Grammetry vs Photogrammetry in Full-Arch Implant Dentistry: What Is the Difference?

Digital full-arch implant dentistry has introduced a new collection of scanners, scan bodies, verification devices and technical terms. Unfortunately, the terminology has developed almost as quickly as the technology, which means similar-sounding words are sometimes used to describe very different workflows.

Two terms creating particular confusion are grammetry and photogrammetry.

Both methods aim to record the three-dimensional positions of multiple implants or multi-unit abutments accurately. Both can support immediate loading and definitive full-arch restorations. Both are designed to reduce the cumulative errors associated with scanning a completely edentulous arch.

However, they do not capture the information in the same way.

In simple terms, photogrammetry normally uses a dedicated camera system and coded markers to calculate implant positions. Grammetry normally uses specially designed, connected or geometrically distinctive scan bodies with a compatible intraoral scanner.

That difference affects equipment costs, clinical technique, verification, data handling and the laboratory workflow. Understanding it helps a practice choose the right technology rather than investing in a system because it looked impressive at a conference.

First, a note about the terminology
Grammetry is frequently misspelled as grammertry, grammetry or even confused with Grammee, which is the name of a commercial photogrammetry scanner.

This is more than a spelling issue. Grammee is a product that uses photogrammetry, while dental grammetry generally describes a full-arch scanning method that improves intraoral scanner tracking through specialised scan bodies, splinted components or recognisable geometric reference points.

The term grammetry is still relatively new and is not used consistently across every manufacturer, clinician or research paper. Some companies use it for connected scan-body systems. Others apply it more broadly to enhanced full-arch intraoral scanning.

Before comparing two systems, ask what the technology physically does rather than relying on the label printed on the brochure.

What is photogrammetry in implant dentistry?
Photogrammetry calculates the three-dimensional position and angulation of implants by analysing images of calibrated markers from different viewpoints.

Special coded scan bodies or flag-shaped markers are connected to the implants or, more commonly in All-on-X workflows, to the multi-unit abutments. A dedicated photogrammetry camera records these markers and calculates their spatial relationship.

The resulting dataset tells the laboratory:

• Where each implant or multi-unit abutment is positioned
• The angle of each implant connection
• The distance between the implant positions
• The rotational orientation of the restorative interfaces
• The relationship of all recorded implant positions to one another
  
  

Photogrammetry is especially useful in completely edentulous full-arch cases because it does not depend on conventional intraoral scanner stitching across a long area of relatively featureless soft tissue.

Systems such as iCam and other dental photogrammetry platforms are designed specifically for this purpose. Some newer intraoral scanners also incorporate photogrammetric functions, but the underlying principle remains the optical measurement of coded reference markers.

Why can an ordinary intraoral scan struggle with a full arch?
An intraoral scanner does not capture an entire arch in one photograph. It records many small areas and joins them together using a process commonly known as stitching.

This works extremely well when the scanner can recognise stable anatomical features such as teeth, preparation margins, cusps and fissures. A completely edentulous arch presents a more difficult environment.

The scanner may encounter:

• Large areas of smooth, visually similar mucosa
• Saliva and reflections
• Moving cheeks, lips and tongue
• Bleeding around newly placed implants
• Scan bodies that appear almost identical
• Long distances between terminal implants
• Limited stable landmarks between one side of the arch and the other
  
  

A small stitching error at the beginning of a scan can accumulate as the scanner travels around the arch. The individual scan bodies may look correct, while their overall cross-arch relationship is slightly distorted.

That discrepancy may not be obvious on a computer screen. It becomes very obvious when a rigid, screw-retained prosthesis refuses to seat passively.

What is grammetry in dental implant scanning?
Dental grammetry is a method of improving complete-arch implant capture using a conventional or approved intraoral scanner together with a specialised scan-body system.

These components provide the scanner with a continuous, recognisable path across the arch. Depending on the system, the scan bodies may be physically connected, splinted to a framework or manufactured with individual geometric shapes that help the scanner identify each position.

Instead of asking the software to navigate across several isolated and visually similar scan bodies, grammetry creates additional landmarks between them.

Common grammetry principles include:

• Scan bodies with unique shapes or surface geometry
• Extensions that bring adjacent scan regions closer together
• A metal or polymer framework linking the scan bodies
• Luting material connecting the components into a rigid assembly
• Continuous visual references from one terminal implant to the other
• A component that can also function as a physical verification jig
  
  

The aim is to reduce the likelihood of the intraoral scanner losing its position or incorrectly stitching one section of the arch to another.

Grammetry therefore works with the intraoral scanning process. Photogrammetry measures implant positions through a separate optical coordinate-capture process.

The fundamental difference between grammetry and photogrammetry
The easiest way to understand the difference is to ask what is doing the measuring.

With photogrammetry, a dedicated calibrated camera identifies coded markers and calculates their relative coordinates. It is primarily measuring the implant or multi-unit abutment positions.

With grammetry, an intraoral scanner captures specially designed scan bodies and the surrounding reference structure. The extra geometry helps its normal image-stitching process remain stable across the complete arch.

This produces several practical differences.

Photogrammetry usually requires:

• A dedicated photogrammetry device or an intraoral scanner with integrated photogrammetry
• System-specific coded markers
  
• Calibration and a defined capture protocol
• A separate intraoral scan for the soft tissue and prosthetic information
• Accurate alignment of the photogrammetry dataset with the other clinical records
  
  

Grammetry usually requires:

• A compatible intraoral scanner
• A specialised grammetry scan-body kit
• Correct positioning or splinting of the components
• A continuous scanning strategy
• Careful inspection of the complete mesh
• Physical verification when the restoration or clinical risk warrants it
  
  

Neither workflow should be reduced to simply attaching components and pressing scan.

Photogrammetry does not capture everything needed for the restoration
One of the most common misunderstandings is that photogrammetry replaces the complete digital impression. In most workflows, it does not.

Photogrammetry provides highly accurate implant-position data, but the laboratory still needs the other information that defines the prosthesis.

This can include:

• The shape and depth of the soft tissue
• The available restorative space
• The preoperative tooth position
• The approved tooth arrangement
• The opposing dentition
• The occlusal relationship
• The vertical dimension
• The midline, smile line and lip support
• The relationship between the implant coordinates and the patient’s anatomy
  
  

A photogrammetry file without a reliable soft-tissue scan is like receiving excellent directions to an address without knowing what needs to be delivered there.

The photogrammetry dataset must be aligned with an intraoral scan, preoperative scan, provisional prosthesis, duplicate denture, fiducial markers or another stable reference. That alignment is a critical stage, not a minor administrative step.

Can grammetry capture more information in one scan?
One attraction of grammetry is that the intraoral scanner may capture the scan-body assembly and surrounding anatomy within the same digital environment.

That can simplify data organisation and reduce the number of separate datasets requiring alignment. It may also allow the laboratory to produce a physical model using the recorded implant positions, depending on the system and workflow.

However, one scan does not automatically mean one perfect dataset. Blood, saliva, movement, incomplete soft-tissue capture and distorted stitching can still compromise the result.

The operator must confirm that:

• Every scan body is fully seated
• The connections are rigid
• The scanner has captured all required geometry
• There are no duplicated or melted surfaces
• The mesh remains continuous around the arch
• The soft tissue has not obscured the restorative interface
• The left and right terminal positions appear complete
• The bite scan is stable and repeatable
  
  

The apparent simplicity of the workflow should never replace clinical inspection.

Which method is more accurate?
Photogrammetry has a strong reputation for full-arch implant-position capture because it was developed to measure spatial coordinates without relying on a long conventional intraoral scan.

Published research generally supports photogrammetry as a highly precise option for complete-arch implant impressions, particularly when compared with conventional intraoral scanning using separate, unconnected scan bodies. However, results vary between devices, study designs, implant distributions and clinical conditions.

Research into grammetry and enhanced intraoral scanning is developing. Splinted or geometrically optimised scan-body systems can improve full-arch capture, but they do not make every intraoral scanner equally accurate or eliminate every source of error.

Accuracy also has two important components:

• Trueness describes how close the scan is to the actual implant positions.
• Precision describes how consistently the system reproduces the same result when scanning is repeated.
  
  

A system can produce repeatable scans that are consistently wrong, or an accurate scan that is difficult to reproduce. Both measures matter when assessing full-arch technology.

The sensible conclusion is not that one method always wins. Photogrammetry is currently the more established dedicated method for recording multiple implant positions, while grammetry offers an accessible way to improve full-arch capture using an existing intraoral scanner.

What are the advantages of photogrammetry?
Photogrammetry offers several valuable benefits in demanding full-arch cases.

These include:

• Highly accurate recording of implant or multi-unit positions
• Reduced dependence on conventional cross-arch stitching
• Fast implant-coordinate capture
• Good performance across widely separated implants
• Support for immediate-loading workflows
• Reduced risk of distortion from impression material and model production
• Predictable digital transfer into compatible CAD workflows
  
  

It can be particularly useful in edentulous arches, cases with posterior implants, zygomatic or pterygoid implants, and situations where a rigid full-arch restoration requires a very accurate restorative platform.

The limitation is that the equipment may represent a significant investment, and the practice still needs a reliable method of capturing and aligning the anatomical, aesthetic and occlusal records.

What are the advantages of grammetry?
Grammetry can make enhanced full-arch scanning available to a practice without purchasing a separate photogrammetry camera.

Its practical advantages may include:

• Use of an existing compatible intraoral scanner
• Lower initial equipment costs
• Familiar scanning hardware for the clinical team
• Continuous landmarks across an edentulous arch
• Reduced scanner confusion between similar scan bodies
• Capture of anatomy and scan components within a connected workflow
• Reusable components with some systems
• Potential use of the splinted assembly as a verification device

For practices undertaking a moderate number of full-arch cases, grammetry may offer a commercially sensible route into a more controlled digital workflow.

Its success remains dependent on the scanner, scan strategy, rigidity of the components, clinical environment and the operator’s understanding of the complete workflow.

What can go wrong with photogrammetry?
Photogrammetry removes certain errors, but it does not make the case error-proof.
Common problems include:

• A coded marker that is not completely seated
• Contamination preventing accurate marker recognition
• Using the wrong marker or component library
• Movement of a marker during capture
• Failure to calibrate the device correctly
• Incomplete visual access to posterior markers
• Inaccurate alignment with the soft-tissue scan
• An unstable bite record
• Changes to multi-unit abutments after the scan
• Incorrect laboratory interpretation of implant identification

A beautifully accurate implant-position file can still produce the wrong restoration if it is aligned to an inaccurate preoperative scan or incorrect bite.

Every dataset must be considered part of one coordinated record.

What can go wrong with grammetry?
Grammetry introduces its own technique-sensitive stages.
Common mistakes include:

• Scan bodies not fully seated on the multi-unit abutments
• Components touching but not being rigidly connected
• Excess resin covering essential scan geometry
• Polymerisation shrinkage within the splinted structure
• A framework pressing against mobile soft tissue
• Scanning too quickly across the arch
• Failing to capture underneath geometric extensions
• Continuing after the scanner has visibly lost tracking
• Assuming a clean-looking mesh must be dimensionally accurate
• Using an unvalidated scanner, library or component combination
  
  

A duplicated surface, sudden step or blurred area should never be tidied up and ignored. If the scan path has become unreliable, rescanning the affected sequence is safer than hoping the CAD software will understand what happened.

Why passive fit remains the real objective
The purpose of either technology is not to create an impressive digital file. It is to produce a prosthesis that seats passively, supports the intended occlusion and can be maintained predictably.

A lack of passive fit may contribute to:

• Difficulty seating the prosthesis
• Screws loosening
• Uneven screw preload
• Component strain
• Prosthetic fracture
• Patient discomfort
• Time-consuming chairside adjustments
• Remakes and delayed treatment
  
  

No digital method changes the basic mechanical reality of a rigid full-arch restoration. Small positional discrepancies across several implants can create clinically significant strain when connected by one framework.

At Bremadent, we look at the complete chain of information rather than treating the scan as an isolated file. Implant positions, multi-unit details, tissue, bite, tooth arrangement and verification must all agree.

How do these systems affect immediate loading?
In an immediate-loading workflow, time matters, but speed without control simply allows an error to reach the printer faster.

Photogrammetry can provide rapid, accurate implant-coordinate capture immediately after multi-unit abutment placement. Grammetry can create a continuous intraoral scanning pathway and may combine more of the clinical anatomy into the same scanning workflow.

Whichever method is used, the practice should establish a clear sequence before surgery.

A reliable sequence should confirm:

• The planned implant and multi-unit system
• The availability of compatible scan components
• The required tightening protocol
• Who is responsible for scanning each dataset
• How the preoperative position will be transferred
• How the bite and vertical dimension will be maintained
• How files will be named and submitted
• Who checks the records before design begins
• How the provisional restoration will be verified
• What happens if the digital records do not align
  
  

These decisions should not be made while the patient is in the chair and the laboratory is waiting online.

Which system should a dental practice choose?
The correct choice depends on clinical volume, existing equipment, team capability and the level of restorative risk.
Photogrammetry may be more appropriate when:

• The practice performs a high volume of full-arch implant cases
• Maximum confidence in implant-position capture is required
  
• Widely distributed or complex implants are common
• The cost of remakes and delays justifies dedicated equipment
• The team has a defined workflow for merging all associated datasets
  
  

Grammetry may be more appropriate when:

• The practice already owns a compatible, capable intraoral scanner
• Full-arch case volume does not justify a dedicated camera
• The team wants a more controlled alternative to isolated scan bodies
• A physical verification option is valued
• The chosen laboratory supports the specific components and libraries
• The practice is prepared to follow a standardised scanning protocol
  
  

Traditional splinted impressions may still have a place where digital compatibility is uncertain or where clinical conditions prevent reliable optical capture. Digital technology should expand the clinician’s options, not remove sensible fallback methods.

Questions to ask before purchasing either system
A demonstration on a clean model does not reproduce a bleeding, reflective, restricted clinical environment. Before investing, ask questions that test the complete workflow.

Useful questions include:

• Is the system validated for our intraoral scanner?
• Does it work at implant level, multi-unit level or both?
• Which implant and multi-unit platforms are supported?
• Are the components reusable and autoclavable?
• How is the system calibrated?
• What files are exported?
• Is the workflow open or tied to proprietary software?
• Can the laboratory produce an accurate physical model?
• How is the implant dataset aligned with the tissue scan?
• What is the protocol when a marker cannot be seen?
• How is a passive fit verified?
• What training is provided to new operators?
• What evidence supports the manufacturer’s accuracy claims?
• What is the replacement cost for damaged or missing components?
  
  

The most important question is whether your chosen laboratory can receive, interpret and manufacture from the files. Compatibility should be confirmed before the first live patient is booked.

The laboratory needs more than a folder full of STL files
Digital full-arch cases often arrive with several scans named upper, upper new, final upper and final upper actual. This is not a workflow. It is a small detective novel.

Every submission should identify:

• The patient and treatment date
• Implant system and platform
• Multi-unit abutment brand, height and angulation
• Scan-body or photogrammetry component system
• Which file contains the verified implant positions
• Which file contains the soft tissue
• Which file represents the approved tooth position
• The opposing arch and bite record
• The required material and restoration type
• The intended delivery time
• Any intraoperative changes from the original plan
  
  

Clear records reduce design delays and prevent the wrong dataset from being used. File management may not be the glamorous part of digital dentistry, but it is often where predictable outcomes are won or lost.

How Bremadent approaches full-arch digital records
At Bremadent Dental Laboratory, we believe that digital implant workflows must be built around verification, communication and repeatability.

We check whether the implant-position data matches the prescribed system and restorative level. We review the scan for missing surfaces, possible stitching errors and inconsistencies between datasets. We also assess whether the bite, tooth position and available restorative space provide enough information to design the requested prosthesis safely.

If the records conflict, we would rather raise the question before manufacture than discover the problem during fitting.

For practices introducing grammetry or photogrammetry, early planning with the laboratory is valuable. A test model, component check or pilot workflow can identify software, library and file-transfer problems before they affect a live immediate-loading case.

The practical answer: grammetry or photogrammetry?
Photogrammetry uses calibrated optical images and coded markers to calculate implant positions. Grammetry uses enhanced geometry, connected scan bodies or splinted reference structures to help an intraoral scanner capture a complete arch more reliably.

Photogrammetry is a dedicated measurement solution. Grammetry is an enhanced intraoral scanning strategy.
Photogrammetry generally offers the stronger evidence base for highly accurate full-arch implant-position capture. Grammetry may provide a more accessible and scalable option for practices wanting to use their existing intraoral scanner.

Neither method independently guarantees a passive restoration. The final outcome depends on component seating, scanner technique, soft-tissue capture, bite accuracy, dataset alignment, CAD libraries, manufacturing tolerances and effective communication between the practice and laboratory.

Choose the system that your team can perform consistently, verify properly and integrate with the laboratory. In full-arch implant dentistry, repeatability is usually more valuable than owning the latest piece of equipment.

We provide a trusted laboratory service delivering consistent quality, saving chairside time, and supporting predictable patient outcomes.

Do you have a full arch case on the go?

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