Orthodontic

1. PROF DR HLA HLA YEE

2. Space discrepancies
(space deficiency)
 Up to 4mm
(mild crowding)
 5mm to 9mm
(moderate crowding)
Treatment Protocol
 Non-extraction
 Disking
 Expansion
(except for third molar)
 Non-extraction
 Expansion
or
 Extraction of some teeth
other than third molar

3.  10mm or more
(severe crowding)
 Extraction regardless
of what happen to
third molar at later
state

4. DECISION FOR EXTRACTION AND NON-EXTRACTION
Depends on :
Dimension of the dentition (or denture)
(1) Anterior dimension or boundaries
(2) Posterior dimension or limitation
(3) Vertical dimension
(4) Lateral or transverse dimension

5. (1) Anterior dimension or boundaries
 Tweed defined the anterior limit of the dentition.
(Anterior limit of the denture base and the correct
inclination of the mandibular incisors on the bony
base.)
 The Tweed cephalometric triangle is constructed.
 This triangle is based upon the Frankfort horizontal
plane , the mandibular plane and the axis of the
mandibular incisor.

6.  FMPA is 20 – 29 degree ----- FMIA should be 68 degree.
 FMPA is 20 degree or less ----- IMPA is 91 degree.
 FMPA is 30 degree or more ----- FMIA should be 65
degree.
 If FMPA is low , the mandibular incisor should not be
pushed forward from their original position if the muscular
balance is normal.
 Therefore , extractions are often necessary if the anterior limit
of the dentition is to be respected in the presence of significant
anterior crowding and / or protrusion.

7. FMPAA
FMIA
IMPA
FHP
MP
Long axis
of the
lower
incisor

10. (2) Posterior dimension or limitation
 The posterior dimension of the mouth is important to
note that when non-extraction treatment is touted ,
32 teeth must be maintained in the mouth.
 The extraction of third molar is a therapeutic decision .
 If a patient has to have third molar extracted , it is
extraction treatment , not non-extraction treatment.
 The non-extraction treatment cannot be performed if the
second molars are hopelessly impacted.

12. (3)Vertical dimension.
 If the vertical dimension is increased in the posterior area
of the mouth , a long face is created . There may be more
gingival display on smiling.
 Also , if the maxillary posterior teeth are driven distally
to correct Class II malocclusion , when no space is
available , there is a wedging open effect in the anterior
vertical dimension that creates a longer face .
 Every 1 mm of vertical expansion in molar area , a
1.3 mm increase in anterior facial height occurred .

13.  Patients who need extractions but who are treated without
them are very often expanded vertically , Point B drops down
and back , poor facial esthetic is the result.
 Except in patients with deep bites who have poor vertical
development , it is crucial to preserve the vertical dimension if
stability , as well as facial balance and harmony , are the
ultimate goals.

14. (4)Lateral dimension.
 Lateral expansion is touted in many circles.
 The downward and backward mandibular rotation that
took place on the non-extraction patient.
 The extraction patient expressed downward and forward
mandibular development.
 The lower lip eversion and soft tissue imbalance on the
non-extraction patient.
 The extraction patient has improved facial balance.
 The non-extraction patient was expanded anteriorly ,
posteriorly , vertically and laterally.

15. • Arch expansion can perform in patient with narrow maxillary
arch with wide buccal corridors .

16. A B
The width of the maxillary dental arch , as seen on smile , should be
proportional to the width of the mid-face .
A – a broad smile is appropriate for a face with relatively large width across
the zygomatic arches ,
B - a narrow smile is preferred when the face width is narrow.
- this patient was appropriately treated with maxillary premolar
extraction to prevent over-expansion during treatment.