An evaluation of preferred lip positions according to different age groups

Abstract

The purpose of this study was to compare preferred facial profiles rated by different age groups. An average profile of each gender was constructed from subjects with normal occlusions. Each average profile was located in the centre, and then the lips were protruded or retruded in six 1 mm increments in each direction. 70 lay people were divided into 3 groups: young adult (20-39 years); middle-aged (40-54 years); and senior (55-70 years). They were asked to rank their 3 most preferred profiles for each gender. The distribution of the most pleasing profile was compared according to age groups by the Kruskal-Wallis test and according to the rater’s gender by the Mann-Whitney U -test. There was a significant difference between the three age groups regarding the preferred male and female profiles ( P < 0.001). Both the middle-aged and the senior groups tended to select a slightly more retruded lip/flat profile than the young adult group. There was no gender dimorphism in the selection of the preferred profile. The young adult group preferred the straight profile while the middle-aged and senior groups favoured the slightly retruded profile. This may provide useful information for treatment planning in orthodontics and orthognathic surgery.

Since achievement of functional occlusion with harmonized and improved aesthetic profile has been a treatment goal of orthodontics and orthognathic surgery, many studies have been conducted on the ideal relationship between soft and hard tissues. Increasing numbers of patients are seeking treatment to improve facial attractiveness, which improves their quality of life.

Aesthetic standards are subjective and may vary over time. Studies have produced divergent results depending on the region, culture, gender, age, and ethnic background of the participants. A previous study showed a significant difference in facial profile preferences according to residency but not according to gender, suggesting a larger role for culture than for gender. Maple et al. demonstrated that clinicians should develop patient-centred treatment goals through awareness of the facial attractiveness standards of their society.

Owing to the increased numbers of middle-aged and senior patients seeking improvement of their facial profile, age-specific aesthetic standards might be necessary to fulfill this demand. Significant differences have also been found between parents and their children regarding dental attractiveness indicating a gap in perception of aesthetic standards between generations.

Previous research has evaluated whether age affected profile preference. Some studies showed no significant relevance to age. In contrast, other studies have demonstrated different preferences between adults and adolescents. This inconsistency is likely to be attributable to differences in research methodology including the way the facial profiles were presented, and the comparatively small sample size of the young adult groups. Also, middle-aged and senior groups were not included in these studies. Few studies have included the preferences of middle-aged and senior groups. None of these articles have provided procedures for producing silhouettes.

The purpose of this study was to evaluate the range of preferred facial profiles rated by young adult, middle-aged, and senior groups from a series of various lip positions in facial silhouettes.

Materials and methods

To develop an average profile silhouette for evaluation of soft tissue profile preferences, 20 Korean dental students (10 males, average age 25.3 years; 10 females, average age 23.3 years) with normal occlusion were recruited from a dental school. The inclusion criteria were no skeletal discrepancy of the maxilla and mandible, Class I canine and molar relationship, only slight or no crowding, full permanent dentition (except for the third molar), no excessively restored teeth, and no history of orthodontic treatment. Cephalometric radiographs were taken for each subject with the head in the natural position and lips relaxed for maximum intercuspation.

In order to determine the average facial profile configuration for soft tissue tracing, V-Ceph™ (Ver. 5.5, Cybermed, Seoul, Korea) was used by a single operator (NSP) to take the following measurements ( Fig. 1 ). First, the true vertical line (TVL) to the upper lip (UL); the shortest distance from the TVL which vertically passes through the subnasale to the upper lip. Second, the true vertical line (TVL) to the lower lip (LL); the shortest distance from the TVL which vertically passes through the subnasale to the lower lip. Third, the true vertical line (TVL) to the soft tissue pogonion (Pg′); the shortest distance from the TVL which vertically passes through the subnasale to the soft tissue pogonion. Fourth, the E-line to the UL; the shortest distance from the upper lip to the line that connects the pronasale and the soft tissue pogonion. Fifth, the E-line to the LL; the shortest distance from the lower lip to the line that connects the pronasale and the soft tissue pogonion. Sixth, the nasolabial angle; the angle made by the colummella–subnasale–labrale superious.

Fig. 1
Soft tissue analyses. 1, true vertical line to UL; 2, true vertical line to LL; 3, true vertical line to Pg′; 4, E-line to UL; 5, E-line to LL; 6, nasolabial angle. Structures positioned posterior to the true vertical line and E-line are indicated by negative values (−), and those positioned anterior by positive values (+).

These values were evaluated by the degree of deviation from the aesthetic standards of Koreans obtained from previous studies. The six measurements in each profile were assigned a grade. Five points if it was within one standard deviation; 4 points within two standard deviations; 3 points within three standard deviations; 2 points within four standard deviations; and one point within five standard deviations. The three profiles with the highest cumulative scores were identified for males and females, independently. The one male and one female with the most aesthetic facial profile were selected by consensus of three faculty orthodontists (aged 37, 39 and 51 years). The facial profile silhouettes were created.

Two sets of 13 silhouettes each were created by placing the average male and female silhouette in the centre and shifting the upper and lower lips in increments of 1 mm to the anterior and posterior, parallel to the Frankfort horizontal (FH) plane. Thus, silhouette 7 was the average silhouette, silhouette 1 exhibited the most retruded lip position, and silhouette 13 exhibited the most protruded lip position ( Fig. 2 ).

Fig. 2
A series of the 13 silhouettes for males and females.

As shown in Table 1 , these profile silhouette sets were assessed in 2010 by three groups of 70 Korean raters: a young adult group (20–39 years), a middle-aged group (40–54 years), and a senior group (55–70 years). The raters in each group were asked to select the three profile silhouettes they preferred the most for each gender via a questionnaire and to rank them in order of preference. The differences in the preferred profile were evaluated between the three groups. For the three most-preferred male and female silhouettes selected by each group, four linear and one angular measurements were performed: upper and lower lip to TVL, and E-line, and nasolabial angle.

Table 1
Number, gender, and mean age of raters in three age groups.
Group N Gender (M/F) Mean age (range) P -value
Young adult 70 35/35 26 y 7 m (20–39 y)
Middle-aged 70 35/35 47 y 5 m (40–54 y) <0.001
Senior 70 35/35 62 y 2 m (55–70 y)

One-way ANOVA.

Statistical analysis

Statistical evaluation was performed by SPSS 16.0 (SPSS Inc., Chicago, IL, USA). One-way ANOVA was performed to assess the differences in the average age between the three groups. The distribution of the most pleasing profile was compared according to the rater’s gender by the Mann–Whitney U -test and according to age groups by the Kruskal–Wallis test followed by multiple comparison with Bonferroni’s correction. The difference in distribution of preferences between male and female profiles was assessed by Wilcoxon signed ranks test. For confirmation purposes and to decrease the effect of non-selected profiles, each two successive silhouettes were combined into one, with the exception of silhouette 7. Then the same statistical analyses were performed. Statistical significance was determined at P < 0.05.

Results

The three age groups showed a significant difference in their preferred facial profiles for both male and female silhouettes ( P < 0.001). The male profile most favoured by young adults was 7, by middle-aged people 4, and by seniors 1, 3, and 4 equally. The female profile most favoured by young adults was 7, by middle-aged people 5, and by seniors 1 and 3 equally.

The distribution of most selected male and female profiles by the young adult group were significantly different from both the middle-aged and senior groups. No significant difference was shown between the middle-aged and the senior groups in rating the male and female profiles ( P = 0.69 and 0.51, respectively) ( Table 2 ). Table 3 shows the facial measurements of the most selected male and female profiles by each age group.

Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on An evaluation of preferred lip positions according to different age groups
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