Why must tartar be removed?

The significance of tartar is that on a microscopic level, it is quite porous meaning that it attracts and allows plaque to adhere to it. As more plaque adheres to the tartar surface, it again  can calcify and allow the tartar deposit to continue growing in size, synonymous with a snowball rolling down a mountainside. And as bacteria in plaque produce toxins, acids and other by products , these can cause detrimental affects in humans.  Such adverse affects include bad breath, tooth decay, swollen and bleeding gums, and eventually, loosening and loss of teeth. It therefore makes sense to remove tartar, so as to reduce the amount of  bacteria accumulating in the mouth and restore health to the gum and supporting tissues. This highlights the need to have your teeth and gums professionally cleaned periodically ( usually every six months ).