Download Orthodontics: Overjet as a predictor of sagittal skeletal relationships

Orthodontics
Original Article
OVERJET AS A PREDICTOR OF SAGITTAL SKELETAL
RELATIONSHIPS
GHULAM RASOOL
2
NAYAB HASSAN
3
SUMMIYA BASHIR
4
ANEELA NAUSHEEN
5
UMAR HUSSAIN
1
ABSTRACT
Skeletal relationships in the sagittal plane do not always correspond with dental relationships. The
aim of the study was to evaluate the degree of correlation between a dental parameter (overjet) and a
skeletal (ANB) angle.
Eighty nine patients fulfilled the inclusion criteria for the study ( 22 males and 69 females, aged 1235). Overjet was measured on casts with a standard ruler. Lateral cephalograph was taken to measure
the ANB angle.
The correlation analysis of overjet with ANB angle in the three malocclusion classes showed, that
there was a weak correlation of overjet with ANB angle in all three groups of malocclusion with “r”
value of 0.257 whereas P value was statistical insignificance (P-value > 0.05).
This study concluded that overjet is not a good predictor for sagittal skeletal relationship and therefore could not be used for better assessment of sagittal jaw relation which is critical in orthodontic
diagnosis and treatment planning.
Key Words: Overjet, ANB angle, sagittal skeletal malocclusion.
INTRODUCTION
Correct orthodontic diagnosis requires history
of the patient, thorough examination and certain
diagnostic tools e.g model, radiographic analysis and
photographs.1-3 The aim of Clinical examination is to
establish the type and severity of malocclusion and to
determine the skeletal or dental origin of the problem.
It also helps to determine what diagnostic records might
be needed.3,4
OJ is an important linear parameter that can be
measured clinically and is used to assess the sagittal
relationship of upper and lower dental arches. OJ could
be due to skeletal, dental, or a combination of both.5
It is generally accepted that increased OJ is due to a
growth deficit of the lower jaw or increase of upper jaw
rather than poor positioning of the dental elements but
no significant data regarding this has been published
as yet.6
Ghulam Rasool, Professor and Principal Khyber College of Dentistry, Peshawar
2-5
Nayab Hassan, Summiya Bashir, Aneela Nausheen, Umar Hussain, Residents Orthodontics FCPS II
Email: [email protected]
Cell: 0321-9117048
Received for Publication:
June 29, 2016
Revised:
August 6, 2016
Accepted:
August 8, 2016
1
At completion of growth, when deciding on surgical
or orthodontic intervention, beside the facial profile,
OJ is also an important guideline. Generally when the
OJ is greater than 10 mm, surgery is a more successful
treatment option.5
Cephalometric analysis is an important part of
diagnosis in orthodontics, allowing changes associated
with growth and orthodontic treatment to be observed.
To diagnose and classify a malocclusion, the measured
values of cephalometric parameters are compared with
standard values. A large number of cephalometric standards have been developed for adult populations and
for children in the period of growth and development.7
For accurate measurement of sagittal skeletal relationship, the ANB angle and the Wits appraisal have
been considered as the most common cephalometric.5,8
ANB measurement is commonly used to determine
sagittal skeletal relationship in routine. It indicates
the magnitude of the skeletal jaw discrepancy and is,
in a normal well proportionate face, from 10 to 40.9
However ANB angle has certain limitations; with
change in the anteroposterior and vertical position of
nasion, increased or decreased vertical height of the
face10, tipping of SN plane ANB can give incorrect value
Pakistan Oral & Dental Journal Vol 36, No. 3 (July-September 2016)
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Overjet as a predictor of sagittal skeletal relationships
.There is variation in ANB angle between patient’s
centric occlusion and centric relation.11 Various authors
have shown that these angular measurements are geometrically sensitive and can give false measurement8,
soother linear measurement like witts and OJ should
be investigated for sagittal evaluation.
The rationale of this study was to determine whether
the sagittal skeletal evaluation through a non-invasive
parameter of OJ rather than through cephalometry
and to find out whether the previous study performed
is applicable in our population or not. If ANB could
coincide with the OJ; then this method could be considered as a substitution in cases where radiographic
facility is not available, patient not fit for radiation or
unaffordable.
METHODOLOGY
This cross-sectional study was carried out in the
orthodontic department of Khyber College of Dentistry.
Eighty nine patients were recruited, out of which 36
were males and 53 were females. Approval from the
Ethics Committee was sought and written consent were
taken from all the participants. The age range was 12 to
35 years. The inclusion criteria included subjects with
permanent dentition. Patients having any asymmetry
of jaws, absent or supernumerary teeth, previous extraction of any tooth or patients with past history of
orthodontic treatment were excluded from the study.
The molar relationship was assessed according
to the mesiobuccal cusp of the upper first permanent
molar.
• Class I: When the mesiobuccal cusp of permanent
upper first molar occluds in the mesio-buccal of the
permanent lower first molar.
• Class II: When the mesiobuccal cusp of permanent
upper first molar occluds mesial to the mesio-buccal
groove of the permanent lower first molar.
• Class III: When the mesiobuccal cusp of permanent
upper firstmolar occludes distal to the mesio-buccal
groove of the permanent lower first molar.
OJ was measured on the study casts with a standard
ruler as the horizontal overlap of the most prominent
incisor, with cast in occlusion distance from the labial
surface of lower central incisor to the incisal edge of
the most prominent upper central incisor was recorded.
The lateral cephalograms were taken under standard
conditions. The film – focus distance from the median
planeof the patient’s head was 150 cm, and the median plane – film distance 10 cm. The cephalograms
were taken with the subjects standing and the head
positioned in the cephalostat and orientated to the
Frankfort horizontal plane with the teeth in maximum
intercuspation. All measurements were made by the
same investigator. On cephalograph, the ANB angle
was measured by drawing two lines from nasion to
point A called as NA line and other line from nasion to
point B called as NB line. Angle formed between these
two lines was taken as ANB angle.
The data were analyzed using SPSS version 19.0.
Mean and standard deviation for numerical variable
likes OJand ANBwere calculated. Pearson correlation
test was used to relationships between OJ and ANB.
P < 0.05 was consideredto be significant.
RESULTS
A total of 83 subjects, 36 (40.4%) males and 53
(59.6%) females) were included in the study. Male
to female ratio was 1: 0.64. The most common age
group was second decade. (Table 1). There is very
low correlation between ANB and OJ (r =0.257) and
co-efficient of determination (r2= 0.066). Only 6.6%
skeletal cases of malocclusion OJ can be for ANB.
There is no statistically significant correlation between
ANB and OJ. (Table 2)
TABLE 1: AGE DISTRIBUTION
Age group (in years)
Frequency
Percentage
11-20
68
76.22
21-30
19
21.44
35
2
2.34
Total
89
100.0
TABLE 2: CORRELATIONAL ANALYSIS
BETWEEN ANB AND OJ
r*
r2
Std. Error of the Estimate
0.257
0.066
3.63775
*Pearson correlation test
TABLE3 : CORRELATION BETWEEN ANB AND OJ USING LINEAR REGRESSION EQUATION
Model
Sum of Squares
df
Mean Square
F
Sig.
81.493
1
81.493
6.158
0.015a
Residual
1151.288
87
13.233
Total
1232.781
88
Regression
a. Predictors: (Constant), ANB
b. Dependent Variable: OJ
Pakistan Oral & Dental Journal Vol 36, No. 3 (July-September 2016)
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Overjet as a predictor of sagittal skeletal relationships
TABLE 4: COMPARISON BETWEEN ANB AND OJ
Pair
Mean
N
Std. Deviation
Std. Error Mean
Overjet
4.0899
89
3.74284
.39674
ANB
4.5618
89
4.29840
.45563
a. Significant level = P<0.005
TABLE 5: PAIRED t TEST STATISTICS OF COMPARISON BETWEEN ANB AND OJ
Paired Differences
Mean
Std. Deviation
Std. Error
Mean
-.47191
4.92060
.52158
95% Confidence Interval
of the Difference
Lower
Upper
T
Df
Sig. (2 tailed)
-1.50845
.56462
-.905
88
.368
Table 3 shows the regression model of ANB and OJ
which is statistically significant; OJ is predictor of ANB
but correlation is very weak. Table 4 and 5 shows that
the difference between OJ and ANB is not statistically
significant (p=.640) which denotes similarity in ANB
and OJ.
DISCUSSION
Among the factors which must be evaluated to
formulate a correct diagnosis and a suitable treatment
plan, the antero-posterior relationship between the
maxilla and mandible is a particularly important parameter.12,13 Correction of sagittal discrepency is very
important in achieving balanced profile after orthodontic treatment. Various methods (ANB, Witts, OJ,
etc) used to measure the antero-posterior relationship
of maxilla to mandible.14-17
As proposed by the ABO (American Board of Orthodontist), OJ, in association with other parameters such
as overbite, IMPA, presence of open bite or crossbite, or
entity of crowding, is a useful indicator in evaluation
of the diagnostic complexity.18
The aim of this study was to evaluate by what
degree a dental parameter i.e OJ which is measured
clinically is able to predict the entity of the skeletal
parameter ANB. Therefore, within individual classes
of malocclusion, according to Angle’s classification, the
average values of these parameters were calculated and
their correlations tested the extent to which OJ can
determine skeletal relationships in the sagittal plane.
OJ is an important measurement in cast analysis. It
has been one of the parameters used to investigate
the sagittal relationship of the upper and lower dental
arch. The cause of an increased or negative OJ could be
skeletal, dental, or a combination of both. At completion
of growth, when deciding on orthodontic or surgical
intervention, in addition to the facial profile, OJ is an
important guideline. Generally when the OJ is greater
than 10mm, surgery is a more indicated treatment.2,5
The current study, showed that there was weak
correlation between OJ and ANB with r=0.257. This
was probably due to the fact that OJ is influenced by
the inclination of the upper and lower incisors, while
ANB is less affected. However, ANB also varies according to the anteroposterior position of the nasion,
the inclination of the SN plane, and the inclination of
the jaws.19 Another factor able to modify the width of
ANB, even if the relationship between the jaws remains
constant, is the inclination of the Occlusal plane.20
In a previously conducted study by Iwasaki et al21
similar results as in current study were observed. They
found that OJ is not always a reliable measure of the
jaw relationship in the sagittal plane, especially in
subjects with Class III malocclusions Another study
carried out by Zupancic et al5 showed the same results.
This study findings demonstrated that for Class I and
Class III malocclusions OJ is not a good predictor of
skeletal relationships in the sagittal plane. However,
according to their study, in Class II division 1 malocclusion subjects, OJ is a statistically significant predictor.5
Similar results were found in a study by Jabbar et al3
they observed weak correlation between OJ and ANB
angle in all three malocclusion groups but found that it
is statistically significant only in class III malocclusion.3
CONCLUSION
The findings of this study demonstrate that OJ is
not a good predictor of malocclusion (Class I, Class II
& Class III) for skeletal relationships in the sagittal
plane.
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Overjet as a predictor of sagittal skeletal relationships
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CONTRIBUTIONS BY AUTHORS
1 Ghulam Rasool:
2 Nayab Hassan:
3 Summiya Bashir:
Supervision and proof reading
Paper writing
Topic selection
4 Aneela Nausheen:
5 Umar Hussain:
Data collection
Data analysis
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398