STL, OBJ, or PLY? Choosing the Right 3D File Format in Digital Dentistry

As digital dentistry continues to advance, we rely more than ever on accurate 3D data—whether for restorative design, patient communication, or long-term monitoring.  Personally I work with just STL files….. but may be I should change?   Not all 3D file formats are created equal. Understanding the strengths and limitations of STL, OBJ, and PLY files can help you choose the right format for each step of your workflow, reduce friction with your lab, and ensure your software handles your data effectively.

STL: The Workhorse of Digital  Dentistry

STL (stereolithography) has long been the universal standard in dental CAD/CAM and Ortho.  It captures only the geometry of a scan—essentially the shape represented as a triangle mesh.

Why dentists still rely on STL:  

Lightweight and fast to process

Universally supported across scanners, CAD systems, and milling units

Limitations:

STL does not include colour, texture, or surface details beyond raw geometry.

Best for:

Restorative work where clean geometry is all that’s required—crowns, bridges, guides, Ortho and most lab communication.

OBJ: When Colour and Texture Matter

OBJ adds another layer of detail by combining geometry with color and texture. This is done through linked texture files that map surface appearance onto the scan.

Strengths: Preserves colour and texture - helpful for visual evaluation. Useful for patient presentations and aesthetic planning.

Considerations: Requires multiple files (the OBJ plus texture maps)

Not supported as widely as STL in dental CAD software

Best for: Digital smile design, patient previews, case documentation, and any situation where aesthetics matter as much as form.

PLY: Rich Data for Diagnostic and Aesthetic Precision

PLY files capture geometry plus high-density colour information, texture, surface normals, and metadata such as per-point confidence. It’s the most data-rich of the three formats.

Strengths: All visual and geometric data is stored in a single file. Excellent for detailed analysis and long-term patient monitoring.

Considerations. Larger file sizes. Slower to process. Not universally supported across dental CAD platforms.

Best for: Aesthetic analysis, diagnostic cases, documentation, and workflows where precision and visual fidelity are essential.

How to Decide: A Quick Guide

Choose STL when your goal is restorative accuracy and fast, reliable compatibility.

Choose OBJ when you need colour and texture for visualisation or patient communication.

Choose PLY when you want the most detailed, data-rich representation of a patient’s oral structures.

Feature	STL	OBJ	PLY
What It Captures	Geometry only	Geometry + color + texture	Geometry + rich colour + metadata (normals, confidence)
File Size	Small	Medium	Large
Speed / Performance	Fastest	Moderate	Slower
Color Information	None	Yes (via texture maps)	Yes (embedded in file)
Texture Detail	None	Yes	High fidelity
File Management	Single file	Multiple linked files	Single file
Software Compatibility	Excellent / universal	Moderate	Variable
Best For	Ortho retainers/aligners/bonding trays/models.   Restorative workflows (crowns, bridges, guides)	Smile design, patient previews, visual communication	Diagnostics, aesthetic analysis, patient monitoring
Primary Strength	Lightweight, reliable	Color + visual detail	Most comprehensive data
Primary Limitation	No color/texture	Requires multiple files	Large size + slower processing