PFM Crowns: Advantages And Disadvantages

The rapid development of technology and dentistry in recent years has led to the emergence of many new materials, such as ceramics and zirconia. These materials have gradually gained popularity due to their unique advantages. However, traditional products like PFM crowns are preferred due to their exceptional durability, aesthetic appeal, and cost-effectiveness. Once considered the gold standard in dental crowns, PFM crowns offer a comprehensive restoration solution with proven reliability backed by clinical research.

In today’s blog, we will explore the advantages, disadvantages, and preparation process of PFM crowns to gain a deeper understanding of this traditional yet highly versatile restoration option.

What Is PFM Crown?

A PFM crown (Porcelain-Fused-to-Metal crown) is a common type of dental crown consisting of two main layers: a metal framework made from metal alloys such as nickel-chromium, cobalt-chromium, or precious alloys like gold and palladium, and an outer porcelain coating. This combination gives them durability comparable to pure metal crowns but with significantly improved aesthetics. As a result, PFM crowns were the most popular type of dental crown for a long time and are still widely used today.

Advantages And Disadvantages Of PFM Crown

Advantages

• Durability and Strength: The metal base provides sturdiness and stability, making PFM crowns suitable for molar positions or for patients with bruxism (teeth grinding). The metal foundation ensures they are more robust and stable compared to all-ceramic crowns, making them ideal for withstanding chewing pressure and years of wear and tear. With proper care, PFM crowns can last up to 15 years, offering a reliable and long-lasting restorative option.
• Cost-Effective: PFM crowns are more affordable compared to other all-ceramic crowns (such as Emax or Zirconia) while still providing comparable aesthetic benefits. This makes them an excellent option for patients with budget constraints.
• Aesthetics: The porcelain outer layer has a natural color similar to real teeth, making PFM crowns more aesthetically pleasing compared to metal crowns.

Disadvantages

• Dark Margin: Although PFM crowns have a porcelain outer layer, their base is still made of metal. Typically, this margin is hidden beneath the gumline, but if gum recession occurs, the dark margin can become exposed, resulting in a less aesthetic appearance.
• Metal Allergies: The base of PFM crowns is made of metal, making them unsuitable for individuals with metal allergies or sensitivities.
• Removal of Significant Natural Tooth Structure: The preparation process for PFM crowns requires the removal of a larger amount of natural enamel compared to other types of all-ceramic crowns.

Preparing For PFM Crown

Preparing Anterior Teeth For PFM Crown

When preparing an anterior tooth for a PFM crown, aesthetics are prioritized above functionality. To achieve desirable aesthetics, sufficient space must be created for the PFM crown restoration.

• The labial surface of the anterior tooth should be reduced by at least 1.2 mm, with 1.5 mm being the preferred size for optimal results. Using a rotary instrument, lingual surfaces are reduced by 1 mm and incisally by 2 mm. To successfully prepare the labial surface, a central cervical groove should be made parallel to the path of placement along the long axis of the tooth. Two other secondary grooves are made on either side.
• Incisal edge reduction grooves are placed, and these must be approximately 1.8 mm deep. The depth of these grooves can be verified using a periodontal probe; they then should extend halfway down the labial surface. Next, the incisal edge is reduced, and proximal contact is broken while maintaining a lip of enamel that protects the adjacent tooth from damage. Ideally, the incisal edge on an anterior tooth should be reduced by 2 mm. This will allow for adequate material thickness, enabling the ceramist to create a crown with good incisal translucency.
• The proximal contacts are reduced, and a 0.5-mm lingual chamfer is created. The tooth structure between the depth grooves is removed, creating a cervical shoulder that should be approximately 1 mm wide. It should extend into the proximal embrasures. The easiest way to shape the lingual surface of an anterior tooth is using a football-shaped diamond. Generally, a single guiding groove is placed in the central lingual surface for anterior teeth.

Preparing Posterior Teeth For PFM Crown

In contrast with anterior teeth, the posterior teeth are focused less on aesthetics and more on strength and functionality. Although all PFM crowns should be prepared with longevity and stability in mind, durability is vital for posterior teeth. Since these teeth do most of the chewing, careful preparation is necessary. Durability is even more important for patients with bruxism.

• When preparing posterior teeth for PFM crowns, depth holes are created in the occlusal surface to facilitate the creation of occlusal depth cuts. Once these depth cuts have been completed, the occlusion can be reduced, and a lingual chamfer and a buccal shoulder are created. The buccal shoulder preparation should extend at least 1mm lingually to the proximal contact.
• The preparation should extend slightly further mesially than distally, as it is more visible. The occlusal surfaces of posterior teeth generally require 1.5 to 2 mm of clearance. Occlusal reduction may be less if the crown is fabricated with a metal occlusal surface or a metal bite stop.
• All margins should be distinct and continuous circumferentially. All other angles must be rounded, and the finished preparation should not have any noticeable burn marks.
• Areas frequently missed during finishing include the incisal edges of anterior preparations and the transition from axial wall to occlusal in posterior preparations. Margins should be finished with diamonds or with hand instruments.

Conclusion

In summary, PFM crowns are an excellent choice for restoring teeth that are lost or damaged due to decay or injury. They combine the strength and durability of metal with the aesthetics of porcelain in a single restoration, offering superior durability and longevity compared to other types of dental restorations. Additionally, they are biologically compatible with the gums and surrounding bone structure, providing a natural look and feel thanks to the porcelain layer on top.

PFM crowns are flexible enough to be used in various situations depending on your needs and are more cost-effective than other options like full porcelain crowns or gold crowns. If you have any questions or simply want to learn more about this type of dental crown, do not hesitate to contact us for answers and to enjoy exciting offers today!