# Pain Perception during Orthodontic Treatment with Fixed Appliances
## 1 Introduction  
The high incidence of dento-maximilary anomalies and patients' desire to improve facial appearance and esthetics have increased the number of patients seeking orthodontic treatment, especially with fixed appliances. Recent studies have shown that people, especially adolescents and adults, prefer to undergo a treatment with clear aligners to safeguard esthetics. Unfortunately, only a small number of them can afford the costs of this more comfortable and esthetic treatment type [1, 2]. Pain sensation and masticatory discomfort are the most common side effects of orthodontic treatment. For efficient patient compliance and favorable outcomes, the orthodontic should inform patients about these aspects before starting treatment and should evaluate their motivation and potential risks. Moreover, it is ethically important to inform the patient about potential side effects of treatment, and it should be part of the patient's informed consent [3]. Orthodontic tooth displacement induces specific inflammatory reactions of the periodontium and the dental pulp that stimulate the release of various biochemical mediators, thus causing the sensation of pain [4, 5]. Generally, theaction of orthodontic appliances consists of a change in the balance of the preexisting dentofacial forces, by triggering new ones or by favoring and selectively directing the action of natural forces. Orthodontic forces depend on the properties of the appliances' materials (elasticity of wires/rubber rings, etc. ), the construction particularities, and its interrelation with the dento-maximly system [6; 7; 8]. The essential coordinates in orthodontic biomechanics are the orthodontic force, the weight-bearing area, and the application area, forming [PERSON]_'s triad [9]. Force applied to the tooth crown is transmitted through the root to the periodontal ligament and the alveolar bone. For tooth displacement, alveolar bone resorption should occur in response to this stress; for the tooth to remain firmly attached, bone deposits should also develop to maintain the integrity of the attachment mechanism [10; 11; 12; 13]. The International Association for the Study of Pain (IASP) defines pain as an unpleasant sensory and emotional experience associated with actual or potential tissue damage [14]. On the other hand, psychogenic pain is the pain generated by pure concurrent psychological factors strictly related to the person concerned or the environment in which that person lives. Psychogenic pain determined by the patient's psycho-emotional condition does not have a somatic origin [15]. Since pain is a subjective experience, we cannot evaluate it by indirect methods. In the case of children who cannot provide conclusive answers, the following parameters might be assessed:  
* Physiological parameters: pulse, blood pressure, and sweating;
* Behavioral parameters: facial expressions (closed eyes, open mouth, dilated nostrils, hollow tongue), high-pitched crying, and body movements (kicking, closed fists) [16]. Still, there are some scales to determine pain intensity. * Verbal scales--used at the time of presentation or during treatment, which classifies pain in 3, 5 or 7 grades: absent/weak/mild/moderate/intense/severe/ extreme pain [15]. * Visual analog scales--these consist of a line with a length of 10 cm, oriented vertically/horizontally, whose extremes are two terms: \"no pain\" and \"the greatest possible pain\" [17]. * Numerical scales--in these cases, the patient is asked to quantify pain using numerical values between 0 and 10 or 0 and 100 (0 representing no pain and 10/100 extreme pain). These scales are easier to understand, providing at the same time a better description of pain intensity, and frequently replace verbal/visual scales [17]. * Behaviorally anchored scales--these quantify the intensity of pain based on its effect on behavior and describe the impact of pain on daily activities [17]. The study aimed to evaluate the intensity of pain perception in patients undergoing fixed orthodontic treatment.