External tooth discoloration is caused by the adhesion of staining substances to the accumulated plaque on the teeth and chemical changes in the content of the deposits resulting from this organic combination . Since the roughness of the oral hard tissues and restorative materials increases plaque retention, the surface roughness will affect the color change. Therefore, the polishing process has great importance . In order to prevent recoloring after the polishing process applied to remove tooth stains, the agents to be used in the treatment process should not increase the roughness. Because a well-polished enamel surface holds less plaque than a rough surface, and thus the risk of recoloring is reduced . Therefore, materials that establish smooth enamel surfaces and do not damage the enamel should be preferred.
Instead of pumice, which is used as a classical polishing material, many new polishing pastes have been produced with the claim that it causes less damage to the enamel surface. At this point, in the use of these materials, which are much more costly than pumice, their superiority to pumice in terms of surface roughness becomes important. In the study conducted by Covey et al. in 2011, they applied polishing rubber to enamel surface samples with and without polishing paste. The initial and final roughness values were measured with a profilometer. Surface roughness increased significantly in enamel samples with polishing paste applied. It has been stated that the abrasive feature of polishing pastes used during polishing is the reason for the roughness on the enamel surface . In this context, in the present study, after measuring and visualizing the initial surface roughness of primary tooth enamel, the difference between the roughness and appearance of the enamel surfaces after polishing using three different polishing paste with pumice was evaluated. As a result of the research, polishing pastes produced to be used instead of pumice remove external discoloration on the surface of the primary tooth enamel, while the ones that do not increase the roughness -as it has been suggested- will prevent recoloring and plaque retention and will help clinicians in the selection of the most affordable material.
In the literature, it has been observed that different methods are used to evaluate the roughness of different applications on dental tissues and restorative materials. When the literature is reviewed, it was seen that there are many studies [19-22, 25] examining the surface roughness with SEM [15-18] and profilometer. SEM has some disadvantages such as its inability to display the surface properties in three dimensions, it is a qualitative method that cannot give a quantitative result, requires specific (coating, etc.) processing . On the other hand, profilometers allow a two-dimensional measurement of the surface profile by going over the material surface of a diamond point [26, 27] . Mechanical profilometers have been widely used for many years to measure surface roughness [28-30]. The most important advantage is that the samples do not require a preliminary preparation stage, thus allowing repeated use and measurement of samples . On the other hand, its most important disadvantages are that it cannot provide visualization of its surface and gives only a quantitative measurement [26, 27]. AFMs can make measurements in wide scales ranging from nano-size to micro size . Measurements made at the nanometric level provide a much more detailed measurement of the surface topography than the profilometer. It has important advantages that it gives a three-dimensional image that cannot be obtained with SEM or profilometry and does not damage the examined tissue because it does not require a special coating process such as SEM . However, it could not be used routinely in the assessment of surface roughness because it is expensive compared to profilometer and SEM and the measurements take a long time . As it can be understood, there is no consensus among researchers about the method of evaluating surface roughness, as each technique has its own advantages and disadvantages. In our study, we evaluated it with AFM analysis because it gives high-resolution objective results.
Researchers have used different types of human teeth in various studies. Chowdary et al.  conducted a study with 60 teeth in 2018. They included each tooth extracted for periodontal reasons and showed no signs of caries, abrasions or fractures. Castanho et al.  , Giampaolo et al.  and Salami et al.  used a third molar tooth in their study in which they evaluated enamel roughness. Willman et al.  stated that they used molar teeth in their study in which they examined the roughness change created by polishing methods on the enamel. Yurdagüven et al.  preferred central incisors in their study. In the present study, in which we evaluated the effect of different polishing methods on primary tooth enamel, primary molar teeth were used because of their more sensitive structure than permanent teeth.
In a study performed by Chowdhary et al., the effectiveness of three different polishing systems on enamel was compared with SEM. Compared polishing methods were polishing paste application with polishing rubber, polishing paste application with bristle brush and air abrasion. All polishing tools used in this study were applied to the samples for 15 seconds. The rotation speed for the tire and brush applied with the help of a motor is between 2500 and 3000 rpm. In the present study, the application was carried out for 10 seconds with a rotation speed between 2000 and 3000 rpm in accordance with the manufacturer's instructions. According to the study results of Chowdhary et al., it has been reported that the surface of the samples treated with an air-polishing device has a more irregular surface than the surface of the samples treated with rubber and brush. It has been suggested that polishing with a rubber brush is the most effective method for obtaining smooth surfaces .
Castanho et al. compared the air abrasion method applied with pumice and paste and sodium bicarbonate spray applied with a rubber brush. They stated that the use of sodium bicarbonate spray results in rougher surfaces than the pumice mixture. Also, they found that the use of polishing paste did not show a statistically significant difference when compared to other methods. In their study, although the brands of polishing pastes are different from the ones we use, it was revealed that the use of polishing paste did not show a statistically significant difference compared to pumice similar to our study .
Salami et al.  investigated the effects of sodium bicarbonate jet, pumice and a whitening paste on enamel using SEM. According to the results, pumice caused the enamel to wear, resulting in a smoother surface than natural enamel. However, the surface formed as a result of polishing with pumice was found to be rougher than the enamel surface which was polished with sodium bicarbonate and paste. However, statistical analysis and SEM images showed that the erosion power of pumice can change the enamel and create a more homogeneous surface than the natural one. In parallel with the results of our study, all methods are statistically significant in reducing enamel roughness. And the roughness measurement values of the pumice group gave mathematically higher results than the other groups.
In the study conducted by Yurdagüven et al. , the effects of polishing paste (Septodont-Detartrine, France) on enamel, dentin, porcelain and various composite types were investigated. The researchers first smoothed the surfaces with discs and then polished them with pumice and distilled water. After this process, the initial roughness value was measured. Then the paste was applied and the final roughness values were measured. As a result, they found that the prophylaxis paste increased the surface roughness of all groups. We think that this result, which is different from our result, is since Yurdagüven et al. tried to obtain an initial roughness value close to the strip band surface roughness by flattening the surface of all samples with a disk in order to establish standardization before the first roughness value measurement. In this study examined  , the evaluation was made by SEM imaging, and since the coating process was applied to the sample used, the initial and final measurements could not be made on the same sample, so a standardization process was performed. In our study, there was no need for such a procedure since the examination was performed with AFM. On the other hand, although our study is an in vitro study, we aim to try to obtain results that can be integrated into clinical conditions. For this reason, this application was not performed in our study since there is no possibility to polish the surface of the tooth of a child patient during clinical practice after flattening with a disc.
In the study conducted by Camboni et al. in 2016, the effects of different polishing pastes (Prophy Paste CCS®, Proxyt®, Cleanic®, Super Polish) applied with rubber on enamels were compared with SEM imaging. It was observed that there was an increase in roughness on the surfaces where the polishing paste applied with a rubber brush was applied compared to the control surface  . The reason for this result, which is different from our findings, might be due to the fact that the evaluation with SEM does not provide quantitative data and cannot display the three-dimensional surface profile. On the other hand, the evaluation with AFM, which we used in our study, provided quantitative results and the opportunity to examine with high resolution.