How to complete ceramic-inlay, partial-crown preps with Expert Kit 4562ST [VIDEO]

June 16, 2014
Issue 6

The Expert Kit 4562ST from Komet USA contains three newly developed diamond instruments that incorporate depth markers (indicated by the letter “D” for “depth” in the reference number). These marks indicate the required minimal occlusal thickness for successful all-ceramic restorations, including those fabricated with CAD/CAM techniques.

The Expert Kit 4562ST from Komet USA contains three newly developed diamond instruments that incorporate depth markers (indicated by the letter “D” for “depth” in the reference number). These marks indicate the required minimal occlusal thickness for successful all-ceramic restorations, including those fabricated with CAD/CAM techniques.

The coarse-grit, rounded-edge, tapered 6847KRD.FG.016 diamond features depth markers at 2 and 4 mm. The shorter, rounded-edge, tapered 959KRD.FG.018 and the 845KRD.FG.025 diamonds provide depth marks at 2 and 4 mm and at 2 mm, respectively.

Supplied in a stainless-steel bur block suitable for sterilization, the complete kit also provides six fine-grit diamonds for subsequent finishing as well as a ball-shaped, normal-grit diamond for deepening the cavity beneath the fissure, if necessary.

In this technique video, the use of crown preparation instruments in Expert Kit 4562ST is demonstrated on a model. (The sequence of the illustrated preparation steps can be modified according to personal preferences.)

Step 1

Open the cavity with instrument 6847KRD.FG.016, a coarse-grit, rounded-edge, tapered diamond. The instrument’s depth marks at 2 and 4 mm help guarantee the required minimal thickness of the ceramic beneath the fissure.

Step 2

Use the same instrument to create a proximal box. The proximal enamel wall remains intact for the time being. If necessary, the adjacent tooth can be protected with a steel matrix band.

Step 3

With the thin, flame-shaped, fine-grit instrument (8862.FG.012), remove the proximal enamel. In this step, the enamel wall is removed. Avoid creating a spring edge.

Step 4

To smooth the inner walls and floor of the preparation, employ finishing instrument 8847KR.FG.016, which features a shape that corresponds to the instrument used in step 1.

Step 5

Depending on the size of the cavity, two shorter, rounded-edge tapered instruments can be applied to shape the cavity as necessary:  959KRD.FG.018 (as illustrated), with depth marks at 2 and 4 mm, and 845KRD.FG.025, with a depth mark at 2 mm. (For shaping the interproximal cavity margin, Komet® sonic tips can be employed.)

Step 6

For subsequent finishing, two fine-grit instruments with matching shapes (8959KR.FG.018, as illustrated, and 8845KR.FG.025) can be used. To increase the opening angle in the occlusal direction, the tapered instrument should be tilted in the oro-vestibular direction. 

Step 7

With the thicker, flame-shaped finisher (8862.FG.016), give the edges of the box a concave shape. The instrument should be pulled from an apical to an occlusal direction.  The convex tip of the instrument automatically creates a concave contour in the tooth structure. Enlarge the opening angle in the occlusal direction, taking care to create an open (rather than excessively steep) preparation, and, again, avoid creating a spring edge. The transition between the cavity floor and the box must be rounded.

Step 8

If necessary, use ball-shaped, normal-grit instrument 801.FG.023 to further deepen the cavity beneath the fissure.

Step 9

With tapered instrument 959KRD.FG.018 held in a horizontal position, horizontally shorten the cusps. The instrument’s 1.8-mm diameter (1.4 mm at the tip) ensures sufficient reduction. Instrument 845KRD.FG.025, with its larger 2.5 mm diameter (1.9 mm at the tip), is ideal for creating smooth margins and can be used to form rounded shoulders inside the preparation as needed.

Step 10

Round off all inner edges with fine-grit, egg-shaped instrument 8379.FG.023.

Use the same egg-shaped instrument to slightly round all horizontal outer edges. Round off all edges within the preparation to avoid leaving sharp transitions.

Step 11

With the thin, flame-shaped finisher (8862.FG.012, as shown in Figure 3), round off any remaining corners and edges in hard-to-reach areas as well as any sharp transitions at the contour of the preparation margin. Make sure to avoid creating a spring edge.