Topical Hyaluronic Acid Adjunctive Effects on Healing After Free Gingival Grafting in Smokers and Non-Smokers

The oral mucosa consists of three main components: (1) masticatory mucosa, (2) specialized mucosa, and (3) lining mucosa. The masticatory mucosa is a keratinized tissue covering the gingiva and the hard palate. The gingiva itself can be classified into three distinct regions: (1) free gingiva, (2) interdental gingiva, and (3) attached gingiva. The free gingiva is composed of oral epithelium, oral sulcular epithelium, and junctional epithelium. Both the oral epithelium, interdental gingiva, and attached gingiva are keratinized tissues.

Keratinized gingiva can be histologically divided into the following cell layers based on the degree of keratin-producing cell differentiation:

Stratum basale (or stratum germinativum)

Stratum spinosum

Stratum granulosum

Stratum corneum

The absence of keratinized gingiva is classified under mucogingival deformities. These deformities represent deviations from the normal dimensional and morphological relationship between the gingiva and the alveolar mucosa and can often have negative esthetic and functional implications for patients. The lack of keratinized gingiva is addressed separately within mucogingival conditions.

In cases where patients present with a thin gingival biotype, inflammation and gingival recession can further reduce the protective capacity of the tissue, creating clinical scenarios in which mucogingival therapy should be considered. Lang and Löe suggested that an apico-coronal width of keratinized gingiva of less than 2 mm is insufficient to maintain gingival health. Today, the presence of attached gingiva is regarded as crucial for maintaining periodontal health. From a periodontal perspective, keratinized gingiva serves two primary functions:

Providing mechanical resistance against functional forces.

Offering a stable surface for toothbrushing, thus facilitating plaque control.

The 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions concluded that, although a minimum amount of keratinized tissue may not be required to prevent attachment loss when optimal plaque control is achieved, approximately 2 mm of keratinized tissue and 1 mm of attached gingiva around the teeth is considered necessary to maintain periodontal health.

The Free Gingival Graft (FGG) procedure, first described by Björn in 1963, is a surgical technique developed to increase the dimensions of keratinized tissue around teeth and prevent gingival recession. This method remains one of the most commonly employed approaches for augmenting keratinized gingiva. However, over time, transplanted tissue can undergo horizontal and vertical dimensional changes. This makes the long-term volumetric stability of keratinized gingiva after FGG procedures critical. Postoperative graft shrinkage is considered a clinical phenomenon that mainly occurs during the early healing phase.

During FGG surgery, a graft is harvested from the palatal donor site, which is then left to heal by secondary intention. The most frequently observed postoperative complications at the donor site include pain, burning sensation, delayed wound healing, and associated difficulties in eating. Over the years, various hemostatic agents, periodontal dressings, platelet-rich fibrin, and analgesics have been used to reduce these complications and support healing; however, no ideal material has been identified in the literature.

The mechanisms by which smoking affects periodontal status are not fully understood, but numerous potential pathways have been discussed in the literature, including effects on the oral microbiota, gingival tissues, inflammatory and immune responses, and the healing capacity of the periodontium. Although smoking does not directly influence plaque accumulation, it is widely accepted that it can impair various aspects of the innate immune response. In periodontitis, the balance between plaque and immune response may shift toward exaggerated tissue destruction, meaning that even a small amount of plaque can lead to disproportionate breakdown.

Evidence suggests that, in smokers, the function and adhesion of gingival and periodontal ligament fibroblasts may be compromised, collagenolytic activity may increase, and collagen production may decrease. Additionally, the suppression of gingival inflammation, reduction in bleeding on probing, and decreased gingival bleeding seen in smokers are not due to vasoconstriction of the gingival vasculature but rather to reduced angiogenesis within the tissues.

For these reasons, mucogingival problems are more prevalent among smokers, with a clear dose-response relationship. Smoking may also negatively impact both the short- and long-term success of periodontal plastic surgery procedures. As a result, the expected dimensions of keratinized gingiva at the recipient site may not be achieved, and smokers may face a higher risk of postoperative complications.

In a study smoking did not appear to have a noticeable impact on postoperative dimensional changes of FGG, it was shown to reduce postoperative bleeding and delay epithelialization, ultimately slowing donor site wound healing.

Hyaluronic acid (HA) is a high-molecular-weight, non-sulfated polysaccharide of the glycosaminoglycan family, found in various body fluids such as synovial fluid, serum, saliva, and gingival crevicular fluid. HA is present in all periodontal tissues-at higher concentrations in non-mineralized tissues like the gingiva and periodontal ligament and at lower levels in mineralized tissues like cementum and alveolar bone. HA is synthesized by mesenchymal cells such as fibroblasts, chondrocytes, and osteoblasts at the cell membrane.

Because HA is highly biocompatible and non-immunogenic, it has bacteriostatic, fungistatic, anti-inflammatory, anti-edematous, osteoinductive, and pro-angiogenic properties, contributing to wound healing in various tissues. These properties have made HA an attractive adjunct in fields such as orthopedics, ophthalmology, and dermatology for treating a range of conditions.

In dentistry, HA has been applied to accelerate healing in extraction sockets, treat temporomandibular joint osteoarthritis, maintain space in sinus lift procedures without grafting, and relieve pain associated with recurrent aphthous ulcers. In periodontology, HA has been proposed for use either as a monotherapy or as an adjunct to non-surgical and/or surgical periodontal therapy to reduce inflammation and support wound healing.

To the best of our knowledge, there is no study in the literature evaluating the potential effects of HA on VAS scores and healing outcomes specifically in smokers undergoing FGG surgery.