## 4 Discussion  
In the present study, scaling and root planing were evaluated through an in vitro study, as this facilitated the selection of a comparable test surface and permitted the standardization of the experimental procedures [18]. Previous studies using older tip designs have shown that ultrasonic instruments have a greater potential to produce root surface damage than curettes [19; 20]; however, in more recent studies, ultrasonic instruments could produce root surfaces as smooth as or smoother than those produced with curettes [21; 22]. Current evidence suggests that ultrasonic instruments used at medium power may do less damage to the root surface than curettes [23]. In this study, it was observed that the root surface roughness produced with the ultrasonic scaler and Gracey curette was similar. It has been established that there is no difference in bleeding upon probing, periodontal pocket depth, or clinical attachment levels when using ultrasonic or hand instruments [24], although a significant difference in root roughness has been reported when manual and ultrasonic instruments were used [16]. Regarding hand instruments, to the best of our knowledge, there have been no studies comparing the effects of debridement on the root structure using separate hand instruments, such as Gracey and double Gracey curettes. In this study, the effects of these different curettes and an ultrasonic scaler on the root surface ultramorphology were examined. [PERSON] conducted another study to compare the effects of different brands of Gracey curettes (no. 5/6), including carbon steel and stainless steel curettes, on the resulting root roughness and topography. He suggested that the quality of the cutting edge of the curette leads to a difference in the topography of the root surface. His study showed that stainless steel millennium provided the most homogeneous root surface [16]. In our study, in terms of smoothness, the Gracey curettes produced a smoother root surface compared to the double Gracey curettes, consistent with the study mentioned above. Based on the results of the current study--which had an in vitro design involving SEM--we found that the double Gracey curettes produced greater root roughness than the Gracey curettes. These results were in accordance with the study of [PERSON], who compared a long-shank, short-blade curette against the conventional Gracey curette variant (Curvette Sub-0) in vitro using a profilometer. His results verified that the test curette (Curvette-0) caused greater root roughness [25]. In the present study, all the test groups (i.e., ultrasonic instrument and Gracey and double Gracey curettes) presented gouging and cracks of varying sizes on the root surfaces. The root surfaces also exhibited deep scratches after root instrumentation. These results are consistent with many other studies that have reported the presence of cracks and gouging when using hand instruments [25; 26; 27]. Similarly, a recent clinical trial that evaluated clinical outcomes and post-treatment hypersensitivity using Gracey curettes, ultrasound, and diamond burs revealed that Gracey \begin{table}
\begin{tabular}{l l l l l l} \hline  & **N** & **Minimum** & **Maximum** & **Mean** & **Standard Deviation** \\ \hline Group 2 & 8 & 40 s & 60 s & 53.5 s & 6.65 \\ \hline Group 3 & 8 & 46 s & 65 s & 54.13 s & 6.68 \\ \hline Group 4 & 8 & 24 s & 48 s & 35.75 * s & 8.32 \\ \hline \end{tabular}
\end{table} 
Table 4: Descriptive statistics of periodontal instrument usage times of the groups (* \(p<0.01\)). curettes and ultrasound improved clinical performance in terms of attachment levels when compared to diamond burs [28]. In this study, no exposed dentinal tubules were found when using Gracey curettes or ultrasonic scrapers; however, exposed dentinal tubules were observed when using double Gracey curettes. Therefore, root sensitivity is expected to be higher when double Gracey curettes are used compared to ultrasonic and Gracey curettes. The results of this study are limited to single-rooted teeth only.