supervisors: dr li mei and mrs florence bennani survival times and reasons for failure of...
TRANSCRIPT
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 1/3rd 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
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
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
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
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%
0
10
20
30
40
50
60
70
80
Percentage
Survival rate at 24 months
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
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
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)
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
Upper retainer of choice = Hawley Lower retainer of choice = Vacuum-
formed Schedule more review appointments
during first 6 months of retention
Thank you
Questions?