Oral Irritation Potency of Dentifrices: Comparison Between Two Alternative Assays

Objectives: Ingredients such as sodium lauryl sulfate present in some dentifrices can result in oral irritation. The irritation potency of dentifrices with and without SLS was assessed using the Slug Mucosal Irritation (SMI) assay and in vitro reconstituted human gingival and oral epithelium. Methods: Five commercially available dentifrices were tested blind: Zendium (SaraLee) (A), Elmex (GABA) (B) and 3 SLS containing dentifrices Theramed (Henkel) (C), Signal (Unilever) (D) and Colgate (Colgate) (E). The SMI assay consists of placing 5 slugs twice for 60 minutes on 30% diluted dentifrice. The amount of mucus produced during each treatment was used as a measure for irritation. Tissue damage was estimated by protein and enzyme release (LDH) from the mucosa after each 60-min treatment. Using gingival and oral 3D constructs, the cytotoxic potency of 30% diluted dentifrice was evaluated after 10, 60 and 180 min exposure using MTT reduction, IL1α release and histology. Results: Dentifrice A and B resulted in significantly lower mucus production compared to the SLS containing dentifrices. Formulation B induced an increased protein and LDH release whereas formulation A induced no tissue damage. SLS containing dentifrices C, D & E induced mild to moderate tissue damage as was demonstrated by the increased protein (> 100µg/ml.g) and LDH release (> 1U/l.g). Using the gingival epithelium only the SLS containing dentifrices resulted in a significantly increased IL1α release. Using the oral epithelium, dentifrice A resulted in minimal effects whereas B, D and E reduced the viability, increased IL1α levels and induced tissue alterations. Dentifrice C had no effect on the viability but resulted in tissue necrosis and increased IL1 release. Conclusions: The following rank order of increasing irritation potency was established: A < B < C < D ~ E. These results confirm clinical inflammatory effects of SLS in oral care products.