https://orcid.org/0009-0009-8886-9301
ABSTRACT
Purpose
Modern orthodontics focus on achieving functional and aesthetically pleasing results. However, traditional cephalometric norms do not necessarily correspond to facial aesthetics, leading to unsatisfactory treatment outcomes. This study aimed to establish cephalometric treatment goals for each facial profile (concave, straight, and convex) by comparing the cephalometric variables of each type.
Materials and methods
The post-treatment lateral cephalograms of 180 orthodontic subjects (18–37 years old) were assessed. Profile silhouettes were scored for attractiveness by 15 Thai laypersons using a 5-point Likert scale. Cephalograms scoring above 3 were divided into the three facial profile groups (n = 60). Fifty-five cephalometric variables were measured, and the statistical analysis was performed using SPSS software.
Results
One-hundred and eighty aesthetically acceptable silhouettes comprised concave, straight, and convex facial profiles with a 1:1 male-to-female ratio. All types shared similarities in the cranial base and maxilla. The convex profiles more frequently displayed skeletal and dental base Class II, skeletal open bite, retruded and retroclined upper incisors, protruded and proclined lower incisors, obtuse nasolabial angles, protruded upper and lower lips, and retruded chins. The opposite findings were observed in the concave profiles. However, all profile types had similar upper and lower teeth relative to A point to pogonion line; and upper and lower lip positions relative to subnasale to soft tissue pogonion line and the true vertical line passing through soft tissue nasion.
Conclusion
Universal treatment goals for all profile types combined with customized values for each profile type to achieve an aesthetically acceptable facial profile are recommended.
KEYWORDS:
1. Introduction
Currently, the main objectives and limitations of orthodontic and orthognathic treatment are determined by the facial soft tissues, rather than by the teeth and craniofacial bones [Citation1,Citation2]. Soft tissue analyses have been performed by Downs [Citation3], Steiner [Citation4], Burstone [Citation5], Ricketts [Citation6], Holdaway [Citation7], and Merrifield [Citation8]. In these analyses, however, there are no established optimum parameters for an aesthetic facial profile, which may lead to treatment failure due to a lack of patient satisfaction with their appearance [Citation9].
A systematic review investigating the reasons why individuals seek orthodontic treatment found that the key motivational factor was to improve their facial aesthetics [Citation10]. Aesthetic perceptions and facial profile preference are influenced by various occupational backgrounds from laypeople to dental professionals [Citation9,Citation11], orthodontists, or oral surgeons [Citation12], and are shaped by sociodemographic factors, including age [Citation9,Citation13], race [Citation13–15], current standards [Citation9], sex [Citation9,Citation13], geographic area [Citation10], socioeconomic status [Citation10], education [Citation10,Citation11,Citation16], and the facial profile category of the evaluators [Citation9,Citation13,Citation17].
Because the traditional cephalometric norms were established based on a normal occlusion and the harmonious profile of the subjects judged by the authors of those studies, orthodontic and orthognathic treatment performed according to these cephalometric standards without considering the aesthetics from laypeople’s perspective may be inadequate to achieve the greatest patient satisfaction [Citation18]. Moreover, the cephalometric standards derived from normal faces may not be appropriate to use as a guideline for treating camouflage cases.
Therefore, in this study, the cephalometric values of orthodontically treated individuals with aesthetically acceptable facial profiles were investigated and compared between concave, straight, and convex profile groups to create cephalometric treatment goals for each facial profile type. These values will help improve modern orthodontic treatment planning towards better patient satisfaction with their facial aesthetics.
2. Materials and methods
This was a retrospective cross-sectional study. The protocol was approved by the Human Research Ethics Committee (#HREC-DCU2020-121 approved on 15/01/2021). Post-treatment lateral cephalometric radiographs of 18–37-year-old Thai citizens that completed orthodontic treatment from January 2007 until August 2020 at the orthodontic clinic were retrieved. The exclusion criteria comprised subjects with: (1) poor quality lateral cephalogram, (2) severe craniofacial disorders or craniofacial trauma, (3) previous history of orthognathic surgery or cosmetic surgery (rhinoplasty, lip surgery, or chin correction), (4) serious medical condition, or (5) mentalis strain.
The sample size estimation was determined by N4studies software version 1.4.1 (Thailand Research Fund and Prince of Songkla University, Thailand), using a standard deviation of 4 (Facial contour angle (FCA) from Sorathesn et al. [Citation19]), a mean error of 0.6, and an alpha level of 5%. Based on the calculation, 171 samples were divided into 6 groups, which were concave males, concave females, straight males, straight females, convex males, and convex females. Each group contained 28.5 samples and was rounded up to 30 samples per group.
To account for a drop-out rate of 65%, the required sample size for scoring was 300. The participants, comprising patients that had completed treatment at the Orthodontic Clinic, were selected using purposive sampling by 2 examiners.
Selection of lateral cephalograms with aesthetically acceptable profiles
The soft tissue profile outline was traced using Adobe Illustrator 2019 software (Adobe System Inc., San Jose, CA), and converted into a black silhouette with Adobe Photoshop CC 2019 by an examiner. The 300 prepared profile silhouettes were divided into six sessions. Only 50 silhouettes were scored per session to reduce fatigue [Citation20].
A panel of 17–40-year-old Thai laypersons, current patients at the Orthodontic Clinic, without craniofacial deformities was selected by purposive sampling. Each profile silhouette was presented to each rater for 5 sec using a Google survey online questionnaire (Google Forms, Google Workspace, Google LLC, CA, USA), without mentioning the subject’s sex or age [Citation21]. The scoring criteria of the attractiveness score (AS) for each silhouette profile (5-point Likert scale) [Citation21] are presented in .
Table 1. The scoring criterion of the attractiveness score for each silhouette profile (5-point likert scale) 21.
The average AS for each silhouette profile was collected from 15 raters, consisting of 5 persons for each profile type. The profiles with an average AS ≥ 3 points were considered aesthetically acceptable and then classified based on their original FCA. Subjects with an FCA 6–14° were classified as straight profiles, whereas those with an FCA < 6° and > 14° were categorized as concave and convex profiles, respectively [Citation17].
Cephalometric measurements
The cephalometric radiographs of the selected profile silhouettes were used for determining the cephalometric values. Each cephalogram was traced and the landmarks were identified by an examiner, who was trained and calibrated by an expert, via Adobe Illustrator 2019 software. To improve the landmark accuracy, the landmarks were confirmed by two experienced orthodontists. Any disagreement regarding landmark position was determined by discussion to reach a panel consensus. The cephalometric landmarks and measurements [Citation10,Citation19,Citation21–26] in the study were displayed in and . The cephalometric measurements were performed using Dolphin 3D software version 11.9 premium (Dolphin Imaging & Management Solutions, Chatsworth, CA, USA).
Figure 1. The cephalometric landmarks. 1. Nasion (N), 2. Sella (S), 3. Porion (po), 4. Orbitale (or), 5. Eye point, 6. Pterygomaxillary fissure (pt), 7. Basion (ba), 8. ANS, 9. PNS, 10. A point, 11. B point, 12. PM point, 13. Pogonion (pg), 14. Gnathion (gn), 15. Menton (me), 16. Gonion (go), 17. Articulare (ar), 18. Condylion (co), 19. Ramus point, 20. DC point, 21. R1 the deepest point on the curve of anterior ramus, 22. R2 the point on the posterior ramus, directly behind R1, 23. R3 the centre and most inferior aspect of sigmoid notch, 24. R4 lower border of mandible, directly inferior to R3, 25. Xi point, 26. U6 occlusal, 27. L6 occlusal, 28. U6 distal, 29. U4 cusp tip, 30. L4 cusp tip, 31. L1 tip, 32. L1 root, 33. U1 tip, 34. U1 root, 35. Soft tissue Glabella (G’), 36. Soft tissue Nasion (N’), 37. Pronasale (pn), 38. Columella (cm), 39. Subnasale (sn), 40. Soft tissue subspinale (SLS), 41. Upper lip (ls), 42. Stomion superius (stms), 43. Stomion inferius (stmi), 44. Lower lip (Li), 45. Mentolabial sulcus (ILS), 46. Soft tissue pogonion (pg’), 47. Soft tissue gnathion (gn’), 48. Soft tissue menton (me’), and 49. Throat point.
Figure 2. The skeletal cephalometric measurements. 1. Anterior cranial base length, 2. FH-SN, 3. SNA, 4. SNO, 5. A-NperpFH, 6. Co-A, 7. SNB, 8. Facial depth, 9. Pg-NperpFH, 10. Co-gn, 11. ANB, 12. Wits appraisal, 13. Convexity of point A, 14. SN-OP, 15. SN-GoGn, 16. SN-MP, 17. Mandibular arc, 18. FMA, 19. NSGn, 20. Lower face height, 21. LAFH, 22. UAFH/LAFH Ratio.
Figure 3. The dental cephalometric measurements. 23. U1-SN, 24. U1-PP, 25. U1-NA, 26. U1-NA, 27. U1-APg, 28. U1-APg, 29. IMPA, 30. FMIA, 31. L1-NB, 32. L1-NB, 33. L1-apg, 34. L1-apg, 35. Interincisal angle.
Figure 4. The soft tissue cephalometric measurements. 36. FCA, 37. NLA, 38. Upper NLA, 39. Lower NLA, 40. E-line to upper lip, 41. Upper lip prominence, 42. B-line to upper lip, 43. Ls to N’ V, 44. H-angle, 45. E-line to lower lip, 46. Lower lip prominence, 47. B-line to lower lip, 48. Li to N’ V, 49. Chin prominence, 50. Pg’ to N’ V, 51. Nose prominence, 52. UFH, 53. LFH, 54. TL, 55. LCTA.
Table 2. Definition of the cephalometric measurements [10,19,21–26].
Statistical analysis
Descriptive statistics were used to determine the mean and standard deviation (SD) for each parameter. The normality of the data was determined using the Shapiro-Wilk test. The differences in cephalometric values between the concave, straight, and convex groups were analysed using one-way ANOVA with multiple comparison Turkey post hoc tests. The differences in cephalometric values between males and females were analysed using the independent t-test. Kruskal-Wallis with Mann-Whitney U post hoc tests were performed for non-parametric variables. The intraclass correlation coefficient (ICC) was used to assess the intra- and inter-examiner reliabilities for cephalometric measurements. The statistical analyses were performed using the IBM SPSS version 22.0 for Mac (IBM, Chicago, IL, USA). The level of significance was set at 0.05.
Results
We selected 180 aesthetically acceptable silhouette profiles. Sixty subjects in each profile group consisted of 30 males and females. The AS of the three profiles were comparable in males (3.02 ± 0.33, 3.00 ± 0.41, and 3.00 ± 0.37 for straight, concave, and convex profiles, respectively). However, a straight profile (3.71 ± 0.24) was the most attractive, followed by concave (3.31 ± 0.36), and convex profiles (3.09 ± 0.36) in females.
The cephalometric comparison between profiles for each sex, and between sexes for each profile were presented in . The ICC for the intra- and inter-examiner reliabilities were 0998–1.000, indicating excellent correlation.
Table 3. Skeletal cephalometric values among the concave, straight, and convex profile groups.
Table 4. Dental cephalometric values among the concave, straight, and convex profile groups.
Table 5. Soft tissue cephalometric values among the concave, straight, and convex profile groups.
Comparing the profile types, the cranial bases were different (p < 0.05); FH-SN angle in the convex profile was the steepest. The A-P maxillary position variables were similar, except for the A-NperpFH in males. Moreover, almost all other cephalometric values in the A-P mandibular position, A-P skeletal maxillomandibular relationship, and vertical skeletal relationship were different (p < 0.05). The upper and lower teeth relative to A-Pg and the interincisal angle among the three profiles were similar, while other cephalometric values of the upper and lower teeth were different (p < 0.05). The upper and lower lip positions compared with the B-line and N’ V and Nose prominence were similar among the three profiles, while other soft tissue cephalometric values were different (p < 0.05).
Compared between sexes, the maxillary and mandibular length, and LAFH were different (p < 0.05), which was consistent with the soft tissue LFH among the three profiles. Other differences in the cephalometric values between males and females were shown in .
The predicted aesthetically facial profiles shown in and derived from selecting lateral cephalometric films with cephalometric values closest to the cephalometric means of male and female straight profile groups. Subsequently, the landmarks and outlines of each facial structure were adjusted to align with the cephalometric means of males and females in straight, concave and convex groups.
Figure 5. The predicted aesthetically facial profiles for males in the concave, straight, and convex groups.
Figure 6. The predicted aesthetically facial profiles for females in the concave, straight, and convex groups.
Discussion
This study determined the cephalometric values of orthodontically treated individuals with aesthetic facial profiles and created cephalometric treatment goals for the concave and convex profile groups. Although previous studies investigated cephalometric values [Citation21] or variables [Citation10,Citation22] that correlated with aesthetic profiles using laypeople’s [Citation10] or orthodontists’ opinions [Citation21,Citation22], they evaluated only normal profiles [Citation10,Citation21,Citation22]. There was insufficient data concerning the cephalometric values in the aesthetic concave and convex profiles, therefore, we sought explicit answers to this knowledge gap.
A silhouette profile, rather than a clinical photograph, was used to reduce perception bias from confounding factors, e.g. race recognition and stereotyping [Citation9,Citation12,Citation27]. Using a Likert scale (numerical rating scale) is concordant with using a visual analog scale [Citation28], but is simpler, more easily understood, used verbally with a simplified score, accepted by the participants, and requires no equipment or motor abilities. Although the same score by a different rater may not imply a similar aesthetic perception [Citation28], we provided specific criterion for each score to reduce potential discrepancies in the scores. Laypeople only were intentionally selected as the panel in our study to generalize the use of aesthetic treatment goals.
Comparing the cephalometric values of the straight group with previous studies, we found that the mandible was more protruded than the American and Chinese subjects [Citation22]. The A-P maxillomandibular relationship was similar to the American and Chinese subjects [Citation22]. The lower incisor angulation and inclination were similar to the American and Chinese subjects [Citation22]. The facial contour angle was straighter than the American, Chinese, and Iranian subjects [Citation10,Citation22]. The nasolabial angle was similar to the Chinese subjects, but more acute than the American and Iranian subjects [Citation10,Citation22]. The upper and lower lip positions were similar to the Chinese subjects, but more protruded than the American and Iranian subjects [Citation10,Citation22]. The nose and chin positions were more retruded than the American, Chinese, and Iranian subjects [Citation10,Citation22]. These differences support that the aesthetic perceptions and the cephalometric values associated with them differ between ethnicities.
There were specific cephalometric values that were important regarding the aesthetic profile of the concave and convex types in our study. The skeletal characteristics of the aesthetic profiles demonstrated similar maxillary length and position; however, there were differences in mandibular length and position for each profile type and sex. The only exception was the difference in A-NperpFH in males because a shorter anterior cranial base length and greater FH-SN angle causes a slightly protruded A-point in the convex profile. The vertical skeletal relationship revealed a similar ratio of UAFH/LAFH and an increasing openbite tendency in the concave, straight, and convex profiles. The patients with the maxillary length and position, and the lower face height values in our study tended to be more attractive than those who had a more retruded or protruded maxilla, and shorter or longer lower face height.
The upper teeth were more proclined and protruded in the concave profiles, whereas they were more retroclined and retruded in the convex profiles. In contrast, the lower teeth were more proclined and protruded in the convex profiles, but more retroclined and retruded in the concave profiles. Although the upper and lower teeth relative to A-Pg and interincisal angle of all profiles were similar, these values were different from some previous Thai norms based on a normal occlusion [Citation21,Citation24]. Therefore, the dental characteristics of an aesthetic profile in our study were associated with receiving dental compensation for each skeletal profile and dental base condition. Patients with concave and convex profiles that require greater compensation in the upper and lower incisors teeth can have an aesthetically acceptable profile. Moreover, males had more protrusion of the upper teeth and more proclination and protrusion of the lower teeth than females.
Concerning the soft tissue characteristics, NLA corresponded with the upper incisor inclination and position in each profile type. The upper and lower lips in the concave profiles were more retruded compared with E-line, but more protruded compared with Sn perpendicular to FH line. These were relative to the different reference lines in each analysis. Interestingly, all profile types had similar upper and lower lip positions related to B-line and N’V. Because the upper and lower lips are supported by the upper and lower incisors, and soft tissue Sn-Pg’ is supported by skeletal A-Pg, a similar incisor relationship relative to A-Pg could explain the similar upper and lower lip positions related to B-line. Moreover, although the upper and lower lips relative to Sn perpendicular to FH line in the convex profiles were more retruded compared with the concave profiles, a more retruded N point in a convex profile could result in similar upper and lower lip positions related to N’V.
Other findings, including protruded chin position, prominent nose, reduced upper facial height, and longer throat length tendencies were identified in the concave profiles. In contrast, the opposite soft tissue findings were present in the convex profiles. Therefore, the patients with acceptable aesthetic concave and convex profiles have a greater compensation tendency in their soft tissue profile.
Clinical application
There are recommendations for treatment planning, especially for camouflage cases. Although the cephalometric values in our study were not within the normal values relative to previous studies [Citation10,Citation19,Citation21–26] the patients with skeletal cephalometric values in the range we found were rated attractive regardless of profile type or sex. Therefore, the skeletal values did not need to be corrected.
Because the upper and lower incisor position and inclination related to A-Pg and the upper and lower lip relative to B-line and N’V were similar for all profile types and sexes, they can be used as universal treatment goals to achieve an aesthetically acceptable profile. Other variables that were different among the profile types can be used to customize flexible treatment goal values for each profile type rather than the previous norms [Citation10,Citation19,Citation21–26], which were based only on a straight profile.
From our study, we can generate both universal treatment goal values and customized values to provide an appropriate treatment plan for a straight profile type, but also for convex, and concave profiles. However, the present cephalometric values of acceptable profiles were investigated only in the rest position; thus, they may or may not be perceived as aesthetically acceptable in posed smiles. Moreover, the specific cephalometric treatment targets may not be fully achieved because the alveolar bone housing the upper and lower incisors can limit tooth movement. Therefore, further studies should assess other aesthetically perceived factors, such as posed smile aesthetics.
Conclusion
Patients with straight, concave, and convex profiles seek orthodontic treatment. To provide them with the best aesthetic outcome, a single set of cephalometric values cannot be applied to all profile types. Therefore, we recommend universal treatment goals for all profile types combined with customized values for each profile type to achieve an aesthetically acceptable facial profile. In the present study, different cephalometric components for each profile (concave, straight, and convex) were determined to guide modern orthodontic treatment approaches based on soft tissue paradigms.
Author contributions
Author 1 contributed to conception, design, data acquisition and interpretation, performed all statistical analyses, and drafted the manuscript.
Author 2 contributed to conception, design, data acquisition and interpretation, and critically revised the manuscript.
Author 3 contributed to data acquisition and interpretation, and critically revised the manuscript.
Ethical approval
The study protocol was approved by the Human Research Ethics Committee of Faculty of Dentistry, Chulalongkorn University [#HREC-DCU2020-121].
Acknowledgments
We thank our staff and the orthodontic patients for the attractiveness score ratings. Furthermore, we express our gratitude to Assist. Prof. Dr. Soranun Chantarangsu for statistical advice and to Dr. Kevin Tompkins for revising the language of the manuscript.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Funding
References
- Ackerman J, Proffit W, Sarver D. The emerging soft tissue paradigm in orthodontic diagnosis and treatment planning. Clin Orthod Res. 1999;2:49–52. doi: 10.1111/ocr.1999.2.2.49
- Proffit WR, Field HW, Saver DM, et al. Contemporary orthodontics. fifth ed. St Louis: Mosby; 2013.
- Downs WB. Analysis of the dentofacial profile. Angle Orthod. 1956;26(4):191–212.
- Steiner CC. The use of cephalometrics as an aid to planning and assessing orthodontic treatment: report of a case. Am J Orthod. 1960;46(10):721–35. doi: 10.1016/0002-9416(60)90145-7
- Burstone CJ. Lip posture and its significance in treatment planning. Am J Orthod. 1967;53(4):262–84. doi: 10.1016/0002-9416(67)90022-X
- Ricketts RM. Planning treatment on the basis of the facial pattern and an estimate of its growth. Angle Orthod. 1957;27(1):14–37.
- Holdaway RA. A soft-tissue cephalometric analysis and its use in orthodontic treatment planning. Part I. Am J Orthod. 1983;84(1):1–28. doi: 10.1016/0002-9416(83)90144-6
- Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. Am J Orthod. 1966;52(11):804–22. doi: 10.1016/0002-9416(66)90250-8
- Buranaprasertsuk P, Tangjit N, Boonpratham S, et al. Agreement on facial profile characteristics between orthodontic patients and orthodontists. M Dent J. 2019;39(3):257–265.
- Ghorbanyjavadpour F, Rakhshan V. Factors associated with the beauty of soft-tissue profile. Am J Orthod Dentofacial Orthop. 2019;155(6):832–43. doi: 10.1016/j.ajodo.2018.07.020
- Abu Arqoub SH, Al-Khateeb SN. Perception of facial profile attractiveness of different antero-posterior and vertical proportions. Eur J Orthod. 2011;33(1):103–11. doi: 10.1093/ejo/cjq028
- Soh J, Chew MT, Wong HB. Professional assessment of facial profile attractiveness. Am J Orthod Dentofacial Orthop. 2005;128(2):201–5. doi: 10.1016/j.ajodo.2004.07.041
- Bronfman CN, Janson G, Pinzan A, et al. Cephalometric norms and esthetic profile preference for the Japanese: a systematic review. Dental Press J Orthod. 2015;20(6):43–51. doi: 10.1590/2177-6709.20.6.043-051.oar
- Hall D, Taylor RW, Jacobson A, et al. The perception of optimal profile in African Americans versus white Americans as assessed by orthodontists and the lay public. Am J Orthod Dentofacial Orthop. 2000;118(5):514–25. doi: 10.1067/mod.2000.109102
- Nomura M, Motegi E, Hatch JP, et al. Esthetic preferences of European American, Hispanic American, Japanese, and African judges for soft-tissue profiles. Am J Orthod Dentofacial Orthop. 2009;135(4 Suppl):S87–95. doi: 10.1016/j.ajodo.2008.02.019
- Imani MM, Sanei E, Niaki EA, et al. Esthetic preferences of orthodontists, oral surgeons, and laypersons for Persian facial profiles. Am J Orthod Dentofacial Orthop. 2018;154(3):412–20. doi: 10.1016/j.ajodo.2017.11.040
- Suphatheerawatr T, Chamnannidiadha N. Esthetic perception of facial profile contour in patients with different facial profiles. J World Fed Orthod. 2019;8(3):112–117. doi: 10.1016/j.ejwf.2019.04.002
- Songkongka P How to identify soft tissue profile for orthodontic diagnosis: the graduate school, Prince of Songkla University; 2017.
- Sorathesn K. Craniofacial norm for Thai in combined orthodontic surgical procedure. J Dent Assoc Thai. 1988;1(2):190–201.
- Ko L, Rana J, Burgin S. Teaching & learning tips 5: making lectures more “active”. Int J Dermatology. 2017;57(3):351–354. doi: 10.1111/ijd.13701
- Sutthiprapaporn P, Manosupradit A, Pisek A, et al. Establishing esthetic lateral cephalometric values for Thai adults after orthodontic treatment. Khon Kaen Dent J. 2020;23(2):31–41.
- Oh HS, Korn EL, Zhang X, et al. Correlations between cephalometric and photographic measurements of facial attractiveness in Chinese and US patients after orthodontic treatment. Am J Orthod Dentofacial Orthop. 2009;136(6):762.e1–763. doi: 10.1016/j.ajodo.2009.04.020
- Suchato W, Chaiwat J. Cephalometric evaluation of the dentofacial complex of Thai adults. J Dent Assoc Thai. 1984;34(5):233–43.
- Dechunakorn S, Chaiwat J, Sawaengkit P, et al. Thai adult norms in various lateral cephalometric analyses. J Dent Assoc Thai. 1994;44(5–6):202–214.
- Chaiworawitkul M. Cephalometric norms of northern thais. J Dent Assoc Thai. 2008;7:1–7.
- Nuntasukkasame A Thai adult norms in lateral cephalometric analysis based on natural head position: Prince of Songkla University; 2012.
- Jarungidanan P, Sorathesn K. Acceptable facial profiles in Thai non-straight profile patients. CU Dent J. 2008;31:235–248.
- Rosas S, Paço M, Lemos C, et al. Comparison between the visual analog scale and the numerical rating scale in the perception of esthetics and pain. Int Orthod. 2017 Dec;15(4):543–560. doi: 10.1016/j.ortho.2017.09.027