CEREC-type restaurations
Chairside-Economical-Restauration-Esthetic-Ceramic
The CEREC-type restoration is the result of cutting-edge technology for the benefit of the patient, developed 30 years ago and continuously improved since then. The name CEREC comes from an English acronym which means “Chairside-Economical-Restauration-Esthetic-Ceramic Restoration”. In fact, it makes it possible to fabricate a high-quality ceramic restoration in a single visit. Crowns and indirect inlays are the most commonly used restorations.
It is also possible to fabricate crowns on implants, temporary acrylic bridges, permanent ceramic bridges or ceramic veneers. Thanks to recent advances, this technology now allows the creation of surgical guides in implantology by integrating 3D scan technology.
Choice of material: ceramic
To this day, dental ceramics remains the material that most closely resembles tooth enamel in its rigidity, texture and the way it reacts to temperature variations when you eat. It is a highly biocompatible material that restores strength to a damaged tooth. In addition, it provides great chewing comfort and wear that is similar to natural tooth enamel, which is beneficial for the tooth itself and for neighbouring teeth. In fact, the contact between adjacent teeth remains tighter, which avoids the unfortunate situation of having food get stuck between the teeth. In addition, the rate of tooth wear during chewing is more similar to the friction wear between two natural teeth. This reduces the risk of premature wear (attrition) or breaking of neighbouring teeth.
Under what conditions is a CEREC restoration necessary?
A CEREC restoration is mostly built to strengthen an adult (permanent) tooth that has a large cavity, is broken or already has a large amalgam or composite restoration. It may also be indicated to strengthen a tooth that is painful because of a crack (Cracked Tooth Syndrome). The dentist is the only one who can diagnose this type of lesion and recommend the appropriate treatment for your situation.
What are the advantages of CEREC restoration?
In addition to the advantages of biocompatibility and comfort, the CEREC-type ceramic restoration offers advantages from a more technical point of view. Because it is fabricated at the same appointment, it allows the dentist to keep a larger, healthier portion of the tooth. In fact, the bonding bond that joins the tooth to the ceramic is known to be stronger in terms of healthy enamel and it allows for the preservation of certain walls that would have to be removed if the restoration were made in two visits. According to scientific studies, a CEREC-type ceramic restoration restores 98% of the strength of a virgin natural tooth. It offers better durability than white composite fillings.
In addition, this technology allows the patient to receive the restoration in a single visit. This means only one anesthesia and no temporary restoration that usually has to be worn while waiting for the ceramic piece to be designed in the laboratory. This temporary piece tends to be brittle, tends to peel off and may cause temporary cold pain. In addition, in the case of temporary inlays, because the temporary restoration is held in place only with temporary cement, the remaining tooth is not yet as strong and is more likely to break.
CEREC technology also uses a digital or video camera, depending on the generation used by the dentist. This camera creates a 3D model from which the ceramic piece is designed. This eliminates the need to take impressions in standard materials, which can be difficult to tolerate or give some people a hard time.
Finally, this restoration usually remains less expensive for the patient and allows the dentist to be competitive in price compared to a laboratory fabricated restoration. The latter require transportation, impressions and the use of various other more expensive technologies and materials, in addition to the inconvenience of requiring two visits.
How does CEREC work?
Digital Impression
The design of a CEREC-type ceramic restoration is mainly divided into three stages. The first step consists of capturing images of the preparation made by the dentist using a digital or video camera, depending on the generation of the device used.
Computer-aided design
The second step is to virtually create the restoration using a specialized computer program. The dentist can then analyze the preparation, define the contours and draw the restoration in 3D using several virtual tools. This is similar to technical drawing used in many fields of technology. It is often referred to as CAD-CAM technology (Computer Assisted Design-Computer Assisted Manufacturing). Finally, the drawing is sent to a machining chamber.
Selection of the block to cut
Various dental companies supply high quality hot-pressed ceramic blocks for making these types of restorations. The dentist can choose the colour and size of the block at that time. There is a wide selection of very esthetic shades and blocks with colour gradations to offer the patient a restoration that perfectly matches the natural shades of the tooth.
There are also more fracture-resistant ceramics (E-MAX ») that are indicated to strengthen a short tooth that has lost height over the years due to wear (attrition) or a fragile tooth in a patient who generates large forces by clenching or grinding teeth (bruxism). There is also a category of pressed composite material blocks (a family of polymers such as white fillings) that can be used in the same cases as those mentioned above. The size of the block is determined by the computer software according to the size of the restoration to be made.
Machining of the ceramic part
The next step is to insert the selected ceramic block into the milling chamber. This unit is equipped with two 5-axis rotary instruments, which will cut the block and reproduce the computer-generated 3D drawing. A jet of water and oil is used to control the temperature and reduce friction to obtain a very precise cut of the ceramic block. Depending on the type of restoration, block, and milling machine used, there is a 5- to 20-minute machining time.
Baking of the ceramic piece
Some blocks must be baked to reach their full strength, such as E-Max? ceramics and Zircon. Other ceramics can be glazed and fired in the kiln to improve their strength or to colour them for superior aesthetics. This step requires more time and is therefore slightly more expensive.
What are the limitations of CEREC ceramic restorations?
Although the advent of ceramic chairside restorations remains a very interesting advance for the patient and the dentist, this technology has certain limitations. Despite the fact that ceramic is the only restorative material capable of strengthening the tooth, it remains expensive compared to amalgam (grey filling) or composite (white filling) restorations, which remain alternative choices in these situations. Mercury amalgam restorations are not offered at our clinic for health reasons (see mercury toxicity).
In addition, ceramic restorations require a minimum thickness and width to achieve good strength. When the dentist needs to remove too much natural tooth substance to achieve the minimum required dimension, it is better to choose a composite filling. Finally, it is important to take into account the time required to fabricate the restorations (drawing, machining and firing). For the majority of cases of more than 4 units, it is preferable to place the restorations during a second visit. In this case, an impression is taken (either with a viscoelastic material or with the CEREC device and sent electronically to the laboratory). If two visits are required, the dentist prepares temporary restorations. Permanent restorations will be fabricated either by an external dental laboratory or by a team member using CEREC technology. When restorations are fabricated at the clinic, this often results in a shorter fabrication time compared to cases that are sent to the external laboratory.