Soft tissue cephalometric norms for a North Indian population group using Legan and Burstone analysis

Abstract

Cephalometric norms are used for providing guidance to clinicians during diagnosis and treatment planning. Most classical norms are not applicable to diverse racial and ethnic population hence the purpose of this study was to establish the soft tissue norms of a North Indian population group using Legan and Burstone soft tissue analysis. The study was conducted on 60 adult subjects with esthetically pleasing profiles aged 18–25 years. Standardized lateral cephalograms were taken in a natural head position and analyzed. North Indians were found to have more convex faces, protrusive lips and acute nasolabial angles compared with Caucasians. Males had more convex faces and protrusive lips than females. This North Indian population group had significant deviations from the Caucasian standards. Considerable diversity was also found for some of the soft tissue variables in males and females.

Facial esthetics is the most important determinant of facial beauty. It plays a unique role in all social interactions and in establishing self-image. The study of facial esthetic has been primarily the subject of artists and philosophers. Today facial appearance is an essential diagnostic criterion to be considered in comprehensive orthodontic treatment planning.

Orthognathic treatment is a comprehensive approach used to correct severe jaw discrepancy using a combination of fixed orthodontic appliances and jaw surgery. The objective of orthognathic treatment is to achieve a harmonious skeletal, dental and soft tissue relationship for the improvement of facial esthetics and function. In most cases the patient is solely interested in the esthetic outcome of the treatment . The study of soft tissue morphology is of utmost importance to the patient, and the dental professional must bear this in mind when planning treatment.

Cephalometrics is a valuable tool with many applications in this field. Various cephalometric analyses for orthognathic surgery have been designed . Cephalometric analysis confirms the diagnosis of hard and soft tissue disharmony by comparison with the normative values.

Legan and Burstone soft tissue analysis is one of the most common soft tissue analysis systems used for orthognathic surgery . It was modified from Burstone’s previous soft tissue analysis ; reducing the analysis to its most relevant measurements and adding new measurements significant for surgical patient. The standards described young adult Caucasians, but these norms may not be appropriate for patients from other ethnic or racial backgrounds as there are structural differences between different racial populations . Researchers in several countries have designed soft tissue norms for various ethnic and racial groups. Some showed great ethnic differences and others few . The clinician should use esthetic guidelines relevant to subjects of the same age, sex and ethnic group as their patients. Allowance can then be made for variations in facial attractiveness while maintaining the familial and ethnic characteristics that make a person unique.

India is a country in South Asia that comprises most of the Indian subcontinent. The original inhabitants of India were Dravidians, but over the centuries India has received waves of immigration leading to population dispersion. The invaders were gradually assimilated in North India, resulting in an Indo Aryan population in North India and Dravidians in South India .

Soft tissue norms for Indians have been compiled that are helpful in orthodontic treatment but few researchers have explored soft tissue norms for orthognathic surgery. This study is an attempt to establish the standard soft tissue cephalometric norms of a North Indian population group using Legan and Burstone soft tissue analysis, which has been used as a benchmark for planning orthognathic surgery.

Materials and methods

The sample comprised 60 North Indian adults (30 males and 30 females) aged 18–25 years. Standardized lateral cephalograms were taken for each subject with the following characteristics: Angle’s class I occlusion; normal overjet not exceeding 3 mm and overbite not more than 40%; spacing/crowding of not more than 3 mm; and a full complement of permanent teeth. Third molars were not taken into consideration. None of the subjects gave any previous history of orthodontic treatment or any orthognathic or plastic surgery.

Ethical approval was obtained from the Ethics Committee of GuruNanak Dev Dental College and Research Institute under Baba Farid University of Health Sciences, Faridkot (Punjab). Informed signed consent was obtained from all the participants after explaining the nature and purpose of the radiograph.

Standardized lateral cephalograms were taken for each subject on the ‘STRATO 2000’ cephalometric machine in a natural head position, with the teeth in maximum intercuspation and lips relaxed. The X-ray source-to-subject distance was kept at a constant distance of 165 cm (65 in.). The subject was asked to look into the reflection of his/her own eyes in the mirror to obtain a natural head position. The film was exposed while operating the cephalostat at a constant of 74 KVP, 12 mA and 0.8 s film exposure time. The magnification factor of the cephalostat was 1:1.1. All the exposed films were developed and fixed manually by a single technician using standard procedure. All lateral cephalometric films were traced and were analyzed using Legan and Burstone analysis ( Figs. 1 and 2 ).

Fig. 1
Legan and Burstone analysis: facial form.

Fig. 2
Legan and Burstone analysis: lip position.

Error due to fatigue was eliminated by the investigator tracing 5–10 cephalograms on average in a day. The correction of magnification difference between successive cephalograms was deemed unnecessary because all radiographs were taken on the same cephalostat. To eliminate inter-investigator variability all radiographs were analyzed by a single investigator. The intra-investigator error was assessed by tracing 20 randomly selected cephalograms on two separate occasions. Dahlberg’s formula was used to calculate the intra-investigator error, which was found to be insignificant. SPSS version 13.00 was used for data analysis. Student’s t -test was used to compare North Indian norms with Caucasian norms and to compare North Indian males and females.

Results

The descriptive statistics for the soft tissue cephalometric values are presented in tabular form. Table 1 shows intergender comparison of North Indians and Table 2 compares North Indians with Caucasians using Legan and Burstone analysis.

Table 1
Comparison of soft tissue cephalometric values of North Indians and Caucasians using Legan and Burstone analysis.
Variable North Indians Caucasians norms p -Value
Mean SD Mean SD
Facial form
Facial convexity angle (°) 13.34 4.76 12 4 0.033 *
Maxillary prognathism (mm) 5.83 4.33 6 3 0.767 NS
Mandibular prognathism (mm) −1.31 6.38 0 4 0.118 NS
Vertical height ratio 1.03 0.13 1.0 0.086 NS
Lower face–throat angle (°) 111.57 8.07 100 7 0.001 ***
Lower vertical height–depth ratio 1.22 0.18 1.2 0.302 NS
Lip position
Nasolabial angle (°) 95.79 11.36 102 8 0.001 ***
Upper lip protrusion (mm) 4.72 1.70 3 1 0.001 ***
Lower lip protrusion (mm) 2.83 1.64 2 1 0.001 ***
Mentolabial sulcus (mm) 5.82 1.23 4 2 0.001 ***
Vertical lip–chin ratio 0.44 0.05 0.5 0.001 ***
Maxillary incisor exposure (mm) 2.35 1.45 2 2 0.061 NS
Interlabial gap (mm) 0.24 0.73 2 2 0.001 ***
p ≥ 0.05 – non-significant (NS).

* p ≤ 0.05 – significant. ** p ≤ 0.01 – significant.

*** p ≤ 0.001 – highly significant.

Table 2
Comparison of soft tissue cephalometric values of North Indian males and females using Legan and Burstone analysis.
Variable Males Females p -Value
Mean SD Mean SD
Facial form
Facial convexity angle (°) 14.57 4.49 12.12 4.78 0.045 *
Maxillary prognathism (mm) 7.07 4.59 4.60 3.74 0.026 *
Mandibular prognathism (mm) −0.50 6.54 −2.11 6.23 0.331 NS
Vertical height ratio 0.97 0.10 1.08 0.13 0.001 ***
Lower face–throat angle (°) 113.23 8.18 109.92 7.75 0.112 NS
Lower vertical height–depth ratio 1.31 0.18 1.14 0.15 0.000 ***
Lip position
Nasolabial angle (°) 93.93 13.55 97.65 8.48 0.208 NS
Upper lip protrusion (mm) 5.23 1.83 4.20 1.42 0.018 *
Lower lip protrusion (mm) 3.23 1.77 2.43 1.42 0.059 NS
Mentolabial sulcus (mm) 6.08 1.04 5.57 1.36 0.105 NS
Vertical lip–chin ratio 0.45 0.05 0.44 0.05 0.817 NS
Maxillary incisor exposure (mm) 2.13 1.57 2.58 1.30 0.233 NS
Interlabial gap (mm) 0.22 0.76 0.27 0.70 0.793 NS
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Feb 7, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Soft tissue cephalometric norms for a North Indian population group using Legan and Burstone analysis
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