Every new client we onboard eventually asks a version of the same question: what is the actual difference between a modification and a revision, and why does it matter? It is a fair question, because the distinction affects both your workflow and your invoice, and getting it right means your team can request changes at the right time without unnecessary cost or delay.
A modification is a change requested before a case has been approved. A revision is a change requested after a case has already been approved, where new STL files need to be uploaded as a result. That single line covers most of what you need to know, but the practical implications are worth walking through.
While a case is still in the review stage, before your team has clicked approve, you can request as many changes as you need at no additional cost. This is true at every pricing tier, from Pay As You Go through Enterprise. Typical modification requests include adjusting attachment placement, changing IPR values between specific teeth, modifying the staging sequence, or asking for a different approach to a particular movement.
Many of these changes do not even need to go through a formal request. Our built-in web editor lets your team make minor adjustments directly, including attachment edits, IPR changes, and individual tooth movement tweaks such as rotation, torque, and tip, all from your browser, without raising a request and without it counting as a revision.
Once a case has been approved, it moves toward manufacturing or final delivery. If, after that point, your team determines that new STL files are needed, for example because a new scan has been taken or the clinical situation has changed, that request is treated as a revision. Revisions are billed per occurrence, but package clients on Basic, Growth, Premium, and Enterprise tiers receive a 40% discount off their standard tier rate.
Why the distinction exists: approval marks the point where a case moves into production planning. Changes after that point involve re-doing work that has already been finalized, which is why they are treated differently from pre-approval refinements.
Say your team reviews a treatment plan and wants the IPR between two molars adjusted slightly, and would also like an attachment repositioned on a canine. If the case has not yet been approved, both of these can be handled as free modifications, either through a request or directly via the web editor. If the case was already approved last week and a new scan now shows the patient's bite has shifted slightly, requiring updated staging based on new STL files, that would be billed as a revision.
Understanding this distinction up front helps your team plan case reviews efficiently and avoids any surprises on your monthly invoice.
