# Factors Influencing Appliance Wearing Time during Orthodontic Treatments: A Literature Review
## 4 Results and Discussion
### \"Appliance-Related\" Factors  
Orthodontic treatment certainly improves both dental and facial appearances, but there are annoying and uncomfortable side effects that may lead to a decrease in patients' compliance [19; 20]. This regards therapies with both fixed and removable appliances on aesthetic and functional levels. For example, fixed appliances are associated with poor aesthetics (such as metallic brackets), and they are therefore less accepted than more aesthetic solutions [19]. These types of appliances can be a source of pain and discomfort, but patients cannot remove them. In the case of fixed appliances, a decrease in cooperation is usually associated with oral hygiene and with the use of additional auxiliaries such as elastics and headgear [20; 32]. Removable appliances are generally considered more comfortable, as, in rare cases of pain or discomfort, patients may remove them. Unfortunately, studies show that removable appliances are worn less than required [45]. Some reports show that compliance with removable appliances is suboptimal: patients wear the appliances five hours less than indicated by the clinician [2]. Pain, discomfort, and functional restrictions that are caused by orthodontic appliances seem to be the most annoying side effects of the treatment. According to the literature, patients' discomfort represents one of patients' main reasons for not cooperating with the orthodontic treatment [2; 5; 19]. Clear aligners (CA) are well-tolerated removable appliances, and they are thus accepted by patients since they are invisible and do not compromise the facial appearance. They cause minimal trauma or irritation thanks to their smooth surface. Patients experience slight alterations of pronunciation, especially in the first period, until they get used to it. This issue is generally considered as the most annoying part of the aligners' therapy, and it could influence compliance levels. However, patients become accustomed to CA very quickly and do not suffer much impairment, as a study on 54 patients showed that 83% of patients got used to the appliance within 1 week and 93% of them felt so secure wearing CA that they felt no inhibition while talking [31]. Clear aligners are designed to exert appropriate, precise, and calibrated forces on the teeth according to the type of malocclusion. Thus, patients are not subjected to heavy forces that may cause \"useless\" and deleterious aches and pains. Patients wearing CA report lower levels of pain, less stress and social anxiety, and higher Oral Health Related Quality of Life (OHRQoL) measurements. As a consequence, patients wearing clear aligners demonstrate a superior attitude during the treatment [22; 46]. A comparison between clear aligners and fixed appliances after the completion of orthodontic treatment assessed patients' satisfaction and OHRQoL. Similar satisfaction levels were found for the two treatment modalities, except for eating and chewing. CA significantly performed better for these activities compared to fixed appliances [21]. Compliance for CAT is required to be high, since aligners are meant to be changed regularly, and they need to be worn almost all day [39]. [PERSON] et al. [39] investigated several factors influencing compliance in clear aligner therapy in a large sample of 2644 individuals using a mobile application for the self-reporting of aligner wear. The results showed that 36% of the patients were fully compliant, 38.3% of them showed fair compliance, and 25.7% showed poor compliance. These findings are particularly relevant as one out of four patients demonstrated insufficient collaboration, which may jeopardize the therapeutic outcome. The effectiveness of clear aligner therapy, compared to the conventional fixed appliances, is widely discussed in the literature.