## 1 Introduction  
In orthodontic treatments performed with fixed appliances or clear aligners, brackets or attachments are bonded to enamel [1, 2]. Despite a high bond strength between adhesive and enamel being sought to counteract forces due to orthodontic therapy, it increases the possibility of enamel damaging during debonding and clean-up procedures [3, 4]. At the end of the orthodontic treatment, a major concern is the removal of those devices and adhesive resin from enamel surface with less damage to the enamel surface as possible [1, 5]. Enamel damage may be a consequence of enamel cracking during debracketing procedure or grinding residual adhesive during the clean-up procedures. The outermost layer of enamel should remain as intact as possible since it is characterized by higher mineral content and fluoride than the deeper layers [6]. The loss of superficial enamel might cause a decrease in the resistance of enamel to the organic acids available in the oral environment, making it more prone to demineralization.  
Debonding and clean-up procedures are time consuming, cumbersome, and cause mental stress on both patients and orthodontists [7, 8, 9, 5]. Improper tools and devices, together with the haste of finishing the treatment, may lead to enamel damage. Furthermore,orthodontic adhesives used for bracket bonding are difficult to distinguish from the surrounding tooth structure, making them very difficult to remove without damaging the tooth structure. Hence, orthodontists, during adhesive removal, may accidentally affect excessive amounts of healthy tooth structure that may need avoidable future restorative procedures [10; 11].  
Clean-up methods after bracket debonding comprise hand or rotary tools such as diamond burs [12], tungsten carbide burs [13; 14; 15], silicone points [16], fiber-reinforced composite burs [17], and aluminum-oxide-coated disks [14; 18; 19]. Nevertheless, currently, there is no consensus on which technique must be preferred for orthodontic clean-up [3; 20].  
Qualitative analysis of adhesive residuals left after clean-up is generally performed through the ARI index [21] (0 = no adhesive; 1 = less than half of the; 2 = more than half of the adhesive; and 3 = all adhesive left with distinct bracket impression). Enamel damage assessment has also been performed mainly through qualitative methods such as the Enamel Damage Index (EDI) [22] (0 = smooth surface no scratches and perikymata still visible; 1 = only a few superficial scratches; 2 = several deeper grooves and scratches; 3 = grooves and scratches are detected with the naked eye) but seldom through quantitative analysis.  
So far, in fact, although new technologies such as micro-computed tomography (micro-CT) systems [23], profile projectors [24], null-point contact stylus systems [25], planer surfometers [26; 27], laser scanning [5; 5], 3D contact profilometry [28], and intra-oral scanners [29] could allow the quantitative evaluation of the enamel loss after debonding and clean-up procedures, only few papers have directly investigated it. Therefore, to investigate the quantitative enamel loss during debonding as well as during clean-up procedures, a systematic literature review was conducted.