The Evaluation of Sodium Lauryl Sulphate in Toothpaste on Toxicity on Human Gingiva and Mucosa: A 3D in vitro Model

Abstract

Five different commercial toothpaste formulations were labeled as A, B, C, D and E and evaluated for toxicity in vitro using reconstituted human oral and gingival mucosa cultures. Toothpastes A, D and E contained sodium lauryl sulphate (SLS) while toothpastes B and C did not. All toothpastes contained fluoride in different quantities. Tissue viability (MTT), tissue morphology (LM and TEM) and release of pro-inflammatory mediator IL-1α were evaluated. For gingival mucosa, topical exposure of toothpastes did not affect MTT values. Examination of oral mucosa however, showed that toothpastes B, E and D induced a significant loss of viability after 1 h (49.2%, 55.5% and 78.4% respectively) (p<0.05). After 3 hours toothpaste B demonstrated a 51.4% loss of viability whereas tissue viability for toothpastes D and E dropped to 11.1% and 4.5% respectively. The release of pro-inflammatory mediator IL-1α showed that only gingival mucosa tissues exposed to toothpaste D and E showed a marked increase of IL-1α after 1 hour, and toothpaste A, D and E after 3 h exposure. Oral mucosa tissue exposed for 1 h resulted in increased levels of IL-1α for toothpastes A, B, D and E, which became more important at 3 h. Morphological analysis of the oral mucosa demonstrated partial necrosis after exposure to toothpastes A, B and C, and severe necrosis to D and E. MTT cannot be used as single toxicity parameter and should be confirmed by histology. Both in vitro oral and gingival mucosa models are suitable to evaluate the toxicity of toothpaste formulations. The presence of SLS in toothpaste formulations is presumably responsible for the toxicity observed in vitro. MTT, IL-1α release and morphology were affected by the SLS containing toothpastes A, D and E. These observations confirm clinical inflammatory effects of SLS in oral care products often reported in literature.