Computer-Aided Design/Computer-Aided Manufacturing In Dentistry – Future Is Present
Computer-Aided Design (CAD) is the use of computer systems to aid in the creation, modification, analysis, or optimization of a design. CAD is an important industrial art extensively used in many application, including automotive, shipbuilding, aerospace industries, dentistry, etc. It helps to increase productivity, quality of the design, improve communication and create database for manufacturing. It can be created in two-dimensional (2D) and/or three-dimensional (3D) depending on the user requirement. Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) are usually integrated as it allows the user to create the model using CAD and send for manufacturing using CAM software to generate the database. The following are the steps of a typical computer aided design process.
- Conceptual system design – starting with a rough model of the system without considering a dimension control. The main purpose of it was to have a better visualization of the product.
- Freezing of concept – By reviewing the conceptual design is being frozen, thus the system level assembly is being finalized.
- Detail component design – The detail CAD geometry of each individual components is then created with appropriate dimension and tolerance.
Product Data Management (PDM) - It is a database for CAD geometry and the related documents. In short, PDM helps systematic access and revisions of CAD data.
Computer Aided Engineering (CAE) - The detailed CAD geometry will be used as input for Computer Aided Engineering or Finite Element Analysis (FEA) to know whether the geometry will sustain the loading condition or not, if not then required modification is done for the CAD geometry and so on.
Computer Aided Manufacturing – After the CAD geometry passed its FEA, it will be converted to NC codes and input to CAM. Those NC codes are the program which fed to the CNC machines for manufacturing the components/parts. Below are the advantages and disadvantage of CAD/CAM:
In the mid 80’s, Computer-Aided Design and Computer-Aided Manufacturing technologies were adopted in the dentistry and prosthodontics to improve the design and creation of dental restorations such as inlays and onlays, bridges, crowns, veneers, and dental implant restorations. The output of a CAD process typically is 2D and/or 3D geometry like curves, surfaces, and solids. However, often the CAD geometry also contains data such as material properties, dimensions, tolerance and manufacturing process specific information. The CAD/CAM system basically consisted of three functional components. The first component will be the scanner which was used to scan an object and transform geometry into digital data which can be processed using a computer. The second component will be CAD modeling software. The software will convert the processed data from the actual dental model into a virtual model. The third components will be CAM production. The production will then use the data to manufacture the desired product. The scanner is an imaging device that collects distance point measurements from a real-world object and translates them into a virtual 3-D model. There is two type of scanner used in dentistry namely Optical scanner and Mechanical scanner.
Optical scanner – This technique is using lighter rays, in the form of lines to project on the preparation (line hatched area). The rays oscillate rapidly across the object in order to obtain three-dimensional shape within a short period.
Mechanical scanner – This technique is also known as a coordinate measuring machine (CMM). It uses a probe (ruby ball) to contact on the physical part to obtain the reading. This scanning provides high accuracy. However, the disadvantages include complicated mechanics, costly and longer processing time. However, there some factors needed to be considered while performing the scanning.
During scanning, all required details for the restoration should be captured entirely by the scan and visualize. 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. Therefore, a slight movement of the patient during scanning can cause deviation to the data produced and may result to restoration misfit. Computer-Aided Design software is used to convert scanned data into a 3D model with STereoLithography (STL) format. There are several CAD software available in the market used commercially for designing virtual 3D dental restoration such as Align Technology, Danaher, DENTSPLY Sirona, Planmeca, Zimmer Biomet, etc. The software program is proprietary to the CAD/CAM system and it cannot be interchangeable among other systems. After the restoration design is complete, the CAD software will then converts the virtual model into a specific set of commands. It will then drive the CAM unit which manufactures the designed restoration.
The Computer-Aided Manufacturing production uses CAM software to convert data obtained from CAD software into the mill sequence. The sequence will be transferred to a milling device to machine the desired product out from a solid block. There are several axis milling device in the market but in dentistry, 4-axis and 5-axis are the most commonly used as it allows to machine complex shape product. There is basically 3 type of CAD/CAM production concept in dentistry namely Chairside/In-office, Laboratory and Production Centre. The detail of each concepts as per below:
Chairside/In-office CAD CAM technique – This concept will have all the functional components of CAD/CAM system located within the dental office which consisted of scanning of tooth preparation and fabricating the restoration in a milling device. A handheld scanner will be used to scan the preparation, entire arch with and without occlusion. The entire process can be done within a single visit and there is no longer the need for impression and temporization.
Laboratory CAD CAM technique – The CAD CAM production will take place completely at the laboratory. The dentist will obtain the patient impression and send it to the laboratory. The master cast will be casted using the impressions sent to the laboratory. The remaining CAD/CAM production steps are carried out completely in the laboratory. This technique will require the patient to visit the dental twice to have the restoration done.
Production centre – Local dental laboratory with satellite scanners send the data sets to the production centre for performing milling of the restoration and the production centre sends to the prosthesis to the responsible laboratory. Therefore, scanning and designing will takes place in the in the dental laboratory while production of the restoration take place in the production centre.
The application for Computer-Aided Design/Computer-Aided Manufacturing in dentistry start with better and multi-layered materials, the dental applications of CAD CAM had expanded tremendously to every field of dentistry. Indirect restoration such as inlays, onlays, single crowns, fixed dental prosthesis, and occlusal splints can be manufactured using CAD/CAM technology. Another convenient application of CAD/CAM includes surgical stents, frameworks, and bars customized zirconia and titanium implant abutments. A few years back, CAD/CAM has also found its applications in removable prosthodontics, maxillofacial prosthodontics using rapid prototyping and orthodontics.
In conclusion, CAD/CAM is part of “today” in dentistry and is processing the future much faster than we think of. It basically helps to improve in various area such as production efficiency, labour issues, cost and provide better service to the patients. Nevertheless, the predictability of the restoration is dependent on good preparation, detailed of the impression obtained and also the well-designed esthetic and functional restoration.
