# The Influence of Different Cleaning Protocols on the Surface Roughness of Orthodontic Retainers
## 1 Introduction
Citric acid in a cleaning tablet, for example, reacts with sodium bicarbonate to form washing soda, which is an excellent agent for removing biofilm from material surfaces. Alkaline peroxide-based commercial cleansing tablets are thus the most commonly recommended agents today. There is no evidence that these cleaning procedures affect the surface roughness of TORs. Many previous studies claim that brushing with or without toothpaste affects structural properties of various dental materials by creating macro and microscopic irregularities on the surface and thus consequently increasing surface roughness [7; 13; 14; 15]. The final effect on material roughness depends on the applied load and brushing duration. Even though toothpushing affects surface roughness, it is still the most commonly recommended method for maintaining the hygiene of retainers [16]. Polypropylene and polyethylene materials are now widely used in the production of orthodontic retainers. Recent research indicates that copolyester- and polyurethane-based retainers are becoming increasingly popular due to their clear and thin surfaces [17; 18] and efficacy in maintaining incisor position and alignment [19]. The physical surface of a target material is important when it comes to bacterial adhesion because it contains a variety of influential factors [20; 21], such as surface charge [22], surface hydrophobicity [23], and surface roughness (in terms of bacterial colonization) [24]. Orthodontics and prosthodonics have seen an increase in the use of daily, ready-to-use cleaning tablets. Cleaning tablets were found to be more effective than controls at reducing bacteria adherence to thermoplastic sheets in an in vitro study published in 2019 [25]. However, a randomized clinical trial found no significant difference in the bacterial count when Essix(r) was cleaned with various cleansing tablets versus mechanical cleaning [8]. Several researchers have attempted to use vinegar as a cleaning chemical agent for orthodontic appliances due to its low cost, ease of access, and antibacterial properties [26; 27]. However, the optimal vinegar concentration for retainer cleaning has yet to be determined. The modes of action and usage directions of vinegar solutions differ, emphasizing the need for additional research [28]. Copolyesters and polyurethane are becoming more widely used in orthodontics due to their hydrolyzable ester bonds, which contribute to potential biodegradability [29; 30; 31]. Furthermore, copolyester contains molecules that are susceptible to microbial attack, such as aliphatic polyester and terephthalic acid [31]. The aliphatic polyester is broken down in two steps: depolymerization (or surface erosion) and enzymatic hydrolysis, which produces water-soluble intermediates that microorganisms can use [32]. Previous research has shown that polyethylene materialshave superior esthetic and mechanical properties to polypropylene materials [33; 34]. By searching the internet, it is possible to find various instructions and guidelines referring to the maintenance of retainer hygiene. These instructions and guidelines are commonly not unanimous and can confuse patients. Patients are instructed to keep their retainers clean, so the aim of this study was to determine the influence of different cleaning protocols on the surface roughness of orthodontic retainers.