# Impact of the Enamel Cleaning Procedure during Debonding on Endodontium Temperature: In Vitro Tests
## 4 Discussion  
Dental teeth cleaning is a basic procedure required in many therapeutic cases. In orthodontics, it is performed before the start of treatment with fixed braces and after the completion and removal of orthodontic brackets, after which residues of the adhesive composite remain on the enamel surface. In this in vitro experiment, however, the enamel was free of residual material to unify the results. When removing brackets, a different amount of composite material remains on the enamel, which has a direct impact on the length of the enamel cleaning procedure. The Adhesive Remnant Index (ARI) indicator analyzed in already published studies is used to assess this phenomenon [19]. In this study, the goal was to polish the enamel of each tooth at the same time and with the same force exerted on the tooth. The proposed research methodology was aimed at quantifying the dynamics of tooth temperature changes during mechanical cleaning as part of the debonding procedure in vitro. Figure 6: Exemplary thermograms of incisors subjected to polishing with water cooling. (**a**) 10 s of polishing; (**b**) 20 s of polishing; (**c**) 60 s of polishing; (**d**) immediately after finishing; (**e**) +5 s after finishing; (**f**) +10 s after finishing; (**g**) +20 s after finishing; (**h**) +50 s after finishing; (**i**) +70 s after finishing. Thermal tests performed in vivo are highly subjective because they are completely dependent on the patient's response to the stimulus. In general, most in vivo research methods require a subjective assessment of the effects of tissue stimulation, which reduces the objectivity of the results obtained. That is why it is so important to carry out in vitro tests [20; 21]. Teeth polishing, when carelessly carried out, can cause not only mechanical damage to the enamel [22; 23; 24; 25], but also irreversible changes in the pulp. The thermal impact of rotary dental tools is the result of several parameters, including the type of drill (its shape, hardness and roughness), the speed of rotation of the dental drill, pressure, exposure time, and enamel thickness [13; 26]. It should be emphasized that as a result of the mechanical impact of the drill on the enamel, there may be a significant increase in temperature within the pulp chamber. Generally, heat distribution can take place through radiation, convection and conduction. In the test model, the heat is distributed within the tooth tissues during the conduction process. Quantitatively, this process consists mainly of the thermal conductivity coefficient, which is about 0.6 Wm\({}^{-1}\)K\({}^{-1}\) for whole teeth, 0.81 Wm\({}^{-1}\)K for dentin, and 0.48 Wm\({}^{-1}\)K\({}^{-1}\) for enamel and dentin. Between the dentin and the pulp chamber, there is a physical connection between the dental tubules and pulp cells with a high heat transfer coefficient (high water content), and thus heating of the dentin will directly affect the heating of the pulp chamber. Physiologically, the DCJ effectively protects the pulp up to a temperature of 42 \({}^{\circ}\)C, while above this temperature (which, as we have shown in this paper, is formed by polishing), the DCJ zone ceases to fulfill its protective function, which may be the cause of damage or even death of the pulp [18]. The time after which the safe temperature of 40 \({}^{\circ}\)C is exceeded without water cooling was 29.4 s, while the use of water cooling increases it to 34.6 s. The time needed to clean the enamel is on average 18-40 s depending on the attachments used and the method of etching and cleaning the enamel [27]. Considering these facts, doctors should be made aware of how much time they should devote to cleaning or polishing enamel so as not to cause an iatrogenic effect on tooth health. It is also important to limit the polishing of composite fillings, which for a satisfactory aesthetic effect often require a long polishing time with the whole set of polishers, often exceeding the polishing time considered safe several times [28].