# Impact of the Enamel Cleaning Procedure during Debonding on Endodontium Temperature: In Vitro Tests
## 1 Introduction  
Orthodontic treatment with fixed braces, apart from the obvious effect on the stomatognathic system (including the occlusion and periodontium), also interferes directly with the tooth tissue by chemically and mechanically bonding the orthodontic brackets to the enamel and then cleaning the adhesive residue after treatment and removing the brackets.  
The pulp filling the tooth cavity is richly innervated and vascularized connective tissue that performs a number of functions responsible for the health and life of the tooth, such as nutritional, sensory, creative and restorative and defensive functions. It is believed that the interdental temperature is similar to body temperature (approximately 37 \({}^{\circ}\)C), although the actual temperature has not yet been measured. The in vitro tests carried out so far that involve simulating blood flow in the pulp established the pulp temperature at 33-35 \({}^{\circ}\)C, and the tolerance of temperature changes in the range of25-42 \({}^{\circ}\)C [1; 2; 3]. In the in vitro studies presented in the article below, the focus was on assessing the temperature within the vestibular wall of the pulp chamber bordering the dentin, which conducts heat to the chamber and directly to the pulp in vivo.  
The objective of this study was to assess the pulp chamber temperature change as a function of time under the influence of the enamel cleaning procedure with silicone rubber and aluminum oxides with and without water cooling.  
The tissue reacts to both low and high temperatures, and raising the temperature by 5 \({}^{\circ}\)C is harmful and leads to inflammation, and in extreme cases to tissue necrosis [4]. The mechanism of action of thermal stimuli is explained by their effect on vasomotor nerves, which leads to rapid congestion or ischemia. In this way, there are disorders in the nutrition of the pulp. The congestion phase becomes inflamed, and hence the pulp becomes inflamed. An undeniable and confirmed fact is the assumption that the operating procedures used in conservative dentistry and prosthetics generate heat within the tooth and periodontitis, which is a huge stress for the pulp, especially with repeated stimuli [5]. Bonding orthodontic brackets requires the use of adhesive materials, such as composite adhesives that require polymerization, during which heat is generated and transferred to the pulp-dentin complex (endodottium) [6]. Another aspect of orthodontic treatment during which heat is generated is the cleaning of the enamel to remove residual composite materials using the method of cutting with milling cutters or polishing with erasers mounted on a micromotor. Pulp irritation caused by the operation of dental drills depends on the number of drill revolutions, the size and material of which it is made, and the intensity and type of cooling as well as the type of polymerization lamps used to polymerize the composite materials [2; 4; 7; 8; 9; 10; 11; 12]. So far, studies have been published investigating the dependence of pulp thermal sensitivity on dentin thickness [13].  
Teeth have poor heat transfer properties, and their overall thermal conductivity is about 0.6 Wm\({}^{-1}\)K\({}^{-1}\), which protects the pulp against overheating [14; 15].  
The tooth consists of a high-hardness enamel that is attached to the dentin. Between the dentin and the enamel, there is a dentin-enamel junction (DEJ) zone that is 100-150 \(\upmu\)m thick. The thermal conductivity of the enamel is about 0.81 Wm\({}^{-1}\)K and the dentin is 0.48 Wm\({}^{-1}\)K\({}^{-1}\), which means that heat transfer into the tooth is limited. Nevertheless, these parameters are effective in pulp protection only up to the temperature of 42 \({}^{\circ}\)C [16; 17; 18].