Degradation of zircon

Discussion in 'Digital Materials and Machine Tools' started by cadfan, Jun 24, 2017.

  1. cadfan

    cadfan Moderator Staff Member

    Sorry guys the study is only in German but done on real cemented crowns on metal stumps 1.2 million chewing cycles with temperature change from 5 to 55 deg c always 8 crowns of one material and what do we see no breakage but degradation of the materials especially the high yttrium stabilized like cube x and all the the others ( Katana HTML, UTML, AG Zolid and so on ) would show same results i think

    39 % degradation !!!!!


    3 unit brigde ??? crap preparation ??? thinn margin ??? shit cemented ???? is this a long run burner ??!! with conventional cementation ?? just a few question nothing to fear.
     

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  2. LiQUiD

    LiQUiD New Member

    Excellent info. Thanks for the translation
     
  3. Toothman19

    Toothman19 Well-Known Member

    From the other "forum"

    "He is referring to Low Temperature Degradation (LTD). This was a phenomenon with older (1st gen) zirconias that when exposed to a warm, wet environment they would break down over time.

    Newer zirconias have been developed to reduce this effect. Can it still happen, yes, but is much less likely.

    The other thing to consider is, how long do you consider the the lifespan of a restoration? I believe for insurance purposes it is 5 years. I personally would consider it longer (10 years) depending on the patient's oral hygiene. In these cases the 5-10 gear span would be acceptable anyways. But this is not necessarily the case."

    and "Just about all the HT materials (1100 MPh) loose 50% of their flexural strength over 5 years. That said the new Anterior materials (about 600 MPh) made form Zepex Smile, Tosoh powder loose virtually no strength over time. This is one of the only ceramic materials in our industry that has no degradation or loss of strength over time. lithium disilicate, feldspathic, lucite ceramics all loose strength. Most are in the 30% + range"
     
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  4. cadfan

    cadfan Moderator Staff Member

    What makes a crown breaking ?? a real breaking test and that is was it is ( 2017) just for the other " forum cowboys "
    and they realized at the Uni that there results where opposite than others but real is real. oder wie wir sagen kaputt ist kaputt LTD HTD UFD who cares. 3 point 4 point ... bend


    a small google translate for the important things and they where glued i think every doc makes it !!!???

    The surfaces of the metal stump to be glued and the inside of the crown are roughened, cored, and wetted with universal primer (Monobond Plus, Ivoclar-Vivadent). The crown and stump are then joined together with a dual-curing, adhesive composite cement (Multilinik Automix, Ivoclar-Vivadent) and pressed centrally and axially, evenly onto the stump.Afterwards, 8 test specimens of a material group are placed in a simulator and subjected to a cyclic load (1.2 million chewing cycles) with simultaneous thermal cycling (5 - 55 ° C), which allows the crown to be used for 5 years in the patient's mouth, formulated. The remaining 8 crowns of the same material group are used for comparative measurements without simulated chewing stress.After the chewing stimulus, all 16 specimens of each material series are loaded with a universal testing machine (Zwick Z010, Zwick / Roell) up to the breaking or the force switch-off limit of the testing machine. [4]Results and discussionWithout load in the causal stimulus, the study shows no significant differences in the fracture load of the tested materials. These results are in contradiction with the results of studies by Carrabba et al. (3-point bending test) [5] and by Zhang et al. (4-point bending test) [6] in which it was found that the flexural strength of zirconium-Oxide ceramics significantly decreased with increasing content of yttrium oxide. The reasons for the different results are the different test methods. However, the test method used here and the associated anatomical sample body shape has the advantage that it is much closer to the clinical reality than the above mentioned test methods.
     
  5. cadfan

    cadfan Moderator Staff Member

  6. lucky54

    lucky54 Well-Known Member

    Du meinst wir hätten gut vorgesorgt ????????
    Wenn sie nach 2 Jahren kaputt sind haste wieder ne neue Arbeit aufm Platz mit etwas Glück kannste die alten einfach wieder fräsen und fertigmachen.
    Win win für uns und die Industrie :):):)
     
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