IYAD sheet 8
-Usually clinicians fail to provide the proper retention after treatment leading to relapse.
- Main problem after treatment is relapse.
-discuss that with your patient and emphasize on the importance of their co-operation by wearing the retainers as prescribed.
- be aware of growth and maturational changes and their effect.
- we have 2 stages of treatment: Active phase and retentive phase.
1-Retention: is the use of PASSIVE appliance/s to prevent relapse of tooth movements and to hold teeth in optimal functional and aesthetic position.
2- Retention: is the phase of orthodontics which maintains the teeth in their new position after active phase.
-retention is a passive mechanism of holding teeth in place
-retentions is need for basically all types of movements/appliances.
-retention requirements are different depending on:
Rationale: (why do we need retention)
*Minimize changes due to growth
*Allow for reorganization of the PD tissues
*Permit musculature adaptation
*Maintain teeth in unstable positions for compromise or aesthetic reasons (ideally we don't compromise our treatment but if we are correcting one problem only for whatever cause and forgetting about the rest we compromise)
etiology of relapse:
1- growth! (very imp.)
sometimes it's favorable and sometimes it's not so we might consider prolonging our retention or extending our treatment.
class 2 div 1>> growth is usually favorable
class3>> growth is mostly unfavorable
--relapse usually occurs due to movement in vertical..sometimes it may extend to AP or sagittal
--deep overbite treated during adolescence may improve but relapse if pt is growing, so we need to either extend our treatment or prolong our retention.
--AOB is very prone to relapse 2- Periodontal tissue (very very imp)
a-bone is not really a problem ,has easy and predictable reorganization (6 months-up to 2? years) for it to go back 90% to original state
b- also the PDL fibers are attached to bone and teeth and take approximately the same amount of time for the bone to be remodeled (6 months-1 year ).
c-However, the problem is in soft tissues >>gingival fibers, transeptal and supracrestal fibers .
These are attached to teeth and soft tissues and take long time for reorganization to occur.... Some studies say that they never reorganize or take a lot of time to do so (more than a year) and won't reorganize 100%...that's why we may consider long term retention.
>>>>If we have generalized spacing or rotations >>high relapse (due to periodontal tissues)
solutions: prolonged retention / overcorrection of rotations/ supracrestal fiberotomy also called circumcision which will allow fibers to reattach in new position
3-soft tissue equilibrium (important)
soft tissues (tongue and lips) are important in holding teeth
if they are normal don't disturb their balance.
4- occlusal forces (maximum intercuspation)>> this a poor factor of minimal impact
-maximum intercuspation may help in retention , we prefer a cusp to fossa relationship.
- occlusal forces can work against us so ideally we want teeth to be in maximum interdigitation.
this is helpful in crossbites correction.
5- Genetic :
some cases have the inherent tendency to relapse
As a general rule:
DON'T CHANGE THE ORIGINAL ARCH FORM!
-if we want to do treatment in lower (which has more forces on it than the upper) we should not mess with the arch form (ex..elliptical should stay elliptical)
-any disturbance will cause imbalance between lips and tongue bringing back the lower teeth to their original place.
- we build the upper arch based on the lower
-vertical dimension once established is difficult to change (so extrusion of post teeth in adults is going to relapse>>no bone remodeling)
We can't predict what type of growth we will have (post or ant) but there are certain signs
-class3--AOB--deepbites >>pt's growth is usually working against us so you have to prolong trx/retention
-Adults grow but at a much lesser magnitude and rate, late facial growth is considered to be an ongoing process throughout life
-retention should be planned with knowledge of the pt's dentofacial structure and anticipated magnitude and direction of growth.
long term follow up.>>teeth relapsed almost to same position! (in both expansion and extraction)
no predictors...simply if you change arch width this will have a high relapse tendency. - reduction in arch length /arch width is a normal physiologic process
-mandibular anterior crowding is a continuing phenomena
-3rd molars have little effect on occurrence or degree of relapse.
-degree of post retention and crowding is not predictable and variable ______________________________________________________________________________
Teeth tend to return to previous position
again if pt is growing : either you prolong the treatment or extend the retention.
- we may include a component like an anterior bite plane within the retainer to maintain the ovb
upper incisors should be covered by lower lip>>mohm!
if we can't do that we may consider surgery..
it's important because we aim to achieve a proper soft tissue environment after trx that aids in retaining the upper incisors in their new positions
class 2 div 1 retention
-don't procline lower incisors more than 2-3 mm
-consider functional appliance type of retainers ...after treatment of for example 6 months ,,,we let the pt use the same appliance until reorganization of soft tissue occurs, but instead of wearing the appliance all the time, we ask the pt to wear it only at bedtime. (active retention...only worn at night )
ex: twin block
or headgear (active but less time)
so overcorrection or supracrestal fiberotomy
-passive bite planes are a good mechanism of retention
- if we have AOB and we intrude the post teeth to close it will tend to relapse if pt is growing (late vertical growth) and use occlusal coverage.
-pt should be notified of the duration of treatment and duration of retention
How long to retain?
what if no retention?! ALL movements need retention !>> or relapse occurs
-however in single crossbite after corrected (example anterior crossbite..(after correction and positive ovb)the lower teeth will prevent the upper from going back into crossbite >>part of the dentition is holding the teeth in place
1-short term retention:
-fixed appliance for example in class 1 (1 year retention >>6 moths full time and 6 months night time)
- URA (6months retention >> 3 full time and 3 night time)
pt still growing after correcting >>usually after functional appliances