Cerec Details
Dental procedure is an alternative to traditional crowns
By Lois M. Collins
Deseret Morning News
Dixie Nielsen has a tooth that’s a candidate for a crown. It has long had a large "silver" filling, which has expanded and contracted enough times over the years to change, and not for the better. At the least, it needs to be replaced.
Garon Larsen, a dentist at the Alpine Dental Clinic in Alpine, explains that teeth with large metal fillings often at some point must be crowned. Expansion and contraction has cracked the tooth or there’s decay under the filling. But if too much of the tooth is gone, replacing the filling simply isn’t going to work. Besides, that filling material contains mercury, which he figures may not be really healthy.
Repairing such a tooth has, most of the time, meant the need for at least two dental-office appointments, usually two or more weeks apart. One to have the tooth prepared for a crown and an impression taken so it can be sent to a lab to have the crown manufactured. The tooth is ground down to a peg so the crown can be bonded over it, like a stocking cap on a head, then a temporary cap placed on it to prevent pain until the permanent crown comes back from the lab.
Nielsen, however, is going to get all the work done in a single visit that takes close to an hour, thanks to an increasingly popular dental repair called CEREC, which can be used on a crown, a veneer or a filling.
CEREC is shorthand for "Chairside Economical Restoration of Esthetic Ceramics."
With CEREC, the tooth is not ground to a nub for a crown to cover. Instead, as much of the tooth as possible is left intact. The filling is drilled out and a reflective powder is placed in the opening that’s created so that it will reflect light. Then a tiny camera is placed in the mouth to take a three-dimensional photograph of the tooth, which is transmitted to a computer-aided design program on a computer. That picture is the process’s equivalent of a dental impression.
It’s not all automated. The dentist does some of the work of creating the design that will become an inlay or overlay.
There are always a few adjustments, but not too much," Larsen notes as he moves the mouse to outline the section of tooth that’s being replaced. The goal is to get it close enough to the neighboring tooth that floss will go through, but not food.
When the dentist is happy with the image, it’s sent to a special machine where a small piece of tooth-colored (there are different shades to match teeth) and very strong ceramic is shaped precisely using a high-speed diamond burr and a disk mill. After a few minutes, the piece is complete.
The restoration is etched so it will bond, then a special type of glue is applied and cured briefly with a light. Within minutes, Nielsen’s tooth looks as if it never needed any work at all.
Many people have never heard of CEREC, though it’s nearly 20 years old. It debuted in Europe and has undergone some changes from the original technology. It arrived in the United States more than a decade ago and has slowly caught on, aided now by a simpler 3-D version that was introduced about a year ago.
Still, only an estimated 2-3 percent of Utah dentists have the technology, distributed solely in this country by Patterson Dental, because the technology costs around $95,000.
Larsen says there are many advantages, but it’s not for every tooth. Although CEREC provides a new option for some teeth, dentists have to be selective. Some teeth still require a conventional crown.
Myles Preble, a dentist in Salt Lake City, has used CEREC for almost five years.
The technology is much more user-friendly now. The new 3-D version (CEREC 3-D) is so much nicer. You can mill in more of the anatomy instead of having to cut it in."
But even with the earlier CEREC models, he says, he has had no breakage. That’s a tribute to the material, he notes. It’s more dense.
The goal with CEREC is never to go below the gum line, Preble says, and that makes it "look like it grew there."
As many as four teeth can be done comfortably at a time, he says. And although the American Dental Association still also backs use of silver amalgam fillings, he prefers CEREC. "To me, there is no comparison. It’s absolutely great. It’s the best restoration technology can provide and the most toothlike. It should be there a long time."
Nelson Glassett, a dentist in Salt Lake County, says about half his patients choose a crown and half choose CEREC. It’s an option that insurance covers as it would a crown. Glassett has used it for both crowns and inlays and likes the fact that he knows right away how it’s going to fit. "With CEREC, we can take a picture of the bite, the opposing arch, we can make it go up and down and see where it’s hitting."
He doesn’t underestimate the benefits of getting the job done in a single visit, either. When a crown comes back from the lab, if it doesn’t fit he has to make a new impression and send it back, adding another couple of weeks to the process. With CEREC, if he has one that didn’t mill perfectly, he makes an adjustment, fixes it and fits it right then. But that’s a rare occurrence.
That’s one of the biggest points. The time for the patient. The other thing is the materials used to mill the crowns or onlays or inlays are out of material that’s extremely compatible with natural enamel, so it won’t cause more wear to the opposing teeth. For people with a porcelain crown, it’s so strong it wears away enamel over time."
He’s had only one CEREC restoration break. "That result came by something I did wrong. Once I understood what it was, I haven’t had one break since then."
When he can, Larsen prefers CEREC, which costs about the same as a crown. The tooth will have 95 percent to 105 percent of its original strength, he says. It looks nice and never leaves the telltale silver line around the gums, something that’s the norm with crowns because of the metal understructure. Because there’s no metal involved, there’s no risk of a metal sensitivity reaction. And it’s expected to last at least as long as a traditional crown.
With a traditional crown, the impression is made of the gap left in-between teeth. The CEREC impression is of the tooth itself, so it looks just like the original.
Perhaps most important, it preserves as much natural, healthy enamel as possible, something that may be important later should a tooth require more work. Who knows, he says, what technology will come along during the CEREC restoration’s lifespan? Once the natural healthy enamel is ground away, it can’t be reclaimed.
"Awesome," says Nielsen, of American Fork, holding a mirror up to check out her improved tooth.
This article was syndicated from Deseret News