B04    Discuss the difference between physical and biological microleakage.

Physical microleakage

Microleakage can be detected by infiltrating gaps with stains, isotopes, or by measuring the flow rate of air around a restoration. All these measurements are done in vitro, and the results are often referred to in advertisements of different products.

Biologic microleakage

In this case, microorganisms infiltrate the gap. Such studies are very rarely conducted. There have been some clinical studies that have tried to relate pulp reactions to the ingrowth of microorganisms. Such studies have mainly been conducted on premolars that were extracted because of orthodontic reasons.

Microleakage Studies - Their Clinical Significance

Microleakage is often discussed in dentistry. Unfortunately, the clinical significance of leakage values (particularly physical microleakage) is questionable. Under clinical condition soon after restoration placement a biofilm will form within the gap. This film may affect the type of microbials that will enter the gap. The corrosive products present in the gap may also influence bacteria colonialization. For example, copper ions may be more toxic for some bacteria than for others. By considering the above aspects, a wide gap may, despite its width, favor a bacteria colonialization that is less cariogenic than the colonialization that occurs in a smaller gap. If this is the case, the composition of the material could be more important than the gap size. This example may explain why microleakage, particularly physical microleakage, may not be a very good predictor for the clinical performance.