biocompatibility of dental materials DR.ANUKRITY.ppt

Biocompatibility of dental materials in dentistry

1. BIOCOMPATIBILITY OF
DENTAL MATERIALS
Dr.ANUKRITY CHANDRA GUIDED BY:
MDS 1
ST
YEAR Dr. SUDHEER ARUNACHALAM
PROSTHODONTICS AND Dr. TUSHAR TANWANI
CROWN AND BRIDGE Dr. ANUPAM PURAWAR
Dr. NEHA NAVLANI
Dr. RUCHI GUPTA
Dr. SUDEEPTI SONI

2. CONTENTS
Introduction
History
Definition
Requirements
Tests for evaluation
Allergic responses to dental materials

Materials considered for biocompatibility

Physical factors affecting pulp health
Summary
References

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.100
o
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. Definition
Being harmonious with life & not having toxic or
injurious effects on biologic function.
(G.P.T. 8
th
edn.-2005)

 Ability of the material to elicit an appropriate biological
response in a given application in the body (Kenneth
J.A).

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

8. Biomaterial

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. 8
th
edn.-2005)

9. Classification of Biomaterials from
perspective of Biocompatibility
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

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

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

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

15. ALLERGY
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 .

16. Allergy

17. Allergic Responses to Dental
Materials
Allergic Contact Dermatitis
Allergic Contact Stomatitis
Allergy to Latex products

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

19. Allergic Contact Dermatitis

Usually occurs where body surface contact with
the 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.

20. Patch Test
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)

21. Allergic Contact Stomatitis
Most common adverse
reaction to Dental Materials

A) Local/contact type lesions
B) Systemic/distant lesions

22. 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

23. 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

24. 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

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

26. MUTAGENIC REACTIONS
•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

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

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

29. CORROSION
•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

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

31. Tests for Evaluation of
Biocompatibility

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.

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

33. 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

34. Cytotoxicity Tests
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

35. Genotoxicity Tests
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.

36. Genotoxicity Tests
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

37. Group II : Secondary Tests
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

38. Group II : Secondary Tests
1. Systemic toxicity test :-
 Material administered to test animals e.g.. Rats-
orally or i.v.

 If > 50% animals survive material is
safe

39. Group II : Secondary Tests
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.

40. Group II : Secondary Tests
3. Skin Sensitization test :-

 Sensitization is inflammatory response requiring
participation of an antibody system specific for
material allergen.
 Done similar to irritation tests

41. Group II : Secondary Tests
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

42. Group II : Secondary Tests
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.

43. IMPLANTATION TEST

44. Group III : Usage Tests
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

45. Classical progression of biocompatibility tests

46. Newer schemes for progression of biocompatibility
tests

47. VARIOUS DENTAL MATERIALS
CONSIDERED FOR
BIOCOMPATIBILITY

48. Metals : Amalgam & mercury
Nickel
Beryllium
Gold

Resins : Acrylic Resins
Chemically cured composite resins
Light cured composite resins

49. Cements : Silicate cement
Zinc Phosphate cement
Glass ionomer cement
Zinc oxide Eugenol cement

Miscellaneous : Impression materials
Implant materials

50. Amalgam & Mercury
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.

51. Mercury
Elemental mercury, Inorganic ion & Methyl mercury
Methyl mercury :-formed by biologic action of
elemental mercury; Absorbed 100% in gut; Most toxic
Elemental mercury absorbed less than 0.01%
65% to 85% mercury vapor that is inhaled is retained
in body

52. Mercury Levels in Blood
 Subjects with amalgam restoration 0.7ng/mL

 Subjects without amalgam restoration 0.3ng/mL
 Lowest level at which earliest 35ng/mL
non-specific symptoms occur

53. Mercury Hazard to Dental Personnel
Via inhalation & skin contact (allergic contact
dermatitis)
Accidental spillage
Handling with bare fingers
Improper storage
Improper retrieval of spilled mercury or waste
amalgam
Faulty equipment

54. Acute mercury poisoning :-
Rare; stomatitis & diarrhoea
Chronic mercury poisoning :-
Weakness, fatigue, anorexia, wt. loss, insomnia,
irritability, shyness, dizziness & tremors in extremities.
Methyl mercury poisoning :-
Paresthesia of extremities, lips & tongue; ataxia (gait
disturbance), & concentric constriction of visual fields
(Tunnel Vision)

55. Recommendations in Mercury Hygiene
1.Store in unbreakable tightly sealed containers
2.Clean-up spilled mercury immediately
3.Do not handle with bare hands
4.Salvage all amalgam scrap & store it under water
5.Use water spray & suction while grinding
6.Do not use ultrasonic condensers
7.Periodic mercury vapor level determination in clinic
8.Alert health personnel about hazards of mercury
9.Use of rubber dam
10.Provide adequate ventilation

56. Nickel
Most common cause of
allergic dermatitis
Female : Male :: 10 : 1
Intraorally : little chance
of allergy
Nasal & sinus cancer
among nickel refinery
workers due to nickel
carbonyl

57. Beryllium
Component of base metal alloys
Highest risk to dental technicians during melting &
trimming of alloy
Berylliosis : inflammatory lung disease due to
inhalation of beryllium dust or fumes

58. Beryllium
Prevention :
•Confirm allergy by Patch test
•Avoid base metal restorations in patients with
known allergy
•Good ventilation & exhaust

60. Gold
Pure gold is inert
Allergy to gold is very rare
(1 in 1 million)

61. Cements

62. Acrylic Resin
Cause allergic reactions
(denture stomatitis) when
used as denture base
material or provisional fixed
partial denture resin
Highest risk for dental
professionals due to
frequent exposure to
unpolymerized monomer

63. Chemically Cured Resin Composites
Require use of matrix pressure to enhance adaptation to
cavity walls : Potential pulp irritant
Chronic pulpitis : persists for indefinite period, after
2 to 3 weeks, develop massive pulp lesion
Thin coating of hard setting Ca(OH)
2
cement
recommended for deep cavities

64. Light-Cured Resin Composites
Visible light cured systems : greater depth of cure, shorter
curing time, less porosity & more wear-resistant restorations
than UV light cured systems less pulp response
Use twice the recommended time exposure to light
Conservative cavity preparation & incremental curing;
no need for matrices & pressure, to gain adaptation
less toxicity to pulp

65. Impression Materials
Irreversible hydrocolloids :- Inhaling fine airborne
particles (dust) can cause silicosis & pulmonary
hypersensitivity.
Dustless/Dustfree alginate is preferred
Elastomers :- Cellular toxicity levels
Polyether > Addition Silicone > Polysulphide

66. Implant Materials
Commercially pure Titanium & its alloys are the most
biocompatible restorative materials
Bio-glass ceramics used as implant materials also
exhibit good biocompatibility

67. Implant Materials
Osseointegration :- Materials have very
low degradation rates, & tend to form
surface oxides that promote bony
approximation within 100A
o
space
eg. Titanium, tantalum, several forms of
ceramics
Biointegration :- Materials undergo
degradation to promote bone formation
without any intervening space
eg. Bio-glass ceramics

68. PHYSICAL FACTORS
AFFECTING PULP HEALTH

69. Microleakage
Free penetration of fluids, micro-organisms & oral debris
along interface between restoration & tooth, progressing
down the walls of cavity preparation
It can result in :-
1.Secondary/Recurrent caries acute/chronic pulpitis,
pulp abscess, etc.
2.Staining or discoloration
3.Sensitivity due to continuing Pulpal irritation

70. Nanoleakage vs Microleakage

71. Prevention:-
1.Use bonding/adhesive techniques for better adaptation
of restoration to tooth surface
2.Regular monitoring of restoration
3.Use cavity varnish below amalgam restoration
(leakage space filled by corrosion products thereby
sealing cavity : but requires much time)

72. Thermal Changes
Temperature fluctuations in oral cavity may crack
restorative material or produce undesirable dimensional
changes Microleakage
Thermal conductivity & coefficient of thermal
expansion
Metals are good conductors of heat, causing sensitivity
with large metallic restorations
eg. Amalgam or gold inlays
Provide suitable base

73. Galvanism
Flow of current when two
dissimilar metallic restorations
oppose each other in oral cavity
Due to different electromagnetic
potentials of opposing metals
Saliva acts as electrolyte
Contact Short-circuit
current flows through pulp
Pain & Discomfort

74. Current falls off if fillings are maintained in contact
due to polarization of cell
Pain perception depends on patient sensitivity rather than
magnitude of current
Magnitude of current depends on composition & surface area
of metals

eg. Alloy of stainless steel develop higher current density than
gold or cobalt-chromium alloys when in contact with amalgam
Galvanism

75. Galvanism
As size of cathode (eg. gold alloy) increase relative to
anode (eg. Amalgam), current density increases
Larger cathode enhances corrosion of smaller anode
Current density in non-gamma2 containing amalgam is
less than gamma2 containing amalgam
Prevention :-
Placement of insulating base
Applying varnish on cavity walls
Proper planning of restoration

76. Estrogenicity
•Ability of a chemical to act in the body in a
manner similar to that of an estrogen.
•Bisphenol A –xenoestrogen may act on
estrogenic receptors in cells.
•E-screen assay –relies on growth response
of breast cancer cells that are estrogen
sensitive .

78. Summary
Clinical Guidelines for selecting
biocompatible materials :
Define the use of material
Define how the material has been tested
Think in terms of Risk & Benefit

79. Conclusion
Benefits Risks
Clinical
Judgement

80. References:-
1) Philips’ Science of Dental Materials
- Kenneth J. Anusavice
2) Dental Material Sciences
- Combe
3) Dental Materials – Properties & Manipulation
- Craig
4) Color Atlas of Oral Pathology – 4
th
Edition
- Robinson & Miller
5) Essentials of Oral Pathology & Oral Medicine
- Cawson & Odell

81. THANK YOU