Description

• Teething is the eruption of primary or deciduous teeth from their development position within alveolar bone to break the gum toward the oral cavity. It is a natural, gradual, and predictable process, with normal variation among infants (1).
• Primary (deciduous) teeth
  • Primary tooth eruption usually begins at 5 to 7 months and as early as 3 months.
  • The order of primary tooth eruption and average age is the following:
    • Upper teeth:
      • Central incisor (8 to 12 months)
      • Lateral incisor (9 to 13 months)
      • Canine (cuspid) (16 to 22 months)
      • 1st molar (13 to 19 months)
      • 2nd molar (25 to 33 months)
    • Lower teeth:
      • Central incisor (6 to 10 months)
      • Lateral incisor (10 to 16 months)
      • 1st molar (14 to 18 months)
      • Canine (cuspid) (17 to 23 months)
      • 2nd molar (23 to 31 months)
  • Delayed eruption may be familial or due to systemic syndromes, nutritional deficiencies, cleft palate, and lower birth weight.
  • Tooth eruption in premature infants occurs according to postconceptual age rather than age since birth (chronologic age) (2).
  • Canine eruption leads to significantly more loss of appetite in comparison to incisors and molars (1).

Epidemiology

Incidence
Predominant age: birth to 3 years of age

Prevalence
Occurs in 68–95% of infants and nearly twice as much in low birth weight (<2,500 g) compared to normal birth weight (1,3,4)

Etiology and Pathophysiology

Teething symptoms are more common with the normal eruption of the primary incisors (3).

Genetics
Both premature and delayed tooth eruption may be familial. Primary failure of eruption has been linked to mutations of the parathyroid hormone 1 receptor (PTH1R) gene (2).

Commonly Associated Conditions

Although it has been controversial that teething has been associated with systemic conditions, studies failed to find causal relationship between teething and symptoms such as fever, diarrhea, rashes, or infections (1).