What is the most effective scanner for achieving margin clarity in dentistry?

Margin Clarity in Dental Scanning: Comparison of Different Scanners

For achieving optimal margin clarity in dentistry, CBCT (Cone Beam Computed Tomography) is the most effective scanner when 2D imaging is insufficient to clarify anatomical relationships, though intraoral periapical radiography with dedicated film holders and beam aiming devices should be the first-line approach for most cases. 1

First-Line Imaging Approach

Intraoral Periapical Radiography

• Recommended as the primary imaging technique for margin clarity assessment 1
• Should be performed using dedicated film holders and beam aiming devices to ensure proper alignment and reduce distortion 1
• Provides adequate visualization for most clinical scenarios with significantly lower radiation exposure than 3D imaging
• Particularly effective when assessing:
  • Crown margins
  • Root canal treatment margins
  • Periapical tissues
  • Restorative margins

Bitewing Radiography

• Technique of choice when assessing carious lesions of permanent teeth 1
• Provides excellent visualization of interproximal margins
• Image size is large enough to evaluate the whole crown of a permanent tooth
• Should be supplemented with periapical radiography when pulpal or apical involvement is suspected 2

Advanced Imaging Options

CBCT (Cone Beam Computed Tomography)

• Indicated when 2D imaging is insufficient to clarify anatomical relationships 1
• Provides superior margin clarity for complex cases but with higher radiation exposure
• Should not be considered as a first-choice examination 1
• Must follow the ALARA principle (As Low As Reasonably Achievable) by using targeted FOV (Field of View) 1
• Particularly valuable for:
  • Dysmorphic dental roots
  • Complex anatomical relationships
  • Suspected root fractures
  • Dental trauma cases where 2D imaging is inconclusive 1

Intraoral Scanners

• Digital impressions from intraoral scanners show varying levels of accuracy for margin clarity
• Short-span scans (23-43 μm precision) provide better accuracy than complete-arch scans (80-198 μm precision) 3
• Clinical factors significantly affecting margin clarity with intraoral scanners include:
  • Proximity to gingivae (equigingival margins are more difficult to capture accurately)
  • Presence of adjacent teeth (especially affecting mesial margins)
  • Accessibility for scanner wand positioning 4

Comparative Performance of Scanning Technologies

Intraoral Scanner Precision

• Median precision for short-span scans: 23-43 μm (intraoral) vs. 22-29 μm (extraoral) 3
• Median precision for complete-arch scans: 80-198 μm (intraoral) vs. 81-165 μm (extraoral) 3
• Trueness of short-span scans: 38-47 μm (intraoral) vs. 28-40 μm (extraoral) 3
• Trueness of complete-arch scans: 147-433 μm (intraoral) vs. 118-581 μm (extraoral) 3

Scanner Resolution Impact

• Higher resolution settings do not necessarily improve margin clarity
• Standard resolution scans can be as accurate as high-resolution scans while requiring less time (34.2-46.5 seconds less) 5
• Tooth surface characteristics affect accuracy more significantly than scanner resolution settings 5

Clinical Applications and Limitations

Optimal Applications for Different Scanners

• Intraoral periapical radiography: First-line for most dental margin assessments 1
• CBCT: Complex cases requiring 3D visualization of anatomical relationships 1
• Intraoral scanners: Suitable for digital impressions for fabricating prosthetic restorations but with limitations for margin clarity in certain clinical situations 6

Key Limitations to Consider

• Intraoral scanners struggle with deep margin lines in prepared teeth 6
• Bleeding can significantly compromise margin clarity with optical scanning 6
• Distal surfaces show the highest discrepancies in digital scans 5
• Equigingival margins on buccal surfaces are particularly challenging to capture accurately 4

Best Practices for Optimal Margin Clarity

1. Begin with intraoral periapical radiography using dedicated film holders and beam aiming devices 1
2. Use bitewing radiography for interproximal margin assessment 1, 2
3. Progress to CBCT only when 2D imaging is insufficient, using targeted FOV 1
4. When using intraoral scanners:
   • Focus on short-span rather than complete-arch scans when possible 3
   • Pay particular attention to distal and equigingival margins 5, 4
   • Control bleeding and moisture for improved margin clarity 6
   • Consider standard resolution settings for efficiency without sacrificing accuracy 5

By following this evidence-based approach to scanner selection and utilization, clinicians can achieve optimal margin clarity while minimizing radiation exposure and maximizing diagnostic accuracy.