure. On the other hand, Ketac N100 showed less microleakage in both the dentition with mean value of 1.5 and 1.1, respectively, than Ketac Molar (2.4 and 2.2) and Ketac Silver (3.0 and 2.9). This can be attributed to the bonded nanofillers and nanoclusters which have better bonding properties and smaller filler size that are added to the newer material (Ketac N100).[27]

Abd El Halim and Zaki compared the microleakage of three GICs and found that nano-filled RMGIC showed the lowest microleakage scores. The nanostructure of the nano-filled glass-ionomer type allowed for excellent wetting and adaptability to the tooth surface, hence enhancing the chemical bonding. The higher filler loading in the nano-filled type may result in lower polymerization shrinkage and lower coefficient of thermal expansion of this type of glass ionomer, improving the long-term bonding to tooth structure.[28]

Falsafi et al. had done a material study and concluded that nano-filled RMGIC showed two setting reactions expected in true RMGIC. The adhesion with dentin and enamel was similar to other glass ionomers, and the formation of calcium-polycarboxylate was also evident. This chemical bonding is a significant factor in the excellent long-term adhesion of these materials.[29] In nano-filled RMGIC, aggregated “nanoclusters” are in the 1-µm size range but are composed of 5–20 nm spherical particles that have been lightly sintered together to form a porous structure interpenetrated with the resin monomers. As the surface of the “nanocluster”/resin combination is subjected to stress and abrasion, the smaller nano-sized particles, which make up the clusters, tend to break apart rather than the entire particle being plucked from the resin matrix. Thus, Ketac N100 is about three times more resistant to biomechanical degradation than other materials.[30]

The results of this study clearly show that the nano-filled RMGIC (Ketac N100) has better physical properties than other glass ionomers, and these nano-filled GICs can be reckoned as restorative materials of the future generation; however, these results have to be substantiated with further long-term in vivo studies and large sample.


   Conclusion Top


The following conclusions were drawn from this study:

  • None of the tested GICs was free from microleakage and no significant difference in microleakage was observed between primary and permanent teeth with respect to all the tested materials
  • Cavities filled with metal-reinforced GIC (Ketac Silver) showed maximum microleakage than conventional GIC (Ketac Molar) and nano-filled RMGIC (Ketac N100)
  • Cavities filled with Ketac N100 had significantly less leakage showing that composition of the material has a definite effect on the degree of microleakage.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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