|Year : 2011 | Volume
| Issue : 2 | Page : 135-139
Comparative evaluation of the microleakage of two modified glass ionomer cements on primary molars. An in vivo study
Shaila Masih1, Abi Mathew Thomas1, George Koshy2, JL Joshi3
1 Departments of Pediatric and Preventive Dentistry, Christian Dental College, Ludhiana, Punjab, India
2 Departments of Oral and Maxillofacial Pathology, Christian Dental College, Ludhiana, Punjab, India
3 Joshi's Dental Clinic, E- Ground Floor, Sant Isher Singh Nagar, Pakhowal Road, Ludhiana, Punjab, India
|Date of Web Publication||9-Sep-2011|
Department of Pediatric and Preventive Dentistry, Christian Dental College, Ludhiana, Punjab
Source of Support: None, Conflict of Interest: None
| Abstract|| |
This in vivo study was conducted to compare and evaluate the microleakage of two modified glass ionomer cements on deciduous molars. Thirty children (10-16 years) were selected. In each patient, standardized class V cavities were prepared on the buccal surfaces of two different retained deciduous molars and these cavities were restored with GC Fuji II LC (Improved) and GC Fuji IX GP, respectively. Following a period of four weeks after the restoration, these teeth were extracted and immersed in 2% Basic Fuschin dye solution for 24 hours. The depth of dye penetration was assessed after sectioning the teeth and the microleakage determined. The results were statistically analyzed using Student 't' test. It was concluded that both the materials, GC Fuji II LC (Improved) and GC Fuji IX GP were comparable in performance and can be considered to be materials safe for Pedodontics usage, and decrease bacterial penetration.
Keywords: Glass ionomer cements, microleakage, sectioning
|How to cite this article:|
Masih S, Thomas AM, Koshy G, Joshi J L. Comparative evaluation of the microleakage of two modified glass ionomer cements on primary molars. An in vivo study. J Indian Soc Pedod Prev Dent 2011;29:135-9
|How to cite this URL:|
Masih S, Thomas AM, Koshy G, Joshi J L. Comparative evaluation of the microleakage of two modified glass ionomer cements on primary molars. An in vivo study. J Indian Soc Pedod Prev Dent [serial online] 2011 [cited 2019 Dec 14];29:135-9. Available from: http://www.jisppd.com/text.asp?2011/29/2/135/84686
| Introduction|| |
Restoring carious teeth is one of the major treatment needs in pediatric dentistry. The ideal requisites for a restorative material are that it should have good colour stability, biocompatibility, have a co-efficient of thermal expansion similar to that of natural tooth structure, excellent marginal seal and should have the ability to adhere chemically to both enamel and dentin.
Some of their physical and chemical properties make glass ionomer cements excellent dental restorative materials for pediatric patients. They provide a slow release of fluoride that produces a cariostatic action; chemically bind to enamel and dentin, thereby reducing the need for the retentive cavity preparation; and, are biocompatible with pulpal tissue. However, lack of strength, moisture sensitivity and poor esthetics in conventional glass ionomer cements have limited their use as a restorative material.
Due to the delayed setting reaction and low early strength, and other reasons such as poor aesthetics associated with the traditional glass ionomer cements, the technology of hybrid versions of the material which are light cured was introduced (Antonucci, McKinney and Stansbury). , These materials were classified as resin-modified glass-ionomer cements (RM GICs). The resin was incorporated in the glass ionomers to protect the chemical cure mechanism in the latter so that immediate finishing can be carried out. 
The longevity of a restoration is essentially because of a good marginal seal. Microleakage has been recognized as the major clinical problem with direct filling dental restorations. Microleakage may be the precursor of secondary caries, may promote tooth discoloration, staining of restorative margins, an adverse pulpal response, post operative sensitivity,
and even hasten the breakdown of certain filling materials.  Marginal leakage may occur because of dimensional change, changes in temperature and mechanical stress, or lack of adaptation of the restorative material resulting in a gap at the tooth/material junction.  These interfacial gaps will lead to microleakage, which can be defined as the "the clinically undetectable passage of bacteria, fluids, chemical substances molecules, ions at the restoration/tooth interface" (Kidd).  So a study of microleakage at the margins of a restoration would contribute to a better assessment of the material.
Most of the earlier microleakage investigations were done with carefully designed simulation of clinical circumstances (Morabito et al., Toledano et al.,). , However, these conditions vary considerably from those in the oral cavity. One such clinical condition of great importance is the outward flow of fluids from freshly cut dentin that may increase wetting of the dentin substrate and interfere with the development of adhesive bond to the tooth structure.
Another factor, which has been reported to influence the marginal integrity under clinical conditions, is the functional stresses caused by mastication.  In addition, adhesion of a restorative material to dentin can be compromised by a number of intraoral environmental conditions. These include the possibility of contamination by saliva or gingival fluids, and the technical difficulties associated with placement, contouring and finishing of the restoration. Recent literature reports few studies that have compared different glass ionomer cements in vivo. Due to the above mentioned reasons, this current study is designed in vivo with the aim to evaluate and compare the marginal sealing ability of the two glass ionomer cements, GC Fuji II LC (Improved) and GC Fuji IX GP, and also to find out which material will result in the least microleakage in primary molars, and to ascertain which of the two is a better restorative material for the primary dentition.
| Materials and Methods|| |
Thirty children (10-16 years old) with at least two sound non-carious primary molars were selected. Standardized class V cavities, approximately 4 mm wide x 2 mm high x 1.5 mm  deep were prepared on the buccal surfaces of non-carious primary molars with no mechanical retention,  using diamond burs (no. 1 round bur, No. 57 straight fissure bur, and No. 35 inverted cone bur). The depth of the cavity was standardized at 1.5 mm with the help of a premeasured and marked No. 57 straight fissure bur.
The prepared cavity was rinsed thoroughly with air/water spray and dried with oil-free compressed air. GC Dentin Conditioner was applied to the cavity walls using a brush with a light scrubbing motion for 20 seconds. The cavity preparation was rinsed thoroughly with water and then was dried. Out of the two teeth selected, one tooth was restored with GC Fuji II LC (Improved), and the other with GC Fuji IX GP. The glass ionomer cement, GC Fuji II LC (Improved), was inserted into the preparation and contoured, using a Teflon coated plastic filling instrument, after mixing in the ratio of 3:1 (powder: liquid) and cured for 20 seconds using the visible light cure unit, LA-500 blue light. After setting, the restoration was finished with finishing and polishing burs (Shofu Inc).
The glass ionomer cement, GC Fuji IX GP, was transferred to the preparation, using a Teflon coated plastic filling instrument. After setting, the restoration was finished and polished, keeping the restoration surface wet. After polishing, the restorations were lightly air-dried and the final surface coating of GC Coat LC was applied and light cured for 10 seconds. Following a period of four weeks after the restoration, these teeth were extracted. Both the restored teeth of each patient were extracted on the same day.
The extracted teeth were cleaned of soft tissue and debris, were washed under tap water and stored at room temperature in 1% Chloramine solution for 1 week  and then dried. All the tooth surfaces, except the restoration and a 1 mm zone adjacent to its margins, were covered with two coats of nail varnish. The root apices if any were sealed with sticky wax.
The coated teeth were immersed in a 2% aqueous solution of basic fuschin dye for 24 hours at room temperature. The specimens were retrieved. The wax was removed and the coatings were stripped from the teeth by peeling and scraping. The teeth were then thoroughly washed in water, dried, and were embedded in self-curing acrylic resin. The teeth were sectioned into two halves buccolingually in an apico-occlusal direction through the middle of the restoration by using a micromotor straight hand piece mounted with a rotating and water cooled diamond disc.
Each section thus prepared was inspected using a Light microscope (Motic-MC 2000 B1 series) with video output device (LG monitor with Windows XP supported hardware) to assess the dye penetration at the margins of the restoration. The microleakage was observed at a magnification of 10 X. A computer linked to the light microscope via a Motic MC camera was used to capture the images. Measurements were made in millimeters with the Motic Images Plus program version 2.0 ML for Windows. The degree of microleakage of both the halves of the sectioned teeth was examined. The section showing the maximum degree of dye penetration was chosen for grading the degree of microleakage. The extent of the microleakage was noted proportionate to the penetration of dye between the tooth structure and the restoration, separately for enamel, dentin and pulp, and scored using the scoring criteria  given below:
Score 0: No dye penetration.
Score 1: Dye penetration between the restoration and the tooth into enamel only.
Score 2: Dye penetration between the restoration and the tooth in enamel and dentin.
Score 3: Dye penetration between the restoration and the tooth in the pulp chamber.
The scores were tabulated, interpreted, and the resultant findings were statistically analyzed.
| Results|| |
[Table 1] shows the distribution of the samples used for the present in vivo study. A total of 60 deciduous teeth were divided into two groups of 30 teeth each for the study purpose. Student 't' test was undertaken to compare the mean scores of dye penetration of both the groups (Group I and Group II). The resin modified glass ionomer cement GC Fuji II LC (Improved) [Group I] showed higher value of mean score of dye penetration (1.33 ±0.84) than GC Fuji IX GP [Group II] (1.17±0.83). This result was statistically not significant (t = 0.75; P > 0.05). [Table 2] The mean extent of dye penetration was found to be more in GC Fuji II LC (Improved) (0.15±0.10) than that of GC Fuji IX GP (0.10±0.07). [Table 3] This result was statistically significant (t = 2.26; P < 0.05).
|Table 1: Distribution of the samples of the primary molars used for the in vivo study |
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|Table 2: Comparison of mean score of dye penetration in both groups, GC Fuji II LC (Improved) [Group I] and GC Fuji IX GP [Group II] in the study |
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|Table 3: Comparison of mean extent of dye penetration (mm) in both groups, GC Fuji II LC (Improved) [Group I] and GC Fuji IX GP [Group II] in the study |
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| Discussion|| |
Out of the 30 samples studied for microleakage using GC Fuji II LC (Improved), 7 samples showed no dye penetration (23.33%), 6 samples showed dye penetration in enamel (20.00%), and 17 samples showed dye penetration in enamel and dentin (56.67%). However, in this group none of the samples showed dye penetration in pulp. The extent of dye penetration was also calculated in millimeters. This gives more accuracy as to how much dye was found to penetrate in enamel or dentin or pulp. The GC Fuji II LC (Improved) showed more extent of dye penetration (p=0.0276) that was found to be statistically significant. The corresponding mean score of dye penetration was also found to be higher for this group though it was statistically non-significant (P=0.228).
GC Fuji II LC (Improved) exhibited greater microleakage at dentin margins than enamel margins. This finding is in accordance with previously reported in vitro studies of microleakage of glass ionomer restorations (Alperstein et al.,  ; Gordonet al.,  ). It exhibited more rapid setting through polymerization of the polymer component. The Fuji II framework is more rigid and less capable of elastic deformation at the initial stage of polymerization. Feilzer et al., and Bourke et al.,  have also shown that significant dimensional changes and surface hardening can occur after initial photo curing of the resin and further contraction also continues for the first 24 hours as the material matures. Hence, microleakage at dentinal margin is greater than at enamel margins for Fuji II LC (Improved).
The presence of a non-particulate layer of solid material within the body of GC Fuji II LC (Improved), adjacent to dentin termed as the 'absorption layer' develops over time and has been shown to be inherently weak (Watson, Sidhu and Griffiths,).  It does not appear adjacent to the enamel and is important in the maintenance of fit of the restoration. This again explains why there is more microleakage at dentinal margin for Fuji II LC (Improved).
The present study showed that resin modified glass ionomers showed more microleakage than conventional glass ionomers. These findings were in contrast with the findings of similar studies done by Leinfelder,  and Bobotis et al.,  which showed that light cured glass ionomer cements can reduce or even eliminate microleakage. The difference in results could be because the above mentioned studies were conducted in vitro in which oral conditions were not considered. This is very clear from the study conducted by Abdalla and Davidson,  in which the marginal integrity of class II composite restorations was compared in vivo and in vitro. The results clearly showed that the restorations placed in vivo showed microleakage that was significantly greater than that found in the equivalent restoration placed in vitro.
The clinical performance of these materials can be explained by the hydrophilic nature of GC Fuji IX GP. The presence of tubular fluid of vital dentin can reduce dehydration of glass ionomer materials during the setting period. It may also improve the hydrated gel phase during solidification and allow a self-repairing process.  According to the above theory, the glass ionomer forms internal microcracks as compensation for the shrinkage in order to maintain the bulk volume. After water sorption and consequent swelling, the cracks close and, due to the continuing chemical reaction, the partially lost cohesive strength is repaired. Thus, the important role of water for glass ionomers during this phase is in the maintenance of good dimensional stability. On the other hand, the in vivo performance of GC Fuji II LC can, besides the presence of hydrophilic groups, be related to the strong and reliable micromechanical bond of resin that has impregnated the demineralized surface dentin. However, the in vitro studies are mainly done in extracted teeth without the presence of an outward flow of dentinal fluid from the cut surface. This can alter the results from that of in vivo studies. In the present study, in spite of the favorable oral conditions for GC Fuji II LC (Improved) and GC Fuji IX GP, both showed microleakage.
The coefficient of thermal expansion of GC Fuji IX GP is similar to that of adjacent tooth structure, which could be a reason for less microleakage observed in GC Fuji IX GP as compared to GC Fuji II LC (Improved), the coefficient of thermal expansion being quite high as compared to tooth structure for the latter. As the temperature in the oral cavity decreases, a negative interfacial pressure is generated. This in turn encourages the ingress of oral fluids into the margins. Conversely, as the temperature increases, the interfacial temperature also increases. Consequently, the fluids are forced back to the surface. This phenomenon results in an increased degree of microleakage. As the difference in coefficient of thermal expansion between restorative material and tooth structure increases, so does the potential for microleakage. This is the possible explanation for more microleakage in GC Fuji II LC (Improved). Another reason for differences in microleakage observed between GC Fuji II LC (Improved) and GC Fuji IX GP might be due to differences in maturation of setting reaction.
Frankenberger et al.,  reported that GC Fuji IX GP sets faster and is of higher viscosity because of finer glass particles, anhydrous polyacrylic acids of high molecular weight and a high powder to liquid mixing ratio. These properties may be responsible for GC Fuji IX GP showing good marginal seal.
Another reason for less leakage in GC Fuji IX GP is because the contraction is initially a slow cross-linking reaction, and the material may absorb a substantial amount of water from the oral fluids, which contributes to the relaxation of stress developing in the final setting.
Conditioning transforms the smooth enamel into a very irregular surface, and also increases its surface free energy. When GC Fuji II LC (Improved) was applied to the irregular etched surface, the resin penetrates into the surface aided by capillary action. Monomers in the material polymerize and the material becomes interlocked with the enamel surface. The formation of resin microtags within the enamel surface is the fundamental mechanism of good adhesion of GC Fuji II LC (Improved) to enamel. However, in dentin, because of the capillary pressure and dentinal fluid oozing out of the tubules, the resin is unable to penetrate far. This could be a possible reason for GC Fuji II LC (Improved) showing more leakage in dentin.
The results clearly depicted that although both the materials, GC Fuji II LC (Improved) and GC Fuji IX GP, showed comparable microleakage, GC Fuji II LC (Improved) showed slightly more microleakage as compared to GC Fuji IX GP. On the other hand, considering that some samples showed no microleakage, the materials are actually capable of reducing bacterial penetration. Though GC Fuji II LC (Improved) has command over setting time and sets immediately, it was unable to prevent microleakage. Hence, further improvement is required for this material so that its marginal sealing ability is maintained till the time the restored primary tooth is present in the oral cavity. It can be concluded that both the materials are equally good for use in pediatric dentistry.
It was concluded that the marginal sealing ability of GC Fuji II LC (Improved) and GC Fuji IX GP was comparable based on the mean score and percentage score of dye penetration, but GC Fuji IX GP showed slightly better results, though the findings were statistically not significant. Both the restorative materials GC Fuji II LC (Improved) and GC Fuji IX GP exhibited some degree of microleakage. The comparison of mean extent of dye penetration showed that GC Fuji IX GP showed lesser microleakage than GC Fuji II LC (Improved), and the results were statistically significant. GC Fuji II LC (Improved) showed more microleakage in dentin as compared to GC Fuji IX GP. GC Fuji IX GP demonstrated more microleakage in enamel as compared to GC Fuji II LC (Improved). Both the materials, GC Fuji II LC (Improved) and GC Fuji IX GP were comparable in performance and can be considered to be materials safe for usage in Pedodontics, thereby decreasing bacterial penetration.
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[Table 1], [Table 2], [Table 3]
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