An Overview of Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) in Restorative Dentistry

Document Type: Review Article

Authors

1 Stomatology Research Center, School of Stomatology, China Medical University, Shenyang, Liaoning Province, P.R. China

2 Orthodontics Department, School of Stomatology, China Medical University, Shenyang, Liaoning Province, P.R. China

Abstract

Objective: To review the current knowledge of CAD/CAM in dentistry and its development in the mentioned field. Sources: An electronic search was conducted across Ovid Medline, complemented by manual search across individual databases, such as Cochrane, Medline and ISI Web of Science databases and Google Scholar for literature analysis on the mentioned topic. The studies were reviewed thoroughly. This paper summarizes the current scientific and clinical opinions through a brief overview regarding the preferred way of utilizing CAD/CAM in dentistry.  Conclusions: The importance of CAD/CAM systems has seen a dramatic development in the number of products and procedures over last decades, with a concomitant rise in publications on the topic. Literature suggests that using this technology permits carrying out dental treatments feasibly particularly for fixed dental appliances. Based on the previous findings, it is concluded that in office CAD/CAM technique appears to be the most common technique currently available, which is rapid, easy and keeps time. CAD/CAM systems are variable; therefore, using the right system with a logical approach for treating patients are quite mandatory.

Keywords

Main Subjects


Introduction

During the last quarter of the 20th century, there was a breakthrough in dentistry regarding introducing a new technology, i.e. the Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) system (1-4). A new age started with the appearance of this technology (5). The notion of using this recent technology in dentistry, particularly restorative dentistry, commenced with diverse research approaches. For instance, in the 1970s Francois Duret in France introduced the Duret system (3, 6-12); which was named after him and supported by “Hennson International”(13). Using this system, Duret pioneered optical impression from which design and milling of an abutment tooth were possible (1). However, due to the complexity, large size, inadequate digitizing and high cost, this system did not take off in dental markets (7). Later another system launched into the market named “Sopha System”, which was supported by “Sopha Bioconcept” (1, 3, 6, 7). Then, in the 1977 Young and Atlschuler (6, 7, 13-15) suggested an optical impression method, which depended on laser holography.

Subsequently, in the 1980s at the University of Zurich in Switzerland, Dr. Werner Mormann and Marco Brandestini introduced the first commercial CAD/CAM system to a dental clinic (8, 10, 16). This technology made major changes in dental practice by permitting dentists to finish multiple works for ceramic restorations such as full crowns, inlays, onlays and veneers in a clinic or laboratory (16, 17).

The first chair-side ceramic inlay with the CEREC1 CAD/CAM system (Sirona “Siemens old name of Sirona” Dental System, Charlotte, NC.) was fabricated and used in 1985  (14, 16, 18-20). However, a study by Culp and Touchstone showed that this system was introduced earlier in 1982 (21). In addition, Freedman in a literature review argued that this system was introduced into the market in the 1987 (22). 

Following this period, Dr. Anderson attempted to introduce the Procera System (1, 3). This system enables the machining of titanium copings by spark erosion. Using this system, Anderson tried to carry out a process of composite veneered restoration (1). Eventually, it becomes a popular system in the worldwide to fabricate all-ceramic frameworks through a centralized network process with satellite digitizers (1).

Apart from these systems, several other groups have tried to introduce others from 1985 to 1990s such as the Aoki group in Japan, Diane Rekow’s in Minnesota and Reggie’s at Alabama University (6). The most developed amongst the various systems was that of Diane Rekow, which was supported by the Bego company under a particular name, the so-called the DentiCAD or Minnesota system (6). This system provided 3D measurement on the teeth surface via stereophotogrammetry. However, it was complicated to operate. Therefore, it did not remain in use for long, only until 1994 (6). Then, the technological revolution in dentistry further developed. Hence, there were certain changes, and various other systems were developed.  For instance, the DCP analogue system, the Celay system, the DFE (Krrup) system and the Erosonic system (ESPE) (13). Since then, several varieties of commercial CAD/CAM systems were developed.

In the past, the CAD/CAM system was used either at the laboratory side or in-office “chair-side” (23). However, recently it has become feasible to merge the concepts. Hence, both dental professionals and experienced technicians have benefited (23). Therefore, CAD/CAM systems have branched into other dental fields such as oral surgery, periodontology, orthodontic treatment, implantology and maxillofacial surgery; it is no longer found only in the restorative field. These are signs for a significant role and ongoing evolution of this technology, from simple fabricated machine to recently developed one (24). This paper aims to show a short glance relating to CAD/CAM system and focusing on certain other aspects.

 

CAD/CAM Components

CAD/CAM systems are composed of three major parts: First, a data acquisition unit, which collects the data from the area of the preparation, adjacent and opposing structures. Then converts them to virtual impressions (25) through intraoral scanners (in-office CAD/CAM or in-office CAD or image acquisition systems) or indirectly using a stone model generated through making a conventional impression. Second, the software used for designing virtual restorations on a virtual working cast and then computing the milling parameters. Third, a computerized milling device used for manufacturing the restoration from a solid block of restorative material or additive manufacturing.

 

General classification of CAD/CAM systems

The CAD/CAM systems are classified into laboratory systems and chairside systems. The laboratory system is further classified into laboratory CAD/CAM, in which the company has its own scanner and milling units such as (Amann Girbach, 3M ESPE, Sirona Dental Systems, Zirkon Zahn, vhf camfacture AG, Weiland Dental, Pou-Yuen and U-Best Dental, Planmeca, KaVo Dental, Dentsply Prosthetics). The CAD unit in which the company has only the scanner (e.g. D2000, 3 Shape; Dental Wings 7 series, Dental Wings; IScan D104, Imetric 3D SA; Ceramill Map, Amann Girrbach; Activity 850 3D, Smart Optics). The CAM unit in which the company retains the milling machine unit such as (DWX-50, Roland DGA Corporation; inLab MC X5, Sirona; M5, Zirkonzahn; Tizian Cut 5 Smart, Schütz Dental; S2 Model, vhf camfacture AG; Ceramill Motion 2, Amann Girrbach).

The chairside CAD/CAM system is further classified into: first, chairside CAD/CAM system in which the company has its own scanner and milling units (Sirona and Planmeca). Second,  image acquisition system in which the company has only a scanner without designing capabilities (e.g. True Definition Scanner, 3M ESPE; iTero, Align Technology, Inc; Trios, 3Shape; Apollo DI, Sirona; CS 3500, Carestream Dental LLC). These, in turn, must be connected to an open laboratory scanner for designing of the restoration.

CAD/CAM can be further classified into open and closed systems (26) according to data sharing. Closed systems offer all CAD/CAM procedures, including data acquisition, virtual design, and restoration manufacturing by the same company. Further, all the steps are integrated into one system, and there is no interchangeability between different systems from other companies. Open systems allow the adoption of the original digital data by CAD software and CAM devices from various companies (26).

The laboratory CAD systems must always be an open system because after acquiring the data and designing the restoration, the data has to be stored in an STL file “Stereolithography or Standard Tessellation Language. However, many manufacturers use their own specific data formats, with the result that data for the construction programs will not be compatible with each other” (27), and then sent to an open laboratory CAM system, which accepts that type of STL file from that laboratory CAD system where the restoration will be fabricated. Additionally, the image acquisition unit is always an open system, and the STL file of a certain restoration can be accepted by an open laboratory CAD system for the restoration to be designed and then sent to an open CAM system for the restoration or model to be fabricated.

When complex restorations are intended to be fabricated such as an implant bar or attachments, the model can be scanned through open laboratory CAD/CAM or laboratory CAD systems and the STL file sent to an outsource production center such as (InfiniDent, Sirona; Procera, Nobel Biocare; Lava, 3M ESPE; TurboDent, Pou-Yuen and U-Best Dental; Ceram M-center, Amann Girrbich; PlanEasyMillTM, Planmeca) for restoration designing and fabrication. In addition, when a  digital  model  is  intended  to  be fabricated  through  scanning  of  the  teeth   intraorally,   the STL file of the image acquisition unit or open chairside CAD/ CAM system can be sent to  an  outsource  production  center for the digital model to be fabricated through milling or additive technology. General classification of CAD/CAM system is summerized in Table 1 (5, 22).

 

 

 

 

Table 1. General classification of CAD/CAM system (5, 22)

Types

Descriptions

1- Chairside production

It saves time and offers the patient indirectly fabricated restoration at one appointment.

In general CEREC system (Sirona) gives this opportunity.

This system was the 1st CAD/CAM sytem and currently the 4th recent generation available in markets.

The benefit is the ability to use software (3D) program and obtaining precise reconstruction of the occlusal surface. 

2- Labrotary production

It is similar to traditional working sequence between dentist and technician.

3D data are produced depending on master die.

Takes longer time than 1st type. Permit technician to work more carefully for final design fabrication.

3- Centralized production

Satellite scanners are connected with a production center through the Internet.

This is an open system, compared to other systems, which are closed type.

 

 

 


Development of CEREC systems and comparison to former generations

CEREC; is the abbreviation of “Chairside Economic Reconstruction of Esthetic Ceramic” (1); however, in certain literature, this acronym is just explained by the terms “Ceramic Reconstruction” (19, 28). This system is more applicable than other available systems (29). The 1st version was launched onto the market in 1985 (16, 30), whereas Akbar et al. argued that that CEREC 1 was introduced in 1984 (29). Then, after technical improvements, the next generation of CEREC 2 was fabricated and introduced to dental clinics in 1996 (1).

Recently, Akbar et al have examined CEREC 3 (29) in a similar way and found that this system was identical to the second system. However, other studies showed that CEREC 3 is better than CEREC 2 regarding marginal integrity (1,7). Previous literatures have established that CEREC 2 can be utilized to fabricate partial crowns, inlays, onlays and overlays (31). However, CEREC 3 can be used for three-unit bridge, veneers, onlays, inlays, full and/or partial crowns and copings (31). For specific crown designs such as veneers, inlays, onlays and temporary bridges CEREC 4 and 4.5 are the most appropriate systems.

Different restorative materials can be used with the CEREC system including; VITA Blocs Spinell, Zirconia, Alumina, Zirconia Mark II, YZ (VITA Zahnfabric, Bad Säckingen, Germany). Lucite reinforced ProCad (Ivoclar vivadent, Schann Liechtenstein) (31, 32).

 

Compare CEREC system properties to earlier versions systems

There are certain properties presented with the previous systems; the infra-red intraoral camera, and an optical image can be obtained with CEREC 2, CEREC 3, and CEREC 4. However, the two last versions improved in such a way that blue ray enhanced better properties in comparison to previous generations.  In addition, the design of models can be fabricated (Extrapolation, Function and Correlation).

The CEREC 3 and later versions have the ability to complete all the work in one appointment without the need for a second visit. In addition, it does not require to take of impressions or making a temporary restoration, i.e. preparation, designing and milling process can be completed in one visit (8, 28).

Due to significant progress in both hard and software computer programs, varieties of laboratory CAD/CAM systems have been launched into the market. In 2002, CEREC inLab was launched into the market. With the CEREC InLab, a die can be either scanned with a laser scanner automatically or separately through inEos system.

Then, a 3D image has been achieved by computer program the restoration is designed (28, 33). The subtracting process through milling chamber can be carried out automatically (7).

Recently, both the InEos and CEREC inLab system can be used as a combined unit that can conduct each scanning and milling independently. The former system was previously used only for milling or scanning purpose. However, both processes can be carried out together in combination.

With CEREC, two types of laser mode scanning are present. The overview can be used for multiple works such as crowns, inlays, onlays and bridges. It has the ability to scan upper and lower arches for occlusal restoration. The  rotational scanning mode can be also used for taking eight scanning pictures, as indicated for a single die or unit (28)   

The modern versions of the CEREC software 4 and 4.5 (Bensheim, Germany) were also released in last few years into the market by Sirona. Major steps in CEREC system development are shown in Table 2 (19).

 

 

 

Table 2. Major steps in the development of CEREC CAD/CAM system (19)

Year

Hardware

Software capability

Restoration Type

Developer

1980

Basic concept

2D

Inlays

Mormann and Brandestini (University of Zurich)

1985

CEREC1

2D

First chairside inlay

Mormann and Brandestini (Brains, Zurich)

1988

CEREC1

2D

Inlays, onlays and veneers

Mormann and Brandestini

1994

CEREC2

2D

Copings, Partial and full crowns

Siemens (Munich,Germany)

2000

CEREC3 and InLab

2D

3 and 4 unit bridge frames

Sirona (Bensheim, Germany)

2003

CEREC3 and InLab

3D

3 and 4 unit bridges

Sirona (Bensheim, Germany)

2005

CEREC3 and InLab

3D

Automatic virtual occlusal adjustment

Sirona (Bensheim, Germany)

2011-2015

CEREC 4 and CEREC 4.5

3D

Automatic virtual occlusal adjustment, full arch recording

Sirona (Bensheim, Germany)

 

 

 

 

Strengths and weaknesses of CEREC CAD/CAM systems

The system lies on the triangulation technique which requires a uniform reflective surface since different materials such as dentin, amalgam, resin, gum reflect light differently. Therefore, it is necessary to coat the teeth with reflective powders before the scanning to provide uniformity in the reflectivity of the surfaces to be scanned precisely. Earlier versions of CEREC® employed an acquisition camera with an infrared laser light source. The Bluecam version employs blue light-emitting diodes (LEDs); the intense blue light with a shorter wavelength projected by the blue LEDs allows for greater precision of the produced virtual model (34). Even at the periphery, the images are free from distortion, so multiple images such as a complete quadrant can be stitched together with high accuracy (34).

The CEREC® AC Bluecam offers image stabilization systems. This means that the practitioner does not have to rest the camera wand on a tooth to get a steady focus. The camera automatically captures an image when the wand is motionless, avoiding the need for a foot pedal as the previous model required. Recently, with further development of CEREC software, it is possible to scan full arches. Earlier versions of the device made a single image from one perspective. At the end of the scanning stage, the preparation is shown on the monitor and can be viewed from every angle to focus or magnify areas of the preparation (35).

 

Restorative materials for CAD/CAM system

With using CAD/CAM systems, operators can fabricate restorations from an array of materials. These include ceramics, metal alloys and various composites. The ceramics currently being used for restorations are predominantly alumina including those subsequently infiltrated with glass, zirconia and porcelain based ceramics (36).

CAD/CAM systems based on machining of
pre-sintered alumina or zirconia blocks in combination with specially designed veneer ceramics satisfy the demand for all-ceramic posterior crowns and fixed partial dentures. Many restorative materials are available for use as CAD/CAM restorations as shown in Table 3 (37). Common ceramic materials used in earlier dental.
CAD/ CAM restorations have been machinable glass ceramics such as Dicor (Dentsply Caulk, Milford, DE 19963) or Vita Mark II (Vident, Bera, CA 92821). Although monochromatic, these ceramic materials offer excellent esthetics, biocompatibility, excellent color stability, low thermal conductivity, and excellent wear resistance (38). They have been successfully used as inlays, onlays (39), veneers and crowns (40). However, Dicor and Vita Mark II are not strong enough to sustain occlusal loading when used for posterior crowns (41). Therefore, alumina and zirconia materials are now being widely accepted as dental restorative materials. These ceramic agents may not be cost-effective without the aid of CAD/CAM technology (42). For instance, In-Ceram l, first was described by Sadoun and Degrange, has been shown to have the acceptable flexural strength and clinical performance (43). However, the manufacture of conventional In-Ceram restoration takes up to 14 hours. A milling copings from presintered alumina or zirconia blocks within a 20 minutes period and reducing the glass infiltration time from 4 hours to 40 minutes, CEREC inLab decreases fabrication time by 90% (44).

Zirconia is strong enough and has high biocompatibility (45). Fully sintered zirconia materials can be difficult to mill, taking 3 hours for a single unit. Compared with fully sintered zirconia, milling restorations from pre-sintered or partially sintered solid blocks is easier and less time consuming, creates less tool loading and wear, and provides higher precision (46).

The dimensional change of zirconia material creates compressive stresses that reduce crack propagation. This phenomenon, called “transformation toughening”, actively opposes cracking and gives zirconia its reputation as the “smart ceramic”(47). The quality of transformation toughness and its effect on other properties is unknown. Zirconia copings are laminated with low fusing porcelain to provide esthetics and to reduce wear of the opposing dentition. If the abutment lacks adequate reduction, the restoration may look opaque. Because they normally are not etchable or bondable, abutments require good retention and resistance form. Alumina and zirconia restorations may be cemented with either conventional methods or adhesive bonding techniques (48). Conventional conditioning needed by leucite ceramics, such as hydrofluoric acid-etch, is not required. Microetching with Al2O3 particles on cementation surfaces removes contamination and promotes retention of pure aluminium oxide ceramics (49).

 

 

 

Table 3. Common Restorative Materials for Dental CAD/CAM Systems (37)

Restorative material

CAD/CAM system

Indications

Cementation

Dicor MCG

Cerec

Inlay, onlay veneer

Adhesive(dual-cured)

Vita Mark II

Cerec

Inlay,onlay veneer,anterior crown

Adhesive(dual-cured)

Pro CAD

Cerec

Inlay,onlay veneer,anterior crown

Adhesive(dual-cured)

In-Ceram Spinell

Cerec 3D, Cerec inLab

Anterior crown

Adhesive(self-cured),conventional

In-Ceram Alumina

Cerec 3D, Cerec inLab, DCS Precident

Crown and anterior bridge

Adhesive(self-cured),conventional

In-Ceram Zirconia

Cerec 3D Cerec inLab, DCS Precident

Crown and bridge

Adhesive(self-cured),conventional

Alumina

Procera

Crown and bridge

Adhesive(self-cured),conventional

Partially sintered Zir-conia

DCS Precident, Lava, Procera,Everest, Cercon

Crown and bridge

Adhesive(self-cured),conventional

Fully sintered Zirconia

DCS Precident, Everest

Crown and bridge

Adhesive(self-cured),conventional

 

 

 

 

 


Marginal integrity of CAD/CAM system

A principle concern surrounding CAD/CAM technology is the accuracy of fit of the ceramic crowns fabricated using CEREC system (50). A wide range of variables can affect the marginal accuracy of CAD/CAM restorations such as the scanning process, software design, milling and shrinkage following the final firing of the restoration (51).

Holmes et al. introduced classifications for the marginal gap (52). They measured “misfit” as internal gap, marginal gap, vertical marginal discrepancy, horizontal marginal discrepancy, overextended margin, underextended margin, absolute marginal discrepancy and seating discrepancy (52). According to their classification “the perpendicular measurement from the internal surface of the casting to the axial wall of the preparation is called the “internal gap”, and the same measurement at the margin is called the “marginal gap”. “Absolute marginal discrepancy “was defined as the angular combination of horizontal and vertical discrepancies and represents the total misfit of the restoration (52).

One of the most important criteria in evaluating fixed restorations is marginal integrity. There are controversies about the acceptable marginal integrity, certain studies have evaluated that a marginal fit
 ≤100 microns is more acceptable (53), others consider a fit ≤75 microns clinically acceptable (54). Another study has been reported that the marginal discrepancies larger than 100μm resulted in extensive loss of the luting agent (55).

A study reported that the marginal fit of CEREC 3 CAD/CAM all-ceramic crowns changed when the setting of cement space was altered from 10 µm to 30-50 µm. The marginal fit of the crowns with the cement space setting of 30-50 µm created a marginal gap range of 53-67 µm. When a cement space setting of 10 µm was used marginal gap range of 95-108 µm was observed (56).

In addition, a study reported the possibility of wear that is resulting from contact of food particles with cement when gap dimension exceeded 100μm (57). McLean and Von Fraunhofer (58) proposed that an acceptable marginal discrepancy for full coverage restorations should be less than 120μm. A study  suggested  a  clinical  goal  of  25-40μm  for the marginal adaptation of cemented restorations (59). However, most clinicians agree that the marginal gap should be no greater than 50-100μm (60, 61).

In general, research has shown that CAD/CAM crowns fabricated via the CEREC 3 and later sophisticated systems demonstrated better marginal fit compared to CEREC 1 and CEREC 2 CAD/CAM generations (62, 63).

 

Advantages and disadvantages of CAD/CAM technology

The use of CAD/CAM technology for dental restorations has numerous advantages over traditional techniques. These advantages include speed, ease of use, and quality. Digital scans have the potential to be faster and easier than conventional impressions because casts, wax-ups, investing, casting, and firing are eliminated (64).

Having a milling machine on site means that patients can receive their permanent restoration on the same day they come in, without making a second appointment. Patients no longer need to have provisional restorations, which take time to fabricate and fit. If anesthetics are needed, they only need to be administered once (64). The quality of CAD/CAM restorations is extremely high because measurements and fabrication are extremely precise (65). Perhaps this difference in the finished product should not be surprising, given the wide variation in quality of traditional impressions. Traditional impressions suffer from problems, such as bubbles and tears in the impression material, cords or other debris embedded in the impression material, and missing teeth (66).

CAD/CAM restorations have a natural appearance because the ceramic blocks have a translucent quality that emulates enamel, and they are available in a wide range of shades (64). Ceramic wears well in the mouth, even when used for posterior teeth; because it is no more abrasive than conventional and hybrid posterior composite resins, it causes minimal wear to the opposing teeth (64).

The quality is consistent due to the prefabricated ceramic blocks which are free from internal defects, and the computer program is designed to produce shapes that will stand up to wear (67).

Savings in time and labor have the potential to reduce costs, and the promise of faster, high-quality restorations should appeal to patients (67). Patients are satisfied with digital technology as they are far from gag-inducing impressions. Another benefit is that all the scans can be stored on the computer whereas standard stone models take up space and can chip or break if stored improperly (68).

The digital systems are not free from drawbacks. The initial cost of the equipment and software is high, and the practitioner needs to spend time and money on training (64). Dentists without a large enough volume of restorations will have a difficult time making their investment pay off.

Just as with conventional impressions, in taking an optical scan, the dentist requires to achieve an accurate recording of the tooth to obtain a precise restoration (67). The scan needs to emphasize the finish line and duplicate the surrounding and occlusive teeth. Digital scanning requires the similar type of soft-tissue management, retraction, moisture control, and hemostasis that is extremely important for conventional impressions (67).

Digital impression systems may not save time as they are currently used because of the need for multiple steps. For example, dentists who use certain scanners must first send the images for a cleanup process, which is followed by setting of the margins by a dental technician. The images then sent to the clinician’s dental laboratory for checking. Then a completed models and dies are then sent to the clinician’s dental laboratory for fabrication process (69).

The absence of glass-ceramics in a disc form is a deficiency. Once it becomes available in disc form, the pressing technique will most likely vanish. In addition, additive technology is limited to polymeric and metallic materials and thus far does not include ceramics in dentistry. One more limitation is the limited full arch accuracy of digital impressions as compared with conventional impressions (70).

It has been noted that zirconia frameworks on teeth requiring longer curved frameworks are subjected to a greater sintering distortion than the shorter straight frameworks, which may potentially affect fit and adaptation. The zirconia frameworks exhibit accurate fit for partial arch prosthesis only (71).

 

Future implications of CAD/CAM technology

In the future, ultrasound impressions will be implemented using ultrasonic waves, which have the capability to penetrate the gingiva non-invasively without retraction cords and not be affected by saliva, sulcular fluid, and blood. This will lead to decisive advancements, as detailed cleaning and drying of the oral cavity and associated tooth structure will become unnecessary, as well as reducing treatment time and increasing patient comfort compared with optical impressions (72). 

 

Conclusion

There are no doubts that treatment technologies and materials in dentistry have progressively advanced over the past 50 years, especially in the field of restorative dentistry and prosthodontics. CAD/CAM systems have progressed very rapidly in the past 25 years, where a variety of systems has been launched into the market. It can be used for multiple purposes in dentistry. It is predicted that CAD/CAM will undergo further development in the near future decades.

The evolution of developed versions will bring better quality, excellent ability and increase work procedure friendliness. Materials will be available with high mechanical and physical properties such as better esthetic, marginal integrity, wear resistance, and high strength which permit remaining for a long period in the oral environment. Additionally, dental CAD/CAM may also be available in educational settings and as training tools for daily dental practice, with explanatory materials for patients, diagnostic materials, and for simulations of surgical procedures.

  1. Mantri S, Bhasin S. CAD/CAM in dental restorations: an overview. Ann Essences Dent 2010; II(3): 123-8.
  2. Strub JR, Rekow ED, Witkowski S. Computer-aided design and fabrication of dental restorations - Current systems and future possibilities. J Am Dent Assoc 2006; 137(9): 1289-96.
  3. Miyazaki T, Hotta Y, Kuni J, Kuriyama Sat, Y. A review of dental CAD/CAM: current status and future perspectives from 20 years of experience. Dent Mater J 2008; 28(1): 44-56.
  4. Poticny DJ, Klim J. CAD/CAM in-office technology Innovations after 25 years for predictable, esthetic outcomes. J Am Dent Assoc 2010; 141: 5S-9S.
  5. Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J 2008; 204(9): 505-11.
  6. Mehl A, Hickel R. Current State of Development and Perspectives of Machine-based Production Methods for Dental Restorations. Int J Comput Dent 2009; 2: 9-35.
  7. Liu P-R. A panorama of dental CAD/CAM restorative systems. Compend Contin Educ Dent (Jamesburg, NJ : 1995) 2005; 26(7): 507-12.
  8. Mormann WH, Brandestini M, Lutz F. The Cerec system: computer-assisted preparation of direct ceramic inlays in 1 setting. Die Quintessenz 1987; 38(3): 457-70.
  9. Miyazaki T, Hotta Y. CAD/CAM systems available for the fabrication of crown and bridge restorations. Aust Dent J 2011; 56: 97-106.
  10. Yau H, Hsu C, Peng HaPC. Computer-aided Framework Design for Digital Dentistry. Comput Aid Des Applic 2008; 5(5).
  11. Wildgoose DG, Johnson A, Winstanley RB. Glass/ceramic/refractory techniques, their development and introduction into dentistry: A historical literature review. J Prosthet Dent 2004; 91(2): 136-43.
  12. Roma Goswami GAaAP. CAD/CAM in Restorative Dentistry: A Review. Br Biomed Bull 2014; 2(4): 591-7.
  13. Mehl A, Hickel R. Current state of development and perspectives of machine-based production methods for dental restorations. Int J Comput Dent 1999; 2(1): 9-35.
  14. Young JM, Altschuler BR. LASER HOLOGRAPHY IN DENTISTRY. J Prosthet Dent 1977; 38(2): 216-25.
  15. Rekow ED. CAD/CAM in dentistry: a historical perspective and view of the future. J Can Dent Assoc 1992; 58(4): 287-8.
  16. Hodd JA. CAD/CAM dentistry for today's on-the-go military. US Army Med Dep J 2011: 26-37.
  17. Fasbinder DJ. Clinical performance of chairside CAD/CAM restorations. J Am Dent Assoc 2006; 137: 22S-31S.
  18. Giordano R. Materials for chairside CAD/CAM-produced restorations J Am Dent Assoc. 2006; 137: 14S-21S.
  19. Moermann WH. The evolution of the CEREC system. J Am Dent Assoc 2006; 137: 7S-13S.
  20. Jeynakiewicz N, Martin N. CAD/CAM in Restorative Dentistry-The Cerec Method1993.
  21. Culp L, Touchstone A. CAD/CAM Dentistry: A New Forum for Dentist-Technician Teamwork. Inside Dent 2006; 2(7).
  22. Freedman M, Quinn F, O'Sullivan M. Single unit CAD/CAM restorations: a literature review. J Irish Dent Assoc 2007; 53(1): 38-45.
  23. Touchstone A, Nieting T, Ulmer N. Digital transition The collaboration between dentists and laboratory technicians on CAD/CAM restorations. J Am Dent Assoc 2010; 141: 15S-9S.
  24. Benington PCM, Khambay BS, Ayoub AF. An overview of three-dimensional imaging in dentistry. Dent update 2010; 37(8): 494-passim.
  25. Galhano GA, Pellizzer EP, Mazaro JV. Optical impression systems for CAD-CAM restorations. J Craniofac Surg 2012; 23(6): e575-9.
  26. Tapie L, Lebon N, Mawussi B, Fron Chabouis H, Duret F, Attal JP. Understanding dental CAD/CAM for restorations--the digital workflow from a mechanical engineering viewpoint. Int J Comput Dent 2015; 18(1): 21-44.
  27. Zimmermann M, Mehl A, Mormann WH, Reich S. Intraoral scanning systems - a current overview. Int J Comput Dent 2015; 18(2): 101-29.
  28. Pollington S, Van Noort R. An Update of ceremics in dentistry. Int J Clin Dent 2009; 2(4): 283-307.
  29. Akbar JH, Petrie CS, Walker MP, Williams K, Eick JD. Marginal adaptation of Cerec 3 CAD/CAM composite crowns using two different finish line preparation designs. J Prosthodont : official journal of the American College of Prosthodontists 2006; 15(3): 155-63.
  30. Fasbinder DJ. The CEREC system 25 years of chairside CAD/CAM dentistry. J Am Dent Assoc 2010; 141: 3S-4S.
  31. Mormann W. The right step to Cerec 3. Int J Comput Dent 2000; 3(1): 3-4.
  32. Fasbinder DJ. Restorative material options for CAD/CAM restorations. Compend Contin Educ Dent (Jamesburg, NJ : 1995) 2002; 23(10): 911-20.
  33. Dunn M. Biogeneric and user-friendly: the Cerec 3D software upgrade V3.00. Int J Comput Dent 2007; 10(1): 109-17.
  34. Kim JH, Kim KB, Kim SH, Kim WC, Kim HY, Kim JH. Quantitative evaluation of common errors in digital impression obtained by using an LED blue light in-office CAD/CAM system. Quintessence int (Berlin, Germany : 1985) 2015; 46(5): 401-7.
  35. Marco Brandestini, Moermann WH: Inventor. Method and apparatus for the three dimensional registration and display of prepared teeth. US patent No.4, 837, 732. 1989.
  36. Santos MJ, Costa MD, Rubo JH, Pegoraro LF, Santos GC, Jr. Current all-ceramic systems in dentistry: a review. Compend Contin Educ Dent (Jamesburg, NJ :1995) 2015; 36(1) :31-7; quiz
     8, 40.
  37. Fasbinder DJ. Materials for Chairside CAD/CAM Restorations. Compend Contin Educ Dent 2010; 31(9).
  38. Li RWK, Chow TW, Matinlinna JP. Ceramic dental biomaterials and CAD/CAM technology: State of the art. J Prosthodont Res 2014; 58(4): 208-16.
  39. Posselt A, Kerschbaum T. Longevity of 2328 chairside Cerec inlays and onlays. Int J  Comput Dent 2003; 6(3): 231-48.
  40. Wiedhahn K, Kerschbaum T, Fasbinder DF. Clinical long-term results with 617 Cerec veneers: a nine-year report. Int J Comput Dent 2005; 8(3): 233-46.
  41. Mormann WH, Bindl A. The new creativity in ceramic restorations: dental CAD-CIM. Quintessence Int (Berlin, Germany : 1985) 1996; 27(12): 821-8.
  42. PrÖBster L. Four year clinical study of glass-infiltrated, sintered alumina crowns. J Oral Rehabil 1996; 23(3): 147-51.
  43. Selz CF, Strub JR, Vach K, Guess PC. Long-term performance of posterior InCeram Alumina crowns cemented with different luting agents: a prospective, randomized clinical split-mouth study over 5 years. Clin Oral Investig 2014; 18(6):
    1695-703.
  44. Gozdowski S, Reich S. A comparison of the fabrication times of all-ceramic partial crowns: Cerec 3D vs IPS Empress. Int J Comput Dent 2009; 12(3): 279-89.
  45. Arnetzl G, Arnetzl GV. Hybrid materials offer new perspectives. Int J Comput Dent 2015; 18(2):
    177-86.
  46. Silva Meza R. Radiographic assessment of congenitally missing teeth in orthodontic patients. Int J Paediatr Dent 2003; 13(2): 112-6.
  47. Badami V, Ahuja B. Biosmart materials: breaking new ground in dentistry. Sci World J 2014; 2014: 986912.
  48. Della Bona A, Donassollo TA, Demarco FF, Barrett AA, Mecholsky JJ, Jr. Characterization and surface treatment effects on topography of a glass-infiltrated alumina/zirconia-reinforced ceramic. Dent Mater : official publication of the Academy of Dental Materials 2007; 23(6): 769-75.
  49. Amaral M, Belli R, Cesar PF, Valandro LF, Petschelt A, Lohbauer U. The potential of novel primers and universal adhesives to bond to zirconia. Journal of dentistry 2014; 42(1): 90-8.
  50. Reiss B. Long-term clinical performance of CEREC restorations and the variables affecting treatment success. Compend Contin Educ Dent (Jamesburg, NJ :1995) 2001; 22(6 Suppl): 14-8.
  51. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems. Eur J Oral Sci 2005; 113(2): 174-9.
  52. Holmes JR, Bayne SC, Holland GA, Sulik WD. Considerations in measurement of marginal fit. J Prosthet Dent 1989; 62(4): 405-8.
  53. Reich S, Gozdowski S, Trentzsch L, Frankenberger R, Lohbauer U. Marginal fit of heat-pressed vs. CAD/CAM processed all-ceramic onlays using a milling unit prototype. Oper Dent 2008; 33(6):
    644-50.
  54. Council adopts American Dental Association Specification No. 8 (dental zinc phosphate cement) and 11 (agar impression material). Council on Dental Materials and Devices. J Am Dent Assoc (1939) 1967; 74(7): 1565-73.
  55. Leinfelder KF, Isenberg BP, Essig ME. A new method for generating ceramic restorations: a CAD-CAM system. J Am Dent Assoc (1939) 1989; 118(6): 703-7.
  56. Nakamura T, Dei N, Kojima T, Wakabayashi K. Marginal and internal fit of Cerec 3 CAD/CAM all-ceramic crowns. Int J Prosthodont 2003; 16(3): 244-8.
  57. O'Neal SJ, Miracle RL, Leinfelder KF. Evaluating interfacial gaps for esthetic inlays. J Am Dent Assoc (1939) 1993; 124(12): 48-54.
  58. McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J 1971; 131(3): 107-11.
  59. Christensen GJ. Marginal fit of gold inlay castings. J Prosthet Dent 1966; 16(2): 297-305.
  60. Zarrati S, Mahboub F. Marginal adaptation of indirect composite, glass-ceramic inlays and direct composite: an in vitro evaluation. J Dent (Tehran, Iran) 2010; 7(2): 77-83.
  61. Chaffee NR, Lund PS, Aquilino SA, Diaz-Arnold AM. Marginal adaptation of porcelain margins in metal ceramic restorations. Int J Prosthodont 1991; 4(6): 508-16.
  62. Ellingsen LA, Fasbinder D.J. An in vitro evaluation of CAD/CAM ceramic crowns. J Dent Restor 2002; 81(331).
  63. Kelvin Khng KY, Ettinger RL, Armstrong SR, Lindquist T, Gratton DG, Qian F. In vitro evaluation of the marginal integrity of CAD/CAM interim crowns. J Prosthet Dent  2016; 115(5):
    617-23.
  64. Mormann WH, Brandestini M, Lutz F, Barbakow F. Chairside computer-aided direct ceramic inlays. Quintessence int (Berlin, Germany : 1985) 1989; 20(5): 329-39.
  65. Miyazaki T, Hotta Y. CAD/CAM systems available for the fabrication of crown and bridge restorations. Aust Dent J 2011;56 Suppl 1:97-106.
  66. 66.  Christensen GJ. The state of fixed prosthodontic impressions: room for improvement. J Am Dent Assoc (1939) 2005; 136(3): 343-6.
  67. Silva LHD, Lima E, Miranda RBP, Favero SS, Lohbauer U, Cesar PF. Dental ceramics: a review of new materials and processing methods. Braz Oral Res 2017; 31(suppl 1): e58.
  68. Birnbaum N AH, Stevens C. 3D digital scanners: a high-tech approach to more accurate dental impressions. Inside Dent 2009; 5(4).
  69. Henkel GL. A comparison of fixed prostheses generated from conventional vs digitally scanned dental impressions. Compend Contin Educ Dent (Jamesburg, NJ :1995). 2007; 28(8): 422-4, 6-8,
    30-1.
  70. Ender A, Mehl A. In-vitro evaluation of the accuracy of conventional and digital methods of obtaining full-arch dental impressions. Quintessence Int (Berlin, Germany :1985) 2015; 46(1): 9-17.
  71. Abduo J. Fit of CAD/CAM Implant Frameworks: A Comprehensive Review. J Oral Implant 2014; 40(6): 758-66.
  72. Vollborn T, Habor D, Pekam FC, Heger S, Marotti J, Reich S, et al. Soft tissue-preserving computer-aided impression: a novel concept using ultrasonic 3D-scanning. Int J Comput Dent 2014; 17(4): 277-96.