Methods: Mandibular segments containing central incisors were embedded in acrylic with the long axis of the root perpendicular to the applied load. Treatment samples were intruded 5mm using a class 2 lever with a minimum force of 1280N. Intruded (n=10) and non-intruded control (n=10) specimens were tested in compression using a Material Testing System (MTS) and the elastic modulus was compared between groups. Incisor displacement was measured on X-ray images taken before and after trauma (if applicable), and following compressive tests.
Results: In 8 paired specimens, the average ratio of Young’s Modulus (Econtrol/Eintrusion) indicated a minimum 2-fold higher stiffness of non-traumatized specimens. Intruded specimens showed a tendency for an extended slack period that was not observed in controls. The intrusion group modulus was significantly lower than the control group (4452 vs. 7704 Mpa; p=0.05). After MTS testing, the root length embedded in bone increased in traumatized and non-traumatized teeth by 2.9mm and 0.81mm, respectively (p=0.03).
Conclusions: Damage to the PDL led to a delay in load bearing and diminished overall periodontal support of the tooth. Traumatic injury in porcine incisors produced a significant degree of axial mobility and constitutes an important model for further study of childhood incisor intrusions. Supported by University of Washington Dr. Douglass L. Morell Dentistry Research Fund.
Keywords: Biomechanics, Pedodontics, Periodontium-gingiva, Stress and Trauma-fracture