Comparison of external apical root resorption and repair levels induced by PowerScope and Forsus fatigue resistant device appliances : Retrospective cohort study with long-term follow-up.

PURPOSE: To assess the impact of PowerScope (3M Unitek Corp., Monrovia, CA, USA) and Forsus fatigue resistant device (FRD; American Orthodontics, Sheboygan, WI, USA) appliances on orthodontically induced external apical root resorption (OIEARR) and repair amounts in the maxillary and mandibular posterior teeth.

METHODS

This study involved 39 patients treated for Angle class II malocclusion using either PowerScope (n = 20) or Forsus FRD (n = 19). A total of 546 roots were evaluated after calculating a magnification coefficient for each tooth. The lengths of maxillary and mandibular premolars, and the mesial and distal lengths of first molars were measured and compared pretreatment (T0), posttreatment (T1), and retention (T2).

RESULTS

The mean retention period was 39.8 months. Significant OIEARR was noted at T1 across almost all evaluated teeth compared with T0, while most of the teeth also demonstrated significant repair at T2 relative to T1. However, the lengths at T2 remained significantly shorter than those at T0. OIEARR was significantly greater, particularly for teeth 1.6, 2.6, 3.6, 2.4, and 4.5 in the Forsus FRD group (median values: 0.6-1.5 mm) compared to the PowerScope group (median values: 0.4-1.1 mm). For example after Forsus FRD treatment, the mesial roots of teeth 1.6 and 2.6 shorten by 1.4 mm and 1.5 mm, respectively. Although repair was observed in both groups, teeth in the Forsus FRD group exhibited significantly shorter lengths at T2 than at T0.

CONCLUSION

Almost all teeth treated with fixed functional appliances experienced OIEARR, and repair was observed during retention. However, teeth in the Forsus FRD group, particularly the maxillary molars, showed a greater reduction in length.