|Year : 2011 | Volume
| Issue : 1 | Page : 20-24
Nanoionomer: Evaluation of microleakage
S Upadhyay, A Rao
Department of Paedodontics and Preventive Dentistry, Manipal College of Dental Sciences, Manipal University, Mangalore, India
|Date of Web Publication||23-Apr-2011|
Professor & Head, Department of Paedodontics and Preventive Dentistry, Manipal College of Dental Sciences, Manipal University), Light House Hill Road, Mangalore - 575 001
| Abstract|| |
Background: Glass ionomer cements are widely used in pediatric practice due to their advantage of fluoride release and chemical bond to tooth structure. Adherence of the restorative material to the cavity walls is one of the most important characteristic for it to be proven as an ideal material as it prevents microleakage. Aims and Objectives: This study was aimed at evaluating the microleakage of nanofilled resin-modified glass ionomer cement compared with the conventional and resin-modified glass ionomer cements. Materials and Methods: Standard class V cavities of size 3 mm x 2 mm x 2 mm were made on a total of 30 extracted teeth and restored with the conventional glass ionomer, resin-modified glass ionomer or nanoionomer. After thermocycling, teeth were immersed in 0.5% methylene blue dye for 24 h. They were then sectioned buccolingually. Microleakage was assessed for the occlusal and gingival walls using a compound microscope by two examiners independently. Results: Nanoionomer demonstrated the least microleakage, with a mean score of 1.3, compared with the resin-modified glass ionomer (score of 3.2) and conventional glass ionomer cement (score 2.6). Conclusion: Nanoionomer exhibited adequate resistance to microleakage and thus may prove better than conventional or resin-modified glass ionomers.
Keywords: Glass ionomer, microleakage, nanoionomer
|How to cite this article:|
Upadhyay S, Rao A. Nanoionomer: Evaluation of microleakage. J Indian Soc Pedod Prev Dent 2011;29:20-4
| Introduction|| |
Adherence of the restorative material to the cavity walls is one of the most important characteristics for it to be proven as an ideal material because it prevents microleakage. Microleakage is defined as the chemically undetectable passage of bacteria, fluids, molecules or ions between the cavity walls and restorative materials.  This seepage can cause hypersensitivity of restored tooth, tooth discoloration, recurrent caries, pulpal injury and accelerated deterioration of the restorative material.
Traditional glass ionomer cement has been plagued by several negative characteristics, which include prolonged setting time that restricts finishing and polishing for approximately 24 h, sensitivity to moisture during initial hardening, dehydration, rough surface texture and opaqueness. These limitations have been overcome by the introduction of resin-modified glass ionomer cements. 
Development in the field of resin-modified glass ionomer cement has led to the introduction of nanoionomer, which combines the benefit of resin-modified glass ionomer cement together with nanofiller technology. Fillers used are fluoroaluminosilicate glass of size less than 3 micron (average 1 micron) and nanofillers (5-25 nm) and nanocluster fillers (1.0-1.6micron) derived from silica and zirconia. Unlike other glass ionomer cements, nanoionomer is a two-paste system that provides faster, easier, less messy and more reproducible dispensing and mixing. The primer ensures better adhesion of the cement to the tooth. 
This study was aimed at evaluating the microleakage of nanofilled resin-modified glass ionomer cement compared with the conventional and resin-modified glass ionomer cements.
| Materials and Methods|| |
Ethical committee clearance was obtained prior to the study from the Time Bound Research Ethics Committee, Kasturba Medical College, Mangalore, Karnataka.
A total of 30 noncarious premolars extracted for orthodontic purpose were selected for the study. Surface debridement of all the teeth was performed with a hand-scaling instrument and the teeth were stored in normal saline at room temperature till further use. The teeth were randomly divided into three groups of 10 teeth each as follows:
Group A: cavities filled with conventional glass ionomer cement
Group B: cavities filled with resin-modified glass ionomer cement
Group C: cavities filled with nanofilled resin-modified glass ionomer cement
The details of the materials investigated in this study are given in [Table 1].
A standard class V cavity of size 3 mm x 2 mm x 2 mm was prepared on the facial surface of each tooth with no mechanical retention, using carbide bur in a contraangle high-speed airotor handpiece with water coolant. Depth of the cavity was measured with a periodontal probe.
For group A, dentin conditioner (10% polyacrylic acid) was applied to the walls of the cavity for 15 s with a cotton pellet, rinsed with water for 30 s and blotted dry with tissue paper. The material was mixed and the cavity was restored as per the manufacturer's instruction. Excess material was removed and a coat of petroleum jelly was applied over the restoration.
For group B, the dentin was conditioned, rinsed and dried as above. Cement was mixed and restored according to the manufacturer's instruction. After removal of the excess, the material was light cured for 20 s.
For group C, primer was applied to the enamel and dentin for 15 s with a fiber tip, dried with an air syringe for 10 s and light cured for 10 s. An equal amount of two pastes was dispensed and mixed for 20 s. The cavity was restored and excess material removed and light cured for 20 s.
All the teeth were then subjected to thermocycling for 250 cycles at temperatures of 4ºC ± 2ºC, 37ºC ± 2ºC and 60ºC ± 2ºC with a dwell time of 30 s in a controlled water bath.
The apices of all the teeth were sealed with acrylic resin. Each tooth was covered with two coats of nail varnish except for an area approximately 2 mm from the periphery of the restoration. All the teeth were immersed in 0.5% methylene blue dye for 24 h. After removal from the dye solution, the teeth were allowed to dry. They were then sectioned buccolingually through the center of the restoration using a carborundum disk.
The specimens were then studied under a compound microscope with a magnification of 40X to measure the depth of the dye penetration on the occlusal and gingival walls of both halves of the teeth.
The scoring was done as described by Khera and Chan  [Figure 1]and [Figure 2] as follows:
|Figure 1: Diagrammatic representation of the cavity showing walls and scoring|
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|Figure 2: Microleakage score under the microscope. (a) score 0, (b) score 1, (c) score 2, (d) score 3, (e) score 4|
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0 = No leakage
1 = Less than and up to one-half of the depth of the cavity preparation penetrated by the dye
2 = More than one-half of the depth of the cavity preparation penetrated by the dye but not up to the junction of the axial and occlusal or gingival wall
3 = Dye penetration up to the junction of the axial and occlusal or gingival wall but not including the axial wall
4 = Dye penetration including the axial wall
Scoring for microleakage was carried out independently by two examiners in order to eliminate bias. The scoring was performed independently by two examiners. Data analysis was done using ANOVA, with SPSS package 11.0.
| Results|| |
Measurement of agreement with the Kappa test was found to be "outstanding" (0.933) between the two examiners.  The microleakage scores are given in [Table 2]. The difference in microleakage score between occlusal and gingival wall was not significant. Thus, the wall with maximum scores was considered for the study. The mean score for group A was 2.6, group B was 3.2 and 1.3 for group C.
Within group A, the microleakage score ranged between 0 and 4, both occlusally and gingivally, for three materials.
For group B, none of the sample showed 0 microleakage. Occlusally, five samples showed maximum microleakage with scores of 4 whereas five sample showed minimal microleakage of score 1, gingivally.
Microleakage scores in group C did not exceed score 2. Nine samples exhibited score 1 in the occlusal wall and seven samples in the gingival wall.
Intergroup comparison showed that there was a significant difference in microleakage between group A and group C (P = 0.027) and between group B and group C (P = 0.001), but no significant difference between group A and group B (P = 0.423) [Table 3].
| Discussion|| |
Microleakage is used as a measure to evaluate the performance of the restorative materials. This in vitro study was carried out to evaluate and compare the microleakage of a new material, nanofilled resin-modified glass ionomer cement, with conventional and resin-modified glass ionomer cements.
After restoration of the cavities, all the teeth were subjected to thermocycling to simulate the oral environment as to the extremes of temperature. Methylene blue dye was used to assess the microleakage as this was the simplest and fastest method. Comparison of leakage at the occlusal and gingival margins revealed no significant difference. A similar result has also been reported previously by Puckett et al. 
The result demonstrates that none of the three glass ionomer cements was free from microleakage. But, the nanofilled resin-modified glass ionomer cements showed the least microleakage, with a mean score of 1.3. Gorseta et al. observed that nanoionomer showed lower microleakage values compared with the conventional glass ionomer cements, and emphasized the efficacy of nanoionomer cements to be used in routine dental practice. Wadenya et al. recommended the use of nanoionomer cements in the atraumatic restorative technique as there was no significant difference between its use as Atraumatic Restorative Technique and as conventional technique.
The microleakage was maximum in the resin-modified glass ionomer cement compared with others, with a mean score of 3.2. Puckett et al. found that the degree of microleakage of the conventional glass ionomer cement was less that that of the resin-modified cements. But, Brackett and Gunny,  on the contrary, found that the resin-modified glass ionomer cement sealed the cavity adequately. Crim,  when comparing the light-cured glass ionomer and conventional glass ionomer, found no microleakage for both the materials.
| Conclusion|| |
None of the three glass ionomer cements was free from microleakage.
Nanofilled resin-modified glass ionomer cement demonstrated the least microleakage and proved to be better than the conventional and resin-modified glass ionomer cements.
This study suggests better efficacy of the nanofilled resin-modified glass ionomer cements in terms of cavity sealing.
| References|| |
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]