Comparison of Antibacterial Activity of Various Additives to Glass Ionomer Restoration: An In Vitro Study

ABSTRACT

Introduction:

Glass-ionomer (GIC) cement was introduced in 1972 as a “new filling material of dentistry”. It is bioactive and plays an important role in caries prevention due to its ability to release fluoride into the oral environment and remineralization of dental hard tissues. However, its properties such as moisture sensitivity, wear resistance, and bond strength are not sufficient to inflict the antimicrobial environment. This in vitro study aimed to evaluate the antibacterial property of four different GIC cements against S. mutans and L. acidophilus.

Methodology:

This study was conducted on 120 disk-shaped samples (30 for antibacterial activity), which were placed in Petri dishes holding Müeller Hinton agar. Bacterial strains were overhauled in the brain heart infusion culture medium, and by utilizing disposable straps on blood agar medium, 100 ml of the strain inoculum was plated out. Through the diffusion method on the solid medium, the antibacterial activity of GIC was determined.

Results:

The antibacterial activity was the highest for Riva silver and chemifill rock for 24 and 72 hours, respectively. For 48 hours, Equia forte and chemifill rock had the highest antibacterial activity, and there was a significant difference between the groups.

Conclusion:

Ketac™ molar easymix inhibited the growth of S. mutans and L. acidophilus but had the lowest antibacterial effect compared to other GICs.

INTRODUCTION

Dental restorative materials must meet basic requirements, including similarity to the tooth structure in terms of their mechanical, physical, and esthetic properties. In 1972, Wilson and Kent introduced glass-ionomer cement (GIC) as a “new filling material of dentistry that is translucent” and recommended for the restoration of cervical lesions. It consists of a powdered fluoroaluminosilicate glass and a polyalkenoic acid.[1] GIC restorative materials play an crucial role in caries prevention because of their ability to release fluoride into the oral environment and initiate the process of remineralization of the tooth structure at the interface between tooth, biofilm, and saliva.[2,3] These are the conventional restorative materials that are bioactive and have a wide spectrum of uses, such as the liner of the tooth structure, bonding of the cement and cementing, or restoration of a tooth structure with decay. Nonetheless, the properties of GIC that stand out in dentistry are its adhesive property to release fluoride and esthetic appearance, sensitivity to moisture, and wear resistance, which are not requisite as they are desired.[4,5,6]

METHODOLOGY

The study was conducted in the laboratory under direct observation and documentation. The institutional review board ethically cleared the study for conduction, and sample size determination was done based on the previous research. In this in vitro study, four types of GICs were used: Equia forte ht, a glass hybrid GIC (GC, Tokyo, Japan); Ketac™ molar easymix, a cGIC (3m-espe, Germany); Riva silver, a silver-reinforced GIC (SDI, Australia); and Chemfil rock, a zinc-added GIC (Dentsply de trey, Konstanz, Germany).

There were a total of 120 disk-shaped samples (30 for antibacterial activity) with a thickness of 2 mm and a diameter of 5 mm. According to the manufacturer guidelines, the products were manipulated into Petri dishes, which contained the Müeller Hinton agar. Using a vernier calliper, the measurement of the diameter of halos og bacterial growth inhibition was assayed and the antibacterial activity was determined. Bacterial strains were overhauled in the brain heart infusion culture medium. 100 ml of the inoculum of strains was plated on the blood agar medium at 37°C in a bacteriological incubator after a 24 h period of incubation. Through the diffusion method on the solid medium, the antibacterial activity of GIC was determined.

RESULTS

The evaluation of antibacterial activity of the four different types of GIC used against S. mutans was done. The antibacterial activity was the highest for GICs 3 and 4 for 24 and 72 hours, respectively. For 48 hours, GICs 1 and 4 had the highest antibacterial activity [Table 1].

Table 1.

Different types of GICs

Code	Composition
GIC 1	Equia forte ht, a glass hybrid GIC (GC, Tokyo, Japan)
GIC 2	Ketac™ molar easymix, a cGIC (3m-espe, Germany)
GIC 3	Riva silver, a silver-reinforced GIC (SDI, Australia);
GIC 4	Chemfil rock, a zinc-added GIC (Dentsply de trey, Konstanz, Germany)

In the evaluation of the antibacterial activity against L. acidophilus, GICs 1 and 4 yielded the highest for 24 hours. GICs 3 and 4 showed the highest for 48 and 72 hours, respectively [Table 2].

Table 2.

Antibacterial activity of the 4 types of GIC

	Groups	Mean and standard deviation			Friedman P*
		Mean±sd (2nd day)	Mean±sd (4th day)	Mean±sd (6th day)
S. mutans	GIC 1	11.34±1.07	12.36±0.32	7.96±0.24	P<0.05
	GIC 2	7.43±0.88	6.99±0.34	7.32±0.41
	GIC 3	13.00±1.6	8.94±0.56	8.54±1.2
	GIC 4	13.78±1.77	11.45±0.64	8.98±0.52
L. acidophilus	GIC 1	13.12±0.42	10.79±0.49	8.58±0.35	P<0.05
	GIC 2	7.92±0.56	6.86±0.31	6.87±0.14
	GIC 3	10.90±1.23	11.53±1.03	7.49±0.21
	GIC 4	13.51±0.71	12.72±0.37	9.81±0.24

Table 3 shows there was a significant difference found between the groups and within the groups for antibacterial activity for 48 hours.

Table 3.

Analysis of variance comparing different groups for antibacterial efficacy

Variable	Intercomparison	Sum of squares	Df	Mean squares	F	Sig
Antibacterial efficacy	Between the groups	1398.028	6	273.031	3.840	0.001
	Within the groups	2037.132	38	42.991
	Total	4729.927	41	0.2387

DISCUSSION

Dental caries is considered as a major public health problem globally and is the most widespread non-communicable disease (NCD). It was the most prevalent condition ranking first for decay of permanent teeth (2.3 billion people) and 12^th for deciduous teeth (560 million children) in the 2015 Global Burden of Disease study. Dental caries can be prevented by avoiding dietary free sugars. Moreover, dental caries is largely preventable through simple and cost-effective population-wide and individual interventions, whereas treatment is costly and is often unavailable in low- and middle-income countries.[6] In the light of these scenarios, restorative and preventive dentistry is gaining importance. The ideal restorative material is of crucial importance. One among them considered is GIC, which is the most accepted acid-based cement in restoring tooth with dental caries because of its distinct properties like chemically based adhesion to the tooth structure, biocompatibility, fluoride releasing capability, and decreased thermal expansion. The feature that attributes to its antibacterial capacity is its ability to release fluoride. However, to inhibit the secondary caries formation due to microbial growth beneath a restoration, its properties are not sufficient and effective.[7,8] GIC also exhibits properties such as high dissolution in water sorption, decreased wear resistance, and reduced fracture toughness, which would further lead to failure of restoration.[8] Different agents were incorporated to overcome these limitations and to increase its antimicrobial efficacy without influencing its mechanical properties.[9,10,11,12] Nonetheless, it contains some limitations, and there is a need for further randomized controlled trials to be conducted.

CONCLUSION

Ketac™ molar easymix inhibited the growth of S. mutans and L. acidophilus but had the lowest antibacterial effect compared to other GICs. The distinct antibacterial properties may be due to the varied chemical compositions, release of fluoride and other ions, and low pH values during setting. Randomized controlled trials should be conducted.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.