At-a-Glance: Why Moisture Matters

• Liquid on the tooth surface increases surface reflection and reduces scanner trueness and precision.
• Even small residual pools in fissures or sulci can distort margins and occlusal anatomy.
• Blow-drying with a three-way syringe significantly improves accuracy versus scanning wet surfaces.
• Dry scans consistently produce the lowest deviation values in controlled studies.

What the Research Shows About Liquid and IOS Accuracy

A key in-vitro study by Chen and co-authors examined how liquid attached to the tooth surface affects intraoral scanner accuracy (trueness and precision) and whether air-drying with a three-way syringe can mitigate those effects.

The researchers evaluated two common scanners under three surface conditions:

• Dry
• Wet (ultrapure water or artificial saliva)
• Blow-dry (air syringe after liquid contact)

Key Findings (Simplified)

• Scans made on wet surfaces showed significantly higher RMS deviation than dry or blow-dry conditions (p < 0.001).
• Dry and blow-dry scans both improved accuracy, with dry surfaces performing best overall.
• The composition of the liquid (water vs artificial saliva) had little effect; the presence of liquid itself was the problem.
• Deviations were most prominent in fissures, pits, and the interproximal area of teeth, and at the margins of abutments.

In short: moisture on the tooth surface is a predictable source of error for all intraoral scanners. Drying with a three-way syringe materially improves the data your scanner captures, but full drying is still the gold standard.

Practical Fluid Control Protocol for Daily Scanning

The following steps are not tied to a specific scanner brand. They’re designed to give your team a repeatable, low-friction protocol that lines up with the evidence and what we see in day-to-day lab work.

1. Prioritize a Truly Dry Tooth Surface

• Use high-volume evacuation with targeted placement near the area being prepared.
• Combine cotton rolls, dry angles, and parotid shields for maxillary posterior teeth.
• When margins are subgingival, use an absorbent retraction cord to wick crevicular fluid before scanning.

2. Control Saliva Rebound During Longer Scans

Salivary flow doesn’t pause just because the scanner is in the mouth. For multi-unit or quadrant scans:

• Segment the scan and re-dry every 20–30 seconds rather than trying to “push through” continuous scanning.
• Reposition HVE and consider a second suction tip when needed for posterior mandibular cases.

3. Manage Blood and Hemostatic Agents Before Scanning

• Fully rinse hemostatic gels or solutions; residual material can mimic enamel reflectivity and confuse the scanner.
• If bleeding persists, consider delaying scanning until soft-tissue management is stable—just as you would for a PVS impression.

4. Use a Consistent “Sweep-Dry, Then Scan” Technique

The Chen study confirmed that blow-drying improves scan accuracy when liquid has contacted the surface. For best results:

• Use a continuous sweeping motion with the air syringe from occlusal toward the gingiva, not a static blast.
• Visually confirm that fissures and marginal areas are free of fluid before you begin scanning each pass.

5. Expose Subgingival Margins Whenever Possible

• Double-cord technique with removal of the top cord immediately prior to scanning.
• Retraction paste or Expasyl for cases with delicate tissue.
• Laser troughing when clinically appropriate and within your comfort zone.

In digital dentistry, the scanner cannot “guess” what is under tissue or pooled fluid. Clear exposure of the margin is essential for accurate design and predictable seating.

Common Scan Errors We See When Moisture Isn’t Controlled

Looking across digital cases from multiple practices, we see recurring patterns when moisture control is inconsistent:

• Rounded or indistinct margins where fluid obscures the finish line.
• Localized “puffy” or flattened areas in the 3D model where liquid pooled in fissures or around line angles.
• Interproximal distortion that leads to heavy contacts or open contacts at seating.
• Posterior occlusal discrepancies, especially on the functional cusp slopes in blow-dry cases where some liquid remained.

These issues are often preventable with a few extra seconds of drying and verification before capturing the final scan.

How Rohling Dental Laboratory Supports Your Digital Workflow

We are not a mass-production operation. Our technicians routinely review IOS cases for:

• Margin clarity and continuity
• Proximal anatomy and contact relationships
• Occlusal morphology and opposing arch data
• Stitch lines or areas of suspected scanner distortion

If we see a moisture-related concern that could impact your outcome, we will let you know. We want to be an extension of your practice. We care about how our work impacts not only you and your staff, but most importantly, the patient. The goal is fewer surprises at the seat appointment and less time spent adjusting restorations.

Clinical Takeaways

• Liquid on the tooth surface is a predictable source of scanning error, regardless of scanner brand.
• Dry and blow-dry conditions significantly improve trueness and precision compared with wet scanning.
• Simple protocols—HVE, retraction, sweep-drying, and re-drying during long scans—have an outsized impact on results.
• Partnering with a lab that reviews digital data critically can help identify and correct small issues before they become remakes.