Indications and clinical technology of manufacture of artificial crowns

1. Indications and clinical technology of manufacture of artificial crowns

2. An artificial crown is a fixed prosthetic restoration that covers more than half of the coronal portions of the tooth. There are several types of crowns. They may be made  of  gold,  porcelain,  acrylic,  or  a  combination  of these   materials.   Along   with   onlays,   which   are classified as extracoronal restorations, are the various kinds  of  crowns  that  make  up  the  balance  of  the extracoronal  category

3. Partial Crown • A partial crown is a cast restoration made entirely from metal and covers more than half but not all of the tooth's  clinical  crown.  A  partial  crown   • is  named according   to   the   fractional   amount   of   the   clinical crown it covers

4. Complete Crown • A complete crown covers the entire anatomy of a tooth’s   clinical   crown.   There   are   several   types   of complete  crowns

5.  Complete  metal  crown

6. Complete  veneered  crown

7. Fig. 2-1. The optimum restoration should satisfy biologic, mechanical, and esthetic requirements.

8. Fig. 2-2. Damage to adjacent teeth is prevented by making a thin "lip" of enamel as the bur passes through a prox­imal contact.

9. Fig. 2-3. Mouth mirror protecting the soft tissues during tooth preparation

10. Fig. 2- 4. a considerable amount of care is needed when preparing a tooth for a complete crown because of the ex­tensive nature of the reduction, with many dentinal tubules sectioned. Each tubule communicates directly with the dental pulp.

12. Fig. 2-5. Conservation of tooth structure by using partial-coverage restorations. In this case, they are used as FPD abutments to replace con-genitally missing lateral incisors.

13. Fig. 2-6. Excessive taper results in considerable loss of tooth structure (shaded area).

14. Fig. 2-7. An anatomically prepared occlusal surface re­sults in adequate clearance without excessive tooth reduc­tion. A flat occlusal preparation will result in either (1) in­sufficient clearance or (2) an excessive amount of reduction

16. Fig. 2-9. Examples where subgingival margins are indicated. A, To include an existing restoration. B, To extend apical to the proximal contact (adequate proximal clearance). C and D, To hide the metal collar of metal-ceramic crowns.

17. Fig. 2-10. A and B, Poor preparation design, leading to increased margin length. C, A rough, irregular margin will make the fabrication of an accurately fitted restoration almost impossible. D, An accurately fitting margin is possible only if it is prepared smoothly.

18. Fig. 2-11. Precise control of the orientation of the diamond is very important. A, Tilting away from the tooth creates an undercut. B, Tilting toward the tooth results in excessive convergence.

19. All unsupported enamel must be removed. Fig. 2-12. A chamfer should not be wider than half the bur used to form it. Otherwise, a lip of unsupported enamel will be left.