Cephalometric Evaluation of Natural Head Position in Lingayat Population of Karnataka.

AIMS AND
OBJECTIVES: To ascertain norms in cephalometry for 11- to 13-year-old Lingayat children in natural head position (NHP).
MATERIALS AND METHODS: Lateral cephalograms of children were obtained by using fluid level device. We determined the variance in Frankfort horizontal plane (FHP) inclination to extracranial horizontal in NHP. The G*Power, version 20 for Windows was used for analysis.
RESULTS: Reduced facial convexity was observed when the analysis was carried out in relation to true horizontal with significant difference of "t" value of 3.05 and percentage difference of 1.1 (P < 0.01) and for girls "t" value of 9.69 and percentage difference of 2.5 (P < 0.001). The highest correlation coefficient for Lingayat boys (r = 0.77) was seen between palatal plane and occlusal plane. We found least correlation coefficient among FHP and Sella-nasion plane (SNP). The coefficient was r = 0.62 and correlation coefficient of r = 0.70 was between FHP and determination coefficient r 2 = 0.38 or 38%. For girls, highest correlation coefficient of r = 0.70 was seen among FHP and palatal plane.
CONCLUSION: Conventional study of craniofacial forms of Lingayat children showed the average skeletal pattern as Class II with retrognathic mandible in comparison to Caucasians. However, when seen in NHP by new method of analysis based on the true horizontal, the skeletal model was Class III in comparison to Caucasians.

INTRODUCTION

Introduction of cephalometric evaluation in 1930s is considered as an important landmark in orthodontics. Now radiographic analysis is a necessary diagnostic tool, giving vital details about the growth and development of an individual.[1]

But proper interpretation of radiographs is still a problem, especially related to reference points or lines. Many analytic studies and continued discussions were carried out to arrive at a proper reference system. Conventional cephalometric analysis uses Frankfort horizontal plane (FHP) or Sella–nasion plane (SNP) as reference lines. However, many objected the usage of FHP as reference point. Sella position can differ both anteroposteriorly and vertically and is entirely not correlated to face structure and hence cannot be employed to measure development of face.[23]

The inception of natural head position (NHP) as an apt base for cephalometric analysis was in 1950s and since then many authors used it as a standard or fixed orientation to study facial morphology. But still it poses controversy even after many studies, as it is erroneous and difficult to maintain head postural position at the crossing point between standing and walking during the time of being transferred into cephalostat.[4567]

There is dissimilarity of craniofacial morphologic features in diverse ethnic groups. The cephalometric norms are generally based on Caucasian patient sample. In India, many communities exist in different regions with unlike ethnic background. But only few studies were done in past to establish cephalometric standards in Indian communities and applying the standards of Caucasians to other ethnic groups may result in incorrect treatment.[891011]

Lingayat community is mostly localized in North Karnataka, India. We carried this study to lay down cephalometric standards in 11- to 13-year-old Lingayat children in NHP.

MATERIALS AND METHODS

A total of 220 subjects (110 of each gender) belonging to Lingayat community from Bagalkot population (schools), aged 11–13 years were included. The study was carried out from January 2016 to December 2017. Sample size was calculated using G*Power software (Institute for experimental psychology in Dusseldorf, Germany). The obtained sample was rounded off to 220. We obtained institutional ethics committee approval (Ethics committee clearance no. PMNM/152/KA/2016) and also obtained consent from the parent/guardian of the children. Lateral cephalograms of children were obtained in NHP with a fluid level device.

Inclusion criteria consisted of the following:

Lingayat community children in the age group of 11–13 years.

Those with Angle’s Class I with normal alignment of teeth and minor crowding.

Absence of history of orthodontic management.

Absence of any deformity of facial skeleton.

Lateral cephalograms of 220 children in centric occlusion were taken by standardized cephalometric technique on “Trophies odontroma P.C. Mixte” cephalometric X-ray machine. Kodak films of size 8” × 10” were exposed at 70–80 kV/8–10 mA with 5’ and 2” film focus distance and 6” from the film and midfrontal plane, for 2–3 s.

The subjects were explained about the radiographic procedure. In view of language difficulty of Lingayat school children, services of bilingual assistant were used. Every child was provided the sugar-free cold drink to standardize their mental and physical state as these may influence the posture. Centric occlusion was confirmed and by using the wall mirror, each one was informed to occlude with the lip in light contact.

All patients were told to take one step front, smoothly move up and down, and later keep their eyes closed. The fluid level device placed on a strap was then tied on head of the patient. Strap position was standardized by placing it 2 mm above the eyebrows in the front and on the back, the strap lied exactly on the occipital protuberance. The subjects were then told to open his or her eyes and look into their own eyes in a mirror and then fluid level was readjusted or rotated on its pivot until the bubble was aligned in the center. The procedure was carried out again until two constant readings were obtained. They were made to sit on an adjustable hydraulic chair supported by wheels. Care was taken to move the chair but not the head, spine, or shoulder. The subject was then positioned in cephalostat, which had a plumb line (metallic wire hanged with the weight) in front of cassette to specify the true vertical. Ear posts were then lightly engaged. Subject’s head was not moved to fit the cephalostat.

Subjects were again instructed to see their eyes in mirror on the wall at 5 feet distance. Then before shooting the radiographs, head was again moved up or down until the same point of bubble was achieved as had been observed immediately before placing the subject on the chair. Now subjects were not asked anything as this often causes the head to be nodded in reply.

The z test was used to compare two positions. Normal values were prepared with 95% confidence limit. Simple correlation analysis was carried out for intracranial reference planes and paired t test to calculate systematic error.

RESULTS

Forty cephalograms (20 males and 20 females) randomly selected were again traced by the same operator. It was not significant in any variable. Random error was assessed through Dahlberg’s equation. Values were small and ranged between 1.2° and 2.9°.

Table 1 shows the mean value, standard deviation (SD), standard error (SE), and 95% confidence interval (CI) of Down’s analysis of 220 (110 males and 110 females) Lingayat children with FHP as the horizontal reference plane [Figure 1].

Table 1

Norms for Down’s analysis for Lingayat boys and girls

S. no.	Measurements	Mean		SD		SE		95% CI/Mean ± 2SD
		Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
1	Facial angle (Npog-FH)	86.45	86.56	3.03	7.33	0.29	0.70	80–93	72–101
2	Angle of convexity	6.38	5.39	4.55	2.80	0.43	0.27	0–15	0–10
3	AB plane	–6.29	–5.90	3.26	1.82	0.31	0.17	–3–13	–2–9
4	MP-angle (FMA)	22.72	21.46	4.87	3.24	0.46	0.31	13–28	15–28
5	Cant of occlusal plane	9.66	9.27	3.16	2.70	0.30	0.26	3–16	4–11
6	Interincisal angle	120.51	122.9	10.4	6.70	1.00	0.64	99–130	109–136
7	Incisor occlusal plane angle	23.82	21.95	6.52	4.17	0.62	0.40	11–37	13–30
8	IMPA	100.79	100.7	7.27	4.53	0.69	0.43	86–115	91–110
9	Protrusion of max. central incisor to APog (mm)	5.75	5.70	2.20	2.12	0.43	0.41	1–9	1–8

SD = standard deviation, SE = standard error, CI = confidence interval, Npog-FH = Nasion pogonion–Frankfurt horizontal, IMPA = incisor mandibular plane angle, FMA = Frankfort mandibular plane angle, APog = A-pogonion, AB plane = point A-point B to nasion-pogonion angle, MP = mandibular plane angle

Figure 1

Down’s analysis

Table 2 shows the mean value, SD, SE, and 95% CI of Cooke’s five-factor summary analysis of 220 (110 males and 110 females) Lingayat children with true horizontal as reference [Figure 2].

Table 2

Norms for Cooke’s five-factor summary analysis for Lingayat boys and girls

S. no.	Measurements	Mean		SD		SE		95% CI/mean ± 2SD
		Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
1	Angle 1	58.99	58.29	4.50	3.55	0.43	0.34	50–68	51–65
2	Angle 2	115.02	114.63	7.05	5.11	0.67	0.49	101–129	104–125
3	Angle 3	87.41	89.42	3.74	2.58	0.36	0.25	80–95	84–95
4	Angle 4	10.77	8.01	5.46	4.38	0.52	0.42	0–22	0–22
5	Angle 5	124.79	122.54	7.42	5.86	0.69	0.56	110–140	11–134

CI = confidence interval, SD = standard deviation, SE = standard error

Figure 2

Cooke’s five-factor summary analysis

Table 3 shows mean value, SD, SE, and 95% CI of Viazis analysis of 220 (110 males and 110 females) Lingayat children with true horizontal and true vertical as reference plane [Figure 3].

Table 3

Norms for Viazis analysis for Lingayat boys and girls

S. no.	Measurements	Mean		SD		SE		95% CI/mean ± 2SD
		Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
1	NA-TH	87.70	90.08	4.41	2.93	0.42	0.28	79–90	84–90
2	ANB	3.47	3.81	1.97	1.34	0.19	0.13	0–7	1–7
3	NP-TH	86.31	89.65	4.02	2.58	0.38	0.25	75–90	84–95
4	ANSPNS-TH	4.78	4.30	2.68	2.29	0.26	0.22	0–10	0–9
5	GoGn-TH	23.93	21.79	5.44	4.15	0.52	0.40	13–30	13–30
6	OP-TH	11.27	9.27	4.17	3.44	0.40	0.33	3–20	2–16
7	I1-GoGn	100.79	100.71	7.27	4.53	0.69	0.43	86–110	91–110
8	U1-ANS-PNS	117.53	115.54	5.22	4.81	0.40	0.33	107–125	109–125
9	S line-V line	–12.24	–11.45	4.34	3.53	0.41	0.34	–3–21	–4–11

SD = standard deviation, SE = standard error, CI = confidence interval, ANB = A point–nasion–B point angle, ANS = anterior nasal spine, PNS = posterior nasal spine, Go = gonion, Gn = gnathion, OP = opisthion, NA-TH = nasion-true horizontal, NP-TH = nasion-pogonion-true horizontal

S line: Line formed by connecting soft tissue pogonion and middle of an S formed by lower border of the nose

Figure 3

Viazis analysis

Table 4 shows the mean value, SD, SE, and 95% CI of the intracranial reference plane in correlation to true vertical reference line and the true horizontal [Figure 4].

Table 4

Intracranial horizontal reference plane in relation to the true vertical reference line and true horizontal derived from it for boys and girls

S. no.	Measurements	Mean		SD		SE		95% CI/mean ± 2SD
		Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
1	SN/vertical	83.37	82.76	4.81	3.97	0.46	0.38	73–93	75–91
2	FH/vertical	91.645	90.16	3.79	3.20	0.36	0.31	84–99	84–97
3	MxP/vertical	92.40	90.94	4.31	3.74	0.41	0.36	84–101	83–98
4	OP/vertical	100.88	98.80	4.26	3.79	0.41	0.36	92–109	91–106
5	MNP/vertical	113.57	111.42	5.60	4.01	0.53	0.38	102–125	103–119

SN = Sella–nasion, FH = Frankfurt horizontal, OP = Opisthion, MxP/MnP = maxillary plane/mandibular plane, SD = standard deviation, SE = standard error, CI = confidence interval

Figure 4

Intracranial horizontal reference plane in relation to the true vertical reference plane

Table 5 shows the inclination of FHP and SNP to true horizontal with head in NHP. Significant difference was seen for both genders [Figure 5].

Table 5

Inclination of the Frankfurt horizontal and Sella–nasion line with that of true horizontal in natural head position for boys and girls

S. no.	Measurements	Mean		SD		SE		95% CI/mean ± 2SD
		Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
1	SN-horizontal	7.66	8.79	4.01	3.68	0.38	0.35	0–15	1–15
2	FH-horizontal	3.83	3.25	2.00	2.11	0.19	0.20	–1.8–8	–1–7

SN = Sella–nasion, FH = Frankfurt Horizontal, SD = standard deviation, SE = standard error, CI = confidence interval

Figure 5

Inclination of the Frankfort horizontal and Sella–nasion plane to the true horizontal

Table 6 shows the relation of facial angle and true horizontal to be 87.41° ± 3.7° in comparison to FHP (86.45° ± 3.03°). This shows that facial convexity is reduced when the analysis is carried out in relation to true horizontal with significant difference of t value of 3.05 and percentage difference of 1.1 (P < 0.01) and for girls, t value of 9.69 and percentage difference of 2.5 (P < 0.001).

Table 6

Comparison between skeletal convexity as seen in natural head position and conventional method for boys and girls

S. no.	Angles	Conventional method (FH-NPg)		Natural head position (TH-NPg)		Difference		Significance (P)
		Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
1	Skeletal convexity	86.45 ± 3.03	86.56 ± 7.33	87.41 ± 3.74	89.42 ± 2.58	–0.95 ± 3.27	–2.20 ± 2.38	<0.01	<0.01

FH-NPg = Frankfurt horizontal–nasion pogonion, TH-NPg = true horizontal-nasion-pogonion

To evaluate the relation of the intracranial reference plane, a simple correlation analysis was carried out [Table 7]. The highest correlation coefficient for Lingayat boys (r = 0.77) was between palatal plane and occlusal plane. Although highly significant, the determination coefficient, r2 = 0.592 or 59.2%, indicates that approximately half of the variation of one plane can be described by variation of the other. We found least correlation coefficient among FHP and SNP. The coefficient was r = 0.62 and correlation coefficient of r = 0.70 was between FHP and determination coefficient r2 = 0.38 or 38%. For girls, highest correlation coefficient of r = 0.70 was between FHP and palatal plane.

Table 7

Correlation between four intracranial reference planes in natural head position for boys and girls

Reference plane	SN/vertical		FH/vertical		MxP/vertical		OP/vertical
	Boys	Girls	Boys	Girls	Boys	Girls	Boys	Girls
SN/vertical	--	--	-0.62***	0.60***	0.76***	0.49***	0.75***	0.63***
FH/vertical	--	--	--	-	0.71***	0.70***	0.67***	0.66***
MxP/vertical	--	--	--	-	-	-	0.77***	0.60***
OP/vertical	--	--	--	-	-	-	-	-

SN = Sella–nasion, FH = Frankfurt horizontal, OP = opisthion, MxP = maxillary plane

***Highly significant

DISCUSSION

Routinely recorded lateral cephalograms in NHP may be of greater importance clinically as they represent the orientation of face as in reality. The advantage of fluid level device is that it allows the assessment of reproducing orientation of head with no additional radiographs and by using it, patients can be effortlessly moved from standing to sitting position in the cephalostat.[121314]

Lingayat girls are head extenders, meaning head up posture with steep angulation of the anterior cranial base to true vertical reference line and Lingayat boys are head flexors meaning head down posture with anterior cranial base more horizontal, but statistically insignificant difference was seen with z value of 1.03. A possible explanation for this might be that girls are generally told to assume a good posture, looking straight ahead, perhaps boys assume a lazier head position. Our results are in contrast with the study by Huggare and Harkness.[15]

The introduction of an adjustable fluid level device attached to temple area forms our study basis and it is easy to use and also has a benefit of high reproducibility. We did not observe any literature on the cephalometric standards of Lingayat population in the NHP. Shortcomings of earlier literature carried in an attempt to ascertain population standards are that a large range of age or only adults were considered. Norms must be laid for children of around 12 years when orthodontic treatment generally is started.[16]

Norms of Cooke’s five-factor summary analysis in Lingayat children showed that they have a more or less horizontal growth pattern and a strong chin compared to the Caucasians and Chinese. Angle 2 (U1, horizontal) in Lingayat children showed that their upper incisors were proclined more when matched with Caucasians but are in the same range with that of the Chinese subjects.

Angle 3 (facial plane, horizontal) in Lingayat children and the Chinese did not reveal much significant variation among them but had a significant difference in comparison with Caucasians. This shows that Caucasian has a retruded mandible in comparison to the Chinese and Lingayat, as there is variation of SN to vertical in NHP. This finding confirms the results of Cooke and Wei, 1988.[17]

Angle 4 (AB, horizontal) in Lingayat children in comparison to Chinese did not reveal much differences between them in comparison with the norms of Cooke and Wei, 1988,[17] for AB-horizontal angles, skeletal class I–12 to 18°, skeletal class II > 18°, skeletal class III ≤ 12°. So according to these norms, Lingayat and Chinese skeletal pattern are Class III versus Caucasian skeletal pattern, which is Class I.[1718]

Conventional analysis showed that Lingayat subjects to be Class I with an A point–nasion–B point (ANB) angle of 3.47°, which is slightly Class II side of Caucasians ANB of 3.1° and similar to general view of previous studies of the Indian faces, the skeletal pattern tending toward Class II with the chin appear retrognathic.

Angle 5 L1-horizontal in Lingayat children showed that their mandibular incisors are upright in relationship to Chinese and Caucasians. This might be due to the fact that the Lingayats have a more horizontal growth pattern and a strong chin than the Chinese and Caucasians, so as the mandible grows forward, incisors are likely to be upright.[1920]

Highly significant intergroup difference was seen in reverence to the angulation between true vertical standard and intracranial reference planes. Lingayat children displayed more downward angulation when seen in NHP than Caucasians and more or less the same angulation compared to Chinese. Insignificant variation was seen among Lingayat and Chinese children, but in comparison to the Caucasians, the difference was highly significant (P < 0.00l).

All the angles in Lingayats were smaller than Caucasians with angular difference statistically significant for the opisthion (OP)/vertical (P < 0.05), a/vertical (P < 0.00l), but not much significant disparity in relation with FH/vertical and maxillary plane (MxP)/vertical. The probable reason might be that SN/vertical relates cranium to the vertical.[171820]

We strongly suggest that observed difference in the angulation of intracranial reference planes represents a true ethnic variation between Chinese, Lingayats, and Caucasians. Significant difference of P < 0.001 was seen among the Lingayats and Caucasians but not much significant variation was seen among Lingayats and Chinese. Hence, we assume that our craniofacial forms are similar to that of the Chinese, which may be as both the ethnic groups are more prevalent in the Asian continent.[1718192021]

Genderwise intracranial reference plane comparison revealed insignificant variation between them in SN/vertical angle (z value, 1.03), but significant difference was observed in relation to the FHP (P < 0.0l), the MxP (P < 0.05), occlusal plane (P < 0.001), and mandibular plane (P < 0.01). These findings confirm the findings by Cooke and Wei[1718] and they are suggested to use more reference planes. To evaluate how much the SN and FH intracranial horizontal reference plane is deviated from true horizontal, a simple analysis was proposed by Lundström and Lundström (1995).[22]

Significant difference of t value of 3.05 (P < 0.0l) was seen in facial plane angle between conventional method (FH as the horizontal) and NHP (true horizontal as the horizontal).[1718]

Despite the revealing fact that NHP is a more dependable reference plane during cephalometric analysis, the orthodontists worldwide continue to use different intracranial reference planes. There is an unambiguous need of a more comprehensive study to validate the dependability of NHP as a reference plane to erase the age-old concept of intracranial reference planes engraved in the thoughtful minds of orthodontists.

Summary of key findings

Lingayat children craniofacial form matches with that of Chinese children.

The facial profile of Lingayat boys is more convex than the girls.

When observed in natural position, based on the true horizontal, the true life skeletal pattern has been shown to be Class III in relation to the Caucasians.

Strengths of the study

Sufficiently large sample size

To be more precise and to avoid error, we have recorded all the radiographs with ear rods

First such study on Lingayat children

Limitations of the study

Intraindividual variations of NHP not taken into consideration

Standard deviation in angles was not considered

Future research

Future studies should focus on making subjects to sit on a stable position such as height-adjustable stool and use three-dimensional photographs for assessing NHP. Studies should also focus on reproducibility by taking images at different intervals in standing and sitting positions and also including subjects with malocclusion for orthognathic treatment purpose.

CONCLUSION

The craniofacial form of Lingayat children matched with that of Chinese children. Lingayat boys had more convex facial profile than the girls. When observed in natural position and using the new method of analysis based on the true horizontal, the true life skeletal pattern was Class III in comparison to the Caucasians.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.