# The Effects of Activated Carbon Toothpastes on Orthodontic Elastomeric Chains--An In Vitro Study
## 1 Introduction  
Elastomeric chains (ECs) are amorphous polyurethane-based polymers that exhibit the properties of both rubber and plastic, both of which account for their elasticity [1]. The form, colour, shape memory, flexibility, low cost, and ease of handling of ECs have resulted in their extensive incorporation into orthodontic practice in recent decades [2; 3]. However, despite the favourable characteristics of ECs, their ageing pattern and mechanical efficiency are marked by a quick onset of intra-oral maturation, leading to a loss in strength of 50-75% over time [4; 5], causing alterations in the force they apply to teeth from a continuous pattern to an interrupted form [3]. It is generally recognized that a fixed orthodontic apparatus offers favourable sites for microorganism colonization and plaque retention, which might cause enamel demineralization and periodontal disease [3; 6]. ECs, specifically, might enhance bacterial plaque colonization due to their latex component's rough surface and absorption characteristics [7]. Therefore, it is recommended that a customized oral hygiene care protocol be implemented, including brushing teeth with effective toothpaste and use of mouthwashes [7]. Numerous types of toothpaste have been developed and introduced onto the market. Nearly all contemporary toothpaste includes essential elements such as thickening agents, flavour, surfactants, water and specific agents that benefit consumer needs. These benefits include whitening teeth, improving gingival care, reducing tooth sensitivity, freshening breath and increasing enamel resistance to the risk of caries [8,9]. There has been an increase in both the demand for and supply of whitening toothpaste containing activated carbon [8,9]. This abrasive component removes and prevents the formation of external enamel pigments but can be excessively abrasive due to the particles' size [10,11]. Throughout fixed orthodontic treatment, tooth enamel is frequently more susceptible to stains, leading patients to use whitening instead of conventional toothpaste to regain tooth brightness. Dental plaque and discolouration are removed from teeth through a three-component scheme consisting of the toothbrush bristles, enamel tooth surface and the activated carbon abrasive particles in between [12,13]. The mechanical action of brushing bonded teeth wearing auxiliary ECs might increase the decay of the ECs' tensile strength, compromising orthodontic treatment [14]. Other local considerations might exacerbate the impact of toothpaste, such as the number and shape of toothbrush bristles, as well as the frequency of brushing and brushing technique [15,16]. Numerous investigations confirmed that active carbon toothpaste is highly absorbent and can exchange ions across nanopores, adhere to enamel and remove stains by absorbing pigments from the tooth enamel surface [15,16,17,18,19]. A search of the published literature found only two studies exploring the impact of activated carbon on ECs [5,14]. [PERSON] et al. [14] concluded that toothpaste with whitening agents significantly reduces EC tensile strength compared to non-whitening toothpaste. However, their investigation used only one type of EC (3M Unitek(r), 3M Unitek Corporation, Monrovia, CA, USA). In another study, [PERSON] et al. [5] observed a similar degrading effect of two of the most widely used whitening mouthwashes (Plux and Listerine) on an EC manufactured by Morelli (Sorocaba, Brazil). Furthermore, according to our search, none of the studies investigated the impact of activated carbon toothpaste on the EC rupture point or colour stability. Therefore, this study aimed to evaluate the effect of toothpaste containing activated carbon on the force degradation of different brands of orthodontic ECs. A further aim was to evaluate the effect of these whitening toothpastes on the EC rupture point and their colour stability. Within this context, the following null hypotheses were tested:  
1.