Tooth Preparation To Receive All Ceramic Crown Notes

Tooth Preparation To Receive All Ceramic Crown Introduction

All ceramic crowns are considered an esthetic option for anterior restoration. The preparation to receive all-ceramic crowns needs more amount of tooth reduction compared to other available options. This chapter describes stepwise tooth preparation to receive all ceramic crown restoration.

Tooth Preparation

The stepwise preparation of the maxillary central incisor to receive all-ceramic crowns is given here.

Incisal Reduction:

Depth of preparation (amount of tooth preparation): 2 mm.

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Instrument: Flat-end tapering diamond. Place depths-orienting grooves or depth cuts on the incisal edge. Place three cuts on the incisal edge, one on the mid-incisal region, and one each at the junction of each proximal surface. Remove the remaining tooth structure from the incisal edge using a small wheel diamond or flat-end tapering diamond.

Read and Learn  More: Preclinical Prosthodontics Notes

Labial Reduction:

Depth of preparation (amount of tooth preparation): 1.5 mm.

Instrument: Flat-end tapering diamond. The labial surface of the incisor can be divided into two planes. These are located at different angulations thus the labial surface is prepared in two planes.

Prepare the labial surface of the maxillary incisor in two planes. Place the depth orientation grooves by sinking flat-end tapering diamond up to 1.2 mm which after finishing will produce a depth of 1.5 mm. Place the depth-orienting grooves in two planes.

One set is within the gingival half and it is parallel to the gingival half of the labial surface. The other set is placed in the incisal half. Remove the remaining tooth structure between the depth grooves using the flat-end tapering diamond. Extend the preparation to the facioproximal line angle.

Follow gingival contour during tooth preparation. This will prevent trauma to interdental papillae and limit the preparation in the gingival sulcus. A shoulder finish line is produced by flattened tapered diamonds. The shoulder finish line can be placed subgingival (recommended for anterior teeth) or subgingival.

Lingual Reduction:

Lingual reduction is done in two parts. Axial reduction is done first and then tooth reduction is done from the lingual fossa.

Lingual Axial Reduction:

Depth of preparation (amount of tooth preparation): 1.5 mm.

Instrument:

Flat-end tapering diamond. The lingual axial reduction will prepare a cervical portion of the lingual surface of the tooth. This surface should be given a taper of 3–5° with the cervical part of the labial surface. Place flat end taper diamond straight against this surface and prepare the tooth.

Due to the taper configuration of the bur, the surface will be prepared in a tapered style. Maintain the position of the bur and extend tooth preparation till linguoproximal line angle. A shoulder finish line is recommended for the lingual surface.

Lingual Fossa Reduction:

Depth of preparation (amount of tooth preparation): 1.5 mm.

Instrument: Number 6 round bur and wheel diamond or football diamond. Place depth cut in the form of potholes in the lingual fossa with a number 6 round bur. The diameter of the round bur should be 1.8 mm which produces depth cuts of approximately 1–1.2 mm after finishing it gives the required depth of preparation. The remaining tooth structure is removed with a small wheel diamond or football diamond.

Proximal Reduction:

Depth of preparation (amount of tooth preparation): 1.5 mm.

Instrument: Long thin tapering diamond and flat-end tapering diamond. A long thin tapering diamond is used to prepare the proximal tooth surface. The access is prepared using a vertical sawing motion. The diamond should follow incisogingival direction.

This motion will cut the tooth surface proximally. The cut is through the proximal enamel and produces the enamel lip.

Remove the enamel lip by any hand instrument or by diamond point. Use flat-end tapering diamond to join facial and lingual preparation through the proximal area. This produces a proximal surface with taper of 3–5°. Produce smooth shoulder in the proximal area following the gingival contour. Prepared tooth to receive all ceramic crowns.

Finishing Of Preparation

Make all the point and line angles rounded to prevent stress concentration and fracture. The axial surface can be finished with a yellow collar fine grit diamond. The shoulder can

be finished with end cutting diamond where only the tip has fine diamonds and the sides are noncutting. See the shoulder finish line on the labial side, proximal side, and lingual side.