Dental Materials · MU Sofia

40. Porcelain fused to metal

Explains porcelain fused to metal restorations, from the layered structure of a metal frame covered by opaque, dentin, enamel and glaze porcelain to the alloy requirements. It covers noble and base alloy types, a table comparing mechanical, van der Waals and ionic-covalent bonding between metal and porcelain, and the firing steps. It then lists possible problems such as cracking, green porcelain from silver, and gum staining, followed by advantages and limits.

Inside: 7 sections · 2 labelled pictures · 1 table · 12 flashcards · 2 min

Topic 40 of 52 in the MU Sofia syllabus for Dental Materials (Dental Medicine, Year 1). The free AceMed note covers it in 7 sections, about 258 words (2 min of reading), with 12 flashcards.

In this note

  1. Introduction
  2. Structure
  3. Requirements for the alloy
  4. The bond between metal and porcelain
  5. Making one
  6. Possible problems
  7. Advantages and limits

Introduction

A metal ceramic restoration, or porcelain fused to metal (PFM), combines the strength of a metal frame with the esthetics of feldspar porcelain. It is one of the most widely used constructions in modern prosthetics.

Structure

The metal frame is strong and tough. Low-fusing or very low-fusing porcelain goes over it in opaque, dentin, enamel and glaze layers, which create the shape and optical properties of the tooth.

Requirements for the alloy

Noble alloys used include gold-platinum, gold-palladium, palladium-silver and palladium. Base alloys include nickel-chromium, cobalt-chromium and titanium.

The bond between metal and porcelain

The chemical bond through the oxide layer holds a metal ceramic together. Too little oxide gives a poor bond, so the layer must be thin and tightly bound.

Making one

  1. Model the frame in wax, cast it in the alloy, and finish it.
  2. Prepare the surface, for example by sandblasting.
  3. Apply and fire the opaque, which hides the metal and bonds to it.
  4. Build up the dentin and enamel layers, then fire them.
  5. Shape, correct and refire if needed.
  6. Glaze the surface.

Continue reading free

The whole note, all 7 sections, is free with an AceMed account, with its 12 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note