The aim of this study was to compare evaluations of the aesthetic outcome of class II orthognathic patients, as performed by observers with varying expertise using three-dimensional (3D) facial images, and to examine the relationship of aesthetic ratings in relation to quantitative surgical changes. Pre- and postoperative 3D facial images of 20 surgically treated class II patients (13 female, 7 male) were assessed for aesthetics by orthodontists, maxillofacial surgeons, and laypeople. Attractiveness ratings for the lips, chin, and overall facial aesthetics were evaluated on a 5-point Likert scale. Correlation between the aesthetic scores was obtained and quantitative surgical changes were examined. For all groups of observers, significant improvements in attractiveness scores were found, especially for the chin assessment. Orthodontists perceived the greatest improvement and laypeople the smallest. Overall, laypeople scored higher with less variability, but with lower intra- and inter-observer agreement. No significant correlation was found between the aesthetic improvement and soft tissue surgical changes. To avoid patient dissatisfaction, it is important to bear in mind that the demands and perception of aesthetic improvement after orthognathic surgery are higher for clinicians than for the general public.
Adult patients seeking orthodontic treatment seem to be largely driven by aesthetic concerns . This is not surprising, since facial appearance plays a significant role in many aspects of life. Attractive individuals are perceived to be more successful and to have better social skills. They also appear to have higher self-esteem than their less attractive peers . Combined orthodontic–orthognathic treatment is used routinely in non-growing skeletal class II patients to obtain a correct occlusion and skeletal relationship and to improve facial aesthetics. However, the perception of facial aesthetics is a complex issue because of its subjective nature. Establishing a well-balanced and attractive face can be challenging, because perceptions of aesthetic morphology may differ between clinicians and laypeople. Since patients are mainly judged by their peers, it is important to understand the differences in perception of facial attractiveness between professionals and society, in order to optimize treatment goals. Adequate communication between clinician and patient is also essential to avoid postoperative dissatisfaction .
In the literature, controversy remains as to whether laypeople and clinicians agree in their perceptions of facial attractiveness. General agreement between professionals and laypeople has been found in several studies . Also, both clinicians and laypeople indicated better improvement in patients with large vertical and horizontal surgical changes in a previous study . Other studies have suggested that laypeople are more tolerant than clinicians and show the greatest variation in what they consider attractive .
Various techniques have been used in the past to evaluate perceptions of facial aesthetics, such as silhouettes, photographs, and line drawings. All of these methods provide a two-dimensional (2D) view of a three-dimensional (3D) face. Considering the advancements made in digital imaging, it has since become possible to use 3D facial images with a high level of informational content.
The aims of the current study were (1) to analyze the aesthetic evaluations made by laypeople, orthodontists, and maxillofacial surgeons of the pre- and postsurgical 3D facial images of class II patients who had undergone orthognathic surgery, and (2) to examine the relationship between the aesthetic ratings and quantitative surgical changes.
Materials and methods
This study was registered and approved by the Medical Ethics Committee of the University Hospitals Leuven (Leuven, Belgium).
The inclusion criteria for patient selection were restricted to the following: (1) skeletal class II patients, (2) who had undergone orthognathic surgery at the Department of Oral and Maxillofacial Surgery of the University Hospitals Leuven between August 2014 and April 2016, and (3) for whom 3D facial images of sufficient quality, obtained before and at 6 months after surgery, were available. All patients meeting the inclusion criteria during the time period considered were selected. Patients with congenital malformations were excluded.
The study sample consisted of 20 patients (13 female and 7 male), aged between 15 and 56 years at the time of surgery (mean age 26 years). Sixteen patients underwent a bilateral sagittal split osteotomy advancement. One of these patients also received a genioplasty. A bimaxillary osteotomy was carried out in four patients, with three of the four undergoing an additional genioplasty. A bimaxillary procedure was performed in one patient because of an anterior open bite. In another patient, an additional maxillary advancement was done to improve facial aesthetics. Two patients underwent a counterclockwise rotation of the maxillomandibular complex to maximize chin projection. All patients provided informed consent for the use of their images in this study.
The mean surgical mandibular advancement was 4.24 mm (range 0.6–10.4 mm). The patients had a mean preoperative anterior lower facial height (ALFH) of 64.2 mm (range 53.7–83.7 mm), a mean upper to lower facial height ratio (UFH:LFH) of 79.3% (range 58.0–96.0%), and a mean mandibular plane angle (SNGoMe) of 33.6° (range 20.0–46.0°).
For each patient, a 3D facial image of adequate quality was obtained before surgery (T0) and at 6 months after surgery (T1) ( Fig. 1 ). All facial scans were obtained using a Planmeca ProMax 3D Mid unit (Planmeca Inc., Helsinki, Finland) under standardized conditions. Patients were scanned in natural head position with their eyes open and with a relaxed facial musculature.
The pre- and postsurgical facial images were judged by a panel of ten orthodontists (eight female, two male), five oral and maxillofacial surgeons (one female, four male), and four laypeople (two female, two male). The orthodontists and surgeons represented various levels of experience and were not involved in the treatment of the patients. All observers were adults. The group of laypeople consisted of staff members of the University Hospitals Leuven without training in dentistry.
Aesthetic assessment of the facial images
The subjects were assessed in four sessions, with five patients included in each session. For each session, pre- and postoperative 3D facial images were placed in random order and presented using ProPlan software version 2.1 (Materialise, Leuven, Belgium). Observers were asked to evaluate the 3D facial images aesthetically on different levels using a 5-point Likert scale: 1 = very unattractive, 2 = unattractive, 3 = not attractive or unattractive, 4 = attractive, 5 = very attractive. For each facial image, an aesthetic score from 1 to 5 was given for lip attractiveness, chin attractiveness, and overall facial attractiveness. Observations were performed individually, undisturbed, and at the same computer. Each observer was able to manipulate the facial images in all directions to obtain an accurate 3D view. There was no time limit to complete the scoring. Instructions were given to evaluate the images in the most objective way and to use the whole scale.
At least 1 week before the actual assessment, a training session was organized to standardize the assessments of the observers. The training sample consisted of five class II patients (three female, two male), who were not included in the study sample. Pre- and postoperative 3D facial images were also placed in random order.
To assess intra-observer reliability, a second assessment round was performed by the same observers at least 1 week after the first observation. The four sessions were presented in a random order to re-evaluate the subjects.
Quantitative evaluation of the facial images
To quantify soft tissue facial changes, pre- and postoperative scans were imported into 3-matic software (version Medical 11; Materialise, Leuven, Belgium) and a protocol of five steps was followed, as shown in the flowchart in Fig. 2 and outlined below.
Registration: Pre-surgical and postoperative scans were matched using the surface registration tool. Confounding regions such as hair, ears, and neck were removed.
Identification of landmarks: In order to isolate the facial regions of the chin and the lips, soft tissue landmarks were identified to create reference planes using the method described by Verhoeven et al. , who developed a validated technique for the evaluation of facial asymmetry on 3D images. Nine soft tissue landmarks were identified manually: left (ExL) and right (ExR) exocanthion, sellion (Se), subnasale (Sn), left (AcL) and right (AcR) alar curvature, left (StmL) and right (StmR) stomion, and soft tissue B-point (B′) ( Fig. 3 a).
Construction of reference and cutting planes: Three reference planes were created in order to construct cutting planes to isolate the chin and lip regions. A transverse plane was identified through ExL, ExR, and Se. A coronal plane was constructed perpendicular to the transverse plane through both exocanthi. A sagittal plane was constructed through Se and Sn, perpendicular to the coronal plane. Afterwards, four cutting planes were created: a first plane through Sn, AcR, and AcL , a second plane through B′ and parallel to the first cutting plane, and another two planes parallel to the sagittal plane, with one through StmR and one through StmL ( Fig. 3 b).
Splitting regions of interest: The regions of interest were split and isolated using the four cutting planes described ( Fig. 3 c).
Distance maps: Finally, a distance map of the chin, the lips, and the overall facial image was obtained to evaluate the changes between the pre- and postoperative scans ( Fig. 3 d). The distance map is the Euclidean distance between every point on the surface of object 1 and its corresponding point on the surface of object 2. The software provides the mean, median, first quartile, third quartile, and the root mean square (RMS) of the surgical movements, illustrating the quantitative changes between the pre- and postoperative images for the different facial regions.
The same protocol was applied to five scans of four control subjects in order to evaluate the reproducibility of facial scans in patients without surgical treatment.
A linear mixed model was used to evaluate the mean difference in aesthetic rating before and after surgery in general and for the three separate observer groups, with observer and patient as the crossed random effect. P -values for differences between measurements before and after surgery were corrected for simultaneous hypothesis testing according to Šidák. A normal quantile plot of the residual values and a residual dot plot showed that the basic assumptions of normality and equal variability of residuals were met. Differences in scores between laypeople, orthodontists, and surgeons were analyzed with the unpaired Wilcoxon test. A bootstrap procedure was used to obtain P -values for the difference between observer groups for score variability. Intra- and inter-observer agreement was verified using Janson and Olsson’s tau-statistics . Spearman rank correlation coefficients were calculated to represent the relationship between quantitative surgical changes and changes in Likert scores before and after surgery. P -values were only considered significant if they were less than 0.05.
Mean scores of attractiveness before and after surgery and the median and mean improvement in the aesthetic assessment for the three panel groups are presented in Table 1 .
|Observer||Mean score T0||Mean score T1||Median T0–T1||Mean T0–T1||P -value||Improvement T1–T0 (%)||Worsening T1–T0 (%)||Unchanged T1–T0 (%)|
|All observers||2.81||3.29||−0.05||−0.49||0.0001 *||56.25||24.92||18.83|
|All observers||2.45||3.18||−0.50||−0.73||0.0001 *||64.92||17.83||17.25|
|All observers||2.61||3.19||−0.50||−0.58||0.0001 *||61.58||14.42||24.00|