CAD/CAM dentistry is a field of dentistry and prosthodontics using CAD/CAM (computer-aided-design and computer-aided-manufacturing) to improve the design and creation of dental restorations, especially dental prostheses, including crowns, crown lays, veneers, inlays and onlays, fixed dental prostheses (bridges), dental implant supported restorations, dentures (removable or fixed), and orthodontic appliances. CAD/CAM technology allows the delivery of a well-fitting, aesthetic, and a durable prostheses for the patient. CAD/CAM complements earlier technologies used for these purposes by any combination of increasing the speed of design and creation; increasing the convenience or simplicity of the design, creation, and insertion processes; and making possible restorations and appliances that otherwise would have been infeasible. Other goals include reducing unit cost and making affordable restorations and appliances that otherwise would have been prohibitively expensive. However, to date, chairside CAD/CAM often involves extra time on the part of the dentist, and the fee is often at least two times higher than for conventional restorative treatments using lab services.
Like other CAD/CAM fields, CAD/CAM dentistry uses subtractive processes (such as CNC milling) and additive processes (such as 3D printing) to produce physical instances from 3D models.
Some mentions of "CAD/CAM" and "milling technology" in dental technology have loosely treated those two terms as if they were interchangeable, largely because before the 2010s, most CAD/CAM-directed manufacturing was CNC cutting, not additive manufacturing, so CAD/CAM and CNC were commonly used together; but whereas this loose/imprecise usage was once somewhat close to accurate, it no longer is, as the term "CAD/CAM" does not specify the method of production except that whatever method is used takes input from CAD/CAM, and today additive and subtractive methods are both widely used.
Application of CAD/CAM in dentistry Computer-aided design (CAD) and computer-aided manufacture (CAM) is a process where non-digital data is captured, converted into a digital format, edited as necessary, and subsequently converted back into a physical form with the exact dimensions and materials specified during the digital design process, usually by either 3D printing or milling. This set of stages is known as a "digital workflow".
CAD/CAM may be used to provide a machine-led means of fabricating dental prostheses that are used to restore or replace teeth. This is an alternative to the traditional process of prosthesis fabrication using physical techniques, in which the dentist makes an impression of the site that is to be restored. This is then transported to the laboratory where a study model is made. On that model, an imitation of the final design is made using wax – known as a wax up – which represents the size and shape of the finished dental prosthesis. The wax is then encased in an investment mold, burned out and replaced with the desired material as part of lost wax casting. CAD/CAM makes such procedures unnecessary for the impression is recorded digitally and the manufacture of the appliance is accompanied by additive (3D printing) or subtractive (milling) means.
Examples of dental prostheses that can be manufactured using this system include:
Study models Orthodontic devices Cuspal coverage restorations Fixed dental prostheses Veneers Removable denture frameworks Implant planning and fabrication
History
Although CAD/CAM dentistry was used in the mid-1980s, early efforts were considered a cumbersome novelty, requiring an inordinate amount of time to produce a viable product. This inefficiency prevented its use within dental offices and limited it to labside use (that is, used within dental laboratories). As adjunctive techniques, software, and materials improved, the chairside use of CAD/CAM (use within dental offices/surgeries) increased. For example, the commercialization of Cerec by Sirona made CAD/CAM available to dentists who formerly would not have had avenues for using it.
The first CAD/CAM system used in dentistry was produced in the 1970s by Professor François Duret and colleagues. The process contains a number of steps. Firstly, an optical impression of the intraoral abutment is obtained by scanning with an intra-oral digitizer. The digitized information is transferred to the monitor where a 3D graphic design is produced. The restoration can then be designed on the computer. The final restoration is then milled from a block. Professor Duret and colleagues subsequently developed the 'sopha system' however this was not widely used, perhaps lacking the accuracy, materials and computer capabilities required in dentistry. The second generation of CADCAM attempted to develop this system further, but struggled to obtain occlusal morphology using an intra oral scanner, so prepared a stone model first before digitizing the model.
Development of a various digitizers followed: a laser beam with a position sensitive detector sensor, a contact probe and a laser with a charged coupled device camera. Due to development of more sophisticated CAD/CAM systems both metal and ceramic restorations could be produced.
Mormann and colleagues later developed a CADCAM system named CEREC, which they used to produce a type of dental restoration called an inlay. The inlay preparation is scanned using an intra-oral camera. A compact machine used chairside allowed design of the restoration from a ceramic block. The major advantage of this system was the chair side approach allowing same-day restorations. However, this technique was limited in that it couldn't be used for contouring or occlusal patterns. The CEREC system is used widely across the world, and studies have shown long term clinical success.
The Procera system was developed by Anderson and colleagues. They used CADCAM to develop composite veneers. The Procera system later developed as a processing center connected to satellite digitizers worldwide to produce all ceramic frameworks. This system is used around the world today.
Difference from conventional restoration
Chairside CAD/CAM restoration typically creates and lutes(bonds) the prosthesis the same day. Conventional prostheses, such as crowns, have temporaries placed for one to several weeks while a dental laboratory or in-house dental lab produces the restoration. The patient returns later to have the temporaries removed and the laboratory-made crown cemented or bonded in place. An in-house CAD/CAM system enables the dentist to create a finished inlay in as little as one hour. CAD/CAM systems use an optical camera to take a virtual impression by creating a 3D image which is imported into a software program and results in a computer-generated cast on which the restoration is designed.
Bonded veneer CAD/CAM restorations are more conservative in their preparation of the tooth. As bonding is more effective on tooth enamel than the underlying dentin, care is taken not to remove the enamel layer. Though one-day service is a benefit that is typically claimed by dentists offering chairside CAD/CAM services, the dentist's time is commonly doubled and the fee is therefore doubled.
Process All CAD/CAM systems consist of a computer aided design (CAD) and computer aided manufacture (CAM) stage and the key stages can broadly be summarized as the following:
Optical/contrast scanning that captures the intraoral or extraoral condition of the patient. Use of software that can turn the captured images into a digital model to upon which a dental prosthesis can be designed and prepared for fabrication. Instruction to devices that can facilitate the conversion of the design into a product by way of 3D printing or milling depending on the CAD/CAM system used.
For a single unit prosthesis, after decayed or broken areas of the tooth are corrected by the dentist, an optical impression is made of the prepared tooth and the surrounding teeth. These images are then turned into a digital model by proprietary software within which the prosthesis is created virtually. The software sends this data to a milling machine where the prosthesis is milled. Stains and glazes can be added to the surfaces of the milled ceramic crown or bridge to correct the otherwise monochromatic appearance of the restoration. The restoration is then adjusted in the patient's mouth and luted or bonded in place.
Integrating optical scan data with cone beam computed tomography datasets within implantology software also enables surgical teams to digitally plan implant placement and fabricate a surgical guide for precise implementation of that plan. Combining CAD/CAM software with 3D images from a 3D imaging system means greater safety and security from any kind of intraoperative mistakes.
Computer-aided design (CAD) To design and manufacture a dental prosthesis, the physical space which it will replace within the mouth has to be converted into a digital format. To do this, a digital impression must be taken. This will convert the space into a digital image which must then be converted into a file extension that can be read by the CAD software system being used.
Once in a digital form, the structures within the mouth will be displayed as a 3D image. Using CAD software, the size and shape of the restoration can be virtually altered, thus replacing the wax up stage present in the traditional approach.
Digital impressions Digital impressions are a means of recording the shape of a patient's dental structures by using scanners. In CAD/CAM's infancy, desktop scanners were used which digitized study models or Dental impressions - indirect representations of the patient's dentition. These devices are also known as extra oral scanners and can be contact or non-contact.
Contact scanners use stylus profilometers that are placed against and run along the contours of an object. The contact of the stylus against the object is represented digitally as a set of co-ordinates (point cloud), which is analyzed by an onboard mathematical algorithm to build up a 3D image of the object (mesh).
Non-contact scanners capture the shape of dental structures by using optics, such as light-emitting diodes. Light is emitted from the scanner which hits the object and then reflects into an onboard sensor, usually a charge couple device (CCD) or a position sensing detector (PSD). These reflections allow the scanner to build up a 3D image of the object as with contact scanners Extraoral non-contact scanners can obtain this information by different means, namely: structured light, laser light and confocal microscopy. Contact scanners are more accurate than non-contact scanners but are rarely used anymore because they are slow and their imaging is unnecessarily detailed, ten times what is required for the success of a dental prosthesis.
Intra-oral scanners are a form of non-contact scanners that have grown in popularity due to their ability to digitize a patient's dentition directly in the mouth, avoiding the need for either a physical impression or a plaster study model, as is the case with extraoral scanners. This allows the fabrication of dental prostheses to be a completely digital process from the very first stage. Older scanners require a contrast powder to be placed on all the structures which were to be scanned whereas newer products do not require such a step.
Intra-oral scanners interpret reflected light to produce a 3D image representing the patient's teeth, using systems including: Confocal laser scanner microscopy Triangulation Optical coherent tomography Accordion fringe interferometry Active wavefront sampling