The development of interdisciplinarity has promoted the combination of computer technology and stomatology. More and more computer-aided technology has been flexibly applied in the diagnosis and treatment of oral and maxillofacial diseases (Sharaf et al., 2010). In the field of oral and maxillofacial surgery, computer-aided technology combined with digital surgical diagnosis and treatment technology derived from maxillofacial surgery is mainly applied in preoperative digital planning, intraoperative real-time navigation, surgical guide design and postoperative digital evaluation of efficacy (Eggers et al., 2009). Using computer-aided technology, we can process the original image data, such as image enhancement, recognition, registration, fusion and segmentation, to guide clinical practice and improve the level of diagnosis and treatment of clinicians. Lentzen et al. developed a method based on anatomical and volumetric analysis of fibro-osseous lesions to guided clinical decisions (Lentzen et al., 2021). In recent years, 3D visualization technologies such as virtual reality (VR), augmented reality (AR) and mixed reality (MR) have shown wide application prospects in surgery planning, intraoperative navigation and operation training. In particular, the MR technology combines the VR technology with the AR technology, which can observe the real environment and the virtual holographic image at the same time, and realize the interaction through gestures, voice, vision and other ways, breaking the boundary between the virtual world and the real world. At the same time, MR technology can transform 2D medical images such as CT, MRI and PET into intuitive 3D virtual models and integrate them with the real environment (Fang et al., 2020; Cartucho et al., 2020). These characteristics make MR technology of great significance for oral and maxillofacial surgery with fine morphology and complex function.

Cystic lesions of the jaw include some cystic neoplasms that are latent, with no discernible symptoms in the early stages. As the cyst gradually expands, it squeezes the bone and extends into the surrounding tissue, which can lead to large jaw cavities, bone defects and jaw deformities. According to pathological classification, cystic lesions of the jaw can be divided into odontogenic and non-odontogenic types, including apical cysts, dental cysts, odontogenic keratocysts, and ameloblastomas (Kennedy, 2018). In clinical diagnosis and treatment, curettage is one of the main methods of treating jaw cysts (Dashow et al., 2015). The recovery of osteogenesis after surgery has an important influence on the recovery of jaw function and shape. Additionally, the implantation of missing teeth also depends on good osteogenic recovery in the lesion area. Therefore, accurate postoperative evaluation of the efficacy of curettage is particularly important to predict the bone regeneration level in the lesion area, functional recovery, and postoperative recurrence (Ihan Hren and Miljavec, 2008).

At present, curettage efficacy can be evaluated two-dimensionally, based on panoramic film images, or three-dimensionally, based on computed tomography (CT) data. Three-dimensional data of the lesions can be lost in panoramic images, and the boundary of cystic lesions is difficult to distinguish because of the overlapping of buccal and lingual images and the interference of adjacent structures such as the maxillary sinus. Studies have shown that bone mineral changes under 30% cannot be detected on X-rays; therefore, panoramic radiographs are unable to sensitively reflect tiny changes in the bone mineral composition of cystic lesions. Additionally, comparisons of the extent of the cystic lesion may be affected by the patient's cephalic deviation and changes in the exposure conditions of each radiographic image (Chiapasco et al., 2000; Zakariasen et al., 1984). CT data are generally scanned by clinicians in the horizontal, sagittal, and coronal planes, without quantitative calculation. In addition, the new bone begins to grow from the edge of the lumen wall, which results in an unclear boundary of the cyst on the postoperative image, making it impossible to accurately compare the cyst with previous imaging or calculate its size. In clinical practice, the contrast and brightness of the two images are sometimes inconsistent, which cannot reflect the true situation of the lesion. Achieving accurate postoperative evaluation results is a great challenge when traditional image processing methods are being used.

Digital techniques for evaluating efficacy using computer methods to reconstruct the original CT image data in 3D provides a new method for accurately evaluating cystic lesions postoperatively. Differing from traditional maxillofacial surface reconstruction, the three-dimensional reconstruction of the cystic cavity eliminates the interference of the surrounding jaw, and makes the jaw transparent or even only displays the cystic cavity, allowing accurate calculation of changes in the volume of the lesion. The primary purpose of this study was to establish a method to accurately and quantitatively describe the characteristics of cystic lesions after curettage by three-dimensional reconstruction and to explore the possible factors affecting the curative effect of curettage for cystic lesions. Secondly, we explored the application of image registration technology in the evaluation and study of jaw lesions and other skeletal lesions.