Mercury “dissolves” the ingredients and allows them to amalgamate into a new, putty like alloy. Note:

• Silver imparts strength and durability.
• Tin makes the amalgam easier to work.
• Copper increases hardness.
• Zinc increases workability, and unites with oxygen and other "impurities" to produce a clean amalgam.

• Amalgams are much easier to adapt into cavities and are not as technique sensitive (although in order to improve mechanical properties, particularly strength and expansion, some skill is required to remove as much excess mercury as possible).
• Amalgams can be used in a “moisture contaminated environment” (amalgams used here must not contain zinc as this can cause excessive expansion on setting with resulting pain and fracture.
• As an amalgam restoration ages in the oral cavity, corrosion products form along the restoration-tooth interface. These compounds act as a mechanical block to micro leakage and account for the excellent clinical results obtained with silver amalgam.
• Are quicker and cheaper.

• The main problem with amalgam fillings we feel lies in the potential for damage to teeth. Greater drilling of teeth is required before placing silver fillings.

• Because amalgams are not bonded to teeth the tooth is not supported and weak sections of teeth are able to flex and eventually form cracks.
• Amalgams also expand and contract greater than teeth and modern composites in response to temperature changes and thus can contribute to tooth fracture Thermal expansion coefficients 10-6/oC : Enamel 17^; Dentine 11^; Amalgam 40-60*; Composite 18~ ^Versluis et al Dent Mater 1996; Sep12:290. *VOCO. Scientific Documentation~ Fraunhofer Institute for Silicate Research in Wurzburg Grandio, Der HessischeZahnarzt 2006; 1:40
• Finally, amalgams undergo something called static creep over the years and results in their expansion and cracking of teeth (see Cracked Teeth).

• Many people object to amalgams appearance especially when it tarnishes and appears black.
• The possibility of a localized sensitivity reaction to the metals contained in amalgam.
• Less likely, but still a concern for many is the potential for systemic effects such as neurological and genetic damage caused by the high levels of mercury used in the alloy.
• Environmental effects of manufacturing, handling and disposing of mercury. Finally, amalgam will also conduct heat or cold readily (high thermal conductivity). If the amalgam is placed too close to the pulp, it may irritate the pulp. Therefore, an intermediate base of zinc oxide-eugenol (oil of cloves) that will not conduct heat or cold as readily (low thermal conductivity) may be placed under the amalgam.

• The most important physical properties of amalgam are:

• Flow and creep. Flow and creep are characteristics that deal with an amalgam undergoing deformation when stressed. The lower the creep value of an amalgam, the better the marginal integrity of the restoration. Alloys with high copper content usually have lower creep values than the conventional silver-tin alloys.
• Dimensional change and
• Strength. Amalgam is a strong material with good compressive strength. Sufficient strength to resist fracture is an important requirement for any restorative material. At a 50 percent mercury content, the compression strength is approximately 52,000 pounds per square inch (psi). In comparison, the compressive strength of dentin and enamel is 30,000 psi and 100,000 psi, respectively. The strength of an amalgam is determined primarily by the composition of the alloy, the amount of residual mercury remaining after condensation, and the degree of porosity in the amalgam restoration.

Antibiotics

• Are used to treat bacterial infections (selective toxicity) have no effect on other cells including viruses and mammalian cells.

Each class inhibits a biochemical process in bacteria but is safe for the same reactions in humans, for example, chloramphenicol and puromycin inhibit the bacterial ribosome, but not the structurally different eukaryotic ribosome.

• Improper use has a risk of resistance development.
• Used in intensive farming to promote animal growth, where they may be contributing to the rapid development of antibiotic resistance in bacterial populations.
• Allergy to penicillin can result in anaphylaxis.
• For resistance prevention and effectiveness, must be taken according to instructions:

Two to three times a day

For 5 to 7 days

• Tend to deplete probiotic organisms.