Will A Ceramic Onlay With A Strength Under 370 MPa Work For A Second Molar?

Discussion in 'Dental Restoration' started by noesis, Sep 13, 2018.

  1. noesis

    noesis

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    I have a broken cusp on a second molar, tooth #18. There is no decay on the tooth and it doesn't need a root canal treatment.

    A dentist who was recommended to me suggested fixing it with an onlay, which she described as a 3/4 crown. She will use either Cerec with Celtra Duo, a zirconia reinforced lithium disilicate material (milled and polished method), which has a flexural strength of 210 MPa. Or, I can get a lab made crown using traditional dental molds for the impression, with IPS e.Max, which has a strength of 360 MPa.

    When I asked about zirconia, ideally the translucent kind, which I understand is the strongest tooth-like ceramic (with a 600-750 MPa), this dentist said that she doesn't use zirconia.

    If I have this dentist do my onlay, I am leaning towards e.Max because it has a longer track record and it is stronger than the Celtra Duo (when using the milled and polished method).

    Please note that when Celtra Duo is glazed and fired, its strength increases to 360 MPa. However, this dentist doesn't fire the crowns. Overall, I am worried about trying either of the recommended ceramic materials because I think they are too weak and will break in a short time, if used on a second molar.

    To complicate matters, I live in the Boston area where the cost of dental services is astronomically high and I have no dental insurance. So, I want the onlay to last as long as possible for both cost considerations and because I don't want to risk repeatedly drilling on the tooth, which might cause me to need additional dental treatment.

    Could there be a reason why a dentist would recommend weaker ceramic materials for a second molar when those materials are usually used for crowns in the front of the mouth? Should I go with the e.Max option? Or, should I find a dentist who uses zirconia for second molar crowns?

    Any information or advice on this matter would be greatly appreciated.
     
    noesis, Sep 13, 2018
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  2. noesis

    MattKW Verified Dentist

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    For 2nd molars I prefer to try and talk patients into a high-noble crown (white or yellow gold). The 2nd molars are typically quite short and you want to keep as much natural tooth structure for a sound foundation. A gold alloy
    can be very thin, biocompatible, kind to opposing teeth, easy to adjust, and indestructible; but you have to be OK about the colour. 2nd choice would be monolithic zirconia as least destructive removal of tooth structure for max strngth. 3rd choice is monolithic eMax. If you layer a zirc or eMax there is greater risk of chipping. May not be significant, very hard to be sure when we start talking in MPa as a simple measure of estimating the overall strength of a restoration.
     
    MattKW, Sep 13, 2018
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  3. noesis

    noesis

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    MattKW, thanks for your reply.

    I asked the dentist about an onlay, rather than a crown, because I would like to keep as much of the natural tooth as possible. My preference, however, is to avoid metal and have the onlay blend in with my other teeth. Believe it or not, it is very difficult to find a dentist in my area who offers gold crowns. Most of them recommend zirconia for 2nd molars. I was surprised when this dentist said that she does not use zirconia because she is listed as a "Top Dentist" in my city's major magazine.

    I have been trying to find a dentist to fix my tooth since mid-July. The ones I have contacted are either too expensive for my budget or they don't use materials I feel comfortable with. Are there any risks to waiting a month or so before fixing this tooth? It broke when I bit down, unexpectedly, on something hard while eating a soft food. Otherwise, the tooth is healthy.

    Would it make sense to have a filling put on the tooth's broken cusp to buy some time? Or should I go straight to an onlay? Getting this tooth fixed has been much more difficult than I expected and I'm not sure what to do at this point.
     
    noesis, Sep 13, 2018
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  4. noesis

    MattKW Verified Dentist

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    I wouldn't bother putting a filling on it if it's a simple clean fracture with no decay. Just eat normal foods and avoid really hard stuff like pork crackling, seeds, etc.
    It's odd your dentist doesn't offer zirc. It requires less tooth reduction than other methods (excluding gold).
     
    MattKW, Sep 13, 2018
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