|Year : 2015 | Volume
| Issue : 2 | Page : 60-64
Computer-aided design/computer-aided manufacturing in dentistry – Future is present
Vidya K Shenoy, M Bharath Prabhu
Department of Prosthodontics, AJ Institute of Dental Sciences, Mangalore, Karnataka, India
|Date of Web Publication||5-Jan-2016|
Vidya K Shenoy
Department of Prosthodontics, AJ Institute of Dental Sciences, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Computer-aided design/computer-aided manufacturing (CAD/CAM) restorations have developed at rapid pace since their introduction offering accuracy and more options. The paradigm shift from traditional techniques to CAD/CAM technology has brought about a revolutionary change in the way the restorations are fabricated. Impression techniques, burnout oven, and casting machines have been replaced by model scanning and CAD/CAM milling machines. Keyboards, monitors, and cursors have replaced Bunsen burners, wax, and carving instrument to fabricate crown and bridge prosthesis. CAD/CAM technology offers automated production, patient comfort, esthetically pleasing and strong restorations and cost-effectiveness to laboratories.
CLINICAL RELEVANCE TO INTERDISCIPLINARY DENTISTRY
- Computer-aided design/computer.aided manufacturing technology is now a viable, predictable, and efficient alternative to traditional methods for fabrication of dental restorations
- It has innumerable clinical applications including fabrication of indirect restorations, occlusal splints, implant prosthodontics, maxillofacial prosthodontics, and orthodontics.
Keywords: Ceramics, computer-aided design/computer-aided manufacturing, milling devices
|How to cite this article:|
Shenoy VK, Prabhu M B. Computer-aided design/computer-aided manufacturing in dentistry – Future is present. J Interdiscip Dentistry 2015;5:60-4
|How to cite this URL:|
Shenoy VK, Prabhu M B. Computer-aided design/computer-aided manufacturing in dentistry – Future is present. J Interdiscip Dentistry [serial online] 2015 [cited 2020 Feb 17];5:60-4. Available from: http://www.jidonline.com/text.asp?2015/5/2/60/173229
| Introduction|| |
The increased demand for all-ceramic restorations in both the anterior and posterior regions has led to evolution of computer-aided design and computer-aided manufacturing (CAD and CAM) technology systems. Pioneered by Mörmann  in the early 1980s, the first CAD/CAM system called Cerec ® System (Sirona Dental systems, Germany) opened the era of CAD/CAM in dentistry. The ever growing CAD/CAM technology was fueled by the evolution of computing power and precise acquisition units and milling machines. Thus, digital systems offer the opportunity to avoid traditional, analog impressions offering patient comfort, and efficient workflow.
| Functional Components of Computer-Aided Design/computer-Aided Manufacturing System|| |
All CAD/CAM systems consist of three components [Figure 1]:,
- Scanner: It captures and transforms geometry into digital data that can be processed by the computer [Figure 2]
- CAD modeling software: Software that processes data and converts the actual dental model into virtual dental model by producing a data set [Figure 3]
- CAM production: A production technology that transforms the data set into the desired product [Figure 4].
|Figure 1: Functional components of Computer-aided design/computer-aided manufacturing|
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It is a data collection tool that measures three-dimensional (3D) jaw and tooth structures and transforms them into digital data sets. It is composed of a high-resolution camera that reads the finest details of the surface to be scanned. There are two different types of scanners available commercially.
- Optical scanners
- Mechanical scanners.
It involves the principle of “triangulation procedure ” for capturing the 3D structures. The scanner takes the image of the cast. White light or laser beam is used as a source of illumination and a digital camera which is represented by the receptor unit registers the reflected patterns. Therefore, the source of light and the receptor unit are in a definite angle to one another and through this angle the computer can calculate a 3D data set from the
image on the receptor unit. For example, Lava™ Scan ST (3M ESPE, USA) KaVo Everest (KaVo Dental Ltd., Germany).
In this technique, scanning is accomplished by reading the master cast mechanically line-by-line by means of a touch probe (ruby ball) around the object, and the 3D structure is measured, e.g., Procera Scanner (Nobel Biocare, Switzerland). This provides a high scanning accuracy. However, drawbacks include complicated mechanics, cost, and long processing times.
Factors to be considered while scanning
During scanning, all required details for the restoration fabrication should be captured by the scan and visualized. Depending on the system, a light and rapid dusting of an opacifier may be required prior to capturing the digital scans. The preparation can be viewed from every angle on the monitor. Slight movement of the patient while scanning would compromise data quality and may lead to restoration misfit.
Computer-aided design software for restoration design
The scanned data is converted into STereoLithography format. Several CAD software programs are available commercially for designing virtual 3D dental restorations. The software program is proprietary to the CAD/CAM system and cannot be interchanged among systems. When the design of the restoration is complete, the CAD software transforms the virtual model into a specific set of commands. These in turn drive the CAM unit which fabricates the designed restoration.
Computer-aided manufacturing production
The data sets from the CAD software are converted into milling sequence using CAM software and finally loaded into the milling device to mill a part out of the stock material [Figure 5]. CAM software may be integrated with CAD software or sometimes a standalone separate programs. The CAM software must be configured with specific information about the mill including the size and shape of the cutting tools, the material being milled, the spindle controller, and the motors that move or rotate the stock and spindle.
|Figure 5: Computer-aided design/computer-aided manufacturing production concepts|
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Milling devices are classified based on the number of milling axes.
This type of milling device moves in the three spatial directions, i.e., X, Y, and Z. They are capable of milling from the top or bottom of the stock material but are unable to mill undercuts, which is adequate for routine crown and bridge work. The advantages of these milling devices are short milling times and simplified control by means of the three axes. For example, inLab (Sirona Dental Systems, Germany), CNC milling machines (vhf, Germany).
This type of milling device moves in the four spatial directions, i.e., X, Y, Z, and the rotatable tension bridge. Mills with four axes can mill undercuts in only one direction. For example, Zeno (Wieland-Imes).
In this milling device, in addition to the three spatial dimensions and the rotatable tension bridge, milling spindle can be rotated (5th axis). Five-axis milling devices can mill undercuts in each direction and are beneficial when milling custom implant abutments that may have undercut areas or for large-span bridges. For example, Everest Engine (KaVo).
There are three basic routines in the milling sequence, i.e., roughing, finishing, and detail. Roughing is the step where bulk material is removed quickly with the largest diameter cutting tool available. Finishing is an intermediate step that removes the material left over from roughing with a smaller tool. In the final milling sequence is done with a smaller cutting tool than the finishing tool.
Manufacturers fabricate the material in a solid block form ready for the milling process. The material must be capable of being milled without damage to the material. Depending on the type of material, dry or wet milling technique can be employed. Certain ceramic materials such as lithium disilicate, feldspathic porcelains, and metals require wet milling whereas zirconia and titanium can be milled dry or wet. In general, wax and acrylic are milled dry. The material must be capable of being milled generally in <20 min with a minimal postmilling processing time for fabrication of chairside CAD/CAM restoration. Furthermore, materials should be esthetically pleasing as milled and able to be customized to the desired shade.
Ceramic blocks (Paradigm MZ 100 [3M ESPE]), feldspathic glass ceramics VITABLOCS® Mark II (VITA, Zahnfabrik, Germany), and high strength ceramics such as lithium disilicate (Ivoclar Vivadent Schaan, Liechtenstein) are most commonly used chairside CAD/CAM restorative materials.
The materials used to fabricate restorations using laboratory CAD/CAM systems include ceramics, metal alloys, composites, titanium, and polyether ether ketone. The materials used for dental CAD/CAM offer benefits such as higher quality, user friendliness, and enhanced esthetics.
Computer-aided design/computer-aided manufacturing production concepts
Depending on the location of the components of the CAD/CAM systems, in dentistry, three different production concepts are available [Figure 5]:
- Chairside/inoffice CAD CAM technique
- Laboratory CAD CAM technique
- Centralized fabrication in a production center.
Chairside/inoffice system computer-aided design/computer-aided manufacturing technique
All functional components of the CAD/CAM system are located in the dental office. The chairside technique involves scanning the tooth preparation and fabricating the restoration in a milling device in the dental office itself. A handheld scanner is used to scan the preparation, entire arch with and without occlusion, e.g., Cerec ® System (Sirona Dental Systems, Germany). It is a single visit procedure eliminating the need for impression and temporization.
Laboratory computer-aided design/computer-aided manufacturing technique
The dentist sends the impression to the laboratory where a master cast is fabricated first. The remaining CAD/CAM production steps are carried out completely in the laboratory.
This technique requires two visits. During the first visit, tooth preparation and scanning is accomplished.
There are two options for scanning the preparation:
- The clinician can scan the preparation chairside and then send the scan to the laboratory by digital transmission for designing and milling the restoration. This eliminates the conventional impression procedure
- The clinician sends the impression to the laboratory where a master cast is fabricated first. The model is scanned with assistance of a scanner.
The CAD/CAM process then takes place in the laboratory equipped with CAD/CAM unit.
Milling centers or production set-up
Local dental laboratories with satellite scanners send the data sets to the production center for the milling the restorations and the production center sends the prosthesis to the responsible laboratory. Thus, scanning and designing take place in the dental laboratory while the production takes place in the center. As a result, the configuration of the prosthesis remains in the hands of the dental technician.
Why use dental computer-aided design/computer-aided manufacturing systems?
- Chairside CAD/CAM technique eliminates a second visit for the patient
- They have been found to have good longevity and clinically acceptable accuracy of fit because of standardized manufacturing process ,
- Clinician can visualize the preparation multiple times and retake the scan if necessary
- Digital impression eliminates discomfort associated with traditional impression procedure
- Cost-effectiveness for the dental laboratories.
Applications for computer-aided design/computer-aided manufacturing in dentistry
With the advent of better and multilayered materials, the dental applications of CAD CAM have expanded tremendously to every field of dentistry. Indirect restorations such as inlays, onlays, single crowns, fixed dental prosthesis, and occlusal splints can be fabricated using CAD/CAM technology. Another convenient application of CAD/CAM includes surgical stents, frameworks, and bars customized zirconia and titanium implant abutments, [Figure 6]. Recently,
CAD/CAM has also found its applications in removable prosthodontics, maxillofacial prosthodontics using rapid prototyping, and orthodontics.
| Conclusion|| |
CAD/CAM is part of “today ” in dentistry and is defining the future faster than we think. It helps to improve production efficiency, labor issues and deliver better service to the patients. However, the predictability of the restoration depends on a good preparation, detailed impression, and a well-designed esthetic and functional restoration.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]