Introduction
Improvement in facial and dental esthetics is a motivator for orthodontic treatment. An update in the preferences of clinicians and patients is necessary because beauty standards are constantly evolving and extraction and nonextraction decisions impact soft tissue and incisor position. This study aimed to update facial profile and incisor inclination preferences among orthodontists (ORs), general dentists (GPs), and laypeople (LPs) and correlate these preferences with objective soft tissue and incisor changes.
Methods
This retrospective study used discriminant analysis to identify 30 borderline patients with Class I and mild Class II treated with extractions and 30 treated with nonextraction. Assessment of profile and incisor inclination was performed by 90 LPs, 40 ORs, and 40 GPs using a 200 mm visual analog scale and rankings on a web-based survey. The degree of preference between the profile esthetics and incisor inclination was compared using the Cohen d value for standardized mean difference.
Results
Survey results indicated ORs’ preference for extraction profiles (mean difference = 5.52 mm; 95% confidence interval = 1.64-9.40), GPs’ preference for nonextraction profiles (mean difference = 3.67 mm; 95% confidence interval = 0.43-6.92), and all groups showing a stronger preference for more upright incisors. LPs’ preferences are more aligned with GPs.
Conclusions
GPs preferred protrusive lips and acute nasolabial angles (typical in nonextraction treatment), while strongly preferring upright incisors (typical in extraction treatment). These discrepancies in preferences highlight the importance of communication of treatment objectives and expectations among ORs, LPs, and GPs.
Highlights
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Extraction and nonextraction decisions impact soft tissue and incisor position.
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Clinician and patient profile preferences require an update as beauty standards evolve.
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Orthodontists prefer extraction profiles, whereas general dentists prefer nonextraction profiles.
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Laypeople’s preferences are more aligned with general dentists.
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Preference differences highlight the need to comunicate treatment objectives and expectations.
Facial and dental esthetics significantly influence psychosocial well-being, and improvement in these areas serves as a primary motivational factor for patients pursuing orthodontic treatment. The decision to extract or not affects both soft tissue and teeth position. Retraction of lips and incisors has been documented with extraction treatment. , There is also a correlation between the amount of incisor retraction and lip retraction in extraction patients. ,,,,
The literature shows a preference among orthodontists (ORs), general dentists (GPs), and laypeople (LPs) for extraction profiles over nonextraction profiles, especially in patients with increased initial lip protrusion. , Additionally, research into dental esthetics reveals that LPs prefer more upright incisors compared with ORs. The study of esthetics is multifaceted, with its complexity reflecting the continually evolving nature of beauty standards and preferences. In more recent years, there appears to be a trend toward fuller and more protrusive lips as seen by the increase in noninvasive cosmetic lip augmentation procedures, with the American Society of Plastic Surgeons reporting 1,439,291 such procedures performed in the United States in 2023, a 4% increase from the previous year alone. Historical comparisons by Berneburg et al, Yehezkel and Turley, and Sutter and Turley also reveal a trend toward fuller lips over the decades, as observed in fashion models in the 1940s compared with those from the 1990s and late 2000s.
Criticism has been directed at the evidence comparing extraction and nonextraction treatment outcomes, highlighting the need for studies involving borderline cases—patients with similar dental and facial attributes at the outset, in whom comparable treatment outcomes can be achieved when treated with either extraction or nonextraction modalities. ,,
Given the changing esthetic preferences over time, this study aims to update the understanding of facial and dental preferences in borderline extraction and nonextraction patients, and to compare these preferences to those reported in the earlier literature ,, (ie, studies published 15 years ago or older). To our knowledge, no other study has examined facial profile and incisor inclination preferences simultaneously.
Material and methods
This retrospective cohort study was approved by the University of Toronto Health Science Research Ethics Board (RIS Human Protocol Number 43230). The records of all patients treated at the graduate orthodontic clinic, University of Toronto, between January 2009 and February 2020 were reviewed. The inclusion criteria included patients with full permanent dentition and Angle Class I and mild Class II dental relationship (up to end-on or half cusp Class II molar relationship). Only patients with full records (pretreatment and posttreatment cephalometric radiographs, study models, and photographs) were considered. For the extraction group, patients treated with the extraction of 4 premolars (all first premolars or maxillary first premolars and mandibular second premolars) were included. Regarding treatment mechanics in the extraction patients and according to patients’ charts, after crowding was addressed by the retraction of the anterior teeth, the implemented biomechanics aimed at closure of the remaining spaces by protraction of the posterior teeth. Patients with congenitally missing teeth other than third molars, early termination of treatment because of noncompliance, craniofacial anomalies or syndromes, and patients treated with the extraction of teeth other than the above extraction patterns were excluded.
There were 204 patients fitting the above inclusion criteria (120 females and 84 males; 139 nonextraction and 65 extraction patients). Discriminant analysis, a method previously validated by cephalometric and geometric morphometric analysis, was applied to this sample to detect 2 groups of similar cephalometric values and hard and soft tissue shape. , These groups made up the borderline sample. Thirty-eight cephalometric and 8 model measurements obtained from the original treating resident, age, and whether the patient was treated with or without extractions were the variables input into the analysis using SPSS (version 29.0.1.0; SPSS Inc, Chicago, Ill) in a stepwise fashion. The original treating residents’ measurements were validated by 3 calibrated examiners (W.V., M.E., and M.M.), who independently scored 20 randomly selected patients. The intraclass coefficient resulted in excellent agreement (0.868-0.998).
A mean discriminant score was determined for each extraction and nonextraction centroids (1.15 and–0.54, respectively), and a weighted mean discriminant score of the 2 centroids (the optimal cut-off point) was calculated as–0.0015 ( Fig 1 ). The borderline patients were selected as those with discriminant scores that were within 1 standard deviation from the optimal cut-off point, which was–0.5 to 1.0. This method yielded 30 extraction and 57 nonextraction patients.
Histogram of standardized discriminant scores of the 204 Class I and mild Class II patients ( purple , mean standardized discriminant scores of nonextraction [ light blue ] and extraction [ dark blue ] patients; orange , weighted mean of the 2 centroids [or cut off point]; red , overlapping borderline extraction and nonextraction patients used).
The 30 extraction patients were age- and sex-matched with 30 patients from the nonextraction group, yielding the final sample that was analyzed. There were 14 males and 16 females present in each treatment group, and there was no statistically significant difference in mean age. The mean ages for the extraction and non-extraction groups were 17.65 ± 8.28 years and 16.99 ± 5.97 years, respectively ( Table I ). The treatment duration for the nonextraction group was 24.63 ± 6.16 months, 4.9 months faster than the extraction group, which completed treatment in 29.53 ± 9.94 months. The variance in ethnicity of the samples was noted, and a Fisher exact test was performed to assess if the distribution of ethnicities in the 2 treatment groups was significantly different. There was no significant difference in the distribution of ethnicities in the extraction and nonextraction groups ( P = 0.285).
Table I
Descriptive statistics and pretreatment comparisons of the extraction and nonextraction borderline sample
| Nonextraction | Extraction | P value | |||
|---|---|---|---|---|---|
| Patient demographics | |||||
| Age (y) (mean ± SD) | 17.65 ± 8.28 | 16.99 ± 5.97 | 0.723 | ||
| Min: 12.00 | Min: 11.25 | ||||
| Max: 52.42 | Max: 42.94 | ||||
| Male | 14 | 14 | |||
| Female | 16 | 16 | |||
| Malocclusion | Class I | Class II | Class I | Class II | |
| 19 | 11 | 18 | 12 | ||
| Ethnicity, n (%) | White: n = 10 (33.3) | White: n = 4 (13.3) | |||
| Black: n = 6 (20.0) | Black: n = 7 (23.3) | ||||
| Asian: n = 2 (6.7) | Asian: n = 5 (16.7) | ||||
| Middle Eastern/other: n = 12 (40.0) | Middle Eastern/other: n = 14 (46.7) | ||||
| Extraction pattern | U4/L4 | U4/L5 | |||
| 22 | 8 | ||||
| Treatment duration (mo) | 24.63 ± 6.16 | 29.53 ± 9.94 | 0.025 ∗ | ||
| Model values | |||||
| Maxillary crowding (mm) | Mean | –3.91 | –4.37 | 0.524 | |
| SD | 2.83 | 2.72 | |||
| Mandibular crowding (mm) | Mean | –5.85 | –6.21 | 0.568 | |
| SD | 2.29 | 2.60 | |||
| Overbite (%) | Mean | 41.23 | 40.15 | 0.823 | |
| SD | 19.48 | 17.97 | |||
| Overbite (mm) | Mean | 3.05 | 3.01 | 0.927 | |
| SD | 1.48 | 1.32 | |||
| Overjet (mm) | Mean | 3.96 | 4.18 | 0.616 | |
| SD | 1.55 | 1.77 | |||
| Right molar (mm) | Mean | 0.77 | 0.87 | 0.642 | |
| SD | 0.78 | 0.87 | |||
| Right premolar (mm) | Mean | 1.70 | 2.20 | 0.270 | |
| SD | 1.47 | 2.01 | |||
| Left molar (mm) | Mean | 0.82 | 0.75 | 0.771 | |
| SD | 0.85 | 0.92 | |||
| Left premolar (mm) | Mean | 1.97 | 2.43 | 0.145 | |
| SD | 1.19 | 1.26 | |||
| Cephalometric values | |||||
| SNA (°) | Mean | 82.47 | 80.87 | 0.123 | |
| SD | 3.73 | 4.21 | |||
| SNB (°) | Mean | 77.77 | 76.70 | 0.284 | |
| SD | 3.43 | 4.15 | |||
| ANB (°) | Mean | 4.70 | 4.17 | 0.389 | |
| SD | 2.49 | 2.20 | |||
| Facial angle (FH-NPg) (°) | Mean | 87.59 | 85.33 | 0.009 ∗ | |
| SD | 3.11 | 3.40 | |||
| N perp -A (HP) (mm) | Mean | –0.58 | –2.64 | 0.029 ∗ | |
| SD | 3.47 | 3.66 | |||
| N perp -B (HP) (mm) | Mean | –8.42 | –10.35 | 0.236 | |
| SD | 5.66 | 6.76 | |||
| N perp -Pg (HP) (mm) | Mean | –9.65 | –11.57 | 0.323 | |
| SD | 6.42 | 8.33 | |||
| Chin prominence (Pg-NB) (mm) | Mean | 0.09 | 0.15 | 0.908 | |
| SD | 2.17 | 1.56 | |||
| Convexity angle (N-A-Pg) (°) | Mean | 9.35 | 8.24 | 0.471 | |
| SD | 6.31 | 5.60 | |||
| Wits appraisal (mm) | Mean | 1.75 | 1.60 | 0.832 | |
| SD | 2.52 | 2.81 | |||
| Mx length (Co-A) (mm) | Mean | 80.56 | 78.35 | 0.096 | |
| SD | 5.74 | 4.24 | |||
| Md length (Co-Gn) (mm) | Mean | 104.83 | 102.92 | 0.261 | |
| SD | 6.99 | 6.04 | |||
| Unit length diff (mm) | Mean | 24.27 | 24.57 | 0.781 | |
| SD | 4.40 | 4.01 | |||
| Upper face ht (N-ANS) (mm) | Mean | 48.22 | 47.99 | 0.805 | |
| SD | 3.40 | 3.79 | |||
| Lower face ht (ANS-Me) (mm) | Mean | 62.45 | 62.6 | 0.915 | |
| SD | 5.96 | 4.87 | |||
| Facial height ratio (N-ANS/ ANS-Me) | Mean | 77.55 | 76.87 | 0.658 | |
| SD | 5.74 | 6.10 | |||
| SN-OP (°) | Mean | 16.23 | 16.67 | 0.707 | |
| SD | 4.26 | 4.70 | |||
| SN-GoGn (°) | Mean | 34.21 | 35.82 | 0.299 | |
| SD | 6.23 | 5.68 | |||
| y-axis (SGn-FH) (°) | Mean | 60.51 | 63.66 | 0.004 ∗ | |
| SD | 4.49 | 3.46 | |||
| FMA (°) | Mean | 26.62 | 29.36 | 0.068 | |
| SD | 6.64 | 4.59 | |||
| U1-PP (°) | Mean | 112.48 | 114.69 | 0.262 | |
| SD | 6.45 | 8.57 | |||
| U1-SN (°) | Mean | 104.60 | 106.07 | 0.478 | |
| SD | 5.72 | 9.74 | |||
| U1-NA (°) | Mean | 22.12 | 25.21 | 0.139 | |
| SD | 6.46 | 9.24 | |||
| U1-NA (mm) | Mean | 4.66 | 6.08 | 0.039 ∗ | |
| SD | 2.42 | 2.77 | |||
| Interincisal angle (U1-L1) (°) | Mean | 122.67 | 119.54 | 0.301 | |
| SD | 11.26 | 11.92 | |||
| IMPA (°) | Mean | 96.36 | 96.45 | 0.965 | |
| SD | 9.02 | 7.96 | |||
| L1-NB (°) | Mean | 30.52 | 31.06 | 0.795 | |
| SD | 8.60 | 7.56 | |||
| L1-NB (mm) | Mean | 7.36 | 7.84 | 0.560 | |
| SD | 3.30 | 3.03 | |||
| L1-Apg (mm) | Mean | 4.54 | 5.33 | 0.291 | |
| SD | 3.08 | 2.64 | |||
| U1-PP (mm) | Mean | 27.17 | 27.47 | 0.687 | |
| SD | 2.65 | 2.96 | |||
| U6-PP (mm) | Mean | 21.22 | 21.88 | 0.280 | |
| SD | 2.30 | 2.39 | |||
| L1-MP (mm) | Mean | 39.42 | 39.28 | 0.887 | |
| SD | 4.10 | 3.29 | |||
| L6-MP (mm) | Mean | 29.00 | 28.73 | 0.772 | |
| SD | 3.86 | 3.20 | |||
| Holdaway ratio | Mean | 0.38 | 0.08 | 0.348 | |
| SD | 1.59 | 0.30 | |||
| Upper lip to E-line (mm) | Mean | –0.82 | –0.46 | 0.668 | |
| SD | 3.13 | 3.21 | |||
| Lower lip to E-line (mm) | Mean | 1.41 | 2.10 | 0.458 | |
| SD | 3.61 | 3.59 | |||
| Nasolabial angle (°) | Mean | 108.86 | 105.85 | 0.339 | |
| SD | 13.81 | 10.05 | |||
| Soft tissue face height ratio (G’-Sn:Sn-Me’) | Mean | 1.03 | 1.06 | 0.433 | |
| SD | 0.10 | 0.13 | |||
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