FAQs

Your questions – Our answers

Zirconia: General

priti ® multidisc ZrO 2 / priti ® multibloc ZrO 2

 

  • What's in zirconia?
    • Zirconium dioxide is made from the mineral zircon (ZrSiO 4 ). The terms zircon and zirconium oxide are not correct as the structure ZrO 2 . Zircon stands for the mineral zirconium silicate (ZrSiO 4 ), which serves as a natural raw material for structural ceramics .
      The correct name for ZrO 2 is: zirconium dioxide.

      Additives are added to the starting powder:

      • Auxiliaries (water, organic compounds) facilitate shaping into blanks and evaporate during pre-sintering.
      • Sintering additives remain in the material and influence the sintering behavior and the properties of the finished ceramic.
      • Zirconium dioxide from pritidenta contains hafnium oxide, yttrium oxide and aluminum oxide.

  • Does zirconia age?
    • All scaffolding materials age, including metals. Partially stabilized zirconium dioxide (opaque / translucent) has good aging resistance: even after a long period of wear, the strength does not fall below the 800 MPa required by DIN EN ISO 6872. Highly and extra translucent, fully stabilized zirconium dioxide has a very good aging resistance: In scientific studies, no loss of strength was found even after a long period of wear.

  • Is zirconia radioactive?
    • Everything is radioactive, including the human body (6,000 Bq). A zirconium dioxide crown has about 0.4 Bq, a VMK crown up to 2 Bq. The ceramic dental standard DIN EN ISO 6872 specifies upper limits; Evidence of compliance is included in the technical documentation.

  • Can I derive its abrasiveness from the bending strength of a material?
    • No, hardness and surface quality are decisive. Ideally, therefore, monolithic, fully anatomical restorations made of zirconium dioxide should be polished – especially the areas with contact with antagonists – and additionally glazed. We recommend the use of lithium silicate spray (eg CeraFusion) for the glaze on the polished surfaces.

  • What is chipping?
    • Chipping stands for flaking of the veneering ceramic, which can be caused by the following circumstances:

      • sharp edges of the scaffolding material
      • strong blasting (= high jet pressure) of the outer and inner surfaces
      • Failure to comply with the specified heating and cooling phases in the sintering process and in the veneering process
      • Tensile stress in the veneer layer (due to different layer thicknesses)
      • Scaffolding design does not follow a reduced, anatomical shape (= cusp support)
      • Too thick veneer layer (1.5 mm> thickness)
      • Falling below the minimum scaffold wall thickness (<0.4mm)
      • Excessive or intraoral grinding of the final sintered restoration is too strong
      • Contraindicated editing
      • Different thermal expansion behavior (CTE) between framework and veneering ceramics

      Colloquially, chipping is sometimes also used for fractures.

  • What is important for a good fit?
    • Various factors interact here

      • Perfect working basis on the model (preparatory work in the dental practice)
      • Precise scan data
      • CAD parameters for crown design (spacer, edge course, …)
      • CAM system settings
      • Diameter and quality of the processing tools
      • Sintering process (firing program, storage on pearls / occlusal pins …)
      • Always follow the manufacturer’s processing instructions!

  • What happens when sintering?
    • Sintering involves heating fine-grained ceramic or metallic materials – often under increased pressure. In order for the workpiece to keep its shape, the temperatures remain below the melting point of the main component.

      As a rule, shrinkage occurs because the particles of the starting material become denser due to diffusion processes and a reduction in the specific surface area, and pore spaces are filled. Each bridge from approx. 4 links should be stabilized during sintering with an individual cross connector that is adapted to the material mass. Occlusal sintered supports ensure uniform horizontal and vertical material contraction.

      Sintering gives the material its (almost) maximum density and thus its properties specified for dentures.

  • After sintering, the color / translucency is not correct - why is that?
    • If all parameters of the sintering process are correct, the following reasons for an undesirable change in color / translucency are possible:

      • Contamination in the oven with foreign materials, e.g. residues of coloring liquids> Carry out cleaning firing with cleaning powder, replace sintered beads.
      • Cross-contamination from contaminated milling cutters> When manually reworking, do not use tools that have already been used for metals, plastics or other materials.
      • Contamination from coolant / grinding additives> When grinding priti ® multibloc ZrO 2 with wet water, clean the tank beforehand, use a second tank if necessary.
      • Varying wall thicknesses> Especially with very translucent zirconium dioxide, the wall thickness has a great influence on the color effect; the thicker the material, the darker or more intense the color.
      • Different stump colors> For heavily discolored stumps, an opaque material should be chosen. This can even be used on metallic constructions without a colored cover, with more translucent materials an opaque or opaque fastening material is required.
      • Additional coloring> Pre-colored zirconium dioxide can theoretically also be treated with coloring liquids, it is better to carry out further characterization with glaze paints.

  • How do I get natural fluorescence?
    • A natural, patient-specific fluorescence is best achieved using fluorescent glaze or veneering materials. The addition of fluorescent additives in zirconium oxide, on the other hand, leads to a significant reduction in translucency, on the other hand, the intensity of natural fluorescence from teeth cannot be achieved.

  • What kind of multicolor priti ® multidisc ZrO 2 / priti ® multibloc ZrO 2 blanks are there?
    • priti ® multidisc ZrO 2 multicolor is available in the three translucency levels High Translucent (HT), Extra Translucent (ET) and Translucent (T) – each in 7 or 8 shade categories, with which all VITA shades can be reproduced.

      priti ® multibloc ZrO 2 multicolor is available in the translucency level High Translucent (HT) – in 3 shade categories with which the VITA classical A1-B2 shades can be reproducibly produced.

  • Which translucency levels are suitable for which indications?
    • High Translucent (HT): inlays, onlays, veneers, partial crowns, anatomically reduced and monolithically fully anatomical crowns and bridges (max. 3 units) for the anterior and posterior teeth area

      Extra Translucent (ET) / Translucent (T): partial crowns, monolithic fully anatomical and partially or fully veneered crowns and bridges (up to 16 units) as well as individual abutments for the anterior and posterior region on natural dental posts and implants

      Opaque (O): partially or fully veneered crowns and bridges (up to 16 units) as well as individual abutments for the Anterior and posterior areas on natural tooth abutments and implants

  • What do the color categories mean for the multichromatic priti ® multidisc ZrO 2 blanks?
    • Each color category stands for a specific color range, which is covered by the color gradient integrated in the blank. Depending on the positioning of the construction on the course, i.e. further up or down in the blank, the basic tone of the restoration is lighter or darker.

      pritidenta color Category VITA classical A1-D4 shades VITA System 3D-Master®
      A light A1 – A3 2M1, 1M2, 2R1.5, 2M2, 3M2
      A dark A3.5 – A4 3R2.5, 5M3, 4L2.5
      B light B1 – B2 2L1.5
      B dark B3 – B4 3L2.5, 3M3
      C light C1 – C2 3M1, 3L1.5
      C dark C3 – C4 4L1, 5M1, 5M2
      D light D2 – D4 4R1.5, 4R2.5, 3R1.5, 4M1, 4M2, 4M3
      priti bleach 0M1, 0M2, 0M3, 1M1

  • Are there any tools to find the right color category or position in the gradient?
    • priti ® MPguide ZrO 2 High Translucent and priti ® MPguide ZrO 2 Extra Translucent are shade guides for determining the tooth shade according to the pritidenta shade categories. The color swatches are simply compared with the patient’s tooth; the color category and the required position in the round (top / middle / bottom) are given for each pattern.
      The software MPT – Multicolor Positioning Tool offers a simulation of the color effect after sintering. The design can be moved within the virtual blank and the software shows how the finished restoration would look in color depending on the position.

  • Are there any restrictions to be observed when constructing bridges?
    • The materials priti ® multidisc ZrO 2 monochrome and multicolor in the translucency levels Opaque, Translucent and Extra Translucent are class 5 dental ceramics with a bending strength of well over 800 MPa. In accordance with DIN EN ISO 6872, they are therefore suitable for monolithic bridges and facing bridges with four or more elements. There is no limit to the span and distribution of the bridge piers; the static and physiological load limits must always be taken into account. pritidenta recommends:

      • Max. a terminal bridge link
      • Max. two pontics in the posterior region
      • Adjustment of wall thicknesses and connector cross-sections for extreme spans

  • How do I properly clamp the priti ® multibloc ZrO 2 in the machine block holder?
    • The block holder is inserted straight and lengthwise via the locking device into the block holder of the machine, then the grub screw can be tightened with a torque wrench – with Dentsply Sirona systems it audibly engages. For a correct fit, the block should only be fixed at the front with your finger when fastening.

  • I do not use a Dentsply Sirona system - do I have to pay attention to something specific?
      • The block holder is in the middle on the horizontal plane, but slightly offset on the vertical plane; this may have to be compensated in the CAM software.
      • The color gradient from light to dark leads from top to bottom in the block; the block top can be recognized by the print. Possibly. the alignment of the block in the machine block holder must be adjusted to the alignment in the CAM software.

  • Can I edit priti ® multidisc ZrO 2 with high speed templates?
    • Opaque materials are more suitable for this than more translucent materials. Our zirconium dioxide is very edge-stable, but breakouts can be expected at extremely high processing speeds. Good results are achieved with the following settings:

      processing step Roughing the
      occlusal / cavity
      Roughing / finishing
      occlusal / cavity + residual material
      processing tool Roughing Roughing / router
      Parameter:
      Speed ​​(n) 19,000-23,000 rpm 23,000-27,000 rpm
      Feed rate (Vf) 1,200-1,500 mm / min 800-1,200 mm / min
      oversize 0.15 mm 0.15 mm
      stepover 1.00 mm 0.20 mm
      delivery 1.00 mm 0.50 mm

  • What is the best way to remove adhering zirconia dust?
    • After the CAM process: cleaning / removal by suction (clean brush / none
      Compressed air to avoid contamination by foreign particles)
      After sintering: cleaning / removal by blasting (50 µ corundum material, max. 1 bar
      Pressure, 10 mm distance, 5 sec beam time / unit)

  • Which stove do I need?
    • Any programmable, open furnace that is suitable for high-temperature sintering (up to
      1,600 ° C).

  • At what temperature is priti®multidisc ZrO2 / priti®multibloc ZrO2 sintered?
    • Option 1: Standard sintering at 1,450 ° C (heating and cooling rate of 10 ° C / min, holding time 2 h)
      Option 2: Fast sintering at 1,500 ° C (heating rate of 10 ° C / min, cooling rate of 40 ° C / min, holding time 30 min)

      Single tooth restorations and a maximum of 3-unit bridges can be sintered together. In order to avoid tension within bridge restorations, long-term cooling to 400 ° C should be carried out and the material should then slowly cool further on the firing tray.

      Attention: Ceramics generally have a low thermal conductivity – if the workpiece cools too quickly, tensions arise in the workpiece, which can later lead to cracks and cracks in the veneer layer or in the framework.

  • Do I have to pay attention to something specific when sintering very massive constructions?
    • It is important to cool the framework and veneering ceramics evenly and to provide stable, balanced support for the restoration during sintering. Firing trays / pens should be metal-free. The following firing parameters are recommended:

      Execution type Heating / cooling rate Long-term cooling of all firing cycles Furnace removal workpiece
      fully anatomical reduced necessary (400 ° C – 200 ° C) 100 ° C
      Partly anatomical / framework reduced necessary (400 ° C – 200 ° C) 100 ° C

      After each veneer and glaze firing:
      1. Carefully remove the firing tray from the firing chamber
      2. Place the firing tray on a fireproof surface, protected from strong temperature fluctuations (e.g. drafts)
      3. Complete cooling of the restoration to room temperature (approx. 20 min. depending on size and volume)

  • Can I sandblast ZrO2?
    • Yes> 50 µ corundum blasting material, max. 1 bar pressure, 10 mm distance, 5 seconds blasting time / unit.

  • What is the best way to process end-sintered ZrO2?
    • We recommend diamond-coated grinding tools and water cooling. Alternatively, there are zirconia grinders from various manufacturers that work without cooling. As far as possible, shape-specific changes should be made before sintering.

  • What is the best way to fix restorations?
    • Phosphate cement or glass ionomer cement can be used. Alternatively, (self-) adhesive attachment is possible. Tooth-colored fastening materials are recommended for translucent materials. Temporary fastening is not recommended.

      If the restorations are tried on in any form on the patient, the inner surfaces / cavities should be blasted again with 50 μm corundum material, max. 1 bar pressure, approx. 10 mm distance and approx. 5 sec blasting time / unit to avoid contamination of the surface and thus to guarantee a maximum adhesive bond with the fastening material.