D.848.023.FG

Frank Dental Tapered Shoulder Crown Preparation Bur 2.3mm at the widest part of the bur (Where the diamond meets the shank) 1.2mm at the narrowest part of the bur (Tip/Head).

Why a 90-Degree Shoulder Margin is Ideal for Porcelain Fused to Metal (PFM) Crowns

One of the primary reasons dentists use the Frank Dental D.848 Tapered Shoulder Diamond Bur is to create a precise 90-degree shoulder margin for porcelain fused to metal (PFM) crown preparations.

Although modern dentistry offers a wide range of restorative materials, PFM crowns remain one of the most predictable and widely prescribed restorations due to their combination of strength, longevity and aesthetics. However, to achieve optimum clinical results, a PFM crown requires sufficient space for both the metal substructure and the porcelain veneering material. This is where a true shoulder preparation becomes particularly important.

A porcelain fused to metal crown is made up of multiple layers:

• Internal metal coping
• Opaque porcelain layer
• Dentine porcelain
• Enamel porcelain

Together these layers require significantly more space than a traditional full metal crown. If insufficient tooth reduction is performed, the dental technician must either reduce the thickness of the porcelain or create an over-contoured restoration.

Thin porcelain is more susceptible to:

• Chipping
• Cracking
• Fracture
• Wear
• Aesthetic compromise

Over-contoured crowns can result in:

• Plaque accumulation
• Gingival inflammation
• Poor emergence profiles
• Difficult oral hygiene maintenance
• Unnatural appearance

The Frank Dental D.848 Tapered Shoulder Bur creates a true 90-degree shoulder margin that provides the space necessary for both the metal coping and porcelain veneer while maintaining ideal crown contours.

Improved Porcelain Support

One of the biggest advantages of a shoulder preparation for PFM crowns is the support it provides to the porcelain margin.

Porcelain is extremely strong under compression but relatively weak when subjected to tensile forces. When porcelain becomes too thin at the margin, the risk of fracture increases significantly.

The flat shoulder created by the Frank Dental D.848 provides a horizontal platform that supports the porcelain right to the edge of the restoration. This support helps distribute occlusal forces more evenly throughout the crown and reduces stress concentration at the margin.

The result is:

• Stronger porcelain margins
• Reduced chipping
• Reduced fracture risk
• Improved restoration longevity

Ideal for Porcelain Butt Margins

Many modern PFM crowns incorporate porcelain butt margins in highly aesthetic areas, particularly anterior teeth.

A porcelain butt margin eliminates the visible metal collar that can sometimes be seen at the gingival margin of traditional PFM crowns.

To successfully create a porcelain butt margin, the technician requires adequate porcelain thickness at the crown margin. A 90-degree shoulder preparation provides the necessary bulk of porcelain while maintaining strength and aesthetics.

The Frank Dental D.848 is therefore particularly valuable when preparing:

• Upper anterior PFM crowns
• Lower anterior PFM crowns
• Smile zone restorations
• Cosmetic crown cases

Better Aesthetics

One of the reasons PFM crowns continue to be widely used is their ability to combine strength with excellent aesthetics.

Creating a true shoulder preparation allows the technician to develop:

• Natural emergence profiles
• Better translucency
• Improved colour layering
• More life-like restorations

Without sufficient reduction, the technician may be forced to compromise aesthetics simply because there is not enough room for the ceramic layering process.

The D.848 shoulder preparation bur helps eliminate this problem by providing consistent and adequate reduction around the entire preparation margin.

Improved Crown Contours

Correct crown contour is essential for long-term restorative success.

When insufficient reduction is provided, crowns often become over-bulked in an attempt to accommodate both the metal coping and porcelain.

Over-contoured crowns can lead to:

• Gingival irritation
• Plaque retention
• Food trapping
• Difficult cleaning
• Patient discomfort

The shoulder margin created by the Frank Dental D.848 allows technicians to maintain ideal crown contours while still providing adequate material thickness.

Superior Laboratory Communication

Dental technicians appreciate clearly defined finish lines.

The sharp, well-defined shoulder produced by the Frank Dental D.848 creates an easily identifiable margin on:

• Conventional impressions
• Stone models
• Digital scans
• CAD/CAM workflows

This reduces ambiguity during crown fabrication and helps improve overall restoration fit and accuracy.

Better Digital Impression Accuracy

Modern digital workflows rely heavily on accurate margin detection.

A clearly defined shoulder margin is often easier for intraoral scanners to identify than poorly defined finish lines.

The D.848 helps produce a preparation that can be accurately scanned using systems such as:

• Trios
• iTero
• Medit
• PrimeScan
• CEREC

This improves crown design accuracy and may reduce the need for chairside adjustments.

Why Not Use a Chamfer for a PFM Crown?

While chamfer preparations can be used for certain PFM restorations, many clinicians prefer a shoulder preparation in areas where porcelain thickness and aesthetics are critical.

A chamfer margin provides less support for porcelain compared to a shoulder margin and generally offers less material thickness at the crown edge.

The 90-degree shoulder produced by the Frank Dental D.848 provides:

• Greater porcelain support
• Increased ceramic bulk
• Improved aesthetics
• Better fracture resistance
• Enhanced longevity

These advantages are particularly important for anterior PFM crowns and highly aesthetic restorative cases.

Frank Dental D.848 – Designed for Precision Shoulder Preparations

The Frank Dental D.848 range has been specifically developed to create precise shoulder margins for crown and bridge dentistry.

The bur features:

• Flat top design for creating a true shoulder floor
• Square edge for producing a 90-degree finish line
• Tapered body for excellent retention and resistance form
• Premium natural diamond coating for efficient cutting
• German manufacturing precision for predictable clinical outcomes

For dentists preparing teeth for porcelain fused to metal crowns, the D.848 remains one of the most effective burs available for producing a strong, clearly defined shoulder margin that supports both the metal framework and porcelain veneer.

Conclusion

A true 90-degree shoulder margin remains one of the most predictable preparation designs for porcelain fused to metal crowns. By creating adequate space for both the metal coping and porcelain veneer, the preparation helps improve crown strength, aesthetics, contour and longevity.

The Frank Dental D.848 Tapered Shoulder Diamond Bur has been specifically engineered to produce this preparation design efficiently and accurately. Its flat top and square-edge geometry create the ideal shoulder margin for PFM crowns, helping clinicians achieve restorations that are strong, aesthetic and built to last.

For dentists searching for a PFM crown preparation bur, shoulder margin bur, 90-degree shoulder diamond bur, metal ceramic crown preparation bur, crown preparation diamond bur, or Frank Dental crown preparation bur, the D.848 range provides a proven solution for modern restorative dentistry