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Eur J Orthod. 2014 Feb;36(1):26-30. doi: 10.1093/ejo/cjs105. Epub 2013 Jan 12.

The prognosis of retained primary molars without successors: infraocclusion, root resorption and restorations in 111 patients.

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Department of Orthodontics, Faculty of Dentistry, University of Oslo, Norway.


This study aimed to assess infraocclusion, root resorption and restorations and their importance for the prognosis of retained primary mandibular molars lacking successors. The sample comprised 188 persisting primary mandibular second molars in 111 subjects, 48 males and 63 females, with a mean age of 12.6 years. The patients had been referred to an interdisciplinary clinic because of extensive hypodontia, missing 8.4 teeth on average. All persisting primary mandibular molars were included in the study, as no decision had been made as to whether they should be kept or extracted. Panoramic radiographs were used to assess infraocclusion, resorption of the mesial and distal roots and whether restorations were present. Clinically significant infraocclusion was observed in 43.6 per cent of the patients and classified as severe in 18.8 per cent. The mesial and distal root exhibited no resorption in 18.9 and 33.3 per cent, respectively (P = 0.01). Most primary molars had no restorations (78.4 per cent). A significant correlation was found between root resorption and infraocclusion. Age was found to be weakly but significantly correlated with root resorption and infraocclusion. No significant relationship was observed between gender and either infraocclusion or root resorption. In conclusion, infraocclusion was estimated to be a more critical factor for the prognosis of retained primary molars than root resorption.

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