International Medical Journal Vol. 20, No. 3, pp. 335 - 341 , June 2013
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ORAL SURGERY
Cephalometric Comparison of Skeletal, Dental, Soft Tissue, Nose and Chin prominence between Malaysian Indian and Malaysian Chinese
Kathiravan Purmal1), Mohammad Khursheed Alam2), Norzakiah Mohammad Zam Zam3)
ABSTRACT Objectives: To compare the cephalometric measurements between Malaysian Indian and Malaysian Chinese. Study Design: A cross sectional study of Malaysian Indian and Malaysian Chinese without any interracial marriage for two generations. Materials and Methods: Ninety seven Malaysian Indian and 98 Malaysian Chinese participants aged 18-25 were selected based on Class I incisor relationship with minimal crowding, no skeletal abnormality, have not undergone any orthodontic treatment and had at least second molar to second molar dentition. Lateral cephalometric radiographs were taken, traced and digitised to produce the values to assess the skeletal, dental, soft tissue, nose and chin positions. Results: There was a significant difference between the Malaysian Indian and Malaysian Chinese on most values. Malaysian Chinese have a maxilla and mandible which is set more forward than the Malaysian Indians. Vertically there is more development in the posterior facial height for Malaysian Chinese and more anterior facial height development in the Malaysian Indians. The Chinese have bidental and lips protrusion. In conclusion: This study is to facilitate the description of dentofacial pattern/relationship, diagnosis and treatment planning, evaluation of treatment results, evaluation of stability and as a baseline data for further research.
KEY WORDS lateral cephalometric radiographs, cephalometric norms, Malaysian adult Indian
INTRODUCTION The introduction of radiographic cephalometrics by Broadbent (1931) in United States provided both a research and a clinical tool for the study of malocclusion and underlying skeletal structure. Bjork (1947) and Downs (1948) were among the pioneers who established cephalometric standards to be used as guidance for treatment planning of orthodontic patients. Most cephalometric studies have proven that the 'norms' should be based on ethnic, sex and age differences (Cooke and Wei, 1989; Yeong and Huggare, 2004; Ajayi, 2005; Wu et al., 2007; Alam et al., 2012; Alam et al., 2013). In Malaysia, the ethnic composition is made up of three main races, which are: Malays (10.9 million), Chinese (5.6 million) and Indians (1.6 million) (National Statistic Center Publication Year 2000). A comprehensive study of the cephalometric norms of Malays and the Caucasians has been done by Hassan (1998). There are numerous studies done on the Chinese community both internationally and locally (Chan, 1972; Foo, 1986; Cooke and Wei, 1988). However the numbers of studies for the Indian community are limited (Kotak, 1964; Kharbanda et al., 1991a and 1991b). The principle of
the analysis is to compare the patient with a normal reference group so that differences between the patients' actual dentofacial relationship and those expected for his racial and ethnic group are revealed. To date, no studies have been found in the literature to compare the cephalometric measurements between Malaysian Indians and Malaysian Chinese. The purpose of this study is therefore to compare the cephalometric measurements between Malaysian Indians and Malaysian Chinese. It is believed this study will facilitate in comprehensive diagnosis of malocclusion and skeletal discrepancy, evaluation of the progress and result of treatment, identification of the degree of difference from the normal value in our orthodontic patients, treatment planning for orthognathic surgery and would act as a baseline for further research in this area.
Received on June 21, 2012 and accepted on September 11, 2012 1) School of Dental Science, Universiti Sains Malaysia 2) Orthodontic Unit, School of Dental Sciences, Universiti Sains Malaysia 3) Department of Children Dentistry and Orthodontics Dental Faculty, University Malaya Correspondence to: Kathiravan Purmal (e-mail:
[email protected])
C 2013 Japan International Cultural Exchange Foundation & Japan Health Sciences University
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Figure 1. Summary of Cephalometric landmarks. Sella; Nasion; STNasion, soft tissue nasion; Porion; Autorotation point; Orbitale; Articulare; PNS, posterior nasial spine; ANS, anterior nasal spine; UIApex, upper anterior apex; A, A point; Columella; U6DC, upper 6 distal cusp; U6MC, upper 6 mesial cusp; UPM, upper premolar point; LiTip, lower incisor tip point; LabrSup, Labriale superiolis; L6DC, lower 6 distal cusp; L6MC, lower 6 mesial cusp; LPM, lower premolar point; UiTip, upper incisor tip point; Labrinf, labriale inferiolis; B , B point; LiApx, lower incisor apex; Gonion; STPog, soft tissue pogonion; Pog, pogonion; Menton.
incisor edges occludes with or lie immediately below the cingulum plateau of the upper central incisors), no previous orthodontic treatment, full dentition from second molar to second molar, no skeletal abnormality, no incisor crowding and subjects whom both parents and grandparents are Malaysian Indian without any interracial marriage. At least two generations must have been Malaysians. Ethical approval was obtained from the research committee of the Dental Faculty of University Malaya. Consent form and patient information sheet about the research project was given to the participants. A clinical examination was conducted by one of the author to determine that the subjects met the inclusion criteria. Questionnaires were given to the subjects to confirm that both parents and grandparents were Malaysians without interracial marriage. A total of 97 and 98 participants were included in this study, with a mean age of 21.7 and 22.2 of Malaysian Indian and Malaysian Chinese respectively. Each subject was positioned in the cephalostat with the head oriented to the Frankfort horizontal plane and the teeth in centric occlusion with the lips relaxed. A Bennett cephalostat at 68kV, 12 miliampere and 40msec was utilized. All radiographs and tracing was done by a single author. All points were standardised and oriented to the Frankfort Horizontal (FH) plane (Ricketts et al., 1976). For example Point B (supramentale) which is the most posterior in the concavity of mandible was located by moving the ruler perpendicular to FH until it touches the innermost point of the curvature (Jacobson, 1995). Twenty three hard tissues and 5 soft tissue landmarks were digitised (Table 1). From these, 12 skeletal, 7 dental, 6 soft tissue, 2 nose prominence and 3 chin prominence variables were obtained using the OPAL Image 2.0 software designed by Dr N.W.T. Harridine and Dr D.J. Birnie (Figure 1). The software was also used to correct the magnification difference in the linear measurements prior to statistical analysis.
SUBJECTS AND METHODS Control of Error The steps taken to minimise the errors were: This was a cross sectional study involving the collection and analysis of lateral cephalometric radiographs of volunteers. The samples were from students of the University of Malaya and dental patients in the Faculty of Dentistry, University of Malaya who fulfilled the inclusion criteria. The samples collection were based on; the age group between 18 to 25 years old, subject with normal occlusion as based on the British Standards Institute (BSI 4482, 1982, Williams and Stephens, 1992); that is an occlusion satisfying the requirements of function and aesthetics with a Class I incisor relationship (lower
a) Radiographic technique - All x-rays were taken by the author to ensure standardisation. A metal ruler was incorporated to allow for enlargement calculation. b) Landmark identification - Clear definition was used and the author was calibrated with an experienced researcher in cephalometrics with a different set of radiographs periodically. c) Randomisation - The radiographs were measured in random using scientific calculator to generate a random number.
Figure 2. Linear graph of cephalometric values of Indians, Chinese and Caucasians 1 = Age 2 = SNA 3 = SNB 4 = ANB 5 = SN/MxP 6 = MxP/MnP 7 = LAFH 8 = UAFH 9 = LAFH/TAFH 10 = LPFH 11 = UPFH 12 = PFH 13 = Wits 14 = OJ 15 = OB 16 = UI/MxP 17 = LI/MnP 18 = Iiangle 19 = Li-Apog 20 = Li-Npog 21 = LS 22 = ExpUI 23 = LS-E 24 = LI-E 25 = NLA 26 = LLA 27 = NT 28 = NA 29 = CT 30 = B-Npog 31 = LADH ◆ Indien Chinese ▲ Caucasian
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Cephalometric Comparison between Malaysian Indian and Chinese Table 1. Hard and soft tissue landmarks/ variables Measurements
Table 2a. Comparison of cephalometric skeletal measurements between Malaysian Indians and Malaysian Chinese (n = 97 and 98 respectively)
Skeletal SNA
angle between Sella-Nasion and Nasion - A point
SNB
angle between Sella-Nasion and Nasion - B point
ANB
SNA minus SNB
Wits
distance along functional occlusal plane
SN/MxP
angle between Sella-Nasion to ANS-PNS (Maxillary plane)
MxP/MnP
angle between Maxillary plane and Mandibular plane
LAFH
perpendicular distance from menton to maxillary plane
UAFH
distance from Sella to Maxillary plane
LPFH
distance from Gonion to PNS
UPFH
distance from Sella to PNS
PFH LAFH/TAFH
95% ConfidenceInterval Variable
SNA SNB ANB
distance from Sella to Gonion lower anterior facial height as a percentage of total facial
SN/MxP
height MxP/MnP
Dental OJ
distance between upper incisal tip and lower insisal tip
LAFH
(horizontal) OB
distance between upper incisal tip and lower insisal tip
UAFH
(vertical) Iiangle
posterior angle between the long axis of the upper and
LAFH/TAFH %
lower incisors LI-Apog
perpendicular distance from lower incisor tip to a line con-
LPFH
necting A and Pogonion Li-Npog
perpendicular distance from lower incisor tip to Nasion-
UPFH
Pogonion Soft tissue LS
PFH vertical seperation of the lips.
ExpUI
distance from bottom of upper lip to the upper incisor tip
LS-E
distance from labrale superious to the E line(Ricketts, 1968)
LI-E NLA
Mean
SD
For Mean Lower
Upper
Bound
Bound
Indian
83.71
1.22
83.46
83.95
Chinese
87.03
2.85
86.46
87.60
Indian
80.86
1.09
80.64
81.08
Chinese
84.29
2.58
83.77
84.80
Indian
2.85
1.70
2.51
3.19
Chinese
2.74
1.39
2.46
3.02
Indian
5.49
2.54
4.98
6.01
Chinese
5.06
1.15
4.83
5.29
Indian
26.12
3.15
25.49
26.76
Chinese
25.13
2.26
24.68
25.59
Indian
68.85
5.15
67.81
69.89
Chinese
62.05
3.07
61.44
62.67
Indian
52.37
1.15
52.14
52.60
Chinese
52.68
1.89
52.31
53.06
Indian
56.73
1.64
56.40
57.06
Chinese
54.07
0.79
53.91
54.23
Indian
46.99
1.55
46.68
47.31
Chinese
48.22
1.30
47.96
48.48
Indian
50.78
3.26
50.13
51.44
Chinese
52.98
1.21
52.74
53.22
Indian
81.18
4.05
80.36
81.99
Chinese
85.69
5.18
84.65
86.73
Indian
2.27
1.97
1.88
2.67
Chinese
-1.09
2.10
-1.51
-0.67
p value
0.001 0.001 0.619 0.126 0.002 0.001 0.167 0.001 0.001 0.001 0.001 0.001
p < 0.001 (significant at 0.1% level) SD = Standard deviation
distance from labrale inferious to the E line angle between columella-subnasale to subnasale-labrale superius
LLA
Wits
Group
angle between labrale superious/inferior labial sulcus/soft
RESULTS
tissue pogonion NT
distance from tip of nose to soft tissue nasion
NA
angle between vertical and soft tissue nasion to nose tip
CT
perpendicular distance from soft-tissue pogonion to softtissue nasion
B-Npog
distance from B point to a line joining nasion and pogonion
LADH
distance from menton to lower incisor tip
d) Experimental design - The function of double digitising on the Opal software was utilised to increase accuracy. The difference in the first and second digitizer was set at 0.5 mm. Repeat measurement was done if this set level was not achieved. e) Error of methods - Calculations were made for 25 radiographs to assess the random and systemic error. These measurements were measured again two weeks later. The errors were assessed using two sample t test and index of reliability for each pair of readings.
Statistical Analysis for study All variables were measured for significance using the range in 95% confidence interval and the p value from one way analysis of variance (ANOVA) with confidence level set at 0.1% to test for significance among the sexes.
Systemic and random errors were assessed using two-sample t-test and index of reliability for each pair of readings. There was no significant difference in all the pairs of measurements (p > 0.05) and the index of reliability showed good correlation (value of correlation was above 0.9). The results comparing Malaysian Indian and Malaysian Chinese cephalometric values of skeletal, dental, soft tissue, nose and chin prominence are presented in Table 2a-e.
Skeletal measurements (Table 2a) Sagital measurements At 95% confidence interval SNA for Indians was (83.45˚, 83.95˚) and for Chinese it was (86.46˚, 87.60˚). Therefore there was a significant difference for this variable. There was also significant difference in SNB in which the 95% confidence interval for Indians was (80.64˚, 81.08˚) and for Chinese it was (83.77˚, 84.80˚). The mean ANB for Indians was 2.85˚ ± 1.70 and for Chinese it was 2.74˚ ± 1.39. There was no significant difference in this variable at 0.1% level. In Indians the Wits value was 2.27 mm ± 1.97 and Chinese had a negative value of -1.09 mm ± 2.10. There was a significant difference in this variable at 0.1% level.
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Table 2b. Comparison of cephalometric dental measurements between Malaysian Indians and Malaysian Chinese (n = 97 and 98 respectively) Variable
Group
Mean
SD
95%
Table 2c. Comparison of cephalometric soft tissue measurements between Malaysian Indians and Malaysian Chinese (n = 97 and 98 respectively) Variable
Group
Mean
SD
95 %
Confidence Interval
Confidence Interval
Lower
For Mean
Upper
Bound
Bound
p value
Lower
Upper
Indian
3.28
0.69
3.14
3.42
0.005
Bound
Bound
p value
Chinese
3.18
0.72
3.04
3.33
0.978
OB
Indian
3.56
1.49
3.26
3.86
Chinese
3.14
1.02
2.93
3.34
UI/MxP
Indian
104.60
3.12
103.97
105.23
Chinese
122.92
1.66
122.59
123.26
LI/MnP
Indian
97.13
2.59
96.61
97.65
Chinese
101.27
1.51
100.97
101.57
Indian
132.70
1.30
132.43
132.96
Chinese
116.06
2.29
115.60
116.52
Indian
3.94
0.90
3.76
4.12
Chinese
4.62
0.82
4.45
4.78
Indian
4.73
1.08
4.52
4.95
Chinese
5.58
0.98
5.39
5.78
OJ
Ilangle Li-Apog Li-Npog
Lip Sep 0.003 Exp UI 0.001 LS - E 0.001 LI - E 0.001 NLA 0.001 LLA 0.001
Indian
0.19
1.00
-0.02
0.39
Chinese
0.19
0.56
0.08
0.30
Indian
2.24
1.99
1.84
2.64
Chinese
0.16
0.78
0.01
0.32
Indian
-2.09
1.02
-2.30
-1.89
Chinese
-0.43
1.00
-0.63
-0.23
Indian
0.13
0.99
-0.07
0.33
Chinese
1.66
0.91
1.48
1.85
Indian
98.60
14.14
95.75
101.45
Chinese
102.10
2.41
101.62
102.59
Indian
118.65
3.93
117.86
119.45
Chinese
144.70
1.21
144.46
144.95
0.001 0.001 0.001 0.001 0.001
p < 0.001 (significant at 0.1% level) SD = Standard deviation
p < 0.001 (significant at 0.1% level) SD = Standard deviation
Table 2d. Comparison of cephalometric nose prominence measurements between Malaysian Indians and Malaysian Chinese (n = 97 and 98 respectively) Variable
Group
Mean
SD
95 % Confidence
Table 2e. Comparison of cephalometric chin prominence measurements between Malaysian Indians and Malaysian Chinese (n = 97 and 98 respectively) Variable
Group
Mean
SD
Interval For Mean
NT NA
Lower
Upper
Bound
Bound
p value 0.001
Indian
25.45
1.50
25.15
25.75
Chinese
22.79
2.73
22.24
23.33
Indian
34.01
1.24
33.76
34.26
Chinese
30.74
1.16
30.51
30.98
95 % Confidence
ANOVA
Interval For Mean
0.001
p < 0.001 (significant at 0.1% level) SD = Standard deviation
Chin Tip B-Npog LADH
Lower
Upper
Bound
Bound
p value 0.001
Indian
0.07
1.81
-0.30
0.43
Chinese
8.45
3.70
7.71
9.19
Indian
-0.24
1.41
-0.52
0.05
Chinese
-0.10
0.87
-0.28
0.07
Indian
38.95
3.72
38.20
39.70
Chinese
37.69
3.01
37.09
38.29
0.422 0.010
p < 0.001 (significant at 0.1% level) SD = Standard deviation
Vertical measurements Vertically the Indians had a significantly higher value of LAFH (68.85 mm˚ ± 5.15), ratio of LAFH/TAFH (56.73% ± 1.64) and UPFH (50.78 mm ± 3.26) but a smaller value for LPFH (46.99 mm ± 1.55). The Chinese mean for LAFH was 62.05 mm ± 3.07, ratio of LAFH/TAFH was 54.07% ± 0.79, LPFH was 48.22 mm ± 1.30 and UPFH was 52.98 mm ± 1.21, but a higher value for LPFH which was 8.22 mm ± 1.30 and PFH was 85.69 mm ± 5.18. There was no statistically significant difference in the UAFH between Chinese (52.37 mm ± 1.15) and Indians (52.68 mm ± 1.89). The angular measurements, MxP/MnP and SN/MnP did not show any significant difference. The confidence interval at 95% for MxP/MnP in Indians was (25.49˚, 26.70˚) and for Chinese it was (24.68˚, 25.59˚). For variable SN/MxP the confidence interval at 95% for Indians was (4.98˚, 6.01˚) and for Chinese it was (4.83˚, 5.29˚).
Dental Measurements (Table 2b) At 95% confidence interval UI/MxP for Indians was (103.97˚, 105.23˚) and for Chinese it was (122.59˚, 123.26˚). As there was no overlap, there was a significant difference in both races. In fact all the values measured in this category except OJ and OB showed significant difference in both groups. For Indians the mean for Li/MnP was 97.13˚ ± 2.59, IIangle was 132.70˚ ± 1.30, Li-Apog was 3.94 mm ± 0.90 and Li-NPog was 5.58 mm ± 0.98. At 95% confidence interval OJ in Indians was (3.14 mm, 3.42 mm) and for Chinese it was (3.04 mm, 3.33 mm). Therefore there was no significant differ-
ence between both races. At 95% confidence interval, the OB for Indians was (3.26 mm, 3.86 mm) and for Chinese it was (2.93 mm, 3.34 mm). Therefore there was also no significant difference in OB.
Soft tissue measurements (Table 2c) The variables ExpUI, LS-E and LI-E showed significant difference in both groups. Only the amount of LS did not show any statistical significant difference at 0.1% level. For Indians, 95% confidence interval for mean of ExpUI was (1.84 mm, 2.64 mm), LS-E was (2.30 mm, -1.89 mm), LI-E was (1.48 mm, 1.85 mm) and LLA was (144.46˚, 144.95˚). For Chinese 95% confidence interval for ExpUI was (0.01 mm, 0.32 mm), LS-E was (-2.30 mm, -1.89 mm), LI-E was (1.48 mm, 1.85 mm) and LLA was (144.46˚, 144.95˚). The mean LS for Indians were 0.19 mm ± 1.00 and for Chinese it was also the same 0.19 mm ± 0.56. The mean for NLA in Indians was 98.60˚ ± 14.4 and for Chinese it was 102.10˚ ± 2.41. The NLA for Indians showed a large standard deviation that was 14.4 mm.
Nose prominence measurements (Table 2d) Both parameters NT and NA were significantly more in Indians
Cephalometric Comparison between Malaysian Indian and Chinese (p < 0.001). The mean NT for Indians was 24.45 mm ± 1.50 and for Chinese it was 22.79 mm ± 2.73. The mean NA for Indians was 34.01˚ ± 1.24 and for Chinese it was 30.74˚ ± 1.16.
Chin prominence measurements (Table 2e) Only the CT measurement was significantly different. At 95% confidence interval, CT was (-0.30 mm, 0.43 mm) for Indians and for Chinese it was (7.71 mm, 9.19 mm). The mean for other measurement in this category that is B-Npog for Indians was -0.20 mm ± 1.41 and for Chinese it was -0.10mm ± 0.87. The mean LADH for Indians was 38.95 mm ± 3.72 and for Chinese it was 37.69 mm ± 3.01. Linear graph of cephalometric values of Indians, Chinese and Caucasians were showed in Figure 2 and conferred in the discussion part.
DISCUSSION
In our study, we have selected the sample based on the criteria as specified in the materials and methods. Many studies of cephalometric norms have selected samples based on certain criteria (Downs, 1948; Riedel, 1952; Goldsman, 1959; Bishara and Fernandez, 1985). Other researchers (Ajayi, 2005; Dandajena and Nanda, 2003; Hamdan and Rock, 2001; Kalha et al., 2008) have used similar selected sample to derive the norm values for the various ethnic groups. Normal is not easy to define and normal in one ethnic population may not be considered normal in another population. In Malaysia, the distribution of malocclusion appears to vary between populations but is predominated by Class I occlusion (Woon 1982). Hence we can assume that Class I occlusion is considered normal in the majority of population and therefore selection of sample based on ideal or normal occlusion is rational. Stirrups (1993) mentioned that confidence interval is good way of presenting results which allows evaluation of clinical relevance without having a full understanding of the complex statistical test. Therefore, the results are presented in the confidence interval of 95% (upper bound, lower bound) form and the mean of the variable with the standard deviations. The differences between the Malaysian Indian and Malaysian Chinese are considered significant if P < 0.001 from the analysis of variance.
Skeletal The anteroposterior spatial relationship of the jaws relative to nasion was measured using the angle SNA and SNB. The SNA for Indians was 83.71˚ ± 1.22 and for Chinese it was 87.03˚ ± 2.83. This indicates that the Chinese maxilla was set more forward than the Indian maxilla in relation to the cranial base. The mandible was also more prognathic in the Chinese as indicated by the SNB (84.29˚ ± 2.58) compared to the Indians whose SNB was (80.86˚ ± 1.09). The ANB angle represents the difference between SNA and SNB angles. It defines the mutual relationship in the sagital plane of the maxillary and mandibular bases (Rakosi, 1982). There was no significant difference in the ANB of both Chinese (2.74˚ ± 1.39) and Indians (2.85˚ ± 1.70). These values indicate that they have a Class I skeletal pattern. This was probably due to the fact the inclusion criteria for this study was a Class I skeletal pattern. The position of sella in the cranium can affect the angles SNA and SNB without affecting the angle ANB. This may be verified by relating the maxillary plane to the sella-nasion plane. For example if the angle SNA was reduced because of low position of sella rather than a forward position of nasion, the angle between the sella-nasion plane and the maxillary plane will be increased (Mills, 1970). The angle SN/MxP for Indian was 5.49˚ ± 2.54 and for Chinese it was 5.06˚ ± 1.15. These value falls in between 5˚-11˚ which is appropriate
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for compensation (McDonald and Ireland, 1998). Variation in the anteroposterior and vertical position of nasion will affect angle ANB, the significance of which varies according to the size of angle SNA. The severity of the anteroposterior dental base discrepancy when judged by the value of angle ANB alone may be masked. A method of adjustment is incorporated into Eastman analysis to compensate for variety in the angle SNA. For every degree SNA is greater or less than 81 degrees, half of a degree is subtracted / added from the original ANB angle. In this study, the adjusted ANB for Indians would be 2˚ and for Chinese 0˚. This indicates a Class III skeletal pattern for the Chinese and Class I skeletal pattern for Indians. The relationship of the maxilla to the mandible was further tested using the Wits appraisal (Jacobson, 1975). The purpose of this assessment was to identify instances in which the ANB reading did not accurately reflect the extent of anteroposterior jaw relationship. A few factors can influence the ANB reading such as the position of nasion and the rotational effect of the jaws relative to the anterior cranial base. The results showed the Chinese mandible was more forward (-1.09 mm ± 2.10) and the Indian maxilla was set further back (2.27 mm ± 1.97). This further strengthens the conclusion that the Chinese jaw had a tendency for class III pattern and Indians had a class I skeletal tendency. This protrusive skeletal pattern from values of SNA and SNB was also similar to those found in the Chinese by Chan (1972), Cooke and Wei (1988), Malaysian Chinese male vs female by Kathiravan et al. (2012), Saudi Arabians (Shalhob et al., 1987), Mexican American (Gracia, 1975) and American Negros (Kowalski et al., 1974). When comparing the Indians to the Chinese, the latter had a tendency towards a Class III skeletal pattern due to a more forward position of the mandible. Lew (1994) in Singapore who did a comprehensive study on three races; Malay, Chinese and Indians concluded that Indians had a straighter profile as a result of less protrusive jaws and teeth (further discussion in the dentoalveolar section). The angular measurement for vertical proportions Sn/MxP and MxP/MnP did not show any significant difference (p < 0.001). The angle Mx/MnP defines the angle of inclination of the mandible to the maxillary base. This angle also serves to determine rotation of the mandible. In this study the angle for Indian was 26.12˚ ± 3.15 and for Chinese it was 25.13˚ ± 2.26. This angle was similar with Malaysian Malays 26˚ ± 5 and Caucasians 25˚ ± 5 by Hassan (1998). There was also no significant difference in the other angular measurement SN/MxP. However there was significant difference in the linear vertical measurement. The contrasting results between the angular and linear measurement could be due to the differences in the inclination of SN plane or the maxillary plane. The LAFH was significantly different in Chinese (62.05 mm ± 3.07) and Indians (68.85 mm ± 1.89) but the UAFH was almost similar; Chinese (52.37 mm ± 1.15) and Indians (52.68 mm ± 1.89). The Indians have a longer lower facial height (difference of 6.8 mm). However the ratio of LAFH/TAFH for Indians was 56.76% and for Chinese it was 57.07%. This difference was statistically significant at 0.1%. Clinically the difference of 2% may not be obvious. Therefore for facial balance the ratio was more important than the exact linear measurement (Kharbanda et al., 1991a). Herzberg and Holic (1943) mentioned that the proportion of upper facial height to total facial height was similar in many racial groups but our results do not support this. The mean value for LPFH, UPFH and PFH for Indians were (46.99 mm ± 1.55), (50.78 mm ± 3.26) and (87.18 mm ± 4.05) respectively. For the Chinese the values were higher which showed there was considerably more development in the posterior in the Chinese whereas in Indians the development was more on the anterior facial height. The mean value given by Jarabak was 62-65%. In this study the Chinese had a greater face height with a value 74% compared to the Indians whose ratio was 65%.
Dental There was no significant difference (p > 0.001) in the overjet and overbite because these were the inclusion criteria. Significant difference was observed in all the other angular measurements (p < 0.001). The Chinese have bimaxillary dental protrusion in comparison with the Indians. This was in agreement with other studies like Hong Kong Chinese (Chan, 1972), Taiwan Chinese (Yen, 1973) and Koreans (Park et al., 1989). The upper incisors of the Chinese were 18.32˚ more proclined than the Indians. The lower incisors were 4.14˚ more proclined in the Chinese. The interincisal angle was significantly less
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in the Chinese sample (116.06˚ ± 2.29) compared to the Indians (132.70˚ ± 1.30). This contributes to the bimaxillary dental protrusion. The linear relationship of the lower incisors to the dental base was assessed by measuring the tip of the lower incisors to A-Pog line and N-Pog lines. Both analyses confirmed that the Chinese had more forward positioned lower incisors. The lower incisor to A-Pog was 4.62 mm ± 0.82 in Chinese compared to 3.94 mm ± 0.90 in the Indians. Downs (1948) mentioned an ideal incisor position to be 0.5 mm in relation to the A-Pog line and Rickets (1957) on the other hand gave a value of 1 mm ± 2 to be normal and stable position. As our research indicates stable position of incisor is more than previously advocated, we need to re-evaluate our treatment planning which is based on Caucasian norms. Further studies are needed in the comparison of stability of treatment using the new norms and with the Caucasian norms. There are two main reasons in the importance of lower incisor to A-Pog line: stability and space estimation. Mills (1968) stressed that proclinaton of lower incisor would result in relapse because of lip pressure and muscular imbalance. Mills added there are exceptions to this rule which are: i) retraction of lower incisors in Class III case if a sufficient overbite is established ii) proclination of lower incisors in class II cases in patients with digit/dummy sucking habits iii) patient with a class II div II cases where proclination to a true soft tissue balance will be stable. The amount of space required in the mandibular arch can be assessed using the A-Pog line. The reason for using the lower incisor to A-pog is because advancing or retracting the mandibular incisor by 1 mm will result in either 2 mm gain or 2 mm reduction in the mandibular dental arch (Jacobson, 1995). Therefore a clinician can plan whether an extraction or non-extraction approach should be followed. The Li-NPog measurement was used to counter check the LiApog. This value was protrusive in Indians (4.73 mm ± 1.08) and Chinese (5.57 mm ± 0.98). The average Caucasian value was between -2 to + 2 mm. This figure is important in treatment planning and deciding: a) whether extraction is indicated. b) whether the lower incisors can be moved further. c) whether anchorage is critical (Rakosi, 1982).
Soft tissue The amount of lip separation was the same for both races although the SD for Indians was 1 mm and for Chinese it was 0.36 mm. The normal value given by Legan and Burstone (1980) was 2 mm ± 2 which was consistence with our finding. Lew et al., (1994) also concluded in their study that there does not seem to be a marked difference with regard to the lip separation between Singaporean Indian, Chinese and Malays. There was a statistically significant different of the amount of incisor shown between both races at 0.1% level. The Indians showed more incisor (2.24 mm ± 1.99) compared to the Chinese where there was hardly any show of incisors (0.16 mm ± 0.78). Arnett and Bergaman (1999) mentioned that a relaxed upper lip should cover three quarter or two third of the upper incisors or leave about 2 mm incisor showing. However Athanasiou (1995) believes that these values should be taken in range. For example in patients with decrease facial height, there should be more incisor show (three quarter lip covers) and vice versa. Athanasiou (1995) rationalized that the decrease in lip length is almost impossible to alter and a necessary vertical change in the incisor position is often compromising the patient's appearance. In relation to the aesthetic plane, Ricketts (1968) found that the lower lip position is 1-2 mm and upper lip position is 2-3 mm behind a line drawn from tip of nose to skin pogonion. Lips which protrude beyond the aesthetic plane seemed undesirable in adults. In this study there was significant difference (p < 0.001) in the lip position of both races. In the Indians, the upper lips were -2 mm ± 1.02 behind the aesthetic line and the Chinese upper lips were -0.04 mm ± 1.00 behind the E line. The Chinese had a protrusive lower lip which was 1.66 mm ± 0.91 in advance of the E line. The Indian lips were 0.13 mm ± 0.99 which was almost on the E line. Although this measurement especially for Chinese would be unacceptable according to Ricketts standards, we
found these readings from normal adults with pleasing or acceptable profiles. This strengthens the viewpoint that facial pattern of Asians (e.g.: Chinese and Indians) is measurably different. What is not acceptable in the Caucasians might be normal in our racial group (Chan et al., 1972). NLA is the angle formed by a tangent to the base of the nose through subnasale and the superior vermilion border. This angle is essential in evaluating the anteroposterior relationship of the maxilla in relation to the profile. An acute nasiolabial angle indicates protrusion of the maxilla. In this study there was no significant difference in both races although the Indians had a more acute angle (98.60˚ ± 4.14) compared to the Chinese (102.10˚ ± 2.11). According to Brown and Mc Dowell (1951) ideally this angle should be 90˚-100˚ although they add even a nasolabial angle of 120˚ could be acceptable. Lo and Hunter (1982) recommended that facial balance could be improved by choosing a treatment approach that would increase the angle if it was small initially. There were doubts as to whether the angle can be influenced by orthodontic treatment alone (Young and Smith 1993) but orthognathic surgery combined with orthodontic would definitely be able to alter it. There was a significant difference in the lower lip angle. The angle in the Chinese was more obtuse (144.70˚ ± 1.71) and Indians had an acute (118.65˚ ± 3.93) angle. The Indians angle was almost similar to Caucasians standard which was (122˚ ± 11.7) given by Burstone (1958).
Nose prominence measurements Indians nose was significantly more prominent than the Chinese (p < 0.001)). This was verified by both the angular and linear measurements. This factor needs to be taken into consideration when attempting orthognathic surgery in the maxillary region, as it would influence the prominence of the nose.
Chin prominence In this category, only the measurement of chin tip was significantly (p < 0.001) forward in the Chinese (8.45 mm ± 3.70) compared to the Indians (0.07 mm ± 1.87). This was the measurement of the anteroposterior prominence of the combined size, position of lower jaw, chin and overlying soft tissue. This was the same with the observation by Woon (1982) who observed that the Chinese patients had a prognathic mandible hence a tendency for Class III profiles compared to the Indians. If we take a look at the measurement BNpog there was no statistically significant difference (p > 0.001) in both races. This shows that prominence of chin is due to the overlying soft tissue. The final variable which gives an indication about the height of the chin showed no significant difference in the height of the chin which was 38.95 mm ± 3.72 for Indians and for Chinese it was 37.69 mm ± 3.01.
Cephalometric Norms of Indian, Chinese and Caucasian Generally from the graph (Fig 2), the Indian norms followed the Caucasian norms (Riolo et al. 1974) more closely than the Chinese norms. The difference was more marked in points 2 and 3 that were SNA and SNB respectively. The Chinese had a higher figure than Indians or the Caucasians. There was also a difference in point 7, which was the measurement for LAFH. Here the Chinese had a lower measurement than Indians even with the males and females (Kathiravan et al., 2012) and Caucasians. The figures however for Indian and Caucasian were similar. There was a marked difference in the dental measurements especially in point 16 (UI/MxP), point 17 (LI/MnP) and point 18 (IIangle). The Chinese had a higher value for point 16 and 17 but lesser value for point 18. The Indians had a slightly lesser value in point 16 but higher values in point 17. The value in point 18 was however similar in Indians and Caucasians. The soft tissue measurements point 26 (LLA), nose prominence measurements point 27 (NT), point 28 (NA) and chin prominence measurement that was point 29 (CT) showed difference in all the three races. In point 26, the Chinese had the highest figure followed by Caucasian and the Indians had the lowest figure. In the nose prominence category represented by point 27 and 28, the Caucasians had the highest fig-
Cephalometric Comparison between Malaysian Indian and Chinese ure. The chin prominence point 29 (CT) showed some different trend. The Chinese had a higher value, followed by the Caucasian and lowest figure in Indians. All the other points were almost similar in the entire three racial groups.
CONCLUSION
The present study showed that there was significant difference in facial configuration when the Malaysian Indians and Chinese were compared. Differences were found in the skeletal, dental, soft tissue, nose and chin prominence measurements. The conclusions that could be drawn from this study are: 1. Malaysian Chinese maxilla and mandible is set more forward than the Indian maxilla and mandible. 2. Vertically there is more development in the posterior facial height for Malaysian Chinese whereas the Malaysian Indians have more development in the anterior facial height. 3. The Malaysian Chinese have bidental protrusion and more protrusive upper and lower lips. 4. The Malaysian Indians have a more prominent nose but the chin is more forward in the Malaysian Chinese.
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