CMBRs as an Alternative to Crowns
Ceramo Metal Bonded Restorations (CMBRs) are typically partial coverage replacements for portions of back teeth. They are bonded to the remaining healthy enamel of teeth. These may be used to preserve those portions of a tooth which are not decayed or filled. The use of adhesives allows teeth to be restored while preserving up to 70% of the tooth while a traditional crown (the most common substitute) usually involves 100% of the tooth to gain mechanical retention.
The Procedure
The procedure starts by removing all of the decay and existing filling in the tooth. The remaining tooth is shaped slightly to accept a reinforced porcelain restoration.
An impression is made of the tooth and a temporary is made to stabilize the dental arch. The impression of the prepared tooth is sent to a special dental laboratory where the restoration is fabricated.
The restoration takes about two to four weeks to fabricate.
After the restoration is returned from the laboratory it is tried in. A special conditioning solution is then applied to the prepared tooth. This allows the porcelain restoration to bond to the tooth surface. The CMBR is bonded to the tooth with a special glue that is hardened by the application of a blue light source. The excess set glue is then trimmed and polished. The final restoration can provide the patient with excellent esthetics and is often very difficult to distinguish from the original tooth surface.
Longevity
CMBRs, though the most durable and conservative mode of treatment, are not permanent. With aging it is common for the edges of the restoration to chip. It is possible these areas could decay if they are not kept clean by regular brushing. Also, the underlying tooth color can change after placement. After a longer period of time, as in all fillings, the material will weaken and may break under normal chewing.
CMBRs can also be damaged or broken by attempting to pry objects with your teeth. As with all restorations, the gum tissues are more susceptible to irritation. However, this is usually prevented with conscientious home care.
Generally speaking, CMBRs may be expected to last between four and ten years. After this time the restoratons may be redone or replaced.
What is a CMBR?
The CMBR is a highly conservative and durable tooth replacement made of an esthetic ceramic which is reinforced with an internal metal supporting structure. These restorations are custom made for each individual tooth in a dental laboratory by highly trained and talented dental technicians. The fabrication technique requires an excess of one hundred separate technical processes. After fabrication they are bonded to your natural teeth to form a lasting and sealed union between the restoration and your tooth. Once bonded in place they can successfully replace decayed, filled, and missing tooth structure in a way which is undetectable from that of the natural virgin tooth.
The Treatment Process
On your first appointment, the tooth will be prepared to provide space for the restoration. This usually requires removing any existing fillings and thinning the chewing surface of the tooth down the thickness of a few fingernails. Molds are then made of your prepared tooth. Before the patient leaves this appointment, their tooth preparation will be protected by a temporary restoration. Some sensitivity after this appointment is common, particularly to hot and cold.
On the following appointment, usually two to four weeks later, the CMBR, which was fabricated by our dental laboratory, is tried in. If it fits to our satisfaction, and the patient likes the appearance, it is bonded to the prepared tooth. On the following appointment the edges of the restoration are polished and any final adjustments are made.
Our goal is to provide the patient with attractive teeth without sacrificing healthy tooth structure.
What is the longevity of CMBRs?
CMBRs, though more durable than the directly placed plastic fillings, have some limitations. It is impossible to determine their exact shade and final appearance. In addition, the cements used to attach them are new and it is not known exactly how long they will last. Breakage is a possibility with any restoration, particularly those made of brittle materials, like porcelain. Care should be taken not to place excessive force on those teeth treated with CMBRs.
Normal chewing forces will rarely result in breakage unless many years have passed and the materials fatigue. It is also possible the gum tissues may be irritated from the restorations themselves or from the cements used to bond them. Generally, this can be controlled with conscientious home care.
The final restoration is adjusted to fit the patient's bite. However, it must be remembered any change in ones bite, may take some time to become accustomed to.
Overall Accessment
We feel with all things considered, CMBRs offer the patient a conservative method of treating damaged or unattractive posterior teeth. We feel confident that they are a good choice for many of our patients and can offer them a pleasing smile for many years to come.
In the final analysis, the CMBR is the preferred method of treatment for many patients.
Alternatives to CMBRs
Their are a number of new dental porcelain systems available which have a reinforcing ceramic core which can be used as a substitute for metal support. These systems have the potential of being slightly more esthetic than a CMBR since a ceramic core can be made in different shades to help better match the shade of your tooth. The disadvantage of these systems is that they are relatively new and have not yet proven themselves over long term clinical use. They will probalbly not be as durable as a CMBR over long periods of use, but to have an advantage when maximum esthetics is one of the prime goals to treatment.