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AN ANALYSIS OF VARIATION OF ANGLE ANB AND ITS
EVALUATION WITH WIT’S APPRAISAL IN SKELETAL CLASS II
MALOCCLUSION
Math Siddayya*, Deepak Kumar Suke†
ABSTRACT:
Objective: This study aimed to analyze the variation of angle ANB and its evaluation
with ‘Wits’ appraisal in skeletal class II malocclusion cases with angle ANB measuring
between 4 and 8 degrees.
Material and Methods: The present study was conducted on forty lateral cephalometric
radiographs of 40 subjects in the age group of 10 to 20 years, with skeletal class II
malocclusions. The angle SNA, SNB and angle ANB are measured for each case and
‘Wits’ appraisal is calculated by the horizontal distance between the perpendicular line
drawn on the occlusal plane from point A and B.
Result: Wits appraisal showed statistically very high significant correlation of variability
when compared to ANB. According to study there was a statistically significant core
relation between two parameters but r-value (coefficient of correlation) was less
compared to other studies. The ‘Wits’ appraisal shows high co-efficient of variability
when compared to ANB.
Conclusion: The high co-efficient variability of Wits’ appraisal signifies a dissimilar
apical base relation of maxilla and mandible in cases with similar ANB angle. Hence
‘Wits’ appraisal is a better indicator of sagittal jaw position when compared to ANB
angle.
AOSR 2013; 3(1): 23-30
Keywords: Malocclusion; Radiographs; Maxilla; Mandible
* Department of Dentistry, Bidar Institute of Medical Sciences and Research Institute,
Bidar.
† Department of Periodontics, Government College and Research Institute, Bangalore.
INTRODUCTION:
Since the introduction of angle ANB by
Riedel in 1952, it has become one of the
most popular means for evaluating the
cephalometric
evaluation
of
the
anteroposterior (AP) relationship of the
apical bases. The angle ANB is widely
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used
to
describe
the
skeletal
discrepancies between maxilla and
mandible. However its reliability as a
true indicator for sagittal jaw
relationship has been questioned. The
criticism has been based upon the fact
that naison is not a fixed point and any
change in its position would affect ANB.
Variation of angle ANB in class II malocclusion
The magnitude of angle may also be
affected by jaw rotations occuring
during growth and treatment.
In an attempt to eliminate the
inherent variations and problems
associated with relying on ANB,
jacobson suggested an alternative
method of assessing sagittal or AP jaw
relationship which is independent of
apical base relationship to cranial land
marks. JACOBSON and other several
authors have demonstrated use of
perpendiculars drawn from point A and
point B to the occlusal plane as an
alternative means to assess apical
discrepancies. This method has been
commonly referred to as 'Wits' appraisal.
At first the 'Wits' appraisal might appear
to be rather simple measurement.
However closer study shows it to be
complex measurement depending upon
the close interaction of sagittal and
vertical growth of maxilla and mandible
and the angulation of the occlusal plane.
The 'Wits' appraisal is a diagnostic aid
which enables the severity of degree of
anteroposterior jaw disharmony to be
measured from a lateral cephalometric
head film. Briefly, the method entails
drawing perpendiculars from points A
and B on the maxilla and mandible,
respectively, onto the occlusal plane.
The points of contact of the
perpendiculars onto the occlusal plane
are labeled AO and BO coincided,
whereas in males point BO was located
approximately 1mm ahead of point AO.
The 'Wits' reading in females having a
normal occlusion would thus be 0,
whereas in males it would be -1mm.
The ANB angle (the difference between
the SNA and SNB angles) is most
commonly used measurement in
appraising horizontal jaw disharmony.
The ANB reading, however, does not
take into consideration the relative
relationship of denture bases to cranial
reference planes. The singular advantage
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of the 'Wits' appraisal is that it
overcomes this shortcoming and
concomitantly emphasizes an awareness
of this relationship in the overall
interpretation of cephalometric analysis.
The 'Wits' appraisal is thought to be a
more reliable measure of anteroposterior
jaw relationship.
The purpose of present study is to
analyze ANB and its evaluation with
'Wits' appraisal in class II malocclusion
cases with angle ANB measuring
between 4 to 8 degrees.
MATERIALS AND METHODS:
The present study was conducted on
forty pretreatment lateral cephalometric
radiographs of 40 subjects of Bangalore
city in the age group of 10 to 20 years,
with skeletal class II malocclusions.
In this study forty pretreatment lateral
cephalometric radiographs of 20 males
subjects and 20 female subjects between
the ages of 10 years and 20 years were
selected on the basis of exhibiting class
II skeletal malocclusions with angle
ANB between 4 to 8 degrees. These
radiographs were selected at random
from out patient records of patient
residing in Bangalore who had reported
for orthodontic treatment at Govt Dental
College, Bangalore. No subject had
undergone any previous orthodontic
therapy. All the radiographs were taken
at the Department of Oral Medicine and
Radiology in a Trophy Radiology
Cephalometer using 85 KV and 10MA
and exposure time of 1.25 seconds on 15
inches was used. The subject was
positioned in the cephalometer with
Frankfurt horizontal plane parallel to the
ground. Each radiograph was traced on
acetate paper of 0.003 inch thickness
using a 0.3mm lead pencil. The
anteroposterior angular relationship of
the maxilla and to the mandible and
cranial base as described by ANB and
Math Siddayya et al.
the anteroposterior linear relationship of
the maxilla to mandible as described by
perpendicular lines from point A and B
on the functional occlusal plane.
The cephalometric points, planes and
angles used in this study.
 S-Sella: The midpoint in the
outline
of
Sella
Turcica
determined by inspection
 N-Nasion: The most anterior
point midway frontal and nasal
bone on the fronto nasal suture.
 A-Point A: Deepest point in
midline between the anterior
nasal spine and alveolar crest of
maxilla.
 B-Point B; The deepest point in
midline between the alveolar
crest of mandible and mental
process.
 Angle SNA
 Angle SNB
 Angle ANB
 AO: Perpendicular from point A
to occlusal plane.
 BO: Perpendicular from point B
to occlusal plane.
 Functional
Occlusal
Plane:
Occlusal plane drawn through the
intercuspation of molars and
premolars.
The angle SNA, SNB and angle ANB
are measured for each case and ‘Wits’
appraisal is calculated by the horizontal
distance between the perpendicular lines
drawn on the occlusal plane from point
A and B.
STATISTICAL ANALYSIS:
The measured values are tabulated and
subjected to statistical analysis. The
calculations were done separately for
male and female subjects of the sample.
Co efficient of variation and Co efficient
of
correlation
were
calculated.
Correlation of ANB with Wits was
calculated by Pearson’s correlation test.
Values were measured as Mean +
Standard deviation.
RESULTS
The mean SNA, SNB and ANB were
81,93,75,93 and 6 respectively. The
mean Wits appraisal was 3.13. The
standard deviation of ANB was 1.24 and
Wits was 1.65. There was a statistically
significant correlation between ANB and
Wits with r = 0.49. The Wits appraisal
showed statistically very high significant
correlation of variability (52.72) when
compared to the ANB (20.67).
Observed Values for Female Subjects
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Variation of angle ANB in class II malocclusion
Observed Values for Male Subjects
DISCUSSION:
The Angle ANB relates the anterior
apical bases of the maxillary and
mandibular dentition to the skeletal base.
Angles SNA, SNB and ANB were first
used by Downs and are still considered
popular criteria for distinguishing dentoskeletal problems from problems from
purely dental problems.
Nanda.R.S demonstrated that
changes in angle ANB could be a
resultant of differential amounts of
increase or decrease in angle SNA and
SNB which behave independently of one
another and are rather difficult to
predict.
Another variable that is believed
to influence the growth changes in angle
ANB is effect of growth changes in
angle S-N to the mandibular plane4 , as
well as closing or opening growth
rotation of the mandible. Studies by
Freeman, Taylor and Jacobson reiterate
that angle ANB is not a reliable basis for
identifying
unharmonious
jaw
relationships. Jacobson presented a
‘Wits’ appraisal based upon the
relationship of Point A and Point B
relative to the occlusal plane the
assumption was that this appraisal was
closest to the area of the dental and
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skeletal base relations and prone to less
variation when compared to angle ANB .
The ‘Wits’ appraisal is thus
intended not as a single diagnostic
criterion
but
as
an
additional
measurement which may be included in
existing cephalometric Analysis to aid in
the
assessment
of
degree
of
anteroposterior jaw disharmony. The
Wits appraisal thus provides a reliable
indication of extent or severity of
anterior posterior skeletal disharmony of
the jaws.
In this study, the average values for
SNA, SNB, ANB and Wits for the
combined values of both male and
female subjects are respectively. The
mean value for SNA is 81.93; SNB is
75.93, ANB is 6.00 and that of Wits is
3.13. Standard deviation for SNA and
Wits are 1.24 and 1.65 respectively. The
relationship between ANB and Wits
Karl Person’s correlation co-efficient (r)
was applied for combined values of both
male and female subjects. The reading is
40.49 which show that it is statistically
correlated.
The significant correlation coefficient among ANB angle and Wits
appraisal denotes that these parameters
are closely related to each other and may
be used inter changeably. The
Math Siddayya et al.
correlation co-efficient between the Wits
appraisal and ANB angle is lower in the
present study compared to that found by
other studies (Bishara ET AL , Jarvinen ,
Richardson ). Various authors have
considered the degree of correlation
between the Wits appraisal and skeletal
base indicators. Rotberg ET AL and
Bishara ET AL in particular have
investigated it correlation with angle
ANB. These appear general agreements.
In the present study there was
very high correlation of variability of
Wits appraisal when compared to the
angle ANB was noted , this supports the
investigations of the Oktay Bishara ET
AL in 1983 in their study showed a
significant correlation between the ANB
and Wits appraisal , but the r-values
were r relatively low (0.63) , but this is
little bit high when compared to the
study.
The age changes in angle ANB
and Wits appraisal was studied by
Bishara ET AL and noted a significant
age changes in angle ANB but there was
no changes in Wits appraisal.
In the present study the
cephalograms were selected considering
the angle ANB in the range of 4 – 8
degrees. Hence the coefficient of
variability was not significant but a large
co-efficient of variability of Wits
appraisal suggests a different apical base
relationships of maxilla and mandible,
eventhough angle ANB were similar,
hence our study supports the claim of
Bishara ET AL and others who claimed
that Wits appraisal is better indicator of
the saggital apical base relationship of
maxilla and mandible.
In
assessing
individual
malocclusion the variation between
ANB angle or the Wits measurement and
an average figure is of very little
practical importance. The information
required from cephalometric Analysis
relates to the nature and severity of
27
malocclusion and to what extent the
positions of teeth can be altered within
the limits dictated by the relationship of
the maxillary and mandibular dental
bases and whether such alterations can
be achieved by simple tipping movement
or whether more complex bodily
movement would be required.
The Wits appraisal is a linear
measurement and not an analysis per se.
it is simply an adjunctive diagnostic aid
which may prove useful in assessing the
extent of anteroposterior skeletal
displasia and in determining the
reliability of ANB angle.
CONCLUSION:
In this study 40 lateral cephalometric
radiographs of 20 male subjects and 20
female subjects selected randomly from
the out patient records in the department
of orthodontia were used. All the
subjects
had
class
II
skeletal
malocclusion with ANB measuring
between 4 and 8 degrees and their ages
ranged from 10 to 20 years. The
cephalograms were taken with standard
means.
Statistical calculations of mean,
standard deviation, co-efficient of
variability, co-efficient of correlation
were done.
The average values are worked
out for SNA, SNB, ANB and Wits for
the combined values of both male and
female subjects respectively. The mean
value for SNA is 81.93, SNB is 75.93,
ANB is 6.00 and that of Wits is 3.13.
Standard deviation for SNA and Wits are
1.24 and 1.65 respectively.
The relationship between ANB
and Wits Karl Person’s correlation coefficient (r) was applied for the
combined values of both male and
female subjects. The reading is +0.49,
which shows that, it is statistically
correlated.
Variation of angle ANB in class II malocclusion
According to the study there was a
statistically
significant
correlation
between the two parameters but r-value
was less compared to other studies.
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CORRESPONDENCE
Dr. Math Siddayya
Associate Professor
BRIMS, BIDAR
E-mail: [email protected]
Phone: +918147163381
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