How Digital Waxup Conversion Works in All-on-X

On the day of full-arch surgery, everything converges on one step: the prosthesis design the patient already approved has to become a fixed, screw-retained provisional that seats passively on implants that didn’t exist that morning. That step is the conversion — and it has a reputation for being the longest, messiest part of the appointment.

This article walks through what a digital conversion actually does between “implants placed” and “prosthesis on the printer”: the records it needs, how software brings them into a single coordinate frame, and why the exported file has to be watertight before a printer will accept it.

What “conversion” means in All-on-X

In a conventional workflow, conversion is done chairside with acrylic: temporary cylinders are attached to the multi-unit abutments (MUAs), the denture or try-in is relieved and drilled, and the cylinders are picked up in cold-cure resin while the patient holds still. The prosthesis then goes to the bench for hours of trimming, hole patching, and polishing before it can be delivered.

A digital conversion replaces the acrylic pickup with CAD. The implant positions are recorded digitally, the approved design is modified in software around those positions, and the result is printed or milled. The clinical goal is identical — a passive, screw-retained provisional that preserves the approved tooth positions and vertical dimension — but the mechanism changes from resin shrinking around cylinders to geometry edited in a coordinate frame.

The three records a digital conversion needs

Every digital conversion, whatever the software, is built from the same three ingredients:

• The approved prosthesis design. The waxup, try-in, or denture STL that defines tooth positions, occlusal plane, and the vertical dimension the patient signed off on. This file is the esthetic and functional contract — the conversion should change how it attaches, not how it looks.
• A post-placement tissue record. An intraoral or desktop scan of the arch after surgery, showing the healed or sutured tissue the prosthesis will sit against. Depending on technique, this record may be captured with a splint, jig, or the try-in itself in place so it can be related back to the approved design.
• An implant-position record. Scanbodies seated on the MUAs and captured with an intraoral scanner, a scan jig, or a photogrammetry unit. This record is what determines whether the finished prosthesis seats passively — errors here become misfit at delivery.

The quality ceiling of the whole conversion is set by these records. No design step downstream can recover implant positions that were captured wrong, which is why scanbody systems are validated individually rather than assumed interchangeable — see the supported systems list for the combinations verified with RapidArch.

Step 1 — bring every record into one frame

Each scan arrives in its own arbitrary coordinate system. The first thing conversion software does is registration: matching shared geometry between records — splint surfaces, unchanged anatomy, scanbody geometry against a library model — until the approved design, the tissue, and the implant axes all sit in a single frame.

This is the step that quietly decides the outcome. A registration error of a few hundred microns at the scanbodies becomes rocking or a non-passive screw seat at the arch. Good software makes the residual alignment error visible and asks you to confirm it rather than hiding it; good records give the algorithm enough overlapping, unchanged surface to lock onto.

Step 2 — edit the prosthesis around the implants

With everything in one frame, the design edits are mechanical and repeatable:

• Screw-access channels are punched through the prosthesis along each MUA axis, sized for the driver and prosthetic screw.
• The intaglio is established — the tissue-facing surface is trimmed to the planned level and shaped for hygiene access, replacing the flanges a removable try-in carried.
• Cylinder or ti-base seats are cut where the restorative connection requires them.

Under the hood these edits are Boolean operations: the software subtracts channel and seat geometry from the prosthesis solid, or intersects it with a keep-volume. Done robustly, every cut comes out already sealed — which matters for the next step.

Step 3 — export a watertight file

A printable STL must be manifold: a closed surface where every edge is shared by exactly two triangles, with no holes, slivers, or self-intersections. Slicers either reject non-manifold meshes or, worse, fill them unpredictably — a hairline gap at a screw channel can print as a blocked channel or a void in the intaglio.

This is why “close holes” exists as a step in traditional CAD packages, and why modern conversion tools favor Boolean-based editing that produces watertight geometry by construction instead of patching holes after the fact. If your export needs a repair pass in a separate tool before it slices, something upstream left the mesh open.

What the digital route changes on surgery day

The practical differences most teams notice first:

• Chair time shifts to print time. The design edit takes minutes; the patient can rest (or the team can turn the room over) while the provisional prints.
• The design persists. If a provisional fractures next week, you reprint the same file instead of rebuilding an acrylic pickup from scratch.
• The records document the case. Scans, implant positions, and the delivered design stay on file for the definitive restoration later.

The honest trade-off: a digital conversion is only as good as its scans. A rushed scanbody capture or a tissue record with too little unchanged anatomy for alignment will cost more time than it saves.

A pre-conversion checklist

1. Confirm your scanbody and MUA combination is validated with your conversion software before surgery day.
2. Seat scanbodies fully and torque per the manufacturer — verify radiographically if seating is in doubt.
3. Capture generous overlap: include unchanged anatomy (palate, retromolar pads, adjacent structures) that alignment can lock onto.
4. Keep the approved try-in design file exactly as approved — esthetic changes belong in a revision step, not mid-conversion.
5. Export scans without post-processing that re-meshes or re-orients them; conversions align raw records best.

Where to go next

If you want to see a conversion rather than read about one, the New User Page has step-by-step video tutorials for each RapidArch workflow — including a ten-second conversion, start to finish. When you’re ready to try one on your own case, the editor runs entirely in your browser.