Supervisors: Dr Li Mei and Mrs Florence Bennani Survival times and reasons for failure of orthodontic retainers: a pilot study

Introduction Orthodontic retention = “secondary orthodontic treatment” McCoy, 1935

Definition Retention: “the holding of teeth following orthodontic treatment in the treated position for the period of time necessary for maintenance of the result” Moyers, 1973

Factors contributing to relapse  Contraction of stretched & displaced gingival & periodontal fibres  Imbalance in soft tissue pressures vs new positions of teeth  Post-treatment occlusal stability & functionality Reitan, 1967, 1969; Blake and Bibby, 1998; Littlewood et al., 2009; Shawesh et al., 2010

Reitan, 1959  Animal study  Teeth were rotated  Following retention period of 232 days, supra-alveolar periodontal fibres continue to show displacement  Fibrous tissue rearrangement even after several years!

Period of retention  New Zealand & Australia:  >2 years (nearly 1/3 rd of orthodontists)  Lifetime retention both removable & fixed – (over 1/5 th of orthodontists)  Netherlands:  >1 year - removable (80% of orthodontists)  Permanent – fixed (84% of orthodontists) Wong and Freer, 2004; Renkema et al., 2009

Choice of retainer type PPre-treatment occlusion PPost-treatment occlusion OOral hygiene PPatient compliance AAesthetics CComfort LLONGEVITY Wong and Freer 2004; Littlewood et al., 2009; Renkema et al., 2009

Aims To assess:  Survival times (range and rate)  Reasons for failure of retainers used in the discipline of orthodontics To provide:  Baseline for the choice of retention protocol

Eligibility criteria Inclusion Fixed orthodontic appliances Initiated in Completed by August 2012 Upper and/or lower retainers Minimum retention = 24 months Agreement to participate Postgraduate clinic

Exclusion criteria Exclusion Incomplete / missing files Retainers worn <24 months Reasons for breakage irrelevant

Method  60 patients  Telephone contact  Standard questionnaire:  Demographic data  Retainer types received  Problems  Survival time  Confirmed with patients’ files

Data analysis  First retainers only  Survival time in months  From date patient received retainer  failure date  To end of August 2014

Results  117 retainers included  38 lower fixed  11 lower vacuum-formed  17 upper fixed  30 upper Hawley  21 upper vacuum-formed

 Overall:  Maxillary retainers – 58.8%  Mandibular retainers – 59.2% Survival rate at 24 months

Survival rate for upper retainers – 6 monthly intervals

Survival rate for lower retainers – 6 monthly intervals Percentage Months

Numbers and reasons for retainer failures Characteristics BrokenLostPoor FitDebond(Total) Maxillary Hawley 7310(30) Vacuum-formed 6210(21) Fixed 400 4(17) Mandibular Hawley 0000 (0) Vacuum-formed 1110(11) Fixed 30013(38)

Discussion  Interest of the study  Retention time minimum 24 months  Upper & lower retention regimen  Findings  Most failures in first 6 months except for lower vacuum-formed  Early tendency for relapse? (Reitan 1967; 1979)  Results in accordance with worldwide studies  Limitation  Retrospective data collection

Discussion: further observations  Retainer combinations  18 patients: UF + UV and/or UH  Impact on survival time?  10 patients: UH + UV  part time retainer wear

Conclusion  24-month retainer survival rates:  Lower vacuum-formed  Upper Hawley (Breakage)  Lower fixed (Debonding)  Upper vacuum-formed (Breakage)  Upper fixed

Clinical relevance UUpper retainer of choice = Hawley LLower retainer of choice = Vacuum- formed SSchedule more review appointments during first 6 months of retention

Thank you Questions?