title: Standardisation of sheep model for endodontic regeneration/revitalisation research.
abstract: OBJECTIVE
  Different endodontic regeneration/revitalisation protocols have been suggested for the treatment of immature permanent teeth with pulp necrosis. Many aspects of these protocols require further investigating necessitating a suitable standardised animal model for research purposes. The focus of this study was to examine the anatomy and histology of sheep teeth at different stages of development to find an appropriate dental age for endodontic regeneration/revitalisation research.
  
  
  METHODS
  Sheep teeth at mature and immature dental ages were investigated. Standardized radiography, computed tomography, and histology were used to measure root length, apical-third dentine thickness and apex diameter, and to evaluate tissue development stages.
  
  
  RESULTS
  A mature sheep tooth has an apical area which consists of a major foramen, intermediate dilatation and minor foramen. From the time of eruption to maturation no major changes occur in the incisor root lengths, but the apical foramen width decreases and the dentinal wall thickness increases. The two-tooth age exhibited the most similar features to that of an immature permanent human tooth.
  
  
  CONCLUSIONS
  Sheep appears to be an appropriate animal model for endodontic regeneration/revitalization research with similar dimension and characteristics to human anterior teeth. Each dental age has its advantages and disadvantages. The two-tooth age showed the most favourable criteria making this age the most suitable for in vivo regeneration/revitalisation research.
authors.affiliation: School of Dentistry, University of Adelaide, SA 5005, Australia. Electronic address: milad.talib.altaii@gmail.com.
authors.forename: Milad
authors.initials: M
authors.lastname: Altaii
authors.affiliation: School of Dentistry, University of Adelaide, SA 5005, Australia. Electronic address: marita.broberg@adelaide.edu.au.
authors.forename: Marita
authors.initials: M
authors.lastname: Broberg
authors.affiliation: School of Dentistry, University of Adelaide, SA 5005, Australia; Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Electronic address: peter.cathro@otago.ac.nz.
authors.forename: Peter
authors.initials: P
authors.lastname: Cathro
authors.affiliation: School of Dentistry, University of Adelaide, SA 5005, Australia. Electronic address: lindsay.richards@adelaide.edu.au.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Richards
mesh_terms: D000818:Animals; D003782:Dental Pulp / Q000166:cytology / Q000254:growth & development; D003786:Dental Pulp Cavity / Q000166:cytology / Q000254:growth & development; D003790:Dental Pulp Necrosis / Q000473:pathology; D003804:Dentin / Q000166:cytology / Q000254:growth & development; D004708:Endodontics / Q000379:methods*; D006801:Humans; D007180:Incisor / Q000166:cytology / Q000254:growth & development; D023421:Models, Animal; D009805:Odontogenesis; D012038:Regeneration / Q000502:physiology*; D012756:Sheep; D034561:Sheep, Domestic; D019227:Tooth Apex / Q000166:cytology* / Q000254:growth & development*
keywords: Animal model; Regeneration; Revitalisation; Sheep; Teeth; Teeth histology