## 1 Introduction  
The goals of periodontal therapy are to eliminate the infectious and inflammatory processes of periodontal tissues. Subgingival plaque and calculus on the root surface in the periodontal pocket are the most important local factors for the occurrence and development of periodontitis [1]. Mechanical removal of plaque and calculus by manual and ultrasonic scaling instrumentation with ultrasound has shown equal effectiveness in in vitro and in vivo studies [1, 2]. Manual root planing eliminates \"infected cementum\", while ultrasonic instruments will not remove the cementum excessively and are also superior in terms of time saving and labour saving compared to using hand instruments [1]. The amount of tooth substance removed and the surface roughness after instrumentation need to be considered [3]. In this regard, it is important to take into account the involved tissue and investigate the mechanical properties of its components, which includes hydroxyapatiteapatite [4, 5, 6, 7, 8]. Extensive cement removal can results in an increase in root surface roughness and promote plaque accumulation and dental hypersensitivity [2]. On the other hand, while the roughness of the root favors the accumulation of plaque, its role in periodontal healing is still controversial. In fact, this surface favors the adhesion of fibroblasts and periodontal regeneration [9, 10].  
Polishing can be considered as the final stage of periodontal treatment after scaling and root planing [11]. During polishing, procedures could be selective or widely per formed [12; 13], such as plaque, biofilm, acquired film and extrinsic pigmentation removal from the tooth surface. Different techniques can determine surface alterations and roughness depending on the time and materials used [11; 14]. In clinical situations, supragingival biofilms and subgingival biofilms measuring within 3 mm can be removed mechanically using rotary instruments and a prophylaxis paste [15].  
Numerous studies have evaluated the root surface after periodontal instrumentation with different techniques, such as profilometric analysis [2; 11], histological evaluation [2; 16] and electron and confocal laser scanning microscopy [15; 17; 18].  
Recently the effects of mechanical periodontal instruments on the root surface have been studied through the SEM observation of replicas of the instrumented surface [19]. Replica technique, by means of SEM inspection of polyether replicas of tooth surface, allows the evaluation of the morphological alterations and changes in time, as proposed in several in vitro and in vivo studies [20; 21; 22].  
The first aim of this study was the morphological evaluation of the root surface subjected to manual and ultrasonic scaling with curette and conventional and diamond tips, respectively. The second objective of the study was to evaluate the effects of polishing carried out with a rubber cup and three medium-sized pastes on teeth subjected to manual and ultrasonic scaling. The root surface was examined--after instrumentation and after polishing--to evaluate the effect of the different procedures.  
The first null hypothesis of the study was that scaling, with both manual and ultrasonic tips, did not alter the root surface. The second null hypothesis was that polishing with the rubber cup and medium grain size pastes increases the roughness of root surfaces that were previously subjected to periodontal instrumentation.