Age-related morphometry of equine incisors.

In the present study the age-related morphological characteristics of 948 equine incisors were investigated. After extraction, total incisival length and root length were measured at the vestibular side of the teeth. Equine incisors reach their maximal length 2-3 years after eruption. Notwithstanding severe occlusal wear, this maximal length is maintained during most of the horses' life due to prolonged root formation. Root formation, at the rate of 2.5 mm per year, starts at the age of 5-6 years and continues until the age of 17. As the root of the incisor develops, its apical foramen narrows and changes position. In young horses the apical foramen is situated at the apex of the tooth, whereas in older individuals it is located at the mesial, distal, or lingual side of the tooth at a distance of 5-15 mm from the dental apex. In horses aged over 20 years apical foramina are still present. Radiographic imaging is a good method with which to obtain reliable information concerning the total incisival length and the size and position of the apical foramen.