Biological Testing of Dental Materials

| April 30, 2013 | 0 Comments

In 1978, the working team 5 of the Federation Dentaire International (FDI), the Commission for Dental Materials, Instruments, Tools and Therapeutics (COMIET) – today’s The Commission for Dental Products, have agreed upon the document No. 198 which was published in the bulletin No. 204.  The bulletin describes recommended tests for evaluation of dental materials.  It was published as the “ISO Technical Report”.  The publication actually represented the first international attempt to set up procedures and rules for evaluation and testing of dental materials and assessment of their harmlessness upon the contact with human tissues.  The report has reflected current level of knowledge at that time and showed readiness to modify or improve testing methods with the final goal of transforming this Technical report into an international norm.  The report has been accepted internationally, except Australia and South Africa, by national government authorities as responsible for evaluation of safety of dental materials used on their territories.
The Czechoslovak stomatology has accepted these rules in the modified form in compliance with available laboratory testing methods and technology in 1986.  This proposal also recommends standard methods for safety testing of dental materials designed for application into human tissues. This recommendation excludes pharmaceuticals, except those that are applied directly during a preserving or endodontic treatment.  Tests of environmental factors effects and dental equipment effects are excluded as well.  Recommended procedures include biological, not technical tests of materials.  Results of proposed tests will be presented as a part of applications for clinical trials.

Testing concerns the following groups of materials:
I.     Materials for preserving stomatology – designed for a tooth reconstruction.  Both metal and non-metal materials belong to this group.  They are inserted into a tooth as a temporary or permanent fillings.  They are in a short-term or permanent contact with tissues and the environment of the oral cavity.
II.     Prosthetic materials – designed for the teeth reconstruction.  The impression materials will stay for a short time inside the oral cavity, materials for molding of dentures will stay there longer.  Implantation materials remain in a tissue permanently.
III.     Materials for endodontics.  These materials serve as disinfectants and fillings of the tooth pulp cavity.  They may penetrate into the periapical ligamentous tissues and the bones via foramen apicis dentis.  Compounds for devitalization of the pulp belong here, too.
IV.     Materials for periodontics.  These materials are used for treatment of the periodontium, come into a temporary contact with the oral mucosa, submucous ligaments and the bone of the alveolar ridge.
V.     Materials used in orthodontics.  Remain inside the oral cavity for the period of up to several years.
VI.     Materials for the oral surgery.  Are present temporarily inside the oral cavity as plastic bandages or tissue glues.
VII.     Materials for stomatological prevention.  These materials enter the oral cavity for a long time.  They are utilized for filling of dental fissures as a prevention of dental decay or for teeth cleaning.

Degree of biological testing of dental materials

Initial tests

    •    Short-term test of systemic toxicity (oral way)
•    Test of acute systemic toxicity (intravenous way)
•    Test of toxicity by inhalation
•    Hemolysis test
•    Coagulation tests
•    Ames test of mutagenicity
•    Clastogenic test
•    Cellular transformation test
•    Test of dominant lethality
•    Cytotoxicity tests

Secondary tests

    •    Test of subcutaneous implantation
•    Test of implantation into a bone
•    Sensitization test
•    Test of oral mucosa irritation

Application tests

    •    Test of oral mucosa irritation
•    The pulp and dentine test
•    Test of materials used for the pulp overlay and pulpotomy
•    Endodontic application test
•    Bone implants application test
Initial tests:
•    The short-term test of systemic toxicity (oral way):  the test is designed to evaluate toxicity of a material tested during a short-term oral administration.
•    Test of acute systemic toxicity (intravenous way):  the test is designed to evaluate an acute toxicity during intravenous administration of studied material or extract.
•    Test of toxicity by inhalation: the test is designed to evaluate toxicity of materials or ingredients that are highly volatile at room temperature or under conditions of their use.
•    Hemolysis test: the test is designed to evaluate an acute, in vitro hemolytic activity of materials designed for a long-term contact with the bone and soft tissues.
•    Coagulation tests:  the tests should show possible changes that might be evoked by tested samples in the blood coagulation system in vitro.  These tests are supplementary.
•    Ames mutagenicity test: the test is designed to investigate mutagenic activity of solid or liquid materials, with recommendations for measurement of gases.
•    Clastogenic test: : the test is designed to investigate mutagenic activity of studied material on the chromosomal level.  It is a supplementary test.
•    Test of cellular transformation:  the test should determine a potential carcinogenic activity of materials studied.
•    Test of dominant lethality:  the aim of this test is to measure the dominant lethality or mutagenicity of materials studied.
•    Cytotoxicity tests:  the tests should check cytotoxicity of materials studied.  A variety of modifications are utilized in this test according to possibilities of  a laboratory.  They may be as follows: the test of dynamic determination of contact cytotoxicity, the combined test of cytotoxicity of cellular morphology and metabolism,  macro-contact method of the cytotoxicity test, cytotoxicity test in vitro, the test of tissue culture overlaid with agar, the test of proliferation of cells in culture, the test of dilatation of cells.

Secondary tests:
•    Test of subcutaneous implantation: the test is designed to evaluate a toxicity in vivo of tested materials designed for a long-term contact with subcutaneous tissues.
•    Test of implantation into a bone: the test is designed to evaluate a toxicity in vivo of tested materials designed for a long-term contact with the bone.
•    Sensitization test: the test is designed to evaluate a allergo-toxic potential of materials studied.
•    Test of the oral mucosa irritation: the test is designed to evaluate a tissue irritation by a tested material which will be temporarily or permanently adhered to the oral mucosa during its proposed use.  This test may be employed as an application one as well.

Application tests:
•    Test of the oral mucosa irritation:  the test was already described in the paragraph on secondary tests above.
•    The pulp and dentine test:  the test is designed to study reactions of the pulp and dentine to procedures and filling materials.
•    Test of materials used for the pulp capping and pulpotomy:  the test is designed for detection of reactions of the pulp and for pulpotomy.
•    Application test of an intra-bone implant: the test is designed for evaluation of materials that are mounted in a bone and penetrate partially the oral mucosa inside the oral cavity.

The above recommendations of the FDI follow a logical sequence, however, they are not a fixed scheme according to which every dental material should be tested biologically. They are rather guidelines of how and  in what order a material should be evaluated.  Further modifications and developments are possible in concordance with new findings.  Manufacturers of a particular dental product or material should obey this system and follow its rules.   For this purpose, a network of testing laboratories should be established in praxis, which would provide for a rational, although official biological testing.

Category: Prosthodontics, Prosthodontics

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