Abstract
Aims: This study evaluated the effects of using continuous, continuous interrupted, and
intermittent forces on the roots and periodontal ligaments in the first molars of
rats. Materials and Methods: The right first molars of 54 Wistar rats were moved with continuous force (CF group),
continuous interrupted force (CIF group), or intermittent force (IF group) for 5,
7, and 9 days. Ankylosed incisors were used as anchors for the orthodontic tooth movement.
To establish the different types of force, NiTi springs of 50 cN were maintained,
deactivated, or removed for certain periods. Amounts of tooth movement, hyaline areas,
and root resorption levels were analyzed using analysis of variance (ANOVA) and post-hoc
Tukey’s test with a significance level of 5%. Results: There was no difference in the amount of tooth movement between the CF and CIF groups,
which differed significantly from the IF group. The CF group demonstrated a significant
formation of hyaline areas, nearly 5 times more, mainly on the fifth day. Conclusions: Continuous force produced more hyaline areas with greater probability of generating
root resorption. Continuous interrupted force enabled better periodontal ligament
repair and more efficient elimination of hyaline areas.
Keywords
Ankylosis - hyaline - rats - root resorption - tooth movement