B01    Identify the potential pulp irritating mechanisms among materials such as amalgam, chemically cured resin composites, light-cured resin composites, zinc phosphate cement, glass ionomer cement, resin-based composite cements, conditioning agents, and bonding agents.

Dentin is a "living" tissue. Dentin fluids pass through the dentin via the dentin canals. Inside the tubules we can also find the odontoblastic processes. During operative procedures, the dentin is exposed. Under some conditions even the pulp may be exposed. If only the dentin is exposed, it is always a possibility that toxic components from the restorative material may diffuse through the dentin and irritate and damage the pulp tissue. Microorganisms may also invade the pulp if the seal around the restoration is not good. This can lead to an infection of the pulp tissue. Other stimuli, such as mechanical and/or thermal stimuli, can also cause discomfort. It is because of the above possibilities as the cut dentin surface often is covered with a varnish, liner or a base before a restoration is placed.

    Intact Tooth                    Prepared and Restored

Different materials can irritate the pulp differently. Below is a brief description of the irritating ability of some commonly used restorative materials.

Amalgam

Inert to mildly irritating to the pulp. Mercury by itself does not seem to contribute to any pulp response. The elements that are most extensively seen around amalgams in the dentin are zinc and tin. Most of the irritations are rather due to trauma during preparation and condensation or caused by microleakage.

Chemically cured composites

Chronic irritations have been seen adjacent to chemically cured composites that have not been lined or bonded. Some of the numerous components may have caused these irritations, or they may be a result of polymerization shrinkage and leakage.

Light-cured resin composites

Poor curing may be a potential problem. Polymerization shrinkage is another problem. The heat generated by the light source can also cause some irritation under certain conditions.

Zinc phosphate cement

The more acid that is used, the more pronounced is the pulp reaction. Thus, bases do not induce significant reactions in contrast to the cement when it is used as a luting agent.

Glass ionomer cement

The GI often produce a more pronounced pulp reaction than both zinc phosphate cements and polycarboxylate cements. A possible explanation is that the reaction between the polyacrylic acid and the glass powder is slower than the setting reaction of the other two cements.

Resin-based cements

Similar behavior as the light-curable resin composites

Conditioning agents

Most conditioners are acids (except EDTA). A short etch (15-30 s) followed by water rinse (20s) will not cause any harm to the pulp as long as the remaining dentin thickness exceeds 0.1 mm.

Bonding agents

Do not seem to cause any significant pulp irritations.