Role of Animal Models in Experimental Studies of Craniofacial Growth Following Cleft Lip and Palate Repair

Abstract

The present study was designed to examine the role of the animal model on investigations of craniofacial growth. Identical experimental protocols were followed using 6-week—old rabbits and 8-week—old bea-gles. Three groups were used for each species, two control groups and one experimental group. The groups within each experimental model were compared for lip pressure, occlusion, and cephalometrics. Statistical analyses including analyses of correlations were used to evaluate dimensional craniofacial relations. The results of this study revealed that dimensional relations were significantly different in rabbits and bea-gles despite the similarities observed in overall craniofacial growth aberrations. Analysis of the results does not allow strong conclusions about which animal model (rabbits or beagles) is more appropriate for studying craniofacial growth. KEY WORDS: simultaneous lip and palate repair, craniofacial growth, animal models, beagles, rabbits, surgically induced cleft lip and palate, craniofacial growth aberrations, craniofacial growth disproportions Animal models are important in research that cannot be readily conducted using humans. When using animal models, however, investiga— tors must not only be aware of the limitations of such models, but must also recognize that the choice of animal might have a pronounced effect on the findings. In our laboratory, experimental research on the effects of various surgical procedures on craniofacial growth was conducted initially in the rabbit model and then in the beagle model. The change of model was, in part, brought about by the criticism of Sarnat (1982), who indicated that lagomorphs are not the best animal model for experimental research on craniofacial growth. Following this criticism, we conducted a literature search to find studies that would suggest that a particular animal provides the best model for studying craniofacial growth. We found that a great variety of animals—such as rats (e. g., Duker and Harle, Siegal and Sa-dler, 1981) have been used to study craniofacial growth. However, we could find no study that compared animal models. This fact raises a legitimate question: which animal model is best for evaluating the effects of various surgical procedures on craniofacial growth? There are very few guidelines for selecting the most appropriate animal model to study craniofa-cial growth. There are obviously several factors that must be considered in the selection of the animal model: factors such as anatomical structures of the facial skeleton, structure and position of the premaxilla, and type of dentition. It is often assumed that a close phylogenetic relationship signifies an appropriate animal model. However, there is no proof that primates are always the best model for craniofacial growth ex— perimentation or that rats or rabbits are poor choices.