A comparative study of mandibular growth patterns in seven animal models

The use of nonhuman primate experimental models has helped make significant contributions toward the clinical and surgical management of patients with craniofacial disorders. With concerns such as increasing cost, however, alternative models will have to be identified. The present comparative study describes baseline, age-related changes in mandibular growth patterns for seven commonly used animal models. The data was obtained from 144 serial and cross-sectional lateral head radiographs of unoperated control animals from a number of previous craniofacial growth studies. The sample consisted of 26 rats, 21 rabbits, 21 domestic cats, 23 domestic dogs, 17 baboons, 16 rhesus monkeys, and 20 chimpanzees. Comparative human data were taken from the Bolton Standards. The samples were divided into three age categories: infant, juvenile, and adult. Mandibular growth measurements included overall mandibular length, ramal height, and body height. Comparative analysis consisted of the calculation of percent increase from the infant condition. For all measurements, three major clusters could be discerned: 1) humans, chimps, and rhesus monkeys; 2) dogs and baboons; and 3) cats, rats, and rabbits. Results suggested that for the dimensions studied, long-term mandibular growth was best modeled by short-faced primates, and in particular, the chimpanzee. In addition, dogs and rats showed similar relative percent changes in different regions from juvenile through adulthood stages, which suggests that these animals may be acceptable, inexpensive alternatives to primates in certain experimental situations.