The primary dentition contains 20 teeth. Children develop 10 on the top (upper jaw) and 10 on the bottom (lower jaw), and most kids have the full set by around age 2 to 2½. These teeth are sometimes called baby teeth, milk teeth, or deciduous teeth, and they serve as placeholders and functional tools until the permanent teeth replace them.
Breakdown by Tooth Type
Those 20 primary teeth fall into three categories:
- Incisors (8 total): Four on top and four on the bottom, right at the front of the mouth. These are the flat, thin teeth used for biting into food.
- Canines (4 total): Two on top and two on the bottom, sitting just beside the incisors. These are the pointed teeth that help tear food.
- Molars (8 total): Four on top and four on the bottom, in the back of the mouth. These broader, flatter teeth handle grinding and chewing.
Unlike the permanent set of 32 teeth, primary dentition has no premolars and no third molars (wisdom teeth). The simpler lineup matches a child’s smaller jaw.
When Primary Teeth Come In
The first teeth to appear are typically the lower central incisors, which break through the gum between 5 and 8 months of age. The upper central incisors follow shortly after, usually between 6 and 10 months. From there, teeth generally erupt in pairs, working outward from the center of the mouth.
The last primary teeth to arrive are the second molars, which typically emerge between 20 and 30 months. That said, the American Academy of Pediatric Dentistry notes that many otherwise normal infants don’t follow the standard schedule precisely. Some babies are born with a tooth already visible, while others don’t see their first tooth until after their first birthday. Both ends of that range are usually normal.
Teething Signs to Expect
Some teeth slip through with no fuss at all. Others announce themselves with a cluster of mild symptoms. According to the NHS, common signs include red, sore gums where the tooth is pushing through, a mild temperature (staying below 38°C or about 100.4°F), one flushed cheek, a facial rash, ear rubbing, extra drooling, and increased chewing or gnawing on objects. Babies may also be fussier than usual and sleep poorly during active teething periods.
Why Primary Teeth Matter
It’s tempting to think of baby teeth as disposable since they’ll fall out anyway, but they play several roles that affect long-term health. Primary teeth hold space in the jaw for the permanent teeth developing beneath them. When a baby tooth is lost too early, from decay or injury, neighboring teeth can drift into the gap. That blocks the permanent tooth from coming in straight, often leading to crowding that later requires orthodontic treatment.
Primary teeth are also critical for speech development. Children who lose front teeth early to decay can struggle with sounds like “th” and “la,” and some develop compensatory speech patterns that require therapy to correct. Beyond speech, these teeth let children chew a full range of foods during a stage of life when nutrition directly fuels growth.
When Primary Teeth Fall Out
The shedding process mirrors the eruption order: the first teeth in are the first teeth out. Lower and upper central incisors loosen and fall out between ages 6 and 7, followed by the lateral incisors at 7 to 8. There’s then a bit of a pause before the canines and molars shed between ages 9 and 12. The full timeline, based on American Dental Association data, looks like this:
- Central incisors: shed around 6 to 7 years
- Lateral incisors: shed around 7 to 8 years
- First molars: shed around 9 to 11 years
- Canines: shed around 9 to 12 years
- Second molars: shed around 10 to 12 years
Most children have lost all 20 primary teeth by age 12, at which point the permanent dentition takes over. During the years when both baby and adult teeth are present, the mouth is said to be in a “mixed dentition” stage.
Missing or Extra Primary Teeth
Occasionally, a child develops fewer than 20 primary teeth. This condition, called hypodontia, is rare, affecting less than 1% of children in most populations. The teeth most commonly absent are the upper lateral incisors and the lower central or lateral incisors. A slightly higher rate of about 5% has been documented in Japanese children, suggesting some genetic variation across populations.
If you notice that your child seems to be missing a tooth or has an extra one, a dental exam with X-rays can confirm what’s happening beneath the gums. Both the AAPD and the ADA recommend establishing a child’s first dental visit within six months of the eruption of the first tooth, or by their first birthday, whichever comes first. Early visits catch developmental variations while there’s still time to plan ahead for the permanent teeth.