Biological properties of dental materials /certified fixed orthodontic courses by Indian dental academy

Biological
properties of
Dental
materials.
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents





Introduction
Biocompatibility v/s Biological properties
Components of biocompatibility
Adverse effects of dental materials











Local & Systemic effects of materials
Key principles that determine adverse effects from materials
Concept of Immunotoxicity
Oral anatomy that influences the biological response






Toxicity
Inflammation
Allergy
Mutagenicity
Carcinogenicity

Enamel
Dentine & Pulp
Bone

Measuring the biocompatibility





Invitro tests
Animal tests
Usage tests
Clinical trials








Advantages & disadvantages of biocompatibility tests
Correlation among the tests
How tests are used together ?
Regulatory standards for measurement of biocompatibility
Current biocompatibility issues in dentistry
Reaction of pulp to different materials










Latex
Impression materials
Biocompatibility of metals
Reaction of other oral soft tissues to restorative materials







Dentine bonding & Dentine bonding agents
Dental amalgam
Dental cements
Bleaching agents

Denture base material
Soft denture liner & adhesives

Reactions of bone & soft tissues to Implant materials
Conclusion
List of references

Introduction


Biological properties of Dental
materials







Biocompatibility = Lack of interaction
Biocompatible material = list of negatives
 Non degradable
 Non irritant
 Non toxic
 Non allergic
 Non carcinogenic
 Non mutagenic
Total inactivity = Passive ignorance ?
More appropriate – active acceptance
Biocompatibility : ability of a material to perform with an
appropriate host response, in a specific application.

Components








Initial Physiochemical interaction
Effect of the tissue environment
Local host response
Transport of products – Systemic effects
 Establishment of solid-liquid interface as any material is
implanted into the tissue
 Protein absorption is the first event
Immediate response to injury is inflammation
Very few is know about the factors
 Condition of the host
 Properties of the material
 Context in which the material is used
Eg: Biocompatible as Crown & Bridge but not as an implant material

Adverse effects from Dental
materials


Toxicity



Placement of a foreign material in the body carries the possibility
of toxicity
Toxicity can be of 2 types
 Acute toxicity.
 Chronic toxicity.








Type 1: requires prolonged or repeated administration
Type 2: requires very few or one dose but long lasting effects

Type 1 chronic toxicity is a possibility with “Biomaterials”
Eg: metal ions released by gradual corrosion of an implant
According to J.J.Jacobs et al (1991)
 Vanadium – lungs
 Aluminium – surrounding tissues
Fortunately, materials causing over toxicity are no longer used in
dentistry.

Inflammation





May result from toxicity or allergy and often it
precedes toxicity.
Oedema, inflammatory cell infiltrate
Current biocompatibility research

Allergy


Allergy




Body specifically recognizes material as foreign &
reacts disproportional to the amount of material
Gell & Coomb’s classification of immune responses







Type 1: Atopic or anaphylactic reaction
Type 2: Cytotoxic hypersensitivity reaction
Type 3: Immune complex disease
Type 4: Delayed or cell mediated hypersensitivity
Type 5: Stimulating antibody reaction
Type 6: antibody dependent, cell mediated Cytotoxic
reaction







Type 1, 2, 3 – quickly. Eosinophils, Mast cells & B
lymphocytes
Type 4 – delayed. Monocytes & T cells
Allergic response – individual’s immune system
recognizes a substance as foreign
Allergic reactions – initially dose independent,
disproportionate
Toxic / inflammatory reactions – dose dependant,
proportionate


Mutagenic reactions



Alteration in base pair sequence (mutation)
2 types







Alteration in cellular process that maintain DNA integrity
Direct interaction

Can occur from radiations, chemicals, errors in DNA
replication process
Examples




Metal ions – nickel, copper, beryllium
Few components of root canal sealers
Resin based materials to some extent

Carcinogenic response




Currently no dental material has been shown to be
carcinogenic for dental applications in patients
However, carcinogenesis is often exceedingly
difficult to prove or disprove conclusively

Local & Systemic effects of
materials


Local effects







Pulp
Periodontium
Root apex
Oral tissues – buccal mucosa, tongue

Systemic effects


Function of the distribution of substances released from the materials






Access to the body by







Simple diffusion
Lymphatics
Blood vessels
Ingestion & absorption in gut
Inhalation
Release at tooth apex
Absorption into mucosa

Systemic response depends on




Duration & concentration of the exposure
Excretion rate of the substance
Site of the exposure

Key principles that determine
adverse effects from materials


A) various types of metal corrosion & other types of
material degradation :



Biocompatibility depends on the degradation process
Corrosion is determined not only by material composition
but also by the biological environment

Many ways for release of products in host






Metal prosthesis – releases metal ions by
 Electrochemical force
 Particles dislodged by mechanical forces
Resin composites
 Cyclic stresses
 Salivary esterases



B) Surface characteristics :





Surface is quite different from interior
Examples
 Dental casting alloy containing 70% gold may have 95%
gold at its surface
 Relative unpolymerized state of a sealant at its surface
The surface composition, roughness, mechanical &
chemical properties are critical to the biocompatibility


Concept of
Immunotoxicity


Concept of Immunotoxicity
“ Based on the principle that small alteration in
the cells of immune systems by materials can
have significant biological consequences ”
 Examples:




Mercury ions increase the Glutathione but
Palladium decreases Glutathione content of
Monocytes
HEMA may change the ability of Monocytes to
direct an immune response once challenged by
plaque or others agents

Oral anatomy that influences
the Biological response


Enamel : “seals” the
tooth




Peroxides permeate
intact enamel

Dentine & Pulp :





Smear layer
Effective in reducing the
hydrostatic pressure but
not diffusion
Acid etching



Bone : Osseointegration & Biointegration


Osseointegration







Implant & bone closely approximate to each other
Approximation less than 100 A
No fibrous tissue in intervening space
Titanium alloys

Biointegration
Implant & bone are fused to one another & are
continuous
 Occurs with Ceramic & Ceramic coated metal
implants
Eg: Calcium & Tri calcium phosphate, Hydroxyapatite,
Bioglass



Measuring the Biocompatibility




Is not simple and methods of measurement are
evolving rapidly as more is know about the
interactions between dental materials and oral
tissues & as technologies for testing improves
Classified as





In Vitro test
Animal test
Usage test
Clinical trial – special case of a usage test in humans


In Vitro test


Placement of a material
or component of it in
contact with cell,
enzyme or some other
isolated biological
system




Direct
 Material in contact
 Physically present or
extract from material
Indirect
 Some sort of barrier

Types of cells used in In-vitro
assays


Primary cells :





Directly from an animal into culture
Grows for only a limited time

Continuous cells :


Primary cells transformed to allow them to grow
indefinitely


Testing procedures & extent of
testing



Manufacturer’s responsibility to test new material
A) Initial tests :deals with general biocompatibility & systemic
effects of a material
 Short term systemic toxicity test





Acute systemic toxicity test




Dental remedies that have significant volatility under usage condition

Hemolysis test




I.V administration

Inhalation toxicity test




Short time oral administration
Toxicity profile

In vitro evaluation of hemolytic activity of materials intended for
prolonged tissue contact

Emes mutagenicity & the dominant lethal test


To asses the potentialwww.indiandentalacademy.com
carcinogenic activity

Cytotoxicity tests


Measures cell count or growth after exposure to a
material




Method 1 :
 Place the cells in the well of a cell culture dish
 If Cytotoxic - cell may stop growing, exhibit cytopathic
features or detach from the cell
Method 2 :
 Measurement of cytotoxicity by a change in membrane
permeability
 Loss in membrane permeability is equivalent or very nearly
equivalent to cell death
 Identifies the cells that are alive or dead

Tests





Sensitization test
Oral mucous membrane irritation test
Subcutaneous implant test
Bone implant test


Usage tests


Pulp &Dentine test






Pulp capping & Pulpotomy test
Endodontic usage test





Response of dentine & pulp
Minimum experimental variables

Assess response of the pulp wound & the periapical tissue
Influenced by – level at which the pulp tissue is cut off &
total removal of pulp tissue

Bone implant usage test


To evaluate all materials that, during their intended use,
penetrate the oral mucosa and the adjacent bone

Correlation among the tests





Lack of correlation
Less prominent biological response
Barriers may exist
Measure different aspects of the biological
response to the material


Advantages & disadvantages
of Biocompatibility tests


In-Vitro test


Advantages








Quick to perform
Least expensive
Standardized
Large scale screening
Excellent for mechanisms of interaction

Disadvantages


Relevance to In-Vivo questionable



In- Vivo test




Advantages
 Allows complex systemic interactions
 More comprehensive
 More relevant
Disadvantages
 Relevance to use ?
 Expensive
 Time consuming
 Ethical concern
 Difficult to control
 Difficult to interpret & quantify




Usage test


Advantages




Relevance to use of material is assured

Disadvantages




Very expensive
Time consuming
Major legal / ethical


How the tests are used together
to measure the Biocompatibility

usage
secondary

primary





progression
of

testing

Linear paradigm, relies on the accuracy of the primary tests (challenged by
Major et al 1977)
No prediction of results in usage tests
Lack of correlation in In-Vitro tests



Non linear thinking
U
S
P




Progression
of
Testing

All the 3 tests are done
As test progresses Usage test predominates



Most common progression

Usage
Primary

Secondary


‘Recognizes
complexity’

Standards that regulate the
measurement of Biocompatibility


ANSI / ADA : earliest attempt in 1933





1972 – The Council on dental material,
instruments & equipment of ANSI / ADA approved
document no. 41 for recommended standard
practices for biological evaluation of dental
materials
In 1982 updated to include test for mutagenicity
Uses linear paradigm



ISO Standard 10993 :





Not restricted to dental materials only
First published in 1992
In 2002 ISO 10993 consisted of 16 parts
2 types of tests –




Initial – Cytotoxicity, sensitization & systemic toxicity.
In – Vitro / animal test
Supplementary – chronic toxicity, carcinogenicity &
bio-degradation. Animals / Humans
Specialized tests – Eg: dentine barrier test


Current Biocompatibility
issues in dentistry





Reactions of pulp to
different materials
Micro leakage :





If a material does not
bond or debonds at
enamel or dentine
Previous belief
Concept of nano leakage




Between mineralized
dentine & bonded
material. In very small
spaces of
demineralized matrix
into which material did
not penetrate
Hydrolytic degradation
of dentine – material
bond



Dentine bonding :






Bonding to dentine is
difficult – composition,
wetness, low minerals
Smear layer formation &
removal
Many studies have
shown
 0.5mm of RDT is
adequate
 Dentine is a buffers of
protons
 Penetration of acids <
100 micrometers



Dentine bonding agents :




HEMA is 100 times less cytotoxic in tissue culture
than Bis – GMA
Bis – GMA, TEGDMA, UDMA


Amalgam




Dental amalgam :





Toxic or not ?
In usage test response of
pulp to amalgam in shallow
or deep lined cavities
Gallium based amalgam






Excessive gallium release,
roughness, discolor
Significant foreign body
reaction

Absorption : 1 – 3
micrograms / day
Minimum dose to produce
observable toxic effect is 3
micrograms / kg body
weight



Dental cements



Resin based materials :








Resin composites –
luting or restorative
Light cured < cytotoxic
than chemically cured
Pulpal reaction
diminishes after 5 – 8
weeks
Protective liner or
bonding agent minimizes
Pulpal reaction



Glass ionomers :






Luting agent &
restorative material
Weaker polyacrylic acid
Fluoride release
Histological studies in
usage test shows that
any inflammatory
infiltrate to ionomer is
minimal or absent after 1
month




Zinc phosphate :







Luting agent & base
Thermal conductivity closer
to enamel
Pulpal damage in first 3
days due to initial low
PH(4.2), reaches neutrality
in 48 hours
When placed in deep
cavities ?
Inclusion of Ca- OH to the
powder or lowering the
concentration of phosphoric
acid




Calcium hydroxide :
Suspension form

Resin containing

Highly cytotoxic

Mild to moderate cytotoxic

Necrosis 1mm or >

No necrotic zone

shortly

Neutrophil infiltration

Dentine bridge formation
is quick

5 to 8 weeks

Slight inflammatory response
wks - months

Dystrophic calcification
Dentine bridge



Zinc oxide eugenol :





Suppresses the nerve transmission
Inhibit synthesis of Prostaglandins & Leukotriens

Hammesfahr 1987, initiated the search for a
biocompatible resin base system incorporating
Calcium hydroxide “ PRISM VLC DYCAL”

Soft tissue response to the
luting cements


Apply petroleum jelly



Clean the excess



Any residues of cement




Bleaching agents :







Usually contain some form of peroxide
In-Vitro – traverses the dentine & in sufficient
conc. can be cytotoxic
Penetrates intact enamel & reaches the pulp in
few min.
May burn gingiva

Latex



Latex :




6% to 7% of surgical personnel may be allergic
42% adverse reactions to occupational materials
Hypersensitivity may be due to true latex allergy or reaction
to accelerator & antioxidants
White, milky sap
Addition of ammonia

Hydrolyses & degrades the sap proteins to produce allergens


Liquid
latex




vulcanization
sulphur + heat

solid
rubber

Soaked in hot water leaches out allergens
Allergenicity depends on collecting, preservation
& processing


Impression materials









Impression materials :
Price & Whitehead
(1972) – Allergic
contact stomatitis &
Foreign body response
Sydiskis & Gerhardt
(1993) – some degree
of toxicity in cell culture
Gabriela Mazzanti et al
(2005) – no significant
evidence of diffuse
inflammation or local
skin reaction


Casting alloys




Dental casting alloys :
John c. Wataha 2000





Release of elements is essential for adverse effects
Identifying & quantifying the elements that are
released is most relevant measure from stand point of
Biocompatibility

a) Release of elements from casting alloys
Multiple phases
 Inherent tendency to release elements – lability
Eg: Cu, Ni, Cd, Zn & Ga – highly labile
 Environmental conditions - PH





b) Systemic toxicity






Released metals may not be inside the body
Route of access – I.V < Peritoneal < Oral
Distribution – there is no documented proof that
these material cause ‘Systemic toxicity’

c) Local toxicity




Micro environment exists around casting alloys
Metal ions can cause local toxicity
Increased exposure causes increased toxicity



d) Allergy to dental casting alloys




Elemental release is essential for allergy
Metal ions – Haptens
Allergy & Toxic reaction – difficult to distinguish




Patch test for metals – controversial
Application of metal ion to skin in the form of patch
 Injecting small amount of ion below the skin
 Assessment of the response is difficult
 Salt of metal ions important for response
Eg: chloride, sulphate, nitrate salts
 Vehicle – whether its water, oil or petrolatum can vary
the response




Grimaudo N.J 2001 – true allergic hypersensitivity to
dental casting alloys is rare



Nickel :








Common component
Incidence of allergy 10% – 20%
Cross reactivity between nickel & palladium (33%
& 100%)
Nickel ions induces ICAM’s in the endothelium –
release of cytokines
It may contribute to any intraoral inflammation
around nickel containing crowns




Beryllium :





Used in Ni-Cr alloys in conc. of 1 – 2 wt%
Forms thin adherent oxides
Documented carcinogen
Berylliosis



Individual is hypersensitive
Inhalation of beryllium dust, salts, fumes

Reaction of other oral soft tissues


a) Denture base
materials







Methacrylates
Greatest potential for
hyper sensitization
Acrylic & diacrylic
monomers, curing
agents, antioxidants,
amines, formaldehydes
For the patients most of
these materials have
been reacted in
polymerization and thus
less prone



True allergy of oral mucosa to denture base
material is very rare



Residual monomer (methyl methacrylate)



Allergic acrylic stomatitis



Heat cured is better



b) Soft denture liners &
adhesives






Release of plasticizers
Extremely cytotoxic
Effects are masked by
the inflammation
Denture adhesives show
severe cytotoxic
reactions In-Vitro
 Large amount of
formaldehyde
 Allowed significant
microbial growth

Denture cleansers


Used to cleanse the prosthesis




Eg : Hypochlorite, mild acids, etc.

Biocompatible & cause no harm to the patient


Artificial teeth



Acrylic & Porcelain teeth



Acrylic teeth is preferred in poor ridges


Implants

Reaction of bone & soft
tissues to implant material



Materials – Ceramics, Metals, Carbons & Polymers
a) Reaction to ceramic implant material







b) Hydroxyapatite





Very low toxic effects. Oxidized state, corrosion resistant
Used as a porous or dense coating
Root surface porosities > 100microns (firmly bound )
Root surface porosities < 100microns (fibrous ingrowth)
Relatively non resorbable form of calcium phosphate
Coating material & ridge augmentation material

c) Beta -Tricalcium phosphate


Another form of calcium phosphate, has been used in
situations where resorption of the material is desirable



d) Reaction to pure metals & alloys











‘Metal’ oldest type of oral implant material
Shares the quality of ‘strength’
Initially selected on the basis of the ‘Ease of
fabrication’
Stainless Steel, Chromium-Cobalt-Molybdenum,
Titanium and its alloys
Most commonly used is Titanium
Titanium’s Biocompatibility is associated with its
fast oxidizing capacity.
Corrosion resistant & allows Osseointegration



Soft tissue :




Epithelium forms bond
with implant similar to
that of tooth
C.T apparently does not
bond to the titanium, but
forms a tight seal that
seems to limits ingress of
bacteria & its products


Conclusion


List of references














Restorative dental materials by Craig & Powers
Phillips’ Science of dental materials
Chemistry of medical & dental materials by J.W.Nicholson
Concise Encyclopedia of medical & dental materials by David Williams
Dental biomaterials by Arturo N. Natali
Dent material 2005;21(4):371-74
JPD 2001 Aug;86(2):203-9
Gen Dent 2001 Sep-Oct;49(5):498-503
JPD 2000 Feb;83(2):223-34
JPD 1998 Sep;80(2):203-9
JPD 1993;69;431-5
J Biomater Appl 1987 Jan;1(3):373-81
BDJ 1972;133:9-14


Precautions to be taken in the
Lab








Make certain the ventilation system in room
is properly functioning
During operation of the dental lathe wear a
protective eyewear & a mask
Clean & disinfect the dental lathe at least
once daily
Use sterile rag wheels, stones & fresh
pumice for each patient's prosthesis

Thank you
For more details please visit


Biological properties of dental materials /certified fixed orthodontic courses by Indian dental academy

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Andere mochten auch

Andere mochten auch (20)

Ähnlich wie Biological properties of dental materials /certified fixed orthodontic courses by Indian dental academy

Ähnlich wie Biological properties of dental materials /certified fixed orthodontic courses by Indian dental academy (20)

Mehr von Indian dental academy

Mehr von Indian dental academy (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Biological properties of dental materials /certified fixed orthodontic courses by Indian dental academy