The baby (deciduous) teeth begin to appear (erupt) at about 2 ½ weeks of age and are completely in by 6 weeks. Kittens begin to lose their baby teeth at about 3 1/2 months of age, just before the permanent teeth begin to appear. By 6 to 7 months of age. All the permanent teeth will have erupted by 6 months of age. The types of teeth are incisors, canines (fangs), premolars and molars. Cats have 26 baby teeth and 30 permanent teeth.