Biocompatibility Of Dental Materials

Biocompatibility Of Dental Materials

Write a short note on the biocompatibility test.
Or
Write in brief on biocompatibility tests for dental materials.
Answer:

Evaluation of biocompatibility of dental materials is a complex and comprehensive area due to unwanted tissue reactions that occur in many types.

• Individual test methods are usually adequate only to describe a single aspect of certain types of unwanted reactions.
• Following are the biocompatibility tests: These tests are carried out at three levels one after another. If the material is successful in the first test then only the second test is carried out and likewise. If successful in the second test then the subsequent tests are carried out.

Group I: Initial or Primary Tests:

• Genotoxicity test: In this test, the effect of the material on the genes is carried out.
• Cytotoxic assays: By these tests, the effect of the material or its leachable products is studied on the metabolic functions of the test cell system.
• Cell plating and growth tests: These tests are done to determine if the material interferes with cell functions by releasing some component of the material into the medium. In this a small piece of sterile material is placed in the cells of tissue culture dishes then the cells are plated at a particular density within the cells in tissue culture medium for l to 3 days. Biologically inert materials like siloxane polymer or Teflon are used as negative controls.
• Mutagenesis assays: These assays are done in vitro to identify materials and chemicals that are capable of producing cancer.

Group II: Intermediate or Secondary Tests: After screening by initial tests of the materials developed for a specific use, the successful materials are tested generally on experimental animals, i.e. guinea pigs, rodents, and hamsters.

• Systemic toxicity test: In this, the product is evaluated for its potency to create systemic toxicity.  For this oral median lethal dose (LD50) test is done in which a test sample is daily administered to rats for l4 days. If half or more than half of the animals survive it is considered that the product has passed the test.
• Inhalation toxicity test: This test is done on guinea pigs, rats, rabbits, or hamsters in exposure to aerosol preparations and the material is sprayed for l0 times around the head and chest of the animals for 30 seconds at half an hour intervals.
• If any animal dies within 3 minutes the product is considered very toxic. If none of the animals dies in four days the product is considered safe.
• Mucous membrane irritation test: In this, the product is applied directly to the oral mucous membrane or abraded skin continuously for several weeks in 10 animals. The histological examinations are done along with controls, if there is no irritation or histological changes the product is considered safe.
• Skin irritation toxicity and sensitization tests (maximization test).
• Implantation tests: Done for the materials that will contact subcutaneous tissues and bone.

Group III: Human Trials: If the material has passed primary and secondary tests, it is ready for trial in humans where: Reactions and performance under clinical conditions are studied.