CAD/CAM Technology in Restorative Dentistry and Endodontics

Introduction

Components of a CAD/CAM System

1. Data acquisition unit (scanner/digitizer) - captures the 3D surface geometry of the prepared tooth either directly (intraoral scanner - optical/laser scanning of the mouth) or indirectly (scanning of a stone cast or impression).
2. Designing unit (software) - the acquired data is displayed as a virtual model on screen; the operator (or automated software) designs the restoration - contours, occlusal anatomy, margins, connectors, and material thickness - using CAD software.
3. Manufacturing unit - converts the digital design into a physical restoration by:
   • Subtractive manufacturing - milling/grinding a block of ceramic, composite, or metal using diamond burs under water/air coolant.
   • Additive manufacturing - 3D printing (stereolithography, digital light processing, fused deposition modelling) used for models, surgical guides, temporary crowns, and increasingly definitive restorations.

Classification of CAD/CAM Systems

Applications in Restorative Dentistry

• Inlays, onlays, and veneers - milled from monolithic ceramic blocks (lithium disilicate, leucite-reinforced glass ceramic) with excellent marginal fit and aesthetics in a single visit.
• Full crowns and fixed partial dentures (bridges) - both anterior and posterior, in ceramic, zirconia, or hybrid ceramic materials.
• Implant-supported restorations - custom abutments and implant crowns/bridges with precise fit to the implant platform.
• Removable prosthodontics - CAD/CAM-milled or printed denture bases and try-in dentures, improving fit and reducing chair-time.
• Diagnostic wax-ups and smile design - virtual mock-ups for aesthetic planning before definitive treatment.
• Materials used: feldspathic and leucite-reinforced ceramics, lithium disilicate glass-ceramic, zirconia (monolithic and layered), hybrid ceramics/resin-ceramic composites, and PMMA for provisional restorations.

Chairside CAD/CAM workflow: (A) digital crown design on 3D scan data, (B) milling of a lithium disilicate ceramic block.

Applications in Endodontics

1. 3D-printed endodontic access guides - Cone-beam CT (CBCT) data is fused with an intraoral/model scan; software plans the ideal access cavity and canal trajectory, and a physical guide (with a metal sleeve to direct the bur) is 3D-printed. This is invaluable in:
   • Locating calcified/obliterated canals
   • Conservative access cavity preparation in teeth with extensive restorations
   • Avoiding perforation in cases with altered canal anatomy (e.g., dens invaginatus, dilacerated roots)
2. Guided apical surgery - CAD/CAM-fabricated surgical guides help precisely locate the osteotomy site and control the angle/depth of resection during apicoectomy, minimizing damage to adjacent anatomical structures (inferior alveolar nerve, sinus floor).
3. Custom endodontic post and core fabrication - CAD/CAM milling of fiber-reinforced or zirconia posts and cores that are custom-fitted to the canal anatomy, improving retention and reducing risk of root fracture compared to prefabricated posts.
4. CAD/CAM in regenerative and restorative interface - fabrication of customized intracanal medicament carriers, custom post-endodontic restorations (endocrowns) that are milled directly onto the pulp chamber/root canal orifice geometry from a single ceramic block, ideal for badly broken-down endodontically treated posterior teeth as they eliminate the need for a separate post-core and crown.
5. 3D-printed models for treatment planning and simulation - printed replicas of complex root canal systems used for case planning, patient education, and endodontic training.
6. Digital workflow integration - CBCT + intraoral scan superimposition (double-scan technique) allows a single digital dataset to plan both the endodontic access/surgery and the final restoration, streamlining interdisciplinary treatment.

Advantages of CAD/CAM Technology

• Eliminates conventional impressions, improving patient comfort and reducing distortion errors
• High precision and reproducibility of fit (marginal and internal adaptation)
• Reduced chair-time; many restorations completed in a single visit
• Reduced laboratory dependency and turnaround time
• Consistent, homogeneous, defect-free industrially processed blocks (fewer porosities than cast/hand-layered restorations)
• Enhanced conservation of tooth structure in guided endodontic access
• Improved case documentation, communication, and archiving of digital records
• Greater accuracy in complex or high-risk cases (calcified canals, surgical guidance)

Disadvantages / Limitations

• High initial cost of equipment (scanners, milling units, software) and per-unit block/material cost
• Steep learning curve for clinicians and technicians
• Limited to certain restoration types/materials (some CAD/CAM ceramics still show lower flexural strength than metal-ceramic in high-stress areas)
• Difficulty capturing subgingival margins or in cases with limited access/moisture control (bleeding, saliva) during intraoral scanning
• Guided endodontic access requires an additional CBCT scan (radiation exposure) and lab/printing time before treatment
• Milling burs wear over time, potentially affecting long-term precision
• Not all clinical situations (e.g., very deep subgingival margins, extensive edentulous ridges) are fully suited to digital scanning

Recent Advances

• Integration of artificial intelligence for automated margin detection and restoration design suggestions
• Hybrid manufacturing combining milling and 3D printing (dual workflows) for both provisional and definitive prostheses
• Intraoral scanners with AI-assisted CBCT fusion enabling one-visit guided endodontic treatment planning
• Development of stronger 3D-printable ceramic-filled resins for permanent restorations, narrowing the gap with milled ceramics

Conclusion