The Effect of Periodontal Treatment on Tongue Coating and Olfactory Functions in Patients With Periodontitis

Periodontitis is a multifactorial chronic inflammatory disease caused by dental plaque, characterized by connective tissue destruction, periodontal pocket formation, and alveolar bone loss. Pathogenic bacteria associated with periodontitis and the host inflammatory response contribute not only to periodontal tissue breakdown but also to oral malodor (halitosis) and disruption of the oral microbiota. Progressive periodontal inflammation promotes the formation of a dense biofilm on the dorsum of the tongue, containing bacterial products, keratinized epithelium, and protein residues. This leads to increased tongue coating, which serves as a primary source of volatile sulfur compounds (VSCs) strongly associated with halitosis.

The Winkel Tongue Coating Index (WTCI) is commonly used to assess tongue coating and is an important clinical indicator for both halitosis and periodontal status. The bacterial load on the tongue also acts as a reservoir, contributing to dysbiosis of the oral microbiota in periodontitis patients.

Recent studies have also highlighted a potential relationship between periodontitis and olfactory function. Proinflammatory cytokines released during periodontal inflammation, such as IL-1β, TNF-α, and IL-6, may negatively affect the olfactory epithelium, leading to impaired odor threshold, discrimination, and identification abilities. Olfactory function is commonly evaluated using the Sniffin' Sticks test, which includes three subtests: odor threshold, odor discrimination, and odor identification. The sum of these tests, known as the TDI score, reflects overall olfactory capacity.

Previous studies have shown that periodontal treatment can improve tongue coating and halitosis. However, studies simultaneously evaluating pre- and post-treatment tongue coating indices, periodontal indices, and olfactory function (TDI scores) are limited. The aim of this study is to compare these parameters before and after periodontal treatment in patients with periodontitis and to investigate the effect of periodontal therapy on olfactory function.

This study was approved by the Batman University Interventional Clinical Research Ethics Committee (Approval No: 2024/08-04). All procedures and data collection were conducted in accordance with the Declaration of Helsinki, and all participants provided written informed consent.