I. Interpretation of the Core Abstract of the Study

Digital imaging and additive manufacturing technologies have expanded the clinical options for dental prosthetic treatment, with stereolithography (SLA) 3D printing enabling precise, controllable reconstruction of congenital or postoperative maxillofacial tissue defects.

This case involves a 65-year-old patient with squamous cell carcinoma of the left maxillary sinus who has undergone bilateral maxillectomy. The treatment plan includes the fabrication of a permanent maxillary obturator. CT imaging data were collected, and an STL file of the defect area was generated using 3D planning software. A precise anatomical model of the defect was then produced via 3D printing. Based on this printed model, a hollow wax pattern for the obturator was created, followed by thermo‑curing silicone rubber to form the obturator component. After positioning the silicone obturator within the oral cavity, a final impression was taken, the master model was replicated, and the cast was sectioned and boxed. Following wax investment removal, a transparent thermosetting acrylic resin was injected into the interior of the obturator to enhance the retention and stability of the acrylic denture base in conjunction with the silicone soft liner of the obturator.

Long-term follow-up was conducted after surgery, with a chairside silicone rubber relining performed at the 6-month recall to optimize fit; the restoration remained free of significant clinical discomfort over 5 years of wear.

Conclusion: Patients following maxillofacial surgery commonly experience complications such as limited mouth opening and pain at the surgical site. The integration of digital 3D printing technology with conventional prosthetic techniques enables the fabrication of highly precise prostheses, significantly alleviating patient discomfort during diagnosis and treatment.

II. The Core Role of 3D Printing Technology in This Study

This study utilized a PVC-layered adhesive 3D‑printing device to fabricate anatomical defect models, which serve as the digital backbone of the entire restoration workflow and fulfill four critical functions:

• Avoid the discomfort of intraoral impressions and accurately restore the anatomy of the defect.

The patient presented with severe trismus and pain in the surgical area, making it impossible to obtain a standard intraoral impression. By directly importing the patient’s CT DICOM images into MIMICS and SimPlant software for three-dimensional reconstruction, an STL file was generated and used to 3D‑print a 1:1 physical anatomical model. This model accurately replicates the extensive 10.4 × 10.5 cm palatal defect, the concavity of the alveolar ridge, the remaining tooth roots, and other intricate details—without any contact with the patient’s oral cavity, thereby minimizing discomfort and anxiety at the source.

• Standardized fabrication of occlusal wax patterns, with a unified restoration reference standard.

Leveraging high-precision 3D-printed physical models, technicians can precisely carve hollow occlusion wax patterns outside the mouth, ensuring perfect conformity to the defect’s contour. This eliminates the need for repeated in‑mouth adjustments, shortens chairside procedure time, and addresses the significant shape deviations and frequent follow-up appointments inherent in traditional manual modeling.

• Integrated mold base, supporting multiple mold reuses.

3D-printed models exhibit excellent physical stability and can be directly embedded in plaster to fabricate casting molds. A single print run enables the replication of multiple batches of silicone rubber impression trays, reducing the costs associated with repeated scanning and modeling, and making them well-suited for high‑volume clinical restorative workflows.

• A visual communication platform for doctors and patients

Physical printed models can visually illustrate the extent of defects and the sealing logic of restorations, enabling clinicians to explain postoperative sequelae and restoration principles to patients and thereby alleviating their psychological apprehension about treatment.

III. Four Major Innovative Breakthroughs of This Study

1. CT imaging directly drives 3D printing, bypassing the traditional intraoral scanning and impression-taking workflow.

Traditional digital prosthetic rehabilitation relies on intraoral scanners to acquire oral data, but patients with limited mouth opening or postoperative wound sensitivity may be unable to cooperate. This approach achieves three-dimensional reconstruction solely from pre- and postoperative CT images, eliminating the need for intraoral scanning and initial impressions. It overcomes the challenges of impression taking in patients following maxillofacial tumor surgery, significantly enhancing the feasibility of prosthetic rehabilitation in cases of severe trismus.

2. Digital 3D-printed models and traditional restoration techniques complement each other’s strengths.

It does not rely solely on 3D-printed prosthetic restorations, but instead adopts a hybrid approach: digital modeling and 3D printing of models, combined with traditional fabrication using silicone rubber and acrylic resin.

3D printing is responsible for high-precision anatomical replication;

• Silicone rubber Molloplast‑B, used as a soft liner for the obturator, conforms to the mucosa and enhances wearing comfort.
• The intermediate interlayer of transparent acrylic resin enhances the bonding between two dissimilar materials, addressing the industry‑wide challenge of silicone rubber easily separating from and detaching from denture bases.
• It combines the precision advantages of 3D printing with the biocompatibility and wearing comfort of traditional dental materials.

3. Hollow silicone rubber plug design, balancing functionality with lightweight construction.

A custom-made, hollow‑structured occlusion ball is fabricated using a 3D‑printed model; after thermally cured silicone rubber molding, it weighs less, thereby reducing pressure on the oral mucosa. The hollow design provides complete sealing of oronasal fistulas, improving hypernasality and preventing liquid reflux, while preserving the soft‑tissue cushioning properties, ensuring no significant pressure‑induced discomfort even with prolonged wear.

4. Ultra-long-term clinical validation confirms the long-term reliability of the protocol.

Following completion of this prosthetic restoration, a 5-year follow-up was conducted: at 6 months post‑placement, only a simple chairside silicone rubber relining was required to maintain fit; over the 5-year period, no complications such as pain, fracture, or loss of marginal seal were observed. This rare long-term clinical data supports the conclusion that the “3D‑printed digital workflow” delivers stable, durable restorative outcomes.

IV. Technical Limitations and Directions for Future Application Expansion

(1) Existing limitations of the current plan

• This time, a PVC‑layered bonded 3D‑printed model was used, with a printing time of 10–12 hours, resulting in a relatively long processing cycle.
• Only defect‑reference models can be printed; the final, wear‑able restorations cannot be fabricated directly. SLA photopolymerization–based dental‑specific printing materials are limited in variety, and some photosensitive resins pose a risk of mucosal irritation and are difficult to sterilize at high temperatures.
• CT reconstruction has limitations in accurately reproducing soft-tissue surface details and therefore still requires the use of an intraoral final impression to refine the soft-tissue margin morphology.
• The overall cost of digital equipment, software, and printing consumables remains high, making widespread adoption challenging for grassroots dental institutions.

(II) Future Directions for Expanding Clinical Applications

(1) Standardized Reconstruction of Postoperative Defects Following Maxillofacial Tumor Resection

For patients with maxillary and mandibular resections and defects of the soft and hard palate, a standardized clinical workflow has been established—comprising “CBCT rapid scanning, three-dimensional reconstruction, 3D-printed models, and obturator prostheses”—which significantly shortens the postoperative rehabilitation waiting period and addresses the growing demand for reconstructive care in head and neck cancer patients.

(2) Repair of congenital craniofacial deformities

Patients with cleft lip and palate or congenital palatal perforations can utilize 3D-printed models to fabricate child‑specific occlusive prostheses that precisely match the maxillary morphology at each stage of growth and development, enabling staged, personalized orthodontic treatment.

(3) One-stop, fully digital direct printing of restorations

As dental biocompatible photopolymer resins continue to evolve, it will soon be possible to bypass the plaster and silicone rubber impression‑taking steps, enabling direct 3D printing of integrated soft‑lining occlusal restorations. This approach can streamline more than a dozen manual fabrication processes, achieving digital one‑step molding.

(4) Multidisciplinary Collaborative Care Support Tools

3D-printed models can be simultaneously used for preoperative surgical guides in maxillofacial surgery, radiotherapy positioning models, and prosthetic restorations, seamlessly integrating the entire digital workflow from surgery to radiotherapy and rehabilitation, thereby enabling comprehensive, full‑cycle management of cancer patients.

(5) Optimization of Lightweight Digital Solutions for the Grassroots Level

Develop a low-cost CBCT‑compatible, simplified 3D‑printing device; streamline the user interface of 3D reconstruction software; reduce equipment and consumable costs; and enable grassroots dental and maxillofacial clinics to offer digital prosthetic rehabilitation.

Image and Text Guide

Figure 1. Initial condition of the maxillary defect

Figure 2. View of the maxillary defect displayed using Simplant software.

Figure 3. Three-dimensional printed anatomical model of the defect site.

Figure 4. Wax pattern embedding structure for hollow spheres

Figure 5. Schematic diagram of the model’s positioning within the oral cavity.

Figure 6: The final impression with an integrated hollow silicone sphere.

Figure 7: Fabrication of the working model—retentive grooves are visible along the mold edges.

Figure 8: The replication process of the master mold and the silicone encapsulator.

Figure 9. A new working model fabricated using a wax sealant (Figure 9).

Figure 10: Preparation of a transparent acrylic substrate.

Figure 11: Direct lining of the final 3D-printed closed‑body restoration using RTV soft liner material.

Figure 12: The newly fabricated working model printed using a wax sealant (Figure 10); the preparation process for a transparent thermosetting acrylic denture base; and the final 3D-printed closed‑body restoration subjected to direct lining with an RTV soft liner. Five-year post‑fabrication status of the 3D‑printed maxillary impacted tooth root canal preparation (Figure 12A): five-year follow-up results of the 3D‑printed maxillary impacted tooth root canal restoration.