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ORIGINAL ARTICLE
Year : 2013  |  Volume : 31  |  Issue : 4  |  Page : 229-233
 

Surface coatings on glass ionomer restorations in Pediatric dentistry-Worthy or not?


1 Department of Pedodontics and Preventive Dentistry, Narayana Dental College, Nellore, India
2 Department of Pedodontics and Preventive Dentistry, Government Dental College and Hospital, Afzulgunj, Hyderabad, Andhra Pradesh, India

Date of Web Publication21-Nov-2013

Correspondence Address:
Rekhalakshmi Kamatham
Assistant Professor, Department of Pedodontics and Preventive Dentistry, Narayana Dental College, Nellore, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-4388.121818

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   Abstract 

Background: To know the effect of surface protective agents used in day-to-day practice on the fluoride release property of conventional glass ionomer cements (GIC) and discuss its pros and cons. Materials and Methods: Thirty disc-shaped specimens were fabricated from conventional GIC and block randomized into three groups (Group I, II, and III) of 10 each. Group I specimens were unprotected, group II coated with cavity varnish (Namuvar, Ratnagiri, India) and group III with petroleum jelly (Vaseline, Hindustan lever ltd). After polymerization, the disks were immersed in three individual sealable plastic bottles containing deionized distilled water which was changed every 24 hours for 15 days to measure the fluoride release. Statistics and Results: Statistical analysis was carried using software version Systat 10.0, and the data was subjected to one way ANOVA, using Duncan Multiple Range test (Variable LSD) with the level of significance set at 0.05 (P < 0.05). The greatest amount of fluoride was released from the uncoated group, followed in ranking by petroleum jelly and varnish coated and the difference among them was statistically significant (P < 0.05). Conclusion: Application of varnish over GIC can severely impede its fluoride release property. Similarly petroleum jelly also impedes the fluoride release, but to a very less extent. We suggest that in situations where the fluoride release property is more important than other properties it is better to coat the GIC with petroleum jelly or leave the restoration without any coating.


Keywords: Glass ionomer cement, petroleum jelly, varnish


How to cite this article:
Kamatham R, Reddy SJ. Surface coatings on glass ionomer restorations in Pediatric dentistry-Worthy or not?. J Indian Soc Pedod Prev Dent 2013;31:229-33

How to cite this URL:
Kamatham R, Reddy SJ. Surface coatings on glass ionomer restorations in Pediatric dentistry-Worthy or not?. J Indian Soc Pedod Prev Dent [serial online] 2013 [cited 2019 Aug 20];31:229-33. Available from: http://www.jisppd.com/text.asp?2013/31/4/229/121818



   Introduction Top


Cariostatic activity in tooth colored restorations has been a desirable characteristic in the entire history of modern dentistry. The glass ionomer cements (GICs) are one of the products developed in this direction and are widely used in Pediatric operative dentistry because of their ability to adhere to/bond with enamel and dentin without any pre-treatment and potential to release fluoride ions over a prolonged period of time. [1],[2] Other positive characteristics of GIC include biocompatibility with dental tissues, resistance to microleakage, good marginal integrity and dimensional stability at high humidity, coefficient of thermal expansion similar to tooth structure, and fluoride rechargibility, whereas the GIC possesses undesirable characteristics like early moisture sensitivity, poor wear resistance, low strength and average esthetics. [1],[2] To surmount the problem of moisture sensitivity, the application of different coatings like water proof varnish, petroleum jelly, cocoa butter, or chemical/light cured bonding resins over the surface of the material immediately following the initial set to maintain the water balance during maturation have been suggested [3] and are embedded into practice. However, there is very limited existing literature on the influence of these protective coatings on GICs [4],[5],[6] and even that literature is focused mainly on the manufacturer recommended ones. The recent literature on GICs is concentrating primarily on the procedural aspects, [7] crystal growth, [8] self-reparability [9] and on the properties of GICs containing chlorhexidine diacetate/cetrimide mixtures [10] and poly quaternary ammonium salts, [11] but not on the influence of surface coatings on GIC. Hence, the present investigation has been performed to evaluate the effect of these protective coatings on fluoride release from one of the commercially available GIC, Fuji II, under in vitro conditions. The surface protective coatings selected in the present study were cavity varnish and petroleum jelly (vaseline) as they are routinely used in clinical practice.


   Materials and Method Top


Conventional GIC, Fuji II (GC Corporation, Tokyo, Japan), was chosen for this study. Using standardized brass mold, 30 disk shaped specimens 11 ± 0.1 mm in diameter and 5 ± 0.1 mm thick, were fabricated. GIC was mixed according to the manufacturer's instructions and immediately covered with polyester strip. A glass slab was laid over the top and held under hand pressure to ensure proper placement. Initially they were protected from dehydration and moisture contamination within their molds for a period of 10 minutes (100% relative humidity at 37°C). Any excess material around the periphery was removed with a scalpel and the glass ionomer surfaces were gently polished under water, using wet carborundum paper (32 grit, waterproof, Metallurgy consumables emery papers, Chennai) in a small polishing machine. They were weighed to verify standardization (±0.01 g), block randomized into three groups of 10 each using block size of 6 and table of random numbers. Surface coatings that is for one group, cavity varnish (Namuvar, Ratnagiri, India) and for another group, petroleum jelly (Vaseline, Hindustan lever ltd.) were applied with a brush and then gently air dried. Immediately after polymerization, the disks were immersed in three individual sealable plastic bottles containing 50 ml of deionized distilled water to prevent small volume of test solution becoming saturated with fluoride. The average fluoride concentration in deionized water was <0.01 ppm. These were then left undisturbed in an incubator set at 37° C. After 24 hours, the bottles were removed from incubator and the tooth samples were grasped with clean metal forceps coated with nail varnish and washed with 1 ml of deionized water using a syringe, over the original holding bottle, thus collecting the rinse water in that bottle. The samples were dried for two minutes on absorbent paper and then transferred to a new bottle containing 50 ml deionized distilled water. The deionized distilled water was changed every 24 hours and release of fluoride was measured for 15 days.

Fluoride release was determined after buffering the solution with equal volumes of total ionic strength adjustment buffer (TISAB II), Orion Research, Inc, Beverly, MA, USA). Fluoride release was measured with a combination of fluoride electrode (Orion 9609BN, Orion Research Inc) and an ion analyzer (Orion EA 940, Orion Research Inc). Data concerning fluoride was recorded in parts per million (ppm). Statistical analysis was carried using software version Systat 10.0, and the data was subjected to one-way ANOVA, using Duncan Multiple Range test (Variable LSD) with the level of significance set at 0.05 (P < 0.05).


   Results Top


Total fluoride release

All the three groups of GICs evaluated for the fluoride release during the entire period of the experiment. The amounts of fluoride released from the three groups during 15 days period are presented in [Table 1]. The greatest amount of fluoride was released from the uncoated group, followed in ranking by petroleum jelly coated and varnish coated and the difference among them was statistically significant. Almost 97% of fluoride release was hampered when varnish was used as a protective coating, thus indicating a dramatic decrease in the release [Figure 1].
Figure 1: Mean fl uoride release (in ppm) from GIC with or without surface coatings at different time intervals in de-ionized water

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Table 1: Mean fl uoride release (in ppm) from GIC with or without surface coatings at different time intervals in de-ionized water

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Pattern of fluoride release

The fluoride release in the present study showed a specific pattern. There was an initial burst of release in the first 48 hours and there was a gradual decrease in the release day-by-day irrespective of the surface coating employed.


   Discussion Top


The fluoride release property of GICs is very important especially in Pediatric dentistry, as GIC is the material of choice in techniques such as indirect pulp capping, alternative restorative treatment and interim therapeutic restorations. The benefit of fluoride released from GIC is seen not only in enamel adjacent to the restoration, but also has been reported in areas up to three millimeters away from the restoration's margin and may even offer protection for the entire tooth. [12],[13] The protective role will be more on decalcified dental tissues as they are proved to be more reactive with fluoride, thus preventing further demineralization. [14],[15] Fluoride has been found to neutralize the acid solutions and slightly inhibit the acid production. [16] Also the concentrations of fluoride released from freshly mixed GIC samples have been reported to be sufficient to inhibit and alter bacterial metabolism in vitro, [17] though not substantiated by in vivo studies. [18],[19] Hence the present study has been conducted to determine the effect of the surface coatings on this very important property of GIC.

Despite the wide variations in the amounts of fluoride released in the present study, the pattern of release remained consistent irrespective of the surface coating. There was an initial burst of fluoride release followed by low, prolonged elution. This result is similar to the findings of other studies on conventional and resin modified glass ionomers. [20],[21],[22],[23],[24],[25],[26],[27] Studies done using ion chromatography and ion selective electrodes have also given consistent findings. [28],[29],[30],[31],[32] This pattern can be explained by the proposed mechanisms concerning fluoride release from GICs, that is superficial rinse, diffusion through pores and micro fractures and mass diffusion. Of these mechanisms initial superficial rinsing effect is credited for the high level of fluoride release on the first day, and diffusion through cement pores and fractures for the constant release in the following days, whereas mass diffusion requires more time than considered and consequently occurs with a longer cement contact with storage media. [33] When the amount of fluoride release is considered, application of either varnish or petroleum jelly resulted in decrease of the release. However, the decrease was dramatic in case of varnish. Thus surface protection of GICs definitely impedes the fluoride release property which might be due to the associated reduction in the movement of water. The surface coating might have occluded the mechanism of superficial rinse and diffusion through pores. Thus these findings of the present study affirm those of others done on manufacturer recommended surface protective agents.

Parenthetically, it is a proved fact that exposure of GIC immediately to oral fluids after placement without any surface protection will disturb the water balance in turn affecting the setting reaction. [34] Disintegration of the surface structure, increased surface roughness, inferior translucency and discoloration are documented. [35],[36] Correlation between early exposure to water and poor clinical performance has also been reported. [37] The reason for this has been attributed to washing out of Ca +2 and Al +3 ions and impaired acid base setting reaction, leading to improper matrix formation with inferior mechanical properties with lower compressive strength. [38] It has also been documented in vitro that the sealing of the GIC material for at least 1 hour during the initial setting will produce specimens of optimum compressive strength [29] and it has been attributed to increase in the amount of bound water in the cement; contrarily higher shear punch strength of GIC at 24 hours for uncoated specimens than for coated ones with no significant difference at longer time interval is also reported and they suggested for additional hydration in order to develop maximum shear punch strength rapidly. [5] All these suggest that the subject of water balance in GICs is complicated, and though for most of the purposes, early protection of cements is desirable, it does not favor every aspect of cement maturation. Thus varnish application on the surface of GI restorations for the sake of improving the strength properties cannot be recommended in primary dentition, where the life span of tooth itself is limited and as the chewing forces will be comparatively less in children. If at all the dentist prefers to use a surface protective agent, petroleum jelly can be a viable alternative which has less hindrance on fluoride release.

The major limitation of the present study is that we did not compare the fluoride release from the specimens in different media, as studies have proved that amount of fluoride release under in vitro conditions was more in acidic and demineralizing-remineralizing regimens, followed by distilled water and the least in artificial saliva. [39] As fluoride release is intermediate in distilled water among the three, we have used it in the present study. Another limitation is that we continued the study for only 15 days, the reason for this being a proved fact that the initial high amounts of fluoride decrease rapidly after 24-72 hours and get plateaued to a nearly constant level within 10-20 days. [20],[40] Being an in vitro study is also a drawback as the influence of tooth brushing and dietary habits on the retention of these surface protective agents could not be assessed. Clinical studies are also necessary to compare the advantages of different protective agents over conventional GICs, as results obtained from in vivo studies can differ from those of in vitro studies. Further studies on the influence of these protective agents on the fluoride rechargeability and re-release are also necessary, as they are very important properties of GIC to be called a smart material in dentistry.


   Conclusion Top


  1. Application of varnish over GIC can severely impede its fluoride release property.
  2. Application of petroleum jelly also impedes the fluoride release, but to a very less extent.
  3. In situations where the fluoride release property is more important than other properties it is better to coat the GIC with petroleum jelly or leave the restoration without any coating.


Thus the pediatric dentist should wisely decide whether to apply surface coating or not, and if decided to apply which one to be used.

 
   References Top

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