The main job of a dental hygienist is to give you the advice and ability to maintain healthy teeth and gums at home. Plaque is a film of bacteria which forms every day on the surface of the teeth and gums. Plaque builds up on the teeth when the brushing and flossing technique used has not removed it all efficiently enough. When plaque remains on the teeth for a period of time it hardens and this is then known as calculus or tartar. This accumulation of hard calculus or tartar can only be removed with a professional dental clean, so the hygienist will remove these build-ups and advise you how to clean your teeth effectively to help avoid these hard build ups in the future.