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Year : 2023  |  Volume : 12  |  Issue : 1  |  Page : 57

Photographic Frankfort plane subnasale pogonion (FSA) angle for assessment of anteroposterior discrepancies in malocclusion subjects: A prospective study

1 Department of Orthodontics and Dentofacial Orthopaedics, Saveetha Dental College, Chennai, Tamil Nadu, India
2 Department of Public Health Dentistry, Saveetha Dental College, Chennai, Tamil Nadu, India

Date of Submission12-Jan-2023
Date of Decision23-Apr-2023
Date of Acceptance25-May-2023
Date of Web Publication04-Sep-2023

Correspondence Address:
Ravindra Kumar Jain
162, Saveetha Dental College, Poonamallee High Road, Velappanchavadi, Chennai - 77, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jos.jos_7_23

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INTRODUCTION: Anterior-posterior discrepancy assessment is a crucial component of orthodontic diagnosis and is often carried out using hard tissue cephalometric analysis. The purpose of this study was to compare the photographic Frankfort plane subnasale pogonion (FSA) angle with established cephalometric parameters to determine the accuracy of the angle in determining maxillomandibular anteroposterior discrepancies.
MATERIALS AND METHODS: In this prospective study, a total of 60 subjects, 20 in each skeletal sagittal malocclusion, were included in the final sample based on the selection criteria. Both photographic and cephalometric records were taken, and the parameters assessed were the beta angle, Steiner's analysis, the ANB (A point- Nasion- B point) angle in the cephalograms, and the FSA angle in the profile photographs. Statistical analysis was done with SPSS software. The correlation between the measured parameters was assessed using Pearson's correlation test.
RESULTS: A high positive and significant correlation between the FSA angle and beta angle (r = 0.793) was noted, and a high negative and significant correlation between the FSA angle and ANB angle (r = -0.848) was noted.
CONCLUSION: The photographic FSA angle can be used as a reliable parameter to diagnose anteroposterior discrepancies.

Keywords: Anteroposterior relation, malocclusion, orthodontics, photographic study, soft tissue

How to cite this article:
Rebekah R, Jain RK, Balasubramaniam A, Sreenivasagan S. Photographic Frankfort plane subnasale pogonion (FSA) angle for assessment of anteroposterior discrepancies in malocclusion subjects: A prospective study. J Orthodont Sci 2023;12:57

How to cite this URL:
Rebekah R, Jain RK, Balasubramaniam A, Sreenivasagan S. Photographic Frankfort plane subnasale pogonion (FSA) angle for assessment of anteroposterior discrepancies in malocclusion subjects: A prospective study. J Orthodont Sci [serial online] 2023 [cited 2023 Oct 3];12:57. Available from: https://www.jorthodsci.org/text.asp?2023/12/1/57/385077

  Introduction Top

The goal of any orthodontic treatment is to bring about the best dental as well as facial outcomes, as patients are majorly concerned about esthetics and function.[1] Anteroposterior jaw discrepancies include deviations between maxillary and the mandibular dentition or skeletal bases in the sagittal plane and can be assessed with cephalometric criteria like the Wits Appraisal, ANB angle, beta angle, and Nasion perpendicular, or using photographs.[2] Soft-tissue evaluation is indispensable in orthodontic diagnosis and treatment evaluation as the skeletal morphology is influenced by soft-tissue function and adaptation.[3]

During a patient's clinical evaluation, the face's profile and convexity can give an estimate of the sagittal jaw relationship. Previous research on using profile photographs for analyzing soft tissues in different malocclusions has reported a moderate correlation between the soft tissue and underlying skeletal structures.[4] Sushner et al.[5] measured the soft-tissue profile using a line drawn from the soft-tissue nasion to the soft-tissue pogonion. Another study by Sowmithra devi S et al. compared and evaluated the anteroposterior relationship of the maxillary central incisors to the forehead using facial profile pictures.[6]

A new soft-tissue angle called the Frankfort plane subnasale pogonion (FSA) angle was reported by Sreenivasagan et al.[7] for the assessment of anteroposterior discrepancies in cephalograms. The FSA angle is the angle formed by the subnasal soft-tissue pogonion plane (SA plane) and the Frankfort horizontal plane, which is used to calculate anteroposterior jaw relations.[7] In the present study, an effort was made to determine the FSA plane in photographs and correlate it with other anteroposterior discrepancy parameters on cephalograms. As photographs can be taken more readily than lateral cephalograms, profile improvement during treatment will be more easily discernible. The purpose of this study was to determine the maxillomandibular anteroposterior discrepancies by correlating the photographic FSA angle with cephalometric sagittal skeletal angles.

  Materials and Methods Top

Study population

This prospective study was done on patients who had reported to the Department of Orthodontics and Dentofacial Orthopaedics at Saveetha Dental College from June 2022 to September 2022 for orthodontic treatment. This prospective study was approved by the Institutional Review Board of Saveetha University (Ethical clearance number: IHEC/SDC/ORTHO-2101/21/654).

Based on the initial clinical examination, 200 subjects with different sagittal malocclusions were selected. The sample size was determined using the G*Power software (version 3.12, Heinrich Heine University, Düsseldorf). The study by Sreenivasagan et al.[7] was used as a reference for sample size calculation. The estimated sample size was 42, but the total sample was expanded to 60 subjects to obtain an equivalent sample in each of the three groups. The alpha level and power were set at 0.05 and 80%, respectively.

Radiographic and photographic records of all 200 subjects were taken, and based on the selection criteria, a total of 60 subjects, 20 in each skeletal sagittal malocclusion, were included in the final sample based on the ANB angle (class I if the angle was 2°-4°, class II if the angle was > 4°, and class III if the angle was 2°). Adult subjects aged 18 and 25 years with no congenital anomalies, missing teeth, or a history of previous orthodontic treatment requiring malocclusion correction were chosen. The demographic details have been tabulated in [Table 1]. [r1]
Table 1: Demographic data of the study subjects

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Photographic procedure

The photographic method described by Mehta et al.[8] was used for the photographic set-up, and the subjects' profile view was taken as part of the photographic record. The images were captured with a Canon EOS 1300D DSLR camera with a 100 mm macro lens mounted on a tripod. The camera was operated manually with the following settings: 1/125 sec. shutter speed, ISO 100, f/14, and 1:1 magnification. All photos were taken with the lips relaxed and the head in natural head posture (NHP). The subjects were told to tilt their heads up and down in front of a mirror until they felt comfortable doing so to find their NHP. Adhesive tape was used to identify the porion and orbitale, which were located on the superior and inferior margins of the orbit, respectively. A 30-cm steel ruler was attached to the wall vertically, and the patients were made to stand in front of the wall in a natural head position, looking at their eye level. With the adhesive marking in place and the ruler set up in the background, each patient's profile was photographed.

The photographs were later transferred to the computer, and cropping was done with a ratio of 3:2 using Adobe Photoshop software (version 2020, macOS 11.0). Later, FACAD digital orthodontic tracing software was used to trace the photographs (ILEXIS, Sweden, version 3.12). The ruler was used to calibrate the pictures in relation to actual measurements (1:1). The subnasale, soft-tissue pogonion, the superior margin of the external auditory meatus, inferior margin of the orbit, and the soft-tissue pogonion were identified on the photographs. The SA plane and FH plane were drawn by joining the respective points on the photographs. The FSA angle was determined for all samples as given in [Figure 1] in the respective groups, and the mean and standard deviation (SD) were determined.
Figure 1: Photographic FSA angle measurement in FACAD digital software

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Radiographic procedure

A cephalostat (Carestream CS9600) was used to take the lateral cephalometric radiographs under standard operating procedures with exposure values of 78 kV, 0 mA, and 0.6 seconds. With the patient in NHP, it was taken with the lips at rest and the teeth at maximal intercuspation. The lateral cephalometric digital images were then incorporated into the Facad software (version 3.12, Sweden). The factors evaluated included the beta angle, Steiner's analysis, and ANB angle, as shown in [Figure 2].
Figure 2: Cephalometric measurements of the ANB angle and the beta angle in FACAD digital software

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Statistical analysis

SPSS software (version 23.0) was used for performing the statistical tests. The descriptive statistics of the measured parameters were performed along with Pearson's correlation tests. The correlation coefficient was also derived for FSA with beta and ANB angles for individual groups, and the results were tabulated.

  Results Top

The statistical tests were performed using the SPSS software (version 23.0). The subjects involved in the study were categorized based on the type of malocclusion, and the descriptive data have been presented in [Table 1]. The descriptive statistics were performed and the mean and SD of the FSA angle, beta angle, and ANB angle were calculated and tabulated as given in [Table 2]. The data were tested for normality using the Shapiro-Wilk test and the data were found to be normally distributed.
Table 2: Descriptive statistics of the measured parameters

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[Table 2] gives the mean and SD of the FSA angle, ANB angle, and beta angle for all groups included in the study for the intergroup comparisons. The correlation of the FSA angle with other angles (beta and ANB angle) in all three groups was determined with Pearson's correlation test and tabulated [Table 3]. There was a statistically significant difference in the correlation between the angular cephalometric and photographic parameters (P = .00) [r3]. A high positive correlation between the FSA angle and beta angle (r = 0.793) and a high negative correlation between the FSA angle and ANB angle (r = -0.848) were noted. The correlation of all the parameters is graphically represented in a Scatter plot matrix graph, as shown in [Figure 3].
Table 3: Pearson's correlation test values

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Figure 3: Scatter plot matrix graph

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The correlation coefficient was also assessed individually in all study groups using Pearson's correlation test. There was a negative correlation between ANB and beta angle which was found to be statistically significant in Class III malocclusion subjects as mentioned in [Table 4]. However, the correlation of photographic FSA angle with ANB angle and beta angle among various skeletal malocclusion groups (skeletal class I, II, and III) was not statistically significant as mentioned in [Table 4].
Table 4: Correlation between the parameters in the skeletal class I, class II, and class III groups individually

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  Discussion Top

Photographs are routinely used as diagnostic aids in an orthodontic setting and can be used to assess the patient's profile. Profile assessment on photographs can be a good alternative to cephalograms, as the latter involves radiation exposure and cannot be routinely carried out. In the present study, an effort was made to study the correlation of the FSA angle introduced by Sreenivasagan et al.[7] on photographs with cephalometric sagittal skeletal angles for determining maxillomandibular anteroposterior discrepancies. Subjects with three different sagittal skeletal malocclusions as assessed by the cephalometric ANB angle were included in this study and correlation assessment of the FSA angle with the ANB and beta angle was performed. A statistically significant association between photographic FSA and cephalometric ANB and beta angles was found (P = .00). The FSA angle showed a high positive correlation with the beta angle (0.793) and a high negative correlation with the ANB angle (-0.848).

Various cephalometric angles are used routinely for anteroposterior assessment in malocclusion patients.[9],[10],[11] Among such parameters, the ANB and beta angles were determined to be the most accurate indicators for assessing the anteroposterior jaw relationship.[12],[13],[14] However, some studies reported that these parameters were insufficient.

Taylor's study emphasized that the ANB angle did not always represent a real apical base connection and that alterations could occur as a result of various horizontal disparities between points A and B as well as changes in the vertical distance from the nasion.[15] Because of differences in points A and B and the condyle's axis of rotation (point C), beta-angle values are also susceptible to variation.[13]

Reidel et al.[16] stated that the soft-tissue profile and the underlying skeletal profile of the patient were closely related. All soft-tissue alterations during growth were discovered to be comparable to equivalent skeletal alterations in a study by Mauchamp et al.[17] Barnett et al.[18] [r4] investigated the relationship between the skeletal and soft-tissue profiles on lateral cephalograms. They found a strong correlation between the skeletal and corresponding soft tissue A and B points, suggesting that soft-tissue assessment can foretell the underlying skeletal relationships. Soft-tissue adaptation following orthodontic treatment has been assessed previously, and it has been found that proportionate changes present between skeletal points and their overlying soft-tissue points.[19] The current soft-tissue paradigm shift in orthodontic treatment planning imparts more importance to soft-tissue position, which can be easily assessed with photographs. Comparing cephalometric angles to photographic measurements in the past has revealed that the latter is more reliable and consistent.[20] Sagittal discrepancy and the position of the lips were discovered to have an impact on the patient's facial esthetics when Yu et al.[21] evaluated the link between cephalometric measurements and facial attractiveness after the conclusion of orthodontic therapy.

Sreenivasagan et al.[7] introduced the FSA angle as a new soft-tissue angle to differentiate the anteroposterior relationship using cephalometric evaluation. The technique by Mehta et al.[8] was employed in the present study for taking photographs which has been proven to be repeatable and reproducible. The results of the present study depict a high positive and significant correlation between the FSA angle and the beta angle and a high negative correlation between the FSA angle and ANB angle. This is in accordance with the results of a previous study by Mehta et al.[8] where cephalometric and photographic variables were compared and they had a high positive correlation (r > 0.5) between them. Thus, the photographic FSA angle could be used as a reliable diagnostic tool in determining anteroposterior discrepancies in malocclusion subjects.


In this study, subjects belonging to different ethnicities were not involved, although the sample size was calculated, more subjects could be involved to derive more evidence. Factors affecting soft-tissue thickness like gender, and growth patterns were not considered, which can affect the results of the present study.[17]

  Conclusion Top

Photographs can be used as a diagnostic tool in determining anteroposterior skeletal relationships. The photographic FSA correlated well with the previously established cephalometric angles and hence can be routinely used for determining maxillomandibular anteroposterior discrepancies in all types of sagittal skeletal malocclusions [r5].

Ethics approval

The study was approved by the Institutional Review Board of Saveetha University (Ethical clearance number: IHEC/SDC/ORTHO-2101/21/654).

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Ackerman JL, Proffit WR, Sarver DM. The emerging soft tissue paradigm in orthodontic diagnosis and treatment planning. Clin Orthod Res 1999;2:49–52.  Back to cited text no. 1
Davis GS Jr, Cannon JL, Messersmith ML. Determining the sagittal relationship between the maxilla and the mandible: A cephalometric analysis to clear up the confusion. J Tenn Dent Assoc 2013;93:22–8.  Back to cited text no. 2
Worms FW, Isaacson RJ, Speidel TM. Surgical orthodontic treatment planning: Profile analysis and mandibular surgery. Angle Orthod 1976;46:1–25.  Back to cited text no. 3
A longitudinal study of soft tissue facial structures and their profile characteristics, defined in relation to underlying skeletal structures. Am J Orthod 1959;45:481–507.  Back to cited text no. 4
Sushner NI. A photographic study of the soft-tissue profile of the Negro population. Am J Orthod 1977;72:373–85.  Back to cited text no. 5
Andrews WA. AP relationship of the maxillary central incisors to the forehead in adult white females. Angle Orthod 2008;78:662–9.  Back to cited text no. 6
Sreenivasagan S, Sivakumar A. FSA angle: A soft tissue approach for assessing sagittal skeletal discrepancy. Int J Clin Pediatr Dent 2021;14(Suppl 1):S54–6.  Back to cited text no. 7
Mehta P, Sagarkar RM, Mathew S. Photographic assessment of cephalometric measurements in skeletal class II cases: A Comparative Study. J Clin Diagn Res 2017;11:ZC60–4.  Back to cited text no. 8
Freeman RS. Adjusting A-N-B angles to reflect the effect of maxillary position. Angle Orthod 1981;51:162–71.  Back to cited text no. 9
Jacobson A. The “Wits” appraisal of jaw disharmony. Am J Orthod 1975;67:125–38.  Back to cited text no. 10
Baik CY, Ververidou M. A new approach of assessing sagittal discrepancies: The Beta angle. Am J Orthod Dentofacial Orthop 2004;126:100–5.  Back to cited text no. 11
Katti CG, Mohan A, Abhi A. Predictability of ANB, Beta, and YEN angles as anteroposterior dysplasia indicators in Gulbarga population. J Indian Orthod Soc 2020; 54:321–4.  Back to cited text no. 12
Singh G, Verma S, Singh DP, Yadav SK, Yadav AB. Correlation of Beta angle with antero-posterior dysplasia indicators and FMA: An institution based cephalometric study. J Clin Diagn Res 2016;10:ZC75–8.  Back to cited text no. 13
Ahmed M, Shaikh A, Fida M. Diagnostic validity of different cephalometric analyses for assessment of the sagittal skeletal pattern. Dental Press J Orthod 2018;23:75–81.  Back to cited text no. 14
Taylor CM. Changes in the relationship of nasion, point A, and point B and the effect upon ANB. Am J Orthod 1969;56:143–63.  Back to cited text no. 15
Riedel RA. An analysis of dentofacial relationships. Am J Orthod 1957;43:103–19.  Back to cited text no. 16
Mauchamp O, Sassouni V. Growth and prediction of the skeletal and soft-tissue profiles. Am J Orthod 1973;64:83–94.  Back to cited text no. 17
Barnett DP. Variations in the soft tissue profile and their relevance to the clinical assessment of skeletal pattern. Br J Orthod 1975;2:235–8.  Back to cited text no. 18
Sharma JN. Skeletal and soft tissue point A and B changes following orthodontic treatment of Nepalese Class I bimaxillary protrusive patients. Angle Orthod 2010;80:91–6.  Back to cited text no. 19
de Carvalho Rosas Gomes L, Horta KOC, Gandini LG Jr, Gonçalves M, Gonçalves JR. Photographic assessment of cephalometric measurements. Angle Orthod 2013;83:1049–58.  Back to cited text no. 20
Yu XN, Bai D, Feng X, Liu YH, Chen WJ, Li S, et al. Correlation between cephalometric measures and end-of-treatment facial attractiveness. J Craniofac Surg 27;2016:405–9.  Back to cited text no. 21


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3], [Table 4]


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