## 4 Discussion
However, replicas of ultrasonic-treated samples showed the presence of cracks that are also visible at higher magnification in samples treated with ultrasonic diamond tips and this observation partially agreed with other results showing that ultrasonic instrumentation produces a significantly higher quantity of cracks [24]. A positive correlation between the roughness of the root surface and the power of ultrasonic instruments, likely due to an increase in lateral pressure during instrumentation due to the operator's poor tactile perception with increasing power, has also been reported [25]. In relation to the samples treated with curettes, clear signs of instrumentation and surface irregularities are evident. Samples instrumented with diamond ultrasound showed a relatively homogeneous surface with localized signs of instrumentation and loss of substance. This last result is in contrast with previous studies that associate the diamond insert with a more irregular surface and a greater loss of substance than instruments with smooth inserts [3,17,28]. However, in the present study, no statistically significant differences were found between the manual and mechanical scaling procedures at the chosen value of 0.05. The results of the study can be compared with those of numerous articles in the literature that present partly concordant results [3,30,32]. However, the presence in the literature of studies reporting completely discordant results confirmed that the question is still debated [16]. All these controversies about the effects of manual and ultrasonic instrumentation are probably due to differences in study designs (e.g., in vivo studies and in vitro studies) and the lack of standardization [3]. In current dental practice, polishing agents are predominantly used for the removal of biofilm and extrinsic pigments by using a selective procedure [13,33]. Polishing is a more comfortable, less stressful and less painful act than scaling and root planing and it is commonly well tolerated and requested since it produces immediate benefits that are perceptible by the patient [12]. Extensive removal of the cervical cement, that could be produced by periodontal instrumentation, can result in greater surface roughness favoring plaque retention [34]; however, the literature reports that dentin and cement are highly subject to abrasive phenomena [35] and so polishing maneuvers on these tissues could cause morphological and structural changes [36]. The most common method for dental polishing involves using a rubber cup and pumice as an abrasive agent. Over the years, some studies have suggested the use of other abrasive agents for polishing, such as zinc oxides or kaolinite pastes, but pumice powder and fine glycerin continue to be the most widely used [11]. The effectiveness and safety of polishing with a rubber cup and prophylaxis paste are influenced by rotation speed, abrasiveness of the paste, applied pressure and the duration of treatment [33]. The use of a polishing cup and abrasive agent at excessive speeds and pressure could remove a superficial layer of cement and very thin tissue at the cervical level [36]. For this reason, during polishing with the rubber cup, the handpiece should be equipped with a torque that guarantees a constant speed (from 2000 to 3000 rpm) protected from oscillations [14]. In this study three polishing pastes medium grain size (74-105 \(\upmu\)m) in single-dose cups were analyzed: Stomyprox media(r), Ultrapro Tx cool mint medium(r) and Nupro medium orange(r). The results of the statistical and SEM morphological analysis did not show statistically significant changes before and after polishing procedures in all teeth regardless of the type of scaling (manual and ultrasonic). Polishing resulted in the improvement or maintenance of the surface texture, which confirms the effectiveness of polishing in reducing the roughness caused by periodontal instrumentation and its safety in not increasing roughness.