Baby (Primary) Teething Guide: From the First Tooth Until All 20 Are In

According to the Korea Disease Control and Prevention Agency (KDCA, 질병관리청), baby teeth start coming in around 6 months with the lower central incisors, all 20 are in by age 2-2.5, and the eruption order differs from child to child. Around 30-41 months, when all the baby teeth are settled, the second national oral checkup lets the whole primary dentition be checked. Teething a little earlier or later than peers is a common individual difference, but if teeth come in on one side and the opposite side is long delayed, a dental check is needed.

Published 2026-11-08 · Updated 2026-11-08 · DentalStatics editorial team

Key facts

First baby tooth	Around 6 months, starting with the lower central incisors (source: Korea Disease Control and Prevention Agency (KDCA))
When all baby teeth are in	Age 2-2.5, 20 teeth in total (source: Korea Disease Control and Prevention Agency (KDCA))
Eruption order	Differs from person to person (source: Korea Disease Control and Prevention Agency (KDCA))
Oral checkup when the primary dentition is complete	30-41 months (added June 30, 2022) (source: Ministry of Health and Welfare)
How to clean	Damp gauze before teeth come in, an infant toothbrush after (source: Korea Disease Control and Prevention Agency (KDCA))

When do baby teeth come in, and in what order?

The first baby tooth usually starts around 6 months with the lower central incisor. The remaining incisors, molars and canines then come up at different times, and by age 2-2.5 all 20 teeth, upper and lower combined, are settled.

The KDCA explains that the order in which baby teeth come in differs from person to person. Sometimes the upper front teeth appear before the lower ones, or several come up at once, so there is no need to worry if it differs slightly from the textbook order.

How does a baby behave when teeth are coming in?

While a tooth pushes up through the gum, a baby may drool a lot, put hands and toys in the mouth and chew on them often, and be fussier or sleep worse than usual. The gum may look red and swollen, or the white tip of the tooth may show through.

Giving a clean teething ring or gently pressing the gum with a clean finger can ease the discomfort. However, if high fever, diarrhea or severe lethargy continues, it is safer to see a pediatrician rather than put it down to teething.

During teething, drool makes rashes around the mouth and chin likely, so wiping often with a soft cloth is good. Chewing force grows, and some babies bite during breastfeeding, so gradually changing the feeding position during this time is one approach.

Should you worry if baby teeth come in late?

The timing of baby teeth varies widely between individuals, so a first tooth coming a few months later than peers is not treated as a problem by itself. However, if other development is also delayed, or if a tooth has come in on one side of the same jaw but the matching spot on the other side is long delayed, the dentist checks the teeth inside the gum.

Having fewer than 20 baby teeth, or teeth that look unusually small and pointed, is also a reason for a dental consultation. The infant oral checkup also looks for tooth abnormalities as a target condition, so ask your questions at the checkup.

When one side has come in and the opposite side is long delayed
When a bluish swollen pocket forms on the gum
When pus or heavy bleeding is seen where a tooth is coming in

How should you clean once teeth start coming in?

The KDCA recommends starting oral care at 6-12 months, when baby teeth start to come in. Before teeth come in, wipe the gums with damp gauze, and when teeth come up, switch to an infant toothbrush.

The guidance advises using fluoride toothpaste after consulting a dentist at around 9-12 months. From this period, build the habit of not letting the baby fall asleep with a bottle and always finishing with brushing after the last feeding before sleep.

What should you take care of after all the baby teeth are in?

The 30-41 month oral checkup was added on June 30, 2022 to help manage cavities as the primary dentition is completed. Once all 20 baby teeth are in, the molars touch each other and trap food easily, so start using floss.

The KDCA's infant checkup guidance advises brushing twice a day with a rice-grain-sized amount of toothpaste at 18-41 months and giving drinks in a cup. Once the molars are in, a caregiver should finish the brushing so that the brush also reaches the grooves on the chewing surfaces.

Common myths and facts

Myth: A high fever during teething is normal.

Fussiness and drooling are common when teeth come in, but if high fever or diarrhea continues there may be another cause, so seeing a pediatrician is safer.

Myth: Baby teeth must come in in a set order.

The KDCA explains that the order differs from person to person. It helps more to see whether left and right come in at similar times than to follow the order.

Frequently asked questions

What if the first baby tooth has not come in after the first birthday?

The timing of baby teeth varies widely, and some children come in late. If other development is normal, have the teeth inside the gum checked at an infant checkup or dental visit and watch how it goes. Even if teeth come in late, do not put off wiping the gums with damp gauze; continue from now.

Are some babies born with teeth?

Rarely, a baby has a tooth visible at birth or soon after. If it interferes with feeding or is loose, there is a risk of swallowing it, so have the dentist check it.

Can I use a gum medicine when teeth are coming in?

Products applied to a baby's gums need caution depending on ingredients, so consult a doctor or pharmacist before use. You can try non-drug methods first, such as a chilled teething ring.

There are gaps between my baby's teeth. Is that okay?

Gaps between baby teeth are common, and they can become room for the larger permanent teeth later. Conversely, if teeth are packed with no gaps, food gets trapped easily and floss needs to be used more carefully.

Should we get a dental checkup before all the baby teeth are in?

The first national oral checkup is at 18-29 months, so you take it before all baby teeth are in. At this checkup, brushing and feeding habits are reviewed, and they are checked again at the 30-41 month checkup when the baby teeth are complete.

References

Korean version →