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Stability of anterior tooth alignment 10 years out of retention
Ragnar Bjering1, Leiv Sandvik2, Marit Midtbø3
1Department of Orthodontics, Faculty of Dentistry, University of Oslo, P.O. Box 1109 Blindern, 0317, Oslo, Norway. ragnar.bjering@odont.uio.no.
Objective:
Long-term posttreatment stability of anterior tooth alignment is of major interest to both patients and orthodontists. In the present study we examined the long-term outcome 10 years postretention and investigated the possible influence of treatment-related factors on posttreatment stability of maxillary and mandibular anterior tooth alignment.
Methods:
The sample comprised 51 patients treated with full fixed appliances in a university clinic. Average retention time was 1.8 years. All patients received a Hawley appliance in the maxilla and a bonded canine-to-canine retainer in the mandible. The Peer Assessment Rating (PAR) Index, Little's Irregularity Index (LII) and dental cast variables were recorded at pretreatment, posttreatment and 10 years out of retention. Stability of occlusion was assessed with the PAR score percentage improvement method. For each jaw a multivariate regression analysis was performed to identify the influence of treatment-related factors on postretention tooth alignment.
Results:
The PAR Index percentage improvement decreased from 73.1% posttreatment to 53.5% 10 years out of retention. For both jaws posttreatment increase in anterior irregularity was significantly correlated with the degree of treatment correction. The strongest association was found in the maxilla. Premolar extractions were associated with increased stability of mandibular alignment.
Conclusions:
The need for retention appears to increase with the degree of alignment correction, particularly in the maxilla. Extraction of premolars significantly improved long-term stability of mandibular incisor alignment.