THREE UNIT ALL CERAMIC PREPARATION

22/09/2021

THREE UNIT ALL CERAMIC PREPARATION

The introduction of stronger and more durable ceramics over the past few years has greatly increased the clinician’s choice of materials when fabricating an all-ceramic three unit bridge. The latest generation of zirconia (Vsmile ST) is suitable for three unit bridges and can restore teeth anywhere in the mouth, and Vsmile Cad Block Glass Ceramic is suitable for anterior teeth.

Suitable Materials for Three Unit All Ceramic Bridges

Options include 41% high translucent (Vsmile ST Zirconia) zirconia for anterior three-unit bridges and layered zirconia. Vsmile ST Zirconia is an extremely strong material suitable for restoring posterior teeth, and it can be an excellent choice when the patient has bruxism or tooth grinding issues.Vsmile B40 Cad Block is a lithium disilicate ceramic that provides exceptional esthetics. It is suitable for three unit anterior bridges.
With all bridge preparations for all-ceramic restorations, incisal and occlusal edges must be rounded. There should be no undercuts, the walls of the preparation must be parallel. The abutment teeth must not diverge or converge, preventing a clear path of insertion. The minimum thickness for the walls of a bridge preparation is 0.5 mm. During tooth preparation, the minimum connector cross-section for an anterior restoration should be 7 mm2, while a posterior restoration should have a connector cross-section of 9 mm2.

 

Three Unit All Ceramic Preparation for Layered Zirconia and ST Zirconia Bridges

Layered and high translucency zirconia bridges can provide the patient with an extremely high quality restoration. The high strength of zirconia means that it handles similarly to PFM restorations. Supragingival margins are acceptable, because of the tooth-colored framework. Zirconia margins make it simple to maintain excellent gingival esthetics, even after these restorations have been in the mouth for a long time.
Ideally, when preparing teeth for a layered or ST Zirconia bridge, ensure that the preparations have a continuous and easily visible chamfer around the entire circumference of the tooth. Avoid bevelling. The vertical and horizontal preparation must have an angle of at least 5 degrees.
When shaping anterior teeth ensure that:
  • The anatomical shape is evenly reduced by between 1 and 1.5 mm.
  • The incisal third of the crown should be reduced by 1.5 mm, and the incisal edge should be reduced by between 1.5 and 2 mm.

When shaping posterior teeth then ensure that:
  • The anatomical shape is evenly reduced by between 1 and 1.5 mm.
  • The occlusal surface should be reduced by between 1.5 and 2 mm.

Three Unit All Ceramic Preparation for Vsmile B40 Cad Block

Vsmile B40 Cad Block is a good material to select when minimal restoration thickness is important. It provides good biocompatibility, high mechanical strength, and optimum translucency.
When preparing teeth for IPS e.max, the following guidelines apply:
  • Tooth preparations should have no sharp angles or edges
  • The shoulder preparation must have rounded inner edges
When shaping anterior teeth ensure that:
  • The anatomical shape is evenly reduced while adhering to the correct minimum thickness required.
  • A shoulder is prepared around the entire circumference of the tooth with a chamfered edge or rounded inner edges and with an angle of approximately 10 to 30 degrees. The overall width of the shoulder or the chamfered edge must be at least 1 mm.
  • The tooth is reduced incisally by at least 1.5 to 2.0 mm. The oral or vestibular area should be reduced by at least 1.5 mm.
  • For successful bonding to, the preparation height should be at least 4 mm and have retentive surfaces.

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