Tweeds

Philosophies Of Dr.Charles Tweed
www.indiandentalacademy.com

Dr.Charles H. Tweed – Arizona
1966-published
Charles H. Tweed foundation.

Anchorage preparations.
Can be classified into three categories:
First degree
Second degree
Third degree

First degree anchorage preparation.
Applicable to all malocclusions with ANB angles ranging
from 0* to 4*,in which facial esthetics are good and in
which total discrepancy does not exceed 10 mm.
First degree means the mandibular terminal molars must
always be upright and maintained in such an upright
position as to prevent their being elongated when a class
II intermaxillary elastic force is used.
The inclinations of the mandibular terminal molar is such
that the direction of pull of the intermaxillary elastic
force during function will not exceed 90* when related to
the long axis of those teeth.

Second degree anchorage preparation.
Malocclusions in which the ANB exceeds 4.5* and facial
esthetics make it desirable to move point B anteriorly and
point A posteriorly.
Usually class II in nature.The degree of distal tipping of
the mandibular terminal molars is more severe than is
necessary in first degree anchorage preparation.
The direction of pull of the class II intermaxillary elastics
when related to the long axis of the terminal molars
should be greater than 90* so that the terminal molars will
be further depressed rather than elongated.

Third degree or total anchorage preparation.
Necessary in extremely severe malocclusions in which total
discrepancies vary from 14 to 20 mm or more but the ANB
angle does not exceed 5*.
In the permanent dentition these cases are as a general
rule,class I in nature with exceedingly irregular teeth.
All three posterior teeth from and including the second
premolar teeth to the terminal molars must be tipped
distally to the anchorage preparation positions.

Classification of Growth trends.
A lateral cephalogram should be included in the
records of all young patients undergoing a pre
orthodontic guidance program.
Some 12 to 18 months later, a second head plate should
be taken and tracings made of both cephalograms.
These tracings are superimposed on S-N with S as the
reference point.
The face of all children grow downward and forward in
one of the three ways.
Type A, Type B and Type C.

Type A growth trend.
The middle and lower third of the face are growing in
unison downwards and forwards, with no change in the
size of the ANB angle.
Growth is approximately equal in both vertical and
horizontal dimensions. 25% of the patients present this
type of growth trend.
If the case is class I with ANB not exceeding 4.5* ,no
treatment is indicated until the full eruption of all
permanent cuspids.
If the case is class II and ANB exceeds 4.5*,the patient
has a type A subdivision growth trend.www.indiandentalacademy.com

The class II molar relationship is corrected with serial
extraction procedures in combination with head gear.
Facial changes vary from good to dramatic and the
mandibular incisors remain stable and free from
crowding because both mid and lower face are growing
forward in unison with no conflict between maxillary
and mandibular incisors.

Type B growth trend
Cases accompanied by ANB readings from 6* to 12*.
Pre orthodontic tracings reveal that growth is downward
and forward,with the middle face growing more rapidly
than the lower as designated by an increase in the size of
ANB-the growth trend is type B and undesirable.
If the ANB is less than 4* the prognosis is fair and on the
other hand,if the ANB ranges from 7* to as much as 12*
prognosis is poor.
Extraction of all first premolars is mandatory for patients
with high ANB angles.

Point B will always drop down and back as a result of
treatment.
Growth of the middle and lower face is predominantly in
the vertical dimension.

Type C growth trend.
Lower face is growing downward and forward more
rapidly than the middle face,with a decrease in the
size of the ANB reading ,the growth is type C.
Because the lower face is growing forward at a more
rapid pace than the mid face,the cutting edges of the
mandibular incisors engage the lingual surfaces of
the maxillary incisors.
The mandibular incisors are tipped lingually or the
maxillary incisors are tipped labially.
60% of all patients have type C growth trends.

Regardless of the size of the FMA,when growth is
virtually confined to the horizontal dimensions,with
little vertical growth,the growth trend is classified ae
Type C subdivision.

Development of diagnostic facial triangle.
Analysis of clinical results.
Tweed began an analysis of his practice results.This
project called for dental casts.photographs and x ray
films of all patients.
Patients possesing balance and harmony of facial
proportions had mandibular incisors that were upright
over the basal bone.
Tweed suggests that the position of the mandibular
incisors over basal bone should be in the range of 90* +/-
5 * to attain ideal facial esthetics.

FMA,IMPA
FMIA.
The angle ANB is very important as it
expresses the mesiodistal relationship of
maxillary and mandibular basal bones.Range
was 5* to –2*.www.indiandentalacademy.com

Concept of the normal.
The term normal is the balance and harmony of
proportions generally accepted as the most pleasing to the
human face.
The clinical research concluded that the normal range of
inclinations of the mandibular incisors when related to the
mandibular plane was 90* =/- 5*.
The first angle IMPA was finally established after clinical
research covering a period of approximately 12 yrs.

THE FRANKFORT MANDIBULAR PLANE
ANGLE
Patients were placed on the head holder with head
oriented on the frankfort horizontal plane.Using the
thumb and forefinger,the mandibular border was
extended posteriorly to connect the frankfort plane.

The normal variation of FMA was 16 * to 35* with
average norm for that angle 25*.
Tweed also concluded that percentagewise more
extraction of teeth was necessary in patients with an
FMA that ranged upward from 30*.
Dr. Tweed further concluded that when the FMA ranges
upward from 35*,it becomes so steep that it is a physical
impossibility to fully compensate the lower
incisors,prognosis is not good.
The result of this research was the establishment of the
norm for the FMA as 25* and the normal variation of
that angle is 16* to 35*.(second angle of diagnostic facial
triangle). www.indiandentalacademy.com

The sum of all the angles of a triangle is 180*.If the
norm for IMPA is established at 90* and the norm for
FMA at 25*,the third angle FMIA must be 65*.
When the patient presented an FMA of 30*,which is
5* larger than the norm for that angle,it was found
expedient to tip the mandibular incisors lingually from
90* to 85*,This maintained the norm of 65* for the
FMIA.
As long as it is physically possible to make this
compensation,patients with a large FMA and a low
ANB angle can be treated with satisfactory facial
esthetics.

Cephalometric appraisal of previous clinical
research.Observations made were:
1.Those samples in whom the FMA ranged upward from
30* demonstrates natures compensation of the
inclinations of the mandibular incisors to the extent that
their inclinations when related to the mandibular plane
read as little as 77* and the FMIA hovered around 65*.
2. Those samples in whom the FMA read 25* displayed
FMIA readings ranging from 65* to 70*,the average
being 68*.
3.Those samples with an acute FMA that ranged
downward from 20* rarely demonstrated axial
inclinations greater than 94*.www.indiandentalacademy.com

Mechanics of treatment
Make one band for one central
incisor tooth.Form and place
the band so that the distance
from the incisal edge of the
bracket slot is 3.5mm.Each of
these teeth upto the premolars
carry one single width anterior
edgewise bracket positioned on
the greatest contour of the
labial or buccal surface.

The mesial bracket on the first molars should line
up with the mesiobuccal cusp.The second bracket
is soldered 1.5 mm distal to the first bracket.
The molar tube is 4.5mm in length and is soldered
to the second molar band.Line the sheath parallel
to the occlusal margin of the band at the junction
of the upper and middle third of the tooth
occlusogingivally.
Mandibular intermaxillary hooks made of heavy
0.032 inch brass wire are soldered gingivally to
the molar tube.

Maxillary arch.
The identical procedure outlined for
mandibular band placement is followed.
The maxillary lateral incisor bands are
placed so that the distance from the
incisal edge of the tooth to the incisal
edge of the bracket slot is 3 mm rather
than 3.5 mm.

Steps in wire bending:
1.Bonwill hawley chart formation
2.First order bends –maxillary arch and
mandibular arch.

3.Second order bends –maxillary and mandibular arch
V bend and distal tipping bends.

Third order bends.
Placing lingual root torque in maxillary anterior
segment.

Bent in stop loop formation – allows ligatures to be
securely tied.
Formation of resilient vertical loops.
5 mm in length ,shoulders square,base rounded,legs parallel
and 1.25 mm apart.

Analysis of second order bends.
Second order or tip back bends are used to prepare
anchorage in the mandibular arch.
An ideal 0.020 * 0.025” arch wire is used and co
ordinated second order bends arte bent into the wire.The
degree of tip back is such that when the arch wire is
placed in the buccal tubes of the molars it will cross the
cuspid teeth at their dentino enamel junctions.

The arch wire is then raised and ligated to the
two brackets on the first molar teeth.The mesial
cusps of the terminal molars are elevated and
the first molars are depressed.
When the arch wire is placed in the slots of
second premolar brackets,the first molars are
elevated and the second premolars are
depressed.
Thus the force tipping the terminal molars are
transferred to the cuspid teeth which in reality
are the teeth tipping the molars distally.www.indiandentalacademy.com

The reason for V notch in the arch wire between the
cuspid and lateral incisor brackets is to maintain the
bracket slots on the lateral and central incisors in the
same plane as that of the canine bracket.
Thus the three anterior teeth will act as a single unit to
resist the depressing action occassioned by the distal
tipping of the terminal molars.

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