Digital vs. Conventional Impressions in 2026: Accuracy, Fit and When Each Wins

The scanner is on the cart and the impression guns are still in the drawer. Most days the choice is easy. Then comes a bleeding distal margin, a six-implant arch or a flat lower ridge, and the question is real: which record gives the lab the truer picture?

The research now answers it case by case. Here is what it shows, and how to get an impression to the lab unchanged.

Quick Answer

Scan single crowns, inlays, onlays and short bridges whose margins you can see: in clinical meta-analyses, restorations from scans fit as well as or slightly better than those from conventional impressions, and patients prefer scanning. Take a PVS or polyether impression when you cannot expose and dry a subgingival margin, for complete-arch tooth-supported bridges and for complete dentures. For full-arch implant cases, scan or use photogrammetry, then verify the implant positions.

How Accurate Are Scans Compared With Impressions?

Trueness is how close a record is to the real geometry; precision is how closely repeated records agree. Lab studies measure both on models; clinical studies mostly compare methods or measure the final restoration.

Single units and short spans

A 2022 umbrella review of 11 systematic reviews found similar accuracy in laboratory data, and in clinical data for fixed prostheses of fewer than 4 units; it recommended the conventional approach for more extensive fixed or removable work. Clinical accuracy data are thin: a 2020 review found 6 clinical studies, whose authors agreed that high-precision impressions were more accurate in patients but disagreed on whether that causes misfit.

Full arches with teeth

In patients, a 2022 meta-analysis found full-arch scans and alginate impressions similarly true, 0.09 mm apart in 3D, with precision under 0.1 mm for both; it did not test PVS or polyether. For complete-arch tooth-supported bridges, a 2025 overview of 28 systematic reviews found conventional impressions more accurate.

Edentulous arches

The bench-to-mouth gap is widest here. A 2024 review of 16 in vitro and 9 in vivo studies reported scan trueness of 20 to 600 µm on models and 40 to 1,380 µm in patients, worst in mobile tissue: soft palate, vestibule and sublingual area. Implant scans have their own rules; see How to Scan Implants.

Do Crowns and Bridges Fit Better From a Scan?

What matters is the fit of the crown, and here clinical evidence leans slightly digital.

• Tooth-supported prostheses, 16 clinical studies: mean marginal fit 80.9 µm from scans and 92.1 µm from impressions, not a statistically significant difference (Bandiaky et al., 2022).
• Lithium disilicate single crowns: no significant difference (Tabesh et al., 2022).
• Zirconia bridges up to 4 units: better marginal and intaglio fit from scans, but 8 of the 9 studies were in vitro (Morsy et al., 2023).

A 2025 overview of 18 systematic reviews found none favoring conventional impressions for marginal adaptation, though most were of low or critically low quality. Do 10 to 20 µm matter clinically? A 2022 review found marginal fit under 120 µm, its acceptability threshold, with every material and impression technique. Whether the margin was captured matters more than how.

Where Do Conventional Impressions Still Win or Tie?

Deep subgingival margins and bleeding

A scanner records only what it can see. A 2025 review of 39 studies found that the more apical the finish line, the lower the scan accuracy, and that displacement cords dramatically improved it. In a 2026 randomized crossover trial in 15 patients, both methods reproduced shallow subgingival finish lines better with retraction; without it, the impression captured the finish line more clearly than the scan. On a typodont, saliva reduced scan trueness, most at subgingival margins.

Retraction matters either way: in the US National Dental Practice-Based Research Network, a dual-cord technique was associated with fewer repeat impressions for subgingival margins. Control bleeding first and rinse off hemostatic agents: 3M warns that their residues can inhibit polyether setting.

Complete-arch bridges and full-arch implant cases

For complete-arch tooth-supported bridges, the 2025 overview favored conventional impressions. For complete-arch implant prostheses, a 2026 meta-analysis of 37 studies (30 in vitro, 7 in vivo) found no overall difference; conventional impressions were slightly favored above 4 implants, and photogrammetry slightly beat conventional. Individual studies split 12 comparable, 11 for conventional, 13 for digital. Another 2026 meta-analysis found photogrammetry truer and more precise than scanners, yet a 2025 meta-analysis with the same finding still recommends a rigid prototype try-in. For materials, see Full-Arch Zirconia vs. PMMA vs. Hybrid.

Edentulous ridges and movable mucosa

Scanners record attached mucosa about as well as impressions, but a 2021 review found them unable to register mobile tissues accurately, and a 2023 review of 6 clinical studies placed the discrepancies mainly at the periphery. A 2026 scoping review found functional mobile tissue still hard to capture, especially in mandibular arches, and reliable evidence that scans can fully replace impressions for complete dentures lacking.

What About Time, Cost and Patient Preference?

Time and cost. In 16 clinical studies of tooth-supported prostheses, mean clinical time was 784 seconds for scanning and 1,125 for impressions, not a statistically significant difference. For implant restorations, a 12-study meta-analysis found scanning more time-efficient, and a 2025 meta-analysis found shorter laboratory times and lower direct laboratory costs with digital workflows in partial edentulism. Scanner costs are in Is an Intraoral Scanner Worth It?

Clinical acceptance. In the Network's study of 3,730 crowns, 99.5% of crowns from scans were clinically acceptable, against 97.0% from polyether and 95.5% from PVS impressions. More in Crown Remakes: What Really Causes Them.

Comfort. In the same 16 studies, mean visual analog comfort scores were 67.8 for scans and 39.6 for impressions. For implant prostheses, a 2025 meta-analysis of 18 studies favored scanning for nausea, bad taste, discomfort and overall satisfaction, with no difference in pain.

Scan or Impression? The Evidence by Situation

If You Take a Conventional Impression, How Should You Handle It?

Choose the material for the job

Use PVS or polyether for crowns, bridges and implants; the 2023 Aquasil Ultra+ instructions list it for all dental impression techniques. The 2025 Jeltrate alginate guide lists study, orthodontic and opposing models, partial denture frameworks without precision attachments, retainers, splints and provisionals, but not definitive crowns or bridges.

Pour on time

• PVS (Aquasil Ultra+): pour 30 minutes after disinfection or up to fourteen days later; wait 60 minutes for epoxy dies.
• Polyether (3M Impregum Super Quick): pour no earlier than 30 minutes and no later than 14 days after taking the impression; keep it dry.
• Alginate (Jeltrate): pour within one minute after disinfection, or wrap it in a wet towel in a sealed bag and pour within 24 hours.

Other brands differ; check yours.

Disinfect before it leaves the office

CDC's 2003 dental guidelines, which CDC says still serve as the standard of practice, call for impressions and bite registrations to be cleaned of blood and bioburden, disinfected with an EPA-registered hospital disinfectant with a tuberculocidal claim and rinsed, as soon as possible after removal. CDC also advises checking each material's stability with its manufacturer: the Jeltrate guide calls for cleaning within 5 minutes and an alginate-specific disinfectant, and 3M recommends glutaraldehyde for its Impregum Super Quick polyether. In a 2023 review, 10 minutes in 0.5 to 1% sodium hypochlorite or 2% glutaraldehyde inactivated oral bacteria, and disinfection within 30 minutes did not change alginate or polyether dimensions.

Ship it so it cannot distort

CDC asks for written information on the disinfectant and exposure time with each case, and notes that clinical materials not decontaminated fall under OSHA and Department of Transportation rules for shipping infectious materials. The Aquasil Ultra+ instructions call for packaging that prevents distortion and storage at ambient temperature, dry and away from direct sunlight.

When Should You Scan, Take an Impression, or Do Both?

Scan

• Single crowns, inlays, onlays and bridges up to 4 units with margins you can expose and dry.
• Patients with a strong gag reflex.

Take an impression

• A subgingival margin that will not stay retracted or dry.
• Complete-arch tooth-supported bridges.
• Complete dentures, where border molding records the functional sulcus.

Do both

• Full-arch implant cases: scan or photogrammetry for implant positions, then a verification jig or prototype try-in.
• Deep esthetic margins: a 2026 case report combined a silicone impression of the sulcus with intraoral scans and a scan of the provisional.

Digital and Conventional Cases at Elegant Dental Laboratory

• Scans: submit a digital case; digital scans are reviewed before production. Scanner setup is in How to Send a Scan to a Dental Lab.
• Impressions and models: send a case with our printable Rx forms and a UPS label from anywhere, or use our own drivers in the New York area (call to confirm availability).
• Every case is made in house at 2308 McDonald Ave, Brooklyn, by more than 35 technicians, with a 5 business day standard turnaround on most restorative cases, rush options and up to a 7-year warranty on final restorations.
• Considering a scanner? See Go Digital or call 877-335-5221.

Related Guides

• TRIOS vs. iTero in 2026: How the Two Leading Intraoral Scanners Compare
• Why Crowns Come Back High or With Open Contacts, and How to Prevent It
• Crown Prep Guide: Reduction, Margins and Taper for Zirconia, E.max and PFM

FAQ

Are digital impressions more accurate than conventional impressions?

For crowns and short bridges, restorations from scans fit as well or slightly better. For complete-arch bridges and edentulous arches, impressions remain more accurate or reliable.

Can I scan a subgingival margin?

Yes, if you can retract and dry it. If you cannot, take a PVS or polyether impression.

Can I mail an alginate impression to the lab?

Only if it will be poured in time: Jeltrate allows up to 24 hours, wrapped in a wet towel in a sealed bag.

Do I have to disinfect an impression before sending it?

Yes. CDC recommends cleaning, disinfecting with an EPA-registered tuberculocidal hospital disinfectant and rinsing, and noting the disinfectant and time on the case.

Is a scan accurate enough for a full-arch implant bridge?

Often, especially with 4 implants or fewer, but results vary. Plan a verification jig or prototype try-in, or consider photogrammetry.

Reviewed by Gary Fingerman, founder and CEO of Elegant Dental Laboratory, Brooklyn, New York (founded 2007). Last reviewed: September 28, 2026. Handling times are from current manufacturer instructions; follow those for the products you use.