Background/Objectives: The aims were 1. to analyse differences in the occurrence of orthodontic induced inflammatory root resorption (OIIRR) of the upper and lower incisors in Angle Class II division 2 patients, between patients treated with fixed appliance only (one-phase treatment group) and patients treated with removable appliance before treatment with fixed appliance (two-phase treatment group) and 2. to analyse differences in OIIRR between treatment time, age, gender, craniofacial morphology and deviations in the dentition for the two groups together.

Materials/Methods: Seventy-four subjects treated for Class II division 2 malocclusion were divided into two groups: 46 patients in the one-phase treatment group (28 girls, 18 boys, mean age 14.4) and 28 patients in the two-phase treatment group (18 girls, 10 boys, mean age 12.4) where 336 and 201 incisors were analysed respectively. OIIRR was assessed on intra oral radiographs, deviations of the dentition were assessed on orthopantomograms and the craniofacial morphology was assessed on lateral cephalograms. Differences were tested by Fisher Exact test, McNemar, and multiple regression analysis.

Results: The one-phase treatment group showed significantly more OIIRR for lower central incisors (P = 0.002) compared to the two-phase treatment group. For the both groups combined, boys showed more OIIRR than girls (P = 0.002) and patients with agenesis showed more OIIRR than patients without agenesis (P = 0.019) for the lower central incisors.

Conclusion: The results indicate that two-phase treatment modalities may be considered as an option for Angle Class II division 2 patients with enhanced risk for OIIRR.