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BIOCOMPATIBILITY OF DENTAL MATERIALS

BIOCOMPATIBILITY OF DENTAL MATERIALS. DR.RAMASHANKER Associate professor Deptt. of prosthodontic 3 rd nov2014 time-10-11am. Introduction History Definition Requirements Tests for evaluation

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BIOCOMPATIBILITY OF DENTAL MATERIALS

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  1. BIOCOMPATIBILITY OF DENTAL MATERIALS DR.RAMASHANKER Associate professor Deptt. of prosthodontic 3rd nov2014 time-10-11am

  2. Introduction History Definition Requirements Tests for evaluation Allergic responses to dental materials Materials considered for biocompatibility Physical factors affecting pulp health Summary References CONTENTS

  3. Introduction • Biocompatibility :- interaction between body & material • Body ↔ Material • Placement of material creates interface : dynamic • Interface activity depends on: - location of material - its duration in body - its properties - health of host

  4. History • Mid 1800’ s dentists tried new materials for first time by directly putting them in patient’s mouth eg. Fox : fusible metal-bismuth, lead & tin-melted & poured in cavity preparation at appx.100o C • G.V. Black tried his new ideas of restorative materials, like early amalgams in patients’ mouth

  5. Concept of protecting patients- early 1960’s • Regulations & ethics introduced • Organisations like FDA,ANSI,ADA and ISO .

  6. Being harmonious with life & not having toxic or injurious effects on biologic function. (G.P.T. 8th edn.-2005) Ability of the material to elicit an appropriate biological response in a given application in the body (Kenneth J.A). Definition

  7. Should not be harmful to pulp & soft tissues Should not contain toxic diffusible substances Should not produce allergic responses Should not be carcinogenic Requirements for Dental Material Biocompatibility

  8. Any substance, other than a drug, that can be used for any period as a part of a system that treats, augments, or replaces any tissue, organ or function of the body. (G.P.T. 8th edn.-2005) Biomaterial

  9. Those which contact soft tissues within the oral cavity eg. Acrylic resin Those which could affect health or vitality of pulp eg. Liner, bases Those which are used as root canal filling materials eg. Gutta percha Classification of Biomaterials from perspective of Biocompatibility

  10. Those which affect hard tissues of oral cavity eg. Implants Those used in dental laboratory eg. Nickel, chromium, cobalt Classification of Biomaterials from perspective of Biocompatibility

  11. Classical biological reactions to materials are : TOXICITY INFLAMMATION ALLERGY MUTAGENICITY ADVERSE EFFECTS FROM DENTAL MATERIALS

  12. Earliest response studied Earlier material containing LEAD posed a risk to patient due to toxic property of lead TOXICITY

  13. Involves activation of the host immune system Histologically it is characterized by edema of the tissue with infiltration of acute & chronic inflammatory cells INFLAMMATION

  14. Most common response that occurs when the body recognizes a material as foreign Reactions involves all dimensions of immune system An allergic reaction results histologically in an inflammatory response that can be difficult to differentiate between non allergic inflammation or low grade toxicity . ALLERGY

  15. Allergy

  16. Allergic Responses to Dental Materials • Allergic Contact Dermatitis • Allergic Contact Stomatitis • Allergy to Latex products

  17. Most common occupational disease Susceptibility & prior sensitization necessary Dose independent Allergic Contact Dermatitis

  18. Allergic Contact Dermatitis • Usually occurs where body surface makes direct contact with allergen. eg. Monomers of bonding agent- distal part of fingers & palmer aspect of fingertips • Acrylic component of dental cements, nickel & resin monomers-allergic contact sensitizers.

  19. Most definitive diagnostic test Suspected allergen applied to skin to produce small area of allergic contact dermatitis After 48 to 96 hrs hyperemia, edema, vesicle formation & itching Positive reaction (Slavin and Ducomb,1989) Patch Test

  20. Allergic Contact Stomatitis • Most common adverse reaction to Dental Materials A) Local/contact type lesions B) Systemic/distant lesions

  21. Common allergens :- chromium, cobalt, mercury, eugenol, components of resin based materials, & formaldehyde Mouthwashes, dentifrices, lozenges, & cough drops cause burning, swelling & ulceration of oral tissues. Lichenoid reactions :- Long-term effect in oral mucous membrane adjacent amalgam & composite resins. (Bratel and Johntell,1994) Allergic Contact Stomatitis

  22. Allergy to Latex Products • Polyether component-main causative agent …March,1988 • Dermatitis of hand (eczema) most common adverse reaction • Localized rashes & swelling to wheezing & anaphylaxis

  23. Repeated exposure & duration plays important role. Most serious systemic reactions occur when gloves or rubber dam contact mucous membrane - generalized angioneurotic edema, chest pain, rash on neck or chest region and respiratory distress …Blinkhorn and Leggate,1984

  24. Prevention: Use Vinyl gloves or gloves made of other synthetic polymer gloves:- Polythene gloves. Powder free gloves. Nitrile gloves.

  25. Mutagenicity results when the components of the material alter the base pair sequences of the DNA in cells Dental materials or components such as nickel, copper, beryllium, some components of root canal sealers & resin based materials are mutagens MUTAGENIC REACTIONS

  26. Two key factors have paramount importance : Metal Corrosion or Metal degradation Surface Characterstics KEY PRINCIPLES THAT DETERMINE ADVERSE EFFECTS

  27. Biocompatibility depends on degradation process Biological response of corrosion products depends on: Amount Composition Form Location in tissues CORROSION

  28. Biological environment in contact also determines the corrosion property for eg: salivary esterases accelerate breakdown of dental resins Ingestion of acidic substances may alter corrosion of alloys or ceramics CORROSION

  29. Surface different from the Interior region For eg: casting alloy sealant EFFECTS OF SURFACE : Ti alloys promote osseointegration Rough surface promotes corrosion SURAFCE CHARATERISTICS

  30. Aim To eliminate any potential harm or damage to oral or maxillofacial tissues from a product or any component of a product To modify or control the use by manufacturer & operator to prevent cytotoxicity. Tests for Evaluation of Biocompatibility

  31. Biocompatibility tests are classified on three levels (tiers) :- Group I : Primary tests Group II : Secondary tests Group III : Usage tests Tests for Evaluation of Biocompatibility

  32. Group I : Primary Tests • Advantages :- • in vitro test, done in controlled experimental condition • Most rapid, economical & easily standardized • Large scale screening • Disadvantages :- • Lack of relevance to in vivo use of material • Lack of immune, inflammatory & circulatory system

  33. Material in a fresh or cured state → placed directly on tissue culture cells or on membranes overlying them. e.g.. Agar (Agar overlay technique) Barriers like dentin disks Cytotoxicity Tests

  34. Determines carcinogenic/mutagenic potential Carried out on mammalian or non-mammalian cells, bacteria, yeasts, or fungi. Evaluates gene mutations, changes in chromosomal structure & other DNA or genetic changes caused by dental materials. Genotoxicity Tests

  35. Ames Test :- -Material is tested with mutant histidine dependant bacteria -Agent is added to culture medium consisting salmonella typhimurium mutant gene which cannot produce histidine -If carcinogenic :- salmonella species reversed to original state, i.e.... start producing histidine again Genotoxicity Tests

  36. Advantages :- Intact biologic system to respond to a material Provide important bridge between in vitro environment & clinical use of material Disadvantages :- More expensive & difficult to control Time consuming Ethical concerns Group II : Secondary Tests

  37. 1. Systemic toxicity test :- Material administered to test animals e.g.. Rats- orally or i.v. If > 50% animals survive material is safe Group II : Secondary Tests

  38. 2. Skin irritation test :- Irritation is inflammation without intervention of antibody or immune system. Material held in contact with shaved skin of rats for 24 to 90 days Erythema & edema are examined & confirmed. Group II : Secondary Tests

  39. 3. Skin Sensitization test :- Sensitization is inflammatory response requiring participation of an antibody system specific for material allergen. Done similar to irritation tests Group II : Secondary Tests

  40. 4. Inhalation toxicity test :- Performed on rats, rabbits or guinea pigs in exposure chamber with aerosol preparations by releasing spray material around head & upper trunk of animals. Death within 2 to 3 min. very toxic No death safe for human application Group II : Secondary Tests

  41. 5. Implantation test :- Only used for testing implants & endodontic materials. Material placed subcutaneously,intramuscularly, or as a bone implant at lateral cortex of femur or tibia or both Histopathological examination has to be done Observation period may be upto 1 year. Group II : Secondary Tests

  42. IMPLANTATION TEST

  43. Advantage :- Material placed in an environment clinically relevant to its use in clinical practice Disadvantages :- Extremely complex & difficult to perform Exceptionally expensive & very time consuming Ethical concerns In animals : usage tests In humans : clinical trials Group III : Usage Tests

  44. Classical progression of biocompatibility tests

  45. Newer schemes for progression of biocompatibility tests

  46. VARIOUS DENTAL MATERIALS CONSIDERED FOR BIOCOMPATIBILITY

  47. Metals : Amalgam & mercury Nickel Beryllium Gold Resins : Acrylic Resins Chemically cured composite resins Light cured composite resins

  48. Cements : Silicate cement Zinc Phosphate cement Glass ionomer cement Zinc oxide Eugenol cement Miscellaneous : Impression materials Implant materials

  49. Mercury itself has no effect on pulp Pulp response related to condensation pressure Rate of diffusion into enamel & dentin-inversely related to degree of mineralization. Amalgam & Mercury

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