Tea tree oil (Melaleuca alternifolia) has been studied for its antimicrobial and anti-inflammatory properties, which are relevant to the pathogenesis of gingivitis—a common inflammatory condition of the gums caused by bacterial biofilms. Several clinical trials and in vitro studies have investigated its potential role in oral health, particularly in reducing gingival inflammation and microbial load.

Randomized controlled trials have shown that tea tree oil-containing gels and mouth rinses can lead to a reduction in gingival bleeding and inflammation compared to placebo, though results on plaque reduction are inconsistent. For example, a double-blind study published in the Australian Dental Journal (2004) demonstrated that a tea tree oil gel significantly reduced gingivitis indices over 4 weeks, although it did not significantly affect dental plaque scores. Other small studies support these findings but highlight variability in outcomes, likely due to differences in product formulation and study design.

Tea tree oil’s efficacy is generally attributed to its active components, such as terpinen-4-ol, which exhibit broad-spectrum antimicrobial activity against oral pathogens implicated in gingivitis. Adverse effects, primarily allergic reactions or irritation, are possible and limit its widespread use in oral care products.

In summary, there is moderate scientific evidence (rated 3/5) supporting the adjunctive use of tea tree oil for reducing gingival inflammation, though it is not considered a replacement for conventional oral hygiene practices.