Impression Armamentarium in Dentistry From Conventional Materials to Intraoral Scanners

Why We Need Impressions

Every indirect dental restoration — whether a crown, bridge, inlay, onlay, denture, orthodontic appliance, or implant prosthesis — is fabricated outside the mouth on a replica model. The impression is the critical link between the patient’s oral anatomy and the laboratory. Its accuracy directly determines the marginal fit, occlusal harmony, and long-term success of the final prosthesis.

Specific reasons impressions are indispensable include: recording the prepared tooth geometry and finish-line for fixed restorations; capturing the edentulous ridge form, palatal contours, and functional borders for removable dentures; documenting the three-dimensional position of implant fixtures through scan bodies or impression copings; obtaining baseline study models for orthodontic diagnosis and treatment planning; fabricating surgical guides, stents, bleaching trays, mouthguards, and night guards; and monitoring changes in tooth position, wear, or soft-tissue dimensions over time through serial models.

Even with the rapid adoption of intraoral scanning, the objective remains the same — an accurate three-dimensional record of the clinical situation. The method of capture (material-based versus optical) is evolving, but the fundamental requirement for precision and completeness has not changed.

Different Armamentarium for Impressions

The impression armamentarium can be divided into seven functional categories: trays, impression materials, mixing and dispensing devices, adhesives and spacers, tissue management instruments, disinfection supplies, and digital scanning equipment. Each category plays a defined role in ensuring the impression procedure yields clinically acceptable results. The table below provides a comprehensive inventory.

Tray selection is the first decision.

• Stock trays (metal or plastic, perforated or rim-lock) are used for preliminary impressions,

• Custom trays fabricated on primary casts are essential for final impressions in complete denture and precision fixed prosthodontics.

• Triple trays capture the preparation, opposing arch, and bite registration simultaneously and are popular for single-unit restorations.

Material handling equipment has advanced significantly.

• Automixing cartridge systems for PVS and polyether have largely replaced hand mixing, providing consistent base-to-catalyst ratios, reduced void incorporation, and extended working time.

• For alginate, mechanical vacuum mixers are available in high-volume clinics, though manual bowl-and-spatula mixing remains standard in most practices.

We need adhesives and spacers to make impressions accurate and stable:

• Tray adhesive (material-specific):Bonds the impression material to the tray to prevent pull-away, bubbles, and distortion on removal. Use the adhesive made for the same material (e.g., alginate, PVS, polyether) and let it dry before loading.

• Baseplate wax spacer:Creates uniform material thickness and space for wash/detail, improving accuracy and reducing internal stress/pressure spots. Commonly adapted as an even layer, stopping short of borders as needed.

• Tray adhesive solvent:Removes old adhesive from trays (and helps clean before reapplication) so new adhesive bonds reliably. Use with ventilation and follow the product instructions; clean and dry the tray afterward.

Tissue management deserves emphasis. Retracting the gingiva to expose subgingival margins is essential for an accurate impression of the finish line.

• Retraction cords impregnated with hemostatic agents (aluminium chloride, ferric sulfate) remain the most common method.

• Retraction pastes (e.g., Expasyl, Traxodent) offer a cordless alternative that is less technique-sensitive.

• Electrosurgery and laser-assisted retraction are used in select cases.

Dental impression disinfection is important because impressions can carry saliva, blood, and germs from the patient to your team and the dental lab. Disinfecting them helps prevent cross-contamination and protects patients, staff, and lab technicians.

• Rinse immediatelyunder cool water to remove saliva/blood/debris.

• Disinfectusing anapprovedproduct that’scompatible with the impression material(spray or immersion) andtime the full contact time.

• Rinse again, shake off excess water (don’t over-dry), andpackage in a clean bag/container.

• Label for the lab:“Disinfected,” product used, time completed, and initials.

Intraoral Scanners: Types and Specifications

Intraoral scanners (IOS) represent the digital evolution of impression making. These handheld devices project a light source (laser or structured light) onto oral tissues, capture the reflected pattern using imaging sensors, and reconstruct a three-dimensional surface model through proprietary software algorithms. The output is a digital file (typically STL, PLY, or DCM format) that can be transmitted electronically to the laboratory or used directly for chairside CAD/CAM milling.

Modern scanners operate on one of several optical principles: confocal microscopy (CEREC Omnicam), active wavefront sampling, triangulation (Planmeca Emerald), parallel confocal imaging (iTero), ultrafast optical sectioning (3Shape TRIOS), or video-based 3D-in-motion capture (Medit). Each approach has implications for scan speed, depth of field, accuracy, and sensitivity to ambient light or moisture. Regardless of the underlying technology, current-generation IOS devices consistently achieve clinically acceptable accuracy for most indications, with deviations typically within 50 µm for full-arch scans and below 20 µm for single-unit preparations.

Comparative Specifications of Leading Intraoral Scanners

Scanner-Specific Notes

CEREC Primescan 2 (Dentsply Sirona)

The Primescan 2, launched in late 2024, is the world’s first cloud-native intraoral scanner. It scans directly through a web browser via the DS Core platform, eliminating the need for a dedicated acquisition centre. Its Smart Pixel Sensor technology processes over 1.5 million 3D data points per second with a dynamic depth of up to 20 mm. The scanner supports wireless operation, integrates seamlessly with CEREC for chairside milling, and exports open STL files for third-party CAD/CAM workflows. The redesigned tip improves posterior access, though the unit is heavier than most competitors.

3Shape TRIOS 6

Unveiled at IDS 2025, the TRIOS 6 features AI-driven ScanAssist guidance, captures over 4,000 images per second, and includes a hygienic closed autoclavable tip with sapphire glass. It outputs open-format files (STL, PLY, DCM) and integrates orthodontic simulation, shade matching, and patient communication tools within the 3Shape ecosystem.

Medit i900

Medit’s flagship scanner offers 70 fps capture, AI-powered soft-tissue removal, and a compact design with one of the largest fields of view in its class. Its open-architecture software (Medit Link) integrates with virtually all major CAD/CAM platforms, positioning it as a premium yet cost-competitive option.

iTero Lumina (Align Technology)

The iTero Lumina features a three-times-larger field of view, multi-angle simultaneous capture, and near-infrared imaging (NIRI) for interproximal caries detection. Full-arch impressions complete in under 60 seconds. It integrates natively with Invisalign workflows, making it particularly valuable for orthodontic practices, and offers time-lapse comparison for tracking tooth movement.

Shining 3D Aoralscan Elite

The Aoralscan Elite introduced intraoral photogrammetry (IPG) — coded scan bodies that establish geometric reference points during implant scanning, significantly improving full-arch implant accuracy. It features real-time colour scanning, a 16 × 12 mm field of view, and open-format export. It was the Institute of Digital Dentistry’s Scanner of the Year for 2024.

Advances in Technology for Impression Making

The evolution from hand-mixed plaster impressions to cloud-native optical scanning represents one of the most significant technological transitions in clinical dentistry. Several key advances deserve attention.

Digital Workflow Integration

Intraoral scanners now function as the entry point to a fully digital chain: scan → CAD design → CAM fabrication (milling or 3D printing). This eliminates the cascade of material-related errors inherent in conventional workflows — dimensional change during polymerisation, distortion during tray removal, expansion during die stone pouring, and further distortion during investment and casting. The result is a streamlined process with fewer variables, faster turnaround, and more predictable prosthetic outcomes.

AI and Machine Learning

Current-generation scanners incorporate artificial intelligence for automatic soft-tissue removal (eliminating tongue, cheek, and instrument artefacts from scans), automatic margin detection on prepared teeth, scan quality assessment in real-time, and predictive preparation design suggestions. The 3Shape TRIOS platform, for instance, uses AI-driven ScanAssist to guide operators through the scanning path, reducing learning curves for new users and improving consistency across operators.

Cloud-Based Collaboration

The Primescan 2’s cloud-native architecture processes and stores scans in real time, accessible from any device with a web browser. This eliminates local hardware dependency and enables instant case sharing with laboratories worldwide. Other manufacturers are following suit through Medit Link, 3Shape Communicate, and iTero’s MyiTero portal.

Conclusion

The impression armamentarium in dentistry has expanded from a handful of rigid materials and metal trays to a sophisticated ecosystem encompassing precision elastomers, tissue management systems, automixing devices, and cloud-connected intraoral scanners. Understanding the full scope of available instruments and materials — and the clinical rationale for selecting each — is fundamental to producing accurate impressions and, ultimately, well-fitting prostheses.

Intraoral scanners such as the CEREC Primescan 2, 3Shape TRIOS 6, Medit i900, iTero Lumina, and Aoralscan Elite now deliver accuracy that matches or exceeds conventional elastomers for most clinical indications. For the practising clinician, mastery of both conventional and digital impression techniques is essential. Conventional materials remain indispensable for complex implant cases, resource-limited settings, and specific clinical scenarios. Simultaneously, intraoral scanning technology is no longer aspirational but increasingly a baseline expectation. The future lies in the intelligent integration of material science and digital technology, guided by sound clinical principles.

Choose the workflow according to the clinical information required

No impression method is universally superior. Selection depends on margin location, moisture control, span, implants, soft-tissue displacement, patient tolerance, laboratory compatibility and operator experience. Digital scanning avoids material distortion but introduces scanning strategy, software, calibration and data-transfer variables.

Continue with impression material selection, putty impression technique and conventional implant impressions.

Frequently asked questions

Are intraoral scanners always more accurate?

No. Accuracy is task-, span-, system- and technique-dependent.

Why is tray adhesive important?

It helps retain impression material to the tray and reduce separation-related distortion when correctly matched and dried.

Must impressions be disinfected?

Conventional impressions require material-compatible infection-control processing before laboratory transfer.