## 4 Discussion  
Non-surgical periodontal therapy aims to remove bacterial plaque, calculus and contaminated cementum to prevent the progression of periodontal disease [24]. This therapy is based on the techniques of Scaling and Root Planing (SRP) that is carried out using manual and mechanical instruments. The first purpose of this study was the morphological evaluation of the root surface subjected to scaling by manual curette and ultrasonic devices with conventional tips and diamond tips. The second purpose was to evaluate the effects of polishing on the root surface of teeth subjected to the aforementioned scaling procedures. Manual instrumentation was once considered more effective than sonic and ultrasonic instrumentation; however, more recently, mechanical instrumentation has been widely accepted as an alternative or an aid to manual instrumentation as it shows the same effects in removing biofilm, subgingival calculus, and endotoxins [1,2]. Manual scaling with curettes allows greater control of the instrument and improves the operator's tactile perception, while the sonic and ultrasonic instruments allow better access to truncation and deep pockets, as well as reducing operator fatigue and instrumentation time [1,25]. There are various types of inserts for mechanical instruments; the standard steel inserts and diamond inserts were used in this study. The diamond coated inserts have been designed to increase the speed and efficiency of deposit removal [26] and, in fact, the instrumentation time is reduced by 60% when using the diamond coated inserts. Their effectiveness and speed have been proven by several studies [26,27]. The experiments carried out so far agree that ultrasound with diamond inserts removes a large amount of root surface and can damage the root if not used correctly [17,28]. Root debridement with this type of insert should be performed with the utmost caution [3]. The diamond coating of the instrument removes the dental tissue with a \"pulverizing\" action. The diamond granules provide the tool with a multitude of edges and each cutting surface is a working part of a multi-faceted tool. Each of these diamond granules contact the tooth surface and exerts an impulse so as to remove the harder dental tissue than with other smooth inserts due to microabrasion [3,28]. The roughness produced by sonic, ultrasonic and manual instruments has been examined in several studies, but the findings are often conflicting. Some experiments show that manual instrumentation produces a smoother surface than ultrasonic instrumentation [29]. In contrast, other studies report that mechanical instruments are better for use on the root surface by producing minimal roughness than curettes [3,30]. The effects of scaling procedures on root surface Kocher are still debated. The smear layer often forms following root debridement and causes a barrier between the periodontal tissues and the root surface; this inhibits the formation of a new connective attachment and alters periodontal healing [24]. The roughness produced by scaling could affect bacterial colonization and fibroblast adhesion [24]. A smoother coronal root surface can be very important for avoiding subgingival bacterial colonization, while in the central and apical area it would be optimal to obtain a rougher surface to allow greater adhesion of fibroblasts [31]. Our experimentation revealed statistically significant differences in surface texture and in the presence of instrumentation signs before and after treatment for all groups examined (\(p<0.05\)). The three types of scaling procedures altered the root surface, and the first null hypothesis of the study should be rejected. SEM morphological analysis of the ultrasonic-instrumented root replicas with a standard steel insert showed smoother and more homogeneous surfaces than those instrumented with curettes.