Intraoral Scanners in Clinical Dentistry: A Comparative Review of Accuracy, Efficiency, and Patient Centred Outcomes

ABSTRACT

Intraoral scanners (IOS) have transformed many workflows in modern dentistry, particularly in prosthodontics, orthodontics, and implantology. This review critically examines the clinical performance of intraoral scanners in terms of accuracy (trueness, precision), efficiency (scan time, adjustment time), usability, and patient satisfaction. We survey recent in vitro and in vivo studies comparing IOS to conventional impressions, and compare different IOS brands/technologies. The evidence suggests that while many IOS now approach or exceed conventional impression techniques in certain contexts (single crowns, short-span prostheses), there remain limitations (e.g., long-span arches, soft tissue, mobile tissues, deep post spaces). Key factors influencing outcomes include scanner technology, scanning strategy, operator experience, and patient anatomy. Finally, we discuss current gaps and suggest future directions for research and clinical practice.

Keywords: intraoral scanner; digital impression; accuracy; patient satisfaction; prosthodontics; implant prosthesis

1. INTRODUCTION

Digital impressions acquired via intraoral scanners (IOS) have become increasingly integrated into clinical dentistry. The potential advantages include improved patient comfort, elimination of impression material distortions, streamlined lab workflow, and faster turnaround times. However, translation into consistent, high-quality outcomes depends heavily on scanner performance, clinical technique, and case selection.

This review aims to compare critically the performance of intraoral scanners in clinical settings—focusing on accuracy (both in vitro and in vivo), efficiency, the impact on patient-reported experiences, and limitations. We provide comparisons among different scanner technologies, examine influencing clinical factors, and highlight where the technology performs well and where it still lags conventional techniques.

2. PRINCIPLES OF INTRAORAL SCANNING

IOS capture three-dimensional surface data inside the patient’s mouth, typically using optical technologies such as confocal microscopy, structured light, triangulation, or parallel confocal optics. Key metrics of performance are:

• Trueness: how close the digital impression is to the actual geometry.
• Precision: how reproducible the impressions are under repeated scanning.
• Resolution and scanning speed, which influence both workflow and data handling.

In clinical settings, besides accuracy, aspects such as scanning strategy, presence of saliva/blood, tissue movement (mobile soft tissues), operator skill, scanner head size, and ambient conditions also influence outcomes.

3. TYPES OF INTRAORAL SCANNERS & TECHNOLOGIES

IOS differ in:

• Acquisition method (optical triangulation, confocal imaging, structured light, etc.).
• Form factor (size and weight of the scanner head, wired versus wireless, ease of access in the oral cavity).
• Software algorithms for stitching images, correction of distortions, noise filtering.
• Updates and compatibility (how manufacturer updates hardware/software, integration with CAD/CAM, export formats, libraries).

4. COMPARATIVE CLINICAL PERFORMANCE

Here we summarize comparative evidence on performance in real or clinically relevant settings.

4.1 Accuracy (Trueness & Precision) in Single Crowns / Short-Span Prostheses

• Clinical evaluations indicate that for single crowns or short-span bridges, many intraoral scanners (e.g. Trios, iTero) deliver accuracy comparable to conventional impressions. For example, a systematic review of implant prostheses showed that conventional and digital impressions had similar prosthetic outcomes, with digital impressions often being faster and preferred by patients. PubMed
• In the “CT vs IOS” or “IOS vs conventional” comparing post & core situations, one in vitro study found that for post space lengths up to 8 mm, accuracy remained clinically acceptable, though at 10 mm the apical third accuracy degraded significantly. Wiley Online Library

4.2 Full Arch, Edentulous, and Implant-Supported Prostheses

• Longer spans and multiple implants present greater challenges. In a study of intraoral scanners for full-arch digital implant impression, only some scanners (Omnicam, TRIOS devices, Apollo DI, Bluecam in one study) maintained deviations in a range (~30-45 µm) that might be acceptable for fixed prostheses. Others exceeded that threshold. MDPI
• For fully edentulous arches with multiple implants, in vitro experiments show generally lower precision across devices. Trios 3 mono and iTero Element showed relatively fair trueness but still with limitations. Wiley Online Library
• Another recent study comparing digital acquisition methods in complete-arch implant supported prostheses found that photogrammetry techniques (dedicated implant position capture systems) often outperform intraoral scanners in repeatability; increasing implant number tends to reduce repeatability in IOS devices. PubMed

4.3 Recording Soft Tissues, Denture Bearing Areas, and Mobile Tissues

• IOS perform well in capturing bony structures and mucosa that is attached or minimally mobile; they are less reliable in accurately recording mobile tissues (e.g. peripheral borders of denture bearing areas) and movable mucosa. A systematic review showed variation among devices, and that factors such as presence of artificial markers, size of scanner head, scanning strategy, and operator experience affect accuracy. PubMed
• For edentulous patients, a randomized/controlled comparative study showed that dentures made from digital impressions had better patient-rated fit and comfort than those from conventional impressions. Digital methods also reduced time to delivery. PubMed Central+1

4.4 Time / Workflow Efficiency and Operator Experience

• Systematic reviews/meta-analyses reveal that digital impressions (intraoral scanning) tend to reduce clinical (chairside) time, adjustment time, and overall treatment time in many contexts. In implant prosthesis-related cases, scanning times are significantly shorter, and patients prefer digital methods. PubMed
• Operator learning curves matter: one study comparing two scanners (iTero vs Trios) found that although baseline scan times for iTero were longer, the rate of improvement (experience) was greater. Trios had shorter scan times even early on, less influenced by experience. The JPD

4.5 Patient Comfort and Satisfaction

• Multiple studies show patients prefer digital scanning over conventional impressions. Factors include less gag reflex, less discomfort, cleaner process, faster experience. Meta-analyses show a statistically significant effect size favoring IOS in patient-reported outcomes. PubMed+1

Table: 1 Comparative overview of commonly used intraoral scanners (IOS) in clinical dentistry

5. FACTORS INFLUENCING CLINICAL PERFORMANCE

From the literature, key influencing variables include:

• Type of scanner technology, e.g. confocal vs triangulation vs structured light. Confocal scanners tend to have higher trueness/precision in many studies, especially for larger spans. PubMed+23Shape+2
• Scanner head size & ergonomics, which affect access, especially in posterior regions. Larger heads have difficulty in limited mouth opening or TMJ constraints. PubMed+1
• Scanning strategy/order (where you start, how you move, stitching patterns). Errors accumulate with longer spans or more complex paths. MDPI+1
• Operator experience: proficiency improves speed and sometimes accuracy. Novice users may have more scanning errors or require more time. The JPD+1
• Patient anatomy & intraoral conditions – degree of tooth irregularity, crowding, moisture (saliva/blood), soft tissue mobility, edentulism, etc. All of these can reduce scan accuracy. Synapse+2PubMed+2
• Software, updates, and post-processing – how well the scanner software handles stitching, filtering, alignment, margin detection. Updated software often improves performance.

6. LIMITATIONS AND CHALLENGES

Even with advances, there are clinical situations where IOS still underperform:

• Full-arch accuracy in edentulous arches or with many implants: deviations can cumulatively become clinically relevant. For e.g., for fixed prostheses over full-arch spans, small deviations can lead to misfit.
• Recording mobile soft tissues: border extensions in removable prosthodontics remain less predictable with IOS.
• Deep internal geometries: apical parts of post spaces or deep preparations can be difficult to capture accurately with optical scanners. Wiley Online Library
• Cost, learning curve, maintenance: high initial investment; operator training matters; scanner tip wear, calibration, and environmental factors (light, moisture) affect performance.
• Data handling and interoperability: file formats, lab compatibility, and consistency between different brands can pose practical challenges.

7. CLINICAL IMPLICATIONS & BEST PRACTICES

Based on existing evidence, some recommendations:

• Use IOS confidently for single crowns, short-span fixed partial dentures, implant prostheses with 1-2 implants in limited span, and as a replacement for conventional impressions in many routine cases.
• For full arch, multiple implants, or long-span fixed prostheses, select IOS with demonstrated high trueness/precision; consider adjuncts (photogrammetry, laboratory scanning) in critical parts.
• Follow manufacturer’s recommended scanning strategy, ensure proper soft tissue management, adequate dryness, controlled intraoral environment.
• Train clinicians thoroughly; allow time to build operator skill; monitor scan times and error rates.
• For removable prosthodontics, especially full dentures, use IOS with caution for capturing mobile tissues; possibly combine with conventional impression techniques when necessary.

8. FUTURE DIRECTIONS

Areas where further research and technological development seem promising:

• Improved technology for capturing soft, mobile, and dynamic tissues (e.g. mucosa, border extensions) with higher fidelity.
• Enhanced deep scanning capability for root canal spaces, post and core, and preparations with deep or narrow geometries.
• Augmented reality / AI–based image processing to improve stitching, error detection, margin detection, and real-time feedback to the operator.
• Standardization of methods for comparing scanner performance in vivo: uniform metrics (trueness, precision), standardized reference models, reporting guidelines.
• Cost-benefit studies over the long term: impact on lab corrections, remakes, patient outcomes, and practice economics.

9. CONCLUSION

Intraoral scanner technology has matured to a point where in many clinical applications it equals or surpasses conventional impression methods—especially for single units, short spans, and routine fixed prosthodontic or implant cases. Patient comfort and workflow efficiency are consistently improved. However, limitations remain in full-arch accuracy, capturing mobile soft tissue, deep geometries, and ensuring consistent performance across operators and conditions. With ongoing technological improvements and better clinical protocols, the use of IOS is likely to expand further toward challenging prosthodontic cases.