Craniofacial adaptation of protrusive function in young rhesus monkeys.

I t is still not fully understood how clinical corrections are achieved by activators and other related orthodontic and orthopedic procedures, largely because the role of function in craniofacial growth and orthodontic treatment is not yet clear. Numerous experiments have been conducted using different methods and producing widely varying results. Clinical studies have offered one avenue of approach to this problem. Patients treated by one of the functional jaw orthopedic methods have been analyzed individually or compared to untreated controls. Many of these studies reported differences in the craniofacial growth pattern, particularly in the mandible.lm4 Both Brownel and Marschner and Harris,2 in two of the few clinical studies that consider total mandibular length rather than mandibular positioning, noted significantly higher mandibular growth rates in the treated groups. However, Bj6rk5 stated that any skeletal changes during this type of treatment may well be within the range of normal growth. Other investigators5-7 found that treatment had no apparent effect on mandibular growth but, rather, acted by reshaping the alveolar arches, by altering vertical dimension, and by affecting the eruption and alignment of teeth. Definitive comparisons among these findings are somewhat obscured by differences in measuring methods, experimental design, and treatment procedures. Experimental approaches have also been taken. The studies most relevant to the clinician have been those utilizing nonhuman primates. Since the original