The interdental brush has a quadrangular shaped handle portion with an angled brush head portion with a brush head cartridge attached at one end and a removable brush head holder at the other end. The brush head can fit in a contra-angle arrangement or co-directional arrangement to the angle of the handle...http://www.google.es/patents/US5896615?utm_source=gb-gplus-sharePatente US5896615 - Interdental brush
