Dental Prosthesis and Crown Classification

Prosthesis

• Definition: An artificial appliance replacing a lost body part (e.g., eye, leg, tooth).
• In dentistry, prostheses can be fixed or removable, complete or partial.

Crown

• Definition: A fixed restoration covering all or part of a tooth's crown.
• Purpose: Restores tooth anatomy, function, and aesthetics.

Classification of Crowns

By Material

• Metal: A crown made of metal.
• Non-metal: A crown made of acrylic or ceramic.
• Ceramo-metallic: A crown combining metal and ceramic (often with a ceramic veneer).

By Coverage

• Full coverage: Entire tooth crown covered. (e.g., full metal, ceramo-metallic)
• Partial coverage: Only part of the crown is covered. (e.g., 3/4, reverse 3/4, 1/2, 7/8, McBoyle crown, pin-ledge crown).

Different types of Crowns

Full Metal Crown

• An artificial crown made entirely of cast metal.
• Covers all coronal structures of posterior teeth.

Ceramic Crown

• A crown made of ceramic.
• Focuses on esthetics and function.

Ceramo-metallic Crown (CM crown) or Porcelain Fused to Metal (PFM)

• Crown with a metal substructure and a ceramic covering.
• Emphasis on aesthetics, anatomy, and function.
• Veneered crown - ceramic covering only the visible part of the crown.
• Full veneered crown - ceramic covering the entire metal substructure, for greater esthetics.

Post Crown

• Artificial crown replacing lost coronal structure.
• Retained by a post in a prepared root canal.
• Aims for aesthetics, function, and anatomy restoration.

Three-quarter Crown

• Partial coverage crown covering two proximal, lingual, or occlusal surfaces.
• Buccal/incisal surfaces remain uncovered.
• Retained by grooves in the tooth structure.
• Universal applicability (can be used in various areas of the mouth).
• Reverse type: Lingual surface left unprepared, labial/buccal surface is prepared.. Common use in lower premolars.

Proximal Half Crown (Mesial Half Crown)

• Partial coverage restoration covering only the mesial, half buccal and half lingual surfaces.
• Portion of the occlusal surface is reduced.
• Retained by grooves or other methods.

Seven-Eighth Crown

• Partial coverage, reducing all the tooth surfaces except for the mesio-buccal cusp, for aesthetic purposes.
• Grooves are present in the proximal and buccal surfaces.

Pin Ledge Crown

• Partial coverage crown.
• Retention is achieved through pins in the palatal surfaces.
• Two incisal and one cervical pinholes usually employed.
• Less common due to complex preparation.

Laminate Veneer

• Partial coverage, thin ceramic material cemented to the labial surface of anterior teeth.
• For improved aesthetics.

Occlusal Veneer

• Partial coverage, thin ceramic material on occlusal surfaces of posterior teeth.
• Aims to replace lost anatomy and increase vertical dimension of occlusion.

Other Restorations

• Onlay: A dental restoration covering the occlusal surface.
• Overlay: Covers the occlusal plus mid-buccal and mid-lingual surfaces.
• Endocrown: A ceramic restoration for endodontically treated teeth, gaining retention from the pulp chamber.
• Fixed Partial Denture (FPD, bridge): A partial denture cemented to natural teeth, tooth roots, or implants to replace missing teeth.

FPD Classification

• Material: Metal, non-metal (acrylic/ceramic), or combination (ceramo-metallic).
• Site: Anterior (canine to canine), posterior (premolars or molars), or complex (crossing the canine).
• Retention: Simple (fixed-fixed, fixed-support, fixed-free) or compound (using multiple methods).

Other restorations

• Resin bonded FPD: uses intra-oral restorations for retention (e.g., inlays). Metal or ceramic wings are sometimes found on anterior teeth (e.g., Maryland bridge).
• Fixed-Removable partial dentures: Restorations have a fixed part attached to abutments and a removable part for the patient.