Indications and clinical technology of manufacture of artificial crowns

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 bal ance of the extracoronal category 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 bal ance of the extracoronal category

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 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 is named according to the fractional amount of the clinical crown it covers

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

Complete metal crown Complete metal crown

Complete veneered crown

Fig The optimum restoration should satisfy biologic, mechanical, and esthetic requirements.

Fig Damage to adjacent teeth is prevented by making a thin "lip" of enamel as the bur passes through a prox­ imal contact.

Fig Mouth mirror protecting the soft tissues during tooth preparation

Fig 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.

Fig 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.

Fig Excessive taper results in considerable loss of tooth structure (shaded area).

Fig 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

Fig 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.

Fig 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.

Fig 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.

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

Fig The recommended convergence angle is 6 degrees. This is a very slight taper. (The angle between the hands of a clock showing 12:01 is 5 1/2, degrees.)

Internal features effectively increase resistance. Fiji Retention form of an excessively tapered preparation can be increased by adding grooves or pin­ holes, because these will limit the paths of withdrawal.

Fig Recommended tooth preparation for a metal-ceramic restoration. The facial reduction has two distinct planes.