title: Multi-level synchrotron radiation-based microtomography of the dental alveolus and its consequences for orthodontics.
abstract: Multilevel synchrotron radiation-based microtomography has been performed on a human jaw segment obtained at autopsy by cutting increasingly smaller samples from the original segment. The focus of this study lay on the microstructure of the interface between root, periodontal ligament (PDL) and alveolar bone in order to find an answer to the question why alveolar bone remodels during orthodontic loading, when the associated stress and strain levels calculated with finite element analyses are well below the established threshold levels for bone remodeling. While the inner surface of the alveolus appears to be rather smooth on the lower resolution scans, detailed scans of the root-PDL-bone interface reveal that on a microscopical scale it is actually quite rough and uneven with bony spiculae protruding into the PDL space. Any external (orthodontic) loading applied to the root, when transferred through the PDL to the alveolar bone, will cause stress concentrations in these spiculae, rather than be distributed over a "smooth surface". As osteocyte lacunae are shown to be present in these spiculae, the local amplified stresses and strain can well be registered by the mechano-sensory network of osteocytes. In addition, a second stress amplification mechanism, due to the very presence of the lacunae themselves, is evidence that stresses and strains calculated with FE analyses, based on macroscopical scale models of teeth and their supporting structures, grossly underestimate the actual mechanical loading of alveolar bone at tissue level. It is therefore hypothesized that remodeling of alveolar bone is subject to the same biological regulatory process as remodeling in other bones.
authors.affiliation: Section of Orthodontics, Department of Dentistry, Institute of Odontology, Aarhus University, Vennelyst Boulevard 9, Denmark. Electronic address: michel.dalstra@odontologi.au.dk.
authors.forename: M
authors.initials: M
authors.lastname: Dalstra
authors.affiliation: Section of Orthodontics, Department of Dentistry, Institute of Odontology, Aarhus University, Vennelyst Boulevard 9, Denmark.
authors.forename: P M
authors.initials: PM
authors.lastname: Cattaneo
authors.affiliation: Section of Orthodontics, Department of Dentistry, Institute of Odontology, Aarhus University, Vennelyst Boulevard 9, Denmark.
authors.forename: M G
authors.initials: MG
authors.lastname: Laursen
authors.affiliation: Institute of Materials Research, GKSS Research Center, Geesthacht, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Beckmann
authors.affiliation: Section of Orthodontics, Department of Dentistry, Institute of Odontology, Aarhus University, Vennelyst Boulevard 9, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Melsen
mesh_terms: D000328:Adult; D016723:Bone Remodeling; D020342:Finite Element Analysis; D006801:Humans; D007568:Jaw / Q000000981:diagnostic imaging*; D008297:Male; D009970:Orthodontics; D010513:Periodontal Ligament / Q000000981:diagnostic imaging*; D017356:Synchrotrons; D014092:Tooth Root / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography; D055815:Young Adult
keywords: Alveolus; Bone; Microtomography; Orthodontics; Periodontal ligament