# Growth, Development and Tooth Eruption

> Eruption chronology for NEET-MDS Pedodontics: primary and permanent dates and sequences, Nolla stages, leeway space of Nance and ugly duckling phase.

- Canonical URL: https://prepelephant.com/topics/neet-mds/pedodontics/growth-development-tooth-eruption-mds
- Exam / course: NEET-MDS · 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: "Growth, Development and Tooth Eruption", PrepElephant, https://prepelephant.com/topics/neet-mds/pedodontics/growth-development-tooth-eruption-mds

## Direct answer

Six months, give or take, is the calendar anchor of paediatric dentistry: the mandibular primary central incisor erupts at about 6 months (5.5-8 months), the full primary complement of 20 teeth is in place by 2.5-3 years, and the primary sequence in both arches runs A-B-D-C-E with the mandibular teeth preceding their maxillary counterparts. The first permanent molar arrives at about 6 years and its calcification begins at birth; the permanent mandibular sequence is 6-1-2-3-4-5-7 while the maxillary sequence is 6-1-2-4-5-3-7, because the maxillary canine erupts after the premolars. Development before eruption is staged by Nolla's ten stages (crown complete at stage 6, apical closure at stage 10), the mixed dentition holds about 1.7 mm of mandibular and 0.9 mm of maxillary leeway space per side (Nance), and the midline diastema with distally flared incisors at 8-9 years is the physiological ugly duckling phase of Broadbent.

## What you must remember

- **Primary chronology:** central incisor 6-7 months, lateral 7-10 months, first molar 12-16 months, canine 16-22 months, second molar 20-30 months; mandibular teeth generally precede maxillary.
- **Primary root milestones:** roots complete roughly 1-1.5 years after eruption; physiological resorption begins about three years after eruption, driven by the succedaneous follicle.
- **Permanent anchors:** first molar at 6 years (calcifies at birth), mandibular central incisor 6-7 years, maxillary central 7-8, mandibular canine before premolars, maxillary canine after second premolar, second molar 11-13 years, third molar 17-21 years.
- **Sequences to reproduce:** primary A-B-D-C-E; permanent mandibular 6-1-2-3-4-5-7; permanent maxillary 6-1-2-4-5-3-7.
- **Nolla's stages:** 1 germ present, 2 initial calcification, 3 one-third crown, 4 two-thirds crown, 5 crown nearly complete, 6 crown complete, 7 one-third root, 8 two-thirds root, 9 root almost complete with open apex, 10 apex closed — the film-reading language of timing.
- **Leeway space of Nance:** about 1.7 mm per side in the mandible (3.4 mm total) and 0.9 mm per side in the maxilla (1.8 mm total), because the second primary molars are larger than the second premolars; it is normally closed by early mesial shift of the first permanent molars.
- **Ugly duckling stage (Broadbent, 8-9 years):** midline diastema and distal flaring of maxillary incisors from canine impingement on lateral incisor roots; self-correcting by about 12 years — never treat orthodontically during it.
- **Eruption theory:** altered proteoglycan degradation in the dental follicle and periapical tissue, mediated by cellular events, is the currently favoured mechanism — the viva line beyond "bone remodelling".

## Working a mixed-dentition timeline

An eight-year-old presents with a midline gap of 3 mm and flared upper incisors, and the parents want braces now. Read the radiograph first: the canines sit low with their crowns between the lateral incisor roots — Broadbent's ugly duckling. The correct answer is reassurance and observation, because the canines upright the incisor crowns as they erupt, closing the diastema by about 12 years; intervening with appliances now fights a physiological phase. Now flip the reasoning to extraction timing. A carious mandibular second primary molar in the same child, with the second premolar at Nolla stage 7-8 (one-third to two-thirds root), can be extracted with confidence that the premolar will follow; the same extraction at Nolla stage 4 in a six-year-old argues for a space maintainer, because the first permanent molar will drift forward and consume the 1.7 mm leeway that belongs to the premolar. Chronology, Nolla staging and leeway arithmetic are the same clinical judgement in three notations — and the exam tests exactly these conversions.

## How the exam frames it

The recurring MCQs are date-and-sequence trivia with a twist: the first tooth to erupt (mandibular primary central incisor), the first permanent tooth to calcify (first permanent molar, at birth), the tooth calcifying at birth (the same first molar — a favourite), and which permanent tooth erupts last in the maxilla of a 12-year-old (the canine, after the second premolar). The classic distractor pair is the permanent canine's position in the two arch sequences. A second layer asks you to apply Nolla: a premolar at stage 6 means the crown is complete but root growth has not begun, so extraction of its predecessor is premature. Finally, the ugly duckling appears as a clinical judgement question — the wrong options are frenectomy, orthodontic closure and composite build-up; the right answer is observation.

## Frequently asked questions

### Which is the first primary tooth to erupt and when?

The mandibular primary central incisor at about 6 months (acceptable range 5.5-8 months), followed within weeks by its contralateral and the maxillary centrals.

### Which permanent tooth begins calcification at birth?

The first permanent molar — a standard NEET-MDS fact that also explains its vulnerability to molar-incisor hypomineralisation from perinatal illness.

### What is leeway space and how much exists per side?

The excess of the primary second molar and canine widths over their successors: about 1.7 mm mandibular and 0.9 mm maxillary per side (Nance), normally consumed by mesial drift of first permanent molars.

### What is the ugly duckling stage?

Broadbent's physiological 8-9-year phase of midline diastema and distally flared maxillary incisors caused by erupting canine pressure, self-correcting by about 12 years.

### What does Nolla stage 8 signify?

Two-thirds root formation — the stage at which a succedaneous tooth can be expected to erupt within roughly a year, guiding extraction versus space-maintenance decisions.