The "Glossary of the American of Periodontology" defines gingival recession (GR) as the apical movement of the gingival margin beyond the cement-enamel junction. Therefore, root surface exposure brought on by gingival recession results in cosmetic impairment, fear of tooth loss, increased susceptibility to root caries, and dentin hypersensitivity. The use of free gingival grafts, sliding pedicle grafts, subepithelial connective tissue grafts, envelope or tunnelling techniques, the use of acellular dermal, connective tissue allografts, guided tissue regeneration, and coronally advanced flap (CAF) are the surgical methods that have been developed to treat gingival recession. The medical area has been invaded by nanotechnology, and the findings are highly promising. Nanomaterials perform far better than conventional materials thanks to their superior surface, size, and quantum effects. Hydroxyapatites (HAs) are a family of materials used for bone grafting that have a high level of biocompatibility, which is partly due to their inclusion in naturally calcified tissue. The aim of the present study was to compare between nanocrystalline hydroxyapatite and tricalcium phosphate carried on PRP membrane in treatment of Miller's class 1 gingival recession in human.

The primary objective of periodontal therapy is the regeneration of periodontal tissues that have been lost owing to periodontal disease since gingival recession results in the loss of both soft and hard tissue. Periodontal regeneration, demonstrated histologically by the development of new cementum, new alveolar bone, functionally orientated periodontal ligament, and gingiva, is the rebuilding of the lost tissues. Platelet rich fibrin (PRF), which contains significant amounts of growth factors, platelets, fibrin membrane, leukocytes, and cytokines, was introduced for periodontal regeneration. The capacity of PRF to boost collagen production and fibroblast proliferation has been demonstrated, and it is widely used to repair and enhance the regeneration of both soft tissues and hard tissues following various periodontal surgical procedures. Xenografts were established in the field of periodontology to address the drawbacks of autogenous bone graft and allograft. Although these materials provide a solution to some of the aforementioned issues, the issue of immunogenicity and the transmission of disease had been frequently brought up; as a result, alloplastic materials were produced. These substances, which are artificial, inorganic, and biocompatible bone graft alternatives, offer a potential substitute for the treatment of periodontal disorders. The benefits of these materials include better accessibility, the removal of the requirement for a donor site, and the absence of any risk of disease transmission. In controlled clinical studies, hydroxyapatite (HA) and tricalcium phosphate (TCP), two alloplastic materials, significantly improved clinical outcomes at grafted locations compared to non-grafted sites. Cone beam computed tomography produces 3D images that are required in periodontics for the diagnosis of intra bony defects, furcation involvements, and destructions of the buccal and lingual bones. The objective of this study was to compare the effectiveness of nanocrystalline hydroxyapatite and tricalcium phosphate, both applied on a PRP membrane, in treating Miller's class 1 gingival recession in humans.

Inclusion Criteria:

• Patients with good systemic health and no contraindication for periodontal surgery.
• Patients who are able to maintain good oral hygiene.
• Gingival thickness for the site selected should be ≥1mm.
• The height of keratinized gingiva (HKG) for the site selected should be ≥1 mm (HKG is the distance between the most apical point of the gingival margin and the mucogingival junction).

Exclusion Criteria:

• Active infectious diseases (hepatitis, tuberculosis, HIV, etc….).
• Medically compromised patients.
• Patients taking medications known to cause gingival enlargement.
• Pregnant patients and smokers.
• Previous mucogingival surgery at the defect.
• Restorations or caries in the area to be treated and non vital tooth.
• Teeth which are tilted or rotated.