Tooth Preparation To Receive All Metal Crown Notes

Tooth Preparation To Receive All Metal Crown Introduction

The preparation to receive an all-metal crown needs less amount of tooth reduction. This chapter describes stepwise tooth preparation to receive all-metal crown restoration on the mandibular molar.

Tooth Preparation

The stepwise preparation of the maxillary central incisor to receive a porcelain fused metal (PFM) crown is given here.

Occlusal Reduction:

Depth of preparation (amount of tooth preparation): 1 mm on the nonfunctional cusp and 1.5 mm on the functional cusp.

Instrument: Round-end tapering diamond. Depth-orienting grooves or depth cuts of 1 mm are placed on the occlusal grooves. Round diamond or bur of 2 mm diameter can also be used for placing depth cuts on the occlusal surface. Place depth cuts on triangular ridges from cusp tip to base. Remove tooth structure between the depth cuts. Follow the contour and anatomy during tooth preparation.

Read and Learn  More: Preclinical Prosthodontics Notes

Axial Reduction: Buccal and Lingual Preparation:

Depth of preparation (amount of tooth preparation): 0.8–1 mm on the buccal surface. On the cervical one-third, the preparation depth is 0.5 mm.

Instrument: Round-end tapering diamond. The buccal surface of the mandibular molar is prepared in two planes. The depth orienting grooves are placed by sinking round-end tapering diamond up to half thickness (if the diameter of the bur is 2 mm, then it will place depth orientation grooves of 1 mm

by sinking the bur by half thickness). The depth-orienting grooves are placed in two planes. One is within the gingival half and it is parallel to the gingival half of the axial surface. The other is placed in the occlusal half. The remaining tooth structure between the depth grooves is then removed using the round-end tapering diamond. Extend the preparation proximally 1 mm beyond the contact point Follow the gingival contour during tooth preparation. This will prevent trauma to interdental papillae.

Preparing the buccal surface with a rounded tapering diamond produces a necessary taper of 3–5°.

Proximal Reduction:

Depth of preparation (amount of tooth preparation): 0.8–1 mm.

Instrument: Long thin tapering diamond and round-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 with any hand instrument or by diamond point.

Use a round-end tapering diamond to join facial and lingual preparation through the proximal area. This produces a proximal surface with a taper of 3–5°. Produce smooth chamfer in the proximal area following the gingival contour.

Functional Cusp Bevel:

A functional cusp bevel is prepared at 45° to the axial surface. This is prepared to give extra bulk of material on the functional cusp to prevent fracture of restoration and to increase structural durability. The functional cusp bevel is given by a round-end tapering diamond placed at 45° to functional cusps.

Finishing Of Preparation

Make all the point and line angles rounded. The axial surface can be finished with torpedo fine-grit diamond.