The purpose of this study was to evaluate the residual cementum with the histological measurements and root surface topography with SEM evaluation using four periodontal treatment methods.

Cementum is a component of the periodontium, and its major role is to serve as the site of attachment for principal collagen fibers (Sharpey' s fibers). In particular, cementum, by virtue of its structural and dynamic qualities, provides tooth attachment and maintenance of occlusal relationships between the jaws. Its multiple functions are fulfilled by the biological activity and reactivity of cementoblasts, which deposits two collagen-containing varieties of cementum with completely different properties. Periodontal disease is the local inflammation of the supporting tissues of teeth, it causes destruction of gingival tissues, bone loss and loss of connective tissue attachment to cementum. Since the relationship between local bacteria and periodontal disease has been proved and widely recognised, it is generally accepted that removal of pathogenic microorganisms that form plaque and calculus is the major goal of periodontal treatment. This therapy currently consists of scaling and root planing, but in addition to mechanical instrumentation, regeneration and restoration of various periodontal components to their original form, function and consistency should be performed.

Previously it was accepted that bacterial endotoxins or bacteria penetrate the cementum of periodontally diseased root surfaces. Therefore, besides the removal of the subgingival plaque and calculus deposits, the removal of all or most of the cementum was one of the primary endpoints of periodontal healing. The goal of periodontal therapy was to attain a planed root surface with a smooth and hard surface characteristics and free of endotoxins as the cementum of a tooth prior to eruption. While some studies have reported that endotoxins are not located within cementum it has been accepted that the removal of 'diseased' cementum was not necessary for a successful periodontal treatment.

Saygin et al. reported that cementum is the site where soft-tissue attachment has to be re-established, and cementum matrix is a rich source of many growth factors which influence the activities of various periodontal cell types and Grzesik et al. stated that cementum plays a regulatory role in periodontal regeneration. From these studies it can be concluded that non-aggressive periodontal treatment is necessary for optimal periodontal health as well as for periodontal regeneration.

During periodontal therapy subgingival instrumentation by means of the removal of root cementum can be eventually lead to exposure of dentinal tubules, pulp injury and dentin hypersensitivity. The in vitro studies including establishing in vitro experimental models under standardized experimental conditions evaluated the amount of cementum with various instruments or force combinations. Several studies, which showed the effects of different instruments on root surfaces, emphasized that periodontal treatment can be performed less aggressively with respect to the removal of cementum.

Previously reported that the teeth treated by HC and US can present a surface without cementum and the open dentinal tubules.They reported that root surfaces treated by US showed a scaly and rough topography whether the teeth treated with HC presented smooth surfaces. Kawashima and co-workers compared two different piezoelectric US (VectorTM and EnacR scaler) and HC and found that both US groups had significantly more remaining cementum than the HC group. However they observed some areas with thin or absent cementum in the HC group. Ruhling et al. compared the effects of the piezoelectric US, sonic scaler (SS), sonic scaler insert coated with Teflon tube, Periotor insert and HC. They showed that HC and SS group presented greater removal of root cementum and nearly all cementum was removed in 25% of the samples treated with HC.

Tomasi et al. reported that biofilm and calculus certainly should be removed but also they questioned the requirement for removal of contaminated root cementum by root planing. US with new shaped tips and AP devices as alternative to HC designed for subgingival access have been developed for minimal root damage. In recent years, there are newly developed instruments presenting clinically efficient results in the treatment of chronic periodontitis. Subgingival AP has been suggested as a treatment modality for root debridement. Two recent studies have investigated the clinical and microbiological efficacy of subgingival AP by glycine powder in periodontal pockets and they revealed probing depth reductions and removal of subgingival biofilm. Today there is no scientific research evidence showing the loss of root substance or surface roughness by subgingival AP or US instrumentation with AP.

The aim of the present study was to compare the effect of in vivo root instrumentation using a new piezoelectric US instrument, HC and air polishing by glycine powder, under routine clinical conditions, on the thickness and surface characteristics of cementum.

Forty-eight periodontally involved caries free, single rooted teeth with advanced periodontitis scheduled for extraction treated in four different methods. The teeth were instrumented subgingivally at one approximal site either by hand curettes (HC), piezoelectric ultrasonic scaler (US), piezoelectric ultrasonic scaler following air polishing, air polishing (AP) alone. Upon extracting the teeth, instrumented and other non-instrumented sites analyzed with a dissecting microscope and SEM for the measurement of amount and surface characteristics of residual cementum.

Inclusion Criteria:

• systemic factors (no systemic diseases; no medications affecting periodontal status in the previous 6 months; no pregnancy or lactation;
• behavioral factors (no smoking habits);
• dental and periodontal factors not to have had previous periodontal therapy; no class III dental mobility;
• a periodontal probing depth (PPD) ≥ 4 mm in at least two sites per tooth with single rooted ;
• have no caries or restorations on the mesial and distal surfaces and bleeding on probing.

Exclusion Criteria:

• systemic diseases; medications affecting periodontal status in the previous 6 months; pregnancy or lactation
• smoking habits
• have caries or restorations on the mesial and distal surfaces and bleeding on probing.
• have had previous periodontal therapy; class III dental mobility;