supervisors: dr li mei and mrs florence bennani survival times and reasons for failure of...
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Supervisors: Dr Li Mei and Mrs Florence Bennani
Survival times and reasons for failure of orthodontic retainers:
a pilot study
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Introduction
Orthodontic retention =
“secondary orthodontic treatment”
McCoy, 1935
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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
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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
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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!
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Period of retention New Zealand & Australia:
>2 years (nearly 1/3rd of orthodontists)
Lifetime retention both removable & fixed – (over 1/5th of orthodontists)
Netherlands: >1 year - removable (80% of orthodontists)
Permanent – fixed (84% of orthodontists)
Wong and Freer, 2004; Renkema et al., 2009
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Choice of retainer type Pre-treatment occlusion Post-treatment occlusion Oral hygiene Patient compliance Aesthetics Comfort LONGEVITY
Wong and Freer 2004; Littlewood et al., 2009; Renkema et al., 2009
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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
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Eligibility criteria
InclusionFixed
orthodontic appliances
Initiated in 2010-2011
Completed by August
2012
Upper and/or lower
retainers Minimum retention = 24 months
Agreement to
participate
Postgraduate clinic
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Exclusion criteria
Exclusion
Incomplete / missing files
Retainers worn <24 months
Reasons for
breakage irrelevant
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Method
60 patients Telephone contact Standard questionnaire:
Demographic data
Retainer types received
Problems
Survival time
Confirmed with patients’ files
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Data analysis
First retainers only Survival time in months
From date patient received retainer failure date
To end of August 2014
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Results
117 retainers included 38 lower fixed
11 lower vacuum-formed
17 upper fixed
30 upper Hawley
21 upper vacuum-formed
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Overall:Maxillary retainers – 58.8%Mandibular retainers – 59.2%
0
10
20
30
40
50
60
70
80
Percentage
Survival rate at 24 months
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Survival rate for upper retainers – 6 monthly intervals
Start 6 12 18 2450
55
60
65
70
75
80
85
90
95
100
Vacuum-formed
Fixed
Hawley
Percentage
Months
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Survival rate for lower retainers – 6 monthly intervals
Start 6 12 18 2450
55
60
65
70
75
80
85
90
95
100
Vacuum-formed
Fixed
Perc
en
tag
e
Months
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Numbers and reasons for retainer failures
Characteristics Broken Lost Poor Fit Debond (Total)
Maxillary
Hawley 7 3 1 0 (30)
Vacuum-formed 6 2 1 0 (21)
Fixed 4 0 0 4 (17)
Mandibular
Hawley 0 0 0 0 (0)
Vacuum-formed 1 1 1 0 (11)
Fixed 3 0 0 13 (38)
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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
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Discussion: further observations
Retainer combinations 18 patients: UF + UV and/or UH
Impact on survival time? 10 patients: UH + UV
part time retainer wear
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Conclusion
24-month retainer survival rates: Lower vacuum-formed Upper Hawley (Breakage) Lower fixed (Debonding) Upper vacuum-formed (Breakage) Upper fixed
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Clinical relevance
Upper retainer of choice = Hawley Lower retainer of choice = Vacuum-
formed Schedule more review appointments
during first 6 months of retention
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Thank you
Questions?