Impact of orthognathic surgery on emotional expression and smile aesthetics in Chinese patients as measured by FaceReader: a before-and-after study

Abstract

Background: The attractiveness of a person's smile is influenced by several factors, including gingival display, incisor show, and facial asymmetries. Malocclusion has long been recognized as having a significant negative impact on smile aesthetics. Addressing dentofacial deformities is a major treatment goal in orthodontic and orthognathic interventions, aiming to improve both functional and aesthetic outcomes. We sought to quantify and assess the impact of orthognathic surgery on a patient's expression of happiness within their smile, thereby addressing the current research gap in this highly subjective field.

Methods: We utilized FaceReader, a commercially available and previously validated artificial intelligence (AI) system, to analyze preoperative and postoperative facial photographs of 216 Chinese patients who underwent orthognathic surgery between January 1, 2021, and December 31, 2022. The AI software measures seven cardinal emotions and associated facial action units, providing an objective evaluation of emotional outcomes.

Results: Our findings indicated a significant postoperative increase in patients' expression of "happiness" while smiling, accompanied by a concurrent decrease in their estimated age. Patients with insufficient incisor show and open bite exhibited notable improvements in emotional expression, while those with a gummy smile showed no significant change. Additionally, stratification based on malocclusion classification (class I, II, III) revealed consistent improvements in emotional outcome scores among class II and III patients.

Conclusion: Our findings underscore the potential of AI in providing objective insights into emotional changes following orthognathic surgery.

Keywords: Artificial intelligence; Dental esthetics; Happiness; Orthognathic surgery; Smiling.

Fig. 1

Flowchart of current study.

Fig. 2

Case example. A 24-year-old man underwent bimaxillary orthognathic surgery for class III malocclusion, with maxillary advancement, clockwise rotation, and mandibular setback. No genioplasty or additional procedures were performed. The photos, taken at 27 months postoperatively, show preoperative and postoperative results with the patient in repose (A, D), smiling (B, E), and FaceReader software (Noldus Information Technology BV) face detection during smiling (C, F). Informed consent was obtained from the patient for publishing this photo.

Fig. 3

Graph depicting the average percentage of happiness before-and-after orthognathic surgery (in repose and while smiling) in patients with dentofacial deformities. Emotion analysis was conducted using FaceReader software (Noldus Information Technology BV).

Fig. 4

Graph showing the mean output of action units (AUs) associated with happiness preoperatively versus postoperatively during smiling. Patients with dentofacial deformities who underwent orthognathic surgery were evaluated using FaceReader software (Noldus Information Technology BV), which detects facial AUs.

Fig. 5

Comparison of actual age at the time of photography versus estimated age by FaceReader software (Noldus Information Technology BV) in the same group of patients with dentofacial deformities who underwent orthognathic surgery.