The interdental papilla is a crucial part of an esthetic smile, its loss results in gingival black triangles giving unpleasant appearance which directly affect patient self-esteem (Lee et al. 2016). The presence of interdental papilla is of great concern for the clinician and the patient. Gingival black triangles are considered to be the most disliked esthetic issue. As well open embrasures can cause food impaction and phonetic problems (Prato et al. 2004).

The treatment of black triangles is challenging in modern dentistry. The treatment options are surgical and non-surgical. Surgical treatments are invasive and do not always give a predictable result due to limited blood supply of the papilla (Mansouri 2013).

However, no technique has been set up as a gold standard treatment for gingival black triangles, although, connective tissue graft surgical techniques are the most common used approaches for treatment of black triangles (RahimiRad 2018).

A modern, non-surgical method for treating papillary deficiencies is the use of hyaluronic acid, which have demonstrated encouraging outcome (Ni et al. 2021). Subperiosteal hyaluronic acid injection overlay technique was proposed by Spano et al, (2020) with the idea of merging hyaluronic acid injection with simple surgical intervention to reconstruct the lost interdental papilla. As far as we know, there is no present studies comparing hyaluronic acid overlay technique with connective tissue graft in treatment of interdental papilla deficiencies.

The interdental papilla is an important anatomical part of the gingiva. It can reduce by time or by different etiological factors as crown shape or presence of periodontal diseases which results in presence of highly unaesthetic black triangles which frequently cause patients complaints in both appearance and function (Patel et al. 2024). The interdental papilla is a part of the gingiva that fills the embrasure space between the contact point of the adjacent teeth. It is supported by the underlying alveolar bone and laterally by the presence of the teeth. It is composed of masticatory mucosa and composed of dense connective tissue covered with oral epithelium (Prato et al. 2004).

Tarnow et al (1992) investigated a relationship between the distance of interdental bone level and contact point and the presence or absence of the interdental papilla. They found that a distance of 3-4 mm, an intact interdental papilla was present. While, when the distance increased to 6 mm and above, there was partial or complete absence of the interdental papilla and the absence of the papilla increased with every millimeter. The interdental papilla can be lost due to interproximal bone loss due to periodontitis or may be iatrogenic damage such as over-countered restorations and crown preparations. In addition, tooth-related factors can cause loss of interdental papilla as loss of contact point, tooth malposition, abnormal tooth shape, triangular-shaped crowns, diastamas, divergent roots and over-eruption of a tooth (Kurth and Kokich 2001).

Nordland and Tarnow (1998) proposed a classification for the loss of interdental papilla which is based on three references: the contact point, buccal apical extent of the cemento-enamel junction (CEJ) and the interproximal CEJ. The classification follows: Normal: when the interdental papilla fills the embrasure space to contact point, Class I: the tip of the papilla lies between the interdental contact point and the most coronal extent of CEJ, Class II: the tip of the papilla lies at or apical to the interdental CEJ but coronal to facial CEJ and Class III: when the tip of the papilla lies at a level apical to the facial CEJ.

Different surgical and non-surgical techniques have been proposed for treatment of interdental papillary deficiency based on the etiological factor with some of degree of success. Among these treatments are the correction of traumatic oral hygiene practices, papilla enhancement with either autologous fibroblast injection or hyaluronic acid and orthodontic therapy (Singh et al. 2013). Among surgical approaches to reconstruct the lost papilla are connective tissue graft base surgical techniques. The surgical treatment of deficient papilla with the connective tissue graft remained the most used approach however, it requires a good vascular supply in the interdental papilla and requires a second surgical site (Gobbato et al. 2016).

Hyaluronic acid injection in the deficient interdental papilla has shown promising results (Fakhari and Berkland 2013; Lee et al. 2016; Ni et al. 2021). Hyaluronic acid is a polysaccharide present in the body tissues. Under physiologic conditions it binds to water and swells in a gel form, resulting in smoother tissue counters. The role of hyaluronic acid in augmentation is by inducing water absorption of gingival fibroblast proliferation. When hyaluronic acid is incorporated into an aqueous solution, hydrogen bonding occurs between adjacent carboxyl and N-acetyl groups; this feature allows hyaluronic acid to maintain conformational stiffness to retain water (Bertl et al. 2017). Also, it may affection collagen remodeling by increasing the production of procollagens and matrix metalloproteinase-1 secretion by fibroblast (Singh et al. 2013). Hyaluronic acid showed a satisfactory result in regeneration of lost interdental papilla at 6 and 12 months (Ficho et al. 2021).

Inclusion Criteria:

- 1. Patients aged over 18 years. 2. Class I papillary recession according to the Nordland and Tarnow classification system. (Nordland and Tarnow 1998) 3. Patients free from any systemic conditions that may affect healing. (Hamadeh et al. 2024).

4. The distance between the contact point to alveolar crest between 5 to 7 mm. 5. Presence of the adjacent teeth. 6. Compliant patients with good oral hygiene.

Exclusion Criteria:

- 1. Smokers. 2. Pregnant females. 3. Patients with active periodontal disease. 4. Patients who has spacing or crowding between the teeth to be treated. 5. Abnormal tooth shape or adjacent teeth with caries. 6. Presence of proximal restoration or orthodontic appliances or fixed prosthesis.

7. Patients with poor oral hygiene according to plaque index score of 2.0 to 3.0 evaluated according to the criteria of Silness and Loe.