For adult Yorkshire Terriers, importance is placed on coat colour, quality, and texture. The hair must be glossy, fine, straight, and silky. Traditionally the coat is grown out very long and is parted down the middle of the back, but 'must never impede movement. Sometimes the number of permanent or adult teeth may vary, which is fine as long as they do not cause bad bite. When puppies are born, they have no teeth because milk is the only food they need. The deciduous teeth will grow from the age of 3 to 8 weeks old, in the order of incisors, canines, and premolars. Yorkie puppies have no molar teeth.