Deciduous teeth, commonly called baby teeth or primary teeth, are the first set of 20 teeth that develop during infancy and early childhood. They begin appearing around 6 to 8 months of age and are gradually replaced by 32 permanent teeth starting around age 6. Though temporary, they play essential roles in a child’s ability to eat, speak, and develop properly aligned adult teeth.
How Many Deciduous Teeth and What Types
Children develop 20 deciduous teeth in total: 10 on the upper jaw and 10 on the lower jaw. Each half of each jaw contains five teeth, broken down into three types:
- Incisors (8 total): Four central incisors and four lateral incisors, the flat front teeth used for biting into food.
- Canines (4 total): The pointed teeth next to the incisors, used for tearing food.
- Molars (8 total): Four first molars and four second molars, the broad back teeth used for grinding and chewing.
Notably missing from the baby set are premolars and third molars (wisdom teeth), which only appear in the permanent dentition. This is why children have 20 teeth compared to the typical 32 in adults.
When Each Tooth Comes In
Deciduous teeth erupt between roughly 4 and 36 months of age. The process follows a fairly predictable sequence, though the exact timing varies from child to child. Lower teeth tend to appear slightly before their upper counterparts.
The lower central incisors usually come in first, around 7 to 8 months on average. Upper central incisors follow at about 9 months, then the lateral incisors at 10 to 12 months. First molars arrive around 15 to 16 months, canines at 17 to 18 months, and second molars last at roughly 23 to 25 months. By age 2 to 3, most children have a complete set of 20 primary teeth.
These are averages. Some babies cut their first tooth as early as 3 months, while others don’t see one until after their first birthday. Both ends of that range are normal. The sequence matters more than the exact timing, so if teeth are arriving in roughly the expected order, there’s rarely cause for concern even if they’re running a few months behind.
Why Baby Teeth Matter More Than You’d Think
Because they eventually fall out, it’s easy to assume baby teeth aren’t especially important. They are. Deciduous teeth serve four critical functions during a child’s development.
First, they make proper nutrition possible. Children need to chew a widening range of solid foods throughout toddlerhood, and primary teeth are what allow them to break food down enough for digestion. Second, they’re essential for speech. The position of the front teeth in particular helps children learn to articulate sounds and form words correctly. Kids who lose front teeth early or have significant decay sometimes develop speech patterns that require therapy to correct.
Third, baby teeth act as space maintainers for the permanent teeth forming inside the jawbone. Each deciduous tooth holds its spot in the arch, guiding the adult tooth beneath it into the correct position. When a baby tooth is lost too early, neighboring teeth can drift into the gap, potentially crowding or blocking the permanent tooth trying to come in. Fourth, primary teeth support the muscles and soft tissue of the face, contributing to normal facial structure during early growth.
How Baby Teeth Differ From Adult Teeth
Deciduous teeth are smaller versions of permanent teeth, but the differences go beyond size. Their enamel, the hard outer coating that protects against decay, is significantly thinner than on permanent teeth. This is one reason cavities in baby teeth can progress quickly. The layer beneath the enamel is also thinner, meaning decay reaches the nerve inside the tooth faster than it would in an adult tooth.
The pulp chamber, the inner space containing nerves and blood vessels, is proportionally larger in baby teeth relative to the overall tooth size. This makes them more sensitive to deep cavities and infection. The roots of deciduous teeth are also shaped differently: they’re thinner and more spread out, which creates space for the developing permanent tooth buds nestled between and below them.
How Baby Teeth Fall Out
The process of losing a baby tooth starts long before it feels loose. As a permanent tooth develops and begins pushing upward (or downward, in the upper jaw), specialized cells gradually dissolve the root of the deciduous tooth above it. This process, called root resorption, breaks down the hard root tissue piece by piece while also clearing away the soft tissue inside the tooth, including the nerve and the ligament anchoring it to the bone.
The process isn’t constant. It happens in cycles of breakdown and partial repair, which is why a loose tooth can seem to tighten up again before eventually becoming loose once more. Chewing forces on the baby tooth also play a role, sending mechanical signals that accelerate the breakdown. Eventually, so much of the root has been resorbed that only the crown remains, attached by a thin thread of tissue. At that point, it wiggles free or falls out on its own.
Baby teeth generally fall out in the same order they arrived. The lower central incisors go first, typically around age 6, followed by the upper central incisors, then lateral incisors, first molars, canines, and finally second molars. Most children lose their last baby tooth between ages 11 and 13.
What Happens When Baby Teeth Are Lost Too Early
Premature loss of a deciduous tooth, whether from decay, injury, or extraction, can affect how the permanent teeth come in. The concern is that neighboring teeth will shift into the empty space, narrowing the gap the adult tooth needs. Several factors influence whether this actually causes problems: the child’s age at the time of loss, which tooth was lost, how far along the permanent tooth is in development, and the child’s overall jaw growth.
Research on premature loss of first molars has found that in many cases, the permanent teeth still come in without significant crowding. One long-term study followed children for nearly seven years after early loss of an upper first molar and found that about 89% had no crowding or blocked permanent teeth at the extraction site. Dentists sometimes place a space maintainer, a small device that holds the gap open, but the decision depends on the specific tooth and the child’s developmental stage rather than being automatic.
Back molars are generally a bigger concern than front teeth when lost early, because the teeth behind them are more likely to drift forward and close the gap. Early loss of front teeth is less likely to cause spacing issues for permanent teeth, though it can temporarily affect speech.
Caring for Deciduous Teeth
The American Academy of Pediatric Dentistry and the American Dental Association both recommend scheduling a child’s first dental visit within 6 months of the first tooth appearing, and no later than 12 months of age. This early visit focuses on checking development, discussing feeding habits, and establishing a prevention routine rather than any treatment.
Because baby tooth enamel is thinner and more vulnerable than adult enamel, daily cleaning matters from the start. For infants, wiping the gums with a soft cloth after feeding helps. Once teeth appear, a small smear of fluoride toothpaste on a soft-bristled brush is appropriate. For children under 6, brushing with fluoride toothpaste should be supervised to make sure they’re using only a small amount and not swallowing it. Cavities in baby teeth are worth treating even though the teeth will eventually fall out, because untreated decay can cause pain, infection, and damage to the developing permanent teeth underneath.