A 40 year old female patient presents to the clinic for teeth cleaning. Intra-oral examination reveals poor oral hygiene with generalized supragingival plaque covering atleast two-thirds of the crown surfaces. Silver amalgam restorations seen with 16, 17, 26 and 27. What type of corrosion may be seen with the restored teeth of this patient?
An important type of electrochemical corrosion is called concentration cell corrosion, which occurs whenever there are variations in the electrolytes or in the composition of the given electrolyte within the system. For example, there are often accumulations of food debris in the interproximal areas between the teeth, particularly if oral hygiene is poor. This debris then produces an electrolyte in that area, which is different from the electrolyte that is produced by normal saliva at the occlusal surface. Electrochemical corrosion of the alloy surface underneath the layer of food debris will take place in this situation.
For most metallic dental appliances, the deleterious effects of stress and corrosion, called stress corrosion, are most likely to occur during fatigue or cyclic loading in the oral environment.
When two dissimilar restorations are brought into contact, there is a sudden short-circuit through the two alloys. This can result in a sharp pain, called galvanic shock.
Phillips 12 th edition Pg- 44
Galvanic shock
Tarnish
Concentration cell corrosion
Stress corrosion