Three-dimensional region-based study on the relationship between soft and hard tissue changes after orthognathic surgery in patients with prognathism

Abstract

Both deep understanding and reliable prediction of postoperative soft tissue changes are crucial for planning orthognathic surgery. Instead of estimating soft tissue responses by measuring individual landmark changes, this study aimed to investigate the relationship (ratio) between soft and hard tissue movements in different facial regions through three-dimensional cone-beam computed tomography (CBCT). Preoperative and postoperative CBCT images were superimposed using the surface registration method on the basis of the cranial base, and 10 facial regions of interest were defined. Region-based volumetric subtractions between the preoperative and postoperative segments were performed. The volumetric differences and surface of each region were used to estimate the average movement. Correlation and regression analyses were performed to examine the relationships between the corresponding soft and hard tissue movements. An overall pattern of facial soft tissue movement was observed in patients with prognathism who underwent orthognathic surgery. The experiment results have shown that mean ratios for the average soft-to-hard tissue movements in the facial regions varied, which may not exactly be similar to the published reports because of the population biocharacteristics and study methods, but the trend is in agreement with the previous studies. Additionally, the prediction capability of the regression model was significantly high, ranging from 0.786 to 0.857, in upper lip, upper vermilion, and chin regions, thus demonstrating that the skin outline changes in these critical regions could be reliably predicted from the underlying bone movements. These results could likely be applied in future soft tissue simulation in orthognathic surgery.

The outcome of skeletofacial reconstruction with mandibular rotation for management of asymmetric skeletal class III deformity: A three-dimensional computer-assisted investigation

“…7) and value ≤0.5 mm (Fig. 8) considered acceptable to ensure that the corresponding reference areas had maximum precision 31,36 . After the registration, the FHP and midsagittal plane (MSP, Table 5) were employed on the skull model for comparisons (Fig.…”

Accuracy of in vitro mandibular volumetric measurements from CBCT of different voxel sizes with different segmentation threshold settings

“…CBCT and 3D reconstruction can be used to assess the efficiency of bone augmentation by aiding in the evaluation of the osteogenesis of grafting materials, and the accuracy of volumetric measurement plays a key role here. Lo et al [8] investigated the relationship between soft- and hard-tissue changes after orthognathic surgery. Pre- and postoperative CBCT images were superimposed by the surface registration method, and the volumetric differences of each region were used to estimate the average movement.…”

Outcome of facial contour asymmetry after conventional two-dimensional versus computer-assisted three-dimensional planning in cleft orthognathic surgery

“…Instead of using the widely applied landmarks-guided linear and angular measurements for determination of the facial asymmetry, the employed 2D-and 3D photogrammetric-based analyses take advantage of all facial surface-related data points which characterizes a more global and precise evaluation of the facial contour asymmetry. These photogrammetric facial surface-based methodologies were previously adopted by other groups testing different hypothesis, with the validity and reproducibility parameters being formerly demonstrated [39][40][41][42] . However, the adopted methods can be time-consuming and also be associated with limitations related to operator-dependent landmark and facial mid-sagittal plane identification.…”