Milk teeth replacement. Close-up of the mouth of a seven year old girl, showing milk teeth and erupting adult teeth. The milk (deciduous) teeth are impermanent teeth which are replaced as adult teeth appear. Here, gaps in the tooth rows show places where the milk teeth have been lost. There are 20 such milk teeth, 10 in each jaw, consisting of 2 molars on each side, one canine (eye tooth) each side, and four incisors across the front. Between 6 and 12 years of age both adult and milk teeth are present, forming a mixed dentition as is evident in this upper tooth row. The set of 32 adult teeth (the permanent dentition) including wisdom teeth are finally present by age 21.