The age is determined according to the following criteria:
About 20 days: Start teething.
4~6 weeks old: deciduous teeth have long incisors.
Nearly 2 months old: all deciduous teeth are long white, thin and pointed.
2~4 months old: replace the first deciduous incisor.
5~6 months: change the age of the second and third breast doors and canine teeth.
After 8 months: all permanent teeth were replaced.
1 year: the permanent teeth are long, white and bright, and the front teeth have sharp protrusions.
1.5 years old: the big peak of mandibular first incisors wears to the level of small peak, which is called peak wear.
2.5-year-old: peak wear of mandibular second incisors.
3.5 years old: The first maxillary incisor has lost its peak.
4.5 years old: The second maxillary incisor has lost its peak.
5 years old: The peak of the third mandibular incisor is slightly worn, and the worn surfaces of the second and second mandibular incisors are rectangular.
6-year-old: the third mandibular cusp has blunt canine teeth.
7-year-old: The first mandibular incisor was worn to the root, and the worn surface was vertical oval.
8-year-old: the first mandibular incisors are worn forward.
10 years old: the worn surfaces of the mandibular second incisors and the maxillary first incisors are vertical ellipses.
16 years old: the front teeth fall off and the dog's teeth are incomplete.