By: Jean Johnson for Dental1
The horror stories about crowns are everywhere. The hygienist who sadly talks about how she sees crowns that fit so poorly they are plaque traps dooming tooth structures beneath. Then there’s the dental lab owner who looks knowingly at a room full of dentists and says “You wouldn’t believe some of the stuff that comes in our door.”
| Get (and Keep) A Good Crown|
When choosing a dentist or prosthodontist, find out if they have a good reputation, or have taken time for continuing education classes recently.
To better the visual match with your natural teeth, ask if you can visit the lab where the crowns are made, or at least consult with a person working in the lab.
You may get what you pay for so price your priorities – a better looking crown may be worth it for a front tooth but not for a molar.
Brush and floss your crown – keeping your crown clean will prevent decay and lengthen the life of your dental work.
Notify your dentist if you begin to see a dark line where the crown meets the tooth or if your crown shreds your floss. These can be an indication that the crown was not fitted correctly.
And hygienists and lab folks aren’t the only ones. “Some of the crowns I’ve seen look like the patients made them themselves,” observed one prosthodontist.
The question is, How does a patient know what they’re getting? What control, if any, can a patient exert to increase the odds that the crowns installed in their mouth resemble the equivalent of a brand new Mercedes – or at the very least a solid Subaru?
To get at some of these delicate issues we talked to Tom Hilton, DMD, MS, who is a restorative clinician in Portland, Ore., and professor at the Oregon Health Sciences University School of Dentistry.
In Search of “Good and Ethical” Dentists
“That’s the $64 question,” said Hilton in reply to our question about how patients can tell if the crowns going into their mouths are up to snuff. He explains that asking about a dentist’s background can be helpful, including the continuing education he or she devoted to dentistry specifically – and not just on the business side of their practice – in the past year or past five years.
As far as what type of dentist is best suited for placing crowns, Hilton takes issue with the idea that only prosthodontists can do quality work. “There are a lot of very competent general dentists who perform crowns at every bit as high a quality as many prosthodontists. And some prosthodontists do crowns worse than some general dentists.”
“But on the question of how a patient can know if they got a good crown or not,” Hilton said, “I think probably the best answer to that is if they got a good and ethical dentist that does it right.”
So it goes then in dentistry as in life; consumers who keep their ears to the ground to learn where the smart money is going will most likely find their crowns more to their liking.
Aside from problems inherent in trying to tell if someone is motivated more by sound ethics than self-interest, Hilton offers some concrete ways patients can at least begin to stay in the loop regarding their own restorative work.
Appearance Can Be a Key
Appearance is one thing, but even here, Hilton cautions that “there is no way you can duplicate natural tooth structure. Most dentists will tell patients that they will attempt to provide a crown that looks as natural as possible from a normal speaking distance about three to four feet away.”
Then again, he says that patients can take note if a telltale dark line starts appearing where the crown meets the margin of the prepared tooth. “A dark line starting to appear might indicate some leakage. It’s usually a delayed process, but if there is a lot of leakage it could happen in a few months. Or it could take several years.”
The Dental Lab
The dental lab with which a clinician works also has significant influence on the outcome of restoration work. “Part of the reason top-quality dentistry is expensive is that top quality labs are expensive,” said Hilton.
“Dentists that use good quality labs usually get good quality crowns, but the price is reflected in patient’s bills. Some dentists will leave the lab choice up to a patient. The dentist may offer an acceptable looking crown from one lab, or a more a lifelike crown from another lab. If it’s a crown on a molar, patients might opt for function alone. But if it’s a top front tooth they may say, ‘I want the best.’”
Hilton also suggests that patients who are willing to go directly to the lab can increase their odds of having front crowns they like. “Some teeth are more translucent than others and there are subtle characterizations as well, for example the bottom edge of some teeth is almost clear. That type of thing is difficult for a dentist to transmit to a lab,” said Hilton.
When asked if dentists would be offended by patients who asked to go to the lab so technicians could see all the nuances of their teeth, Hilton was momentarily surprised. That is, until we reminded him of how many of us are intimidated by the healthcare system and tend to view the patient-doctor relationship as one in which the doctor is the supreme authority not to be questioned. But once Hilton realized the source of our question, we found his answer instructive.
“We routinely do that in our office. Since the lab is right in the building with us, we just have the lab tech come up,” he said. “But I can’t imagine most dentists being offended by that. Instead I think most dentists are more concerned about convenience for their patients.”
According to Hilton, “Most dentists might think something to the effect of ‘they (the patients) already have to see me and now I’m asking them to go the lab and make sure the shade is right.’ So I think if the patient was willing, they’d actually kind of like it because it reduces the chance that when the crown comes back it’s not going to be a good match on the shade.”
Matters of Fitting
As far as the initial fit goes – whether crowns slip easily into place right from the lab or take some doing to get correct before they are cemented – Hilton says that there are too many variables involved to draw conclusions here.
“Taking impressions and pouring them up into a model is the first step in making crowns. Then the lab has to fabricate a wax up to the model and then that’s cast,” he said. “So in every step along the way there are going to be some inaccuracies and you will inevitably end up with something that is going to need to be adjusted.”
“Also, teeth tend to shift over time and the space accommodating the crown might not be quite the same size as when the tooth was first prepared.” More, Hilton points out that when adjusting crowns, dentists have to “go very slowly, shaving a little off and trying it in and so on. Sometimes it can take awhile.”
But on matters of final fit, if patients are flossing a new crown and find that their floss shreds, a red flag should go up. “It might be an indication that there is not a good adaptation of the crown with the tooth margin, and that there is an overhang that needs to be adjusted.”
Foundation and Materials
Crowns fit over a number of materials and situations – tooth structure that has been cut down, posts, and implants. Where it gets tricky is when the crown covers something dark in color, either dark tooth structure or metal posts. Also, to temper the gray shadow, yellow gold is sometimes used for posts. Added to that, choices in crown materials go a long way in complementing foundation work.
“The prettier crowns are made from porcelain. They are all ceramic, but consequently if they go over a post, they will have that dark shadow or graying effect that shows through,” said Hilton. “So in that situation, we typically have to go to a different material.
“We have new ceramics out there now that are very dense and opaque enough to block the metal from showing through. The advantage is that with their substructure they are stronger, but they don’t have quite the same qualities of providing a real life-like restoration.”
That said, Hilton added that these types of crowns are “quite good, and I think the average person might be hard pressed to tell the difference between crowns made from the new ceramic materials and the more traditional porcelain crowns.” Still, he noted that the idea of “as the strength goes up the prettiness goes down is somewhat of a truism.”
The third choice in crowns still has the porcelain on top, but the substructure is made from gold or metal alloys. “This one is the strongest crowns, but it’s more difficult to get a good life-like appearance with these types of crowns.”
The Art of Tooth Restoration
In sum, trying to replace what Mother Nature provided is an art with many variations on the theme. Thus, patients needing crowns will find they are well-served by first educating themselves then checking out their dentist as carefully as they might research a new car. Finally, patients should remember that in matters of health, skimping on budget deals is probably taking on more risk than will be comfortable over the longer haul.