Hayder Abdullah Hashim, BDS, MSc
Division of Orthodontics Department of Preventive Dental Sciences College of Dentistry, King Saud University P.O. Box 60169, Riyadh 11545, KSA
 

The soft tissue relationship was studied in 25 Saudi female dental students who satisfyied the criteria of a pleasing face and the age range of 20 to 25 years.  Cephalometric radiographs were taken for all subjects and traced. Eight soft tissue variables were studied in addition to five skeletal and five dental variables.  Student's t-test and descriptive statistics were used for data analysis.  The results showed that there were racial differences between the Saudi study and studies on other racial groups done by some researchers.  Saudi females demonstrated retrusive upper and lower lips in relation to the aesthetic line and an increased upper lip length when compared to the American black and white females, respectively.  Also the Saudi female had a thinner upper lip and an increased lower lip length compared to the British females.  Further, Saudi females possess a straight profile and a nasiolabial angle similar to the white American females, whereas the black American females have a convex profile and an acute nasiolabial angle. The cephalometric values obtained will be of great value not only in diagnosis and treatment plan of conventional cases but also in surgical cases and as a basis for future related studies.

Facial esthetics is considered as one of the main goals of orthodontic treatment and increased emphasis has been placed on it in recent years by both patients and orthodontists.1 The soft tissue profile has also been studied extensively in orthodontics, primarily from lateral cephalometric radiograph, under the assumption that the form of the soft tissue outline largely determines the esthetics of the whole face.2

The environment of the teeth and alveolar bone is subjected to different forces and pressures, primarily from muscular function, which in part determine tooth position.3

Soft tissue analysis plays an important role in orthodontic diagnosis and treatment planning.4 Changes in appearance that are pleasing to all concerned are brought about by correction of malocclusion.  It should, however, be determined beforehand that the proposed orthodontic treatment will not result in adverse facial change.

Few cephalometric studies have been carried out so far in Saudi population.  Shalhoub et al.5 in 1987 did a study among Saudi males and females with an age range from 20 to 46 years.  He compared his results to American data and found that the Saudi subjects had more protrusive maxilla, bimaxillary protrusion of the incisors and reduced overbite. When the results were compared to these of North American, the Saudis demonstrated an obtuse nasolabial angle and a reduced upper lip length. 

Sarhan and Nashashibi6 also did a study on 50 Saudi male children aged 9 to 12 years.  They found that the Saudi children had slightly prognathic face, protrusive upper and lower incisors, and low gonial and saddle angles when compared to a British sample with the same age range.  Further, Nashashibi et al.7 compared the cephalometric measurements of Saudi males to the Steiner measurements.  They found differences in the skeletal and dental measurements between the Saudi males and American males.  The Saudi males showed more protrusive maxilla and bimaxillary incisors protrusion. However, no soft tissue variables were investigated.          

Very few studies have so far been reported on Saudi Population on orthodontic soft tissue evaluation.  Therefore, the intention of the present study was to study the soft tissue relationship among Saudi female dental students and to compare the results obtained to those of previously published studies. 5,11

Lateral cephalometric radiographs were taken of twenty-five Saudi female dental students aged from 20 to 25 years who satisfied the following criteria: pleasing face, balanced facial profile, competent lips, and normal overjet and overbite relationship.8  Each subject selected had a normal dental relationship (Class I molar) without any severe anteroposterior, vertical or transverse discrepancies and with no history of orthodontic treatment.

Method

The selected subject was seated in a chair with the head in a natural position. The radiograph was taken with the teeth in centric occlusion and the lips at rest.

Each radiograph was hand-traced on an acetate paper by one person. Linear and angular measurements were done to the nearest 0.5-millimeter and degree, respectively. The magnification factor was found to be 0.9. All linear measures were corrected for magnifications.

Lip Measurements

These were done according to the method of Mamandras.9

Upper Lip Length. The perpendicular distance from the most inferior point of the maxillary vermilion border to the palatal plane.

Upper Lip Thickness.  The perpendicular distance between the two vertical and parallel planes drawn at 800 to S-N plane and passing through points subspinale and soft tissue A point.

Lower Lip Length. The perpendicular distance from the most superior point of the mandibular vermilion border to the mandibular plane.

Lower Lip Thickness. The perpendicular distance between two vertical and parallel planes drawn at 800 to S-N plane and passing through point B and soft tissue B point. 

Error of the Method: The error method of the skeletal, dental and soft tissue cephalometric measurements used in the present study was calculated by means of double determination.10 Ten randomly selected cephalographs were traced.  All landmarks and measurements used were retraced and measured after one week interval.  Dahlberg's formula10 was used for the calculation of the measurement error (M.E.).

Statistical Analysis

The data were subjected to statistical tests utilizing the (SPSS) package. Student's t-test was used for comparison between the present results and previously published studies. A level of significance of 5% was used.

Table 1 shows the error of the method.  The results of the measurement errors revealed that the highest error was found to be in the determination of the interincisal angle (1.01) and the lowest in determination of the upper lip thickness and lower incisor in relation to the NB line (0.00). Table 2 shows the mean and the standard deviation for each measurement included in the study.

The purpose of the present study was to present soft tissue cephalometric relationship for  Saudi female dental students, which should be of great value in orthodontic diagnosis and treatment planning.

The importance of studying growth of the lips for orthodontic treatment and prognosis has been a subject of much discussion.5-8,11

When the results of the present study were compared to a study carried out among 25 black American and 25 white American females,12 significant differences were found. The Saudi females were found to have a shorter lower lip (44.1mm) when compared to the white (47.1mm) and black (49.5mm) American females. They also had an increased upper lip length (26.5mm) compared to the white American females (21.5mm). On the other hand, both Saudi females and black American females demonstrated a similar upper lip length (26.5mm) whereas the white American females had a short upper lip length (21.5mm). The black American females also demonstrated an acute nasiolabial angle of 77.1 degrees. This indicated that the black American females possessed a protrusive maxilla unlike the Saudi females (SNA 79 degrees). This variation in the comparison was attributed to the racial difference between the Saudi females (Cuacasiod) and the black American females (Negroid).

The results of the present study were also compared to a study carried out among adult Saudi females by Shalhoub et al.5 with the similar criteria of selection and sample size except in the age range. The result of the current investigation showed a low mean value for the lower lip length (44.1mm) and the nasolabial angle (96.6 degrees) and high mean value for the upper lip length (26.5mm) compared to Shalhoub et al.5  (48.9mm, 104.5 degrees and 21.5mm, respectively). No significant difference was noticed in the lower lip thickness and the upper lip length between the Saudi females (11.6mm and 26.5mm) and the British females (11.8mm and 27.0mm), respect-ively. Also no significant difference was observed for the upper lip length between the Saudi females (26.5mm) and black American females (26.3mm). 

The result indicated that Saudi females studied have straight profile (angle of convexity NAPog Table 2). Holdaway13 stated that the convexity is directly interrelated to harmonious lip positions and, therefore, had a bearing on the dental relationships needed to produce harmony of the features of the human face.  He mentioned further that the observations indicated that as skeletal convexity increases so also does the convexity of the soft tissue profile, if the entire facial complex is to be one of balance and harmony with its type. Therefore, the angle of convexity obtained in the present study indicated that the Saudi females of the study sample had a harmonious face.           

The nasal projection of the females remained virtually constant from age 12 to 17 years.14 Thus, the relationship of both upper and lower lip to the esthetic line in the present study was found to be in a retrusive position. This could be explained by the fact that the majority of the Saudi females in this sample had slightly prominent nose and chin. This was confirmed by the fact that the angle SNPOg does not follow the SNB angle and also during clinical examination, a prominent nose was observed in the majority of the participants. This observation should make the clinician aware of the relationship of the nose in achieving the most esthetic orthodontic or orthognathic result and treatment decision for a non-extraction borderline case having a prominent nose.13 The prominence of the nose and chin affect this measurement, as do the underlying teeth and skeleton.15   

It became obvious from the available literature data that the hard and soft tissue relationship of the Saudi females differ from the white standards. Therefore, it can be concluded with caution that the results of the present study demonstrated areas of differences, which may help to correct the inappropriateness of using white norms. The results of the soft tissue relationship obtained could also be of great help to the orthodontist not only in the diagnosis of conventional and surgical cases, but also in serving as a basis for future studies when a large sample and more soft tissue variables are included.

It may be concluded from this data that the studied Saudi females

1. Demonstrated retrusive upper and lower lips in relation to the esthetic line.
2. Had a similar and an increased upper lip length when compared to the black and white American females, respectively.
3. Had a thinner upper lip and an increased lower lip length when compared to the British females.
4. Possessed a straight profile and a nasiolabial angle similar to the white norm.