BIOLOGICAL PROPERTIES OF DENTAL MATERIALS BIOCOMPATIBILITY By Head

BIOLOGICAL PROPERTIES OF DENTAL MATERIALS (BIOCOMPATIBILITY) By Head of Department Dr Rashid Hassan Assistant Professor Science Of Dental Materials Department Rawal institute of Health Sciences Rawal College of Dentistry Islamabad 1

BIOMATERIAL n n “When a material is placed within, or in contact with the human body, it is referred to as biomaterial” OR “A non living material designed to interact with the biological system” 2

BIOCOMPATIBILITY n n Defined as, “The ability of a material to elicit an appropriate biological response in a given application in the body. ” The material is said to be “biocompatible” when it possesses the property of being non destructive in a biological system. 3

BIOMECHANICS n n n a) b) “Behavior of a material in real structures is known as mechanics” “Biomechanics is application of mechanics to biomaterials” Biomechanics involve. Limitation of a material. Restorative design. 4

ADVERSE EFFECTS FROM DENTAL MATERIALS Adverse effects may be, n Toxic. n Inflammatory. n Allergic. n Mutagenic. These effects are differentiated on the basis of histological and pathological analysis of tissues. n 5

TOXICITY n n n Earliest response studied. First screening test for every material. Materials may release toxic substances. e. g. lead containing materials. 6

INFLAMMATION n n Second type. Activate immune response of the host. May be due to toxicity or allergy. Inflammation precedes toxicity. e. g. Pulpal and Periodontal 7

ALLERGY n n n Most Familiar to the general public. Body specifically recognizes a material as a foreign body and reacts disproportionately to the amount of material. Involves all the dimensions of the immune system. Can be difficult to differentiate from nonallergic inflammation or low grade toxicity. E. g. Latex. 8

MUTAGENIC REACTION n n Occurs when the components of the materials alter the base pair sequence of DNA. May be due to direct / indirect interactions. Does not imply carcinogenicity. Metal ions from a dental material (nickel, beryllium and copper) 9

LOCAL and SYSTEMIC EFFECTS OF MATERIALS LOCAL EFFECTS: Occur in the pulp of the tooth, periodontium, nearby mucosa or root apex. n Depends upon the ability of material. n E. g. Nickel containing crowns. 10

LOCAL and SYSTEMIC EFFECTS OF MATERIALS SYSTEMIC EFFECTS: Due to substances that gain access to the body. ingestion and absorption from the gut, inhaled vapor, absorption through oral mucosa or release from the tooth apex. 11

LOCAL and SYSTEMIC EFFECTS OF MATERIALS SYSTEMIC EFFECTS: May occur by blood or lymphatic transport or simply by diffusion. Systemic effect depends upon, 1. Duration and concentration of exposure. 2. Excretion rate of substance. 3. Site of exposure. 12

MEASURING BIOCOMPATIBILITY OF DENTAL MATERIALS n n 1. 2. 3. Biological response is related to the use of a material. Factors affecting biological response: Location of the material. Duration of the material in the body. Stresses placed on the 13

1. Location of the material Surroundings can be a soft tissue or a hard tissue. n May be exposed directly to the blood, tissue fluids or saliva or through a barrier. n Might be placed externally or internally to the oral epithelium. n 14

2. Duration of the material in the body May be: 1. Short duration-> 4 – 6 minutes. e. g. Impression materials. 2. Longer duration-> for ten years. e. g. Fixed prosthesis. n Longer duration provides more time to the material and body to react to each other. n 15

3. Stresses placed on the materials n Stresses may be physical, chemical or thermal. n Properties of the material comes under consideration. E. g. Strength of a material. Fatigue stresses. 16

TESTS FOR MEASURING BIOCOMPATIBILITY 17

TYPES OF TESTS n 1. 2. 3. n 3 basic types of tests. The in vitro test. The animal test. The usage test. No single test can measure the biological response accurately. 18

1. IN VITRO TEST n n Performed outside the organism. First screening test to evaluate biological response of a new material. Conducted in test tube, cell culture dish, flask or other container. Contact may be direct/indirect. 19

1. IN VITRO TEST ADVANTAGES Relatively fast. n Inexpensive. n Easily standardized. n Controlled conditions. n Large scale testing. n DISADVANTAGES n n Lack of relevance to in vivo conditions. Lack of complex systemic coordinations. 20

2. THE ANIMAL TEST n n Material placed into an intact organism. Commonly used animals are mice, rats, hamsters or guinea pigs. Other animals used are cats, sheep's, dogs, monkeys and baboons. Distinct from usage tests. 21

2. THE ANIMAL TEST ADVANTAGES n n Intact biological system. Act as a bridge between in vitro and usage test. DISADVANTAGES Expansive. n Difficult to control. n May take months or years. n Ethical concerns. n 22

3. USAGE TEST n n n Performed in animals or humans. In case of humans it is called as clinical trial. Choice of animal is limited. Animals used should be large, with anatomy similar to the humans. Human clinical trial is the “gold standard”. 23

3. USAGE TEST DISADVANTAGES: n Very costly. n In case of humans ethical permission requires. n Prolonged time required for results. n Legal liabilities. 24

TESTS USED TOGETHER n n 1. 2. 3. No single test can evaluate biocompatibility. Three phases are recognized Primary phase. Secondary phase. Usage phase. 25

TESTS USED TOGETHER Usage SECONDARY PRIMARY Progress of testing Number of materials 26

TESTS USED TOGETHER PRIMARY PHASE Performed initially for testing a new material. Often in vitro. May also include some animal tests for systemic toxicity. 27

TESTS USED TOGETHER SECONDARY PHASE Always conducted in animals. n Used to rule out any dermal irritation, chronic toxicity or response upon implantation. n Can also rule out inflammation, allergy and sub lethal biological responses. n n USAGE PHASE: Same as discussed previously 28

TESTS USED TOGETHER Usage SECONDARY PRIMARY Progress of testing Number of materials 29

CURRENT BIOCOMPATIBILTY ISSUES IN DENTISTRY n n Latex: Incidence rate 6% 7% may cause localized rashes or swelling, dermatitis of hands (eczema) Nickel: Incidence rate 10% 20%. 100% of patients sensitive to palladium will be sensitive to nickel. 30

CURRENT BIOCOMPATIBILTY ISSUES IN DENTISTRY n n n n Nickel: But only 33% of individuals allergic to nickel will be allergic to palladium. Etiology not known. Beryllium: Only used in 1% – 2% by weight in Ni-Cr alloy. Carcinogenic effects. Can cause “beryllosis”. 31

QUESTIONS ? ? 32