INTRODUCTION:

The primary teeth are necessary to preserve the integrity of the dental arch.(1) Periradicular lesions in the primary teeth are of major concern in primary teeth because it causes spread of infection to the developing permanent teeth. Preserving the primary dentition is essential for physiological and social development of the children.(2) Therefore appropriate treatment is to be provided to completely eliminate the oral flora from the root canals by bio-disinfection which promotes enhanced healing and prevents reinfection. Pulp canal infections are polymicrobial in nature with majority of facultative anaerobes and aerobes.

Streptococcus salivarius is the principal commensal seen in oral cavity. It is a gram positive facultative anaerobic cocci. The presence of murein layer makes it a resistant organism to survive even in less osmotic conditions.(3)Some authors have studied the prevalence of microorganisms and reported that Streptococcus salivarius were seen dominating in primary teeth with necrotic pulp and periapical lesions.(4,5)The predominance of Streptococcus salivarius were seen inperiapical abscess in children.(6)It is difficult to eliminate these bacteria from contaminated root canals. Streptococcus salivarius were found regularly in primary culture of the samples contaminated with saliva. (7) Over many years various materials have been used as a intracanal medicament in primary teeth like formocresol, glutaraldehyde, calcium hydroxide, chlorhexidine gel, corticosteroids and some antibiotics. Calcium hydroxide is the most commonly used intracanal medicament in endodontic treatment. Due to the alkaline nature of calcium hydroxide it does not eliminate certain facultative anaerobes like Streptococcus salivarius, E. faecalis etc. In the view of finding newer approaches for treatment of periradicular lesion, lesion sterilization and tissue repair (LSTR) technique was introduced in 1996 to disinfect pulpal, and periapical lesions.(8) This technique used a combination of antibiotics like ciprofloxacin, metronidazole and doxycycline were used to remove the harboured microbes in root canal dentine.(9) It is important to have the appropriate knowledge of the antimicrobial sensivitivity testing of various endodontic pathogens to use the necessary medicaments under resistant root canal infections.(10) There is a lacuna of evidence available in the literature evaluating the antimicrobial effectiveness of TAP against Streptoccus salivarius. This study aims in determining the stability of TAP over a period of time by evaluating the antibacterial effect of various concentrations of Streptococcus salivarius by antimicrobial susceptibility testing.

MATERIAL AND METHODS:

The study approval was obtained from the institutional review board, Saveetha Dental College. (TAP) Triple antibiotic paste made of metronidazole, ciprofloxacin, doxycycline (1:1:1) were prepared by using sterile mortar and pestle with different concentrations of triple antibiotic paste using propylene glycol as a carrier in the ratio of 1:1 and stored under sterile conditions. The antimicrobial effect of triple antibiotic paste was tested by antimicrobial susceptibility testing against Streptococcus salivarius by using Agar disc diffusion method over the period of one day and after 3 days. The samples were divided into three groups: Group 1, 1% TAP; Group 2, 2% TAP; Group 3, 3%; Group 4, Chlorhexidine (control). Mueller- Hinton agar plates were used and inoculated with Streptococcus salivarius and sterile discs with different concentrations of Triple antibiotic paste were placed over it and incubated for 24 hours at 37 °C for 24 hours.(11) The zone of inhibition was measured after 24 hours and recorded in millimeters and the same procedure was repeated after 3 days, 7days, 14 days and 21 days. The results were analyzed statistically by the Kruskal-Wallis test at 5% significance level.

RESULTS:

The inhibitory zones at various concentrations of triple antibiotic paste and chlorhexidine against streptococcus salivarius are shown in (ig 1 and Table 1). From the disc diffusion method, it was observed that the zone of inhibition for (Group 1; 1% TAP) was 26mm 25mm, 26mm, 29mm and 32mm at 24h, 3 days,7 days, 14 days and 21 days (Group 2; 2% TAP) was 28mm, 26mm, 27mm, 31mm and 33mm (Group 3; 3% TAP) was 31mm 31mm, 37mm, 39mm and 41mm at 24h, after 3 days,7 days,14 days and 21 days respectively. (Group 4; Chlorhexidine) showed a zone of inhibition of 27mm, 23mm, 21mm, 18mm and16mm at 24h, after 3 days,7 days,14 days and 21 days respectively. The greater antimicrobial effect of TAP was seen for higher concentration and consequently increased over the period of 21 days (Figure-1 and Table- 1). The antimicrobial effect of triple antibiotic paste increased after 3, 7 14 and 21days. But chlorhexidine showed a lesser zone of inhibition after 14 and 21 days compared to 24 hours of incubation against Streptococcus salivarius.

Figure 1: Zone of Bacterial inhibition against Streptococcus salivarius

DISCUSSION:

The ulmitate goal of pulp therapy is to restore the teeth in its ideal functional position to maintain the integrity of the dental arches. The intracanal medicament placement may help to reduce the microbes harbouring the root canal in between appointments.(12) The Antibiotics are used in treating many infectious diseases. Many bacteria in the root canal develop resistance to certain antibiotics due to constant use of antibiotics for treatment of wide range of infections limiting its antibacterial effect.(13) The systemic delivery of antibiotics is difficult reaching the root canals of non vital teeth, since there is no blood supply which is required for adequate absorption and distribution of the medicament. Topical application of antibiotics allows for better absorption and provides effective sterilization. (13) Intracanal application of antibiotics can destroy the pathogens during endodontic therapy.(14) William Windley et al., 2005 observed that the antimicrobial effect was less post-irrigation and the microbes decreased after placement of triple antibiotic paste for a period of 2 weeks.(15)

Triple antibiotic paste consists of mixture of two antibiotics and one corticosteroid. Metronidazole, ciprofloxacin and tetracycline combinations were used for the past few years. Mechanism of action of tetracycline is that it inhibits collagenase and matrix metalloproteinase thereby producing anti-inflammatory effect.(15) But, the use of tetracycline like minocycline has shown to cause crown discoloration.(16) So in this present study doxycycline was used.

Studies have shown that TAP provides effective disinfection of the root canals after 24 to 48 hour application.(17,18) There are various methods available in the literature for evaluating the anti-bacterial effect. Disc diffusion method was used in this study due to its simplicity and rapid detection of antimicrobial property and its ability to penetrate deep into the plasma membrane of the bacteria which proves its superior antibacterial effect. But it does not test the toxicity against specific microorganisms.(19) Most commonly used intracanal medicament used is calcium hydroxide. Calcium hydroxide has been widely used as an intracanal medicament. Several studies have reported that due to alkaline ph of calcium hydroxide there is difficulty in eliminating resistant microrganisms.(20) In this study, chlorhexidine has been used as a control as it possess various properties like superior antimicrobial activity, substantivity, lower cytotoxicity and its clinical effectiveness compared to other medicaments as it has the capacity to inhibit matrix metalloproteinase.(21) It removes the smear layer produced during mechanical instrumentation.(22,23) Chlorhexidine has better antibacterial property compared to Ca(OH) against resistant bacteria present in the root canal. TAP showed a favourable healing and repair of periradicular tissue when used as an intracanal medicament in non surgical endodontic therapy.(24)

Streptococcus salivarius was used as a test organism in the present study. It has been observed by J.P Burton et al., 2005 that Streptococcus salivarius was detected in the human saliva.(25) In this study 1, 2 and 3% TAP was used because it has been reported that higher concentration of TAP may cause adverse effects on the stem cells of dental papilla.(26) Under the limitations of this in vitro study, higher concentrations of triple antibiotic paste can effectively eliminate Streptococcus salivarius from the root canals compared to chlorhexidine. The antibacterial effect of intracanal medicaments increased after 21days, thus confirming its stability and antibacterial efficacy.

FUTURE PERSPECTIVES FOR RESEARCH:

In future more in vivo studies are advocated to determine the stability and antibacterial effect of TAP under proper oral conditions against Streptococcus salivarius for a longer period of time to confirm the findings obtained from this study.

ACKNOWLEDGEMENT:

Authors would like to thank Department of Microbiology for their guidance and support.

CONFLICT OF INTEREST:

Nil.

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Received on 05.11.2017 Modified on 07.12.2017

Research J. Pharm. and Tech 2018; 11(4):1327-1330.

DOI: 10.5958/0974-360X.2018.00247.0