BACKGROUND: Paranasal augmentation has been a popular approach in restoring Asian patients\' lateral profile. Irregular surface in the surgical area emphasizes the importance of morphological evidence for the preoperative evaluation and the design of paranasal implants.
METHODS: We retrospectively collected craniofacial computer tomography scans of patients in the department of plastic surgery from 2020 to 2022. The imaging data were imported to Mimics (version 20.0; Materialize, Leuven, Belgium) for three-dimensional reconstruction. Measurements of osteal nasal base were performed in 3-matics (version 12.0; Materialize). The severity of paranasal concavity was graded by a senior doctor to study the correlation with measured variables.
RESULTS: Fifty-seven patients with a median age of 27 years (IQR: 22-33) were included in the study. For design of paranasal implants, the lengths of both lower and lateral edge were measured for reference. In the regression analysis, the alar base-alveolar process angle was significantly associated with the degrees of paranasal concavity (OR = 1.222, p = 0.00001).
CONCLUSIONS: Morphological data of osteal nasal base were measured and presented in the current study. The analysis supported that alar base-alveolar process angle be used for preoperative grading and evaluation to help guiding treatment decisions.
METHODS: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The digital fabrication of a maxillary obturator with a 3D-printed polyetheretherketone (PEEK) framework is described. Digital oral data were scanned for the computer-aided design (CAD) of the framework and the 3D printing of a preliminary resin cast. The framework was accurately printed from a PEEK filament material. A secondary impression was made to fabricate the definitive cast. The PEEK framework exhibited precise fit, excellent retention, and reduced weight compared with a typical metal framework.

A fully digital workflow for the design and manufacture of prostheses for maxillectomy defects was described. Three-dimensional images from spiral computed tomography and intraoral scanning were used to generate a three-dimensional digital cast of a maxillectomy defect. The obturator prosthesis was then designed on the digital cast by combining dental computer-aided design and reverse engineering software programs. The prosthesis was subsequently milled from polyetheretherketone or three-dimensional-printed from polylactic acid.

With the rapid development of 3D printing, it is widely used in the field of cranio-maxillofacial surgery. Through the individualized production of 3D printing, the backward mode of traditional production relying on manual shaping has been changed to meet the needs of different patients. However, as no clear specification exists for the performance requirements of 3D printing metal powder for cranio-maxillofacial surgery, its long-term development is not feasible. In this paper, the preparation technologies of 3D printing metal powder for cranio-maxillofacial prostheses (i.e., gas atomization, rotating electrode atomization, and radio frequency plasma spheroidization) and 3D printing forming technologies (i.e., selective laser melting, electron beam selective melting, and laser-engineered net shaping) are introduced. The performance requirements of 3D printing metal powder for cranio-maxillofacial prostheses are then summarized according to the characteristics of the preparation and forming technologies described.
随着3D打印的快速发展，其在口腔颅颌面外科的应用越来越广泛，3D打印个性化生产改变了传统依靠手工成型的落后模式，满足了不同患者的使用需求。但目前对于颅颌面修复体制作用3D打印金属粉末的性能要求并无明确规范，不利于产业的长久发展。本文对颅颌面修复体制作用3D打印金属粉末的制备工艺（气雾化法、等离子体旋转电极雾化法、射频等离子体球化法）以及3D打印成型工艺（选区激光熔化、电子束选区熔化、激光近净成形）进行了介绍，并且根据制备工艺及成型工艺特点总结了颅颌面修复体制作用3D打印金属粉末的性能要求。.

Objective: To explore a digital negative molds technique based on three-dimensional (3D) printing to assist in the manufacture of maxillofacial prostheses, and to improve the deficiency of the current clinical treatment. Methods: Seventeen patients with maxillofacial defects (including nasal defects, orbital defects, cheek defects, auricle defect) were scanned by means of facial optical scanning and computer tomography (CT). The 3D models were then reconstructed and global registration was made to merge the reconstructed models into a new digital model for 3D design. The 3D design of the prostheses was implemented in software. The mechanical connection structure was designed by forward engineering technology for 3 patients with intra-oral defects in maxilla who needed to make removable partial dentures, so that the silicone prostheses and removable partial denture could be combined. The removable partial dentures were made by conventional method and connected with the prostheses. According to the 3D data of the prostheses, the digital negative molds were designed, and the 3D printing technology was used to finish the processing of the resin molds. Silicone for prostheses were filled and cured in the resin molds to fabricate the clinical restorations for the patients. The margin adaptation and retention of the prostheses was detected. Results: Twenty patients with varying degrees of maxillofacial defects were rehabilitated using the courses developed in the study. All patients reported no pain or discomfort during the treatment; and they were satisfied with the final prostheses of the shape, color, retention, stability, etc. Eighteen of the prostheses showed good marginal adaptation, and sixteen of the prostheses showed good retention effect. Conclusions: The digital negative molds technique used in this study could greatly reduce the intensity of manual operation and provided a good therapeutic effect for patients with maxillofacial defects.
目的： 探索三维打印数字化阴模辅助制作口腔颌面缺损赝复体的加工方案，弥补目前口腔临床赝复治疗的不足。 方法： 对17例口腔颌面缺损患者（包括鼻缺损、眼眶缺损、面颊部缺损、耳廓缺损）进行面部光学扫描和头颅CT扫描，配准后构建三维数字化融合模型，进行赝复体计算机辅助设计；对3例上颌骨缺损需同时制作可摘局部义齿的患者进行头颅CT扫描，赝复体设计时正向设计可连接赝复体和可摘局部义齿的机械式连接体。根据赝复体数据设计数字化阴模，并三维打印树脂阴模；硅橡胶充填并固化，完成赝复体制作。检测赝复体边缘密合度和固位力。 结果： 为20例不同程度口腔颌面缺损患者制作了赝复体。所有患者治疗过程中无任何疼痛或不适感，对最终赝复体的形态、颜色、固位力、稳定性等方面满意。18例赝复体边缘密合，2例密合度尚可，无边缘不密合者；16例赝复体固位力佳，4例固位力尚可，无固位力差者。 结论： 三维打印数字化阴模辅助制作赝复体的方法可减少临床手工操作强度，并使口腔颌面缺损患者获得良好的治疗效果。.

BACKGROUND: Digital techniques are not clinically applied for 1-piece maxillary prostheses containing an obturator and removable partial denture retained by the remaining teeth because of the difficulty in obtaining sufficiently accurate 3-dimensional (3D) images.
OBJECTIVE: The purpose of this pilot clinical study was to generate 3D digital casts of maxillary defects, including the defective region and the maxillary dentition, based on multisource data registration and to evaluate their effectiveness.
METHODS: Twelve participants with maxillary defects were selected. The maxillofacial region was scanned with spiral computer tomography (CT), and the maxillary arch and palate were scanned using an intraoral optical scanner. The 3D images from the CT and intraoral scanner were registered and merged to form a 3D digital cast of the maxillary defect containing the anatomic structures needed for the maxillary prosthesis. This included the defect cavity, maxillary dentition, and palate. Traditional silicone impressions were also made, and stone casts were poured. The accuracy of the digital cast in comparison with that of the stone cast was evaluated by measuring the distance between 4 anatomic landmarks. Differences and consistencies were assessed using paired Student t tests and the intraclass correlation coefficient (ICC). In 3 participants, physical resin casts were produced by rapid prototyping from digital casts. Based on the resin casts, maxillary prostheses were fabricated by using conventional methods and then evaluated in the participants to assess the clinical applicability of the digital casts.
RESULTS: Digital casts of the maxillary defects were generated and contained all the anatomic details needed for the maxillary prosthesis. Comparing the digital and stone casts, a paired Student t test indicated that differences in the linear distances between landmarks were not statistically significant (P>.05). High ICC values (0.977 to 0.998) for the interlandmark distances further indicated the high degree of consistency between the digital and stone casts. The maxillary prostheses showed good clinical effectiveness, indicating that the corresponding digital casts met the requirements for clinical application.
CONCLUSIONS: Based on multisource data from spiral CT and the intraoral scanner, 3D digital casts of maxillary defects were generated using the registration technique. These casts were consistent with conventional stone casts in terms of accuracy and were suitable for clinical use.

BACKGROUND: Maxillary defects are usually rehabilitated by a prosthetic obturator.
OBJECTIVE: This study aimed to evaluate the functioning of obturators prosthesis in patients with unilateral defects after maxillectomy.
METHODS: Of 49 patients, 28 underwent to maxillectomy as a result of tumor ablative surgery, and acquired unilateral maxillary defects. Evaluation of the function was performed by applying the Obturator Functional Scale (OFS).
RESULTS: From a total of 49 patients, 28 were treated as follows: 9 with a conventional retained obturator prosthesis (COP), 11 (39%) with an enhanced retentive obturator prosthesis with stud attachment (POP) and 8 (28%) with an enhanced retentive obturator prosthesis with magnetic attachment (POM). The mean OFS score was 80. Scores on functions of speech, swallowing and chewing reached statistical significances (p<0.05) among these three subgroups. Comparing COP and MOP groups, the scores of OFS in the domains of \"Speech-ability to speak in public\" and \"Swallowing-leakage with liquids\" were significantly higher in AOP group. Comparing COP group, the scores of OFS in \"Swallowing-leakage with solid\" and \"Chewing/eating\" domains were increased significantly (p<0.05) both in MOP and AOP groups.
CONCLUSIONS: Obturator prosthesis improves oral function of patients after maxillary defects; the retention of the obturator prosthesis enhanced by the addition of attachments showed more benefits in oral function.

OBJECTIVE: To quantitatively evaluate the tissue surface adaption of a maxillary complete denture wax pattern produced by CAD and 3DP.
METHODS: A standard edentulous maxilla plaster cast model was used, for which a wax pattern of complete denture was designed using CAD software developed in our previous study and printed using a 3D wax printer, while another wax pattern was manufactured by the traditional manual method. The cast model and the two wax patterns were scanned in the 3D scanner as \"DataModel,\" \"DataWaxRP,\" and \"DataWaxManual.\" After setting each wax pattern on the plaster cast, the whole model was scanned for registration. After registration, the deviations of tissue surface between \"DataModel\" and \"DataWaxRP\" and between \"DataModel\" and \"DataWaxManual\" were measured. The data was analyzed by paired t-test.
RESULTS: For both wax patterns produced by the CAD&RP method and the manual method, scanning data of tissue surface and cast surface showed a good fit in the majority. No statistically significant (P > 0.05) difference was observed between the CAD&RP method and the manual method.
CONCLUSIONS: Wax pattern of maxillary complete denture produced by the CAD&3DP method is comparable with traditional manual method in the adaption to the edentulous cast model.

Rapid prototyping (RP) technologies have found many uses in dentistry, and especially oral and maxillofacial surgery, due to its ability to promote product development while at the same time reducing cost and depositing a part of any degree of complexity theoretically. This paper provides an overview of RP technologies for maxillofacial reconstruction covering both fundamentals and applications of the technologies. Key fundamentals of RP technologies involving the history, characteristics, and principles are reviewed. A number of RP applications to the main fields of oral and maxillofacial surgery, including restoration of maxillofacial deformities and defects, reduction of functional bone tissues, correction of dento-maxillofacial deformities, and fabrication of maxillofacial prostheses, are discussed. The most remarkable challenges for development of RP-assisted maxillofacial surgery and promising solutions are also elaborated.

OBJECTIVE: Making impressions for maxillectomy patients is an essential but difficult task. This study developed a novel method to fabricate individual trays by computer-aided design (CAD) and rapid prototyping (RP) to simplify the process and enhance patient safety.
METHODS: Five unilateral maxillectomy patients were recruited for this study. For each patient, a computed tomography (CT) scan was taken. Based on the 3D surface reconstruction of the target area, an individual tray was manufactured by CAD/RP. With a conventional custom tray as control, two final impressions were made using the different types of tray for each patient. The trays were sectioned, and in each section the thickness of the material was measured at six evenly distributed points. Descriptive statistics and paired t-test were used to examine the difference of the impression thickness. SAS 9.3 was applied in the statistical analysis. Afterwards, all casts were then optically 3D scanned and compared digitally to evaluate the feasibility of this method.
RESULTS: Impressions of all five maxillectomy patients were successfully made with individual trays fabricated by CAD/RP and traditional trays. The descriptive statistics of impression thickness measurement showed slightly more uneven results in the traditional trays, but no statistical significance was shown. A 3D digital comparison showed acceptable discrepancies within 1 mm in the majority of cast areas. The largest difference of 3 mm was observed in the buccal wall of the defective areas. Moderate deviations of 1 to 2 mm were detected in the buccal and labial vestibular groove areas.
CONCLUSIONS: This study confirmed the feasibility of a novel method of fabricating individual trays by CAD/RP. Impressions made by individual trays manufactured using CAD/RP had a uniform thickness, with an acceptable level of accuracy compared to those made through conventional processes.