Fixed Appliances in Orthodontics 2 Flashcards
What was the experiment that lead to having 6 keys to normal occlusion
120 sets models: local dentist, orthodontist, university department sent in study models of patients that didn’t have any ortho treatment previously:
Straight teeth
Pleasing appearance
Bite seemed correct
Did not need ortho treatment
1150 models of ortho treated patients with good results
compared results
What are the 6 keys?
Correct molar relationship Correct crown angulation Correct crown inclination No rotations No spaces Flat occlusal plane
What is a class I molar relationship?
Mosio-buccal cusp of upper 1st molar occlues in buccal groove of lower 1st molar
What is meant by correct crown angulation?
Root of the tooth should always be distal to the crown
5 degrees in 1st molars
11 degrees of upper right canine
5 degrees of distal tip on upper right central incisor
What is meant by correct crown inclination?
torque
the root should be more palatal making the tooth more proclined
What is key 5?
No spaces - tight contacts
no crowding
What does the straight wire have built in?
tip values - get teeth in the right angles
torque values
in-out values - different bracket thickness
What are the main stages of treatment?
Levelling and aligning
Space closure: overjet reduction, centreline correction
Additional stages: Overbite correction, crossbite correction, finishing and detailing
What is the levelling and aligning stage?
Levelling to get them all in the same planes
Bucco-lingually, mesio-distally, correct rotations
Always use NiTi to do this (round wire)
What is the problem with tip of canine in brackets?
Crown moves forwards (mesially)
Incisors extrude (upwards)
Overbtie deepens
What can be dont to stop the canine from tipping mesially?
Ligature wire under the arch wire
prevents the canine crown moving mesially
posterior teeth can move forwards
What wire is used for space closure (and overjet reduction and centreline correction)
Arch wire 0.019x0.025 SS
What are the methods of space closure?
NiTi spings/coild
Elastics: Powerchain, Modules (traction ligatures, elastics), temporary anchorache devices
What are the types of retainer?
Removable: acrylic (hawley), Vaccum formed (essix)
Fixed: bonded
When would you use a hawley retainer?
When have missing teeth, can have prosthetic ones on retainer
made from acrylic baseplate and metal labial bow
What are essix retainers?
Vacuum-formed, better at holdning the teeth- clear plastic
cover all the teeth
thinner than gun shield
only drink water with them in
What is the advantage of Essix over Hawley?
Superior aesthetics Less interference with speech more economical quicker to make less likely to break ease of fabrication superior retention of lower incisors
What happens if have Essix retainer and poor OH?
These are retained by plastic engaging the undercut gingival to the contact point
if OH is poor, then hyperplastic gingivae, this can obliterate the areas of undercut
What are bonded retainers?
wire bonded to teeth with composite - OH more difficult, caries, need routine checks
When to use bonded retainers?
when there’s a high risk of relapse and final result is unstable
Closure of spaced dentition (median diastemer)
Following correction of severely rotated teeth
Where there has been substantial movement of the lower labial segment
Where an overjet has been reduced, but lips still incompetent
Combined perio and ortho cases where reduced perio support makes relapse more likely
What are the problems with bonded retainers?
Technique sensitive process
Can cause periodontitis and caries if OH not maintained
Need to be reviewed regularly for bond failure
What is the retainer regime?
12 hours/day for the 1st day
Alternate nights for the 2nd year
Gradual withdrawal, minimum 1 night a week
What does the retain regime depend on?
The stability of the result
Which cases will have a high relapse potential?
Periodontally involved teeth
Midline diastema
Severe rotations
Teeth out of zone of stability with soft tissues - proclined lower incisors
What is a Pericision (circumferential supracrestal fibrotomy)
Adjunct to an retention procedure after correction of rotations - performed to counter the relapse tendency of the stretched gingival fibres
Surgical sectioning of gingical fibres
Performed a few weeks before removal of ortho applicance or at the same time it is removed
Retainer must be inserted immediately
