title: Three-dimensional anatomy of equine incisors: tooth length, enamel cover and age related changes.
abstract: BACKGROUND
  Equine incisors are subjected to continuous occlusal wear causing multiple, age related changes of the extragingival crown. It is assumed that the occlusal wear is compensated by continued tooth elongation at the apical ends of the teeth. In this study, μCT-datasets offered the opportunity to analyze the three-dimensional appearance of the extra- and intraalveolar parts of the enamel containing dental crown as well as of the enamel-free dental root. Multiple morphometric measurements elucidated age related, morphological changes within the intraalveolar part of the incisors.
  
  
  RESULTS
  Equine incisors possess a unique enamel cover displaying large indentations on the mesial and distal sides. After eruption tooth elongation at the apical end outbalances occlusal wear for two to four years resulting in increasing incisor length in this period of time. Remarkably, this maximum length is maintained for about ten years, up to a tooth age of 13 to 15 years post eruption. Variances in the total length of individual teeth are related to different Triadan positions (central-, middle- and corner incisors) as well as to the upper and lower arcades.
  
  
  CONCLUSIONS
  Equine incisors are able to fully compensate occlusal wear for a limited period of time. However, after this ability ceases, it is expected that a diminished intraalveolar tooth length will cause massive changes in periodontal biomechanics. The time point of these morphodynamic and biomechanical changes (13 to 15 years post eruption) occurs in coincidence with the onset of a recently described destructive disease of equine incisor (equine odontoclastic tooth resorption and hypercementosis) in aged horses. However, further biomechanical, cell biological and microbiological investigations are needed to elucidate a correlation between age related changes of incisor morphology and this disease.
authors: Patricia
authors: P
authors: Schrock
authors: Matthias
authors: M
authors: Lüpke
authors: Hermann
authors: H
authors: Seifert
authors: Institute for Veterinary-Anatomy, -Histology and -Embryology, Faculty for Veterinary Medicine, Justus-Liebig-University Giessen, Frankfurter Str, 98, D-35392 Giessen, Germany (formerly Institute of Anatomy, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, D-30173 Hannover, Germany. carsten.staszyk@vetmed.uni-giessen.de.
authors: Carsten
authors: C
authors: Staszyk
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D003743:Dental Enamel / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D005260:Female; D006736:Horses / Q000033:anatomy & histology*; D007180:Incisor / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000254:growth & development; D008297:Male; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography / Q000662:veterinary