Primary and permanent dentition, eruption and types of occlusion
The human dentition consists of two sets of teeth - primary and permanent.
The teeth are arranged in two ellipsoid arches, the maxillary and mandibular arch. Each arch is divided into two symmetrical halves called quadrants.
Primary Dentition[edit | edit source]
The primary dentition, also more commonly known as the milk teeth, consist of 20 teeth, 10 in each arch.
There are 5 in each quadrant (four quadrants in the mouth): a central and lateral incisor, a canine and two molars.
Permanent Dentition[edit | edit source]
The permanent dentition consists of 32 teeth, 16 in each arch.
There are 8 in each quadrant: a central and lateral incisor, a canine, two premolars and three molars.
Eruption[edit | edit source]
The milk teeth erupt at around 6 months of age and start getting replaced by permanent teeth at around 6 years of age.
The permanent teeth erupt at around age 6-13 with the 3rd molar usually coming in at around 21 years of age.
Types of occlusion[edit | edit source]
Occlusion refers to the way the two dental arches come together when the jaw is closed. Normal occlusion allows oral functions to occur properly, provides the best aesthetics and helps in prevention of disease. Anything other than is referred to as malocclusion.
We can use the Angles classification system to differentiate them
- Class I: Orthognathic occlusion; normal occlusion, the upper teeth slightly overlap the lower teeth
- Class II Retrognathic occlusion; either the maxilla or the mandible (mostly) has an abnormally posterior position relative to the rest of the skull
- Class III: Prognathic occlusion; protrusion of the lower jaw
Both class II and III are malocclusions.
