Aims: Determination of the interdependence of the extent of EARR on the quantity of applied orthodontic intrusive force and the correlation between resorption and the extent of intrusion.
Materials and methods: The set included 17 patients in which the treatment with fixed appliance was indicated, together with the extraction of the maxillary first premolars. For six months, the unilateral force of 50 g was applied in the premolars, the force of 150 g was applied in counterlateral teeth. Then the teeth were extracted and measured. CT scans was taken prior the treatment period and after that. In all CT scans the length of a tooth, the length of a root, and the length of a crown were measured prior and after the research.
Results: We found out that when the intrusive force of 50g was applied, the mean value of intrusion reached 1.69mm. In case of the intrusive force of 150g it was 4.86mm. The extent of a tooth intrusion depends on the extent of the intrusive force. The dependence is statistically significant. When the intrusive force of 50g was applied, the mean value of the change in the root vestibular length was 0.44mm. In case the intrusive force of 150g was applied, the mean value of the root resorption reached 0.73 mm. The values are not statistically significant.
Conclusion: The root apex resorption does not depend on the extent of the intrusive force. However, the force is a statistically significant factor of the extent of a tooth intrusion.