The physical characteristics of dental kibble are very important as they contribute to the mechanical cleaning of the tooth's surface.[1] The kibble need to be large and very dense to promote chewing, as more time spent chewing will aid in the decrease of accumulation of plaque, tartar and calculus.[21] When the kibble is being chewed, the broken pieces rub against the tooth's surface and scrape off the buildup of bacteria that forms the tartar, plaque and calculus.[22] Ingredients that have an adequate amount of carbohydrates and are high in insoluble fibers (typically around 10%), such as soy fiber, wheat bran fiber or cellulose fiber, are added to increase the density of the kibble to assure it does not easily crumble and promotes a texture favourable to scraping of the tooth.[2][23] Increasing the diameter will also significantly reduce the accumulation of plaque and calculus compared to traditional dog food as it will require more chewing by the molars.[5] Traditional hard kibble will not have the same effects on oral health as it has been proven that the increase in fiber and diameter is what provides those benefits in the diet.[14] A disadvantage is that the mechanical cleansing is more beneficial for the molars compared to the incisors and canines.[14] The incisors and canines are typically used for grabbing and tearing, whereas the molars are used for crushing and chewing, so most of the contact with the broken kibble is in the back of the mouth.[14] The physical characteristics and chemical agents of the kibble work together to delay the buildup of plaque, and are both equally important to the cleansing of the dog's teeth.[14]