OB Reduction

Question 1

Overbite

Answer 1

• vertical overlap of maxillary upper incisor to mandibular incisors

Question 2

Cause of Increased OB

Answer 2

• Skeletal
• Dental

Question 3

Skeletal cause

Answer 3

• Excessive growth of mandibular ramus
• short mandibular body
• Backward growth rotation

Question 4

Dental Example

Answer 4

• Over eruption of anterior teeth
• Retroclined upper anterior teeth
• loss of posterior teeth

Question 5

Overbite reduction depends on?

Answer 5

• Vertical skeletal pattern
• Inclination of incisors
• Crowding
• Growth

Question 6

Aim of OB reduction mechanism

Answer 6

• flatten occlusal plane

Question 7

Means of overbite reduction?

Answer 7

• Extrusion / uprighting posterior teeth
• Intrusion of incisors/ canine
• Proclination of lower incisors

If sever - Orthognathic surgery

Question 8

Method of overbite reduction?

Answer 8

• 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

Question 9

Removable anterior bite plane

Answer 9

• Very effective in growing patient
• Hold vertical position of lower incisor
• Encourage eruption of posterior teeth
• Lab instruction : anterior Bite plane OJ+2mm

Question 10

Fixed anterior bite plane

Answer 10

• 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

Question 11

Continuous Archwire

Answer 11

• 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.

Question 12

Flat archwire

Answer 12

• Intrude lower incisors.
• Extrude posterior teeth.
• Best in growing patient.
• Bond/ band lower second molars.

Question 13

Curve of spee

Answer 13

• Further intrusions in incisors
• Extrusion of premolars
• Beware LLS Proclination

Question 14

Class 2 Intermaxillary elastics

Answer 14

• 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.

Question 15

Best way to reduce overbite cases

Answer 15

• Run lower fixed with upper removable appliance. When lower in heavy wire stop URA and go into upper fixed appliance

Question 16

Bonding and banding 7s

Answer 16

• 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.

Question 17

Bonding 7s - bite opening

Answer 17

• Harradine and Birnie
  Suggests that bonding lower 7s contribute Little to bite opening effect

Question 18

Sectional Mechanism for OB reduction

Answer 18

• Ricketts utility arch
• Not often used
• bonding molars and incisors it Encourage intrusion

Question 19

Segmental mechanism with cont wire with Reverse curve of spee

Answer 19

• 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

Question 20

Average OB

Answer 20

• 1/3 of clinical crown height of mandibular incisors
• 2-3mm coverage