1. Charles Tweed made significant contributions to orthodontics including popularizing premolar extractions and developing the diagnostic facial triangle and Tweed's occlusion. 2. Tweed's occlusion involves positioning the mandibular arch flat and the maxillary arch with an accentuated curve of Spee, resulting in a disclusion of the second molars and distal cusps of the first molars. 3. Tweed developed this occlusion to allow the muscles of mastication to effect the greatest force on the primary chewing table while also achieving stability, function, and esthetics.

1. Guided by: Presented by:
Dr. Mridula Trehan. Dr. Deeksha Bhanotia
Professor & HOD MDS First Year.
Department of Orthodontics
& Dentofacial Orthopaedics.
1

2.  Historical Perspective
 Tweed’s Contribution to Orthodontic Speciality
 The Diagnostic Facial Triangle
 Facial Growth trends
 Tweed’s Occlusion
 Case Treated with Tweed’s Occlusion
 Conclusion
2

3. Historical Perspective:
Charles H. Tweed graduated from a improvised
Angle course given by GEORGE HAHN in 1928,
when he was 33 years old.
Angle admired TWEED’s ability , he asked him to
help in article, published in DENTAL COSMOS.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 634-635 3

4. He returned to Arizona and started 1st edgewise
specialty practice in United State.
 On august 11, 1930 Angle died at the age of 75.
 In 1932 ,Tweed published 1st article in ANGLE
ORTHODONTICS.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 634-635 4

5.  TWEED held to ANGLE’S firm conviction that one
must never extract the teeth.
 But the result was very unsatisfactory, and he almost
gave up the orthodontic practice.
 He observed that
 1) in the analysis of non extraction cases,
only 20% was successful.
 2) upright mandibular incisors are related to
post treatment facial balance and harmony.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 634-635 5

6. He concluded that one should prepare the anchorage
and extract the teeth where needed.
He retreated his 80% of failure cases with the
extraction of 4 first premolar.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 634-635 6

7. In 1936, Tweed published his first paper on EXTRACTION OF
TEETH FOR ORTHODONTIC MALOCCLUSION
CORRECTION.
MOTHER ANGLE refused to attend the lecture and GEORGE
HANN criticized him severely.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 634-635
7

8. In 1940, Tweed presented a paper and display his case
report in meeting of ANGLE SOCIETY in CHIKAGO.
In this way, Tweed’s philosophy was born.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 634-635 8

9. Tweed was considered the premier edgewise
orthodontist of those day.
He devoted 42 years of his life in advancement of
edgewise appliance and died on 11 January 1970.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and
Technique (2nd edn).St Louis, Mosby 1994: 634-635
9

10. 1. Emphasized the four objectives of orthodontic
treatment—esthetic, health, function and stability
with emphasis and concern for facial esthetic.
2. Developed the concept of uprighting teeth over basal
bone with emphasis on mandibular incisors.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and Technique
(2nd edn).St Louis, Mosby 1994: 636-637.
10

11. 3.Made the extraction of teeth for orthodontic
correction acceptable, and popularized the extraction
of the first premolars.
4.Enhanced the clinical application of
cephalometrics.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and
Technique (2nd edn).St Louis, Mosby 1994: 636-637.
11

12. 5.Developed the diagnostic facial triangle to make
cephalometrics a diagnostic tool, as well as a guide in
treatment and an evaluation of treatment results.
6.Developed a concept of orderly treatment procedures
and introduced anchorage preparation as a major step in
treatment.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and
Technique (2nd edn).St Louis, Mosby 1994: 636-637. 12

13. 7. Developed a fundamentally sound and consistent pre
orthodontic guidance program using and popularizing
serial extraction of primary and permanent teeth.
Graber TM, Vanarsdall RL. Orthodontics: Current Principles and
Technique (2nd edn).St Louis, Mosby 1994: 636-637.
13

14.  Four angles will be referred to repeatedly during the
discussion of clinical orthodontic procedures.
 They are as follows:
1. Frankfort mandibular plane angle---FMA.
2. Mandibular incisor plane angle---IMPA.
3. Frankfort mandibular incisor angle---FMIA.
4. SNA–SNB(Down’s)---ANB.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 6-12 14

15.  The Frankfort plane is established by connecting a
point 4.5mm above the geometric center of the ear rod
and an orbitale point midway between left and right
lower borders of the orbits.
 The mandibular plane is drawn along the lower border
of the mandible and is extended posteriorly to connect
with the Frankfort plane.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2:6-12 15
Porion Orbitale
menton
Gonion

16.  Anteriorly it connects with menton, and posteriorly it
bisects the distance between the right and left lower
borders of the mandible in the region of the gonial
angle.
 The third plane of the triangle is made by extending the
long axis of the mandibular CI downward to the
mandibular plane and upward to the Frankfort plane.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2:6-12 16

17.  Angle ANB is important .
 It expresses mesiodistal relationship of the maxillary
and mandibular basal bones.
 Range is : 5to -2 degree.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2:6-12 17

18.  Essentially, Tweed described the growth of the face as
being normal when mandible and face grow in unison
in downward and forward direction with no change in
angle ANB.
Kharbanda OP.Orthodontics Diagnosis and Management of malocclusion
and Dentofacial Deformities.Elsevier 2020;3:574 18

19. CLASSIFICATION OF FACIAL GROWTH TRENDS
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26 19

20. Type A :
 Middle and lower face grows in forward
and downward in unison with no change in size of
ANB angle.
 Growth is approximately equal in both
vertical and horizontal dimension.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26
20

21.  Prognosis is good because the point B is
moving forwards as the maxillary denture
is moved posteriorly.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26
21

22. Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26 22

23.  Middle face grows more rapidly than the lower
face.
 Growth occurs predominantly in the vertical
dimension.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26
23

24. Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26 24
ANB<4 ANB from 7 to 12

25. Lower face growing downward and forward
more rapidly than the middle face with
decrease size of ANB angle.
Growth occurs predominantly in the
horizontal direction.
Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2: 13-26
25

26. Tweed C.H.Clinical Orthodontics.St Louis, Mosby 1966;2:13-26
26
Growth is Confined to
Horizontal Dimension,
regardless of the size of
Frankfort Mandibular
Angle (FMA)

27. Tweed’s occlusion refers to that set of occlusion in which
the teeth are positioned with the mandibular arch flat while
the maxillary arch exhibits an accentuated curve of Spee.
Klontz H.A.Readout.Charles Tweed Foundation:53-64. 27

28.  "Tweed occlusion," properly identified as transitional
occlusion, is characterized by a disclusion of the
second molars and the distal cusps of the first molars.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267. 28

29.  The mesio lingual cusp of the maxillary first molar is
seated into the central fossa of the mandibular first
molar with the mesial inclined plane of the mesial cusp
of the maxillary first molar contacting the distal
inclined plane of the mesial cusp of the mandibular
first molar.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267.
29

30.  The maxillary second premolar buccal cusp contacts
the distal inclined plane of the mandibular second
premolar buccal cusp, while the distal inclined plane of
the maxillary second premolar buccal cusp contacts the
mesial inclined plane of the mesial buccal cusp of the
mandibular first molar.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267.
30

31. The anterior part of the denture is guided by the
Tweed’s triangle , while the necessary inclinations of
posterior teeth are monitored with read out.
Read out is a very effective and easily used clinical
procedure for monitoring all second order tooth movement.
This control makes it possible to place the posterior teeth to a
predetermined position.
Fig: Range of ideally tipped maxillary and mandibular posterior teeth.
Klontz H.A.Readout.Charles Tweed Foundation:53-64.
31

32. Once the case has been over treated to Tweed’s
Occlusion, finishing wires are fabricated to maintain all
the distal tips in both maxillary and mandibular arch.
Klontz H.A.Readout.Charles Tweed Foundation:53-64. 32

33.  This arrangement allows the muscles of mastication
to effect the greatest force on the "primary chewing
table" in the mid arch area.
 The slightly intruded distally inclined maxillary and
mandibular second molars can now re-erupt to a
healthy functional occlusion without trauma or
premature contact.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267.
Distally inclined
33

34.  . Because of overtreatment of Class I and Class II
"deep-bite" patients, the anterior teeth are positioned in
an end-to-end relationship with no overbite or
overjet.
This relationship, however, is transitory and will
rapidly adjust to an ideal overjet and overbite
relationship.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267.
34

35. Tweed occlusion is further characterized by a
balanced skeleto-facial complex because the denture
is positioned upright over basal bone for maximum
stability and esthetics.
The muscles of swallowing, expression, and
mastication are actively involved in determining the
final stable, esthetic relationship of the teeth, referred
to as functional occlusion.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267. 35

36. The concept of a transitional occlusion followed by
a period of recovery is based on the belief that each
individual's own oral environment will determine the
ultimate position of the dentition and that
overtreatment allows the patient the greatest
opportunity for maximum stability and functional
efficiency.
Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars
in Orthodontics.1996;2:254-267. 36

37.  After finalizing, idealizing and proper cusp seating, the
appliance is removed and the case is put into retainers
for recovery.
Fig: Model comparision between pre treatment, post treatment and recovery.
Klontz H.A.Readout.Charles Tweed Foundation:53-64. 37

38. Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267.
Pre-Treatment Photographs
and Casts.
38

39. Klontz H.A.Tweed –Merrifield Sequential Directional Force Treatment.Seminars in
Orthodontics.1996;2:254-267. 39

40. The orthodontist should not strive for the ideal final
result at the end of treatment. The ideal result will
occur after all treatment mechanics are discontinued
and uninhibited function and other environmental
influences, active in the post treatment period, stabilize,
and finalize the position of the total dentition.
40

41.  When all appliances are removed and the retainers
are placed, the most critical "recovery" phase occurs.
The latter is the recovery period, and the forces
involved are those of the surrounding environment,
primarily the muscles and the periodontium. If
mechanical corrective procedures barely achieve
normal relationships of the teeth, there will be
inevitable relapse. Hence overcorrection of the finished
dental arches are done to prevent relapse.
41

42. 1. Graber TM, Vanarsdall RL. Orthodontics: Current
Principles and Technique (2nd edn).St Louis, Mosby 1994:
634-635.
2. Tweed C.H.Clinical Orthodontics.St Louis, Mosby
1966;2:6-26.
3. Klontz H.A.Tweed –Merrifield Sequential Directional
Force Treatment.Seminars in Orthodontics.1996;2:254-
267.
4. KlontzH.A.Readout.Charles Tweed Foundation:53-64.
5. Kharbanda OP.Orthodontics Diagnosis and Management of
malocclusion and Dentofacial Deformities.Elsevier 2020;3:574
42

43. 43