# Clear Aligner Treatment as a Safe Method for Treating Occlusal Trauma in Elderly Patients
## 1 Introduction  
Pathological teeth migration, as well as their increased mobility, widening of the periodontal space, possible bone resorption and pain are some of the most common symptoms and signs of occlusal trauma [1]. In addition to the aesthetic issue, patients report functional problems that make it impossible to perform physiological activities such as biting food and correct articulation [2]. Occlusal injury (traumatic occlusion, occlusal disease) is a set of very small changes, often microscopic or sub-microscopic, manifested by a periodic and reversible increase in tooth (teeth) mobility [3]. These are adaptive or pathological changes in the periodontium resulting from the occlusal forces generated by the mastectomy muscles [3]. Occlusal trauma is the damage to periodontal tissues caused by occlusal forces, and the entire occlusion that leads to periodontal damage is called traumatic occlusion [4]. Depending on the duration of the forces, occlusal injury can be classified as chronic or acute. Chronic occlusal trauma results in decreased bone density and widening of the periodontal space near the crown or along the entire length of the root, which causes an increase in teeth mobility and fremitus--i.e., noticeable or palpable small movements of the tooth when traumatic forces are applied to it [5, 6, 7]. The changes occurring in the periodontium in the case of occlusal trauma are histopathologicalally identical and independent of the type of traumatic occlusion. The most important difference concerns the resistance of the tooth/teeth and periodontal tissues to occlusal loads occurring in the oral cavity. The most important difference concerns destructive changes in the periodontium [2, 8]. Depending on the direction and magnitude of theapplied forces, occlusal injury causes tension and pressure. In the pressure zone, bone resorption, root cement resorption or hyalinization, periodontal fibre necrosis, increased vascular permeability, microhaemorrhage and vascular thrombosis occur. In the tension zone, if there is no inflammation, a new alveolar bone develops. Cement apposition and periodontal fibre elongation may sometimes occur [7]. After the cessation of the pathological forces, periodontal repair or regeneration is possible [9]. Physiologically occurring occlusal forces, even small ones, can have a destructive effect on the periodontium if it is reduced as a result of periodontal disease [2,10]. In clinical practice, the effects of traumatic occlusion are much more common in the anterior segment of the upper dental arch, especially in cases of loss of posterior tooth support [2,8]. The most characteristic manifestation of traumatic occlusion includes pathologic tooth migration (PTM), and the maxillary incisors are considered the most vulnerable to it. Depending on the research carried out, the incidence of PTM ranges from 30.3% to 55.8% in patients with periodontitis [11,12]. The specificity of the position of the upper incisors, for example, limited contacts on the proximal surfaces with the adjacent teeth, the absence of contacts or largely limited occlusal contacts with the incisors in the mandible, may cause their increased susceptibility to pathologic migration manifested by the lengthening of the clinical crown of the tooth/teeth [13]. Given the current standards in dental treatment aimed at reducing tooth extraction to the minimum, dentists face the challenge of preserving the patient's natural teeth for as long as possible [14]. In order to eliminate traumatic occlusion, it is possible to apply orthodontic treatment--e.g., by using conventional fixed appliances or aligners [15]. Orthodontic treatment is aimed at improving the position of the tooth/teeth, for example, by the intrusion of elongated incisors, reduction of diastemas caused by tooth fanning, and removal of premature occlusal contacts and occlusal obstructions [12].