A simplified digital workflow using a modified 3D printed anatomical tray with LEGO plates as occlusal rims for digital complete denture fabrication

Technical Summary: A Simplified Digital Workflow for Complete Denture Fabrication

Problem Statement
The fabrication of conventional complete dentures (CD) is traditionally a time-consuming and labor-intensive process requiring multiple clinical and laboratory visits. While Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) technology has introduced digital workflows that utilize intraoral scanning (IOS) and reduce physical laboratory work, significant challenges remain. Specifically, recording accurate maxillomandibular relations in completely edentulous patients is difficult due to the absence of stable vertical stops and reliable anatomical landmarks. Existing digital solutions, such as specialized occlusal rims and anatomical measuring devices (AMD), often face limitations regarding high costs, regional unavailability, and technical complexity. Furthermore, purely digital impressions can struggle to capture the viscoelasticity of soft tissues, potentially leading to inaccurate sulcus depth and border molding compared to conventional functional impressions.

Methodology
The authors propose a simplified, low-cost, and time-efficient digital workflow that integrates 3D printing with modified anatomical trays (MAT) and commercially available LEGO building plates to serve as occlusal rims. The workflow is structured across three clinical visits:

1. Fabrication of Modified Anatomical Trays (MAT):

   • Ready-made anatomical trays (Xanlgin Tray Set 1) are scanned using an intraoral scanner and exported as STL files.
   • Using Blender for Dental (B4D) software, a 2mm thick record base is created from the tray STLs.
   • Free STL files of LEGO unit bricks (3001) and plates (3020) are imported. For the mandibular arch, the plates are positioned on the posterior ridge crest (16–18 mm height) with the hollow side up. For the maxillary arch, plates are attached to the anterior labial flange (20–22 mm height) with a slight labial inclination.
   • The modified trays and additional LEGO plates are fabricated using a high-precision SLA 3D printer and C&B resin.

2. First Clinical Appointment (Impression and Jaw Relation):

   • An appropriate MAT is selected and borders are adjusted with green compound.
   • A functional impression is made using polyvinyl siloxane (PVS). Alternatively, an intraoral scan can be performed, utilizing added PVS in the anterior tray area as a "stitching point" for superimposition.
   • LEGO plates are used to establish the midline and occlusal plane. Vertical dimension and centric relation are recorded by having the patient close onto the plates, adjusting the number of plates as needed.
   • Bite registration material (Occlufast+) is applied to the LEGO plates to capture the centric relation.
   • The trays are removed as a single unit, scanned, and the STL file is exported.

3. Digital Design and Second Clinical Appointment (Try-in):

   • The scanned MAT STL is imported into B4D software. Maxillary and mandibular models are generated. If an intraoral scan was used, it is aligned with the MAT STL using the impression material as a reference.
   • Denture bases and teeth are designed using the midline and occlusal plane markings on the MAT as guides. Occlusal interferences are removed digitally.
   • Trial dentures are printed and presented for a try-in to verify aesthetics, occlusion, and vertical dimension.
   • If modifications are required, the trial dentures are rescanned, and the design is updated.

4. Third Clinical Appointment (Delivery):

   • Final denture bases and teeth are printed using permanent resins (Asiga DentaBASE and DentaTOOTH).
   • The teeth are bonded to the base using the same resin, followed by final curing.
   • The dentures are delivered to the patient.

Key Contributions

• Cost-Effective Innovation: The study introduces the use of LEGO plates as a reusable, low-cost alternative to expensive proprietary occlusal rims and bite registration devices.
• Hybrid Workflow Integration: The technique successfully bridges the gap between conventional functional impressions (which ensure tissue accuracy) and digital design, allowing for accurate jaw relation records in the first visit.
• Reduced Clinical Visits: The workflow aims to reduce the fabrication process to three clinical visits, a significant reduction compared to conventional methods, while maintaining the ability to make modifications during the try-in phase.
• Reproducibility: The use of standardized 3D-printed trays and modular LEGO components allows for a reproducible technique adaptable to various edentulous arch shapes and sizes.

Results and Claims
The paper presents this technique as a descriptive report of a clinical workflow rather than a quantitative comparative study with statistical results. The authors claim that this method allows clinicians to:

• Accurately and consistently make impressions and record jaw relationships in the first clinical visit.
• Achieve denture delivery by the third visit.
• Overcome the limitations of pure intraoral scanning regarding soft tissue viscoelasticity by incorporating functional impressions.
• Reduce the overall cost of the digital workflow through the reusability of the 3D-printed trays and LEGO plates.

Significance
The authors position this technique as a practical solution to make digital complete denture fabrication more accessible and efficient for daily dental practice, particularly in regions where expensive commercial CAD/CAM systems are unavailable. By simplifying the recording of maxillomandibular relations, the workflow aims to elevate patient care and minimize the physical and temporal burdens of denture fabrication. The paper concludes that while the technique shows promise, further scientific evidence and evaluative studies are required to fully validate its reproducibility and accuracy.