How Komet USA’s Expert Kit 4573ST yields precise preparations for all-ceramic lateral crowns [VIDEO]

The Komet® Expert Kit 4573ST focuses on crown preparations with special attention directed toward the specific requirements of all-ceramic crowns produced through CAD/CAM or conventional techniques.

Available with coarse-grit diamonds, the key instrument (6856.FG.021) in the Expert Kit 4573ST features a tapered, round configuration. It is adapted for preparing a distinct chamfer with rounded interior angles.

Sinking the instrument up to half of its diameter into the tooth creates a distinct chamfer with a 0.8-mm radius, which assures sufficient substance removal and rounded interior angles. Both of these characteristics are among the primary requirements for a successful ceramic-crown preparation. The large radius prevents a lip preparation, and the large diameter (021) yields smooth surfaces without grooves or scratches, particularly during finishing.

Because the optimal amount of substance removal to assure sufficient material thickness ranges between 1.0 and 1.5 mm, the kit includes instruments in two diameter sizes: 021 for larger teeth and 018 for smaller teeth. The instrument features a 2° cone angle, which allows the creation of a 4° total angle in case of a circular preparation, without the need to swivel the instrument.

In addition to the 6856.FG.021 diamond and the 6856.FG.018 diamond, the Expert Kit 4573ST contains the coarse-grit, smaller diameter 6856.FG.012 diamond as well as the 6837KR.FG.012 coarse-grit diamond for initial, precise shoulder creation; the 6836KR.FG.014 coarse-grit instrument for incisal-aspect reduction; and the 6379.FG.023 coarse-grit diamond for reduction of the palatal aspect. Other instruments in the kit include three fine-grit, finishing diamonds to successfully define the final preparation limit.

The instruments in the Expert Kit 4573ST are conveniently organized in a Komet® stainless-steel bur block suitable for sterilization.

Lateral-Crown Preparations with Expert Kit 4573ST*

1. With instrument 6837KR.FG.012, prepare a 1-mm uniform shoulder approximately 0.5-1 mm above the future preparation limit.

2. Use instrument 6856.FG.012 to create an interdental separation and prepare a thin, proximal temporary enamel wall. Protect the adjacent tooth with steel matrix as necessary.

3. After creating an interdental separation, use diamond instrument 6837KR.FG.012 (as in step 1) for initial shoulder preparation. Hold the instrument in a vertical position to allow parallel substance removal (Figure 3).

4. Figure 4 displays the occlusal view with a 1-mm circumferential shoulder that corresponds to the anatomical contour of the root.

5. Using instrument 6836KR.FG.014, reduce the occlusal surface. To easily achieve a minimum 1.4 mm substance removal, introduce the instrument completely into the occlusal surface. An occlusal substance removal of up to 2 mm is possible.

6. With the occlusal reduction, make certain to prepare simplified replicas of the anatomic cusps. To create cusp replicas, apply instrument 6836KR.FG.014 (as in step 5) to the molars and premolars from four different directions.

7. Place a retraction cord to protect the gingiva after completion of the initial preparation.

8. For final shaping of the preparation limit to achieve a chamfer with a 0.8 mm radius, use (larger) instrument 6856.FG.021 to simplify access to oral and vestibular areas. Take care to avoid damage to adjacent teeth when applying this instrument.

9. If adjacent teeth require no preparation, use the thinner instrument (6856.FG.018) to create the chamfer in the interdental areas. Define the final preparation limit with the finishing instruments of matching shapes-for example, instruments 8856.FG.018 and 8856.FG.021.

10. If sufficient interdental space is present, the finishing instruments described in the previous step can be employed. Again, avoid damaging adjacent teeth.

11. Check the completed preparation for sufficient interocclusal clearance. With all-ceramic restorations, all sharp edges and corners must be rounded off. Komet® flexible polishing discs are especially suitable for this purpose.

* The use of crown preparation instruments in Expert Kit 4573ST is demonstrated on a model. The sequence of the illustrated preparation steps can be modified according to personal preferences.