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Orthodontics
137
October 2014
Symphyseal Angle: an
Angle to Determine
Skeletal Pattern using
Panoramic Radiographs
Abstract: The aim of this article is to derive an angle using panoramic radiographs which is as reliable as lateral cephalometric norms in
determining the skeletal growth pattern. The sample size consisted of 60 OPGs of patients with normodivergent growth pattern evaluated
from cephalometric radiographs. The mean Symphyseal Angle (SA) obtained was 134.1 ± 2.1 and correlation tests showed high, negative
and statistically significant correlation for both Basal Plane Angle (BPA)1 and Frankfurt Mandibular Plane Angle (FMA) (p = 0.0063) and
a positive correlation was shown with the Jarabak Ratio (JR)2 (p = 0.032). The Symphyseal Angle derived was helpful in determining the
skeletal pattern of the craniofacial structure.
Clinical Relevance: This paper demonstrates the use of the Symphyseal Angle to determine skeletal growth pattern using panoramic radiographs.
Ortho Update 2014; 7: 137–139
Shreya N Ajmera, BDS, MDS, 3/7, Marwadi Galli, Osmanabad, Maharashtra 413501, Shivanand Venkatesh, BDS, MDS, MOrth RCS(Edinb),
Assistant Professor, Department of Orthodontics and Dentofacial Orthopedics, MS Ramaiah Dental College and Hospital, MSR Nagar,
Bangalore, Karnataka 560054, Sanjay V Ganeshkar, BDS, MDS, MDO RCPS(Glasg), Diplomate Indian Board of Orthodontics, Professor,
Department of Orthodontics and Dentofacial Orthopedics, Sangamesh B, BDS, MDS, MOrth RCS(Edinb), Reader, Department of
Orthodontics and Dentofacial Orthopedics and Anand K Patil, BDS, MDS, MOrth RCS(Edinb), Professor and Head, Department of
Orthodontics and Dentofacial Orthopedics, SDM College of Dental Sciences, Sattur, Dharwad, Karnataka 580009, India.
Panoramic radiography was first introduced
by Yrjo Paatero of the University of
Helsinki in 1961 and demonstrated the
right and left anatomic landmarks for
bilateral structures in a panoramic view.3
Orthodontic practice utilizes panoramic
radiography for information on the teeth,
their axial inclinations, maturation periods
and surrounding tissues and is considered
to be an indispensable orthodontic
screening tool.4,5,6 Facial and mandibular
asymmetries, bilateral condylar symmetry,
bone trabecular pattern and alveolar
support to the teeth are of major concern
to orthodontists. Similarly, the growth
pattern or the divergence of the jaw bases
has to be determined in a patient to help
Shreya N Ajmera
decide on the type of mechanics to be
employed.
The gonial angle measured
from the lateral cephalogram is one of the
most common methods of determining
jaw divergence. However, the gonial angle
has to be validated with other parameters
because of its poor reliability as it measures
the arithmetic mean of right and left
angles.7 Recent studies have concluded that
panoramic radiographs can also be used to
determine the gonial angle as accurately as
lateral cephalograms.8,9
One of the first attempts
to determine skeletal pattern using
panoramic radiographs was undertaken
by Levandoski10 and since then very few
studies have demonstrated the use of
panoramic radiographs to determine
growth pattern. The aim of the present
study is to determine a more reliable angle
that could be used as an adjunct to lateral
cephalometric measurements to determine
the growth pattern of the individual using
panoramic radiographs.
Materials and methods
Sixty panoramic radiographs
(33 females and 27 males, age range of
14−25 years) were obtained from patients
undergoing orthodontic treatment in
the SDM College of Dental Sciences,
Karnataka, India. All the patients had a
Shivanand Venkatesh, Sanjay V Ganeshkar, Sangamesh B and Anand K Patil
138
Orthodontics October 2014
normodivergent growth pattern which was
determined using the lateral cephalograms
from the following cephalometric criteria:
Frankfurt Mandibular Plane Angle (FMA) of
25 ± 2°, Jarabak Ratio (JR)2 of 62−65%, and
Basal Plane Angle (BPA)1 of 25 ± 2° (Figure
1). Panoramic and lateral cephalometric
radiographs were obtained using a KODAK
9000 machine with the patients in the
Natural Head Position. Radiographs of
patients with asymmetry, bone disorders,
cyst and tumours were excluded from
the study and good quality OPGs with
recognizable landmarks were used.
The radiographs were traced
on a sheet of cellulose acetate paper using
a 0.3 mm Staedtler Mars micro pencil.
Landmarks on the panoramic radiographs
were identified and marked. The use of
a bite plate while taking the radiograph
altered the relationship between the
maxilla and mandible, leading to errors in
the measurements obtained involving both
the jaws. Therefore, independent reference
planes were drawn on the mandibular
panoramic images to ensure reliability
of the measurements even with the use
of a bite plate. A new angle called the
Symphyseal Angle (SA) was defined and
constructed based on these reference
angles.
The SA was constructed
from two tangents drawn at the
most prominent point on the inferior
border of the mandible in the canine
and premolar regions, meeting at the
midsagittal plane, drawn passing through
the anterior nasal spine and between
the two central incisors (Figure 2). To
derive the midsagittal plane, a grid of 1
cm square was constructed and placed
on the radiograph. All the radiographs
were traced in this way and the SA was
measured. To reduce the intra-operator
errors, all the measurements were
repeated after one week.
Statistical analysis
All the parameters were
measured by the same examiner
and repeated after one week. Hence
repeatability coefficients were calculated
for the initial and final measurements
to eliminate intra-observer error. The
mean values and the standard deviation
of the parameters were calculated for
both panoramic radiographs and lateral
cephalograms. The correlations between
the mean values of the panoramic
measurement and their cephalometric
correspondents were obtained.
Regression equations were set for the
significant correlations. Thus it was
possible to calculate the significance level
and the predictability of the information
from the panoramic radiographs.
Results
The repeatability coefficients
were above 0.99 for all the parameters
measured, confirming the reliability of the
measurements. The mean Symphyseal
Angle obtained from panoramic
radiographs was 134.1° with a standard
deviation of 2.11° (Table 1).
To summarize the results
shown in Table 2:
A highly significant negative correlation
was seen between FMA and SA (r = -0.41,
p = 0.0063), suggesting any increase in
FMA resulted in a decrease in SA.
A significant positive correlation was
seen with the JR2 and SA (r = 0.325, p =
0.033), whereas a noteworthy negative
correlation was observed with BPA1 and
SA (r = -0.30, p = 0.04).
Hence there was a significant
correlation between the Symphyseal
Angle and all the three parameters.
Discussion
Panoramic radiographs have
been used extensively to determine
presence or absence of teeth, their root
positions, bone architecture, relevant
pathology and to determine the teeth
eruption status. Recent studies have
suggested that panoramic radiographs
can be used as an adjunct to determine
the growth pattern along with lateral
cephalometric radiographs. These articles
focus on measurement of the gonial angle
since there is a possibility of error in the
measurement of this angle using lateral
cephalometric radiographs. Larheim
and Svanaes stated that both panoramic
radiographs and lateral cephalograms
were accurate in determining the gonial
angle and found no significant difference
between the right and left sides in
panoramic radiography.8
Fisher-Brandies et al indicated
that the gonial angle obtained by
panoramic radiography was 2.2−3.6°
less than that obtained from a lateral
cephalogram.11 Türp et al stated that
vertical linear measurements on the
condyle and the ramus are not reliable for
patients with macerated skulls.12 On the
contrary, Larheim and Svanaes emphasized
that horizontal measurements obtained
from OPG were unreliable. Therefore, only
angular measurements were made on the
panoramic radiographs.8 The horizontal
distances are particularly unreliable as a
result of the non-linear variation in the
magnification at different object depths,
whereas vertical distances are relatively
reliable.13,14,15 However, other authors have
found that the reproducibility of vertical
and angular measurements is acceptable
provided that the patient’s head is correctly
positioned in the equipment.16 Since there
is a disparity in the reliability of gonial
angle measurements obtained from a
panoramic radiograph, an alternative to the
gonial angle was determined.
This study was devised to derive
an angle which is reliable and accurate
in determining the growth pattern of an
individual using panoramic radiographs. In
order to derive an angle, a study population
with normodivergent growth pattern (FMA
of 25 ± 2, JR2 of 62−65%, BPA1 of 25 ± 2,)
was selected. This would enable a check to
be made for any deviation from the norms
for hypo/hyperdivergent growth patterns.
The pantomographs were taken in the
Natural Head Position in order to eliminate
distortion or magnification errors and also
to eliminate any effect rotation of the skull
would have on the Symphyseal Angle.
Grids were placed on the
Figure 1. Cephalometric tracing showing various
planes used to measure the parameters: FHP −
Frankfurt Horizontal Plane; PP − Palatal Plane;
MP − Mandibular Plane; AFH − Anterior Facial
Height; PFH − Posterior Facial Height.
Figure 2. Reference planes and the angles
measured on panoramic radiographs: SA −
Symphyseal Angle.
SA
Orthodontics
139
October 2014
distortion in lateral head films: a methodologic
study. Am J Orthod 1977; 71(5): 554−564.
8. Larheim TA, Svanaes DB, Johannessen S.
Reproducibility of radiographs with the
Orthopantomograph 5: tooth length
assessment. Oral Surg Oral Med Oral Pathol
Oral Radiol Endod 1984; 58: 736−741.
9. Shahabi M, Ramazanzadeh BA. Comparison
between the external gonial angle in
panoramic radiographs and lateral
cephalograms of adult patients with Class I
malocclusion. J Oral Sci 2009; 51(3): 425−429.
10. Piedra I. The Levandoski Panoramic Analysis in
the diagnosis of facial and dental asymmetries.
J Clin Pediatr Dent 1995; 20: 15–21.
11. Fisher-Brandies H, Fischer-Brandies E, Dielert E.
The mandibular angle in the orthopantomogram.
Radiologe 1984; 24: 547−549.
12. Türp JC, Vach W, Harbich K, Alt KW, Strub
JR. Determining mandibular condyle
and ramus height with the help of an
orthopantomogram − a valid method? J Oral
Rehabil 1996; 23: 395−400.
13. Ohm E, Silness J. Size of the mandibular jaw
angle related to age, tooth retention and
gender. J Oral Rehabil 1999; 26: 883−891.
14. Tronje G, Welander U, McDavid WD, Morris
CR. Image distortion in rotational panoramic
radiography. Acta Radiol Diagn (Stockh) 1981;
22(3A): 295−299.
15. Zach GA, Langland OE, Sippy FH. The use
of the orthopantomogram in longitudinal
studies. Angle Orthod 1969; 39: 42−50.
16. Larheim TA, Svanaes DB. Reproducibility of
rotational panoramic radiography: mandibular
linear dimensions and angles. Am J Orthod
Dentofacial Orthop 1986; 90: 45−51.
panoramic radiograph to determine the
midsagittal plane, as well as to determine
maximum curvature on the lower border
of the mandible in the symphysis and
the parasymphysis region in order to
facilitate drawing of the tangent on the
lower border. The maximum difference was
found on the lower border in the canine
and premolar areas. Tangents were drawn
both on the right and left side at the most
prominent point. As the patients with
condylar asymmetries were eliminated in
the study, both the tangents intersected
at the midsagittal plane. The angle formed
by the tangents was measured at the point
of intersection on the midsagittal plane
and was named the Symphyseal Angle.
The mean SA obtained was 134.1 ± 2.1; for
females it was 133.5 ± 3.9 and in males it
was 135.1 ± 1.5. This is supported by gender
variation obtained in the gonial angle
measurement in the study done by Ohm
who claimed gender had some effect on the
size of the gonial angle.13 The correlation
analysis depicted strong negative
significant correlation between the SA and
the FMA, together with a less significant,
but negative, correlation with the BPA.1
Depending upon the
significance values, the Symphyseal
Angle can be considered as an adjunct
to lateral cephalograms to determine the
growth pattern of the patient. This study
was done using panoramic radiographs
which showed no mandibular asymmetry,
therefore clinicians should be aware of this
fact while evaluating radiographs.
Conclusions
The Symphyseal Angle of 134.1 ± 2.1°
indicates a normodivergent growth pattern
of an individual as accurately as using
lateral cephalometric parameters such
as the Frankfurt Mandibular Plane Angle,
Jarabak Ratio2 and Basal Plane Angle.1
With standard exposure conditions and
high image quality, panoramic radiographs
can provide information that is accurate
and reliable when compared to lateral
cephalograms in assessing divergent
growth pattern.
References
1. Rakosi T. An Atlas and Manual of Cephalometric
Radiology. London: Mosby (Wolfe Medical
Atlases), 1982: pp113−116.
2. Jarabak JR, Fizzell JA. Technique and Treatment
with Light-wire Edgewise Appliance. St Louis: CV
Mosby, 1972.
3. Hazan H, M olina V, Schendel SA. Reliability of
panoramic radiographs for the assessment
of mandibular elongation after distraction
osteogenesis procedures. Orthod Craniofac Res
2011; 14: 25−32.
4. Akcam MO, Altiok T, Ozdiler E. Panoramic
radiographs: a tool for investigating skeletal
pattern. Am J Orthod Dentofacial Orthop 2003;
123: 175−181.
5. Friedland B. Clinical radiological issues in
orthodontic practice. Semin Orthod 1998; 4: 64−78.
6. Graber TM, Brainerd FS. Current Orthodontic
Concepts and Techniques. Philadelphia: WB
Saunders, 1985: pp45−46.
7. Slagsvold O, Pedersen K. Gonial angle
Standard Confid Confid
Parameters Mean SD Error Median -95.000% +95.000% Minimum Maximum
SA 134.38 2.11 0.46 135.00 133.42 135.34 131.00 138.00
FMA 25.40 1.14 0.25 25.00 24.89 25.92 23.00 27.00
JR 63.30 1.23 0.27 63.40 62.74 63.85 61.00 65.50
BPA 24.90 1.23 0.27 25.00 24.34 25.47 23.00 27.00
Table 1. Descriptive statistics of the panoramic and cephalometric measurements. Key: SA − Symphyseal Angle; FMA − Frankfurt Mandibular Plane
Angle; JR − Jarabak Ratio; BPA − Basal Plane Angle.
LC parameters r-value R2 t-value P-value Reg equation
FMA -0.4103 0.1684 -2.8813 0.0063 SA = 150.33-0.63
JR 0.3255 0.1060 2.2046 0.0332 SA = 102.50+50 JR
BPA -0.3066 0.0940 -2.0622 0.0456 SA = 146.37-48 BPA
Table 2. Correlation analysis of Symphyseal Angle with various lateral cephalometric measurements. Key: LC parameters − Lateral cephalometric parameters,
p < 0.05; SA − Symphyseal Angle; FMA − Frankfurt Mandibular Plane Angle; JR − Jarabak Ratio; BPA − Basal Plane Angle.
