Advantages and disadvantages of CAD / CAM in dentistry

Traditionally, veneers, crowns, implant abutments, bridges, inlays/onlays, dentures, and other dental restorations required several office visits, and a long turn-around period of over two weeks before finishing your treatment. Today, advancements in dental technology have made many dental techniques and processes faster, more accurate, and more efficient than ever before. CAD/CAM or computer-aided design and computer-aided manufacturing allow dentists to design and fabricate a variety of cosmetic and restorative procedures in a single visit, while you wait in the office.

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Office-based CAD/CAM Devices

The dental CAD/CAM systems used in offices typically comprise a handheld scanner, a milling machine, and a cart that holds a computer and monitor.

When the scanner head is positioned intraorally above the tooth preparation, it produces 2-D or 3-D data in the form of images that are displayed on the monitor. The dentist can then perform design work on the monitor, before relaying milling instructions to a computer-assisted processing machine.

Restorations are typically milled from porcelain prefabricated blocks that include leucite, lithium disilicate, feldspathic, and composite block materials. The restoration is then assessed, approved for installation, and polished before placement using normal bonding methods.

Types of office-based devices

Currently, dental offices can take digital impression using four devices:

CEREC AC

E4D Dentist
iTero
Lava COS

By taking dental impressions in-house, dental professionals can avoid the laborious tasks of choosing trays, mixing ingredients and waiting for them to set, cleaning up the mess from the impressions, sanitizing the impressions, and sending the impressions to a lab.

The iTero and Lava COS devices are solely used for image acquisition, in contrast to the CEREC and E4D devices, which can be used for both in-office design and milling. It is the latter 2 that make same-day dental restorations possible.

The CAD/CAM Process

CAD/CAM technology is available to dentists and qualified technicians in dental labs, giving them the ability to design restorations and orthodontic appliances on a computer display.

There are many different ways that laboratories and dentists might use the new technology. Dentists can, for instance, create a digital imprint and send it to a lab for restorative manufacturing, or they can undertake their own internal computer-aided design and milling in-house.

When labs get a digital impression, they can use the data to produce a stone model, then either carry out traditional fabrication as is or rescan the model for milling. As an alternative, the lab can use the photos it receives to perform all of the design work online.

The process starts with taking a digital image of the tooth/teeth, which is stored by the software as a 3-D image of a tooth. The software estimates the shape and size of the restoration using comparisons to surrounding teeth, and then sends that data to a milling chamber where the restoration is carved out of a solid mass of porcelain or composite resin. The dentist then checks the size and fit of the restoration before using resin cement to bond it to the tooth for a natural look and a durable fit.

How the CEREC System works for same-day restorations

CEREC was introduced in 1987 as the first dental system that uses digital scanning and a milling machine. It uses ceramic blocks that are readily available in the marketplace to produce restorations in a single appointment.

In preparation for scanning with CEREC, the dentist applies a layer of special titanium dioxide powder on the entire tooth. This makes the translucent portions of the teeth opaque and enables the camera to register all of the tissues. Next, several optical impressions are taken from an occlusal position, making sure to capture photos of the tooth that needs to be restored as well as the neighboring and opposing teeth. The scanner has the ability to focus automatically.

When the dentist finishes taking the impression, a 3-D image of the tooth that will be restored appears on the monitor. Based on this image, the dentist can mark the starting and ending points of the die. And using comparisons to the neighboring teeth, the software then provides a planned restoration that can be adjusted or improved as needed.

Once the design has been approved, milling can start. Simply place a block of the appropriate color ceramic or composite material into the milling equipment.

If the dentist doesn’t want to mill in-house, he can get a digital imprint and send the information to a dental lab. The lab can then use CAD/CAM technology to design and mill the restoration.

Advantages of cad/cam in dentistry

With CAD/CAM technology, you can have a damaged tooth restored in as little as one hour, compared to the several weeks required using conventional methods. Other benefits of the technology include:

Convenience – as mentioned before, the technology allows dentists to take impressions, design a suitable restoration, and place the fully customised restoration in only one appointment, except for all-ceramic bridges that require a second visit because the bridge is created in a laboratory. But the technology generally eliminates the need for temporaries, except for bridges.
Better fit – the technology provides greater control over the entire manufacturing process, which ensures that the restorations are accurately fabricated to fit comfortably and naturally with your bite.
Comfort – compared to conventional impression trays that use gooey gels, CAD/CAM technology employs digital impressions that are clean, fast, and comfortable.

Enhanced esthetics – many restorations are crafted on porcelain, which can be easily matched to the color of your natural teeth.
Durability – research suggests that CAD/CAM restorations are stronger than prosthetics milled from dated techniques, which makes them less likely to fracture. In addition, the materials used with CAD/CAM restoration have a similar composition to your natural teeth, which ensures that the restorations expand and contract at nearly equal rates with your natural teeth whenever you consume hot or cold foods and drinks.

Another benefit of using CAD/CAM technology is that the materials used are bonded to your teeth chemically, allowing the dentist to save as much healthy tooth tissue as possible while giving you a restoration that strengthens your tooth.

Disadvantages of CAD/CAM in dentistry

High initial cost – The practitioner must invest time and money in training, plus the initial cost of acquiring the equipment and software is quite substantial. Dentists who don’t do enough restorations may struggle to get a return on their investment.
Quality of results still depend on human input – The dentist must take an accurate optical scan of the tooth in need of repair, much like with traditional impressions. The scan must clearly replicate the adjacent and occlusive teeth and emphasize the finish line. Similar soft-tissue care, retraction, moisture control, and hemostasis techniques are needed for digital scanning just as they are for traditional imprints.
Some systems do not deliver fast results – Due to systems that have multiple stages, digital impression systems may not save time as expected. For instance, dentists who use specific scanners are required to send the photos for image cleanup before a dental technician sets the margins. The photos are then sent to the dental laboratory for approval before returning them for model milling. Only then can the dental laboratory fabricate the restoration using the models and dies that were sent earlier.

Applications of CAD / CAM in Dentistry

Early CAD/CAM technology made it possible to develop inlays, onlays, veneers, and crowns. With modern technologies, it’s now possible to also produce fixed partial dentures and implant abutments.

Moreover, this technology has influenced the field of orthodontics with the increasingly popular Invisalign (Align Technology, Inc., Santa Clara, CA, USA), which uses a number of clear, removable aligners designed and produced using CAD/CAM technology to straighten teeth.

Indeed, dental offices are increasingly adopting CAD/CAM technologies, with over 30,000 dentists worldwide own scanning and milling equipment, 10,000 of whom are in the US and Canada. This translates to more than 15 million CEREC restorations alone, globally.