Comparison of Antimicrobial Efficacy and Physical Properties of Antibiotic-Modified, Propolis-Added, and Conventional Glass Ionomer Cement

Abstract

Objective:

To evaluate the antimicrobial efficacy and physical properties of antibiotic-modified GIC, propolis-incorporated GIC, and conventional GIC.

Study Design:

An antibiotic mixture containing ciprofloxacin, metronidazole, and doxycycline and propolis tincture were mixed with GIC to obtain two study groups and Fuji IX as a control group. Antibacterial action, fluoride release, and physical properties were evaluated.

Results:

Addition of antibiotics and propolis to GIC increased its antimicrobial action without negatively modifying physical properties of conventional GIC.

Conclusion:

Hence, the incorporation of antibiotics and propolis into GIC provided an acceptable combination of properties.

INTRODUCTION

There has been a shift from extension for prevention to minimal intervention approach, like atraumatic restorative treatment (ART), especially for young children, those with dental anxiety.[1] ART uses manual instruments to remove caries and restore with glass ionomer cement (GIC), providing adhesion to dental tissues, fluoride release, biocompatibility, and antimicrobial properties, making it highly appealing.[2] However, some residual bacteria may remain under the restoration, potentially leading to secondary caries and failure over time. Thus, there is a need to improve ART using materials with enhanced antibacterial properties.

Propolis is a natural resinous substance produced by honey bees. It exhibits antimicrobial, anti-inflammatory, anesthetic, and healing properties.[3] Recently, adding antimicrobials to GIC, such as combination of ciprofloxacin, metronidazole, and minocycline, has shown to be successful in managing carious lesions.[4]

The literature lacks data comparing the properties of GICs modified with antibiotics or propolis to conventional GIC. This study evaluated the impact of adding propolis and an antibiotic mixture on the antibacterial activity, fluoride release, and physical properties of conventional GIC.

METHODOLOGY

This in vitro experimental study compared the antimicrobial efficacy and physical properties of three types of GIC: (a) Group 1—conventional GIC modified with an antibiotic mixture of ciprofloxacin, metronidazole, and doxycycline (1:1:1 ratio), (b) Group 2—conventional GIC with propolis tincture added to the liquid, and (c) Group 3—conventional GIC as the control.

Preparation of study materials

In Group 1, antibiotic tablets had their sugar coatings removed, then were ground into fine powder using a pestle and mortar. A mixture of 20 mg each of ciprofloxacin (200 mg tablets, Okacet, Cipla), metronidazole (200 mg tablets, Unique’s Metrogyl), and doxycycline (100 mg tablets, Actavis) was prepared in a 1:1:1 ratio and added to 3940 mg of GIC powder. This antibiotic–GIC mix was combined with liquid at a powder/liquid ratio of 3.6:1 and mixed on a pad for 30 seconds. Group 2 involved mixing propolis tincture (Source Naturals, 29.57 ml) with the GIC liquid in a 1:1 ratio before mixing with GIC powder at the same ratio and conditions.

Preparation of specimens from standardized molds

Commercially available linear low-density polyethylene tubing was cut using a microtome to create 150 molds, each 4 mm in diameter and 10 mm in height, divided equally into Groups. The mixed study materials were placed into molds. Specimens set for 30 minutes at room temperature, then were carefully removed by applying pressure with a condenser. Specimens for antimicrobial testing were inoculated immediately, while those for compressive strength were stored in distilled water at 37°C for 24 hours.

Evaluation of antibacterial activity

Ten specimens from each experimental group were evaluated for antibacterial activity, with 30 specimens tested against Streptococcus mutans (MTCC 497) and 30 tested against Lactobacillus casei (MTCC 1423). The agar inhibition test was used to assess the antibacterial activity of the cement specimens.

Evaluation of shear bond strength

Thirty occlusal dentin specimens were obtained from human premolar teeth. The exposed, polished, flat dentin surface was conditioned with polyacrylic acid for 10 seconds. Ten dentin specimens were allotted to each test group. The powder and liquid of each group were mixed and placed in the center of the prepared dentin surface by packing the material into resin molds. The specimens were stored at 37°C and 100 percent humidity for 24 hours, after which the shear bond strength was measured using a universal testing machine.

Evaluation of micro leakage

Fifteen freshly extracted, caries-free human premolars were cleaned, polished, and prepared with standardized Class V cavities (4 mm diameter, 2 mm depth) on the buccal surfaces. After rinsing, drying, and conditioning, cavities were restored with five teeth per experimental group. Restorations were finished after setting. Following 24 hours in saline at 37°C, teeth underwent 1,000 thermocycles between 5°C and 55°C with 30-second dwell and 15-second transfer times. The apices were sealed with GC Fuji IX glass ionomer, and all surfaces except a 2 mm margin around restorations were coated with two nail varnish layers. Teeth were immersed in 2% methylene blue for 48 hours, then rinsed and sectioned buccolingually with a diamond bur, yielding two sections per tooth.

RESULTS AND STATISTICAL ANALYSIS

Data were analyzed using SPSS version 22.0. Results were obtained as means with standard deviations. Comparisons were performed using analysis of variance (ANOVA) and paired t-tests. A P value of 0.05 or less was considered statistically significant.

Antibacterial activities and fluoride release

In comparison with the mean inhibition zones against S. mutans at 24 hours and L. casei at 48 hours, the control group showed no inhibition, while Group 1 had a significantly larger inhibition zone than Group 2 (P < 0.001). At seven days, the control showed no inhibition, and Group 1 continued to outperform Group 2 significantly (P < 0.001). At 24 hours, Group 1 exhibited the lowest fluoride release, while Group 3 released significantly more fluoride than Group 2. However, fluoride release significantly decreased in all groups from 24 hours to seven days.

Calculation of setting time, compressive strength, shear bond strength, and microleakage

The highest mean net setting time was observed in Group 2 (648.0 ± 76.27 seconds), followed by Group 1 (466.0 ± 57.77 seconds) and Group 3 (388.0 ± 59.40 seconds). The differences in net setting time between the groups were highly significant. Group 3 exhibited the highest mean compressive strength, followed by Group 2 and then Group 1 (P < 0.001). Group 1 showed the highest mean shear bond strength. Least shear bond strength was observed with Group 3. Group 2 showed low mean value as compared to Group 1 and higher than Group 3. The highest microleakage scores were observed with Group 2 (1.4 ± 1.19). Group 1 (1.2 ± 0.75) and Group 3 (1.0 ± 0.64) showed almost similar results after evaluation (P > 0.0001).

DISCUSSION

GIC modified with antibiotics and propolis showed significantly better inhibition of S. mutans and L. casei compared to conventional GIC by reducing microbial adherence to the cement and inhibiting biofilm formation after 48 hours of incubation.[5] Devi K proved the superior antimicrobial effectiveness of Miswak-modified GIC against S. mutans.[6] However, Coogan[7] reported that conventional GIC also exhibited considerable antibacterial effects.

Conventional GIC had the highest fluoride release, followed by propolis-incorporated GIC, while antibiotic-modified GIC released the least. Propolis creates pathways within the GIC matrix that aid fluoride ion release. Additionally, as propolis is plant-derived and some plants naturally contain fluoride, hence, it may contribute to the higher fluoride release compared to antibiotic-modified GIC.[8]

Many authors[9,10] have confirmed the occurrence of an initial high fluoride release from glass ionomers over the first 24 hours, probably due to the burst of fluoride released from the glass particles when reacting with the polyalkenoate acid during the setting reaction.

The setting time was longest for propolis-incorporated GIC, followed by antibiotic-modified GIC, with conventional GIC setting the fastest. In compressive strength, conventional GIC outperformed both modified materials.

This study demonstrated that adding antibiotics and propolis to GIC improved antimicrobial activity without harming its mechanical properties.

CONCLUSION

Addition of antibiotics and propolis to GIC increased its antimicrobial action without negatively modifying physical properties of conventional GIC.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.