An intraoral scanner is a handheld device that generates digital impression data of the oral cavity. The scanner's light source is projected onto the scan items, such as whole dental arches, and a 3D model processed by the scanning software is then shown in real-time on a touch screen.
Types of intraoral scanners
Intraoral scanners in dentistry come in various types, each with unique features. Here are some common types:
Optical Scanners: Use light to capture images of the oral cavity. Examples include the iTero and 3Shape TRIOS. Laser Scanners: Utilise laser technology for precise measurements and can provide high-resolution 3D images.. Video Scanners: Capture continuous video footage, which is then processed to create a 3D model. Hybrid Scanners: Combine multiple technologies (e.g., optical and laser) to enhance accuracy and speed.
Features of an intraoral scanner:
Accuracy: Essential for minimising errors and reducing the need for retakes. Higher accuracy leads to better fitting restorations and fewer patient visits. Speed: Fast scanning improves patient comfort and decreases lab turnaround times. Example: Primescan can complete a full arch scan in under a minute. Ease of Use: User-friendly scanners require minimal training and integrate smoothly into existing workflows. Price: Prices have become more competitive, making scanners more accessible. Consider long-term savings and return on investment when comparing costs. Integration with Existing Workflows: The scanner should enhance efficiency by reducing repeat impressions and improving treatment times. Software Compatibility: Look for scanners with open software that easily connects with your lab's systems. Primescan supports connections to major lab CAD software for seamless data sharing.
What do patients think about intraoral scanners:
Based on 9 studies, Participants generally reported more positive experiences with intraoral scanners regarding smell, taste, sound, vibration, nausea, and queasiness, leading to a preference for digital methods in terms of comfort. However, there was no significant difference in anxiety levels between the two approaches. The studies also showed mixed results when it came to how participants perceived the time taken for each method.
How does it work? With the use of high-resolution cameras, the intra-oral scanner can record dental arches, implants, and their dimensions by projecting a light beam—either structured light or laser—onto the surface of the teeth. It can also record the distortion that occurs when the beam strikes these structures. This is made possible by the distortion that occurs when the instrument's beam strikes the different structures inside the oral cavity. The cameras record this distortion, which is then emphasised in the 3D model using specialised software.
A physical representation of the scanned material will be produced by first creating a sort of tracing of points from which a triangulation between these points, or mesh, will be built. The final 3D model that will be formed will represent the virtual structure of the patient's oral cavity in both shape and size.
Digital intraoral scanners, which are built and manufactured in compliance with ANSI/IEC 60601-1 requirements, are classified as Class I medical electrical devices. A computer monitor to enter prescriptions, approve scans, and review digital files; a wireless mobile workstation to facilitate data entry; and a portable camera wand to gather scan data in the patient's mouth are the three main parts of every scanner. Energy from either laser or white light is projected from the wand onto an item and reflected back to a sensor or camera inside the wand in order to collect surface data points Tens or hundreds of thousands of measurements are made every inch using algorithms, producing a three-dimensional (3D) representation of the object's shape.
The scanner's measurement speed, resolution, and accuracy are determined by the technology the wand uses to collect surface data. There are now four different kinds of imaging technologies in use:
Using projected laser light, triangulation, which is employed in CEREC4, calculates the angles and separations from known sites. Both the angle between the laser and the sensor and the distance between the laser source and the sensor are known. According to the Pythagorean theorem, the system calculates the angle of reflection when light bounces off the item, and consequently, the distance between the laser source and the object's surface. The target tissue must be covered with a thin layer of opaque powder in order for this technology to produce consistent and reliable light dispersion.
Laser light is projected onto the target tissue via a filtering pinhole in parallel confocal imaging. Any light coming from above or below the plane of focus is blocked by a tiny aperture in front of the sensor, which is positioned at the confocal (in-focus) imaging plane in relation to the target. The accuracy of the scan is maximised because only focused light that reflects off the target tissue will pass through the filter and reach the sensor for processing; out-of-focus light, or faulty data, is removed. The "point-and-stitch reconstruction" method uses a parallel confocal system to tomographically slice the object and stitch together thousands of slices of data to get a whole image. Accordion fringe interferometry (AFI) projects three "fringe patterns" of light using two light sources on the tooth and tissue.
Depending on the object's particular curvature, a fringe design will distort and take on a different pattern as it touches the surface. "Fringe curvature" is the term used to describe this distortion in the fringe pattern. An HD video camera, positioned approximately 30° away from the projector, records surface data points of the fringe curvature. Changes in tooth colours and materials have no effect on the differential measurement since the distance is determined by the discrepancies between the three precision optical readings.
An HD video camera with trinocular imaging—three tiny video cameras at the lens—captures three exact views of the tooth for three-dimensional in-motion video. Behind the cameras, a complementary metal-oxide semiconductor (CMOS) sensor transforms light energy into electrical signals.
The 3D data, which are recorded in a video series and modelled in real time, are determined by concurrently calculating the distances between two data points from two angles. In contrast to the heavier coating needed for triangulation, only a little dusting is necessary to capture surface data points. Unlike the slower point-and-stitch reconstruction of surface data, both AFI and 3D in-motion video imaging use HD video cameras instead of a sensor to quickly acquire images in real time. Because of their greater dynamic range of luminosity, AFI scanners can scan reflective objects without the need for powder coating.
Basic principles Intraoral scanning is a digital dentistry technique that creates precise 3D models of the mouth's hard and soft tissues. The process consists of several key steps, each contributing to the final digital model used for treatment planning and manufacturing.
1. Scanning Process: The scanning process begins with the intraoral scanner capturing real-time data through a light source, such as a laser or structured light, which projects patterns onto the tooth surface. As the scanner moves around the mouth, the reflected light is recorded, creating a continuous stream of data. This allows the clinician to obtain a digital representation of the oral cavity quickly.
2. Data Acquisition: The scanner continuously gathers data points as it moves around the oral cavity, recording the surface details of the teeth and soft tissues, providing the foundational data for creating the 3D model. The real-time data acquisition allows the clinician to view the scanning progress and make adjustments if needed.
3. 3D Model Generation: Once the data is captured, specialised software processes the data points and assembles them into a high-resolution 3D model of the patient's dental anatomy. This model includes detailed representations of the teeth, gums, and surrounding tissues, allowing for precise analysis and planning. The 3D model can be rotated and zoomed in on, providing a detailed view for clinical examination.
4. Editing and Validation: After generating the 3D model, it is edited and validated in real-time. Clinicians can refine areas that may have been inadequately captured or check for errors in the data. Some scanners have built-in validation tools that automatically detect incomplete scans or inaccuracies, helping to ensure a complete and accurate model.
5. Application in CAD/CAM: The validated 3D model is then imported into computer-aided design (CAD) software, where it can be used for designing restorations such as crowns, bridges, or orthodontic appliances. The digital model can be sent directly to computer-aided manufacturing (CAM) systems.
Laser-Based Triangulation in Intraoral Scanners The triangulation method is a commonly used imaging technology in intraoral scanners. This technique involves projecting a fringe pattern onto the surfaces within the oral cavity . The system calculates the 3D coordinates by measuring the angles and distances between multiple points, typically using a light source and two or more detectors. As the scanner collects data from multiple angles, it constructs a digital model by identifying the exact position of each point. Triangulation-based scanners have become essential in digital dentistry workflows, allowing for accurate measurements and detailed 3D representations of dental structures, aiding in procedures such as prosthetic design and orthodontic assessments.
The triangulation method operates on the geometric principles of triangulation, which involves using the positions of two known points and the angles between them to calculate the location of a third, unknown point. In the context of intraoral scanning, a light source projects a structured pattern, such as a grid or stripe, onto the surface of the teeth. The scanner then uses two or more sensors or cameras positioned at specific angles relative to the light source to capture how this pattern deforms over the three-dimensional surface of the teeth and gums. By analysing these deformations, the scanner software can precisely calculate the coordinates of each point on the tooth surface, creating a highly accurate 3D representation of the dental structures
Intraoral scanners vs conventional way of taking impression The use of digital impressions has changed prosthodontics, enabling a more precise and faster method for recording intraoral information. Digital scanners: Though first marketed in the early 2000s, technology developments from the late 1980s have now made digital scanners much smaller, more economical, and omnipresent. The significant benefits of this approach include increased precision, decreased patient anxiety, quicker restoration time and an improvement in the communication protocols with colleagues in different fields as well as digital sharing with patients for better interactive learning. There has been a significant change in processes that have enabled the streamlining of workflows and providing efficient treatment.
The advantages and disadvantages of optical impressions with respect to conventional physical impressions (i.e. impressions made with trays and materials) are presented below and summarized in the table below: Advantages DisadvantagesLess patient discomfort Difficulty detecting deep marginal lines of prepared teeth Time efficient Learning curve Simplified clinical procedures Purchasing and managing costs Better communication with the dental technician Better communication with patients No more plaster casts
Are optical impressions as accurate as conventional impressions?