Evaluation and comparison of microbial colonization on nickel titanium (NiTi) closed coil springs and active tie-backs during orthodontic space closure: An in-vivo study

Abstract

Objective: Literature suggests that the mode of ligation and use of elastomeric chains for achieving orthodontic space closure may result in a significant increase in microbial colonisation. The objective of the present study was to evaluate and compare the rates of microbial colonization on nickel-titanium (NiTi) closed-coil springs and active tie-backs used for orthodontic space closure in the maxillary premolar extraction site.

Materials and methods: Thirty-two participants, including 14 males and 18 females, were enrolled in the present split-mouth study. In Group I, NiTi closed-coil springs (Nitinol, 3M Unitek) were used, while in Group II, active tie-backs [stainless steel ligature wire (0.009') threaded through an elastic module (3M Unitek) were used. After a period of 3 weeks, the NiTi closed-coil springs and active tie-backs were carefully removed and transferred to brain heart infusion broth (BHI Broth). The BHI broth samples were then incubated and inoculated into different media, followed by sub-culturing with various specific media. The colony-forming unit per millilitre were measured using a colony counter (HiMedia Laboratories Private Limited, Mumbai, Maharashtra, India). Finally, the various isolated colonies were submitted for phenotypic characterization using BIOMÉRIEUX VITEK^® MS, an automated mass spectrometry microbial identification system based on proteomics-based detection.

Results: The observations made in the study suggested an increased number of microbial colonies in the NiTi closed-coil spring group (46437.50 ± 11848.34 CFU/mL) compared to the active tie-back group (31031.25 ± 8204.97 CFU/mL), with the difference being statistically highly significant (P < 0.000).

Conclusion: Based on the findings of the present study, it can be concluded that using active tie-backs resulted in significantly reduced pathogenic adherence compared to NiTi closed-coil springs. However, further research is necessary to validate these findings before active tie-backs can be recommended as a suitable means for orthodontic space closure, especially in patients with compromised oral hygiene due to any given reason.

Keywords: Active tie-backs; NiTi; closed coil springs; in-vivo study; microbial colonization; orthodontic space closure.

Figure 1

NiTi closed coil springs (Nitinol, 3M Unitek)

Figure 2

(a) Left- Elastic module and (b) Right- Stainless steel ligature wire (0.009’) (3M Unitek)

Figure 3

NiTi closed coil spring and active tie-back placed in the patient’s mouth during retraction (a) Upper- Right lateral view revealing the NiTi closed coil spring, (b) Middle- Left lateral view revealing the active tie-back, and (c) Lower- Frontal view of the patient

Figure 4

Samples collected in brain heart infusion broth (Sisco Research Laboratories Private Limited, Mumbai, Maharashtra, India)

Figure 5

Bacterial colonies as observed in: (a) Upper- blood agar, (b) Middle- chocolate agar, and (c) Lower- Mitis Salivarius agar

Figure 6

Gram staining (×100) revealing: (a) Upper- Gram-positive bacteria and (b) Lower- Gram-negative bacteria

Figure 7

(a) Left- Colony-forming unit per millilitre (CFU/mL) being measured with the help of a Colony Counter (HiMedia Laboratories Private Limited, Mumbai, Maharashtra, India) (b) Right- BIOMÉRIEUX VITEK^® MS, an automated mass spectrometry microbial identification system that uses matrix-assisted laser desorption ionization time-of-flight technology for bacterial identification using proteomics-based detection