- Dentition in humans includes a temporary dentition and a permanent dentition;
- There are 20 temporary or deciduous teeth and they erupt between ± 6 – 10 months of age for the lower jaw (7-12 months of age for the upper jaw) and ± 30 months;
- There are 28 permanent teeth (32 with wisdom teeth) and they appear between ± 6 and 13 years of age;
- Girls often have a faster dental development than boys;
- The eruption of the same tooth on both sides of the dental arch can be delayed. If this delay goes beyond 6 months, talk to your dentist;
- Primary dentition will be completed between the second and third years of age, and some primary teeth will remain in the mouth until about 12 years of age.
|The following tables represent the average age of tooth eruption. A translation of these tables is coming soon. To see a diagram illustrating the eruption and the shedding of primary teeth.|
A few facts about dental eruption in humans
Dental eruption is a dynamic and complex biological and physiological process that spans over several years and includes the formation of teeth and their migration in the jaws until they erupt in the mouth in their final functional position in the dental arches.
- It implies a transition between 2 types of dentition: the temporary or primary dentition and the permanent or definitive dentition.
- It is closely related to children’ development and craniofacial growth and involves bone and soft (gum) tissues surrounding the teeth, as well as tissue modifications, such as resorption (wear) of the roots of temporary teeth to give way to the permanent teeth.
- Eruption is a located and symmetrical process, occurring normally at the same time on both sides of the dental arch. This is programmed in time, regulated by the dental follicle and is followed by multiple modifications of tissues, such as resorption.
- The first stages of development occur during the embryonic stage and end about 20 years later with the eruption of the permanent third molars or wisdom teeth.
- The process of formation and eruption of teeth is very complex and several theories or hypotheses attempt to explain the mechanisms of eruption without nevertheless having elucidated them completely.
Chronology of normal tooth eruption
The period or age at which the temporary and permanent teeth appear shows a relatively significant variation which can be related to several factors, such as:
- Gender: dental eruption occurs in average earlier in girls than in boys, except the upper first molar;
- Height: literature reports a relationship between a child’s short height and late dental development;
- Jaws: eruption occurs later in the maxilla than in the mandible;
- Posterior teeth: the last teeth of each group (third molars, second premolars) are the teeth most affected by delayed eruption;
- Dentition: late eruptions are less common in the temporary dentition than in the permanent dentition;
- Population: there are differences in times of eruption of teeth between populations. For instance, European populations show later eruption;
- Climate: warmer climates seem to favor faster or earlier dental eruption;
- Socioeconomic conditions: children from a disadvantaged social standing can present a later dental development and eruption;
- Urbanization level: eruption is faster in urban environments than in the country;
- Phylogenetic evolution: our modern population presents more eruption problems with wisdom teeth (troisièmes molaires) (third molars) and upper canines. Researchers relate this phenomenon to human evolution and to the lack of jaw development related to changes in food habits of Western populations;
- Rank in family: eruption occurs later in children that are born last in a family than the older children.
- The video on the opposite side shows in fast-forward a normal eruption sequence of 32 teeth in humans. The numbers at the bottom represent the eruption age in years.
➡ To see other examples of early and late dental eruption.
Chronological anomalies of eruption
Chronological variations of dental eruption can be early or late eruptions, can affect only one or both dentitions (temporary and permanent) and affect one or several teeth.
Late dental eruption
Late eruptions are less frequent in temporary dentition than in permanent dentition and most late eruptions do not have significant clinical effect. Eruption is considered to be late when it occurs more than 6 months beyond the average age limit of eruption for temporary teeth and more than one year for permanent teeth.
Two situations can explain a delayed eruption:
- 1- Associated late dental maturation (late eruption); in such case, coordination between dental development and eruption (which is normal) is good but they only occur late.
- 2- Late eruption in which case dental maturation or formation is normal (late eruption). In such case, dental root formation is normal compared to the child’s age, but a physical obstruction holds back the tooth and prevents it from continuing its normal eruption path. Teeth form normally and can even have completed their formation, but they are blocked, cannot come out and thus become impacted or embedded, which is the ultimate stage of the evolution of late eruption. Dental impaction can be total or partial and can affect all permanent teeth, but certain are more affected (in order of occurrence: wisdom teeth, upper canines, premolars, lower incisors, lower canines and molars).
NOTE : Before talking about late eruption, a differential diagnosis with agenesis (congenital absence of one or several teeth) must be done with a radiological examination.
Early and premature eruption
Early eruption: Dental eruption can also occur earlier than planned. and is thus called early eruption.
- For temporary teeth, it will most often occur when the tooth bud is positioned superficially under the gingiva. It is also observed in cases of hyperthyroidism and early puberty.
- Early eruption of the whole permanent dentition is exceptional and can be related to endocrine problems or certain syndromes. Early eruption of a single tooth is more frequent and is usually caused by local etiological factors, such as premature loss of a temporary tooth which is itself most often caused by dental decay.
Premature eruption: It is different from early eruption because it implies immature teeth, always in the bud state, that erupt and can be caused by traumas, tumors, infections, etc.
The cause of early or late eruptions can be various and also be related to:
- genetic origin,
- systemic problems (for instance, a deficiency in vitamin A or D),
- endocrine disorders,
- metabolic disorders,
- local factors (tumors, traumas, position of the bud, etc.).
➡ To see examples of early and late eruption.