Explain why a clinician would decide against using a bonding alloy for a substructure of an anterior porcelain crown. List the alternative materials that could be used.

Explain why a clinician would decide against using a bonding alloy for a substructure of an anterior porcelain crown. List the alternative materials that could be used.

1. Disadvantages

   • • Bonding alloys can: - Distort at margins - Cause greening of porcelain - Be difficult to cast
   • • Metal/porcelain failure can occur.
   • • Bonding alloy does not look aesthetically pleasing.
   • • Patients can have an allergy to bonding alloy.
   • • As PFMs have a metal base underneath, the dentist needs to trim a large part of tooth to fit them well.
   • • PFM crowns increase the chances of gingivitis more than the other crown types.
   • • Over a period of time, the gum line of PFM crowns gets darker. A grey line appears there which is visible when you smile.
   • • PFMs are not suitable for someone who has receding gums / gums which have gone towards your bone.
   • • The porcelain from the PFM crowns can chip off when you bite on very hard foods.

2. Alternatives

   • • Due to their translucency full porcelain or all ceramic crowns are usually a better choice when restoring anterior teeth.
     • • One example is Zirconia, it can be used as an alternative to bonding alloy crowns, and the clinician may choose to use this as an alternative material because:
       • • Zirconia is white naturally
       • • Zirconia has no metal lining at the gums.
       • • These crowns require less tooth removal than many other types of dental crowns.
       • • Thanks to its extreme durability and natural look, zirconia crown is getting more and more popular.
     • • Emax is another all-ceramic system that can be used as an alternatice, it is based on Lithium disilicate glass, and consists of quartz, lithium dioxide, phosphoroxide, alumina, potassium oxide and trace elements. Emax based all-ceramic prostheses are rapidly gaining widespread popularity in cosmetic dentistry due to their excellent esthetics, durability, and strength.
     • • Sintered alumina is also an alternative material for an anterior crown.
   • • However if the clinic/laboratory is unable to produce all ceramic crowns, another alternative could be porcelain fused to gold alloys instead of bonding alloy.
     • • Using a gold substructure requires less of the tooth to be trimmed.
     • • A gold substructure is also better on the gums compare to other metal alloys.