Summary Background The aim of this retrospective cohort study was to assess long-term occlusal changes at debond and a median of 8 years afterwards (in retention) with the American Board of Orthodontics (ABO) objective grading system and identify risk factors. Materials and method Fifty patients (median age: 14.3 years at debond; 60% female) treated with fixed appliances (25 with and 25 without premolar extractions) were included. The occlusal outcome was assessed with the ABO tool and analyzed statistically at 5%. Results Extraction treatment was associated with better occlusal outcome than non-extraction treatment (34.2 versus 40.9 points; P = 0.009). In retention, ABO scores improved by 7.4 points, while patients with worse debond finishing improved more afterwards (P = 0.001). Alignment/rotations deteriorated in 58% of the cases and occlusal relationships in 38% of the cases. Marginal ridges improved more for extraction than non-extraction patients (28% versus 0%; P = 0.001). Occlusal relationships improved more for cases that ‘passed’ the ABO requirements at debond than failed cases (64% versus 28%; P = 0.02). Furthermore, patients with worse debond ABO scores were more likely to deteriorate at alignment/rotations in retention. Finally, the proportion of cases passing the ABO requirements improved considerably between debond (28%) and in retention (54%) as half (47%) of the cases that had failed the ABO requirements at debond passed them in retention. Conclusions Considerable long-term occlusal changes are seen post-debond, which mostly favour improved settling. Extraction treatment and higher finishing quality at debond significantly influenced the chance for improvement. However, setting a cut-off score to denote treatment excellence showed considerable instability through time.

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