Patient-friendly definition from the DentistsDirectory.org dental glossary.
Dental eruption is the developmental process by which a tooth moves from its position within the jaw bone, pushes through the overlying gum tissue, and becomes visible in the oral cavity. The process is driven by a combination of root growth, bone remodelling, and the pressure exerted by the developing tooth pushing upward. Eruption follows a relatively predictable sequence and timing, though there is considerable variation between individuals.
Primary (baby) teeth begin erupting around 6 months of age, typically starting with the lower central incisors. The full set of 20 primary teeth is usually complete by age 2.5–3. Permanent teeth begin replacing primary teeth from around age 6, with the lower central incisors and first molars typically first. The process continues through the teenage years, with second molars completing the set around age 12–13. Third molars (wisdom teeth) erupt last, typically between ages 17 and 25 — and frequently do not erupt fully, becoming impacted in many people.
Delayed eruption, where teeth erupt significantly later than expected, can result from crowding, early loss of a baby tooth, a retained baby tooth blocking the path, or systemic conditions. Ectopic eruption occurs when a tooth erupts in an abnormal position. Impacted teeth — most commonly wisdom teeth and upper canines — fail to fully erupt because they are blocked by bone, another tooth, or soft tissue. Orthodontic evaluation during childhood can identify eruption problems early and intervene when they are most easily addressed.