[Analysis of stress-strain curves in the rat molar periodontal ligament following administration of beta-aminopropionitrile (BAPN)].

To understand the function of the periodontal ligament as a tooth support, stress-strain curves obtained from the transverse section of the mesial root of the rat mandibular first molar were analyzed following administration of BAPN, known as an inhibitor of collagen cross-linking. An experimental group of rats took drinking water containing 0.2% of BAPN ad libitum for 20 days. Radiographs of the transverse section of the molar root were processed by an image analyzer. Mechanical testing was performed by pushing the tooth out of the surrounding alveolar bone at a loading speed of 7 mm/min in an extrusive direction. Doses of BAPN ranged from 19 to 29 mg/100 g bw/day during the experimental period. By the analysis of stress-strain curves, it was found that the maximum shear stress, the elastic stiffness and the failure strain energy density decreased respectively to 42, 43 and 43 percent of the control values following administration of BAPN. However BAPN did not cause a significant change in the maximum strain. It is supposed that the changes in the mechanical properties of the ligament were caused by the inhibition of cross-linking of periodontal collagen fibers.