Guide · Full-arch
Full-arch framework try-in: how to check passive fit
How to run a framework try-in on a full-arch implant bridge: the Sheffield one-screw test, verification jigs, radiographs and what to do if it won't seat.
Short answer
A framework try-in is the appointment where you screw the full-arch bar, or a verification jig, onto the abutments before the definitive prosthesis is made. The Sheffield one-screw test tightens a single terminal screw and looks for gaps at the other abutments; a radiograph confirms. If the bar doesn't seat passively, it doesn't get teeth.
Step by step
- 01
Agree on the try-in when the case is opened
Settle with the lab what goes into the mouth before the definitive: a verification jig, the bar itself or a rigid prototype, and at which stage. You're done when the order states which try-in is planned and what happens after it.
- 02
Check the abutments first
Remove the provisional and check every multi-unit abutment: torqued to the manufacturer's value, platform clean, no tissue caught. A try-in on a poorly seated abutment flags a misfit that isn't the bar's.
- 03
Seat the bar without screws and press each side
Seat the bar by hand and press down on one side, then the other. Rocking, or saliva bubbling at an interface, means misfit. It passes when the bar sits still with no screws in.
- 04
Run the one-screw test from both ends
Tighten only the screw on one terminal abutment and inspect the other interfaces, with loupes and an explorer wherever the margin is visible. It passes when none of them shows a gap. Remove it and repeat from the opposite end.
- 05
Tighten the screws one at a time
With every screw in place, tighten them one by one, starting with the abutment closest to the midline. In the classic criterion, a screw that needs more than an extra half turn after first resistance signals misfit; the figure depends on your system's thread pitch.
- 06
Radiograph the subgingival interfaces
Where the bar-abutment junction sits below the tissue, take a periapical radiograph with the beam perpendicular to it. With the beam angled, a small gap disappears from the image.
- 07
Record the result on the case
Note the result of each test abutment by abutment, by tooth position, and attach the radiographs. If the bar passed everything, the case moves on to the teeth; if not, it gets no veneering until there's a new record.
What is a framework try-in, and why does it come before the teeth?
A framework try-in is the chairside check of passive fit on a full-arch implant bridge: the bar is screwed onto the abutments and examined before any teeth or gingiva go on it. Passive fit means the bar seats on every abutment at once, with no strain. If it only seats because the screws pulled it down, that strain stays in the bar and the components.
The try-in exists because no record of implant positions is right every time. Harfagar and colleagues (Clinical Implant Dentistry and Related Research, 2025) followed 20 edentulous arches with four or six implants. Frameworks made from the intraoral scan and from the conventional impression both passed the one-screw test in 17 of 20 cases, and even the reference record, measured on a coordinate measuring machine, failed twice.
This guide picks up where our full-arch scanning guide leaves off. That one covers the scan sequence and scan body errors; this one covers the chairside check before the definitive is made. If it’s the finished prosthesis that won’t seat on delivery day, that’s a different problem with a different workup: see full-arch bridge not seating at delivery.
What do you need before the try-in?
Before a framework try-in, have what you need to read passive fit with more than one test: the system’s driver and torque wrench, loupes, an explorer, a film holder and your abutment list by tooth position. Kan and colleagues (The Journal of Prosthetic Dentistry, 1999) concluded that no single clinical test gives an objective result, and suggested combining several.
Agree with the lab, when the case is opened, on what goes into the mouth. It can be a verification jig, the bar itself or a rigid prototype; how they differ is covered below, and each one fits a different stage of the case.
Which tests show whether the bar fits passively?
At the try-in appointment, passive fit is read with five chairside tests, and each one sees part of the problem. The review by Buzayan and Yunus (The Journal of the Indian Prosthodontic Society, 2014) describes all five, building on Kan and colleagues. It also mentions disclosing media and 3D measurement.
| test | how | what signals misfit | limit | source |
|---|---|---|---|---|
| Alternating finger pressure | bar with no screws; press one side, then the other | rocking; saliva bubbling at an interface | doesn’t measure the gap, only misfit big enough to rock the bar | Buzayan and Yunus (2014) |
| Direct vision and explorer | loupes and explorer tip at each visible interface | a step or gap at the margin | supragingival margins only; a new explorer tip is about 60 µm | Buzayan and Yunus (2014) |
| One-screw (Sheffield) test | one screw tightened on a terminal abutment, then from the other end | a gap at the unscrewed abutments | only as good as what you can see, or the radiograph | Buzayan and Yunus (2014); Harfagar et al. (2025) |
| Screw resistance test | tighten one by one, starting closest to the midline | a screw needing more than an extra half turn after first resistance | the half turn assumes a 300 µm thread pitch, which not every system uses | Buzayan and Yunus (2014) |
| Periapical radiograph | beam perpendicular to the bar-abutment junction | a dark line at the interface | with an angled beam, small gaps vanish | Sharkey et al. (2011) |
Beam angle decides what a radiograph shows. In an in vitro study by Sharkey and colleagues (The International Journal of Oral & Maxillofacial Implants, 2011), gaps of 12.7 µm were reliably seen with the beam up to 5° off perpendicular. At 15°, reliable detection took a 51 µm gap.
How much of a gap is acceptable at try-in?
There is no single accepted figure for misfit at try-in. Kan and colleagues (1999) call the proposed levels of passive fit empirical, and Buzayan and Yunus (2014) found no consistent value or range in the literature. What clinicians use instead are thresholds quoted in reviews and figures from lab studies.
The 2025 review by Pozzi and colleagues (Clinical Implant Dentistry and Related Research) cites misfit under 150 µm and angular deviation up to 1° as generally enough to avoid complications such as screw loosening and fracture. The authors add that tolerance shrinks as more implants are joined, and that fabrication alone can leave gaps of 20 to 100 µm.
Eid and colleagues (BMC Oral Health, 2026) tested titanium bars on a four-implant model with the terminal screw at 15 Ncm. At the other three abutments, the mean gap was 49 µm for milled bars and 44 µm for printed ones, and the authors rated both clinically acceptable. A gap that size is smaller than a new explorer tip, which is why a combination of tests beats the naked eye.
What happens if a bar with misfit gets screwed down?
A bar screwed down with misfit loads the components and the bone around the implants, which in theory leads to technical and biological complications. In the systematic review by Katsoulis and colleagues (European Journal of Oral Implantology, 2017), two clinical studies showed a slightly higher risk of screw-related complications, while bone loss caused by misfit was not confirmed.
The evidence is thin: five human and five animal studies, measured different ways, with no meta-analysis possible. The authors don’t read that as permission to accept misfit; they recommend aiming for the least misfit you can get. That’s the job of the try-in, before the bar gets its teeth.
Verification jig, bar try-in or prototype: what’s the difference?
A verification jig, a bar try-in and a rigid prototype all check the same thing, the implant positions, at different points in the case. The jig checks the record before the bar exists. The bar try-in checks record and fabrication together. The prototype puts the design of the definitive into the mouth as a rigid piece.
| try-in | what goes into the mouth | when | what it checks | source |
|---|---|---|---|---|
| Verification jig | a rigid index joining the implants in their recorded positions, in resin or milled from the file | before the bar is made | whether the impression or scan captured the right positions | Papaspyridakos et al. (2011); Sinada and Papaspyridakos (2021) |
| Bar try-in | the titanium bar itself, no teeth yet | once the bar is made, before veneering | record and fabrication together | Harfagar et al. (2025); Eid et al. (2026) |
| Rigid prototype | a rigid interim piece made from the same design as the definitive | before the definitive, including monolithic zirconia with no bar | passive fit of the final piece before it’s made | Pozzi et al. (2025) |
Papaspyridakos and colleagues (The International Journal of Oral & Maxillofacial Implants, 2011) used verification jigs joined in the mouth to make the master casts for 13 arches. The one-piece zirconia prostheses fit on every one, on the cast and in the mouth; with nonsplinted impressions, only 6 of 13 fit accurately.
A jig isn’t foolproof. In an in vitro study by De La Cruz and colleagues (The Journal of Prosthetic Dentistry, 2002), with three implants, jigs made in three different resins were no more accurate than impressions. For resin splints, Buzayan and Yunus (2014) describe sectioning between the copings with a thin disc and rejoining the segments in small increments to offset shrinkage.
Sinada and Papaspyridakos (Journal of Prosthodontics, 2021) describe the digital version: a jig designed and milled from the digital record, tried in before two monolithic zirconia full arches. It’s a case report, not a comparative study. Which of these try-ins your case gets, and when, is agreed with the lab when the case is opened.
What do you do when the bar won’t seat at try-in?
When the bar won’t seat at try-in, don’t keep tightening to pull it down: whatever strain the screw overcomes stays in the bar and the components. Step back, separate abutment problems from record problems, and only accept the bar once it passes the tests.
| what the try-in shows | where the cause usually is | what to do |
|---|---|---|
| Bar rocks or won’t seat on one abutment | loose or poorly seated abutment, or tissue caught | retorque the abutment, clean the platform and repeat the try-in |
| A gap at one or more abutments on the one-screw test, abutments checked | an implant position recorded wrong, from the scan body or the coping | don’t accept the bar; take a new record: a jig joined in the mouth, a new scan or an impression |
| A screw turning past the half turn after first resistance | the screw is pulling the bar into place | stop tightening and treat it as misfit, even with no visible gap |
| An unclear radiograph | beam angled to the interface | repeat with the beam perpendicular before you decide |
| A verification jig that won’t seat | a wrong record, or the jig itself distorted | section the jig between abutments, rejoin the segments in the mouth and send it to the lab |
The table pairs the tests described by Buzayan and Yunus (2014) with the jig joined in the mouth from Papaspyridakos and colleagues (2011). Once there’s a new record, a bar made on the old one is no longer a reference: agree the next step with the lab and try in again before the teeth. If the scan bodies are the suspect, the common errors are in our full-arch scanning guide.
What should you note on the case after the try-in?
After a framework try-in, note the result of each test abutment by abutment, by tooth position, and attach the radiographs and photos. That tells the lab whether the bar moves on to the teeth or the record needs redoing, without guessing which abutment failed.
In the Smile Digital Lab portal, messages and files stay inside the case with date, time and author, so the try-in result sits with the order; the portal screens are in Portuguese. The bar on its own is on the milled titanium bar page, and the bar with zirconia on top under zirconia on a titanium bar. The version without a bar is the full-arch zirconia bridge.
Checklist before the bar goes on for teeth
- Abutments checked and torqued to the manufacturer’s value
- Bar stable with no screws, no rocking under alternating pressure
- One-screw test with no gap, from both ends
- No screw past your system’s resistance criterion
- Perpendicular radiograph with no gap at the subgingival interfaces
- Results by abutment and radiographs attached to the case
Related services
Open a portal accountFrequently asked questions
How do you do a framework try-in on a full-arch implant bridge?
Check the abutments, seat the bar without screws and press each side, run the one-screw test from both ends, tighten the screws one at a time while feeling for resistance, and radiograph the subgingival interfaces with the beam perpendicular. The bar only gets teeth if it passes every test.
What is the Sheffield test?
The Sheffield test is the one-screw test: with the bar seated, you tighten a single screw on a terminal abutment and look at the interface on the others. A gap at any of them means misfit. You repeat it from the other end, and a radiograph confirms what you can't see.
Is a framework try-in always necessary?
No consensus makes it mandatory, and the call is yours. The 2025 review by Pozzi and colleagues recommends a rigid prototype try-in until clinical trials settle how accurate full-arch scanning is. In a 2025 clinical study, 3 of 20 frameworks failed the one-screw test.
How do you check passive fit on a monolithic zirconia full arch with no bar?
With a verification jig before the final design, or with a rigid prototype milled or printed from the same design as the zirconia. The tests are the same as for a bar: alternating pressure, one screw from each end, screw resistance and a radiograph. Which try-in you use is agreed with the lab when the case is opened.
Sources
- Clinical methods for evaluating implant framework fit · The Journal of Prosthetic Dentistry (Kan et al., 1999)
- Passive fit in screw retained multi-unit implant prosthesis understanding and achieving: a review of the literature · The Journal of the Indian Prosthodontic Society (Buzayan and Yunus, 2014)
- Trueness and passivity of digital and conventional implant impressions in edentulous jaws: a prospective clinical study · Clinical Implant Dentistry and Related Research (Harfagar et al., 2025)
- Photogrammetry versus intraoral scanning in complete-arch digital implant impression: a systematic review and meta-analysis · Clinical Implant Dentistry and Related Research (Pozzi et al., 2025)
- Passive fit of milled and additively manufactured complete arch implant-supported titanium frameworks: a micro-CT analysis · BMC Oral Health (Eid et al., 2026)
- Misfit of implant prostheses and its impact on clinical outcomes. Definition, assessment and a systematic review of the literature · European Journal of Oral Implantology (Katsoulis et al., 2017)
- A radiographic analysis of implant component misfit · The International Journal of Oral & Maxillofacial Implants (Sharkey et al., 2011)
- Effect of splinted and nonsplinted impression techniques on the accuracy of fit of fixed implant prostheses in edentulous patients: a comparative study · The International Journal of Oral & Maxillofacial Implants (Papaspyridakos et al., 2011)
- Verification jig for implant-supported prostheses: a comparison of standard impressions with verification jigs made of different materials · The Journal of Prosthetic Dentistry (De La Cruz et al., 2002)
- Digitally designed and milled verification jigs generated from photogrammetry data acquisition: a clinical report · Journal of Prosthodontics (Sinada and Papaspyridakos, 2021)
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