# Anchorage Loss Evaluation during Maximillary Molars
###### Abstract  
The purpose of the research was to analyze the premolar and canine anchorage loss observed during maxillary molars distalization in subjects with Class II malocclusion treated with clear aligners. A total of 49 subjects (27 females, 22 males, mean age 14.9 \(\pm\) 6 years) derived from the Department of Orthodontics of the University of Rome \"Tor Vergata\" were selected according to the following inclusion criteria: Caucasian ancestry, Class I or minor Class II skeletal malocclusion, Class II occlusal relationship, permanent dentition with fully erupted second molars, and good compliance with aligners. Each patient underwent the same non-extractive molar distalization protocol with no auxiliaries other than attachments and Class II elastics. Prior to treatment (T1) and at the end of the first maxillary molars distalization movement (T2), digital dental casts were taken by using an iFero intraoral scanner. Linear measurements were performed in order to evaluate the anchorage loss at the level of the second and first premolars and the canines. The statistical comparison of T2 and T1 values was obtained using a paired _t_-test (_p_ < 0.05). A statistically significant distalization of the maxillary first permanent molars (2.5 mm) was observed; a slight and not significant anchorage loss of the first and second premolars was assessed, while a statistically significant mesial movement of upper canines (1.33 mm) was highlighted. Clear aligner treatment was effective in obtaining a molar distalization movement. However, during molar distalization, an anchorage loss at the level of upper canines was observed. clear aligners; molar distalization; anchorage loss; digital casts 2023133646. 202313646.  
known are the Hilgers' Pendulum, the Distal Jet, the Jones Jig, and the First Class. Each of these structures is composed of a passive unit, usually an acrylic Nance button, and an active unit, such as superelastic nickel-titanium (NiTi) archives [8], coil springs on a continuous archive or one sectional archive [5; 9], springs in beta titanium alloy [10], and vestibular screws associated with palatal NiTi coil springs [6]. Their strength is the absence of patient effort, but some negative effects may result during the therapy [5; 6]. The main disadvantages encountered are dental anchorage loss, the flaring of the maxillary incisors, the mesialization of premolars, the distal tipping of maxillary molars, the clockwise rotation of the mandible, and an increase in the lower anterior facial height due to the distal tipping of maxillary molars. These adverse effects are principally due to the use of the dental unit as an anchorage unit during the molars' movement. In order to reduce these unwanted dental secondary movements, temporary anchorage devices (TADs) were recently introduced to orthodontic treatment, which use the bone instead the teeth as the anchorage unit. Various authors [11; 12; 13; 14] have reported favorable results using this system as a support in the distalization mechanics of maxillary molars. However, also in the use of TADs, it is necessary to consider some risks and complications related to the structure of the device, such as a screw fracture. Additionally, pain, discomfort, and invasiveness for the patients cause a lack of collaboration, as well as the clinician's learning curve for the placement of TADs and root proximity [11; 12; 13; 14]. In recent years, an increase in demand for aesthetic, minimally invasive, and more comfortable orthodontic solutions has been seen in adults and growing subjects. Therefore, the orthodontic treatment with removable clear aligners (clear aligners treatment (CAT)) has become a competitive and more hygienic alternative to conventional fixed appliances [15]. CAT is today used also for maxillary distalization movement with the advantage of planning the molar backward movement and teeth alignment simultaneously, thus reducing treatment duration [16].