CHAPTER 12: DIGITAL DENTISTRY

What does CAD/CAM stand for in dentistry?

A: Computer-Assisted Design / Computer-Assisted Machining.

Q: What is the main application of CAD/CAM technology in restorative dentistry?

A: Fabrication and delivery of permanent restorations for teeth and implants.

Q: How long has dental CAD/CAM been incorporated into patient care?

A: For the past 30 years.

Q: What advantage does CAD/CAM provide for ceramic restorations?

A: Enables delivery of esthetic ceramic restorations in a single dental appointment.

Q: What are the three sequences involved in the CAD/CAM process?

1. Digital impression (scanning)

2. Virtual design (software proposal)

3. Restoration fabrication (milling or grinding)

first sequence of the CAD/CAM process

An intraoral scanner records hard and soft tissue geometry to create a digital impression.

second sequence of the CAD/CAM process

A software design program creates a virtual restoration and allows editing of emergence profile, proximal contact, and occlusion.

third sequence of the CAD/CAM process

A computer-controlled device machines the final restoration from a preformed block of restorative material.

Q: What type of process is commonly used to fabricate CAD/CAM restorations?

A: A subtractive process — grinding or milling using carbide burs or diamonds.

Q: What is the purpose of understanding the three CAD/CAM sequences?

A: To decide how best to implement the technology and categorize systems in the marketplace.

Q: What is the main function of digital impression systems?

A: To record intraoral geometry and transmit files to a dental laboratory for design and fabrication.

Q: Can dentists design restorations using digital impression systems?

A: No, digital impression systems offer minimal opportunity for design input by the dentist.

Q: What advantages do digital impression systems offer over conventional impressions?

A: Greater comfort, efficiency, and accuracy with digital transmission to the lab.

Q: What do chairside CAD/CAM systems include that digital impression systems do not?

A: They include intraoral scanning, design software, and milling units for same-day restorations.

Q: What is the main advantage of chairside CAD/CAM systems?

A: They allow complete control of design, fabrication, and delivery of restorations in a single appointment.

Q: Is CAD/CAM a new restoration type?

A: No, it’s an alternative fabrication method, not a new type of restoration.

Q: What are key factors to consider in CAD/CAM treatment planning?

• Type of restoration (inlay, onlay, crown)

• Material choice

• Occlusal relationships

• Ability to isolate the tooth for delivery

Q: Which factor is more critical: fabrication method or ability to isolate margins?

A: The ability to isolate a subgingival margin for adhesive cementation.

Q: What is one limitation of digital impressions?

A: The size of the intraoral camera may be difficult for patients who can’t open wide.

Q: Why might patients with a severe gag reflex prefer digital impressions?

A: Because digital scanning avoids physical contact with trays or impression materials.

Q: Who conceptualized the first chairside CAD/CAM system and when?

A: Dr. Francois Duret in 1973.

Q: Who introduced the first functioning chairside CAD/CAM prototype, and when? developed the first CAD/CAM block

A: Dr. Werner Mörmann (Swiss prosthodontist) and Marco Brandestini (Italian engineer) in the 1980s.

Q: What was Dr. Mörmann’s vision for CAD/CAM technology?

A: To deliver esthetic ceramic restorations with improved longevity in a single appointment, avoiding polymerization shrinkage seen in composites.

Q: When was the CEREC system introduced and when were the first trials reported?

A: Introduced in 1985; first trials reported in 1987.

Q: What major advancement did the CEREC Omnicam introduce in 2012?

A: It was the first color-streaming, powder-free intraoral camera.

Q: What are the main components of the CEREC system?

• Omnicam (intraoral camera)

• Chairside computer with 3D design software and LCD monitor

• Electronically connected milling unit

Q: What is unique about the newest CEREC milling unit?

A: It can perform both dry grinding and wet milling, allowing in-office dry milling of zirconia.

Q: What is the function of the CEREC SpeedFire furnace?

A: It sinters and glazes zirconia restorations in 10–15 minutes, compared to hours in laboratory sintering.

Q: When was the E4D Dentist System introduced, and by whom?

A: In 2008 by D4D Technologies.

Q: What are the key components of the E4D Dentist System?

• Intraoral laser scanner

• Mobile Design Center with DentaLogic software

• Separate milling unit with dedicated CAM server

Q: What is special about the E4D milling unit?

A: It has two opposing electric motors that automatically switch between three different diamonds based on restoration dimensions.

Q: What scanner was introduced by Carestream in 2013?

A: The CS 3500 powder-free intraoral scanner.

Q: What software and milling unit are used with the Carestream system?

A: CS Solutions Restore software and the CS 3000 milling unit.

A: Through CS Connect, compatible with programs like 3Shape and Exocad.

Q: How does the Carestream system connect with dental laboratories?

Q: What unique features does the CS 3500 intraoral scanner have?

A: A disposable tip and a guiding light that indicates a successful scan.

Q: What restorations can the Carestream system produce chairside?

A: Inlays, onlays, and crowns (limited chairside capability).

Q: What restorations can most chairside CAD/CAM systems fabricate?

A: Inlays, onlays, veneers, and crowns.

Q: What additional restorations can some advanced chairside systems produce?

A: Short-span fixed partial dentures and temporary restorations in-office.

Q: What other applications can be done with certain chairside CAD/CAM systems?

A: Implant abutments, fixed partial dentures, and orthodontic appliances.

Q: What is the main advantage of chairside CAD/CAM systems in general?

A: They enable single-visit fabrication and delivery of high-quality ceramic restorations under the dentist’s full control.

Q: How does occlusal reduction differ between zirconia and porcelain crowns?

A: Full-contour zirconia crowns require less occlusal reduction than leucite-reinforced or feldspathic porcelain crowns.

Q: What unique concept applies to CAD/CAM restorations related to milling?

A: The concept of “undermilling” and “overmilling.”

Q: What causes undermilling or overmilling in CAD/CAM fabrication?

A: Preparation geometries that are smaller than the dimension of the milling instrument.

Q: What happens during overmilling?

A: The instrument removes extra restorative material so the restoration can seat completely.

Q: What happens during undermilling?

A: The instrument fails to remove smaller geometries, leaving excess material that prevents complete seating of the restoration.

Q: How can overmilling and undermilling be minimized?

A: By creating smooth contours, flowing curves, and rounded transition angles in the preparation design.

Q: Why is smooth tooth preparation important for CAD/CAM restorations?

A: It improves scanning accuracy, milling precision, and ensures accurate internal adaptation of the restoration.

Q: What is the main goal of proper tooth preparation in CAD/CAM dentistry?

A: To achieve an accurate fit and optimal strength for the chosen ceramic restoration.

Q: How does tooth preparation for CAD/CAM crowns compare to laboratory-fabricated ceramic crowns?

A: It is essentially the same in terms of design and reduction principles.

Q: What margin design is required for all-ceramic crowns to prevent chipping or fracture?

A: A margin that provides sufficient bulk of ceramic — such as a shoulder, sloped shoulder, or heavy chamfer.

Q: Why should internal angles of CAD/CAM crown preparations be rounded?

A: To facilitate accurate internal adaptation and prevent overcutting during milling.

Q: What is the recommended axial reduction for CAD/CAM monolithic ceramic crowns?

A: 1 to 1.2 mm — since there is no opaque inner coping that needs veneering.

the recommended occlusal reduction for CAD/CAM inlays and onlays / glass ceramic

• 1.5 mm in central fissure and over nonfunctional cusps

• 2 mm over functional cusps

Q: What occlusal thickness can full-contour zirconia crowns safely have?

A: 1 mm without compromising strength (based on in vitro studies).

Q: What is the manufacturer’s current claim for e.maxCAD crowns occlusal reduction?

A: 1 mm occlusal reduction, though it still needs independent validation.

A: Significant undercuts in the preparation.

Q: What common issue can occur in crown preparations due to old restorations or caries excavation

They are accurately captured by the scanner and shown in the virtual CAD model.

Milling tools cannot reproduce this as shape internal areas that would prevent restoration seating

Can be digitally blocked out using CAD software but it’s not recommended because it can lead to internal inaccuracies.

Q: What happens to undercuts that remain during cementation?

A: They are filled with resin cement during crown seating.

Q: What is the preferred way to manage undercuts before scanning?

A: Block them out clinically with an appropriate dentin substitute material before taking the digital scan.

Q: What is the main goal of proper crown preparation for CAD/CAM?

A: To provide adequate strength, precise fit, and accurate internal adaptation of the final restoration.

Q: What type of retention do CAD/CAM inlays and onlays primarily rely on?

A: Adhesive retention — the bond of resin cement to enamel and dentin.

Q: How are CAD/CAM inlay and onlay preparations designed in terms of mechanical retention?

A: They are divergent and minimally retentive, relying on adhesion rather than grooves, slots, or boxes.

Q: Why are CAD/CAM inlay and onlay preparations more conservative than traditional designs?

A: Because they don’t require extensive mechanical resistance features like boxes or grooves.

Q: What should be avoided on the internal aspect of inlay and onlay preparations?

A: Sharp divots or concavities — all internal angles should be rounded.

Q: Where should cavosurface margins be placed?

A: Away from the contact position of opposing cusps and must be smooth and well-defined.

Q: Why should beveled margins be avoided in CAD/CAM inlay and onlay preparations?

A: Because bevels create thin areas of ceramic that are prone to fracture.

ferrule

CAD/CAM onlay restorations doesnt require bc is unnecessary and may interfere with seating due to undermilling or overmilling.

Q: What is the preferred marginal design for CAD/CAM onlays?

A: A butt-joint margin, which provides adequate ceramic thickness at the margin and reduces marginal fracture risk.

Q: What is a disadvantage of the butt-joint margin design?

A: It may create a visible line or demarcation between the restoration and the tooth.

Q: How can the esthetic appearance of the butt-joint margin be improved?

A: By modifying the facial cavosurface margin with a football-shaped diamond at a 45° angle.

Q: What is the benefit of this modified 45° margin design?

A: It allows a smooth ceramic transition over enamel while maintaining bulk strength at the margin.

Q: What did in vitro studies find about modified-margin designs for endodontically treated teeth?

A: They significantly improve marginal and internal fit compared to ferrule or 90° butt-joint designs.

Q: What complications can result from undermilling or overmilling of onlays?

A: They can thicken or thin the restoration improperly, leading to poor fit or reduced strength.

Q: What is the purpose of isolating and retracting soft tissues during CAD/CAM scanning?

A: To ensure the margins and tooth preparation are visible and accurately captured by the digital camera.

Q: What additional scans are required aside from the tooth preparation in CAD/CAM workflow?

A: Scans of the opposing arch and the dentition in maximum intercuspation (from the facial aspect).

Q: How does the software establish occlusal relationships for restoration design?

A: It virtually articulates the opposing models using the scan of facial surfaces.

Q: What does the design software do after identifying the restoration margins?

A: It uses data from adjacent and opposing teeth to generate a proposed virtual restoration.

Q: What aspects of the restoration can the software edit?

A: Emergence profile, occlusal anatomy, occlusal contacts, and proximal contacts.

Q: What process is used to fabricate the restoration from the ceramic block?

A: Subtractive milling or grinding based on the volumetric design created in the software.

Q: How long does it usually take to design and mill a CAD/CAM restoration?

A: Around 10 to 15 minutes for most restorations.

Q: Why might slower machining be preferred for some restorations?

A: To prevent chipping during fabrication, especially for thin margins like porcelain veneers.

Q: What follows after clinical confirmation of anatomy and marginal adaptation?

A: Final glaze firing and/or external surface polishing, then adhesive cementation with resin cement.

Q: What does the copy-design function in CAD/CAM software allow?

A: It allows the operator to copy a pretreatment or prototype tooth form onto the prepared tooth.

Q: When is the copy-design feature especially useful?

A: For restoring fractured abutment teeth in RPDs or anterior restorations using diagnostic wax-ups.

Q: What advantage does the copy-design process provide for RPD abutments?

A: It ensures excellent adaptation to the existing RPD by replicating rest seats and proximal contours.

Q: What is the overall goal of chairside CAD/CAM systems?

A: To digitally design and fabricate restorations in the dental office for same-day delivery.

Q: Which three areas are scanned in a CAD/CAM workflow?

1. The prepared tooth

2. The opposing arch

3. The dentition in maximum intercuspation (facial scan)

Q: What is the first step in designing the restoration after scanning?

A: Identifying the margins of the planned restoration.

Q: What data does the software use to generate a proposed restoration?

A: Data from adjacent and opposing teeth.

Q: What can the operator modify in the restoration design phase?

A: Emergence profile, occlusal anatomy, occlusal contacts, and proximal contact areas.

Q: How are restorations fabricated in CAD/CAM systems?

A: By subtractive milling or grinding an industrial ceramic block based on the design data.

Q: When might longer machining times be needed?

A: For complex restorations such as fixed partial dentures or implant restorations.

Q: Why is slower machining preferred for thin margins like veneers?

A: To reduce the risk of chipping during the milling process.

fine machining modes

A: They refine the surface contour by slowing the block’s advancement or performing a smoother second pass.

Q: What follows the milling process before cementation?

A: Clinical confirmation of anatomy and marginal fit, then final glaze firing and/or polishing.

Q: What unique feature do some CAD/CAM programs offer for design efficiency?

A: A copy-design (biocopy) function that copies a pretreatment or prototype tooth form.

Q: What is the main benefit of the copy-design function?

A: It minimizes editing after the restoration proposal, saving time and improving precision.

Q: How does the copy-design function benefit RPD cases?

A: It allows copying of existing rest seats and proximal contours, ensuring accurate adaptation of the new restoration to the RPD.

Q: How is the copy-design feature beneficial for anterior restorations?

A: It can copy contours from a diagnostic wax-up, allowing for esthetically accurate design.

Q: What happens after copying diagnostic wax-up contours?

A: The contours are digitally refined and then milled into the final ceramic restoration.

Q: What are CAD/CAM restorative materials commonly called?

A: Blocks — dense, homogeneous materials industrially produced under ideal conditions to minimize internal flaws like porosity or voids.