IADR Abstract Archives
Temporomandibular Joint Compressive Stresses Before and After Orthognathic Surgery
Objectives: To compare orthognathic surgical effects on temporomandibular (TMJ) loads and compressive stresses during static biting.
Methods: In accordance with institutional review board oversight, archived de-identified pre- and post-orthognathic surgery cone beam computed tomography (CBCT) images were used to investigate surgical effects on TMJ loads. Criteria were applied to exclude subjects with a history of temporomandibular disorders, syndromes, or previous TMJ procedures. Three-dimensional anatomical data of positions of the mandibular condyles, occlusal plane, and origins and insertions of the right-left pairs of masseter, temporalis, lateral and medial pterygoid, and digastric muscles, were derived from CBCT images. The anatomical data were used in a numerical model to predict TMJ loads for a range of biting angles on the right mandibular canine. Ipsilateral and contralateral compressive stresses were calculated by dividing TMJ loads by the rectilinear loading areas of right and left condyles, respectively. Analysis of co-variance (ANCOVA) tested for effects of mandibular advancement/set-back and occlusal plane rotation on TMJ loads and compressive stresses.
Results: Of 148 cases available from one site, 49 (19 males, 30 females) met inclusion criteria and provided complete data. At the time of surgery, subjects’ average age was 32.0 (±15.2) years. Presurgical TMJ stresses were generally higher in females than males and influenced by significant differences in condylar loading areas (p=0.014; females: 126 mm2; males: 146 mm2). Sex differences in TMJ loads were dependent on direction of biting vector (all p≤0.035). ANCOVA showed that with increasing occlusal plane angle (clockwise rotation in right lateral view, +°) and mandibular advancement (+mm), ipsilateral and contralateral TMJ loads were significantly increased (all p<0.050). Mandibular set-back (-mm) and counterclockwise rotation of occlusal plane angle (-°) resulted in significant reductions in TMJ loads (all p<0.050).
Conclusions: Surgery-related changes in mandibular position and occlusal plane angulation affected TMJ loads and compressive stresses.
Methods: In accordance with institutional review board oversight, archived de-identified pre- and post-orthognathic surgery cone beam computed tomography (CBCT) images were used to investigate surgical effects on TMJ loads. Criteria were applied to exclude subjects with a history of temporomandibular disorders, syndromes, or previous TMJ procedures. Three-dimensional anatomical data of positions of the mandibular condyles, occlusal plane, and origins and insertions of the right-left pairs of masseter, temporalis, lateral and medial pterygoid, and digastric muscles, were derived from CBCT images. The anatomical data were used in a numerical model to predict TMJ loads for a range of biting angles on the right mandibular canine. Ipsilateral and contralateral compressive stresses were calculated by dividing TMJ loads by the rectilinear loading areas of right and left condyles, respectively. Analysis of co-variance (ANCOVA) tested for effects of mandibular advancement/set-back and occlusal plane rotation on TMJ loads and compressive stresses.
Results: Of 148 cases available from one site, 49 (19 males, 30 females) met inclusion criteria and provided complete data. At the time of surgery, subjects’ average age was 32.0 (±15.2) years. Presurgical TMJ stresses were generally higher in females than males and influenced by significant differences in condylar loading areas (p=0.014; females: 126 mm2; males: 146 mm2). Sex differences in TMJ loads were dependent on direction of biting vector (all p≤0.035). ANCOVA showed that with increasing occlusal plane angle (clockwise rotation in right lateral view, +°) and mandibular advancement (+mm), ipsilateral and contralateral TMJ loads were significantly increased (all p<0.050). Mandibular set-back (-mm) and counterclockwise rotation of occlusal plane angle (-°) resulted in significant reductions in TMJ loads (all p<0.050).
Conclusions: Surgery-related changes in mandibular position and occlusal plane angulation affected TMJ loads and compressive stresses.