Intraoral scanners convert the physical surfaces of teeth and gingiva into accurate digital 3D models using precision optical technology. Understanding the core principles behind these systems is essential for evaluating performance metrics and expanding clinical applications.
The three mainstream intraoral optical scanning (IOS) technologies today are confocal imaging, structured light, and active stereo vision.
Confocal Imaging
Confocal imaging uses optical sectioning to generate high-resolution images by selectively illuminating and detecting light from a specific focal plane. The scanner captures each sharply focused layer point-by-point or line-by-line, then computationally stacks these optical slices into a complete 3D model.
How it works: A focused light source (typically a laser or precisely collimated LED) illuminates a tiny point or line on the tooth surface. Light reflected from the exact focal plane passes through a pinhole aperture to a photodetector. Out-of-focus light is rejected because it arrives out of phase and is largely blocked. This selective filtering ensures only in-focus data is measured. The system rapidly raster-scans the focused light across the surface and at different depths. Software then reconstructs the independent focused data points into a 3D model-often described as "point-by-point stitching" or optical sectioning acquisition.
Light source: Laser (coherent point source) or collimated LED array.
Data acquisition: Point-by-point or line-by-line raster pattern, linking intensity measurements to corresponding x, y, z coordinates.
Depth resolution: Excellent depth resolution with minimal image distortion and outstanding fine-detail capture-particularly valuable for preparation margins.
Depth of field (DOF): Inherently shallow due to optical sectioning. This delivers high precision within the focal plane but requires careful operator technique (consistent working distance and scan-head angle) when capturing deep grooves or interproximal areas.
Hardware characteristic: Presence of moving optical components. An internal lens assembly performs rapid reciprocating motion, producing a distinctive "whoosh" or humming sound during scanning.
Representative products: 3Shape TRIOS series, Align Technology iTero Element series.
Notable innovation: 3Shape TRIOS 6 integrates hyperspectral technology that projects white light, fluorescence emission, and near-infrared wavelengths. This enables realistic color fidelity and enhanced geometric reconstruction during high-speed acquisition. Color accuracy has improved noticeably compared with TRIOS 5.
Structured Light
Imagine projecting precise straight grayscale stripe patterns onto a crumpled piece of paper. The stripes bend and deform according to the surface topography. By analyzing the captured deformed patterns, the system calculates the three-dimensional shape. Structured-light scanners perform this process at high speed, rapidly projecting a sequence of coded patterns to build a detailed 3D model.
How it works: A structured-light projector casts predefined optical patterns (parallel stripes, grid arrays, or complex coded patterns) onto the object (teeth and gingiva). Cameras positioned at calibrated angles and distances capture the deformed patterns. Using triangulation principles and the known projector-camera geometry, the system computes the 3D coordinates (X, Y, Z) of surface points from the measured pattern deformation.
Cameras: One or more digital cameras (typically CMOS or CCD sensors). Resolution, frame rate, and optical quality directly influence overall performance and measurement accuracy.
Scanning speed: High-speed capability. Each pattern projection and image-capture cycle covers a large surface area, enabling rapid full-arch scans.
Hardware characteristic: No moving optical components. Slow-motion smartphone video often reveals multi-line or grid patterns being projected. Typical systems use a dual-lens configuration-one dedicated to projection, one to imaging.
Representative IOS brands: Alliedstar, Shining 3D, Medit, Dexis, and Aident (AI-30 series).
Key strengths of the structured-light route: Modern implementations deliver high-density point clouds, excellent surface detail, and strong performance on reflective tooth surfaces when equipped with adaptive illumination.
Aident AI-30, for example, employs advanced structured light technology to achieve ≤10 μm full-arch accuracy, powder-free true-color scanning, intelligent anti-fog heating, 20–25 mm ultra depth of field, and ≥30 fps imaging. At only 156–198 g, it ranks among the lightest handpieces available, reducing operator fatigue while supporting an open STL/PLY/OBJ workflow that integrates seamlessly with major CAD software and Aident's dental 3D printers for a complete Scan → Design → Print solution.
Active Stereo Vision
Human binocular vision works by combining slightly offset views from each eye to perceive depth. Active stereo vision scanners operate similarly, using two or more cameras as digital "eyes." To improve feature detection on smooth surfaces such as enamel, these systems typically project a random light texture (high-density random dots or subtle grid patterns). The artificial texture provides unique visual markers that the cameras can match across their fields of view. Calibrated camera geometry and triangulation then produce sub-millimeter-accurate 3D reconstruction.
How it works: Two or more synchronized cameras arranged in a calibrated stereo setup capture offset views of the object. An active projector casts unstructured or semi-structured patterns (natural speckles, pseudo-random dots, or diffuse patterns) onto the oral surface because natural enamel often lacks sufficient texture for reliable matching. Software solves the correspondence problem by identifying homologous points across camera views with the help of the projected texture. Triangulation using known camera parameters yields dense 3D surface coordinates.
Cameras: Two or more high-fidelity CMOS cameras with precision optics. Resolution, frame rate, and low-distortion lenses determine data accuracy.
Light projector (active illumination): Generates artificial surface texture rather than encoding geometric data (unlike structured light). This reduces dependence on the object's natural texture.
Motion sensitivity: Can be more sensitive to patient movement or operator hand tremor, although high frame rates and software motion-compensation algorithms mitigate the effect.
Texture handling: Excellent on smooth, glossy, or featureless surfaces such as edentulous ridges.
Computational demand: Real-time stereo matching requires significant processing power (onboard modules or a capable host computer).
Hardware characteristic: Slow-motion video typically shows irregular spatial distribution of light points in the projection field.
Representative products: iTero Lumina, Langcheng DL 300.
Notable innovation: iTero Lumina's Multi-Direct Capture™ technology places six scanning modules at the tip of the scan head, offering a wider field of view and up to 25 mm scanning distance. This helps capture complex anatomy (narrow/deep palates, edentulous ridges, partially erupted teeth) with fewer maneuvers. Operator distance and motion sensitivity still require careful technique on some systems; other active-stereo implementations focus on improved handling of these variables.
Choosing the Right Technology for Your Practice
Each technology has distinct strengths:
Confocal systems excel in depth resolution and fine margin detail.
Structured-light systems typically offer high speed, large coverage per frame, and robust performance when combined with adaptive optics and open ecosystems.
Active stereo vision provides strong results on low-texture surfaces and increasingly wider fields of view.
For clinics and labs prioritizing a complete digital workflow, open data formats, lightweight ergonomics, powder-free true-color scanning, and seamless integration with design and 3D printing, structured-light solutions such as the Aident AI-30 deliver a practical balance of clinical performance and total cost of ownership.
Ready to experience modern intraoral scanning in your practice? Explore the Aident AI-30 and full Scan → Design → Print solutions at https://www.aident3d.com/. Request a quote or book a live demo today.
