Amazon calculates a product's star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
I am a big fan of the Colgate Natural Extracts category. Charcoal acts like a perfect natural teeth whitener with antibacterial properties, removing plaque and strains. Results are quite impressive, thumbs up!