Digital Dentistry: CAD/CAM and Intraoral Scanning Workflows

Digital dentistry has transitioned from an academic curiosity to a clinical necessity over the past two decades. The convergence of intraoral scanning, computer-aided design (CAD), computer-aided manufacturing (CAM), cone-beam computed tomography (CBCT), and 3D printing has fundamentally re-engineered the workflows of restorative dentistry, prosthodontics, implantology, orthodontics, and oral surgery. The dental practice that integrates digital technology gains improvements in diagnostic accuracy, treatment predictability, laboratory communication efficiency, and patient experience—the last being perhaps the most transformative, as patients who have experienced both conventional impression-taking with viscous impression materials and a 10-second intraoral scan rarely choose to return to the analog method. This article examines the core technologies of contemporary digital dentistry and their clinical integration.

Intraoral Scanning Technology

The intraoral scanner (IOS) is the digital gateway through which the physical oral environment enters the virtual design space. Modern scanners use one of three optical technologies to capture the three-dimensional topography of the dentition and soft tissues:

Scanning Protocol and Accuracy

Scan accuracy has two components: trueness (how closely the scan matches the actual geometry) and precision (how consistently repeated scans of the same object match each other). The clinical threshold for acceptable marginal fit of a fixed restoration is generally considered to be less than 120 microns of marginal discrepancy. Current-generation intraoral scanners demonstrate trueness in the range of 15-50 microns for single-unit scans and 30-80 microns for full-arch scans—within the clinically acceptable range for single crowns, inlays, onlays, and short-span fixed dental prostheses (FDPs). For full-arch implant-supported prostheses, where passive fit across multiple implants is critical to prevent biological and mechanical complications, the accuracy threshold is more demanding (less than 50 microns of 3D deviation across the arch), and many scanners remain at or near the limit of this threshold.

Recommended scanning protocol for optimal accuracy:

1. Preparation: Place a single retraction cord (#00 or #000) if the preparation margin is subgingival. Ensure the preparation, adjacent teeth, and opposing arch are clean and dry. Powder is not required for current-generation scanners but may be applied selectively on highly reflective metal surfaces (amalgam restorations, metal implant scanbodies).
2. Starting quadrant: Begin scanning on the occlusal surface of the most distal tooth in the arch. This provides an initial reference plane with distinct occlusal anatomy that the software uses to anchor subsequent frames.
3. Scan path: Proceed mesially along the occlusal surfaces, then rotate to the buccal surfaces from distal to mesial, then the lingual/palatal surfaces from mesial back to distal. This captures all surfaces with overlapping coverage. For full-arch scans, continue this pattern through the contralateral quadrant without interruption; do not lift the scanner and restart, as this introduces stitching errors.
4. Preparation scanning: Dedicate additional attention to the preparation: scan the margin from multiple angles (buccal, lingual/palatal, mesial, distal), ensuring the margin is clearly delineated with at least 2 mm of sound tooth structure apical to the margin captured in the scan. For subgingival margins where a cord is placed, scan immediately upon cord removal, before the gingival tissue rebounds.
5. Occlusal registration: Capture the buccal bite registration in maximum intercuspation. For full-arch cases, bilateral buccal registrations (right and left) improve the accuracy of the virtual articulation.

CAD/CAM Systems: Chairside and Laboratory Workflows

Chairside CAD/CAM

Chairside CAD/CAM—epitomized by the CEREC system (Dentsply Sirona), though now joined by Planmeca FIT and other systems—enables same-day restoration design, milling, and delivery within a single appointment. The workflow eliminates the provisional restoration entirely, reduces the number of appointments from two to one, and eliminates the laboratory turnaround time, which is particularly advantageous for patients with geographic or scheduling constraints.

Chairside workflow:

1. Scan: Intraoral scan of preparation, adjacent teeth, opposing arch, and bite.
2. Design (CAD): The software automatically proposes a restoration design based on the tooth's position, adjacent and opposing tooth anatomy, and the virtual die. The clinician refines the design: margin line verification, proximal contact intensity, occlusal contact distribution (the virtual articulator simulates excursive movements using the digital facebow and patient-specific condylar settings if recorded), axial contours, and emergence profile. The design process for a single-unit restoration typically takes 5-10 minutes.
3. Mill (CAM): The designed restoration file is sent to the in-office milling unit. A block of the selected material—lithium disilicate (IPS e.max CAD), leucite-reinforced glass-ceramic (IPS Empress CAD), zirconia-reinforced lithium silicate (Celtra Duo, Vita Suprinity), hybrid ceramic (Vita Enamic, Lava Ultimate), or feldspathic ceramic (Vita Mark II)—is positioned in the mill. Milling time: 8-15 minutes for a single-unit monolithic restoration, depending on material and complexity.
4. Post-milling processing: For lithium disilicate, the milled restoration is in a partially crystallized ("blue") state with lower strength and easier millability. It must be crystallized in a porcelain furnace (approximately 20 minutes at 840-850 degrees Celsius) to achieve its final translucency and flexural strength (360-400 MPa). Staining and glazing follow crystallization.
5. Try-in and cementation: The restoration is tried in, proximal contacts and occlusion are adjusted with fine diamond burs, and the restoration is polished or glazed. Adhesive cementation (resin cement with total-etch or self-etch technique) under rubber dam isolation completes the workflow.

Laboratory CAD/CAM

Laboratory CAD/CAM extends the digital workflow to more complex restorations—multi-unit FDPs, full-arch prostheses, implant-supported restorations, and removable prostheses—that exceed the material and geometric capabilities of chairside milling. The laboratory CAD software (exocad, 3Shape Dental System) provides advanced design tools: virtual articulator with full condylar guidance settings, smile design modules for esthetic zone cases, implant library integration for custom abutment and screw-retained crown design, and framework design for metal copings, partial denture frameworks, and implant bars.

The laboratory CAM options are more diverse than chairside milling, ranging from subtractive manufacturing (5-axis milling of zirconia, lithium disilicate, PMMA, wax, and metal) to additive manufacturing (3D printing).

3D Printing in Dentistry

Additive manufacturing—popularly termed 3D printing—has rapidly expanded its role in dentistry, driven by the development of biocompatible resins, improved resolution (down to 25-50 microns in current-generation dental printers), and the expiration of key patents that has increased competition and lowered hardware costs. Technologies used in dentistry include:

Surgical guide workflow: The integration of CBCT DICOM data with intraoral scan STL data in implant planning software (coDiagnostiX, SimPlant, Blue Sky Bio) allows virtual implant placement with prosthetically driven positioning. The surgical guide is designed in the software, exported as an STL file, and 3D printed in a biocompatible, autoclave-sterilizable surgical guide resin. The guide transfers the virtual implant position to the surgical site with sleeve-guided drilling, controlling osteotomy depth, angulation, and mesiodistal/buccolingual position with accuracy within approximately 1 mm at the implant apex and 1 degree of angular deviation relative to the virtual plan—a clinically significant improvement over freehand placement for cases requiring precise prosthetic alignment (immediate loading, full-arch rehabilitation, esthetic zone single implants).

Digital Implant Planning and Guided Surgery

The fully digital implant workflow begins with data acquisition: a CBCT scan (DICOM format) and an intraoral scan (STL format) or a scan of a stone model. The two datasets are superimposed (registered) using common anatomical landmarks—typically the remaining dentition—or a radiographic scanning template with radiopaque markers. In the implant planning software, the clinician performs the virtual implant placement, taking into account the prosthetic plan (crown position, emergence profile), the bone volume and quality, the proximity to vital structures (inferior alveolar nerve, mental foramen, maxillary sinus, nasal floor), and the inter-implant and implant-tooth distance requirements (minimum 1.5 mm from adjacent implant and 1.5 mm from adjacent tooth root).

The surgical guide is then designed to fit precisely over the dentition or edentulous ridge, with metal sleeves at the planned implant positions. The guide is fabricated by 3D printing or milling. During surgery, the guide is seated and checked for stability; drill sleeves of progressively increasing diameter are placed in the guide's metal sleeves to control the osteotomy sequence; the implant is placed through the guide (fully guided) or the guide controls only the initial pilot drill and the remainder of the osteotomy and implant placement are performed freehand (partially guided). The accuracy of fully guided implant placement, as measured by superimposition of the planned and actual implant positions on a postoperative CBCT, is superior to partially guided and freehand placement.

Clinical Evidence and Limitations

The clinical evidence base for digital dentistry has matured substantially. Systematic reviews and meta-analyses support the following conclusions:

• Single-unit restorations: Intraoral scanning and CAD/CAM restoration (chairside or laboratory) produce marginal fit, proximal contacts, and occlusal contacts that are clinically equivalent to conventional impressions and laboratory-fabricated restorations. Patient preference strongly favors intraoral scanning over conventional impressions (less discomfort, no gagging, shorter procedure time).
• Short-span FDPs (3-4 units): Digital workflows produce clinically acceptable marginal fit. The accuracy of full-arch intraoral scans for long-span or full-arch restorations, however, remains a limitation—conventional impressions with polyvinyl siloxane or polyether remain the gold standard for full-arch accuracy in many practices.
• Implant restorations: For single-implant crowns, the digital workflow (scanbody-based intraoral scan, CAD/CAM custom abutment and crown) demonstrates equivalent or superior accuracy compared to the conventional open-tray pickup impression technique. For multi-implant cases, the accuracy of the digital scan is inversely proportional to the inter-implant distance; the conventional splinted open-tray pickup impression remains more accurate for full-arch implant cases.
• 3D-printed surgical guides: Meta-analyses report mean deviations of 1.0-1.5 mm at the implant apex and 3-5 degrees of angular deviation compared to the virtual plan, with fully guided surgery demonstrating approximately half the deviation of partially guided surgery. The clinical significance of this deviation depends on the case complexity: in the posterior mandible with abundant bone, a 1.5 mm deviation may be inconsequential; in the anterior maxilla with thin buccal bone, the same deviation risks perforation and esthetic compromise.

Conclusion

Digital dentistry is not merely an analog-to-digital translation of existing workflows but a transformation that enables new clinical possibilities—same-day restorations, prosthetically driven implant planning, multi-material additive manufacturing—that were technically impossible or economically prohibitive in the analog era. The decision to adopt digital technology should be evidence-driven and incremental: a practice can begin with an intraoral scanner for single-unit restorations, gain proficiency over months, and progressively integrate CAD/CAM milling, CBCT-guided implant surgery, and 3D printing as the clinical demand and return on investment justify each step. The digital dental practice of the future is already taking shape in the present; the question for the clinician is not whether to adopt digital dentistry, but when and how to integrate it into a practice philosophy that prioritizes precision, efficiency, and patient-centered care.