Comparative Evaluation of Compressive Strength and Flexural Strength of GC Gold Hybrid, GIC Conventional and Resin-modified Glass-ionomer Cement.

Purpose: The aim of the study was to emphasize the compressive strength and flexural strength of glass-ionomer cement (GIC)-gold hybrid, conventional GIC, and resin-modified GIC (RMGIC). Methodology: Three GIC materials were used in the study: group A: GC-gold hybrid (Gold Label hybrid Universal Restorative), group B: type II conventional GIC, and group C: RMGIC. A total of 120 cylindrical test specimens of dimensions 4 mm diameter × 6 mm height were prepared from a custom-made Teflon mold according to respective study groups. The specimens prepared were then stored in 20 mL of deionized water at 37°C for 3 h daily for 30 days, and the solutions were changed every week, after which they were tested for compressive strength and flexural strength by using a universal force testing machine. All the results were analyzed by SPSS software and were subjected to statistical analysis using ANOVA followed by the Bonferroni post-hoc test.
Results: The mean compressive strength was the highest for group A and lowest for group B. Similarly, the mean flexural strength was the highest for group A and lowest for group B.
Conclusion: The conclusions can be drawn from this in-vitro study that the compressive strength and flexural strength of GC-gold hybrid were greater than those of RMGIC and conventional GIC. Copyright:

INTRODUCTION

In dentistry, operators have always encountered the common problem of replacing missing tooth structures with artificial materials with regard to both aesthetics and function restoration. The ability of the dentist to accomplish the desired result has been limited by certain basic factors such as the availability of suitable materials compatible with the hazards present in the oral cavity and the development of an appropriate process for their daily use. Ideally, a restorative material should have physical properties identical to those of the tooth and should mimic it aesthetically.[1] During the first half of the 19th century, amalgam and gold were developed as viable restorative materials for dentistry.[2] However, their poor aesthetic properties led to the development of dental cement and more aesthetically acceptable restorative materials. Glass-ionomer cements (GICs) were a step in this direction and have now become one of the most commonly used restorative materials in dental practice.

GICs are classified as acid-base cements. They are formed as a result of a reaction between weak polymeric acids and powdered glasses, with the final structure containing filler particles in the form of unreacted glass, which helps in reinforcing the set cement.[3] Conventional GICs have been used in the oral cavity mainly due to their favorable properties such as the ability to bond to the tooth structure, fluoride release, bactericidal ability, and the potential to promote remineralization.[4] However, despite these advantages, GICs are not considered as first-choice restorative materials such as amalgam or resin composites.

Self-adhesive posterior restorative material featuring GC–glass hybrid technology is a combination of two types of fluoro-alumino-silicate (FAS) glass and two types of polyacrylic acid. It has small particle size distribution, resulting in higher mechanical strength. Gold label hybrid consists of glass that reacts with polyacrylic acid, helping the restorative matrix release a high amount of fluoride. It consists of more acid-resistant FAS glass and high-molecular-weight polyacrylic acid. These two components strengthen the restorative matrix and give higher acid resistance. The fine size of FAS glass particles decreases collision against visible light waves. More light passes through the restorative material, making it more translucent.[5678] This study emphasized the compressive strength, tensile strength, and flexural strength of GIC–gold hybrid, conventional GIC, and resin-modified GIC (RMGIC).

METHODOLOGY

Three GIC materials were used in the study: group A: GC–gold hybrid (Gold Label hybrid Universal Restorative), group B: type-II conventional GIC, and group C: GMGIC.

A total of 120 cylindrical test specimens of dimensions 4 mm diameter × 6 mm height were prepared from a custom-made Teflon mold according to respective study groups. A thin layer of petroleum jelly was coated on the lateral walls of the mold to prevent material adhesion. The powder and liquid of the GC–gold label, conventional GIC, and RMGIC were mixed according to the manufacturer's instructions and placed in the molds. The mixed material was placed inside cylindrical Teflon molds placed on a glass slide and covered by a MylarR strip. A second strip and a glass slide were used to cover the mold. The RMGIC samples were light-cured for 20 s from each side by using a LED curing unit with an irradiance of 980 mW/cm2 monitored with a radiometer. In the case of GIC samples, they were removed from the mold after the setting time specified by the manufacturer. Flashes and irregularities were removed using #600 SiC paper and protected with one layer of GIC varnish, allowing the solvent to evaporate for 2 min. The specimens were then stored in 20 mL of deionized water at 37°C for 3 h daily for 30 days, and the solutions were changed every week, after which they were tested for compressive strength and flexural strength by using a universal force testing machine. All the results were analyzed by SPSS software and were subjected to statistical analysis using ANOVA followed by the Bonferroni post-hoc test.

RESULTS

The mean compressive strength was the highest for group A and the lowest for group B. Similarly, the mean flexural strength was the highest for group A and the lowest for group B. Hence, overall, the following result was obtained: GC–gold hybrid > RMGIC > conventional GIC.

DISCUSSION

GICs are the material of choice for atraumatic restoration treatment[9] and for restoring cervical dental lesions. They are preferred as they release fluoride and provide chemical adhesion with tooth structure, requiring minimal preparation.[3] However, one of the major drawbacks of GICs is their relatively low fracture strength compared to modern resin composite materials.[10] Therefore, the current study assessed and compared the flexural strength and compressive strength of GC–gold label hybrid, RMGIC, and conventional GIC (Fuji IX). The methodology adopted by a previous study was duplicated in our research and was aimed at determining whether similar results could be obtained.[11] The flexural strength is a commonly evaluated mechanical property of the material as it is more susceptible to showing subtle changes in the substructure than compressive strength tests.

In the present study, The mean compressive strength was the highest for group A and the lowest for group B as shown in [Table 1]. Similarly, the mean flexural strength was the highest for group A and the lowest for group B as shown in [Table 2]. Hence, overall, the following result was obtained: GC–gold hybrid > RMGIC > conventional GIC. Similar results have been reported in previous literature.[111213] Poornima et al.[13] compared the compressive strength and surface microhardness of EQUIA Forte, light cure, and conventional GIC. Fifty-four pellets of G-Coat (GC) Gold Label 2, GC Gold Label light-cured universal restorative material, and EQUIA Forte GIC were prepared. Comparing the compressive strength of EQUIA Forte from day 1 to 30 when placed in artificial saliva, there was a significant increase on day 30 (P = 0.007) compared to other groups. The surface microhardness of EQUIA Forte from day 1 to 30 when placed in artificial saliva non significantly decreased compared to other groups. Surface microhardness and compressive strength of EQUIA Forte were significantly high in comparison to the other groups. Bali et al.[14] explored the influence of the addition of 8% hydroxyapatite to conventional GIC on its compressive strength when immersed in different storage media and antibacterial activity. One hundred and twenty six pellets of the specific dimension of 6 mm × 4 mm were prepared and divided into six groups and were immersed in deionized water, artificial saliva, lactic acid solution, respectively, for 3 h every day over the 30-day test period. GIC ± HAp showed significantly greater antibacterial activity against Streptococcus mutans when compared to the GIC group. There was no statistically significant change in the compressive strength among the groups except for group 3 and group 6 when immersed in lactic acid, which had shown a significant difference at the end of 24 h. The addition of 8% hydroxyapatite to GIC showed marked increased in the antibacterial activity of the conventional GIC against caries initiating organism without much increase in the compressive strength of the GIC when immersed in the different storage media.

Table 1

Comparison of compressive strength between different time intervals in each group and subgroup

Group	Mean	n	SD	P
Group A	261.43	40	1.12	0.000 (Significant)
Group B	170.75	40	2.16
Group C	201.80	40	19.09

Table 2

Flexural strength (MPa)

Group	Mean	n	P
Group A	26.66	40	0.000 (Significant)
Group B	23.53	40
Group C	25.89	40

CONCLUSION

The following conclusions can be drawn from this in-vitro study: the compressive strength and flexural strength of GC–gold hybrid are greater than those of RMGIC and conventional GIC.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.