Biocompatibility (MTT Test) of Over-The-Counter Palliative Sialagogues

Objectives: To compare in vitro biocompatibility to a variety of over-the-counter, palliative sialagogue (OPS) products.
Methods: The pH of commercial OPS products (2 liquid* and 4 lozenges**) were measured (Table): TheraBreath Oral Rinse* (TBOR); Mouth Kote Spray* (MKS); MedActive Oral Relief Lozenges** (MORL); Ludens-Pectic Lozenges** (LPL); Hylamint (Hyaluronic Acid) Lozenge** (HAL); MighTeaFlow Lozenge** (MTFL). Dilutions of phosphate buffered saline (PBS) with media served as control. Liquid products were used as received, lozenges were dissolved in deionized water (1:5 ratio). All solutions were centrifuged at 2000 rpm for 5 min to remove any particulate. Solutions were diluted at 1:1, 1:10, and 1:20 ratios with complete media and pH measured. Dilutions were applied to mouse fibroblast (L929) cells and incubated at 37°C for 72h. N=6/product. Cell mitochondrial succinate dehydrogenase (SDH) activity (MTT testing) was measured on cultures after 72h, and individual plate well results were expressed as a percentage of the appropriate PBS controls. Within a product, percent control values were compared using a 1-way, repeated measures ANOVA. Within a dilution level, percent control values were compared using a 1-way ANOVA. Post-hoc testing by the Tukey test. Pre-set alpha=0.05.
Results: Products demonstrated differences in biocompatibility among dilutions. All solutions, except for HAL (original pH 4.4), showed decreased MTT activity at the 1:1 dilution ratio. At 1:10 dilutions, MTT activity increased above control levels, except for TBOR and MORL. At 1:20 dilution, some MTT values decreased relative to the 1:10 value: MTFL, LPL, and HAL, with MKS and MTFL significantly exceeding control. All products demonstrated significantly higher biocompatibility (greater % control) at 1:20 dilution compared to 1:1, except HAL, which was lower.
Conclusions: Biocompatibility of over-the-counter palliative sialagogues varies significantly, with diluting resulting in increased biocompatibility. MTT activity did not correlate with initial pH of the solutions.