It keeps teeth clean Cleaning. A toothpaste's cleaning ability depends on its prowess at removing surface stains. To test cleaning ability, we cut sections of cow's teeth, lightly etched them, and soaked them in a murky mix of food, drink, bacteria, and chemicals to amass a dark-brown stain. A brushing machine delivered hundreds of strokes with a measured amount of toothpaste and water. Toothpastes that were the best cleaners did an excellent job.
All toothpastes contain abrasives to clean tooth surfaces.
Modern toothpastes can consist of 25 to 50 percent abrasives. Dry baking soda is a gentle abrasive, but it also quickly dissolves and loses its abrasiveness. It offers no therapeutic value, according to the dentists we spoke with. Tooth enamel can take pretty rough abrasives, but dentin, a softer tissue that's exposed as gums recede, can be damaged by toothpaste that's too abrasive. To test abrasiveness, we used the toothpastes on extracted human teeth in a standard machine-brushing setup and assayed how much dentin came off.