What is a labial bow?
A largely horizontal wire labial to the incisor teeth
Describe the objectives the labial bow achieves?
Retention - holding the appliance up anteriorly
Guidance - of canines during retraction
Active - retracting the incisors
Retention - holding the corrected teeth in their new position
Which functions of a removable appliance does a labial bow fulfil?
Active and retentive components
What do these show?
Left - High labial bow - only suited to be used as an active component
Right - Reverse looped bow - this is more versatile
Describe retention in the labial bow?
Picture shows example of labial bow positions relative to the normally angulated central incisor
A high (gingival) position may engage some undercut
The bow is too flexible and the undercut too little to provide good retention
How can the labial bow be adjusted?
What are the alternative anterior retainers to the labial bow?
Southend clasp and Adams anterior clasp
Southend clasp is the anterior retainer of choice It is stiff and engages a lot of undercut
Describe control of tooth movement and the labial bow?
Action is hard to classify
A labial bow can guide canine retraction
1) Teeth move at right angles to point of contact of the spring
2) Where the line of force does not pass through the centre of resistance the tooth will rotate
REMEMBER - teeth move at right angles to the surface of the tooth where the spring contacts the tooth - this is not necessarily in the same direction as the spring moves as it goes passive
Labial bow can prevent the canine escaping labially and lessen any tendency to rotate
How is the labial bow used in incisor retraction in treatment of Class II Div I?
Retract upper canines and reduce overbite
Retract proclined incisors
What thickness of wire is used to make labial bows?
For retention we need: stiff (thick) wire
For guiding a canine we need: stiff (thick) wire
For retracting incisors we need: flexible wire
For retaining tooth positions we need: stiff (thick) wire
What is happening here?
Labial bow is being split to make it much more flexible
When the labial bow is being used for incisor retraction how is it activated?
Incisor retraction activate 3mm to get the right force level and a good range of action
How can the bow be made stiffer for retention of tooth movements?
Soldering the ends together
What is happening in this image?
Treatment of Class II Div I with a URA - this is not a frequent method these days, but can still work well in the right case and involves many important principles
What are the common faults in labial bow construction?
Tag in wrong place Kinked bow