Tartar forms on teeth when you fail to remove plaque from your teeth. Plaque is the sticky residue of food debris combined with the bacteria that feed on that debris. In general, brushing your teeth twice a day should ensure that you keep tartar at bay, for the most part. However, if you fail to remove plaque from an area of your teeth 12 days in a row, that plaque becomes tartar.
24 September 2019