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Indian Journal of Dental Research

: 2015  |  Volume : 26  |  Issue : 2  |  Page : 180--185

"Comparative evaluation of surface modified elastomeric ligatures for microbial colonization": An in vivo study

M Pavithra Bai, Anna Cecilia Vaz 
 Department of Orthodontics and Dentofacial Orthopedics, P.M.N.M Dental College and Hospital, Bagalkot, Karnataka, India

Correspondence Address:
Dr. Anna Cecilia Vaz
Department of Orthodontics and Dentofacial Orthopedics, P.M.N.M Dental College and Hospital, Bagalkot, Karnataka


Introduction: Elastomeric ligatures are observed to reduce chair side time; however, they are also seen to have greater bacterial adhesion. Polymeric coating utilizing the Metafasix Technology and the OrthoShield Technology have been introduced in the Super Slick™* and Safe-T-Ties™** by TP Orthodontics, Ortho Organizers, respectively, to reduce bacterial adhesion. While each of the elastomers has been individually evaluated, no study compares the two elastomers manufactured by differing technologies together; hence the need for this study was felt. This in vivo study compared the Super Slick and Safe-T-Ties with their unmodified counterparts for bacterial adhesion. Materials and Methods: Thirty patients undergoing orthodontic treatment, between 12 and 25 years age group were selected and the modified, and the unmodified elastomers were randomly placed quadrant wise, on all the premolar brackets. After a period of 4 weeks, the elastomeric rings were removed and transported for culture on Mitis-Salivarius, Rogosa SL agar for Streptococcus mutans and Lactobacilli, respectively. The colonies were digitally counted (HiMedia) after 48 h of incubation at 37°C. Results: There was a significant difference in the S. mutans and Lactobacilli counts in both surface modified and unmodified elastomeric modules (P < 0.01). Unmodified elastomeric modules Mini Stix™*, Hand-EE-Lasts™** was associated with higher mean values of colony-forming units/millimeter than the surface modified Super Slick™* and Safe-T-Ties™** ligatures. When compared pair-wise, the surface modified elastomers showed less bacterial accumulations than the unmodified counterparts for both S. mutans and Lactobacillus, and the differences were statistically significant. Conclusion: Technological modifications of the elastomers using the Metafasix or OrthoShield Technology, is a definite improvement over the regular elastomers with regard to adhesion of S. mutans and Lactobacilli.

How to cite this article:
Bai M P, Vaz AC. "Comparative evaluation of surface modified elastomeric ligatures for microbial colonization": An in vivo study.Indian J Dent Res 2015;26:180-185

How to cite this URL:
Bai M P, Vaz AC. "Comparative evaluation of surface modified elastomeric ligatures for microbial colonization": An in vivo study. Indian J Dent Res [serial online] 2015 [cited 2023 Oct 4 ];26:180-185
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Full Text

The development of dental plaque has been associated with several factors such as maintenance of oral hygiene, [1] composition of diet, [1],[2] fluoride exposure, [3] the quality of saliva, the composition of the oral micro flora and immune factors. [4],[5] Fixed or removable orthodontic appliances create new retention areas [4] and impede the maintenance of oral hygiene. [5],[6] Decalcification, white spot lesions, caries, and inflammatory periodontal disease are some of the commonly recognized consequences of poor oral hygiene, especially during orthodontic treatment. [7],[8] The prevalence of white spot lesions in patients after orthodontic treatment range from 15% to 85% [9] and some studies report a prevalence of around 50-70%. [10],[11],[12],[13] Decalcification has been shown to occur as early as 4 weeks after bonding. [8]

The method of ligation of orthodontic archwires is one relevant factor that accounts for dental biofilm retention. [4] Clinicians may use 0.008-0.014 inch stainless steel ligature wire, self-ligating springs or circular synthetic elastomers to secure arch wires to brackets. [1],[2],[3],[4] In the search for more practical and efficient orthodontic accessories, elastomeric rings have been suggested as the material of choice to connect stainless steel archwires to brackets instead of metallic ligatures. [4],[14],[15] Apart from its practical advantages, it is evident from the literature review that elastomeric rings exhibit a greater number of micro-organisms in the plaque around the brackets when compared with the steel ligatures. [4],[16]

To reduce the demineralization of the teeth during and postorthodontic treatment, various plaque control measures such as the use of chlorhexidine mouthwashes, varnishes or topical fluoride applications, fluoride releasing composites, cements were advocated. [17] The fluoride releasing elastomeric rings have been reported to reduce dental biofilm formation and improve enamel remineralization in areas adjacent to the bracket base, which is difficult to clean. [18],[19],[20],[21] However, not all researchers concurred with the latter view. [22]

The surface characteristics of the elastomerics have been altered by companies in recent years using the Metafasix technology (Super Slick™*) [23] and the OrthoShield Orthodontic Antimicrobial Technology (Safe-T-Ties™**). [24] These alterations have been claimed to reduce bacterial adhesion. [23],[24],[25],[26] Reports in literature with regards to the efficacy of the Super Slick™* elastomers in reducing microbial adhesion remains controversial. [27] Literature is scarce [28] with regard to the utility of the OrthoShield Technology on elastomers in orthodontics. It was our premise that the improved technological changes in orthodontic elastomers did, in fact, alter the surface characteristics and reduced bacterial adhesion on them. Our null hypothesis, therefore, stated that surface modified elastomers reduced the bacterial adhesion on them, but it made no difference as to which technology was used.

No study to the best of our knowledge was carried out to comparatively evaluate the two elastomers utilizing differing technologies to reduce bacterial adhesion. Hence, this study compared the surface modified Super Slick™*, Safe-T-Ties™** with their unmodified counterparts from the same company, Mini Stix™*, Hand-EE-Lasts™** for bacterial adhesion.

 Materials and Methods

Thirty patients (15 males and 15 females) undergoing orthodontic treatment, aged between 12 and 25 years were randomly selected from the post graduate clinic of the Department of Orthodontics, P.M.N.M Dental College and Hospital, Bagalkot, Karnataka. This research project was approved by the local Ethical Committee (PMNMDCH/1816/2011-12) of the institution. A written consent was received from the patients who were willing to be part of the study from the patients themselves or their parents (or legal representatives).

Patients who were using antimicrobial mouthwashes, or who had any systemic diseases, were pregnant, had used antibiotics 3 months prior to the study, or had brackets bonded with glass ionomer cements were excluded from the study. All patients selected were right handed brushers. They had undergone thorough oral prophylaxis at the start of the study. They were instructed to use a common dentifrice and to brush after each meal.

The investigation was designed as a split-mouth study. Stainless steel 0.022″ slot MBT brackets were bonded in both the arches and 0.016-inch Nitinol Archwire (Ortho Organizers) was placed. In each subject, the elastomers were randomly assigned to premolars. If the modified elastomers, one of each type, were assigned to one quadrant, care was taken to see that the contralateral side received the unmodified elastomers, one of each type. Similarly, if the maxillary arch received the modified elastomers, the mandibular arch of the same side received the unmodified counterparts. This was carried out for a total of 240 ligatures [Figure 1]. Patients were recalled after 4 weeks, the ligatures were aseptically and carefully removed without disturbing the plaque around the brackets. Each elastomeric ligature with the adhered plaque was individually transported in a vial containing 10 ml of thioglycolate medium to which Hemin and Vitamin K (1:1000 dilutions) were added [Figure 2] to be inoculated on media for culture of Streptococcus mutans and Lactobacilli.{Figure 1}{Figure 2}

The samples were inoculated on Mitis-Salivarius agar to estimate the colonization of S. mutans. A decimal dilution of the specimen was prepared, and 0.01ml in amount was spread by a platinum loop over the surface of the complete medium. The plates were then incubated in CO 2 jar at 37°C for 24 h with 5-10% CO 2 . One percent potassium tellurite solution was added to make the medium highly selective for S. mutans. Cultural characteristics appeared after 18-48 h at 37°C. Plates were removed from the jar, growth noted, and organisms identified by Gram staining. To estimate Lactobacilli, the samples were inoculated on Rogosa SL agar, which is highly selective for oral Lactobacilli. A decimal dilution of the specimen was prepared, and 0.01 ml in amount was spread by a platinum loop over the surface of the complete medium. The plate was incubated at 37°C for 48 h at 5% CO 2 in a vacuum anaerobic jar. Cultural characteristics appeared after 40-48 h at 37°C. Plates were removed from the jar, growth noted, and organisms identified by Gram staining [Figure 3].{Figure 3}

The number of colonies was counted with a digital colony counter (HiMedia). The results were expressed as colony-forming units per millimeter (CFU/ml × 10 3 ) and tabulated. All the microbiologic procedures were performed by an investigator who was blinded to the type of elastomeric ring being investigated.

Statistical analysis

A pilot study was conducted in first two groups by taking a convenience sample of 3 each; CFU counts were recorded. Based on the pilot study (alpha error = 5%, power of test = 90%), the sample size was estimated to 60 in each group, totaling 240 ligatures (60 × 4 = 240).

The normal distribution of the data was estimated to be a skewed distribution in all the four groups as calculated from the Shapiro-Wilk W-test (Group 1: W = 0.93518, P < 0.00416; Group 2: W = 0.86058, P < 0.00001; Group 3: W = 0.91862, P < 0.0005; Group 4: W = 0.94109, P < 0.0100).

The data obtained from the study was subjected to statistical analysis using SPSS software (IBM® SPSS® Advanced Statistics version 20.0). All bacterial counts were considered at 10 3 CFU/ml for ease of statistical calculations.

Descriptive statistics

The mean and standard deviation was calculated for each type of elastomers.

Comparison of each type of elastomer with respect to the bacterial count of S. mutans and Lactobacilli was analyzed nonparametrically using Kruskal-Wallis (H) one-way ANOVA testPair-wise comparisons of the same were done by the Mann-Whitney U-test.

Significance for all statistical tests was predetermined at P ≤ 0.05. The researcher was blinded to the type of elastomeric ring when analyzing the data.


The mean and standard deviation of bacterial counts in 10 3 CFU/ml on the four types of elastomers is tabulated in [Table 1] for both S. mutans and Lactobacilli. Analysis of the data revealed the unmodified elastomeric modules Mini Stix™*, Hand-EE-last™** to be associated with higher mean values of CFU/ml than the surface modified ligature modules Super Slick™*, Safe-T-Ties™** as illustrated in [Table 1]. Kruskal-Wallis, one-way ANOVA test when applied to the data showed the difference to be statistically significant for S. mutans [Table 2] and Lactobacillus [Table 3] (P < 0.05). When the number of CFU's of S. mutans was compared with that of Lactobacillus, it was noted that the number of CFU's in S. mutans was higher than those of Lactobacillus in both surface-modified and unmodified elastomeric modules [Figure 4]. The micro-organisms on the surface modified Safe-T-Tie™ ** utilizing the OrthoShield antimicrobial technology were seen to be the least while the micro-organisms on the Mini Stix™ * were seen to be the highest both for S. mutans as well as for Lactobacillus [Table 1].{Figure 4}{Table 1}{Table 2}{Table 3}

Pair-wise comparison using Mann-Whitney U-test carried out between the same company elastomers showed the pairs to have statistically significant differences (P < 0.05) with the surface modified elastomers having less bacterial accumulations than the unmodified elastomers for both S. mutans [Table 4] and Lactobacillus [Table 5]. When the pairs of different companies were compared, the unmodified elastomers showed more bacterial adhesions than the surface modified elastomers, and these differences were statistically significant. The CFUs on Safe-T-Ties™** were the least, lower than that of Super Slick™* however, the difference between them was not statistically significant. Hand-EE-last™** showed statistically significant difference with Mini Stix™*.{Table 4}{Table 5}


Plaque is the major etiological factor in the development of dental caries. The control of plaque is fundamental in the control of caries and periodontitis. It has been reported that Lactobacilli and Streptococci species create a low pH oral environment (pH < 5.5) due to the bacterial byproducts. [29] S. mutans is strongly associated with the initiation of dental caries, [30] and Lactobacilli has long been associated with caries development. [31] Therefore, determination of both the S. mutans and the Lactobacilli counts was considered important to determine caries risk in this study. This study showed the streptococcal counts to be higher than that of Lactobacillus during the 4-week period of study. As Streptococcus is strongly associated with the initiation of dental caries, it is postulated that the risk of demineralization is high.

The material used for ligation of orthodontic archwires alters the bacterial colonization in the areas adjacent to the brackets. [4],[10],[16],[17],[32] Forsberg et al. [4] found that most patients had a higher bacterial count on teeth ligated with conventional elastomers than on teeth ligated with steel ligatures. On the other hand, Türkkahraman et al. [17] and Sukontapatipark et al. [32] found no significant differences (P > 0.05) between the two materials when evaluated for microbial colonization.

Elastomeric ligatures with modified surface characteristics that are claimed to control bacterial development on their surfaces have been introduced in recent years. [23],[24],[25] These elastomeric modules are produced by different technologies, the Metafasix technology [23] and the OrthoShield Orthodontic Antimicrobial Technology. [24] The Metafasix technology™* uses a water-insoluble, hydrogel-polymer coating which transforms the polyurethane-based elastomeric surface, when moistened, into a highly smooth surface which, as claimed by the company, reduces bacterial adhesion. [24] On the other hand, OrthoShield Orthodontic Antimicrobial Technology™** makes use of the antimicrobial characteristics of naturally occurring silver; silver has an ability to destabilize the bacterial cell wall, interrupt cell metabolism and inhibit reproduction. The silver is embedded in a porous ceramic that controls the silver's release to the surface of the elastomeric ring thus providing a durable antimicrobial solution for a period of 30 days. [24],[25]

This study investigated the microbial colonization on the surface modified elastomers; Super Slick™*, Safe-T-Ties™** along with the unmodified Mini Stix™*, Hand-EE-last™** for both S. mutans and Lactobacilli. From the results of this study, it is evident that the plaque around the brackets ligated with unmodified elastomeric ligatures contained higher number of bacterial colonies with respect to both S. mutans and Lactobacilli when compared with the surface modified Super Slick™*, Safe-T-Tie™** elastomers. This indicated that surface modification of the elastomers, both by Metafasix technology and the OrthoShield Orthodontic Antimicrobial Technology, reduces the accumulation of bacteria on the elastomers. Safe-T-Tie™** showed lower bacterial counts than Super Slick™*, both for S. mutans and Lactobacillus, however, the differences were not statistically significant (P > 0.05), thus indicating that both surface-modified elastomeric modules irrespective of technology used to modify its surface, reduces bacterial adhesion.

This study contradicts the lone study of Magno et al. [27] on the Super Slick™* and the lone study of Kim, et al. [28] on the Silver ion releasing elastomers Safe-T-Ties™**. Magno et al. [27] showed statistically higher number of S. mutans on Coated Super Slick ties™* when compared to conventional elastomers. However, the dissimilarities in study design, type and period of evaluation, scoring system, type of microbiological test, and host resistant factors in the patient population could be responsible for the differences seen in the results of our study with that of Magno et al. [27] and that of Kim, et al. [28] Clinically, Corbette, [26] has reported an observation when he used the Safe-T-Ties. There has been no study comparing the different technologies together to the best of our knowledge and hence direct comparison with similar studies is difficult.

Surface modification by coating the elastomers using the Metafasix Technology [23] or using the AgION Antimicrobial Technology [24] could thus be a useful technological advancement. This study supports our premise and favoured our null hypothesis. The surface modification reduces the colonization of micro-organisms: S. mutans and Lactobacillus, related to both caries initiation and progression.

Limitations of this study

This study evaluated the adherence of two micro-organisms to the elastomeric ligatures namely S. mutans and Lactobaccillus. Periodontal pathogens such as Actinobacillus actinomycetemcomitans and Tannerella forsythia have also been significantly associated with gingival inflammation during orthodontic therapy however, including these micro-organisms was beyond the scope of this study. [16] As furtherance to this study, the microbial spectrum could be widened.

This study estimated the bacterial adhesion on the respective ligatures. Estimation of altered microflora in and around the environment of the ligature is a limitation in this study and could be pursued utilizing improved technologies, DNA isolation, and polymerase chain reactions.


Contemporary surface modified elastomeric ligatures show superior qualities with respect to bacterial adhesion when compared with their unmodified counterparts. Technological modifications of the elastomers using the Metafasix* or OrthoShield** Technology is a definite improvement over the regular elastomers with regard to adhesion of Streptococuus mutans and Lactobacilli.

End notes: ™* - TP Orthodontics; ™** - Ortho Organisers.


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