Primary tooth eruption

Primary tooth eruption

Tooth eruption is a common anatomical process that involves the tooth shifting from its initial placement in the jaw bone and emerging in the oral cavity. The emergence of primary teeth normally begins around 6 to 9 months after birth, however it is not uncommon for teeth to come in a little earlier or later than this.

The timing of tooth eruption is affected by heredity, a child’s gender and ethnicity. Little girls often develop teeth sooner than what little boy’s do, and children of colour sooner than children of Caucasian decent.

In rare cases, some babies may be born with an already erupted tooth, and more commonly, some babies develop teeth as early as 3 months, while others may take up to a year. Regardless of whether your child is an early or late bloomer in terms of teething, the complete set of twenty short-term teeth are commonly visible by 30 months to three years of age. (1)

The eruption of the primary teeth is usually bilaterally symmetrical, this means that the left and right teeth will normally appear around the same time. The first set of primary teeth to breakthrough are the mandibular central incisors or front teeth, with the bottom ones coming in first, followed by the top ones. The teeth on either side of these, namely the maxillary central incisors, are second in line accompanied by the lateral incisors, 1st molars, canines, and then the 2nd set of molars, from front to back in consecutive order.

Eruption of primary teeth

Lower teeth Age of Eruption
Central incisor 6–10 months
Lateral incisor 10–16 months
Canine 17–23 months
First molar 14–18 months
Second molar 23–31 months


Upper teeth Age of Eruption
Central incisor 8–12 months
Lateral incisor 9–13 months
Canine 16–22 months
First molar 13–19 months
Second molar 25–33 months

Delayed tooth eruption

As discussed above, the timing of cutting teeth is unique to each child and delayed teething is often of little consequence in an otherwise healthy baby. However, if by 12 months of age your child has not developed teeth, it is advisable to consult with a paediatrician or dentist. While rare, there may be an underlying health condition that has developed. (2)

Some of the conditions that may cause delay in development include:

  • Impaction of teeth
  • Illness inadvertently caused by medical examination or treatment
  • Rare systemic conditions (often linked to nutritional deficiencies)
  • Down syndrome
  • Cleidocranial dysostosis (also referred to as cleidocranial dysplasia) - a birth defect that affects the teeth and bones)
  • Congenital thyroid disorders such as hypothyroidism
  • Congenital hypopituitarism (pituitary insufficiency) – a condition in which the pituitary gland does produces insufficient hormones
  • Gaucher disease – a genetic disorder wherein the enzyme required to break down fatty substances does not function correctly, leading to a build-up of these in the organs which compromises their function
  • Osteoporosis
  • Cytotoxic therapies such as chemotherapy and radiotherapy

Accelerated tooth eruption

The increased rate of primary teeth eruption can occur due to a number of factors including:

  • Fever accompanied by a skin rash (exanthemata) during pregnancy (3)
  • An over active thyroid (hyperthyroidism)
  • Turner syndrome (this is a condition in which a female is only born with 1 X chromosome)


1.  US National Library of Medicine National Institutes of Health. July - September 2017. Association between fever and primary tooth eruption: A systematic review and meta-analysis. Available at: Accessed [26/04/2018]

2. US National Library of Medicine National Institutes of Health. March 2001. Oral health and disease. Available at: Accessed [26/04/2018]

3. US National Library of Medicine National Institutes of Health. 4 August 2012. Early baby teeth: Folklore and facts. Available at: Accessed [26/04/2018]

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