Experimental dental traumatology: development of a model for external root resorption

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Abstract
Intentional replantation of teeth appears to be a suitable model for examining the etiology and pathogenesis of root resorption elicited after traumatic dental injury. A histomorphometric analysis of root resorption developed with this model is described. An analysis of the accuracy and precision of the method in replanted monkey incisors has demonstrated that the method is usually reliable in revealing the extent and type of root resorption. In some experimental circumstances, however, where the pulp status was not controlled by endodontic therapy, a large intra‐ and interanimal variation was found in the extent of root resorption. Apart from a relation to tooth maturation and tooth type (incisors versus molars), this variation was primarily caused by haphazard occurrence and extent of inflammatory resorption. Based on an analysis of a series of experimental replantation studies, the following guidelines for experimental design seem appropriate: 1) selection of teeth according to identical tooth development and pulp status (i.e. intact, extirpated or root‐canal‐treated); 2) use of a standardized extraction procedure; 3) consideration of the type of teeth included (i.e. molars vs. incisors), unless paired experiments are planned or the experimental design includes an equal number of incisors and molars allotted to the different experimental groups; 4) side differences (right vs. left side) are apparently of no or minor importance; 5) sex differences are apparently of no or minor importance; 6) an individual proneness to resorption is apparently of no or minor importance, which means that more than one tooth can be used in each animal. The experimental design thus does not dictate the use of paired (i.e. homologous) teeth. However, as a matter of safety, when small differences in healing are expected, paired observations should be used.