How is 3D printing related to dental models?

I’m trying to understand how 3D printing is used in dentistry, specifically when it comes to creating dental models. Is it replacing traditional methods completely? What are the main benefits and drawbacks compared to plaster models? I’m particularly interested in the workflow – how does a dentist go from a patient’s mouth to a 3D printed model? Does it require special equipment or software? Are the materials used for 3D printed dental models as accurate and durable as plaster? And finally, is it cost-effective for smaller practices to invest in 3D printing for this purpose? I’ve heard about intraoral scanners playing a role, but I’m not exactly sure how they fit into the process.

Answer

3D printing has revolutionized the field of dentistry, and its application in the creation of dental models is one of the most significant advancements. Here’s a detailed explanation of the relationship between 3D printing and dental models:

Traditional Methods vs. 3D Printing:

Traditionally, dental models were fabricated using a process involving physical impressions taken of a patient’s teeth and surrounding oral structures. These impressions, typically made of materials like alginate or polyvinyl siloxane (PVS), were then poured with dental stone (plaster) to create a positive replica of the patient’s dentition. This method, while reliable for many years, is labor-intensive, time-consuming, and prone to inaccuracies due to material shrinkage, distortion during pouring, and human error. It also requires significant storage space for physical models.

3D printing offers a digital workflow that overcomes many of these limitations.

The 3D Printing Workflow for Dental Models:

The modern digital workflow using 3D printing involves these steps:

1. Intraoral Scanning or Extraoral Scanning:

   • Intraoral Scanners (IOS): A wand-like device is used inside the patient’s mouth to directly capture a digital impression of the teeth and gums. This eliminates the need for physical impression materials. The scanner uses optical or laser technology to create a highly accurate 3D image of the oral cavity in real-time.
   • Extraoral Scanners: In some cases, a conventional physical impression is taken. This impression or a stone model created from the impression is then scanned using a desktop or laboratory scanner. The scanner captures the surface geometry of the physical object and converts it into a digital 3D model.

2. Digital Model Design and Software: The scanned data is imported into specialized dental CAD (Computer-Aided Design) software. This software allows dental technicians or dentists to:

   • Refine and optimize the digital model.
   • Segment the scan to isolate specific areas of interest (e.g., individual teeth).
   • Design and add bases, articulation structures, and other features necessary for a functional dental model.
   • Prepare the model for printing by optimizing its orientation and generating support structures if needed.
   • Integrate the model with other digital information, such as CBCT scans for surgical planning.

3. 3D Printing: The designed digital model is then sent to a 3D printer. Common 3D printing technologies used in dentistry include:

   • Stereolithography (SLA): SLA printers use a laser to selectively cure liquid resin layer by layer. This technology produces highly accurate and detailed models.
   • Digital Light Processing (DLP): DLP is similar to SLA but uses a projector to cure an entire layer of resin at once, making it faster.
   • Material Jetting: This technology deposits tiny droplets of resin that are then cured by UV light. Material jetting can produce multi-material models with varying properties.
   • Fused Deposition Modeling (FDM): While less common for high-precision dental models, FDM printers extrude thermoplastic filaments layer by layer. It is used for some aligner models and other applications where extreme precision isn’t critical.
4. Post-Processing: After printing, the dental model typically requires some post-processing. This may include:
   • Removing support structures.
   • Washing the model to remove uncured resin (especially for SLA and DLP).
   • Curing the model under UV light to fully harden the resin.
   • Polishing or finishing the model to achieve the desired surface texture and aesthetics.

Applications of 3D Printed Dental Models:

3D printed dental models are used for a wide variety of dental applications, including:

• Orthodontics:

  • Fabrication of aligner models for clear aligner therapy (e.g., Invisalign). 3D printing allows for the creation of multiple models representing different stages of tooth movement.
  • Indirect bonding trays for orthodontic bracket placement.
  • Study models for treatment planning and case presentation.

• Restorative Dentistry:

  • Working models for the fabrication of crowns, bridges, veneers, and inlays/onlays.
  • Diagnostic models for treatment planning and wax-ups.
  • Models for implant planning and surgical guides.

• Prosthodontics:

  • Models for the fabrication of dentures and removable partial dentures.
  • Master casts for complex prosthodontic cases.

• Surgical Planning:

  • Models for pre-surgical planning of implant placement, orthognathic surgery, and other oral and maxillofacial procedures. These models can be combined with CBCT data for enhanced visualization.
  • Surgical guides for precise implant placement or bone resection.
• Patient Education:
  • Accurate and visually appealing models for educating patients about their treatment options and procedures.

Advantages of 3D Printed Dental Models:

• Improved Accuracy: Digital workflows reduce the potential for errors associated with traditional impression techniques and stone pouring.
• Increased Efficiency: 3D printing automates the model fabrication process, saving time and labor.
• Enhanced Predictability: Digital design allows for precise control over the model’s dimensions and features, leading to more predictable treatment outcomes.
• Digital Storage: Digital models can be stored electronically, eliminating the need for physical storage space. They can also be easily duplicated and shared.
• Faster Turnaround Times: 3D printing can significantly reduce the time it takes to produce dental models, allowing for faster treatment delivery.
• Cost-Effectiveness: While the initial investment in 3D printing equipment can be significant, the long-term cost savings can be substantial due to reduced material costs, labor costs, and storage costs.
• Improved Patient Experience: Intraoral scanners eliminate the need for messy and uncomfortable physical impressions.

Materials Used for 3D Printing Dental Models:

Various types of resins and other materials are used for 3D printing dental models, each with its own specific properties and applications. These include:

• Resins:

  • Standard resins: General-purpose resins suitable for a wide range of dental models.
  • Model resins: High-precision resins designed specifically for creating accurate and detailed models.
  • Surgical guide resins: Biocompatible resins approved for use in surgical guides.
  • Thermoformable resins: Resins that can be thermoformed, making them suitable for aligner models.
  • Flexible resins: Used for applications requiring some degree of flexibility, such as soft tissue models.
• Other Materials:
  • Thermoplastic Filaments (PLA, PETG): Used in FDM printing, primarily for less critical applications.

In summary, 3D printing has revolutionized the creation of dental models, offering a more accurate, efficient, and predictable alternative to traditional methods. It has become an indispensable tool in modern dentistry, enabling a wide range of applications in orthodontics, restorative dentistry, prosthodontics, and surgical planning. The ongoing advancements in 3D printing technology and materials are expected to further expand its role in the future of dentistry.