Cosmetic Dentistry Blog Cosmetic and General Dentistry Questions Answered

September 21, 2018

Gap between my crown and my bridge


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I have a space between my 2 front teeth, however one of my front teeth is a crown and the other front tooth is part of a bridge. Can the gap between my front teeth be closed with Lumineers or any other procedure or would I have to get a new bridge and crown, possibly all in one structure to close the gap?
– Laura from Nevada

Laura,
Your question prompts me to ask a question of my own: Why did the dentist who made the crown and/or the bridge leave a gap between your front teeth? The easy way to fix this would have been to make them correctly in the first place.

At this point, yes, you pretty much need to have probably both of them re-made—depending on how big the gap is. Both front teeth need to be the same size—you don’t want to close the gap from just one side by making one side larger.

this microetcher has a long nozzle with a button on it, and at one end a small clear plastic bottle as a reservoir

A Micro-Etcher

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But there is a procedure you might want to try before doing that. There are ways to bond composite to porcelain, and you could start with trying that—treating this as a dental bonding case. If the dentist has what is called a micro-etcher, which is a small sand-blasting handpiece, he or she could micro-etch the porcelain surfaces next to the gap. This would be followed by etching with a hydrofluoric acid gel and then priming the surface with a silane coupling agent. A bonding resin would then be applied followed by composite bonding material to match the shade of the crown and the bridge. The composite would be shaped and polished. In theory, this should work. However, my experience with bonding to porcelain was that after a few months, we would see staining along the margin between the composite and the porcelain. But it could be worth a try to try to avoid the expense of a complete re-do of your front teeth.
I would think it goes without saying that you need an expert cosmetic dentist to do this, such as we recommend on this website.

The company that makes Lumineers, a few years ago, tried to promote the idea of bonding Lumineers over the top of porcelain crowns, but I strongly discourage that. You would get the same risk of staining at the margins, and would spend the same amount of money as you would spend just re-doing the case completely. Click the link to read more about the problems with that approach.

– Dr. Hall

Do you have a comment or anything else to add? We’d love to hear from you. Enter your comment below.

Click here to ask Dr. Hall a question of your own.

About David A. Hall

Dr. David Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does complete Internet marketing for dentists.

July 9, 2016

Why does my crown keep falling off?


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Dr. Hall,
I have had a crown put on by a dentist and it was done same day. No temporary. Not sure what type of material he used for the crown. It fell out three times in less than a year. I went to a different dentist on the fourth time it fell out and he replaced the setting with a new one stating the other dentist didn’t create a good setting. This new crown is Zirconia Porcelain and it has fallen out twice in a month. He is suggesting a full porcelain crown on the same setting as he states the cement is adhering to my tooth but not the crown. He says the all porcelain has a more rough underside to adhere to the cement better. Any suggestions on what my next move should be?
– Stephanie from North Carolina

Stephanie,
Your same-day crown was a CEREC crown or a similar type that is milled by a computer in the dental office while you wait. But when properly prepared and bonded on, it will stay on permanently. It’s not the material your crown is made of. Gold crowns, porcelain crowns, CEREC crowns, zirconia crowns–all of them can be made to stay on solidly, permanently. I have most of those types of crowns in my own mouth and they stay on just fine.

There are two main factors for retention of a dental crown–the bonding strength of the cement, and the shape of the tooth preparation. Of those two, the shape of the tooth preparation is far more important. If the tooth is prepared with only a slight taper, a crown can be cemented with a very weak cement and it will still stay on. If it is prepared with a lot of taper, some of the strongest cements will not hold it on.

I’m not saying that getting a good bond between the crown and your tooth wouldn’t solve your problem. The strength of the cement is a factor. And I know very little about your tooth and the techniques these dentists used. But I do know that a tooth prepared with good retention form will not have a crown falling off three times in less than a year, regardless of the cement used. So even though I know very little about your tooth, I’m pretty confident that it was prepared with inadequate retention form.

So what should your next move be? I would find a dentist who knows how to do crowns that stay on. In 23 years of dental practice, I never had a crown fall off of any that I did for my patients, so I know it can be done.

For further understanding of this principle, of creating a crown that stays on, see my blog post from about nine months ago, “The main reason your crown probably fell off.”

I hope this is helpful.
Dr. Hall

Do you have a comment or a question or anything else to add? We’d love to hear from you. Enter your comment below.

Click here to ask Dr. Hall a question of your own.

About David A. Hall

Dr. David Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does complete Internet marketing for dentists.

January 18, 2016

Can you bond a Maryland Bridge to porcelain crowns?

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Dr. Hall,
Can you place a Maryland bridge between 2 teeth that are porcelain crowns on implants?
On my upper right, I’ve been missing my first molar and my first premolar. There was another tooth between them, but that’s going to have to be extracted. Can my dentist just put a Maryland bridge in there and attach it to the teeth on implants on either side?
Thanks

Ed G

Ed,
The simple answer is that yes, you can attach a Maryland bridge to existing porcelain crowns, but it’s very tricky and questionable whether it would hold up over time.

Maryland bridge diagram

Diagram of a Maryland bridge

Many dentists have problems with Maryland bridges, resulting in a short lifespan for the bridge. They seem really simple to place—grind the adjacent teeth a little to make space for the metal framework, and then just bond it on. But it’s not quite that simple. There should be certain grooves placed in the preparation to resist the forces that will occur. Otherwise it is very easy to dislodge a Maryland bridge.

And you have the added complication of having porcelain crowns on the adjacent teeth. The ideal is to bond the metal wings of the Maryland bridge to enamel. That gives the strongest bond. Bonding the bridge to porcelain is inherently weaker, even if it’s done right. And very few dentists know how to bond to porcelain.

Then there is the additional complication of having to prepare the teeth with the porcelain crowns so that they have the proper grooves, with retention and resistance form that will help keep the bridge from coming loose. Placing proper grooves could cause the groove preparations to go through the porcelain entirely and reach the underlying metal. Now, instead of bonding to porcelain, the dentist needs to bond to metal, which is more difficult still.

So yes, it can be done. But it’s a high-risk, difficult procedure.

The ideal would be if the dentist would anticipate this possibility back when the original implants were placed. Knowing there is one natural tooth left between the implants, the dentist should be anticipating that at some point in the future the patient could lose that tooth. Then the implants for the missing teeth should be placed so that the abutments end up parallel and then use a screw-retained crown. When the tooth in between is lost, the dentist would simply unscrew the adjacent crowns and replace them with a bridge.

Another solution would be to place a third implant in the missing space, assuming there is enough space in the bone to accommodate a third implant.
– Dr. Hall

Do you have a comment? We’d love to hear from you. Enter your comment below.

Click here to ask Dr. Hall a question of your own.

About David A. Hall

Dr. David Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does complete Internet marketing for dentists.

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