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BIOLOGICAL PROPERTIES OF

DENTAL MATERIALS

(BIOCOMPATIBILITY)

ByHead of Department

Dr Rashid HassanAssistant Professor

Science Of Dental Materials Department

Rawal institute of Health SciencesRawal College of Dentistry

Islamabad

BIOMATERIAL

“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”

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BIOCOMPATIBILITY

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.

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BIOMECHANICS

“Behavior of a material in real structures is known as mechanics”

“Biomechanics is application of mechanics to biomaterials”

Biomechanics involve.

a) Limitation of a material.

b) Restorative design.

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ADVERSE EFFECTS FROM DENTAL MATERIALS Adverse effects may be, Toxic. Inflammatory. Allergic. Mutagenic.

These effects are differentiated on the basis of histological and pathological analysis of tissues.

TOXICITY

Earliest response studied.

First screening test for every material.

Materials may release toxic substances.e.g. lead containing materials.

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INFLAMMATION

Second type. Activate immune

response of the host.

May be due to toxicity or allergy.

Inflammation precedes toxicity.e.g.Pulpal and Periodontal diseases.

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ALLERGY

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 non-allergic inflammation or low grade toxicity.

E.g. Latex.

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MUTAGENIC REACTION

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)

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LOCAL and SYSTEMIC EFFECTS OF MATERIALSLOCAL EFFECTS:

Occur in the pulp of the tooth, periodontium, nearby mucosa or root apex.

Depends upon the ability of material.

E.g. Nickel containing crowns.

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LOCAL and SYSTEMIC EFFECTS OF MATERIALSSYSTEMIC 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.

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LOCAL and SYSTEMIC EFFECTS OF MATERIALSSYSTEMIC 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.

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MEASURING BIOCOMPATIBILITY OF DENTAL MATERIALS Biological response is related

to the use of a material. Factors affecting biological

response:1. Location of the material.2. Duration of the material in

the body.3. Stresses placed on the

materials.

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1. Location of the material

Surroundings can be a soft tissue or a hard tissue.

May be exposed directly to the blood, tissue fluids or saliva or through a barrier.

Might be placed externally or internally to the oral epithelium.

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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. Longer duration provides more

time to the material and body to react to each other.

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3. Stresses placed on the materials Stresses may be physical,

chemical or thermal. Properties of the material

comes under consideration.E.g. Strength of a material.

Fatigue stresses .

TESTS FOR MEASURING BIOCOMPATIBILIT

Y

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TYPES OF TESTS

3 basic types of tests.1. The in vitro test.2. The animal test.3. The usage test. No single test can measure the

biological response accurately.

1. IN VITRO TEST

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

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1. IN VITRO TEST

ADVANTAGES Relatively fast. Inexpensive. Easily standardized. Controlled conditions. Large scale testing.

DISADVANTAGES Lack of relevance to in vivo

conditions. Lack of complex systemic co-

ordinations.

2. THE ANIMAL TEST

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

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2. THE ANIMAL TEST

ADVANTAGES Intact biological system. Act as a bridge between in vitro

and usage test.

DISADVANTAGES Expansive. Difficult to control. May take months or years. Ethical concerns.

3. USAGE TEST

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”.

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3. USAGE TEST

DISADVANTAGES: Very costly. In case of humans ethical

permission requires. Prolonged time required for

results. Legal liabilities.

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TESTS USED TOGETHER No single test can evaluate

biocompatibility. Three phases are recognized1. Primary phase.2. Secondary phase.3. Usage phase.

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TESTS USED TOGETHER

Progress of testing

Number of materials

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TESTS USED TOGETHER

PRIMARY PHASE

Performed initially for testing a new material.Often in vitro.May also include some animal tests for systemic toxicity.

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TESTS USED TOGETHER

SECONDARY PHASE Always conducted in animals. Used to rule out any dermal

irritation, chronic toxicity or response upon implantation.

Can also rule out inflammation, allergy and sub lethal biological responses.

USAGE PHASE:-Same as discussed previously

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TESTS USED TOGETHER

Progress of testing

Number of materials

CURRENT BIOCOMPATIBILTY ISSUES IN DENTISTRY 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.

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CURRENT BIOCOMPATIBILTY ISSUES IN DENTISTRY 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”.

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QUESTIONS ????

QUESTIONS???

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