Periodontal Indices and Cytokines of Ex-Smokers/Non-Smokers After Bleaching

Background/Objectives: Smoking is known to modulate the periodontal inflammatory response, and dental bleaching agents can transiently alter local and systemic cytokine levels. The aim of this study was to evaluate cytokine levels in both saliva and gingival crevicular fluid (GCF) in non-smoking and ex-smoking patients, before and after in-office dental bleaching performed using chemically activated or diode-laser-activated protocols. Methods: This prospective, longitudinal, split-mouth clinical study included 40 participants allocated to two smoking-status groups (non-smokers and ex-smokers, cessation ≥ 5 years). For each participant, one maxillary hemi-arch received chemically activated bleaching and the contralateral side received diode-laser-activated bleaching, applied in two sessions one week apart. Plaque index (PI), gingival index (GI), and bleeding index (BI) were recorded, and IL-6 and TNF-α levels were measured in saliva and GCF using ELISA at baseline, after each session, and two weeks after treatment. Results: A non-significant increase was observed in GI and BI after two weeks compared with baseline (p > 0.05), while a significant decrease was observed in PI in the ex-smoker group (p < 0.05). A transient increase in TNF-α and IL-6 levels was observed in saliva and GCF samples following bleaching, and TNF-α/IL-6 levels were consistently lower in the ex-smoker group across all measurements. Conclusions: Bleaching was associated with a temporary alteration of periodontal indices and cytokine levels irrespective of smoking history. Smoking history was independently associated with lower cytokine levels, regardless of bleaching application, supporting the relevance of considering smoking history when interpreting the inflammatory impact of bleaching activation methods.