Inheritance of susceptibility to root resorption associated with orthodontic force in mice

External apical root resorption (EARR) is an unwanted sequelae of orthodontic treatment. Genetic factors account for approximately 64% of the EARR variation in humans. Inbred mice offer a model to control the environmental factors and genetic heterogeneity that complicate human genetic studies. Genetically distinct inbred mice and their offspring (F1s) were analyzed to examine the mode of inheritance and the influence of parental sex on the susceptibility to root resorption associated with orthodontic force (RRAOF). Methods: RRAOF was determined histologically for male and female mice of the A/J, DBA/2J, and BALB/cJ strains, and the A/J x DBA/2J and A/J x BALB/cJ crosses (10 males and 10 females/reciprocal cross). RRAOF was induced by tipping the maxillary first molar mesially for 9 days. Results: Sex differences were observed only among the mice of the BALB/cJ strain. Two patterns of inheritance were observed; F1s from the A/J x BALB/cJ cross were resistant, suggesting that the A/J have dominant resistance alleles. On the other hand, F1s from the A/J x DBA/2J cross showed RRAOF intermediate between their parental mice, suggesting a polygenic trait. Conclusions: These results provide evidence of a traceable and polygenetic component affecting RRAOF in mice. (Am J Orthod Dentofacial Orthop 2008; 134: 742-50)