Periodontal ligament hydrostatic pressure with areas of root resorption after application of a continuous torque moment.
OBJECTIVE
To evaluate the risk of root resorption, individual finite element models (FEMs) of extracted human maxillary first premolars were created, and the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models was simulated.


METHODS
A continuous lingual torque of 3 Nmm and 6 Nmm respectively was applied in vivo to the aforementioned teeth. After extraction, FEMs of these double-rooted teeth were created based on high-resolution microcomputed tomographics (micro CT, voxel size: 35 microns). This high volumetric resolution made the recognition of very small resorption lacunae possible. Scanning electron micrographs of the root surfaces were created as well. This enabled the investigation of advantages and disadvantages of the different imaging techniques from the viewpoint of the examination of root resorption. Using the FEMs, the same loading conditions as applied in vivo were simulated.


RESULTS
The results of clinical examination and simulations were compared using the identical roots of the teeth. The regions that showed increased hydrostatic pressure (>0.0047 MPa) correlated well with the locations of root resorption for each tooth. Increased torque resulted in increased high-pressure areas and increased magnitudes of hydrostatic pressure, correlating with the experiments.


CONCLUSIONS
If hydrostatic pressure exceeds typical human capillary blood pressure in the PDL, the risk of root resorption increases.
Hohmann
Ansgar
A
Department of Orthodontics, University of Ulm, Ulm, Germany. ansgar.hohmann@uni-ulm.de
Wolfram
Uwe
U
Geiger
Martin
M
Boryor
Andrew
A
Sander
Christian
C
Faltin
Rolf
R
Faltin
Kurt
K
Sander
Franz Guenter
FG
D001641:Bicuspid / Q000503:physiopathology; D001794:Blood Pressure; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D006874:Hydrostatic Pressure; D008437:Maxilla; D008855:Microscopy, Electron, Scanning; D010513:Periodontal Ligament / Q000098:blood supply / Q000503:physiopathology*; D012391:Root Resorption / Q000209:etiology* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed; D014087:Tooth Movement Techniques / Q000009:adverse effects*; D019415:Torque