OB Reduction Flashcards
Overbite
- vertical overlap of maxillary upper incisor to mandibular incisors
Cause of Increased OB
- Skeletal
- Dental
20%
Skeletal cause
- Excessive growth of mandibular ramus
- short mandibular body
- anterior growth rotation
Dental Example
- Over eruption of anterior teeth
- Retroclined upper anterior teeth
- loss of posterior teeth
Overbite reduction depends on?
- Vertical skeletal pattern
- Inclination of incisors
- Crowding
- Growth
Aim of OB reduction mechanism
- flatten occlusal plane
Means of overbite reduction?
- Extrusion / uprighting posterior teeth
- Intrusion of incisors/ canine
- Proclination of lower incisors
If sever - Orthognathic surgery
Method of overbite reduction?
- URA with anterior bite plan
- Fixed anterior bite plane I.g bite turbos
- Lower arch wire in reverse curve of spee
- upper arch wire with increased curve of Spee
- Class II elastics
- Bonding lower second molars
- Sectional mechanism
- Orthognathic
Removable anterior bite plane
- Very effective in growing patient
- Hold vertical position of lower incisor
- Encourage eruption of posterior teeth
- Lab instruction : anterior Bite plane OJ+2mm
Fixed anterior bite plane
- Composite and metal bite turbos
- Hold vertical position of lower incisors
- Encourage eruption of posterior teeth
- 2 potential Issue- Inhalation risk and difficult to remove
- Advantage- no patient compliance required
Continuous Archwire
- Flat SS arch wire or with
Upper - increased curve of spee
Lower- Reverse curve of spee - Rocking chair Niti lower
If left in situ for too long can cause premolar expansion and distolingual molar rotation. - Both above method results - Proclination of LLS due to labial crown tipping.
Flat archwire
- Intrude lower incisors.
- Extrude posterior teeth.
- Best in growing patient.
- Bond/ band lower second molars.
Curve of spee
- Further intrusions in incisors
- Extrusion of premolars
- Beware LLS Proclination
Class 2 Intermaxillary elastics
- Effecting at extruding lower molars
- They also extrude upper incisors but:
1- This can be limited by adding a Curve of spee to upper wire
2- 1mm of molar extrusion will have greater effect on opening the bite as the molar is closer to the condylar hinge axis.
Best way to reduce overbite cases
- Run lower fixed with upper removable appliance. When lower in heavy wire stop URA and go into upper fixed appliance
Bonding and banding 7s
- Adding these most posterior teeth means that molar extrusion is more distal therefore maximise “ wedge “ occlusal effect
- Additional vertical posterior Anchorage = less molar extrusion and more incisal intrusion.
Bonding 7s - bite opening
- Harradine and Birnie
Suggests that bonding lower 7s contribute Little to bite opening effect
Sectional Mechanism for OB reduction
- Ricketts utility arch
- Not often used
- bonding molars and incisors it Encourage intrusion
Segmental mechanism with cont wire with Reverse curve of spee
- ADVANTAGES : More rapid Intrusion and longer range of action of wire
- longer range of action of wire
-DISADVANTAGE: increased chair time, more difficult oh , potential patient discomfort if wire impinges on mucosa, Second phase require reunite labial and buccal segments, greater potential for over correction
Average OB
- 1/3 of clinical crown height of mandibular incisors
- 2-3mm coverage