Is nicotine damaging to oral tissues?

Area of Science:

• Oral biology
• Toxicology
• Cell biology

Background:

• Nicotine is a primary component of tobacco products and is used in nicotine replacement therapy (NRT).
• Understanding nicotine's effects on oral cells is crucial for assessing risks associated with various tobacco and NRT products.
• Previous research has yielded mixed results regarding nicotine's impact on human gingival and periodontal cells.

Purpose of the Study:

• To systematically review in vitro studies examining the effects of nicotine on human gingival and periodontal fibroblasts and epithelial cells.
• To determine safe concentration thresholds for nicotine exposure in oral cells based on levels found in different user groups.

Main Methods:

• A systematic review of 42 pre-clinical in vitro studies published between 1995 and 2017.
• Studies assessed nicotine's impact on cell viability, attachment, proliferation, and inflammatory mediator production.
• Data synthesis involved a narrative approach, with quality assessment focusing on in vitro study design limitations.

Main Results:

• Nicotine did not affect cell viability at concentrations found in smokers and NRT users (including e-cigarettes).
• Adverse effects on cell viability occurred only at concentrations exceeding those in smokeless tobacco users' saliva (>5 mM).
• Observed effects on cell attachment, proliferation, and inflammation were contradictory across studies and concentrations.

Conclusions:

• Nicotine is unlikely to be toxic to human gingival and periodontal ligament cells at concentrations typical for smokers and NRT users.
• Higher nicotine concentrations, as found in smokeless tobacco, demonstrate in vitro cytotoxicity.
• Further high-quality in vitro research is recommended to clarify nicotine's effects on oral cells.