Due to its durability and natural aesthetics, the PFM crown is still a common instrument for fixed restoration in many dental offices. The prep design must be carefully mapped out since PFM crown prep requires substantial tooth reduction to allow both metal and porcelain to fit in.
Porcelain-fused-to-metal (PFM) crowns are among the most well-liked and dependable restorations. This material closely resembles the look of a genuine tooth using a cast metal framework covered with porcelain.
For this dental restoration to be effective, the tooth must be sufficiently prepped, which sometimes necessitates significant dental reduction. To conceal the metal base and the expansive porcelain used to disguise this alloy, the crown must be thick enough. A methodical, planned approach to tooth preparation helps to guarantee that the prep is properly formed.
Tools Needed For PFM Crown Preparations
The materials needed for a PFM crown preparation are:
- Metal matrix band
- Coarse-grit flat-end tapered diamond bur
- Fine-grit flat-end tapered diamond bur
- Scalpel blade and handle
- High-speed handpiece
- End-cutting diamond bur
- Coarse-grit football-shaped diamond bur
- A small diameter round-end diamond bur
- Silicone putty impression material
- End-cutting diamond bur
- Wooden wedges
Preparation Technique for PFM Crown (Anterior Teeth)
- To satisfy aesthetic needs, the reduction on the labial surface of an anterior tooth should be between 1.2mm-1.5mm while the lingual surface should be reduced by 1mm, and incisal surfaces.
- A central cervical groove that is parallel to the placement path along the long axis of the tooth must be created in order to properly prepare the labial surface, while other two secondary grooves should be placed on either side.
- There must be 1.8 mm of depth in the incisal edge reduction grooves that are installed.
- Then the reduction of 0.55mm is done on the lingual chamfer.
- The cervical shoulder between the depth grooves should be 1mm wide.
- Shape the lingual surface using a football-shaped diamond bur.
- A fine-grit diamond bur is then used to finish the preparation. If at all feasible, think about using metal collars since this will assist limit how much of the cervical teeth must be prepared. For teeth with exposed root dental pulp or gum disease, this is extremely advantageous.
Preparation Technique for PFM Crown (Posterior Teeth)
- Depth holes are made in the occlusal area of posterior teeth to make it easier to make occlusal depth reductions while preparing them for PFM crowns.
- A lingual chamfer and a buccal collar can be made once these depth cuts are finished, which also allows for the reduction of the occlusion. At least 1mm lingually from the proximal connection should be covered by the buccal shoulder preparation.
- Typically, 1.5 to 2 mm of space is needed for the posterior teeth’s occlusal edges. If the crown is made with a metallic occlusal area or metal bite stop, the occlusal decrease may be minimal.
- It is essential that every margin be defined and continuous throughout the perimeter.
- The completed preparation must be free of any discernible bur marks and every other curve must be rounded.
- The incisal borders of anterior preparations and the change from the axial wall to the occlusal in posterior preparations are two places that are commonly overlooked during completion.
- Diamond burs or hand tools should be used to complete the margins.
