# The Influence of Different Cleaning Protocols on the Surface Roughness of Orthodontic Retainers
## 1 Introduction  
Ensuring the stability of orthodontic treatment results represents a great challenge for every orthodontist. After the completion of active orthodontic treatment, changes in tooth position may occur due to occlusal-, periodontal-, or growth-related factors [1]. In order to prevent relapse and unwanted tooth movement, orthodontic retention with fixed or removable retainers is required [2]. Wearing full-time retainers is, unquestionably, important, as maintaining the final orthodontic outcome is one of the most important goals after treatment completion. Given that retainers fail in approximately 70% of orthodontic treatments, they should be worn consistently [3]. After Sheridan introduced the Essix retainer in 1993, it became the most widely used type of retention because it was comfortable and almost invisible. The vacuum-formed retainer (VFR) is one of the most common types of orthodontic retainer, and patients prefer it over Hawley retainers because of its excellent esthetic characteristics, ease of use, superior formability, maintenance of good oral hygiene, and lack of discomfort. Thermoplastic vacuum-formed retainers are fabricated from polyethylene, polyurethane, and polypropylene, meaning they are prone to morphological and physical changes [4]. However, from a clinical standpoint, VFRs have significant limitations due to their material properties. The forming procedure, because of heating, might cause some changes to the mechanical properties of the material [5]. Furthermore, during intraoral use, mechanical and chemical degradation of the material has been noticed. Thermoplastic materials are sensitive to humidity, temperature variations, enzyme activities, and cyclic pressure/loading. All these factors can cause changes to the mechanical properties of the material [6]. Furthermore, there has been a lot of research conducted on bacterial colonization of retainers and bacterial eradication protocols, butnot on the impact of these same protocols on the mechanical and chemical properties of retainers. Any change in the chemical composition and mechanical properties of the material could have a significant impact on the form and function of the retainer. There are no uniform guidelines for keeping thermoplastic orthodontic retainers clean. Brushing is one of the most widely accepted methods of cleaning removable appliances, according to the Dental Professional Recommendation, even though brushing alone, with or without toothpaste, can still increase surface roughness [7]. However, [PERSON] et al. [6] reported that mechanical brushing itself has no effect when compared to its chemical counterpart. Numerous studies have been conducted to date on the accumulation of microorganisms (such as _Streptococcus_ spp., _Staphylococcus_ spp., _Enterobacteriaceae_, and _Candida_ spp.) on removable orthodontic devices [8; 9; 10; 11]. A 2019 study [11] investigated the effect of three different cleaning methods (peroxide-based cleanser tablets + brushing, control (only brushing), and vinegar + brushing) on the _Streptococcus mutans_ and Lactobacillus. Bacteria counts were determined, indicating that mechanical cleaning alone was insufficient to maintain the hygiene of clear vacuum-formed retainers. The majority of OCC products contain alkalizing agents, such as sulfate or carbonate groups, which aid in pH buffering. It is possible that differences in the effectiveness of appliance plaque removal by different chemical methods are due to their different mechanisms of action. One of the most commonly used active ingredients in cleaning tablets is sodium perborate. In a saturated aqueous solution, this ingredient buffers H\({}_{2}\)O\({}_{2}\) to a pH of about 10. Oxygen is liberated during the oxidation of H\({}_{2}\)O\({}_{2}\). Evolved O\({}_{2}\) appears to be associated with the effervescing action of cleaner solutions, which is thought to have a mechanical cleaning effect [12].