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ORIGINAL ARTICLE
Year : 2022  |  Volume : 25  |  Issue : 4  |  Page : 541-547

Ricketts' E-line profile preferences among Nigerian orthodontists, orthodontic trainees, and a young undergraduate students' population


1 Department of Child Dental Health, Obafemi Awolowo University, Ile-Ife, Nigeria
2 Department of Preventive and Community Dentistry, Obafemi Awolowo University, Ile-Ife, Nigeria
3 Department of Preventive and Community Dentistry, Zohay Healthcare, Emmanuel's Place, Samonda, Ibadan, Nigeria

Date of Submission09-Oct-2021
Date of Acceptance30-Dec-2021
Date of Web Publication19-Apr-2022

Correspondence Address:
Dr. D Afolabi
Department of Preventive and Community Dentistry, Obafemi Awolowo University, Ile-Ife
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_1873_21

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   Abstract 


Aim: This study compared the perceptions of orthodontists, orthodontic trainees, and young university undergraduate students in Nigeria regarding facial profile attractiveness and the need for orthodontic treatment. Materials and Methods: We used a photo-editing software to alter the lips on Ricketts' esthetic line (E-line) in a lateral silhouette to produce five silhouette profiles with 2 mm incremental changes in the upper and lower lips from the 'normal' position on the E-line (-4 mm/-2 mm to + 4 mm/+6 mm). Two hundred and thirty-two participants (consisting of six groups) ranked the five profiles on a 5-point Likert scale (least attractive, 1 to most attractive, 5). Participants also assessed whether orthodontic treatment was needed to improve facial esthetics. Data were analysed in SPSS 20. Intra-rater reliability was assessed using Cohen's Kappa. We tested the null hypothesis (P ≤ 0.05) that ranked preferences between groups using the Kruskal-Wallis test. Mann-Whitney U test was also used to assess pairwise comparisons between the groups. Results: Intra-rater reliability for facial profiles and treatment needs were moderately acceptable (perceptions ≥67.7%; treatment needs ≥67.0%). Perceptions between orthodontists and orthodontic trainees were not significantly different. However, orthodontists/trainees tended to rank the 'normal' Ricketts' E-line profile as most attractive, while students preferred more protrusive lips. Participants' age rather than sex significantly influenced esthetic preferences. About one-half of all participants (46.6%) ranked the 'normal' Ricketts' E-line as unacceptable; hence required orthodontic treatment to improve their facial attractiveness. Conclusion: Clinical/professional judgment and age significantly influenced participants' perceptions of facial attractiveness. Most participants preferred slightly protrusive lips.

Keywords: E-line profile, Nigerian population, orthodontists and trainees, Ricketts' perceptions


How to cite this article:
Otuyemi O, Afolabi D, Oyewole T. Ricketts' E-line profile preferences among Nigerian orthodontists, orthodontic trainees, and a young undergraduate students' population. Niger J Clin Pract 2022;25:541-7

How to cite this URL:
Otuyemi O, Afolabi D, Oyewole T. Ricketts' E-line profile preferences among Nigerian orthodontists, orthodontic trainees, and a young undergraduate students' population. Niger J Clin Pract [serial online] 2022 [cited 2022 May 22];25:541-7. Available from: https://www.njcponline.com/text.asp?2022/25/4/541/343466




   Introduction Top


Orthodontists in recent times have placed greater emphasis on facial appearance, dental esthetics, and natural beauty.[1],[2],[3],[4] Clinical evidence and data from epidemiological studies also indicate that the perceptions of facial profile attractiveness and the need for orthodontic treatment have been a subject of interest among different racial and ethnic groups, cultures, and socio-demographics even though science and technology have tried to bridge the intercultural gap in today's modern society.[1],[5],[6],[7],[8],[9]

Many studies have documented that facial esthetics and harmony, and, in particular, the lip position is one of the key objectives of treatment and improvement in the quality of life among individuals seeking orthodontic care.[2],[3],[10],[11] The anteroposterior position of upper and lower lips and other dentofacial features are critical in evaluating individuals' natural facial esthetics. A study by Nomura et al.[1] on esthetic preferences of soft-tissue lip profiles ranked by four independent panels comprising European-Americans, Hispanic Americans, Japanese, and Africans, reported that the race and ethnicity of the judge, patient, and sex significantly influence laypersons' standards for lip profile esthetics.

The professional expert opinions in the field of orthodontics and how individuals evaluate themselves also influence perceptions of facial profile attractiveness and dental esthetics[1] Shaw et al.[12] and Prahl-Andersen[13] independently concluded that dental professionals are conditioned to be too critical about any deviation from the norm. However, most of the informed views are usually based on certain stereotyped rules, guidelines, norms, ideal proportional ratios, angles, and other human psychosocial behaviour.[9],[14]

Most studies evaluating the relationship between upper and lower lip positions to esthetic facial profile were conducted using Caucasian standards and values with very little or no reference to the African populations[15],[16] Zarif Najafi et al.[3] opined that proper understanding of the preferred lip position with regards to the individual's facial profile could facilitate treatment planning and the overall decision making to obtain the most attractive facial profile upon the completion of orthodontic treatment.

In one of the established facial esthetic standards, Ricketts[15],[17] described an imaginary line drawn from the nose (pronasale) to the chin (soft-tissue pogonion) and referred to it as the esthetic line or E-line. For an acceptable range, the upper and lower lips should lie behind the line by a mean distance of 4 mm and 2 mm, respectively.[11] Similarly, Hsu[14] compared five soft-tissue analytical reference lines, including the Ricketts' E-line, Holdaway's H-line, Steiner's S1-line, Burstone's B-line, and Sushner's S2-line in terms of consistency and sensitivity. The author reported that the E-line was very convenient and of great value to clinicians because of its anterior location.

Also, most of the studies on esthetic preferences were conducted among Caucasians of American and European origin[3],[15],[17] and a substantial report in the Mid-East[4],[8] and Asian races and ethnicities.[2],[9],[14] However, very little has been documented about the esthetic preferences in communities of African descent.[1],[7] This is more important as the facial profiles vary distinctly between Africans and other racial and ethnic groups.[18]

The purpose of this study was to evaluate and compare the perception of facial attractiveness of Nigerian orthodontists, resident orthodontists, and university undergraduate students, including their perceived need for orthodontic treatment in different facial profiles according to Ricketts' esthetic line (E-line) using lateral silhouettes. The hypothesis, therefore was that there were no differences in the perceptions and orthodontic treatment needs of the Ricketts' facial profiles among the study group.


   Methods Top


Ethical approval was sought and obtained from the Ethical and Research Committee with protocol no; IPH/OAU/12/1323. A non-probability sample of 232 Nigerians comprising of 30 orthodontists, 34 orthodontic trainees, 43 clinical dental students, 42 clinical medical students, 41 science students, and 42 art students were recruited in the study. The Nigerian orthodontic clinicians (orthodontists and orthodontic trainees) were drawn from the full, and associate membership register of the Nigerian Association of Orthodontists while the students were recruited from a Federal Public University in Nigeria. The inclusion criteria for the students were 18 years of age and above, no history of facial surgery or orthodontic treatment, and no facial deformities or trauma. Informed consent was obtained from all participants.

A lateral silhouette in the natural position of the head was constructed with the aid of a computer software (Adobe Photoshop CS version 8.0; 2017 Adobe Systems, San Jose, Calif) using the normalized values of the esthetic line (E-line) of Ricketts; an imaginary line that runs from the pronasale (tip of the nose) to the soft tissue pogonion (chin) with the upper and lower lips lying 4 mm and 2 mm respectively behind this line.[17] Other cephalometric parameters were constructed within the normal values of the Nigerian population.[11],[19]

The photo editing software was used to manipulate the lip positions of the constructed lateral silhouette. While maintaining the original facial convexity, the position of the lips was altered using the esthetic E-line as the reference point. The first silhouette image (profile A) was manipulated to produce four other images in 2 mm increments from the originally constructed profile for different lip protrusions (B, C, D, and E) [Figure 1].
Figure 1: Five silhouette profiles

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Before the assessment, the five silhouette profiles were shuffled to avoid stereotyping based on the progressive increase in the fullness of lip positions. Each of the silhouette profiles was later identified with alphanumeric codes; A1, B2, C3, D4, and E5 [Figure 2]. The shuffled silhouette profiles' template was further edited to remove the E-lines and codes before it was finally printed and mailed to the various respondents for assessment. [Figure 3]
Figure 2: Five shuffled silhouette profile

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Figure 3: Five unmarked shuffled silhouette profiles

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A questionnaire was also prepared to rank the five profiles by the respondents based on a Likert scale of 1 to 5: 1, very unattractive; 2, unattractive; 3, neither unattractive nor attractive; 4, attractive; 5, very attractive. Information on socio-demographic data such as age and sex were also sought in addition to the perceived need for orthodontic treatment of the lip positions for the five silhouettes as “yes” or “no” depending on their desirability to orthodontic treatment. This survey was administered via online software (SurveyMonkey, San Mateo, Calif) after the respondents had agreed to participate in the study. The silhouette profiles were mailed again to all the respondents for re-evaluation two weeks after the receipt of the initial assessment to determine the intra-rater reliability.

Statistical analysis

Data entry and analysis was done using SPSS software version 20. Cohen's Kappa was used to measure the intra-class reliability of facial profile perceptions and orthodontic treatment needs. The means and standard deviations for the rank scores were calculated for all facial profiles. Also, the means and standard deviations were calculated independently for each of the socio-demographic groups. The Kruskal-Wallis test was used to compare the rankings among the two professional and four student groups. The Mann-Whitney U test was used for pair-wise comparisons in the professional and student groups. The level of significance was set at P < 0.05.


   Results Top


Intra-class reliability of the entire population sample conducted two weeks after the initial evaluation using Kappa statistics ranged from 0.71–0.81 and 0.30–0.56 for the facial attractiveness scores and orthodontic treatment needs, respectively. The agreements were reasonably acceptable and were highly statistically significant for the groups (P < 0.001) [Table 1].
Table 1: Intra-class reliability of facial profile perceptions and orthodontic treatment needs

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The means and standard deviations of the facial profile ranked scores for sex, age-groups, professional, and student groups are shown in [Table 2]. No significant difference was found between male and female raters in the ranking of different facial profiles (P > 0.05). With regards to age-groups, middle-aged Nigerian adults ranked the 'normal' Ricketts' profile (profile A) (3.84 ± 1.36) ahead of the young and old adults with 2.56 ± 1.52 and 3.37 ± 1.80 respectively (P < 0.05). Similarly, the young adults ranked the slightly procumbent upper and lower lips (profile B) (4.25 ± 1.22) higher than the middle-aged (3.33 ± 1.66) or old adult groups (3.68 ± 1.16). The differences were statistically significant (P < 0.05). For the more procumbent facial profiles (profiles C, D, E), there were no statistically significant differences in the mean rank scores among the age groups (P < 0.05).
Table 2: Perceptions of different Ricketts' facial profiles according to sex and age groups

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For the comparison of facial profile perceptions among orthodontic professionals and student groups, the Kruskal-Wallis analysis test was used. For the 'normal' profile and slightly procumbent upper and lower lip profiles (profiles A and B), the orthodontic professionals ranked the facial attractiveness higher than all the student groups. These differences were statistically significant (P < 0.05). On the contrary, more protrusive upper and lower lip position (profile D) was rated as less attractive by the professional orthodontic groups. This was also statistically significant (P < 0.05). The extreme protrusive upper and lower lip positions (profiles C and E) were not fancied by all the groups as they were rated low. The differences were not statistically significant (P > 0.05) [Table 3].
Table 3: Perceptions of different Ricketts' facial profiles according to the specialist orthodontists, orthodontic trainees, and young university undergraduate students

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[Table 4] shows the pair-wise comparisons of perceptions of different participant groups according to Ricketts' facial profiles. Only the orthodontists versus orthodontic trainees and orthodontists versus dental students showed no significant differences across the different upper and lower lip profiles.
Table 4: Comparisons and P values of perceptions of different Ricketts' facial profiles according to the different orthodontic professionals and student groups

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When the participants were asked whether there was a need for orthodontic treatment in any of the upper and lower lip positions on a 'yes' or 'no' basis to improve the facial attractiveness, most respondents (76.7%) believed that the most extreme protrusive upper and lower lip position would require orthodontic treatment to improve their facial attractiveness. Also, the majority of the participants were satisfied with slightly protrusive upper and lower lips (profile B); hence required the least attention for orthodontic treatment with 24.1%. However, about one-half (46.6%) of the respondents reported that the 'normal' Ricketts' E-line profile needed orthodontic treatment for an improvement in facial attractiveness [Figure 4].
Figure 4: Stacked column showing the perceived orthodontic treatment needs for different Ricketts' facial profiles by the participants

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   Discussion Top


In our study, Ricketts' E-line was adopted as the appropriate reference plane which is routinely used for orthodontic diagnosis and treatment planning and is widely used in studies on esthetic preference.[1],[11],[14] Apart from this application, the Ricketts' E-line is convenient and of great value on the silhouettes due to the anterior location of its landmarks. The inclusion of details of nasal prominence on the E-line is another important facial characteristic found in different racial and ethnic groups.[1],[14]

The use of androgynous silhouette facial profiles constructed in black as against clinical photographs in this study eliminates any form of distractions such as the colour of the eyes, hairstyle, and even the skin complexion that could easily introduce bias, thereby affecting the outcome of the study. Alley and Cunningham[20] and Spyropoulos and Halazonetis[6] independently reported that all extrinsic and intrinsic factors, including atypical dimensions of facial features, have a profound influence on esthetic scores.

The initial hypothesis of this study was clearly rejected as differences were reported in the perceptions of facial profile attractiveness among the different professional and socio-demographic groups.

Based on the results of this study, the orthodontic professionals/clinicians, including the specialist and orthodontic trainees, preferred the original lip positions according to Ricketts' 'normal' E-line values as most attractive. On the contrary, young undergraduate university students tended to rank a slightly protrusive lip position as most attractive. This is expected, and the plausible explanation for this disparity may be due to differences in professional training and exposure to westernization; the specialist orthodontist or the orthodontic trainee is accustomed to the characteristic profile which is known for the Caucasian. Furthermore, the specialized training of both the specialist and orthodontic trainee allows them to pick out any profile that deviates from normal.[21] Orthodontic practitioners have been said to distinguish profile changes better because of their experience in observation and studies of several profiles during their careers.[21] Lines et al.[22] compared the judgments of orthodontists with other dental specialists and concluded that orthodontists were more critical in the assessment of facial esthetics. Similarly, Imani et al.[4] reported that orthodontists were able to make clear-cut choices on facial profiles. They also noted that specialist orthodontists were stricter and sharper for identifying favourable profiles compared with surgeons and laypersons.

Regarding the undergraduate students, it appears that their choice of facial attractiveness was largely driven by cultural and ethnic norms, as they tended to prefer protrusive lip positions. A cephalometric study of horizontal lip position in a typical adult Nigerian population reported by Isiekwe et al.[11] showed that both upper and lower lips were more protrusive (upper lip to E-line, 3.21 ± 2.69; lower lip to E-line, 6.76 ± 2.83) than the normative values of Ricketts' E-line. These findings signify a more protrusive natural lip position in the Nigerian population as compared to Caucasians. The general lip protrusion observed in the Nigerian study may be attributed to the protrusive dentoalveolar relationship associated with bimaxillary proclination, which has often been described as a feature of the African profile.[19]It is therefore not surprising that the young Nigerian university laypersons accept a slight soft-tissue lip fullness or prominence as against the Ricketts' norm. This is consistent with a previous report on facial profile perceptions among a group of Black South Africans, which showed that the population preferred exaggerated bimaxillary protrusive profiles with lip competence and normal overjet/overbite relationships.[7] Farrow et al.[23] had earlier surveyed the lateral profile photographs of African American patients and reported that mild convex profiles with greater protrusion were more acceptable. Even among facial profile judges of different racial backgrounds, Nomura et al.[1] showed that African judges preferred more protrusive profiles compared with either the Hispanic Americans or Japanese judges.

With modernization, breakdown in cultural barriers and disintegration of segregation, there is a preferential tendency towards fuller and more anteriorly positioned lips with more acute nasolabial angle among the general public.[24],[25]

Another possible influential factor in the choice of lip profile attractiveness is the relative positioning of other facial features. Czarnecki et al.[26] reported that the judgment of lip positions was dependent on the position of the chin and nose. They observed that more lip protrusive profile was acceptable by professionals irrespective of gender when either a large nose or a large chin was present. The authors however concluded that orthodontic treatment goals should be tailored to the attainment of balanced and harmonious facial features rather than a rigid adherence to standard average dental and skeletal parameters.

It is interesting to note that extreme protrusive lip positions were not favoured by any of the groups and therefore ranked very low by all the evaluators in this study. This clearly shows that there are limits of acceptability to soft tissue lip fullness or protrusion by the Nigerian population.

The results of study indicate no sex dimorphism in the esthetic preferences. This is consistent with other studies.[2],[3],[27] In contrast, Sushner[28] reported that though African American subjects preferred fuller lips than their white counterparts when assessing facial profile from facial photographs, the African American males preferred a more protrusive lower lip than their female counterparts with +2 mm and +1.1 mm respectively anterior to the E-line. Other authors[1],[22],[26] found sex-specific profiles and reported that retruded profiles were preferred by men. This, according to Nomura et al.[1] gives the desired impression of muscularity when the chin appears more prominent as the lips are positioned more posteriorly.

The young adults who are mainly undergraduate students in this study, though they constitute about three-quarters (73%) of the sample population, showed a preference for slightly protrusive upper and lower lips. Their preference may largely be induced by the societal norm of fuller or protruded profile seen in Africans. In addition, the generational trend towards procumbent lips as evidenced in contemporary fashion magazines and other social media, may have a great impact on their choices.[25] In contrast, the preference for normal Ricketts' E-line by middle and old-aged groups who are predominantly the orthodontic trainees and specialist orthodontists may have been conditioned by their training and career experiences. Our experience in this study was quite different from the Asian-Chinese, who appear to prefer flatter profiles. Chan et al.[29] reported that bimaxillary retruded profiles were more acceptable by Asian orthodontists than by dental students, though the difference was not significant.

Another factor that may influence lip profile perception is age-appropriate profile. Bishara et al.[30] studied the facial and dental changes in adulthood and reported the relative changes of lip position compared to chin and nose, which cause the lips to appear more retrusive at age 46 years than those at 25 years. This relative change may be an important reason why the middle and older age groups preferred a more retruded lip profile in our study. This age-appropriate profile was earlier explored by Shimomura et al.,[2] who reported that Japanese female patients over 30 years of age significantly preferred a more retruded lip position than those aged 15 to 19 and 20 to 29 years.

Facial esthetics is usually the main concern when individuals seek orthodontic treatment for upper and lower lip protrusion. Even though bimaxillary protrusion is a common malocclusion trait among Africans,[11],[18],[19] the extreme protrusion (upper lip +4 mm; lower lip +6 mm) was still judged as requiring orthodontic treatment by the majority of evaluators in this study. Surprisingly, the least percentage of evaluators that required orthodontic treatment as a necessity for improvement in their facial esthetics were found in the slightly protrusive lip profile (upper lip -2 mm; lower lip 0 mm). This emphasizes the need for racial/ethnic group-specific norms during orthodontic diagnosis and treatment planning.


   Conclusions Top


The following conclusions can be drawn from this study:

  1. The orthodontic clinicians comprising the specialist orthodontists and orthodontic trainees had the same perception of facial lip attractiveness, which was different from the students' group.
  2. The orthodontic clinicians preferred the normal lip positions as espoused by normal Ricketts' E-line as most attractive, while the young undergraduate students tended to prefer slightly protrusive lip positions.
  3. Though there was no sex-dimorphism, the older age groups found the retruded (normal Ricketts' E-line) lips more attractive than the younger age group.
  4. While a substantial number of participants judged the normal Ricketts' E-line as requiring orthodontic treatment, the extreme protrusive lips were adjudged to require orthodontic treatment by all the groups. Therefore, our initial hypothesis was rejected except for the gender difference.


Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Shimomura T, Loi H, Nakata S, Counts AL. Evaluation of well-balanced lip position by Japanese orthodontic patients. Am J Orthod Dentofacial Orthop 2011;139:e291-7.  Back to cited text no. 2
    
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Imani MM, Sanei E, Niaki EA, Shahroudi S. Am J Orthod Dentofacial Orthop 2018;154:412-20.  Back to cited text no. 4
    
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Hsu BS. Comparisons of the five analytic reference lines of the horizontal lip position: their consistency and sensitivity. Am J Orthod Dentofacial Orthop 1993;104:355-60.  Back to cited text no. 14
    
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Farrow AL, Zarrinnia K, Azizi K. Bimaxillary protrusion in Black American: An esthetic evaluation and the treatment considerations. Am J Orthod Dentofacial Orthop 1993;104:240-50.  Back to cited text no. 23
    
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Czarnecki ST, Nanda RS, Currier GF. Perceptions of a balanced facial profile. Am J Orthod Dentofacial Orthop 1993;104:180-7.  Back to cited text no. 26
    
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Modarai F, Donaldson JC, Naini FB. The influence of lower lip positon on the perceived attractiveness of chin prominence. Angle Orthod 2013;83:795-800.  Back to cited text no. 27
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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