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Digital Imaging and Processing for Restorations
C H A P T E R
14 Digital Imaging and Processing for Restorations O U T L I N E Dental CAD/CAM Systems Digital Impressions Design Software
Processing Devices Clinical Outcomes
349
350
CRAIG’S RESTORATIVE DENTAL MATERIALS
DENTAL CAD/CAM SYSTEMS CAD/CAM, the abbreviation for computer-aided design/computer-aided manufacturing, describes a process in which digital images or models of objects are created and used for the design and fabrication of prototypes or final products using computer numerical control (CNC) or other fabrication methods such as stereolithography. This process has been used for decades in a variety of industries and has become a popular method in restorative dentistry for creating impressions, cast and dies, and provisional and final restorations. Reports of 10-year follow-up studies for one system have shown good outcomes that are improving with each technological enhancement. Dental CAD/CAM systems consist of three components: 1. A scanner or digitizing instrument that transforms physical geometry into digital data. 2. Software that processes the scanned data and creates images of the digitized object. Some systems then enable restorations to be designed for the digitized object. 3. Fabrication technology that transforms the digital data of the restoration into a physical product. Different systems place the fabrication technology in the dental office, dental laboratory, or centralized facility. The two types of CAD/CAM systems for dental offices are acquisition (digital impression) only and scan and mill. Acquisition only systems create digital impressions by capturing images of the preparation and then sending the digital file to a center where a model is made upon which a laboratory technician can fabricate the final restoration. A scan and mill system adds an in-office restoration fabrication device to the digital impression instrument, enabling a restoration to be designed, fabricated, and delivered in one appointment. For the acquisition only system, multiple appointments are required as in conventional indirect restorative care, and a provisional
restoration is placed in the interim while the restoration is being fabricated by a laboratory technician. Scan and mill systems offer the convenience of one appointment preparation, impression, fabrication, and delivery, but includes a waiting period while the restoration is milled and the additional cost of the milling machine. Dental CAD/CAM systems have the following benefits: • Provide improved precision and consistency • Allow the clinician to visualize the preparation on a computer display from many perspectives • Allow the clinician to design the restoration on a computer while visualizing the opposing dentition • Provide a clean and streamlined impression method without the complexity of the many materials required for conventional impressions with an elastomeric material • Offer instant display and feedback for making corrections immediately • Reduce the environmental impact of disposing the materials required for conventional impressions There are several dental CAD/CAM systems currently on the market (Table 14-1). Two of these systems (CEREC AC, Figure 14-1, A, and E4D Dentist, Figure 14-1, B) offer the option of in-office design and milling but also allow design and milling by dental technicians. Two other systems (iTero, Figure 14-2, A, and Lava Chairside Oral Scanner C.O.S., Figure 14-2, B) produce digital impressions that require design and milling at a dental laboratory or milling center. All of these systems can produce models from their digital files.
DIGITAL IMPRESSIONS After the tooth preparation is complete and the tissues are retracted to visualize the tooth margins, the tooth is dried and readied for scanning. Some
TABLE 14.1 Digital Impression Systems Product
Manufacturer
Light Source
Number of Images Required
In-office Milling
Laboratory Milling
3M ESPE Lava Chairside Oral Scanner C.O.S.
3M ESPE (St. Paul, MN)
LED
Continuous video
No
Yes
CEREC AC
Sirona Dental Systems (Charlotte, NC)
Bluecam LED
1-3
Yes
Yes
E4D Dentist
D4D Technologies (Richardson, TX)
Laser
9+
Yes
Yes
iTero
Cadent, Inc. (Carlstadt, NJ)
Laser
21
No
Yes
LED, Light-emitting diode.
14. DIGITAL IMAGING AND PROCESSING FOR RESTORATIONS
A
B
FIGURE 14.1 In-office CAD/CAM systems. A, CEREC AC. B, E4D Dentist. (A, Courtesy of Sirona Dental Systems LLC, Charlotte, NC; B, Courtesy of D4D Technologies, Richardson, TX.)
A
B
351
scanning systems require the use of an oxide powder on the tooth to remove optical highlights from the surface of the preparation and to enhance the scan quality. Scanners use either a series of static images or a stream of video images to capture the geometry of the tooth preparation. CEREC AC with the CEREC Bluecam has a blue light-emitting diode (LED) and camera system, and uses active triangulation to create images of the tooth surface. Static images of the tooth are stitched together to create a single 3-D model. The E4D Dentist system uses a high-speed swept laser beam combined with a camera to obtain a series of 3-D scans of the tooth using the principle of laser triangulation. Laser utilization allows scanning of a variety of different surface types and colors without the need for a contrast agent (powder). These scans are registered together to form a single 3-D model. The iTero uses parallel confocal imaging to create 100,000 point maps at 300 focal depths spaced 50 micrometers apart. A series of 15 to 30 scanned images record the preparation, opposing teeth, and the occlusal relationship. The LAVA C.O.S. scanner is based on the principle of active optical wavefront sampling, in which 3-D information is collected by a single lens imaging system. Three sensors collect video data simultaneously from different perspectives. Twenty 3-D data sets are captured per second. For a complete digital volume model, about 2400 3-D data sets or 24 million data points per arch are reconstructed.
C
FIGURE 14.2 Digital impression systems. A, iTero. B, Lava Chairside Oral Scanner C.O.S. C, CEREC AC. (A, Courtesy of Cadent, Inc., Carlstadt, NJ; B, Courtesy of 3M ESPE, St. Paul, MN; C, Courtesy of Sirona, Charlotte, NC.)
352
CRAIG’S RESTORATIVE DENTAL MATERIALS
TABLE 14.2 Digital Impression Systems—Choice of Materials (2010) Product
Company
PFM/Gold
Lithium Disilicate
Leucite- reinforced
Zirconia
iTero
Cadent, Inc.
Yes
Yes
Yes
Yes
E4D Dentist
D4D Technologies
Yes (via E4D Sky)
Yes
Yes
Yes (via E4D Sky)
CEREC AC
Sirona Dental Systems
Yes (via CEREC Connect)
Yes
Yes
Yes (via CEREC Connect)
3M ESPE Lava Chairside Oral Scanner C.O.S.
3M ESPE
Yes
Yes
Yes
Yes
Courtesy of John M. Powers, Ann Arbor, MI.
DESIGN SOFTWARE Each system includes proprietary software for the visualization of the scanned data and design of restorations. A wide variety of restorations can be designed, including inlays, onlays, full crowns, and fixed dental prostheses. The digital cast and dies can be visualized from any perspective, with or without the opposing dentition. Restorations are designed interactively by the clinician and computer, adapting the contours to harmonize with the adjacent and opposing teeth. A virtual “clay” is used to mold the restoration to the correct emergence profile, interproximal contact, and occlusal scheme. The opposing dentition can be moved through excursive paths to further develop a functional occlusal profile.
PROCESSING DEVICES Milling centers and dental laboratories produce restorations directly from the digital impression and restoration design data. Restorations can be milled from a variety of materials such as composites, feldspathic porcelain, leucite-reinforced ceramic, lithium disilicate ceramic, and zirconia (Table 14-2). Wax patterns and acrylic provisional restorations can also be milled. The digitally produced models can be used to produce restorations by traditional methods in the dental laboratory. Milling devices are distinguished by the number of milling axes. The quality of the final product does not necessarily depend on the number of milling axes, but it does affect the level of geometric complexity that can be produced. Three-axis devices are capable of movement in three spatial directions. They are not capable of milling axis divergences and convergences. Three-axis devices can turn the material block used for milling by 180 degrees during processing. Four-axis devices add the ability to rotate the material block infinitely. This enables the fabrication of a fixed prosthesis with a large vertical height difference. Five-axis devices add the ability to rotate the
milling spindle so complex geometries can be milled in sections. This enables geometries such as converging abutment teeth to be accommodated. Metals, resins, composites, and ceramics can be milled by the processing devices. Commercially pure titanium, titanium alloys, and cobalt chrome alloys are metals commonly used in the devices. Resins can be milled to create lost wax frames for casting and also for long-term provisional prostheses. Composite blanks that are prefabricated to mimic enamel and dentin in their translucency and color can be milled to create final anterior restorations. Zirconia, described in Chapter 11, is a high performance ceramic with excellent mechanical characteristics. It is used in milling devices for crowns, fixed partial prostheses, and implant abutments.
CLINICAL OUTCOMES The performance of restorations produced in CAD/ CAM systems have improved dramatically in the last decade. An older perception of poor marginal integrity associated with CAD/CAM restorations is no longer true. Enhancements in image capture, design software, and milling technology along with improvements in materials have all contributed to superior clinical outcomes. Patient selection and attention to margin design and tissue retraction are important factors, as they should be for all restorative procedures. In recent studies of zirconia-based restorations, digital impressions resulted in better quality of contacts, better fit, and better occlusion than elastomeric impressions (Table 14-3). Digital impressions typically result in 33% shorter seating/adjustment time and fewer incidents of remakes when compared to elastomeric impressions. In a 10-year study of 308 ceramic restorations placed in 74 patients between 1991 and 1994, the restoration survival rate was 94.7% after 5 years and 85.7% after 10 years, which is comparable to the survival rates of cast gold restorations. A systematic review of four studies that reported on implantsupported CAD/CAM fabricated restorations found
14. DIGITAL IMAGING AND PROCESSING FOR RESTORATIONS
TABLE 14.3 Comparison of Restorations Made by Digital Impression vs. Elastomeric Impressions
Parameter
Digital Impression (% perfect)
Elastomeric Impression (% perfect)
Quality of contacts
62
46
Fit
92
71
Occlusion
74
48
Modified from Farah JW, Brown L: Dent. Advis. Res. Rpt. 22, 1-3, 2009.
353
a cumulative 5-year survival rate of all-ceramic single crowns of 100% (95% CI: 92.4% to 100%). A systematic review of studies that reported on single-tooth restorations fabricated with CAD/CAM technology from 1985 to 2007 revealed a failure rate of 1.75% per year, calculated per 100 restoration years from a total of 1957 restorations and a mean exposure time of 7.9 years. The review estimated a total 5-year survival rate of 91.6% (95% CI: 88.2% to 94.1%). The long-term survival rates for CAD/CAM single-tooth restorations were found to be similar to restorations fabricated with conventional methods.
SELECTED PROBLEMS PROBLEM 1 What types of materials can be milled with CAD/ CAM systems?
Solution Restorations can be milled from a variety of materials such as composites, feldspathic porcelain, leucite-reinforced ceramic, lithium disilicate ceramic, and zirconia.
PROBLEM 2 Why is it necessary to dust the preparation with titanium oxide powder for some systems?
preparation is void of specular reflection. The powder provides surfaces that are uniform in color and reflectance.
PROBLEM 3 Is the long-term survival rate of CAD/CAM fabricated restorations similar to those fabricated using conventional methods?
Solution Yes. Systematic reviews found 5-year survival rates between 92% and 95%, which compare favorably with restorations fabricated by conventional methods.
Solution CAD/CAM systems use video or static imaging methods that provide the best images when the
Bibliography Anderson S: E4D Dentist, E4D Studio and E4D Labworks along the digital skyway, Dent Advis Clin Case Rpt 17: 1–3, 2010. Beuer F, Schweiger J, Edelhoff D: Digital dentistry: an overview of recent development for CAD/CAM generated restorations, Br Dent J 204(9):505–511, 2008. Farah JW, Brown L: Integrating the 3M ESPE Lava Chairside Oral Scanner C.O.S. into daily clinical practice, Dent Advis Clin Case Rpt 12:1–4, 2009. Farah JW, Brown L: Integrating iTero into a busy dental practice, Dent Advis Clin Case Rpt 16:1–3, 2009. Farah JW, Brown L: Comparison of the fit of crowns: 3M ESPE Lava Chairside Oral Scanner C.O.S. vs. traditional impressions, Dent Advis Res Rpt 22:1–3, 2009. Farah JW, Powers JM: CAD/CAM update, Dent Advis 26(7):1, 2009. Farah JW, Powers JM: Digital impressions, Dent Advis 27(6):1, 2010. Fasbinder DJ: Digital dentistry: Innovation for restorative treatment, Digital Age Dentistry, Compendium of Continuing Education in Dentistry 31(Spec Iss 4):2–11, 2010.
Giannetopoulos S, van Noort R, Tsitrou E: Evaluation of the marginal integrity of ceramic copings with different marginal angles using two different CAD/CAM systems, J Dent 38(12):980–986, 2010. Harder S, Kern M: Survival and complications of computer aided-designing and computer-aided manufacturing vs. conventionally fabricated implant-supported reconstructions: a systematic review, Clin Oral Implants Res 4: 48–54, 2009. Schroder BK, Brown C: Use of selective open architecture in digital restoration fabrication, In Digital Age Dentistry, Compendium of Continuing Education in Dentistry 31(Spec Iss 4):15–22, 2010. Wittneben J-G, Wright RF, Weber H-P, Gallucci GO: A systematic review of the clinical performance of CAD/ CAM single-tooth restorations, Int J Prosthodont 22: 466–471, 2009. Zimmer G, Gohlich O, Ruttemann S, Lang H, Raab WH, Barthel CR: Long-term survival of Cerec restorations: a 10-year study, Oper Dent 33(5):484–487, 2008.
14 Digital Imaging and Processing for Restorations O U T L I N E Dental CAD/CAM Systems Digital Impressions Design Software
Processing Devices Clinical Outcomes
349
350
CRAIG’S RESTORATIVE DENTAL MATERIALS
DENTAL CAD/CAM SYSTEMS CAD/CAM, the abbreviation for computer-aided design/computer-aided manufacturing, describes a process in which digital images or models of objects are created and used for the design and fabrication of prototypes or final products using computer numerical control (CNC) or other fabrication methods such as stereolithography. This process has been used for decades in a variety of industries and has become a popular method in restorative dentistry for creating impressions, cast and dies, and provisional and final restorations. Reports of 10-year follow-up studies for one system have shown good outcomes that are improving with each technological enhancement. Dental CAD/CAM systems consist of three components: 1. A scanner or digitizing instrument that transforms physical geometry into digital data. 2. Software that processes the scanned data and creates images of the digitized object. Some systems then enable restorations to be designed for the digitized object. 3. Fabrication technology that transforms the digital data of the restoration into a physical product. Different systems place the fabrication technology in the dental office, dental laboratory, or centralized facility. The two types of CAD/CAM systems for dental offices are acquisition (digital impression) only and scan and mill. Acquisition only systems create digital impressions by capturing images of the preparation and then sending the digital file to a center where a model is made upon which a laboratory technician can fabricate the final restoration. A scan and mill system adds an in-office restoration fabrication device to the digital impression instrument, enabling a restoration to be designed, fabricated, and delivered in one appointment. For the acquisition only system, multiple appointments are required as in conventional indirect restorative care, and a provisional
restoration is placed in the interim while the restoration is being fabricated by a laboratory technician. Scan and mill systems offer the convenience of one appointment preparation, impression, fabrication, and delivery, but includes a waiting period while the restoration is milled and the additional cost of the milling machine. Dental CAD/CAM systems have the following benefits: • Provide improved precision and consistency • Allow the clinician to visualize the preparation on a computer display from many perspectives • Allow the clinician to design the restoration on a computer while visualizing the opposing dentition • Provide a clean and streamlined impression method without the complexity of the many materials required for conventional impressions with an elastomeric material • Offer instant display and feedback for making corrections immediately • Reduce the environmental impact of disposing the materials required for conventional impressions There are several dental CAD/CAM systems currently on the market (Table 14-1). Two of these systems (CEREC AC, Figure 14-1, A, and E4D Dentist, Figure 14-1, B) offer the option of in-office design and milling but also allow design and milling by dental technicians. Two other systems (iTero, Figure 14-2, A, and Lava Chairside Oral Scanner C.O.S., Figure 14-2, B) produce digital impressions that require design and milling at a dental laboratory or milling center. All of these systems can produce models from their digital files.
DIGITAL IMPRESSIONS After the tooth preparation is complete and the tissues are retracted to visualize the tooth margins, the tooth is dried and readied for scanning. Some
TABLE 14.1 Digital Impression Systems Product
Manufacturer
Light Source
Number of Images Required
In-office Milling
Laboratory Milling
3M ESPE Lava Chairside Oral Scanner C.O.S.
3M ESPE (St. Paul, MN)
LED
Continuous video
No
Yes
CEREC AC
Sirona Dental Systems (Charlotte, NC)
Bluecam LED
1-3
Yes
Yes
E4D Dentist
D4D Technologies (Richardson, TX)
Laser
9+
Yes
Yes
iTero
Cadent, Inc. (Carlstadt, NJ)
Laser
21
No
Yes
LED, Light-emitting diode.
14. DIGITAL IMAGING AND PROCESSING FOR RESTORATIONS
A
B
FIGURE 14.1 In-office CAD/CAM systems. A, CEREC AC. B, E4D Dentist. (A, Courtesy of Sirona Dental Systems LLC, Charlotte, NC; B, Courtesy of D4D Technologies, Richardson, TX.)
A
B
351
scanning systems require the use of an oxide powder on the tooth to remove optical highlights from the surface of the preparation and to enhance the scan quality. Scanners use either a series of static images or a stream of video images to capture the geometry of the tooth preparation. CEREC AC with the CEREC Bluecam has a blue light-emitting diode (LED) and camera system, and uses active triangulation to create images of the tooth surface. Static images of the tooth are stitched together to create a single 3-D model. The E4D Dentist system uses a high-speed swept laser beam combined with a camera to obtain a series of 3-D scans of the tooth using the principle of laser triangulation. Laser utilization allows scanning of a variety of different surface types and colors without the need for a contrast agent (powder). These scans are registered together to form a single 3-D model. The iTero uses parallel confocal imaging to create 100,000 point maps at 300 focal depths spaced 50 micrometers apart. A series of 15 to 30 scanned images record the preparation, opposing teeth, and the occlusal relationship. The LAVA C.O.S. scanner is based on the principle of active optical wavefront sampling, in which 3-D information is collected by a single lens imaging system. Three sensors collect video data simultaneously from different perspectives. Twenty 3-D data sets are captured per second. For a complete digital volume model, about 2400 3-D data sets or 24 million data points per arch are reconstructed.
C
FIGURE 14.2 Digital impression systems. A, iTero. B, Lava Chairside Oral Scanner C.O.S. C, CEREC AC. (A, Courtesy of Cadent, Inc., Carlstadt, NJ; B, Courtesy of 3M ESPE, St. Paul, MN; C, Courtesy of Sirona, Charlotte, NC.)
352
CRAIG’S RESTORATIVE DENTAL MATERIALS
TABLE 14.2 Digital Impression Systems—Choice of Materials (2010) Product
Company
PFM/Gold
Lithium Disilicate
Leucite- reinforced
Zirconia
iTero
Cadent, Inc.
Yes
Yes
Yes
Yes
E4D Dentist
D4D Technologies
Yes (via E4D Sky)
Yes
Yes
Yes (via E4D Sky)
CEREC AC
Sirona Dental Systems
Yes (via CEREC Connect)
Yes
Yes
Yes (via CEREC Connect)
3M ESPE Lava Chairside Oral Scanner C.O.S.
3M ESPE
Yes
Yes
Yes
Yes
Courtesy of John M. Powers, Ann Arbor, MI.
DESIGN SOFTWARE Each system includes proprietary software for the visualization of the scanned data and design of restorations. A wide variety of restorations can be designed, including inlays, onlays, full crowns, and fixed dental prostheses. The digital cast and dies can be visualized from any perspective, with or without the opposing dentition. Restorations are designed interactively by the clinician and computer, adapting the contours to harmonize with the adjacent and opposing teeth. A virtual “clay” is used to mold the restoration to the correct emergence profile, interproximal contact, and occlusal scheme. The opposing dentition can be moved through excursive paths to further develop a functional occlusal profile.
PROCESSING DEVICES Milling centers and dental laboratories produce restorations directly from the digital impression and restoration design data. Restorations can be milled from a variety of materials such as composites, feldspathic porcelain, leucite-reinforced ceramic, lithium disilicate ceramic, and zirconia (Table 14-2). Wax patterns and acrylic provisional restorations can also be milled. The digitally produced models can be used to produce restorations by traditional methods in the dental laboratory. Milling devices are distinguished by the number of milling axes. The quality of the final product does not necessarily depend on the number of milling axes, but it does affect the level of geometric complexity that can be produced. Three-axis devices are capable of movement in three spatial directions. They are not capable of milling axis divergences and convergences. Three-axis devices can turn the material block used for milling by 180 degrees during processing. Four-axis devices add the ability to rotate the material block infinitely. This enables the fabrication of a fixed prosthesis with a large vertical height difference. Five-axis devices add the ability to rotate the
milling spindle so complex geometries can be milled in sections. This enables geometries such as converging abutment teeth to be accommodated. Metals, resins, composites, and ceramics can be milled by the processing devices. Commercially pure titanium, titanium alloys, and cobalt chrome alloys are metals commonly used in the devices. Resins can be milled to create lost wax frames for casting and also for long-term provisional prostheses. Composite blanks that are prefabricated to mimic enamel and dentin in their translucency and color can be milled to create final anterior restorations. Zirconia, described in Chapter 11, is a high performance ceramic with excellent mechanical characteristics. It is used in milling devices for crowns, fixed partial prostheses, and implant abutments.
CLINICAL OUTCOMES The performance of restorations produced in CAD/ CAM systems have improved dramatically in the last decade. An older perception of poor marginal integrity associated with CAD/CAM restorations is no longer true. Enhancements in image capture, design software, and milling technology along with improvements in materials have all contributed to superior clinical outcomes. Patient selection and attention to margin design and tissue retraction are important factors, as they should be for all restorative procedures. In recent studies of zirconia-based restorations, digital impressions resulted in better quality of contacts, better fit, and better occlusion than elastomeric impressions (Table 14-3). Digital impressions typically result in 33% shorter seating/adjustment time and fewer incidents of remakes when compared to elastomeric impressions. In a 10-year study of 308 ceramic restorations placed in 74 patients between 1991 and 1994, the restoration survival rate was 94.7% after 5 years and 85.7% after 10 years, which is comparable to the survival rates of cast gold restorations. A systematic review of four studies that reported on implantsupported CAD/CAM fabricated restorations found
14. DIGITAL IMAGING AND PROCESSING FOR RESTORATIONS
TABLE 14.3 Comparison of Restorations Made by Digital Impression vs. Elastomeric Impressions
Parameter
Digital Impression (% perfect)
Elastomeric Impression (% perfect)
Quality of contacts
62
46
Fit
92
71
Occlusion
74
48
Modified from Farah JW, Brown L: Dent. Advis. Res. Rpt. 22, 1-3, 2009.
353
a cumulative 5-year survival rate of all-ceramic single crowns of 100% (95% CI: 92.4% to 100%). A systematic review of studies that reported on single-tooth restorations fabricated with CAD/CAM technology from 1985 to 2007 revealed a failure rate of 1.75% per year, calculated per 100 restoration years from a total of 1957 restorations and a mean exposure time of 7.9 years. The review estimated a total 5-year survival rate of 91.6% (95% CI: 88.2% to 94.1%). The long-term survival rates for CAD/CAM single-tooth restorations were found to be similar to restorations fabricated with conventional methods.
SELECTED PROBLEMS PROBLEM 1 What types of materials can be milled with CAD/ CAM systems?
Solution Restorations can be milled from a variety of materials such as composites, feldspathic porcelain, leucite-reinforced ceramic, lithium disilicate ceramic, and zirconia.
PROBLEM 2 Why is it necessary to dust the preparation with titanium oxide powder for some systems?
preparation is void of specular reflection. The powder provides surfaces that are uniform in color and reflectance.
PROBLEM 3 Is the long-term survival rate of CAD/CAM fabricated restorations similar to those fabricated using conventional methods?
Solution Yes. Systematic reviews found 5-year survival rates between 92% and 95%, which compare favorably with restorations fabricated by conventional methods.
Solution CAD/CAM systems use video or static imaging methods that provide the best images when the
Bibliography Anderson S: E4D Dentist, E4D Studio and E4D Labworks along the digital skyway, Dent Advis Clin Case Rpt 17: 1–3, 2010. Beuer F, Schweiger J, Edelhoff D: Digital dentistry: an overview of recent development for CAD/CAM generated restorations, Br Dent J 204(9):505–511, 2008. Farah JW, Brown L: Integrating the 3M ESPE Lava Chairside Oral Scanner C.O.S. into daily clinical practice, Dent Advis Clin Case Rpt 12:1–4, 2009. Farah JW, Brown L: Integrating iTero into a busy dental practice, Dent Advis Clin Case Rpt 16:1–3, 2009. Farah JW, Brown L: Comparison of the fit of crowns: 3M ESPE Lava Chairside Oral Scanner C.O.S. vs. traditional impressions, Dent Advis Res Rpt 22:1–3, 2009. Farah JW, Powers JM: CAD/CAM update, Dent Advis 26(7):1, 2009. Farah JW, Powers JM: Digital impressions, Dent Advis 27(6):1, 2010. Fasbinder DJ: Digital dentistry: Innovation for restorative treatment, Digital Age Dentistry, Compendium of Continuing Education in Dentistry 31(Spec Iss 4):2–11, 2010.
Giannetopoulos S, van Noort R, Tsitrou E: Evaluation of the marginal integrity of ceramic copings with different marginal angles using two different CAD/CAM systems, J Dent 38(12):980–986, 2010. Harder S, Kern M: Survival and complications of computer aided-designing and computer-aided manufacturing vs. conventionally fabricated implant-supported reconstructions: a systematic review, Clin Oral Implants Res 4: 48–54, 2009. Schroder BK, Brown C: Use of selective open architecture in digital restoration fabrication, In Digital Age Dentistry, Compendium of Continuing Education in Dentistry 31(Spec Iss 4):15–22, 2010. Wittneben J-G, Wright RF, Weber H-P, Gallucci GO: A systematic review of the clinical performance of CAD/ CAM single-tooth restorations, Int J Prosthodont 22: 466–471, 2009. Zimmer G, Gohlich O, Ruttemann S, Lang H, Raab WH, Barthel CR: Long-term survival of Cerec restorations: a 10-year study, Oper Dent 33(5):484–487, 2008.