Introduction

Oral cavity is colonized by more than 10⁹ bacteria and contains a remarkably diverse microbiome, with more than 700 species reporte (1). Chronic periodontitis is a common oral disease with diverse bacterial etiology. Oral and periodontal surgical sites being moist and favorable for accumulation and retention of microorganisms, are most susceptible to post-surgical infection and delayed wound healing. Bacterial colonization of sutures might lead to bacteremia and has been reported to contribute to post-surgical complications in dentoalveolar and periodontal surgeries (1).

Application of sutures requires passage of a foreign material through tissue which predisposes tissues to extreme reactivity. This also allows for the retention of microorganisms into the tissue which might lead to infection (2). Silk sutures sometimes exhibit the phenomenon of ‘wicking’ and can be a site of retention and ingress of bacteria.(3) Cyanoacrylates have been used as an alternative to braided silk, which is the most common suture material used for closure of oral wounds(3).  Cyanoacrylates are tissue adhesives that were synthesized in 1959 by Coover et al. which demonstrate properties of an ideal wound closure agent. These are liquid monomers that polymerize on contact with wound moisture to form a solid bond. These solidified adhesives unite and hold the incised tissues stably, avoiding penetration of foreign bodies, thus promoting wound healing and vascularization(4,5). This favours clot stabilization and provides aesthetics to the surgical site (4).

An ideal surgical tissue adhesive must meet the following criteria: strong binding strength, ease of application, tissue biocompatibility, biodegradable and reasonable cost. Cyanoacrylates demonstrate most of these properties, giving them an edge over the conventional wound closing agents. These adhesives have strong adhesion to tissues in the presence of moisture, workable polymerization time, haemostasis, enhanced elimination of dead space, bacteriostatic ability, reduction in postoperative pain and biodegradability (6).

The use of cyanoacrylate-based adhesives in periodontal surgery, has demonstrated ease and efficiency, minimizing the problems generated by suture thread. The antimicrobial properties of cyanoacrylate tissue adhesives have been extensively investigated in other fields of medicine (7,8) However, there is a dearth in the literature on the antibacterial effect of cyanoacrylates in oral environment against the oral microflora. The present study was undertaken with the aim of assessing antimicrobial properties of two commonly used formulations of cyanoacrylate tissue adhesives against oral pathogens.

We hypothesized that cyanoacrylate tissue adhesives express significant antibacterial properties against oral pathogens and the null hypothesis was that cyanoacrylate tissue adhesives would not possess significant antibacterial properties against oral pathogens.

Materials and Methods

Two cyanoacrylate tissue adhesives were studied in this in vitro study: n-butyl + 2-octyl cyanoacrylate (B+OC) (Periacryl^®90-HV) and iso-amyl cyanoacrylate (AC) (VERIBOND^®) [fig 1a & 1b]. Six microliters of cyanoacrylate adhesive was applied on standard filter-paper discs, using micropipettes under sterile conditions.

Previously cultured anaerobic colonies of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis & Tanerella forsythia were incubated in Blood agar plates and aerobic colonies of Lactobacillus amylovorus and Staphylococcus aureus were incubated in Brain-Heart infusion agar. In each agar plate, a sterile blank disc without adhesive was placed in the center as a control. Six additional discs with six microliters of adhesive on each disk were placed onto the cultures: three with polymerized (solidified) B+OC and three with polymerized AC. To achieve prior polymerization of cyanoacrylate, the adhesive-soaked discs were exposed to air under a sterile hood for 10 min before being placed on the cultures.

Plates for anaerobic and aerobic bacterial cultures were incubated at 37°C for 48 & 24 hours respectively. After the completion of incubation period, the bacterial inhibitory halos were measured in millimeters (Fig 2a-e). In order to evaluate whether the bacterial inhibitory halos were the result of mere bacteriostasis or actual bactericidal effects, samples were collected from the clear agar within the inhibitory halos and re-cultured on new bacterial culture plates. The new plates were incubated at 37°C and analyzed after 48 h for anaerobic bacteria & after 24h for aerobic bacterial cultures (Fig 3a-e). Finally, the bactericidal activity was measured by calculating the percentage of plates with no bacterial growth.

Mann Whitney U test was used to analyse the collected data.

Figure 2. Bacterial inhibitory halos against :

figure 2a. Streptococcus aureus  

figure 2b. Lactobacilli amylovorus 

figure 2c. Tanerella forsythia 

figure 2d. Porphyromonas gingivalis 

figure 2e. Aggregatibacter actinomycetemcomitans     

With a blank disk in the center, B+OC on left side and AC right side.

figure 2a. Streptococcus aureus

figure 2b. Lactobacilli amylovorus

figure 2c. Tanerella forsythia

figure 2d. Porphyromonas gingivalis

figure 2e. Aggregatibacter actinomycetemcomitans

with a blank disk in the center,  B+OC on left side   and AC right side.

Figure 3. Bactericidal activity against :

figure3a. Streptococcus aureus                      

figure3b. Lactobacilli amylovorus 

figure3c. Tanerella forsythia                           

figure3d. Porphyromonas gingivalis

figure3e. Aggregatibacter actinomycetemcomitans

with B+OC on left side and AC on right side.

figure3a. Streptococcus aureus 

figure3b. Lactobacilli amylovorus

figure3c. Tanerella forsythia

figure3d. Porphyromonas gingivalis

with B+OC on left side and AC on right side.

Results

Table.1 shows the mean and standard deviation (SD) of the inhibitory halos (mm) for B+OC and AC for each microorganism studied. Under the conditions employed, both formulations of cyanoacrylate had a potent inhibitory effect against all test organisms. The diameter of inhibition zone ranged from 8 – 22 millimetres. The antibacterial efficacy of the two formulations was comparable (graph 1). A the test microorganisms, the zones of inhibition against Gram positive bacteria (Staphylococcus aureus & Lactobacillus amylovorus) were found to be larger than the Gram negative bacteria (Aggregatibacter actinomycetemcomitans, Tanerella forsythia & Porphyromonas gingivalis).

The bactericidal activity of AC ranged from 0% to 100% whereas B+OC showed bactericidal activity of upto 50% against the tested organisms(graph2). The bactericidal activity of AC was found to be more potent than B+OC against P.gingivalis and T.forsythia. Amongst the tested microorganisms, both formulations of cyanoacrylate showed maximum bactericidal activity against P.gingivalis and least against L.amylovorus.

Table 1 Individually the formulations showed potent inhibitory effect against all test organisms. Comparison between the groups did not reveal statistically significant results.