Posterior Crossbites

Question 0

What are the characteristics of a crossbite due to a deficiency in the maxillary basal bone width?

Answer 0

1) Molar axial inclinations are upright or bucally flared
2) Frequently bilateral
3) Palatal vault high and constricted

Question 1

How can posterior crossbites be classified?

Answer 1

1) Dental arch/ alveolar bone width deficiency
- bu-li axial inclinations of teeth in crossbite tend to be upright or palatally tipped
- appears unilateral but may be bilateral
- palatal vault often not constricted
2) Deficient maxillary basal bone width

Question 2

what are the characteristics of a dento-alveolar crossbite?

Answer 2

• arch narrowness
• premature contacts in centric relation
• slide to a bite of convenience

Question 3

what are the characteristics of a posterior crossbite?

Answer 3

• mandibular closure deviation

- if severe, might not necessarily show a deviation

Question 4

What are the reasons for treating a posterior crossbite?

Answer 4

1) aesthetics, function but with less emphasis on aesthetics

2) Growth and development

Question 5

What kind of appliances can be used to treat a dento-alveolar crossbite?

Answer 5

1) SME (expansion screw twice a week for 3-4 mmonths)
2) Expanded lingual arch
3) Coffin spring
4) Quad-helix appliance
5) Cross-elastics (strong elastics - 200g)
6) RME

Question 6

If using an SME to treat a posterior crossbite, what should be taken into account?

Answer 6

• good retention
• expansion screw turned twice per week for 3-4 months
• overexpansion to compensate for relapse
• rarely use a posterior bite plane

Question 7

How should RME be carried out and what does it actually do?

Answer 7

• two turns per day for 2-3 weeks
• splits the midpalatal suture and can result in an upper central diastema
• shouldnt hurt
• if the suture doesnt splint, can result in a lot of pain and alveolar fractures
• can sometimes result in easier breathing for patients

Question 8

what are the types of RME’s availible?

Answer 8

1) Hyrax type
- bands on molars and premolars
- centreally located expansion screw
- 0.9mm wire
- two turns a day
2) Haas type
- basically the same with palatal acrylic pads

Question 9

What are the indications for RME?

Answer 9

1) Occlusion
2) Respiriation
3) MIdface deficiency

Question 10

What are some problems asscociated with RMEs?

Answer 10

• oral hygiene
• length of fixation
• dislodgement and breakage
• tissue damage
• infection
• failure of suture to open