CEREC or E4D ceramic crowns, inlays and onlays

CEREC or E4D ceramic crowns, inlays and onlays

What is a dental crown?

The crown is the visible part of the tooth located above the gum line.

The crown is covered with enamel and protects the most sensitive parts of the tooth (dentine and pulp) from food, air, saliva, bacteria, and microbes.

Dental crown restoration

The crown of a tooth can undergo different types of damages. The most frequent are tooth decay, trauma (accident), or the presence of cracks or fractures. Regardless of the cause of the crown deterioration, it is important to repair or replace it, depending on the severity of the injury.

Three types of materials are traditionally used to repair parts of a dental crown:

  • Amalgam restoration (grey filling);
  • Composite resin restoration (white filling);
  • Ceramic, resin or gold inlays or onlays to replace a large part of a damaged crown or a defective filling (when a new filling is not the ideal solution).

When the crown portion of a tooth needs to be fully replaced, it is also possible to create a complete artificial crown which is then glued or cemented onto the remaining structures of the natural tooth.

Traditionally, the production of an artificial crown, inlay or onlay requires several dentist appointments in order to complete all the stages of the treatment plan. During the first appointment, the tooth that will receive the crown is prepared (filed down). Impressions of the teeth are taken and a temporary crown is installed on the damaged tooth. Two weeks are usually necessary for the production of the final restoration in an external laboratory. During the second visit, the final restoration is fitted and cemented or glued onto the tooth. For aesthetic reasons, it is sometimes necessary to plan an additional fitting appointment.

For some years now, dentists have taken advantage of the CEREC or E4D cutting-edge technology, a computer-aided method that allows creating inlays, onlays or crowns directly from their clinic.

What is CEREC or E4D technology?

Historical background

The CEREC technology was the first of this type to be available on the market. The meaning of CEREC has evolved throughout the years, from “CEramic REConstruction” to “Chairside Economical Restoration of Esthetic Ceramics”. The E4D has appeared more recently in the dentists’ offices. While it comes from a different company, it is very similar to the CEREC technology. Both methods provide patients with the same high-quality ceramic restoration done in one appointment.

This type of restoration is relatively new because it has only been used on patients for the first time in 1985. Since then, the number of dentists using it is on the rise. It has become essential for many dentists to master this technology because patients are increasingly requesting it. According to the latest statistics (2013), about 38,000 dentists use CEREC or E4D technology worldwide and almost 7 million restorations are performed each year, for a total of 28 million restorations carried out since this technology is available. These figures are expected to climb because this technology is still growing. Indeed, new applications are developed and material upgrades are continuously done.

The basic principle behind the CEREC or E4D technology

The CEREC or E4D technology allows creating inlays and onlays (partial crowns) or full crowns in one appointment. It is a computer-aided design and computer-aided manufacturing (CAD/CAM) dental system.

The resulting restoration can replace a full or partial natural tooth crown that is not functional anymore. It is also used to substitute a faulty or damaged filling.

Equipment used and treatment steps

CEREC or E4D technology allows the dentist to design, produce and install custom-made ceramic (porcelain) restorations in a single appointment. In order to do this, the dentist uses:

  • A camera that takes digital images of the problematic tooth, adjacent teeth, antagonistic teeth (located on the opposing arch) and occlusion (contact between teeth);
  • A design software that uses the images from the camera to model the crown or inlay;
  • A computerized robot that produces the crown or inlay by milling the actual restoration from a solid block of material using diamond burs. A delay ranging from 5 to 20 minutes is usually required for this step. The crown or inlay is then ready to be bonded to the tooth using a high-performance resin cement. In fact, a thin film of adhesive cement is used and the strength of the resulting joint is superior to formerly used adhesives.

The first generations of CEREC technologies were using bidimensional (2D) models. Since the beginning of the 2000s, a 3D model is produced by the design software. The crown or inlay produced with CEREC or E4D technology can be created by the computerized robot that reads 3D models.

It is worth noting that some dentists that offer CEREC or E4D restorations do not have, for some reason, the milling unit that makes the artificial crown or inlay on the spot. The dentist chooses to send the digital images to an external dental laboratory which will be in charge of the fabrication. In this case, the patient may not receive a crown or inlay in one appointment because of the processing and delivery time. However, the patient will still benefit from a very high-quality restoration.

Benefits of CEREC and E4D technology

  • Rapidity: The ceramic crown or inlay is produced on site, at the dental office, within a short time frame, which allows restoring your teeth to their natural beauty and function in one appointment. This technique saves valuable time and provides quick results.
  • Comfort: Only one local anesthesia is necessary to prepare the tooth to receive the crown or inlay (traditional methods require two).
  • Accuracy of the dental impression: the dentist uses a digital camera and computer-assisted design and production to make the CEREC or E4D ceramic restoration. Digital impressions are very accurate and more comfortable for the patient than the bulky traditional impression material placed in a tray designed to take an imprint of the dental arches, not to mention the debris often left in the mouth after the procedure.
  • Transparent machining process: the patient can see the real-time fabrication of the crown or inlay by the computerized robot, allowing to become familiar with the milling process.

Usinage de dent

  • Milling precision: The size and shape of the crown or inlay are more accurate since the dentist creates the dental restoration with the help of a software. The computer-assisted design is based on a very accurate 3D model obtained from 3D images.
  • Safety: This technology is regarded as being very safe and is backed by hundreds of scientific studies.
  • Aesthetics: The ceramic is translucent and has the ability to mimic the properties and appearance of natural teeth. Available in large variety of colours, the ceramic restoration will blend in perfectly with the other teeth. In addition, its colour will remain relatively stable over time.
  • Biocompatibility: Ceramic is made of silica particles and is a very biocompatible material, which means that it can exist in harmony with human tissues without causing deleterious changes. It is thus recommended in individuals with allergies or hypersensitivity.
  • High success rate: According to recent clinical studies, the success rate of a CEREC or E4D ceramic crowns or inlays stands at 95% over 10 years, which is great compared to other types of crowns and inlays.
  • Durability and strength: Ceramic is a very resistant and durable material, which protects the crown or inlay from breakage and damage during mastication. In addition, CEREC or E4D crowns and inlays can solidify weakened teeth and restore 98% of their original strength.
  • Preservation of natural structures: When a filling must be replaced, the dentist must first remove the filling as well as a small part of the healthy tooth. Ceramic inlays and crowns have a much longer lifespan than white or grey fillings, which allows the patient to keep the healthy and natural part of their teeth longer. Also, as CEREC or E4D restorations are done on site, the dentist is able to preserve weaker parts of the tooth which would not have resisted the waiting period necessary for a restoration made in a laboratory.
  • Purity and quality: Ceramics used to make the CEREC or E4D crowns and inlays are standardized and free from impurities.
  • Predictability: Ceramics used for CEREC or E4D crowns and inlays do not expand or contract when exposed to heat or cold. The patient does not experience discomfort, sensitivity or pain in response to temperature changes, unlike what happens with other restorations like amalgam fillings.

Disadvantages of CEREC or E4D technology

  • CEREC or E4D crowns and inlays may not be the ideal solution for some patients depending on their dental history or the location of the tooth to be restored.
  • CEREC or E4D technology is not used by all dentists because it requires a substantial investment of money and time to acquire the necessary equipment and to learn how to use it properly. As a result, patients who want to enjoy the benefits of CEREC or E4D technology must sometimes visit a different dental clinic. Depending on the region where they live, some patients may have to travel a considerable distance to take advantage of this technology.
  • CEREC or E4D crowns and inlays can be more expensive to manufacture than other kinds of restorations (amalgam or composite). This disadvantage is offset by the fact that CEREC or E4D dental restorations are more durable and aesthetic. Mostly, they are the only restorations that are able to strengthen a weakened tooth. This can justify paying a little more money to protect a tooth.

Other applications

In addition to crowns and inlays, CEREC or E4D technology is used to make dental veneers (thin layers of material placed over teeth to improve the aesthetics of the smile), bridges and implant-supported crowns and posts, according to the choice of your dentist.

Since 2009, some dentists specializing in implants also use CEREC or E4D technology and 3D X-rays (cone-beam computed tomography (CBCT)) to practise integrated implantology.

The methods traditionally used in implantology involve 2 steps: a surgical procedure, which is the insertion of an implant into the jawbone, and the fabrication of the crown that is then attached to the implant. These two stages are often performed by two different dental health professionals who need to plan their individual work while cooperating together to achieve a functional and aesthetic result for the patient.

With CEREC or E4D technology, the dentist can plan these two stages at the same time, thus shortening the treatment time. In fact, computer-aided design and manufacturing of the crown offer optimum and precise results. The restorative dentist can control all the treatment steps, including the dental crown production, on site, in his office. Dentists who do not use CEREC or E4D technology must rely on an external laboratory for the dental crown fabrication, resulting in additional delays during the second stage of the treatment.

Dental professionals who install dental implants can also use CEREC or E4D technology to manufacture surgical guides (drill templates) used during the insertion of implants into the jawbone. The use of surgical guides allows for more precise surgery. The results are therefore more predictable for the surgeon and the restorative dentist.

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