# Laser Applications in Metal Orthodontic Bracket Debonding: A Systematic Review
## 1 Introduction  
Orthodontic treatment with fixed appliances involves the use of brackets. These include metal brackets, typically made from stainless steel or titanium (for patients with nickel allergies), and esthetic brackets made from ceramic crystals, often referred to as \"sapphire\" brackets\" [1; 2; 3]. Brackets are bonded to teeth using a composite material following the preparation of the enamel surface through etching and the application of an adhesive system. These brackets are designed to stay securely in place throughout the orthodontic treatment, which typically spans 2-3 years. Equally crucial is the ability to remove the brackets without causing damage to the tooth structure. Notably, when the shear bond strength (SBS) of the bond exceeds 10 MPa, the risk of enamel damage increases significantly, as the high forces required for removal can result in the detachment of enamel prisms [4; 5]. This underscores the critical need for optimizing debonding techniques to protect the integrity of the enamel during and after orthodontic care [5; 6; 7]. However, it should not be forgotten that it is not only the bond strength that determines enamel damage. Additional factors such as the type of orthodontic bracket and its dimensions are also important. This is due to the fact that debonding can occur between the tooth and the adhesive, within the adhesive, or between the adhesive and the bracket [8]. Over the years, numerous methods for debonding orthodontic brackets have been developed to optimize efficiency and minimize enamel damage. The most commonly employed technique involves the use of specially designed forceps that mechanically disrupt the adhesive bond during removal [9]. An alternative and less frequently used method employs pliers with an attached wire that is hooked under the bracket wings. This approach minimizes damage to the brackets, making them recyclable for future use [10; 11]. Another technique involves squeezing the bracket wings with Weingart forceps, which can distort the wings, alter the slot dimensions, and render the bracket unusable [11]. In 1995, [PERSON] et al. [12] introduced an electromechanical debonding device as an alternative method; however, while it failed to gain widespread adoption among clinicians, it gave rise to the electrothermal debonding method [13]. Ultrasonic debonding using specialized ultrasonic tips has also been explored. This method is associated with a lower risk of enamel damage compared to conventional techniques but is significantly more time-intensive [14; 15; 16; 17]. The safest method for enamel preservation involves the use of different essential oils like eucalyptus oil or peppermint oil to soften the composite adhesive. This allows for the mechanical removal of the bracket with minimal force, reducing the risk of enamel damage and leaving only a minimal amount of composite residue on the enamel surface. However, this technique requires the bracket to remain in contact with the oil for at least an hour, causing considerable patient discomfort and reducing its practicality [14; 18; 19; 20]. One potential method for debonding orthodontic metal brackets is the use of lasers. Three primary mechanisms describe this process: thermal softening, thermal ablation, and photoablation (Figure 1). The heat generated by the laser causes thermal softening of the adhesive material, enabling the bracket to detach from the tooth surface [4]. When the resin is heated rapidly enough to reach its vaporization temperature, thermal ablation occurs. This process precedes debonding via thermal softening, leading to the bracket's detachment from the tooth surface [21; 22]. Photoablation is a mechanism where high-powered laser light interacts with the adhesive resin, causing the bonding energy level between the adhesive atoms to exceed the dissociation energy threshold [23]. This results in thedecomposition of the resin material, allowing the bracket to debond [24]. There are many types of lasers; only some of these were evaluated in the included studies.