Stability of occlusion and anterior tooth alignment – the influence of retention in a long-term perspective
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AbstractThe lack of knowledge regarding the long-term effect of retention on anterior tooth alignment provided much of the motivation for this research project. Further, the work would give information about long-term outcome of patients treated at the Department of Orthodontics, University of Oslo (UIO), and serve as a quality assurance of the teaching at the Department. The patient material from the Department of Clinical Dentistry, University of Bergen (UIB), provided a rare opportunity to evaluate long-term stability after what by today’s standards is considered to be a short retention period. Based on the findings of the papers enclosed in the present thesis, the following main conclusions were drawn regarding stability of orthodontic treatment and the influence of retention in the long term: Stability of occlusion as measured by PAR Index improvement was 79% 10 years posttreatment in 96 patients treated at the Department of Orthodontics, UIO. The results demonstrate that orthodontic treatment can be stable to a great extent, even in the long term. Compared to other studies using same methodology and with a correspondent follow-up period, the results from the present study were favourable. The earlier Bergen sample showed somewhat less favourable long-term results with an improvement score of 54% 12 years posttreatment. However, the results were still on par with existing research with an equivalent postretention period. Anterior alignment was the occlusal component most prone to posttreatment changes. However, acceptable alignment was still found 10 years out of retention (12 years posttreatment) after only a short (2 years) retention period. A major finding was that long-term deterioration of maxillary anterior alignment showed a moderate to strong correlation with the amount of treatment correction, which in turn indicates that need for maxillary retention seems to increase with the degree of alignment correction. Types and duration of retention procedures were compared to each other retrospectively. In maxilla, dual retention was found unnecessary in the average patient with mild/moderate crowding, both in the medium and long term. For patients with more severe alignment irregularity, prolonged retention should be considered. In the mandible, longer duration of fixed retention improved the mandibular alignment, albeit to a moderate extent.
List of papers
|Paper I: Bjering R, Birkeland K, Vandevska-Radunovic V. Anterior tooth alignment: A comparison of orthodontic retention regimens 5 years posttreatment. Angle Orthod. 2015 May;85(3):353-9. Epub 2014 Aug 20. PubMed PMID: 25140669. The paper is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.2319/051414-349.1|
|Paper II: Bjering R, Sandvik L, Midtbø M, Vandevska-Radunovic V. Stability of anterior tooth alignment 10 years out of retention. J Orofac Orthop. 2017 Jul;78(4):275-283. Epub 2017 Apr 13. PubMed PMID: 28409195. The paper is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1007/s00056-017-0084-2|
|Paper III: Bjering R, Vandevska-Radunovic V. Occlusal changes during a 10 year posttreatment period and the effect of fixed retention on anterior tooth alignment. Manuscript 2017 (Under review). To be published. The paper is not available in DUO awaiting publishing.|