# Compressive Strength Comparison of Different Orthodontic Metal Bracket Systems
## 1 Introduction  
In orthodontic clinical practice, the rebonding process of brackets to their new positions is a commonly utilized technique, nearly ubiquitous in orthodontic treatment. Clinicians may remove and rebond brackets to achieve better positioning [1]. Various methods are employed for the removal of orthodontic brackets, including mechanical, ultrasonic, electrothermal, and laser techniques. Among these, mechanical debonding methods are most commonly preferred in clinical practice [2]. Debonding orthodontic brackets can cause enamel damage, even if it is not evident clinically or under microscopic examination [3]. The procedures for debonding and clean-up that result in the minimal enamel volume loss remain a topic of debate [4]. A successful debonding procedure is based on the principle of preserving a sound enamel structure without causing iatrogenic damage.  
Instruments used for the mechanical removal of metal brackets include Weingart pliers, Howe pliers, band removing pliers, ligature cutters, debonding pliers, and the Lift Off Debonding Instrument (LODI). Hand instruments like Weingart pliers typically apply compression force in the mesio-distal direction to facilitate bracket debonding from the tooth surface. It is believed that with this method, a significant portion of the adhesive resin remains on the tooth surface, minimizing stress on the enamel [5, 6].  
Biomechanical analyses using finite element method have investigated shear, compression, frontal torque, and lateral torque forces, common in debonding procedures, andhave found bracket wing compression to be the gentlest method in terms of enamel and periodontal ligament preservation. It has been concluded that undesired torque during bracket detachment can be easily prevented with bracket wing compression, thus avoiding additional loading on the periodontal ligament or alveolar bone [7; 8].  
When subjected to force, all solid materials can undergo deformation. Up to a certain force, a material returns to its original dimensions when the load is removed. The return to the original dimensions upon removal of the load is known as elastic behavior. The load beyond which the material no longer exhibits elastic behavior is called the elastic limit. If the elastic limit is exceeded, the material undergoes permanent deformation or a change in shape. A material that has undergone permanent deformation is said to have undergone plastic deformation.  
Considering rising costs and sustainability, it is imperative for brackets to be resilient and resistant to plastic deformation when being debonded from teeth. Deformation during bracket removal can occur in the wings, base, or slot of the bracket. In any of these cases, reuse of the bracket and subsequent reworking with the respective bracket become impossible [9]. Therefore, the resistance of brackets to plastic deformation is crucial during rebonding procedures.  
In the literature, numerous studies have measured the bond strengths of different brackets and adhesives during bracket debonding and compared them with different debonding techniques [10; 11; 12; 13; 14; 15; 16]. Additionally, there are studies examining plastic deformations resulting from torque forces applied by orthodontic wires [17; 18]. However, no studies investigating the plastic deformation incurred by different metal brackets during compression force application for removal could be found in the literature.  
In our study, we aim to compare the compression strengths and resistance to plastic deformation of different metal brackets, and to determine which bracket system is more preferable for rebonding and reusability. This research is anticipated to contribute to the national and international literature on the plastic deformation characteristics of brackets.  
**Null Hypothesis (H0).**_There is no significant difference in the resistance to plastic deformation and compressive strengths among the five different types of metal brackets tested in this study._