Today, it has generally been accepted that effective and physiologic treatment of malocclusion is possible by using gentle and constant forces in orthodontics. Various methods are available for producing this force in orthodontics, namely coil springs, loop archwires, elastomeric chains, and magnets.¹ First introduced in the 20^th century in orthodontics, elastomeric chains are the most popular method for space closure. Low costs, ease of use, and comfort for both patients and clinicians are among the advantages of this method.² Due to variations in these elastomeric chains and differences in force degradation in each chain in different environments, coming up with the most efficient chain in orthodontic treatments is of utmost importance.³,⁴ Elastomeric chains are employed in a significant number of places, such as diastema closure, midline treatment, canine retraction, and tooth rotation treatments.²,³,⁴,⁵ Although the main feature of these chains is retrieving the original length after force application, different in vivo and in vitro studies have shown that force degradation happens to these chains after applying the force.⁶,⁷,⁸,⁹ Despite their extensive clinical use, elastomeric chains are prone to certain limitations: limited water and saliva absorption, irreversible color change, and breakage of internal links, which leads to permanent deformation. Thus, force degradation in elastomeric chains is affected by several factors, such as design; manufacturing technique; color; and mouth environment conditions.³,¹⁰ Nearly 50%–70% of orthodontic primary force loss happens in the first 24 h, and that is due to oral exposure, enzymes of saliva, oral hygiene, and mastication.¹¹,¹²,¹³

The sensitivity to the changes in the oral environment due to various food, beverages, and mouthwashes is one of the major causes of plastic deformation and force loss in elastomeric chains.¹⁴ Under normal circumstances and disease-free conditions, PH alterations, fluoride ions, components of saliva, alterations in temperature, and oxygen level can affect force decay in orthodontic chains.¹¹,¹⁴ Mouthwashes are extensively prescribed for patients undergoing orthodontic treatments. The ones containing fluoride are done to inhibit tooth decay, demineralization of enamel, and reduction of tooth sensitivity. Chlorhexidine (CHX), although prescribed more often, has side effects such as color change and taste confusion. Nowadays, herbal and alcohol-free mouthwashes such as green tea, persica, Punica granatum, cinnamon, and Aloe vera have become common and they are replacing the ones containing alcohol.¹⁵,¹⁶,¹⁷ This research was done to investigate the importance and vast application of elastomeric chains in orthodontics and the effects of mouthwashes on force degradation. No comprehensive and systematic study has elaborated on the impact of various types of mouthwash on the elastomeric chains. The current research aims to improve the clinical function of elastomeric chains in orthodontics, reduce force degradation in them, and help orthodontists choose a precise and efficient method.

Information sources and search

This study had a systematic review of articles published on primary electronic databases of PubMed, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus. For doing so, specific medical subject headings were used, including elasticity, elastomers, orthodontic appliances, dental materials/chemistry, mouthwashes, tensile strength, time factors, and stress mechanical. The mentioned keywords were combined with “and” and “or” in the time range of January 1, 1990 − December 31, 2020. Furthermore, for a broad search, the reference list of all articles and related reports was analyzed.

Protocol and registration

This review article was then issued the code of ethics. IR.GUMS.REC.1399.442

Data collection and interpretation were modeled on Preferred Reporting Items for Systematic Reviews and Meta-Analyses.¹⁸

Study selection

After gathering the data, the articles had matching titles and abstracts – and, if necessary, the full text – with the inclusion criteria entered the study.

Based on PICOs.

The inclusion criteria were designed as follows:

Population: Orthodontic elastomeric chains required for space closure

The exclusion criteria

Based on those mentioned earlier, in vitro articles entered the study; abstracts, animal and review articles, case reports, case series, and discussions were excluded. Recurrent papers were omitted using END-NOTE X8 software (Thompson Reuter, CA, USA), and to prevent bias in search protocols, exclusion criteria were applied after the primary analysis. For identifying and detecting all the related articles, even those with only their abstract in English were included.

Search and extraction of data were carried out by two separate researchers. The researchers evaluated the titles and abstracts and in case of approval, the full texts were analyzed.

Data extraction

The extraction of data and assessment of validity were performed by two expert reviewers independently.

As the first step, one of the researchers extracted some data, including title, authors, type and year of study; sample size; type of mouthwash; kind of elastomeric chain; and results. Moreover, then, the second researcher carried out a second analysis; in case of divergence, the subject was discussed for the final decision.

Moreover, then all information is checked by a third expert reviewer. The process of assessing validity followed a previously established checklist.

Risk of bias assessment

Quality analysis of in vitro studies regarding dental material was done based on Faggion¹⁹ using a modified CONSORT checklist, parameters of which are shown in Table 1. Based on being reported or not reported, each one got a “yes” or “no,” and finally, the score for each article was calculated, and the final results were reported as a mean percentage of all articles. The authors examined the articles' quality separately, and in case of discrepancy, the final decision was made through negotiation.{Table 1}

Study selection

Altogether, 414 articles were found on electronic databases and also by manual searching Figure 1. After omitting duplicate articles and initial review, the full text of 15 surveys entered the final study. In the end, 14 in vitro articles had the inclusion criteria for this systematic review Table 2.Figure 1

The PRISMA flow diagram. PRISMA: Preferred Reporting Items for Systematic Review and Meta-Analyses.

This systematic review focuses on force degradation in orthodontic elastomeric chains caused by different mouthwashes.

Fourteen RCT articles were covered in this study, all of which measured the effects of mouthwashes on the force loss in elastomeric chains. Among them, three papers were on mouthwashes containing alcohol,¹⁶,²²,²⁴ 5 articles investigated the effects of fluoride mouthwash,⁵,⁶,¹⁵,²⁰,²¹ 4 articles used CHX mouthwash,¹⁵,²¹,²³,²⁴,²⁷ 3 studies had mouthwashes with bleaching agents,⁶,²⁰,²⁶ and in 5 articles Listerine mouthwashes were studied.¹⁶,²²,²³,²⁴,²⁵,²⁶

The measurement of the force degradation in elastomers caused by mouthwashes in all articles was measured in four intervals: the 1^st day, the 1^st week, the 3^rd week, and the 4^th week. Orthodontic elastics are the essential sources of force transmission to the teeth, which, ideally speaking, are expected to have minimal force loss on activation and to apply force continuously throughout the treatment. As the results of the reviewed articles revealed, however, the case was not so. Various investigations performed by different authors at different times unanimously showed that force transfer did not proceed according to the ideal assumptions. Because of various mechanical and environmental factors, force loss would occur right from the beginning. One study claimed the maximum rate of force loss in the early hours was 50% to 70%, which would continue in a downward trend for 3–4 weeks.²¹ Another research estimated the loss to be 40%−50% in the first 24 h.²⁹,³⁰,³¹

Ramachandraiah et al.,²² however, claimed that mouthwashes containing alcohol with a concentration of 21.6% showed the highest force dissipation (55.18%) among other mouthwashes after 24 h, but in Menon et al.'s,²⁴ mouthwashes had an alcohol concentration of 26.9% and they showed the highest rate of force loss (49.48%) among other types. In the Larrabee et al.'s study,¹⁶ 24 h after using Listerine mouthwash, 53% of the force was lost. In the clinical conditions, if the rate of force degradation was high in the first 24 h, it would increase the patient's comfort, but on the other hand, it would cause a tissue response to the effect of tooth movement.

A proven factor affecting the initial load force loss is a humid environment compared to a dry one. Most force loss occurs in the early hours, but it has been shown that this degradation rate is higher in humid environments than in dry ones.⁸ Therefore, in elastomeric studies, chains are immersed in the artificial saliva throughout the experiment, and it was placed in the mouthwash only at the determined time during the day. It is shown that a higher initial load causes a greater force to be lost. All elastomers used in the reviewed articles for this systematic review were under prestretch conditions except Ramachandraiah et al.,²² which examined elastomeric chains under prestretch and unstretched conditions. Their study showed that force decay in unstretched elastomeric chains was higher than prestretch ones. Another influential factor in force degradation is the ambient temperature, so in all articles studied, the temperature was set at 37 ± 1°C, matching the oral cavity and body temperature. The results of a study by Dadgar et al.,²⁰ who conducted their study on two types, memory chain and conventional chain, showed that in the first 24 h, the latter loses more force than the former, while memory chain had higher force stability during the first few days, but at the end of 4^th week, no statistically significant difference was observed between the two regarding the force loss. Mirhashemi et al.⁴ also confirmed the same results. However, they found a statistically significant difference in the 4^th week since the conventional chain retained only 40% of the initial force, but regarding the memory chain, that number was 60%. One of the critical factors in the rate of force loss is the environment of different mouthwashes. The amount and concentration of soluble substances in mouthwashes have secondary effects on the oral mucosa and dental tissues diet, bioflora and its biproducts can influence on elastomeric chains materials.³² CHX mouthwash, besides its antibacterial and anti-plaque effect, causes the color change of teeth and oral mucosal ulcers.²² Pithon et al., which examined their effects on elastomeric chains, showed that CHX 0.2% compared to CHX 0.12% caused less force degradation in the chains during 4 weeks, but this amount was not statistically significant. They also observed that the highest rate of force loss in the chains happens in the first 3–5 h.²⁷ Omidkhoda et al. announced that the highest loss occurred in CHX mouthwash, followed by NaF, while the lowest rate was observed in Persica mouthwash. The reason for the highest force degradation in CHX mouthwash can be attributed to its ethanol composition (13.65%).¹⁵ Ramazanzadeh et al. and Javanmardi and Salehi showed that the pattern of force decay in elastomers with the presence of mouthwashes would not change compared to the control group.⁵,⁷ Pithon et al. had reported a similar result for mouthwashes with bleach.²⁶ Javanmardi and Salehi and Pithon et al. stated that the chains were removed from the pins five times for force measurements and transferred to a dry medium.⁷,²⁶ However, this matter would not occur in clinical conditions, so their results can be attributed to the limitations of these articles regarding the environmental changes of elastomeric chains. However, Behnaz et al. showed whitening mouthwashes with the active ingredient hydrogen peroxide, which would change the teeth' optical properties and react with organic molecules and increase the rate of force loss compared to NaF mouthwashes.⁶

On the other hand, Oshagh et al., Omidkhoda et al., and Dadgar et al. reported a tremendous force loss in elastomeric chains in the NaF mouthwash environment.¹⁵,²⁰,²¹ The difference in the results of these studies could be related to different brands of chains.

Ramachandraiah et al., who studied mouthwashes with different concentrations of alcohol, concluded that mouthwashes containing alcohol cause structural and molecular changes in elastomeric chains that can increase the rate of force degradation in them.²² Larrabe et al., who made a similar comparison, showed that alcohol-based mouthwashes increased the rate of force loss in chains and reported the difference to be statistically meaningful.¹⁶ Santana et al. and Mahajan et al. investigated the effect of alcohol-free mouthwashes and alcohol-based ones on force degradation. They showed that alcohol (ethanol) in mouthwashes with the chemical structure CH3-CH2-OH bonds with polyurethane polymer in the chain structure, and thus alcohol-based mouthwashes cause more force loss than alcohol-free mouthwashes.²³,²⁸ Menon et al., who compared the effects of 26.9% alcohol NaF, CHX, and Listerine mouthwashes on the force decay of the chains, observed a statistically significant difference among them. Because of the alcohol it contained, Listerine mouthwash caused the highest force degradation due to hydrolysis of elastomeric chains, and the lowest rate was observed in CHX mouthwash.²⁴ Ramazanzadeh et al., who studied the effects of fluoride mouthwash regarding the mentioned loss, did not find fluoride mouthwashes to cause force degradation in elastomeric chains.⁵ Thus, it can be concluded that they can safely be used for reducing the prevalence of caries, especially in patients undergoing orthodontic treatments since they are more prone to primary caries lesions and whitespots around the brackets.

Elastomeric chains provide the force needed for the tooth movement in orthodontic treatments. However, this force does not remain constant until the end of the said treatment and is influenced by environmental and mechanical factors. Regardless of other influential factors, mouthwashes are among the most critical contributors to force loss in chains. However, on the other hand, they are influencing the forces in decreasing the prevalence of dental caries and periodontal disease in patients undergoing orthodontic treatment. According to the research results reviewed in this systematic review, it is recommended to use fluoride-containing mouthwashes in orthodontic patients, which cause less force decay in the elastomeric chains than other types. It is also suggested to consider alcohol-free CHX mouthwashes in treating periodontal diseases of patients undergoing orthodontic treatments. However, patients should be aware of the complications of CHX. The results also showed that alcohol mouthwashes cause significant force loss, so the recommendation is to replace them with alcohol-free types as much as possible.

Although based on the explanation in the data extraction part, all of the selected articles have got problem in sampling and randomization. We just tried to review the result of selected articles. According to the results of this review, the development of the feature research is reasonable.

Acknowledgment

We would like to express our special thanks for Student Research Committee of Gilan University of Medical Sciences, Rasht, Iran.

This article is based on the research proposal with ethical code. IR.GUMS.REC.1399.442

Financial support and sponsorship

Nil.

Conflicts of interest

The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or nonfinancial in this article.