How predictable are 3D simulations of facial changes?

Orthognathic surgery is a treatment designed to optimize the balance between the upper jaw, lower jaw, and chin region. Patients with an overly large or undersized lower jaw, where the lower jaw is positioned too far forward or backward, often require combined upper and lower jaw correction. To achieve this, orthodontic treatment is often necessary before and after jaw surgery to correct the tooth position and bite. This ensures proper function and greater stability after the surgery.

A chin correction (genioplasty or mentoplasty) is a targeted surgery on the chin region to enhance chin prominence or reduce chin asymmetry. This type of surgery is less invasive compared to orthognathic surgery because only the chin region is operated on. This procedure generally does not require orthodontic correction of the tooth position, and there is no need to follow a modified diet after the surgery. As part of aesthetic correction of the lower facial profile, many chin corrections are performed, resulting in stable and predictable results.

To achieve a predictable result at the level of the facial profile, we carefully evaluate the position of the teeth, jaws, and soft tissues of the chin prior to a chin correction. We listen carefully to the patient's wishes. The most challenging aspect is translating the patient's wishes into the number of millimeters of chin displacement and the number of degrees of rotation so that the desired result at the soft tissue level is visible. Therefore, we always use a 3D simulation of the soft tissues to personalize our chin corrections. This method allows us to demonstrate to the patient the potential treatment outcome before the chin correction.

Image: An example of a 3D soft tissue simulation of a genioplasty

The central question in this modern method, known as soft tissue backward planning, is how accurate the 3D soft tissue simulation is. Does the simulated result match the actual result? Over the past ten years, Dr. Xi and Dr. Liebregts have conducted extensive research on this topic. Last month, Dr. Xi published a new study in the European Journal of Cranio-Maxillo-Facial Surgery that addresses this important question, in collaboration with Chang Gung Memorial Hospital in Taipei, a leading university medical center in Southeast Asia for surgical jaw corrections.

What does the research show?

This study, conducted by Chang Gung Memorial Hospital (Taipei) in collaboration with Radboud University Medical Center (Nijmegen), investigated the accuracy of 3D simulations of facial soft tissue changes in patients with a class III jaw deformity who underwent orthognathic surgery.

In this study, sixty patients were divided into two groups based on their facial pattern: Group 1: high-angle group, meaning patients with a long and narrow face; and group 2: low-angle group, namely patients with a shorter and wider face. All patients were virtually planned using SimPlant O&O software prior to orthognathic surgery, after which the predicted soft tissue facial profile was compared with the actual post-operative result using 3D (CBCT) scans of the face.

The study demonstrated that current generation 3D simulations generally offer high clinical accuracy. The average deviation between predicted and measured facial changes was less than 2 mm. This deviation is considered clinically acceptable because a 2 mm difference at the soft tissue level is generally not detectable. The results indicate that surgeons can rely on virtual planning to predict the final profile in most cases.

However, there are differences between facial regions. The chin region proved to be the least predictable, with an average error of approximately 1.5 to 1.6 mm. In the cheek and lower lip regions, forward movement was often underestimated. Soft tissue prediction was slightly more accurate in high-angle patients compared to low-angle patients. These findings demonstrate that soft tissue simulation is particularly reliable for global facial shape changes. However, surgeons' clinical experience remains important for predicting subtle contour changes around the chin.

Clinical Significance

Practically, this means that surgeons and patients can achieve the expected changes with greater predictability based on 3D soft tissue simulations. At the same time, it remains important to incorporate clinical experience and patient-specific factors (such as soft tissue thickness in the chin region, age, ethnicity, muscle tone, and skin elasticity) into the final surgical planning.

At EKOC, we strive to offer every patient a predictable, natural, and personalized treatment outcome through 3D soft tissue simulation.

Source:

Chen CY, Xi T, Ko EW, Tsao SY. Accuracy of 3D simulation in soft tissue change after orthognathic surgery in class III malocclusion: Influence of different vertical facial patterns. J Craniomaxillofac Surg. 2025 Oct 16:S1010-5182(25)00300-2. doi: 10.1016/j.jcms.2025.09.012.