Flux and Anti-Flux in Soldering: Types, Functions, and Applications in Dentistry

Soldering Fluxes

Flux in Dentistry

Flux is the compound that is applied to the metal surfaces which is to be joined to prevent the formation of oxides which reduce the strength of soldered area.

The function of Flux in Dentistry:

Flux plays three roles, i.e.

• Flux removes impurities, i.e. dirt, oil, and oxide from the joint. These impurities weaken the joint
• Flux acts as a reducing agent. As the metal gets heated to melt solder, increase temperature leads the metal to reoxidize, so the reducing agent prevents this reoxidation.
• Flux acts as a wetting agent and decreases the surface tension of solder which increases its flow and wettability.

Classifiation of Flux in Dentistry

• According to their main purpose:
  • Surface protection type: This flux covers the metal surface and prevents access to oxygen so that no oxides can form.
  • Reducing agent type: It reduces any oxide present and exposes clean metal.
  • Solvent type: It dissolves, oxide and drives them away.
• According to their pH:
  • Acidic flux: Silicon dioxide
  • Basic flux: Calcium oxide and calcium carbonate
  • Neutral flux: Fluorspar and borax
• According to their source:
  • Organic: Used in soft soldering purposes which need lower temperature
  • Inorganic: These are acid based. Used in brazing procedures which require high temperatures.
• According to their composition:
  • Borax flux:
    1. Used for noble metal alloys
    2. Act as protective fluxes and reduce fluxes
  • Fluoride flux: Used with base metal alloys.

Composition of Flux in Dentistry

Application of Flux in Dentistry

• Flux should be painted on the substrate metal at the junction of pieces to be joined.
• Pre-fixed solders are available in tube form with the flux being contained in the tube. So there is no need to apply flux separately

Antiflxes of Flux: The flow of solder can be prevented by the use of an antireflux material. It is applied to the surface before the flux or solder is applied. Soldiers will not flow into an area where antireflux has been applied.

Flux in Dentistry Examples:

• Graphite (soft lead pencil)
• Rouge (iron oxide)
• Whiting (calcium carbonate)
• In an alcohol and water suspension.