Experimental and postexperimental effects of posteriorly directed extraoral traction in adult Macaca fascicularis.

The experimental, postexperimental, and postretention effects of continuous high-pull headgear force application to the maxilla were evaluated in four adult, nongrowing Macaca fascicularis monkeys. Force was applied at 450 grams per side to face-bows attached to cast maxillary splints with an implanted occipital plug for anchorage. The active experimental phase lasted from 84 days to 205 days, and its effects were documented histologically, cephalometrically, and with dry skull preparations. Postexperimental, retention, and postretention responses were documented cephalometrically. The findings of the present investigation lead to the following conclusions: 1. The termination active sutural growth is of little significance to the remodeling potential of the sutural articulations and the morphologic adaptability of the facial skeletal complex. 2. The length of time necessary for resorptive remodeling of the sutural bony projections is partially responsible for the slower rate of detectable skeletal movement in adult animals. 3. The sutural ligament in adult animals is initially less responsive to the effects of extraoral force application, possibly because of a diminished level of cellular activity at older ages. 4. Increases in age do not appear to affect the osteogenic potential of the periosteal envelope. 5. Retention aids in establishing a maintainable equilibrium following experimentally induced sutural and skeletal remodeling, but it is of little importance in maintaining the altered position of the denition. 6. The amount of postexperimental skeletal reorientation following force application to the maxilla may be related to the force level and the duration of force.