Direct Resin Onlay or Crown

This topic contains 39 replies, has 11 voices, and was last updated by  miwezemati August 1, 2018.

Viewing 10 posts - 31 through 40 (of 40 total)
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  • #7713
    Michael Martin
    Michael Martin
    Participant

    Graeme,

     

    I love reading your posts!  Could you send a picture of one of your preps?

     

    Warmly,

     

    Michael

    #7714
    Alex Touchstone
    Alex Touchstone
    Keymaster

    HI All,

     

    I am in the process of re-loading threads from the previous forum and since this is such a hot topic (onlays) and there was great info posted before by Graeme and others, I decided to merge several threads together.  I hope you enjoy and agree with this approach.  Feedback welcome.

     

    Alex

    #7715
    Graeme Milicich
    Graeme Milicich
    Participant

    Michael

    I can’t remember if I have posted this case or not, but is shows the basic contours associated with recreating a compression dome.

    Patient presented with a virgin tooth with a mesio-distal crack developing in the distal half of the tooth, associated with a severe palatal plunger cusp on the opposing tooth.

    The bite paper highlights the strong wedging contacts from the upper plunger cusp. The danger with these vertical fractures is the crack doesn’t transect many dentin tubules so they are more often thatn not quite symptomless until the fracture reaches the pulp and often the crack goes way down the root faces and the tooth is lost. Preemptive intervention is the best course for these teeth.

     

    The crack was dissected to within 1mm of the pulp and a rolled chamfer margin placed right around the occlusal reduction. If you look closely you can also see a trench cut bucco-lingually.

     

    Trench outined in red. Ribbond was bonded bucco-lingualy into the groove. This provides addittional stabilization of the fracture to help prevent it flexing.

     

    Here is a screen shot of the prep to give you a better idea of the margin design. Note, I also ran the “margin” design through buccolingually as well. The basic margin contour puts the underlying dentin back into compression. Whenever there is a lateral load, one of the margins goes into compression and prevents lateral shear loads from building in the bond interface. Note teh angle on teh buccolingual face of the prepe. This exposes the ends of well supported enamel rods. The strongest bond we have got in dentistry.

     

    To further stabilize this restoration, I ran the buccolingual groove. This provides resistance to and forces driving the restoration in a distal direction.  Normally, this would be provided by the mesial and distal margins of a full onlay.  In this case, I deemed it unneccesary to remove the front half of the tooth. There were no occlusal loads present from the opposing occlusion that could begin to generate a force that could damage the front of the tooth.  So WHY cut sound tooth away if you don’t have to? Just engage the other half of our brain instead! Just because we get a frontal lobotomy at Dental School doesn’t mean we have to live with some of the learning that got shoved into the empty space they created. 😮

     

    The red area is the bonded Ribbond strapping.

     

    Completed BONDED e.max onlay. Note how I modified the occlusion (partially by reshaping the upper plunger cusp) and contouring the lower restoration so the primary occlusion is a compressive load on the outside cusp angle of the mesiobuccal cusp. NO splitting forces at work on this tooth any more.

     

    Hope this makes sense. There is no substitute for sound tooth structure! However, conservation has to be done with understanding, otherwise you end up having to deal with the tooth again in the future. Crown preps are dead.

    #7716
    Graeme Milicich
    Graeme Milicich
    Participant

    Are there general guidelines on when to pick onlay vs crown ?

    Yes. Not wanting to sound like a smart A**se.

     

    The guide line I use is Never do a full crown.

     

    Get good at adhesive dentistry and anything you bond into a tooth will stay there as long as you work withing the basic guidelines for adhesive ceramics. If you throw away all your crown cements (and that includes SE cements), your whole perspective changes.

    The more damaged a tooth is, the harder it is to do a full crown anyway because you are really struggling to find a decent ferrule to make cementation work, so you end up over cutting the tooth, doing aggressive crown lengthening etc where all you have to do is create a gentle rolled margin after your 1.5mm occlusal reduction and you are done. Let the lost tooth structure dictate the prep contours, not a text book.

    #7717
    Michael Martin
    Michael Martin
    Participant

    Graeme, That is beautiful!  That is exactly the restoration I want on MY lower second molar!  What is the green material under the ribbond? What are your thoughts on dissecting the crack to within 1mm or the pulp?  Also, aside from the manufactures recommendation, what are your thoughts on material thickness of emax?  In some conversations with Pascal Magne, he’s theorizing that 1mm well bonded and supported may be adequate,  Also, it is my understanding that light yellow in the e4d software shows where the software has added material thickness to total 1mm.  Is that correct?

     

    Warm Regards and Happy Holidays,

     

    Michael

    #7718
    Mike Kelliher
    Mike Kelliher
    Keymaster

    Michael,

    Yes the system will add material to your restoration if it’s thin. One way around this is to tell the software you’re doing a veneer instead of a crown or onlay. Then it’ll mill as thin as .3mm.

    #7719
    Michael Martin
    Michael Martin
    Participant

    Thanks Michael,

     

    Just to clarify, if I design a crown that is 0.8 mm in the central groove area (not that I’ve ever under-reduced), the software will add 0.2 mm and show it in yellow, and mill a restoration with a 1.0 mm minimum thickness in the central groove area.  Do I have that right?

     

    Thanks so much for your help,

     

    Michael

    #7720
    Graeme Milicich
    Graeme Milicich
    Participant

    Graeme, That is beautiful! That is exactly the restoration I want on MY lower second molar! What is the green material under the ribbond? What are your thoughts on dissecting the crack to within 1mm or the pulp? Also, aside from the manufactures recommendation, what are your thoughts on material thickness of emax? In some conversations with Pascal Magne, he’s theorizing that 1mm well bonded and supported may be adequate, Also, it is my understanding that light yellow in the e4d software shows where the software has added material thickness to total 1mm. Is that correct?

    Warm Regards and Happy Holidays,

    Michael

    The green material under the Ribbond is a graphic of the radio-opaque composite I placed into dissected crack t fill it up nearly flush with the groove I cut for the ribbond. Ribbond THM will not hold a radius in contact with the narrow groove, though the new Ribbond THM Ultra might, so I sealed and filled the base of the groove first.

    Cracks make me nervous, particulary the vertical ones. I dissect them in a controlled way. Sometimes they run out, then I am really happy, but by disecting them, I am removing a lot of the contaminants that may be present, and I don’t wnat to seal too much rubbish inside the tooth.

    The basic rule of thumb is the pulp horns are 5mm from the occlusal surface. That accounts for 1.5-2mm of enamel, then 3-4mm of dentin. In this case, all the enamel has been worn away. That leaves 3mm of dentin over the pulp horns. I confirmed this with an Xray.

    I have measured the tooth from the occlusal surface, down to the pulp horns. Click on the Xray image to enlarge it. You will see the red measurement line and its length on the right side of the screen shot.

    The first thing I did when prepping, was to take a fine 1/2round diamond bur and dissect out the fracture using a fine perio probe as a depth guide. If I had done the prep first, I would never have had any idea as to where I was regarding depth.

    Hope this makes sense.

    #7721
    Mike Kelliher
    Mike Kelliher
    Keymaster

    Thanks Michael,

     

    Just to clarify, if I design a crown that is 0.8 mm in the central groove area (not that I’ve ever under-reduced), the software will add 0.2 mm and show it in yellow, and mill a restoration with a 1.0 mm minimum thickness in the central groove area.  Do I have that right?

     

    Thanks so much for your help,

     

    Michael

    Basically that’s it.  If you design less than 1mm it’ll add material unless you set it up as a veneer.  Personally I’m still real hesitant to go thin in the posterior, I like 1.5mm so far that’s served me very well!

    #16281

    miwezemati
    Participant
Viewing 10 posts - 31 through 40 (of 40 total)

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