A study to evaluate cephalometric hard tissue profile of Tamil population for orthognathic surgery.

The primary aim of this study is to compare, the cephalometric hard tissue profile values and analysis between Tamil and Caucasian population. The study also aims to create a better understanding in the facial proportions of Tamil Nadu population and to have better diagnosis and treatment planning for orthognathic surgery for Tamil population in Tamil Nadu.

This study is a cross-sectional study which is a gateway to conclude upon the normal hard tissue values of Tamil Nadu population. These values will give an edge in diagnosis and treatment planning for this prestigious population. The first step in the diagnosis of the orthognathic surgical patient is to determine the nature of the skeletal and dental defects using specialized cephalometric appraisal system called cephalometric analysis.

Various attempts have made to investigate the differences in facial features among ethnic groups including American[1]–blacks, Australian, Chinese, Japanese, Koreans, and Indians. Further studies have been done among Indians population.[234] From this review, it could be concluded that there are differences in dentofacial relationships of various ethnic and racial group.

The purpose of this study is to identify the normal values for the hard tissue profile.

It was difficult to differentiate Tamil population in Tamil Nadu as it had people from all over the Dravidian state like Andhra Pradesh, Karnataka, and Kerala. Hence, to be specific, we had to stick on to the communities specific to this particular ethnic population. The candidate or the volunteer should be native of Tamil Nadu for three generations belonging to the same communities for all three generations. This detail was confirmed by questionnaire set to the candidate.

A study was conducted to provide a description of the craniofacial morphology of Singaporean Chinese children and to compare gender differences.[56] The data provide useful reference cephalometric values for Singaporean Chinese children.[7]

Materials and Methods

Methodology

Sample constituted 54 individuals which included 28 males and 26 females with age ranging from 18 to 35 years were enrolled for the study consecutively who met inclusion and exclusion criteria. They were selected on the basis of their class I molar occlusions and well balanced facial profile.[8] The adults of Tamil Nadu origin residing in Tamil Nadu were included in the study. Lateral cephalograms were taken for each subject included in the study with their consent. A pre-structured proforma was used to collect the relevant information and record cephalometric measurements for each subject.

Inclusion criteria

Person who were native of Tamil Nadu

Class I molar occlusion with acceptable profile

Full permanent teeth with proper intercuspation

Normal limits of overjet and overbite

Presence of negligible crowding, rotations, and spacings

The candidate should be in Tamil Nadu and should be settled in Tamil Nadu for three generations who belongs to the communities of Tamil Nadu.

Exclusion criteria

Person with major dental and skeletal discrepancy like syndromic patients and gross class II and class III skeletal and dental patterns

History of trauma, fracture in maxillofacial region

History of previous orthodontic treatment, orthognathic or plastic surgery

People belonging to other state communities from Andhra Pradesh, Kerala, Karnataka were excluded.

Lateral cephalometric radiographs were taken for 54 people who were native of Tamil Nadu and met the above-mentioned criteria. Radiographs were taken in natural head position with the teeth in maximum intercuspation and lips in repose.

After standardization of cephalometric technique, the analysis for orthognathic surgery for hard tissue given by Burstone is used.

Sella (S), the center of the pituitary fossa

Nasion (N), the most anterior point of the nasofrontal suture in the midsagittal plane

Articulare (Ar), the intersection of basisphenoid and the posterior border of the condyle mandibularis

Pterygomaxillary fissure (PTM), the most posterior point on the anterior contour of the maxillary tuberosity

Subspinale (A), the deepest point in the midsagittal plane between the anterior nasal spine (ANS) and prosthion

Pogonion (Pg), the most anterior point in the midsagittal plane of the contour of the chin

Supramentale (B) the deepest point in the midsagittal plane between infradentale and Pg, usually anterior to and slightly below the apices of the mandibular incisors

Anterior nasal spine, the most anterior point of the nasal floor; the tip of the premaxilla in the midsagittal plane

Menton (Me), the lowest point of the contour of the mandibular symphysis

Gnathion (Gn), the midpoint between Pg and Me, located by bisecting the facial line N-Pg and the mandibular plane (lower border)

Posterior nasal spine (PNS) the most posterior point on the contour of the palate

Mandibular plane (MP), a plane constructed from Me to the angle of the mandible (Go)

Nasal floor (NF), a plane constructed from PNS to ANS

Gonion (Go), located by bisecting the posterior ramal plane and the mandibular plane angle.

Planes

Horizontal plane (HP) is a surrogate Frankfort plane constructed by line 7° from the line S to N

S-N Plane: A line joining sella and nasion

Nasal floor (NF): A line passing from ANS to PNS

Mandibular plane (Go-Gn): A line passing from gonion to gnathion

Functional occlusal plane (OP): A line extending from buccal groove of first molar to 1 mm above incisal edge of the central incisor

Long axis of upper incisors (U1)

Long axis of lower incisors (L1).

Figure 1 illustrates the reference planes used in the study.

Figure 1

Reference planes

Skeletal measurements

Cranial base

Posterior cranial base: Measured parallel to HP from articulare to PTM fissure

Anterior cranial base: Measured parallel to HP from PTM fissure to nasion.

This is illustrated in Figure 2.

Figure 2

Cranial base measurements

Horizontal (skeletal)

Angle of facial convexity: It is the angle formed between nasion-point A and pogonion [Figure 3]

Figure 3

Facial convexity

Apical base of maxilla to nasion: Measured from nasion to point A parallel to HP

Chin prominence: Measured parallel to HP from nasion to pogonion.

Vertical (skeletal, dental)

Anterior component

Middle third facial height: Measured perpendicular to HP from nasion to ANS

Lower third facial height: Measured perpendicular to HP from ANS to gnathion.

Posterior component

Posterior vertical height: Measured perpendicular to HP from PNS to nasion

Posterior facial diversions: It is the angle formed between mandibular planes (Go-Gn) to HP.

Dental

Anterior component

Anterior maxillary dental height: Measured from a perpendicular line dropped from the incisal edge of upper central incisor to the nasal floor

Anterior mandibular dental height: Measured from perpendicular line dropped from incisal edge of mandibular anterior teeth to the mandibular plane.

Posterior component

Posterior maxillary dental height: Measured from the mesiobuccal cusp tip of the maxillary first molar to the nasal floor

Posterior mandibular dental height: Measured from the mesiobuccal cusp tip of mandibular first molar to the mandibular plane.

Maxilla and mandible

Maxillary length: Distance between ANS and PNS

Mandibular ramal length: Measured from articulare to gonion

Mandibular body length: Measured from gonion to pogonion

Gonial angle: Angle formed between articularegonion and gnathion

Chin position: Measured from point B to pogonion.

Dental

Occlusal plane angle: Angle formed between OP and HP

Relation of maxilla and mandible to OP: Measured from the distance point A to point B dropped perpendicularly to OP

Upper incisor position: Determined by measuring the angle formed between the nasal floor and the long axis of upper central incisor

Lower incisor position: Determined by the angle between the mandibular plane and the long axis of the lower central incisor.

Statistical analysis

Mean, standard deviation, and range values were determined for the total sample male and female groups. The mean and standard deviation of each group and the values originally obtained by Burstone were subjected to Student's t-test using Excel program (Microsoft Corporation, Redmond WA, USA) and the level significance was set at 0.05.

Results

In our study, 54 individuals (28 males and 26 females) with age ranging between 18 and 35 years were enrolled for the study consecutively. They were selected on the basis of their excellent occlusions angles class I molar relation and well balanced facial pattern. Sample constituted adults of Chennai origin residing in Tamil Nadu. Lateral cephalograms were taken for each subject.

Various angular and linear measurements for hard tissues in both males and females were obtained and were tabulated. All the reading thus obtained were subjected to statistical analysis. Mean, standard deviation, and range values were determined for the total sample, male and female groups. The mean and standard deviations of each group and the values originally obtained by Burstone and Legan were subjected to a Student's t-test using Minitab software and the level of significance was set at 0.05.

Tables 1 and 2 show results of hard tissue measurements for males and females. Tables 3 and 4 show a comparison of hard tissue norms between Tamil Nadu population and Caucasian population for males and females.

Table 1

Study results of hard tissue measurements in males

Table 2

Study results of hard tissue measurements in females

Table 3

Comparison of hard tissue norms in males

Table 4

Comparison of hard tissue norms in females

Cephalometric comparison of Caucasian men and Tamil men

Tamil men have increased anterior and posterior cranial base length.

Horizontal (skeletal) relationship

Tamil men have reduced convex profile than Caucasian men

No significant difference in the horizontal relationship between both the population.

Vertical (skeletal) relationship

Posterior maxillary skeletal height is increased for Tamil men than the Caucasian men

Mandibular plane angle is low in Tamil population when compared with Caucasian men.

Figure 4 illustrates the vertical relationship.

Figure 4

Vertical measurements

Vertical (dental) relationship

Posterior dental height in maxilla is reduced when compared with Caucasian men

Posterior dental height in mandible is increased for Tamil men when compared with Caucasian men.

Maxillary mandibular relationship

Maxillary body length is increased in Tamil men

Ramus length is increased in Tamil men

Chin is less prominent when compared with Caucasian men.

Figure 5 illustrates the Maxilla Mandibular relationship.

Figure 5

Maxilla - Mandible

Dental relationship

Maxillary and mandibular incisal angulation is more in Tamil men [Figure 6].

Figure 6

Dental measurements

Cephalometric comparison of Caucasian women and Tamil women

Cranial base

Anterior and posterior cranial base for Tamil women is more compared with Caucasian women.

Horizontal (skeletal) relationship

No significant difference found when compared with Caucasian women.

Vertical (skeletal) relationship

Anterior maxillary height is increased in Tamil women than Caucasian women (or) increased anterior middle third facial height

Increased lower third facial height in Tamil women than in the Caucasian women

Increased posterior maxillary skeletal height in Tamil women than Caucasian women.

Vertical (dental) relationship

Maxillary anterior dental height is increased in Tamil women

Mandibular posterior dental height is increased in Tamil women than in Caucasian women.

Maxillary and mandibular relationship

Maxillary body length is increased in Tamil women

Mandibular ramus height is increased in Tamil women

Mandibular body length is increased in Tamil women

Chin prominence is reduced in Tamil women.

Dental relationship

Mandibular incisal angulation is increased in Tamil women

Discussions

In this study, the inclusion criteria and methodology were oriented to identify formative values that can assist in the diagnosis and treatment planning of adults of Tamil Nadu seeking orthognathic surgery. We intended to obtain a representative sample of the normal Tamil population. Hence, we did not include patients who have received orthodontic or any kind of cranial or facial surgical treatment or people from other states. Due to the facial growth and development, cephalometric studies whose samples included predominantly or exclusively children may not be useful for prospective orthognathic surgery cases. Similarly, patients of advanced age may show changes due simply to the aging process such as loss of vertical dimension between the jaws caused by attrition and loss of teeth. Keeping this in mind in the present study, the sample was limited to young adults with a range of 18–35 years.

Our study showed that males of this Tamil population had increased the posterior cranial base length and increased anterior cranial base length was present in both the sexes. There is less convex profile in the males and more convex profile in the female and also, increased maxillary and mandibular incisor proclination were noticed. It was inferred from our study that a separate norms for normal ethnic Tamil adults contemplating orthognathic surgery was needed. Table 5 shows hard tissue norms.

Table 5

Hard tissue norms for Tamil Nadu population

Conclusions

A cephalometric appraisal is only one step in diagnosis and planning of treatment. In the present study, surgically useful cephalometric norms for hard in the diagnosis and treatment planning of orthognathic surgery in adult Tamil population have been determined. There was a significant difference in the values of Tamil and Caucasian population. These differences should be considered when formulating the diagnosis and treatment plan for patients of Tamil Nadu contemplating surgery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.