1. Arch lengthening and expansion

2. Arch lengthening
Increasing the arch length using distal movement of posterior teeth or proclination of incisors

3. Arch expansion
Management of “narrow” arches by increasing the upper or lower intercanine, inter-premolar and/or inter-molar width

4. Arch width changes with age
Male arches wider than female
Lower intercanine width increases up to change to permanent dentition
Upper and lower inter-molar width increases between ages 7 to 18
Little change in premolar width after age 12

5. Arch expansion

6. Indications for arch expansion
Correction of posterior cross-bite
Elimination of a displacement
Avoiding creation of a cross-bite in cases needing distal movement of upper buccal segments
“V” shaped arch in a thumb-sucker

8. Preparation for a bone graft in a cleft alveolus
Child with < 31mm of inter-molar width at age 7 yrs. Is unlikely to attain adequate arch dimensions through normal growth alone
Minimal crowding in upper arch (1-2 mm)
Interceptive orthodontics

9. Mobilization of maxillary sutural system for orthopedic correction of early CL III
Initial preparation for functional jaw orthopedics (FR III), facial mask therapy and orthognathic surgery

10. Clinical points
Expansion where posterior teeth are tilted lingually may be expected to be stable
Stable expansion of lower intercanine width unlikely unless canines lingually displaced
Expansion more likely to be stable in absence of extractions

12. Correction of bilateral cross-bites is controversial: they may be left untreated if there is no displacement – the decision will depend on the pre-treatment inclination of the teeth and width of the underlying maxilla
Over-expansion is advisable in anticipation of some relapse
Increase in inter-molar width produces linear reduction in arch depth

13. 1mm of arch expansion causes 0
1mm of arch expansion causes 0.3mm reduction in arch length ( equates to 0.6 mm space creation within the arch)
Claims that expansion improves nasal respiration equivocal

15. relapse
Up to 40 % relapse has been found with all forms of active expansion
Occurs via lingual tilting of molars
Relapse less with fixed retainer than URA

16. complications Over expansion can cause scissors bite
Possible periodontal damage (equivocal evidence)
Increase in MMP angle and lower face height thus worsening AOB

18. Appliances used for maxillary expansion

19. URA
Design consists of an acrylic base plate which incorporates springs and retention clasps
Relies on patient to turn screw two quarter turns per week
Needs adequate seating and retention to produce expansion as the main effect is that of tipping
Coffin springs are less well tolerated and retained but can provide differential expansion laterally and anteroposteriorly
Coffin springs provide a continuous as opposed to interrupted orthodontic force

22. Rapid maxillary expander
Design consists of an active plate, which incorporates a jackscrew which is attached to the teeth with wirework or acrylic
Patient turns a “Hyrax” screw once a day ( mm/day) for 1-3 weeks (midline diastema develops quickly)
May produce more bodily movement than other appliances
There is evidence that mid palatal suture does split producing maxillary expansion

25. RME contd. Limitations are : Amount of available bone for expansion
Controversial evidence: Î periodontal breakdown compared with URA
Care in choosing age for RME, due to Î resistance to maxillary base expansion which needs prolonged retention

27. RME contd.
Bonded acrylic RME has occlusal coverage to reduce tipping and extrusion of molars
No significant differences between bonded and banded RME

28. Surgically assisted RME
To overcome problems of expansion in non growing patients
Use buccal corticotomy or Le Forte 1 osteotomy and/or midpalatal splits in conjunction with “hyrax” screw
Claims:
Less periodontal support loss unsubstantiated
Increase in nasal air flow unsubstantiated

29. Evidence :
Surgical and non-surgical techniques ; no difference in stability of expansion after one year
Non-surgical expansion allows sufficient expansion in adults
Problems :
Surgical procedure associated with morbidity and risks
Risk of nasal septum deviation

30. Quad /tri /bi helix
Bi-helix used in mandibular arch in grossly narrowed or distorted arches, or to aid correction of a severe scissors bite
Some differential expansion of inter-molar width possible (however changes in patient’s original archform may not be stable)
Quad helix / tri helix fixed or removable, are useful in cleft cases
Activated by half a tooth’s width on either side
Provides some differential expansion and can derotate molars
May produce less dental tipping than URA
Unlike URA ,fixed quad helix is not reliable on patient’s compliance

33. Fixed appliances
Limited amount of expansion possible with fixed appliance alone
Requires rectangular wire to prevent unfavorable dental tipping
Unilateral expansion possible but requires placement of buccal root torque on correct side to prevent tipping

34. Functional appliances
Produce active expansion ( usually with either expansion screw or palatal arch) to prevent cross bite formation whilst a CL I relation is being obtained
Frankel appliance produces passive expansion only by removing influence of buccal tissues with buccal shields

39. Arch lengthening

40. indications Non extraction cases with only very mild crowding (1-2 mm)
Any change in original arch form is likely to collapse, so lengthening must be kept to a minimum
Half unit CL II molar relationship in a non-extraction case
Correction of incisal relationship in CL III case by proclination if upper incisors
Regain space lost by early loss of deciduous teeth
Correction of retroclined mandibular incisors in CL II/2 cases,or CL II/1 cases with mandibular incisors trapped in palate

41. Arch lengthening procedures
Distalisation of upper buccal segments
Distalisation of lower buccal segments
Proclination of upper or lower incisors

42. Distalisation of upper buccal segments
HG with URA ( palatal finger springs to upper 6s, bite plane, HG to 6s tubes)
HG with no URA – HG to 6s tubes only. May take longer as there is no finger springs to prevent to prevent relapse during the day when HG is not worn
Distalising super elastic Nickel titanium coil springs
Magnets supported with CL II traction
Active palatal arch (TPA)

47. Distalisation of lower buccal segments
Lip bumper ; not well tolerated
Removable appliance and HG

49. Proclination of upper or lower incisors
URA ( split screw anteriorly, “Z” springs or “T” springs)
ELSA (expansion and labial segment alignment appliance); recurved spring or “wiper” arms to procline incisors
Labial crown torque ( rectangular wire in FA )
Avoiding the use of “lace backs” in CL III maxillary incisors
Side effect of some FA is to procline the mandibular incisors if there is no incisal capping