# Eruption Timeline of Teeth in Children

> Eruption timeline of primary and permanent teeth — BDS Pedodontics notes on sequences, chronology, calcification dates and delayed eruption clues.

- Canonical URL: https://prepelephant.com/topics/bds/pedodontics/eruption-timeline-pedo
- Exam / course: BDS · Subject: Pedodontics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Eruption Timeline of Teeth in Children", PrepElephant, https://prepelephant.com/topics/bds/pedodontics/eruption-timeline-pedo

## Direct answer

A child's mouth fills to a predictable timetable: primary teeth begin at about six months with the mandibular central incisors, follow the A-B-D-C-E sequence — central incisor, lateral incisor, first molar, canine, second molar — and complete twenty teeth by two and a half to three years. The permanent dentition opens with the first molar at about six years, the famous "six-year molar" whose mandibular member begins calcifying at birth, and closes with third molars in the late teens or never. Exfoliation mirrors eruption in reverse from six to twelve years, and departures from these windows — no tooth by the first birthday, a first molar stalled well past seven — are diagnostic clues rather than cosmetic delays.

## What you must remember

- **Primary chronology:** mandibular central incisor about 6-7 months, lateral incisor 8-10, first molar 12-16, canine 16-18, second molar 20-30 months; the mandible precedes the maxilla tooth for tooth, girls run slightly ahead of boys, and textbook tables (Logan and Kronfeld, modified by McCall and Schour) vary a little between authors — quote the range, not a decimal.
- **Sequence over dates:** A-B-D-C-E is the exam answer; the canine erupts after the first molar in the primary dentition, which surprises anyone who memorised the permanent order.
- **In utero calcification:** primary teeth begin mineralising at 3-4 months in utero, mandibular central incisors first; the only permanent tooth calcifying at birth is the mandibular first molar — a one-mark classic.
- **Root completion:** primary roots finish roughly a year to eighteen months after eruption; eruption is not the finish line, which matters for trauma, extrusion and pulpal judgement.
- **Permanent anchors:** first molar 6 years, central incisors 6-8, laterals 7-9, mandibular canine 9-10 but maxillary canine 11-12, premolars 10-12, second molar 11-13, third molars 17-25 or congenitally absent.
- **Permanent sequences:** mandibular 6-1-2-4-3-5-7 (canine before second premolar) versus maxillary 6-1-2-4-5-3-7 (canine last of all) — a favourite sequence-difference viva.
- **Exfoliation:** begins 6-7 years at the mandibular central incisors, driven by the successor follicle and osteoclastic root resorption, finishing with the second primary molars around 10-12 years.
- **Delay red flags:** no primary tooth by 12-18 months warrants radiographs and a medical look (hypothyroidism, Down syndrome, rickets); localised delay suggests an over-retained predecessor, supernumerary tooth or odontoma; cleidocranial dysostosis presents with multiple impacted permanent teeth.

## Reading two delayed-eruption cases

Start with a 15-month-old brought because "she has no teeth". First teeth can legitimately appear as late as 12-15 months in some families, so the examination targets the algorithm: confirm no natal or broken-down teeth, feel for cusp tips through the ridge, and take an occlusal radiograph if nothing is palpable. Bilateral radiolucencies at the crest mean simple maturation delay with review; absent buds mean a development disorder and paediatric referral.

Now contrast an 8-year-old whose right mandibular central incisor exfoliated on time but whose left refuses to budge. Unilateral failure of exfoliation plus absent successor eruption points to a local cause — a mesiodens or odontoma above the follicle, or an ankylosed primary incisor with a missing successor. One occlusal film answers it, and the management is surgical, not hormonal. The third scenario closes the loop: a second primary molar condemned to extraction just as the first permanent molar is unerupted is a space-maintainer decision, because the six-year molar erupts mesially into any vacated saddle within months.

## How exams frame chronology

Theory papers ask for eruption dates of all primary teeth in months and permanent teeth in years — mixing the units loses credibility markers. Sequence questions outrank date questions in MCQs: which primary tooth erupts third (first molar), which permanent tooth calcifies at birth (mandibular first molar), which arch erupts first for most teeth (mandibular). The classic trap is canine timing: candidates transplant the primary sequence onto the permanent dentition and place the canine before the premolars in the maxilla. Indian university vivas frequently add a clinical layer — "a child of 14 months with no teeth: your approach" — expecting the answer to move through history, palpation, radiographs and referral rather than a single date.

## Frequently asked questions

### Which tooth erupts first and when?

The mandibular deciduous central incisor at about 6 months, followed within weeks by its contra-lateral and then the maxillary central incisors.

### What is the eruption sequence of primary teeth?

A-B-D-C-E — central incisor, lateral incisor, first molar, canine, second molar; the first molar precedes the canine.

### When should complete absence of primary teeth prompt investigation?

If no tooth has appeared by 12-18 months, examine, palpate the ridges and take radiographs, looking for delayed maturation or absent buds, with medical referral for systemic causes.

### Which permanent tooth begins calcifying at birth?

The mandibular first permanent molar — the reason a neonate's jaws already hold the seed of the six-year molar.

### How do the permanent eruption sequences differ between arches?

Mandibular order is 6-1-2-4-3-5-7 with the canine ahead of the second premolar; maxillary order is 6-1-2-4-5-3-7 with the canine last before the second molar.