Journal of Conservative Dentistry

GYNAECOLOGY AND OBSTETRICS IMAGING
Year
: 2005  |  Volume : 8  |  Issue : 2  |  Page : 15--23

A spectrophotometric evaluation of effectiveness of surface protection for resin modified glass ionomer cement an in vitro study


Vishwas M Sangappa, NM Dhanya Kumar, Vasundhara Shivanna 
 College of Dental Sciences, Davangere, India

Correspondence Address:
Vishwas M Sangappa
College of Dental Sciences, Davangere
India

Abstract

Water plays an important role in the setting reaction and cement structure of glass ionomer cement. Both hydration and dehydration compromises the integrity of the material. Antonucci (1988) and Mithra (1989) developed resin modified glass ionomer cements (RMGIC). These were developed to overcome the problems of low initial mechanical strength and moisture sensitivity associated with conventional glass ionomer cements while preserving their clinical advantages. Investigations oil these materials have shown that addition of resin has not significantly reduced the susceptibility of glass ionomer materials to hydration and dehydration problems. Surface protection soon after the restoration is placed in the oral cavity preserved the water balance in the system and also filled small surface voids and defects preserving the restoration color by reducing the uptake of stains. This study was to spectrophotometrically evaluate the best surface protectant for RMGIC among Nail varnish, Fuji varnish, Fuji coat LC and Helio bond.



How to cite this article:
Sangappa VM, Dhanya Kumar N M, Shivanna V. A spectrophotometric evaluation of effectiveness of surface protection for resin modified glass ionomer cement an in vitro study.J Conserv Dent 2005;8:15-23


How to cite this URL:
Sangappa VM, Dhanya Kumar N M, Shivanna V. A spectrophotometric evaluation of effectiveness of surface protection for resin modified glass ionomer cement an in vitro study. J Conserv Dent [serial online] 2005 [cited 2022 Aug 12 ];8:15-23
Available from: https://www.jcd.org.in/text.asp?2005/8/2/15/42600


Full Text

 Introduction



Wilson and Kent introduced Glass ionomer cements in 1972. [1] their development arose from research into silicate and polycarboxylate cements. This material has unique properties, such as chemical adhesion to moist tooth structure, anticariogenic due to fluoride release and biocompatibility. [1] This tooth colored esthetic restorative material is becoming increasingly popular in recent years.

Water plays an important role in the setting reaction and cement structure of glass ionomer cement. Water lost during the early setting reaction, may stop the reaction resulting in surface crazing. [5] Water sorption on the other hand will lead the cement to loose its translucency. [5]

In essence, glass ionomer cements form a class of materials known as acid-base reaction cements. Initial setting occurs in 3-4 minutes, but precipitation, gelation and hydration occurs for atleast 24 hours and setting continues slowly for much longer periods. [1] These materials set and harden by a transfer of metal ions from the glass to the polyacrylic acid to form a salt hydrogel which is the binding matrix. [1] Water is the reaction medium and also serves and hydrate the silicious hydrogel and the metal polyalkeonate that are formed. It is an essential part of the cement structure. Therefore the water balance must be controlled to permit sufficient maturation of the glass ionomer cement before the restoration is exposed to the oral environment. Some form of surface protection during the early phases of setting reaction is essential for the development of optimum physical properties. [1]

If the setting cement is exposed to an aqueous environment too soon, after placement the setting process may be upset. Only after 1 hour the glass ionomer set cement is sufficiently resistant to hydration and dehydration to allow its exposure to oral environment with the setting reaction continuing upto 24 hours. [8] Correlations between early -exposure to water and reduced mechanical properties that lead to poor clinical performance have been demonstrated. [3] Lower compressive strengths and reduced degrees of hydration of the set matrix have also been reported. [3] On the other hand if left exposed to air after the initial setting, the glass ionomer cement will loose water rapidly leading to shrinkage and crazing. This will leave the restoration surface susceptible to staining and place heavy stresses on the newly formed ionic bonds, thus possibly leading to a loss of adhesion. [9] Restoration of glass ionomer cement should be covered with a waterproof protectant like varnish to protect them from hydration and dehydration for the first one hour. [11]

Antonucci (1988) and Mithra (1989) developed hybrid version of glass ionomer cement by incorporating HEMA which were called the Resin modified glass ionomer cements. [2] These were developed to overcome the problems of low initial mechanical strength and moisture sensitivity associated with conventional glass ionomer cements, while preserving their clinical advantages (ionic­adhesion to dental tissues and fluoride release). Although it's supposed that the occurrence of photochemical reaction and the presence of a resin network reduces the diffusion of water into the cement. Studies have shown that there is a detriment in the esthetic properties and failure at the tooth restoration interface of the resin modified glass ionomer cements due to dehydration and imbition respectively [7] . Investigations on these materials have shown that addition of resin has not significantly reduced the susceptibility of glass ionomer materials to hydration and dehydration problems, which lead to detriment in the esthetic properties and failure at the tooth-restoration interface [12] . But the application of surface protection soon after the restoration is placed in the oral cavity preserved the water balance in the system and also filled small surface voids and defects preserving the restoration color by reducing the uptake of stains [5] .

The purpose of this study was to evaluate the effectiveness of surface protectants such as nail varnish, Fuji varnish, Heliobond (light activated bonding resin) and Fuji Coat LC for a resin modified glass ionomer cement - Fuji II LC with the help of absorbance spectrophotometer.

AIMS AND OBJECTIVES

To evaluate the effectiveness of surface protectants applied on restorative resin modified glass ionomer cements immediately after setting in maintaining the water balance.

METHODS

The present in-vitro study was carried out in the Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere.

METHOD:

The resin modified glass ionomer cement used in the study is Fuji II LC. The four surface protectants compared are;

Nail varnishGC Fuji VarnishHeliobond - Light activated bonding resinGC Fuji coat LC

Positive control : No surface protectant is applied. Specimens are immersed in Methylene blue for 24 hrs.

Negative control No surface protectant is applied. Specimens are immersed in de-.ionized water for 24 hrs.

The cement - Fuji II LC is manipulated according to the manufacturers instructions and placed into the acrylic rings of 3 mm inside diameter and 2 mm height. The specimens are held between 2 glass slides separated by Mylar strips, and pressed with a weight of 500 Gms for 30 seconds and light cured for 30 seconds each on both exposed sides of the ring.

Then the excess of cement is trimmed off and the test specimens are protected with one of the surface treatments except for the positive and negative control groups, on both the exposed surface .

All the surface treatments are applied two coats on both the exposed surfaces with a brush. The light cured bonding resin and Fuji Coat LC are light cured according to the manufacturers directions. Nail varnish and Fuji varnish are allowed to dry for two minutes. After the surface treatment the specimens except for the negative control group specimens are immersed in 0.1% methylene blue solution at 37°C while the negative control group specimens are immersed in de-ionized water for 24 hours.

After 24 hours all 60 specimens are removed and rinsed with deionized water and the surface coatings are trimmed off with mediums of Sof Lex disc (3M) for 5 seconds. The specimens are now removed from the acrylic rings and immersed separately in 60 tubes each containing 1 ml of 65% Nitric acid for 24 hours. Standard solutions of methylene blue in I ml of nitric acid are prepared containing from 0 - 10 mg dye/ml based on absorbance of the Spectrophotometer (UV 160 IPC) at 606nm used in this study.

After 24 hours the standard and experimental solutions are diluted with 2 ml of de-ionized water. The solutions are filtered and centrifuged and the supernatant is used to determine the absorbance in a spectrophotometer at 606 nm. The method used to quantify the effectiveness of surface protection was adapted from that of Douglas and Zakariasen (1981). [13]

The effectiveness of surface protectants is recorded as mg dye per specimen, with lower values corresponding to better protection.

Dye penetration values are presented as Mean and standard deviation. One-way ANOVA was used for multiple groups comparison followed by Newmann-Keul's test for pairwise comparisons. P­-value of less than 0.05 was considered for statistical significance.

 Results & Observation



The present study was conducted to evaluate the effective surface protectant among Nail varnish, Fuji varnish, Fuji coat LC and Heliobond light cure bonding resin for Resin modified glass ionomer cement. (FujiliLC).

The effectiveness of the surface protectant applied to resin modified glass ionomer (Fuji II LC) was evaluated by a Spectrophotometric dye recovery method a volumetric analysis developed and utilized by Douglas W.H. and Zakariasen K.L. (1981) [13] in their study for determining the volume of apical leakage for obturated root canals. The study method has been found easy to utilize, is subject to minimal human measurement error and provides determination of volumes of leakage, rather than linear measurements.

The effectiveness of surface protectants was recorded as mg dye/specimen, with lower values corresponding to better protection.

Dye penetration values are presented as mean and standard deviation. One-way ANOVA was used for multiple group comparison followed by Newmann-Keul's test for Pairwise comparisons. P-Value of less than 0.05 was considered for statistical significance.

[INLINE:1]

 Discussion



The hypothesis verified on this work was that incorporation of resin into glass ionomer has not overcome the moisture susceptibility of glass ionomers and that Resin modified glass ionomer cement surface should be protected soon after initial set till the cement completely matures.

According to the results obtained, the Non­protected Resin-modified Glass ionomer cement specimens immersed in methylene blue (Positive control) presented a statistically significant higher dye uptake than other groups (P

The mean value for negative control group (0.00 ± 0.00) shows that there was no dye in the resin modified glass ionomer restorative tested (Fuji II LC). Consequently, the values of the experimental groups represent only the methylene blue that was taken up.

All the tested protective materials were not effective in completely preventing the uptake of dye. Furthermore Heliobond light cured bonding resin (Group 6) was comparatively a better surface agent for protecting resin modified glass ionomer cement from wafer imbalance.

The results are in accordance with Riberio G.P. et al (1999) [1] and Hotta M. (1992) [10]

The higher performance of Heliobond (P in this study can be probably explained by;

1) Its low viscosity, which means a low contact angle between the resin and the surface of the restorative material, leading to uniform distribution on to the restoration and resistance to disintegrate.

2) Interaction and the resin compatibility between the bonding resin and the resin components of the resin modified glass ionomer restorative evaluated leading to a chemical bond between them.

Among Group 3(Nail varnish), Group 4 (Fuji varnish), Group 5 (Fuji Coat LC).

Fuji varnish (Group 4) showed better protection with less dye penetration value, followed by Nail varnish (Group 3) and Fuji Coat LC (Group 5). But there was no statistically significant difference among their effectiveness as surface protectants.

When compared between Group 3 (Nail varnish) and Group 6 (Heliobond). The Nail varnish's poor performance over Heliobond was statistically significant, (p volatile solvent which became porus after the solvent evaporated.

This result is in accordance with Riberio G.P. and C. H. Sera et al - (1999). [1]

When compared between Group 4 (Fuji varnish) and Group 6 (Hello bond), the effectiveness of Heliobond was statistically significant (P Fuji varnish with low volatile solvent could not be better than Heliobond due to its inability to interact with the resin components of Resin modified glass ionomer to form a complete marginal seal, which may explain its poor performance.

These results were in accordance with previous studies by Shu-Fen Chang, Ying Tai J.N. et al (2001) [4]

When compared between Group 5 (Fuji coat LC) and Group 6 (Hello bond), the effectiveness of Heliobond was statistically significant (P poor performance of Fuji coat LC may be probably due to Fuji coat LC being a proprietary glaze, their chemistry varies and therefore their physical properties vary forming a high contact angle.

These results were in accordance with previous studies by Earl M.S.A. (1989) [6] and Riberio G.P. Ana et al (1999) [1]

The results of this study supports the working hypothesis that incorporation of resin into glass ionomer has not overcome the moisture susceptibility of Glass ionomers and that resin modified glass iondmer cement surface should be protected soon after its initial set till the cement completely matures.

THE SURFACE PROTECTANT SHOULD:

Be less volatile,Have low contact angleShould be able to bond with the chemical components of the resin in the Resin modified glass ionomer.Be able to seal the cement structure from external environment and allow the cement to completely mature.

The Heliobond light activated bonding resin on comparision provided better protection over the remaining protectants tested in this study.

However, additional in vivo and in vitro test and clinical trials are desirable in order to elucidate the effectiveness of this surface protectant.

 Conclusion



The present study concludes that:

1) Resin modified glass ionomer cement has not overcome the moisture susceptibility and its surface should be protected soon after its initial set till the cement completely matures.

2) Heliobond Light cured bonding resin is comparatively effective among Nail varnish, Fuji varnish, and Fuji coat LC in protecting the surface and there by preserving the water balance in resin modified glass ionomer cement.[Table 1],[Table 2]

References

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2 Alan D. Wilson. : Resin modified glass ionomer cements". International Journal of Prosthodontics. 1990; 3: 425-429.
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13W.H.Douglas,K.L.Zakariasen u.: Volumetric assessment of Apical leakage, utilizing a spectrophotometric dye recovery method. Journal of Dental Research. 1981;60:438 (Abst.512).