Overview of the basic scanning process used by intraoral scanners:
The basic scanning process used by intraoral scanners
Intraoral scanners use a handheld wand that is moved around the mouth to capture images of the teeth and surrounding tissues. The tip of the scanner wand contains optic components including:
Laser, structured light, or other illumination source
Lenses, mirrors and sensors to measure distortions
As the scanner tip is slowly dragged along the teeth, it projects a laser or structured light pattern onto the surfaces while rapidly capturing images. The scanning software analyzes the pattern distortions picked up by the sensors to map out the contours and textures of the teeth in 3D.
Hundreds or thousands of images are taken from slightly different angles as the scanner moves around the mouth. Advanced processing algorithms analyze this image stream data to stitch and blend the images together into a seamless 3D model.
The scanner software accounts for any irregularities in movement or positioning, using accelerometer and gyroscope data to align the images properly. This allows even novice users to get accurate scans without needing perfectly steady hand motions.
Once fully processed, the scan data file can be exported as an open STL file or proprietary file format. CAD software then allows the 3D model to be used for various applications like creating surgical guides, crowns, aligners and more.
So in summary, intraoral scanners use a wand to capture a video-like stream of images that are automatically converted by sophisticated software into a detailed 3D model of the oral anatomy. This digital impression can then be utilized for a variety of dental treatments and appliances.
Basic scanning patterns
Basic scanning patterns used with intraoral scanners:
To fully capture the teeth and oral anatomy, the scanner wand must be moved around the mouth in a careful, methodical pattern. Proper wand motion is important to effectively stitch together the many images into an accurate model.
For upper teeth, it’s recommended to start scanning from the posterior teeth and slowly progress forward. The wand tip should follow the curve of the arch, staying in close contact with the teeth and just slightly angled toward the occlusal plane.
For lower arches, the same posterior-to-anterior pattern is used, scanning the lingual side of the teeth. The wand is inverted but still held at a slight angle toward the occlusal.
The motion should be slow, smooth, and steady as the scanner acquires a constant stream of images. Abrupt movements or lifting the scanner off the teeth can disrupt the scanning process.
The wand is like a video camera, capturing frames constantly from every vantage point. So overlapping scanning from multiple angles helps improve detail and accuracy. Difficult-to-reach areas may require special positioning.
Bite registration requires holding the wand still while the patient closes into occlusion, to link the upper and lower dental arches together. Motionless scanning may also be used for small isolated areas.
With practice, the scanning patterns become second nature. While software can compensate for imperfections, proper technique is key for the most accurate digital impressions.
How powders and opacifying agents are used with intraoral scanners:
Intraoral scanners are devices used in dentistry to capture digital impressions of the teeth and oral structures for various dental procedures, such as crown and bridge fabrication, orthodontic treatment planning, and more. The use of powder or opacifying agents can enhance the performance of intraoral scanners by creating contrast and improving the scanning process. Here’s how:
Many intraoral scanners rely on projecting light patterns onto the teeth’s surface to capture details. However, the natural translucency and reflective properties of dental enamel can make it difficult for the scanner sensors to accurately detect the light patterns.
To improve the contrast and scanning efficiency, a fine powder is often applied to the teeth prior to scanning. These powders are designed to temporarily coat the teeth with an opaque, non-reflective layer.
The powder particles scatter the projected light uniformly across the surface, eliminating glare spots. This creates a high contrast image that the scanner can easily recognize and map.
Titanium dioxide or aluminum oxide powders are commonly used. They can be delivered with an integrated powder blower on the scanner wand or applied with a separate applicator.
After scanning, the powder is simply rinsed or air-sprayed away, leaving no residue behind on the teeth.
Some newer intraoral scanners use alternate technologies like fluorescence or polarized imaging to achieve contrast without powder. But many systems still benefit from the use of an opacifying powder for optimal precision and speed.
So in summary, scanning powders are a key way to improve the accuracy of intraoral scanners by temporarily coating the teeth to make surface details clearly visible and scannable.
Reducing Reflectivity
Intraoral scanners use light to capture the surface of teeth and surrounding tissues. The presence of saliva, blood, or reflective surfaces can interfere with the accuracy of the scan. Powder or opacifying agents, often in the form of a fine spray or powder, are applied to the teeth to reduce reflectivity. This helps to create a more consistent surface for the scanner to capture.
Enhancing Surface Detail
The powder or opacifying agent helps to coat the tooth surface, making fine details more visible and distinct. This is particularly important for capturing intricate features of the teeth, such as occlusal anatomy, margins, and surface irregularities. The improved contrast allows the scanner to pick up subtle variations in tooth structure more effectively.
Improving Scanning Efficiency
Applying a powder or opacifying agent can make the scanning process more efficient by reducing the need for repeated scans. Improved contrast and detail recognition help the scanner to quickly and accurately capture the necessary information, saving time for both the dental professional and the patient.
Patient Comfort
Some patients may experience discomfort or a gag reflex during intraoral scanning. The application of powder can help to alleviate these issues by creating a smoother surface and reducing friction between the scanner tip and the teeth. This can contribute to a more comfortable and tolerable scanning experience for the patient.
5. Preventing Fogging
In certain situations, intraoral scanners may be prone to fogging due to moisture in the oral environment. Powder acts as a desiccant, absorbing excess moisture and preventing fogging on the tooth surface. This is especially beneficial when scanning in challenging conditions or when dealing with patients who produce excessive saliva.
It’s important to note that not all intraoral scanners require the use of powder or opacifying agents. Some modern scanners are designed to perform well without additional aids. However, in cases where conditions are suboptimal, or when enhanced contrast and detail are crucial, the use of these agents can be a valuable adjunct to the scanning process. Dental professionals should follow the manufacturer’s guidelines and recommendations when using powder or opacifying agents with specific intraoral scanners.
Projecting light/lasers and capturing the distortion with sensors
Intraoral scanners utilize advanced optical technologies, including the projection of light or lasers onto dental surfaces, coupled with sophisticated sensors, to capture detailed digital impressions of the oral cavity. This process involves the projection of structured light or lasers onto the teeth and surrounding structures, and the subsequent analysis of the distortion or deformation of this projected pattern to create a three-dimensional digital model. Here’s how this technology typically works:
Light Projection
Intraoral scanners often use structured light or laser projection systems to illuminate the surfaces being scanned. Structured light involves projecting a known pattern of light onto the dental structures. Lasers, which emit coherent and focused beams of light, are also commonly employed.
Pattern Deformation
As the projected light or laser pattern encounters the surfaces of the teeth, it undergoes deformation based on the contours and topography of the dental structures. The way the light pattern distorts provides information about the shape, size, and spatial orientation of the scanned surfaces.
Capture by Sensors
The deformed light pattern is captured by a set of highly sensitive sensors integrated into the intraoral scanner. These sensors are designed to rapidly and accurately record the changes in the projected pattern caused by the geometry of the oral structures.
Triangulation and Depth Calculation
The scanner relies on a principle known as triangulation. By comparing the known pattern projected onto the surfaces with the deformed pattern captured by the sensors, the system can calculate the three-dimensional coordinates of numerous points on the dental surfaces. This process is repeated rapidly and continuously as the scanner is moved around the oral cavity.
Real-time Processing
The captured data is processed in real-time by powerful computing algorithms. These algorithms analyze the distortion patterns and generate a highly accurate three-dimensional digital representation of the teeth and soft tissues within the oral environment.
Creation of Digital Models
The processed data is then used to construct a digital model of the patient’s teeth, gums, and surrounding structures. This digital model can be manipulated, analyzed, and used for various dental applications, such as crown and bridge design, orthodontic treatment planning, and more.
Advantages of using light or lasers in intraoral scanners include:
Accuracy
The use of structured light or lasers allows for highly accurate and detailed scans, capturing even intricate surface features of the teeth.
Speed
The technology enables rapid data capture, contributing to efficient scanning procedures.
Non-invasiveness
Intraoral scanning with light or lasers is non-invasive, providing a more comfortable experience for patients compared to traditional impression methods.
Real-time Feedback
Dental professionals can receive real-time feedback during the scanning process, ensuring that comprehensive data is acquired.
In summary, the integration of light projection and sensor technology in intraoral scanners represents a cutting-edge approach to digital impression-taking in dentistry, offering improved accuracy, efficiency, and patient comfort.
Generating multiple images from different angles
Intraoral scanners generate multiple images from different angles through a process known as multi-view imaging. This technique involves capturing images of the oral cavity from various perspectives to create a comprehensive and detailed three-dimensional representation. Here’s an overview of how intraoral scanners achieve this:
Multiple Cameras or Light Sources
Intraoral scanners are equipped with multiple cameras or light sources strategically positioned within the scanning device. These cameras or light sources are arranged to capture images from different angles simultaneously.
Structured Light or Laser Projection
Many intraoral scanners use structured light or laser projection systems. These systems project a known pattern of light or laser onto the surfaces being scanned. The pattern deformation, as explained in the previous response, is captured by multiple cameras at different angles.
Simultaneous Image Capture
As the light pattern is projected onto the teeth and oral structures, the cameras capture the deformed patterns from their respective angles. This simultaneous image capture is crucial for obtaining a comprehensive view of the entire oral cavity.
Coordinate Alignment
The intraoral scanner’s software aligns and merges the images captured from different angles into a cohesive and accurate three-dimensional representation. This process involves matching corresponding points in each image to create a seamless and complete digital model.
Real-time Processing
The captured images are processed in real-time by powerful algorithms within the scanner. These algorithms analyze the images, identify common points, and use triangulation methods to determine the spatial relationships and distances between these points.
Continuous Scanning
Intraoral scanners are designed to be moved continuously throughout the oral cavity during the scanning process. This movement, combined with the simultaneous capture of images from different angles, allows for a comprehensive and continuous data acquisition.
Feedback and Visualization
The software often provides real-time feedback to the operator, displaying the evolving digital model as the scanning progresses. This feature enables the dental professional to ensure that all necessary areas are adequately scanned and that the data is of high quality.
The advantages of generating multiple images from different angles include:
Comprehensive Coverage
Multi-view imaging ensures that all surfaces of the teeth and surrounding structures are captured, resulting in a more complete digital model.
Enhanced Accuracy
By incorporating information from various perspectives, intraoral scanners can improve the accuracy of the final digital impression.
Efficiency
Simultaneous image capture and real-time processing contribute to a more efficient scanning process, reducing the time required for data acquisition.
Better Visualization
The ability to visualize the digital model in real-time allows the dental professional to identify and address any potential issues during the scanning procedure.
In summary, the generation of multiple images from different angles is a key feature of intraoral scanners, contributing to their accuracy, efficiency, and ability to provide comprehensive digital impressions of the oral cavity.
Conversion of images into 3D rendering by software
The conversion of 2D images into 3D rendering by software involves a process known as 3D reconstruction. This process is commonly used in various fields, including computer vision, medical imaging, computer-aided design (CAD), and more. Here’s a general overview of how this conversion is typically accomplished:
Image Acquisition
– Initial images, usually taken from different perspectives or angles, serve as the input data for the 3D reconstruction process.
– The images may be captured by cameras, scanners, or other imaging devices, and they often represent different views of the same object or scene.
Feature Extraction
– The software identifies and extracts key features or points from the 2D images. These features could include corners, edges, or other distinctive elements that can be matched across multiple images.
– Feature extraction is essential for establishing correspondences between points in different images, forming the basis for the subsequent 3D reconstruction.
Correspondence Matching
– Matching algorithms are employed to find corresponding points in different images. These algorithms aim to establish how features in one image relate to those in another.
– Common techniques for correspondence matching include feature matching using descriptors (like SIFT or SURF) or dense matching methods.
Triangulation
– Triangulation is a geometric process that uses the information from corresponding points in multiple images to calculate the 3D coordinates of those points in space.
– By triangulating the matched points, the software determines the depth or distance of each point from the imaging devices.
Surface Reconstruction
– Once the 3D coordinates of points are established, the software can create a surface mesh that represents the object or scene.
– Various algorithms, such as Delaunay triangulation or marching cubes, can be used to generate a mesh connecting the points and forming a continuous surface.
Texture Mapping (Optional)
– If the original images contain texture information, such as color or intensity, this information can be mapped onto the 3D model to enhance its visual realism.
– Texture mapping helps in creating a more visually detailed and realistic 3D rendering.
Post-Processing and Refinement
– Additional post-processing steps may be applied to refine the 3D model. This can include smoothing the surface, reducing noise, or filling in missing data.
Visualization
– The final 3D model can be visualized using appropriate software. Visualization tools allow users to interact with and explore the reconstructed 3D scene or object.
This process is widely used in various applications, from reconstructing 3D models of objects for virtual reality to generating anatomical models from medical imaging data. The specific algorithms and techniques employed can vary based on the application and the characteristics of the input data.
Stitching images together into a complete model.
Stitching images together into a complete model involves combining multiple images, often overlapping or taken from different viewpoints, to create a seamless and comprehensive representation of a scene or object. This process is commonly used in panoramic photography, medical imaging, computer vision, and other fields. Here’s a general overview of how image stitching is typically achieved:
Image Alignment
– Before stitching, it’s crucial to align the images properly. This involves adjusting the position, rotation, and scale of each image to ensure that corresponding features match accurately across multiple images.
– Feature-based methods, such as matching key points or corners, are often employed for precise alignment.
Feature Matching
– Feature matching involves identifying distinctive points or patterns in overlapping regions of adjacent images. These features act as anchor points for aligning the images.
– Common feature matching techniques include using descriptors like SIFT (Scale-Invariant Feature Transform) or SURF (Speeded-Up Robust Features).
Homography Estimation
– The relationship between corresponding features in two images is described by a mathematical transformation called homography. This transformation encapsulates the translation, rotation, and scaling needed to align the images accurately.
– Algorithms such as RANSAC (Random Sample Consensus) are often employed to estimate the homography robustly, especially when dealing with outliers or errors in feature matching.
Image Warping
– Once the homography is determined, each image is warped or transformed to align with the reference image. This involves applying the calculated transformation to every pixel in the image.
– Common methods for image warping include bilinear interpolation or more sophisticated techniques to preserve image quality.
Blending
– Blending addresses the transition areas between stitched images, ensuring a smooth and visually cohesive result. Overlapping regions are often blended to eliminate noticeable seams.
– Techniques like feathering or multi-band blending are used to gradually blend pixel values at the boundaries.
Global Optimization (Optional)
– In some cases, a global optimization step may be applied to refine the stitching by considering the entire set of images simultaneously. This helps improve the overall alignment and coherence of the stitched model.
Post-Processing
– Post-processing steps may include color correction, contrast adjustment, and removal of artifacts to enhance the visual quality of the stitched image or model.
Output
– The final stitched model, often in the form of a panoramic image or a larger composite image, is the output of the stitching process. This model represents a seamless integration of the input images.
Image stitching techniques can vary based on the specific requirements of the application, the characteristics of the input images, and the desired output format. Advanced software tools and libraries, such as OpenCV or Adobe Photoshop, often provide functionalities for image stitching.
Why do scanners often use white or blue light for accuracy?
Intraoral scanners often use white or blue light for accuracy due to several reasons related to the optical properties of these wavelengths and their interaction with dental surfaces. Here are some key reasons:
Optimal Scattering Properties
– White and blue light have shorter wavelengths compared to other colors, making them ideal for capturing fine details. Shorter wavelengths result in better scattering properties, allowing the light to interact with the surface features of teeth and soft tissues more effectively.
– The scattering of light helps in capturing intricate surface details, such as the anatomy of teeth, margins, and other important structures.
Improved Depth Perception
– Shorter wavelengths, like those in the blue spectrum, can provide better depth perception. This is crucial for accurately capturing the three-dimensional structure of the dental surfaces.
– The ability to perceive depth accurately is essential for creating precise digital models that reflect the true anatomical characteristics of the oral cavity.
Reduced Reflection and Glare
– White or blue light is less prone to reflection and glare compared to longer wavelengths. Reflections and glare can interfere with the accuracy of the scan by creating unwanted highlights or shadows.
– By using light with wavelengths that are less susceptible to reflection, intraoral scanners can produce clearer images and reduce the likelihood of errors in the scanning process.
Color Differentiation
– White light encompasses a broad spectrum of colors, allowing for better color differentiation. This can be important in dentistry, where distinguishing subtle color variations on the tooth surface or identifying anomalies is essential.
– Blue light, specifically, is often chosen for its ability to enhance the contrast between the scanned surfaces and the surrounding tissues.
Less Heat Generation
– White and blue light generally generate less heat compared to some other light sources. This is advantageous when the intraoral scanner is in close proximity to sensitive oral tissues. Minimizing heat generation helps ensure patient comfort and safety during the scanning process.
Compatibility with Optical Sensors
– Intraoral scanners often use optical sensors to capture the reflected light and generate the digital impression. White and blue light are well-suited for the sensitivity and spectral response of these optical sensors, contributing to accurate and reliable data capture.
Clinical Considerations
– White and blue light are commonly used in dental clinical settings, and intraoral scanners designed to work with these light sources align with existing clinical practices. This ensures compatibility with established workflows and lighting conditions in dental offices.
While white and blue light is frequently used, it’s worth noting that advancements in technology may lead to the development of intraoral scanners that leverage different wavelengths or combinations of colors to further enhance accuracy and performance. The choice of light source is a critical design consideration for intraoral scanners, and manufacturers carefully select the optimal wavelengths based on their advantages for dental applications.
IR cameras and gyroscope/accelerometer data were utilized.
In addition to using visible light sources for imaging, some advanced intraoral scanners incorporate additional technologies such as infrared (IR) cameras and sensors like gyroscopes and accelerometers to enhance their performance. Here’s how these technologies are utilized:
IR Cameras
– Infrared cameras are sometimes integrated into intraoral scanners to capture information beyond what is visible to the human eye.
– IR imaging can be particularly useful for capturing surface details or features that may not be as clearly visible under visible light. It can enhance the overall accuracy of the digital impression by providing complementary data.
– IR imaging is often combined with visible light data to create a more comprehensive and detailed representation of the oral structures.
Gyroscope and Accelerometer Data
– Gyroscopes and accelerometers are motion-sensing devices that measure the orientation and acceleration of the scanner in real time.
– Intraoral scanners may utilize this data to track the movement and position of the scanner during the scanning process. This information is crucial for accurately mapping the spatial relationship between the captured images or point clouds.
– Real-time tracking helps the scanner software to dynamically adjust and align the captured data, ensuring that the 3D model accurately represents the actual orientation and position of the scanned surfaces.
Dynamic Image Registration
– The data from gyroscope and accelerometer sensors can be used for dynamic image registration. This involves continuously aligning and registering the incoming images based on the real-time movement and orientation of the scanner.
– Dynamic image registration contributes to the creation of a seamless and accurate 3D model, even when the scanner is moved rapidly or in complex trajectories.
Reduction of Artifacts
– Gyroscope and accelerometer data can aid in the reduction of motion artifacts. Motion artifacts, caused by the movement of the scanner during the scanning process, can negatively impact the accuracy of the final digital impression.
– By compensating for motion in real-time, these sensors help mitigate artifacts, resulting in a cleaner and more accurate representation of the scanned surfaces.
Improved User Experience
– Integration of gyroscopes and accelerometers enhances the overall user experience by providing real-time feedback to the operator. Dental professionals can monitor the movement and alignment of the scanner during the scan, ensuring that all areas are adequately covered.
– This real-time feedback contributes to more efficient and effective scanning procedures.
The combination of visible light imaging, infrared technology, and motion sensors helps create a robust and accurate intraoral scanning system. These technologies work synergistically to capture precise 3D data of the oral structures, reduce errors related to motion, and enhance the overall usability and performance of intraoral scanners in clinical settings.
Stereophotogrammetry triangulation process
Stereophotogrammetry is a technique used to obtain three-dimensional information about objects or scenes by analyzing images captured from multiple viewpoints. The process involves triangulation, where the position of a point in 3D space is determined by measuring its projections onto two or more images. Here’s a step-by-step description of the stereophotogrammetry triangulation process:
Image Acquisition
– Stereophotogrammetry starts with the acquisition of at least two images of the object or scene from different viewpoints. These images should overlap to ensure common features are visible in both views.
Calibration
– Before triangulation, the camera parameters must be calibrated. Calibration involves determining the intrinsic parameters of the camera, such as focal length, principal point, and lens distortion. This step is crucial for accurate triangulation.
Feature Matching
– Corresponding features in the overlapping images are identified. These features can include points, corners, or other distinctive patterns that can be easily matched between images.
– Feature matching is typically done using computer vision techniques, and algorithms such as SIFT (Scale-Invariant Feature Transform) or SURF (Speeded-Up Robust Features) are commonly employed for this purpose.
Epipolar Geometry
– Epipolar geometry describes the geometric relationship between two views of the same scene. It defines the epipolar lines, which are the intersection lines between the image planes and the epipolar plane.
– The epipolar geometry helps constrain the search for corresponding points, making the matching process more efficient.
Triangulation
– Triangulation is the key step in stereophotogrammetry. Given corresponding points in two or more images and the known camera parameters, the 3D coordinates of a point in the scene can be calculated.
– The triangulation process involves extending lines from the camera centers through the corresponding points in each image and finding the intersection point in 3D space. The intersection point is the triangulated point.
Bundle Adjustment (Optional)
– Bundle adjustment is an optimization process that refines the camera parameters and 3D coordinates simultaneously. This step helps improve the overall accuracy of the 3D reconstruction by minimizing errors in the triangulation process.
Generation of 3D Model
– Once triangulation is complete, a dense set of 3D points is obtained, representing the surface of the object or scene. These points can be further processed to create a 3D mesh or point cloud, providing a detailed representation of the geometry.
Texture Mapping (Optional)
– If the images include color information, texture mapping can be applied to project the color information onto the 3D model, enhancing its visual realism.
Stereophotogrammetry is widely used in various fields, including photogrammetry, computer vision, and 3D reconstruction. It is an essential technique for applications such as topographic mapping, cultural heritage documentation, and creating 3D models for virtual reality or augmented reality environments.
Steps for calibrating the scanning wand before use.
Calibrating the scanning wand before use is a critical step in ensuring the accuracy and reliability of the data captured by the intraoral scanner. Calibration compensates for any variations or distortions in the scanner’s measurements, making the subsequent scans more precise. Here are the general steps for calibrating a scanning wand:
Power On the Scanner
– Start by turning on the intraoral scanner and any associated hardware, such as the imaging unit or control console.
Prepare Calibration Tool or Target
– Most intraoral scanners come with a calibration tool or target. This could be a specially designed pattern or object with known dimensions. Ensure that the calibration tool is clean and free of any debris that could affect the calibration process.
Place the Calibration Tool in the Field of View
– Position the calibration tool within the scanner’s field of view. Make sure it is well-illuminated and that the scanner has a clear line of sight to the entire calibration tool.
Initiate Calibration Mode
– Access the scanner’s calibration mode or calibration settings. This might involve navigating through the scanner’s user interface or software.
Follow on-screen Instructions
– The scanner will typically provide on-screen instructions to guide you through the calibration process. This may include prompts to place the calibration tool in specific positions or orientations.
Capture Calibration Images
– During the calibration process, the scanner captures images of the calibration tool from various angles. The goal is to record how the scanner’s optics and sensors perceive the known geometry of the calibration tool.
Analysis and Adjustment
– The scanner’s software analyzes the captured calibration images and compares them to the expected positions and dimensions of the calibration tool. If any discrepancies are detected, the software may make adjustments to the scanner’s internal parameters to correct for errors.
Verify Calibration Accuracy
– After the calibration process is complete, some scanners provide a verification step. This involves scanning a verification tool or a known reference object to ensure that the calibration has been successful.
Document Calibration Results
– It’s good practice to document the results of the calibration, including any adjustments made and verification outcomes. Some scanners may automatically generate a calibration report that you can save for reference.
Regular Calibration Checks
– Periodically check and recalibrate the scanner to maintain accuracy. The frequency of calibration checks may vary depending on the manufacturer’s recommendations, usage patterns, and environmental conditions.
Calibration Quality Assurance
– Some advanced intraoral scanners include built-in quality assurance features. These features may involve regular self-checks or alerting the user if the scanner detects any deviations from expected performance.
Following these steps helps ensure that the intraoral scanner is calibrated accurately before each use, contributing to the precision of digital impressions and the overall success of dental procedures. Always refer to the manufacturer’s guidelines and documentation for specific calibration instructions for your intraoral scanner model.
Intraoral scanners use advanced optical technology to capture thousands of images per second while scanning the inside of a patient’s mouth. These images are then stitched together to create a precise 3D model.
Intraoral scanners eliminate the need for traditional dental impressions, which can be uncomfortable for patients. They also provide highly accurate digital models for various dental procedures, such as crowns, bridges, and aligners.
While intraoral scanners are incredibly versatile, they may not be suitable for every dental procedure. Your dentist will determine the best approach based on your specific needs.