Digital Orthodontics: Intraoral Scanning and 3D Workflow in the Lab and Clinic

The transition from the plaster model to the three-dimensional digital model — obtained through direct intraoral scanning or model scanning — is one of the most significant infrastructural changes in contemporary orthodontic practice. This transition isn't purely technological: it changes the clinical workflow, communication with the lab, treatment planning possibilities, and record archiving. Understanding its practical implications is essential for any professional wanting to integrate these tools into their practice.

Intraoral scanners (IOS) currently used in orthodontics — Align Technology's Itero Element 5D, 3Shape TRIOS 5, Dentsply Sirona's Primescan, Medit i700 — all operate through optical triangulation or confocal imaging technology that captures thousands of frames per second, reassembling them into a three-dimensional mesh through point cloud registration software. Clinically relevant dimensional accuracy has two components: local accuracy (shape fidelity in a limited area, typically measured in micrometers) and global accuracy (error accumulation over the whole arch, measured as average deviation across the entire surface). Flügge et al.'s systematic research (2018) documented that IOS produce an average global error of 170-250 μm over full arches — significantly greater than local error (30-60 μm) — but clinically acceptable for most orthodontic applications.

The integrated digital orthodontic workflow includes: digital acquisition of the arches with IOS; digital occlusal registration at maximum intercuspation; transfer of digital models to planning software (Rhinoceros 3D, 3Shape Ortho Analyzer, OrthoSelect's Maestro); cephalometric and model analysis; communication to the lab via STL/OBJ/PLY files; 3D printing of study or working models in light-curing resin; fabrication of aligners, splints, and thermoformed retainers on the printed model. Every step introduces a source of error that must be minimized through specific quality protocols.

3D printing of orthodontic models — through SLA (Stereolithography), DLP (Digital Light Processing) or LCD printers — has practically eliminated plaster from the digitally integrated orthodontic practice. The quality of printed models depends on printer resolution (layer thickness 25-100 μm, XY resolution 35-100 μm), resin quality (certification for dental lab use, color, transparency), and print parameters (model orientation, supports, post-curing). Resins for orthodontic models must be ISO 10993 certified for indirect biocompatibility and guarantee dimensional accuracy ≤100 μm on occlusal surfaces.

Managing STL file flow in communication with orthodontic labs requires standardized naming protocols, file resolution (mesh density), and a coordinate reference system for orientation. The absence of these standards — still common in many clinical settings — creates incompatibility between the practice's scan and the lab's software, resulting in loss of accuracy or the need to redo the impression. The AMF (Additive Manufacturing File) format — STL's successor with support for color and multiple materials — is increasingly adopted but not yet universal.

IOS has also changed orthodontic record management. Digital models have unlimited lifespan, don't degrade, take up no physical space, can be sent instantly and are retrievable at any time. Privacy regulation (GDPR) requires that scan data — containing potentially identifying biometric information — be handled with the same precautions as health data: secure servers or certified cloud, anonymization when possible, defined retention periods. Backing up STL data must be systematic: losing the digital archive without a backup is equivalent to losing all plaster models.