The Wits appraisal: A diagnostic aid for assessing sagittal jaw disharmony

The Wits appraisal
of jaw disharmony.
Alexander Jacobson.
AJODO-2003
Volume 124, Number-5
www.indiandentalacademy.com

• The validity of Angle ANB
as measure of sagittal
skeletal disharmony has
been criticized because it is
affected by rotations and
variations of the sagittal
and vertical jaw dimensions
relative to the cranial base.
•

• Jacobson in 1975 described a
method of assessment of sagittal
jaw relationship which aimed to
eliminate these variations by
relating A and B points to the
occlusal plane.
• This method was originally
described by Harvold in 1963.

What would you like to
choose?
• Many analyses tend to be
cumbersome and far too complex
for routine clinical use, many
measurements which do not come
up with out meaningful
information and inconsequential
details.
• Too few measurements to yield
adequate information for appraisal
of the orthodontic problem.

• The “Wits appraisal of jaw
disharmony is not an analysis
per se , rather , it is intended as
diagnostic aid whereby the
severity or degree of
anteroposterior jaw
disharmony can be measured
on a lateral cephalometric head
film.

Why the name “wits”
• Alexander Jacobson was
head of the orthodontic
department at the
university of Witwatersrand
also know as “Wits” and
that’s why the name given
to the analysis.www.indiandentalacademy.com

Cranial and denture
landmarks
• Nasion
-related functionally to the ectocranial
table of the calveria.
- growth may alter its vertical and
horizontal position in space
- conventionally regarded as the
anterior most point on the anterior cranial
base from which to relate the dentures.

• Point A
- deepest point on the counter of the
maxilla between the ANS and alveolus.
The ANS is a process , as is the alveolar
process, and between these two lies the
most basic part of the denture base at the
anterior limit.
All bone in the anterior part of the maxilla is
thin and laminated and subject to change
when upper incisor teeth are moved.
From practical standpoint, point A must be
regarded as
the anterior limit of the maxillary denture
base.

• Point B
- described by Downs in 1948 as a
point at the deepest curvature of the
outline of the symphysis of the chin.
- this point is located at the junction
of basal and alveolar bone.
- the deepening of the body of the
symphysis occurs with eruption of the
teeth.
- the bony tissue that is alveolar in
the young is incorporated into the body
and becomes basilar in the adult, so that
point B moves horizontally and vertically.

• Point B
- referred to earlier in the
anthropometric term by Bjork as
supramentale.
- as like point A, is subject to
mild change with lower incisor
movement and may be regarded as
the anterior limit of the lower
denture base.

• In appraising the horizontal
disharmony of the face, the ANB
angle is the most commonly used
measurement.
• The SNA reading, Steiner reports , is
of little concern because it merely
shows whether the face protrudes or
retrudes below the skull.

• This article endeavors to
emphasize an awareness of this
this relationship in overall
interpretation and assessment of
cephalometric analysis.
•

ANB angle as a measure of
jaw dysplasia
• Normal – 20
• >20 _
tendency towards class II
jaw disharmonies.
• <20 -
tendency towards class III
jaw discrepancy

A) Class II malocclusion
SNA/SNB – 87/80 ANB -7
B) Normal Occlusion

• A) Class II malocclusion
B) Normal Occlusion
SNA/SNB – 87/81 ANB -6www.indiandentalacademy.com

• The A/P relationship of the jaws in
these examples is satisfactorily
reflected by the ANB angle
readings. These general variants
have importance when one
endeavors to appraise degree of
craniofacial disharmony in
orthodontics.www.indiandentalacademy.com

• Relating jaws to cranial reference
planes presents inherent
inconsistencies because of
variations in facial physiognomy.
• The craniofacial variations
includes are
1) The A/P position spatial
relationship of Nasion relative to
the jaws.
2) The rotational effect of the
jaws relative to cranial reference

Tracing of a normal occlusion with all
ANB reading of
2 degrees.

This has the effect of reducing the ANB reading, in this
instance from 2 degrees to —2 degrees. A similar reduction
in the ANB reading is effected by the jaws (bearing the same
relationship to each other) being retropositioned in the
craniofacial complex. A) ANB -2 Wits-0mm B)ANB - -2,
Wits-0mm C) ANB – 5, Wits -0mmwww.indiandentalacademy.com

• C. now nasion is retro-positioned
(re-duced anterior cranial base
length). This has the effect of
increasing the ANB angle, in this
instance from 2 degrees to no less
than 5 degrees. Forward positioning
of the jaws in the craniofacial
complex would have the same effect
of increasing the ANB angle
reading.

A)AVERAGE NORMAL ANB-2, Wits-0mm
B) ROTATIONCLASS III ANB – -5, Wits-0 mm
c) CLASS II ROTATION ANB- 8, Wits- 0 mm

• Rotational effects of jaws.
Clockwise or counter-clockwise
rotation of the jaws relative to
cranial refer-ence planes (SN in
the examples cited) likewise
radically affects the ANB angle
reading.

The SN plane is superiorly tipped.

• It is the anterior part of SN plane
which is superiorly tipped. The
rotational effect of the SN line
virtually has no anteroposterior
positioning effect on nasion point in
which case the ANB angle reading is
hardly affected by any angular
deviation of SN from the horizontal.

The “Wits” appraisal of jaw
disharmony
• The “Wits” appraisal of jaw disharmony
is a measure of the extent to which the
jaws are related to each other
anteroposteriorly.

• The method of assessing the degree or
extent of the jaw disharmony entails
drawing perpendiculars on a lateral
cephalometric head film tracing from
Points A and B on the maxilla and
mandible, respectively, onto the
occlusal plane which is drawn through
the region of maximum cuspal
interdigitation The points of contact on
the occlusal Plane from Points A and B
are labeled A0 and BO, respectively.

• In a sample series of 21 adult males
selected on the basis of excellence
of occlusion it was found that Point
BO was approximate1 mm ahead of
Point AO. The calculated mean
reading was 1.17, S.D 1.9 (range, —2
to 4 mm) In twenty adult females
selected on the same basis, Points
A0 and Bo generally coincided. The
calculated mean reading was —0.10
mm, SD 1.77 (range, ~4.5 to 1.5)

• In sum, therefore, the average jaw
relationship according to the “Wits”
reading is 1 mm in males and 0 in
females, In skeletal Class II jaw
dyplasias, point BO would be located
well behind point AO (a positive
reading) whereas in skeletal Class Ill
jaw disharmonies, the “Wits” reading
would be negative, namely, point BO
being forward of’ point AO. The more
the Wits readings deviate from 1 mm
in males and 0 in females, the greater
the horizontal jaw disharmony.

Application of wits
appraisal
It shows Class ii malocclusion and the normal occlusion. The ANB
in each instance is 7 degrees According to the “Wits” appraisal,
however, the Class ii reading is 10 mm (markedly Class II), whereas
the reading for the occlusion is 0 mm

• A) Class II ANB 6 and “Wits” 6mm
• B) Same ANB and but “Wits” is 0
mm.

• Application of the “Wits” appraisal
• A and B. Here again, the ANB angle is 6
degrees whereas the “Wits” appraisal
clearly reflects the difference between
the Class II and the normal occlusion
The “Wits” reading for the Class II
malocclusion is 6 mm, whereas the
normal reading is 0 mm.

A) Class III Mild Class III with ANB -1.5 and
“Wits” - -1.5mm
B) Severe Class III where ANB is
-1 and but “Wits” is -12 mm.www.indiandentalacademy.com

A and B, shows lateral head film of two
Class III malocclusion. The ANB differ
only slightly, namely 1 degree and -1.5
degrees respectively. The “Wits
appraisal Cr, Places a completely
different complexion on the scene.
According to the “Wits” reading is – 1.5
mm, reflecting the mild discrepancy in
the relationship of the jaws to each
other where is wits reading in B is no
less than 12mm a major jaw
disharmony.

• In fact, the latter patient undergo a
bilateral mandibular Osteotomy.
The severity of the jaw disharmony
is clearly reflected, in the wits
appraisal but not so in the
conventional ANB angle reading.

• example of Class II malocclusion tracings.
The ANB instance was 9 degrees The Wits
reading in A and B, however, Were 8 and 2.5
mm respectively,www.indiandentalacademy.com

• Interpreted, this means that the
anteroposterior discrepancy in A was
severe, whereas that of B was mild
inspite of the identical ANB angle
measurement. Because of this, the high
mandibular Plane angle and the divergent
type of profile, A proved most difficult to
treat. By contrast, B proved easily
treatable, the anteroposterior
discrepancy being mild and the vertical
profile dimensions favorable.

Figure shows the lateral cephajometric head film
tracing of a patient with an ANB angle
measurement of no less than 10 degrees In Spite
of the high ANB angle, there wits reading was
only 2 mm and easily treatable.

Class II malocclusion with ANB 7 and “Wits” -
9mm
Severe Class II
B) where ANB is 7 and but “Wits” is 1 mm.

A) Class III malocclusion with ANB is 2 but “Wits is -4.5
mm suggest a definite class III skeletal disharmony.
B) ANB 0 but “Wits is -9.5 mm suggest a class III
tendency by conventional.www.indiandentalacademy.com

Follow up studies on ANB
angle and “Wits”
measurements.
• Kim and Vietas
(A/P dysplasia indicator-AJO 1978)
Mean reading in adolescent white
control group of 51 boys and 51
girls with normal occlusion is
comparable values with the
Jacobson.

• McNamara and Ellis
( Int j Adult Orthod Og surgery-
1988)
recorded the mean values –o.72 in
men and + 0.93 in women.

• The ANB angle is not only
dependant on anteroposterior
relationship of jaws but on
the inclination of the palatal
plane, maxillary prognathism,
and vertical facial dimension.

• Author stressed that not too much
importance to the ANB angle, nor
should it be considered the
absolute measurement of the
anteroposterior relationships of the
jaws. Rather it should be judged
always in respect to other
variables which have been cited.

• Binder recognized the geometric
effects at work in the ANB angle
( J Orthod – 1979)
He showed that for every 5 mm of
anterior displacement horizontally,
the ANB angle changed 2.5
degree.

• A 5 mm upward displacement of
nasion altered the ANB angle 0.5
degrees, a downward
displacement of Nasion changed
the ANB angle 1 degree

• Bishara et al ( AJO – 1983)
showed the effect on the ANB
angle of moving nasion forward
or backward 0.5 inch (12.7mm),
and vertically up or down by the
same amount.

• Sperry et al, in differential treatment
planning for mandibular
prognathism, the true dental
discrepancies can be noted relative
to the occlusal plane.
• Roth and Martina et al recognized
the ANB angle invalid measure of
sagittal skeletal disharmony. The
mean value measured by him is 0.27
which correspond to the mean value
of Jacobson.

• During the investigation there is
significant mean annual change of
0.59 mm in the wits measurement.
The angle A-B occlusal decreased
0.29 degrees per year during the
same period.

• This is contrary to the finding of
the Bishara et al who concluded
that the ANB angle significantly
change with age, where as wits
appraisal does not.

• Two factor that Roth suggests will
affect the wits reading are the
occlusal plane angle and the
vertical alveolar dimensions.

• The positive summation effect of
increasing the distance A-B and
decreasing the occlusal plane angle
demonstrated. Alteration of the vertical
jaw relationships ( increasing the
distance between two points A and B)
leads to further increase in the A-B
distance or Wits reading.

• To eliminate the influence of the
vertical relationship of points A and
B to the occlusal plane, Roth
provides an alternative procedure
where by a standard distance of 50
mm is used along A-B line, in effect
constructing phantom points with a
consistent dental relationship that
eliminates the effects of deeper
skeletal relationships.

• Roth contends that it would be
interesting if the anteroposterior effect
of Wits appraisal of treatment changes
in the occlusal plane could be used for
determining, changes in the molar
relationship relative to the occlusal
plane.

• Alterations of Wits appraisal applied to
the molar relationship and assuming an
identical alteration of the occlusal plane
(-10 degree), the anteroposterior molar
relationship is positively correlated with
the length of the distance A-B if the
upper molar moves on an arc( RA) with
the anterior point A, and the lower
molar on the arc (RB) with the center
point B.

• Starting from class I molar
relationship , the class II effect in
molar region is larger with the
greater distance A-B (Right) than
with the smaller distance A-B (left).

• The above assumptions are only
possible if the upper and lower
molars move on arc with the
centers A and B, respectively, as a
consequence of therapeutic
change in occlusal plane

• There is no scientific change for such
acceptation , nor is there justification
for suggesting that the distance from
points A to B in one individual is likely
to be 2.5 times greater than that of
another as shown in the illustration.

• Also, a 10 degree change in the
occlusal plane as a result of
treatment would cause the lower
incisor to be flared by the same
amount relative to this plane.

• The lower incisors were lingually
inclined at the beginning of
treatment because of instability, it
is unlikely that this would be the
effect of a treatment of choice.

Summary
• The wits appraisal is largely
dependent on correct location or
representation of the occlusal
plane. It can present a problem in
that the occlusal is not an actual
plane, and the left and right sides
do not coincide or superimpose
correctly.

• Due to possibility of supra/infra-
eruption of incisors a more
appropriate plane would be
functional occlusal plane drawn
through the occlusal overlap of the
maxillary first molars and first
bicuspids.

• The Wits appraisal is a linear
measurement and not analysis per
se. It is simply a diagnostic aid that
may prove useful in assessing the
extent of anteroposterior skeletal
dysplasia and in determining the
reliability of the ANB angle.

• This problem may be due to true
Dento-facial asymmetry,
asymmetric location of EAM, and
or incorrect location of head in
cephalostat.

• according to the “wits” reading is I mm in
males and 0 in females. In skeletal Class
II jaw dysplasia, point B0 would be
located well behind Point Ao (a Positive
reading) whereas in skeletal Class iii jaw
disharmony the “Wits” reading would be
negative namely, point B0 being forward
of point A0.

Thank You…

References
• AJODO- 1963
Volume 49.
• AJODO-2003
Volume 124, Number-5
• AJODO- 1975
Volume 67, Number-5
• European Jr of Orthodontics- 1982
Volume 4.

The Wits appraisal: A diagnostic aid for assessing sagittal jaw disharmony

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