# Do Oral Antiseptics Affect the Force Degradation of Elastomeric Chains?
## 4 Discussion  
Elastomeric chains, because of their elastic characteristics [19], are susceptible to environmental influences in the oral cavity: they absorb water, saliva, pigments, and dyes. The current study was performed to compare the force degradation of five different brands of elastomeric chains after exposing them to four different commonly used mouth rinse brands. In the present study, elastomeric chains were firstly activated on their double length, then exposed to thermocycling, followed by immersion in the various mouthrinses through a total number of three cycles simulating a duration of 30 days. All investigated brands of chains experienced statistically significant force decay after the aforementioned procedures. Initial rapid force decay that occurs in the first investigated period is explained by two factors. The first is stress relaxation caused by stretching of the material [22; 23]. This is due to the viscoelastic properties of the elastomer causing the material would relax when experiencing constant stress beyond its stress relaxation time, whereby the deformation becomes permanent and thus reduces the delivery force. On a molecular level, stretching represents the stress for the polymer, causing breakage of primary bonds, sliding of polymer molecules and, consequently, permanent deformation of the material [23]. Another factor influencing force decay is water absorption during thermocycling and immersion in different solutions [22]. Polyurethane materials absorb water molecules which fill up the spaces in the rubber matrix resulting in swelling of the material and hydrolysis. This consequently leads to fissures in the microstructure with a breakdown in the polymer-polymer interactions [23; 24; 25]. Hence, water molecules act as plasticizers. They increase chain flexibility and reduce the brittleness of the material. Therefore, the force delivered by chains is decreased. The greatest force decay was observed after the first phase of thermocycling or after 10 days of simulated usage. This was expected since it is a well-known fact that the highest force decay occurs during the first hour or the first 24 h, then progresses in a steadier way, which was proved by a great number of studies [26; 27; 28; 29; 30]. Of all investigated brands, Forestadent chains were most susceptible to accelerated aging. Force decay in this brand was statistically significantly greater than in RMO and Ormco chains. According to [PERSON] et al., 100 cN is considered to be the lower limit for physiologically acceptable tooth movement [31]. At the end of the experiment, all elastomeric chains except Forestadent had final force values which were above 200 cN. Forestadent chains immersed in all investigated mouthrinses, excluding the control, had residual force values below 100 cN. However, according to other authors, residual force delivered by Forestadent chains in combination with various mouthrinses would still be high enough to produce all types of orthodontic tooth movement [32; 33]. All investigated elastomeric chains were closed connector chains. The effect of distance between links on force decay was investigated in previous studies [31]. Some of them found that chains with less distance between modules produced higher initial force and underwent lower force loss [34]. However, others concluded the opposite [26]. Hence, future studies are needed to evaluate the influence of length between modules on force decay. Subgroups of elastomeric memory chains in this study showed more steady force residue compared to conventional elastomeric chains, which is in accordance with [PERSON] et al., whose results showed that memory chains provide greater forces for longer durations over conventional ones [35]. Immersion in chosen mouthrinses by our results showed an overall greater loss of force for each elastomeric chain brand compared to the control group, but only statistically significant in Forestadent EOC in Listerine.