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1. BIOCOMPATIBILITY OF RESTORATIVE MATERIALS
Dorlands Illustrated Medical Dictionary defines the term
‘BIOCOMPATIBILITY’ as “being harmonious with life and not having
toxic or injurious effects on biologic function”.
In general, biocompatibility is measured on the basis of:
 Localized cytotoxicity
 Systemic responses.
 Allergenecity.
 Carcinogenicity.
Based on these criteria, the requirements for dental material
biocompatibility include the following:
1) It should not be harmful to the pulp and soft tissues.
2) It should not contain toxic diffusible substances that can be released
and absorbed into the circulatory system.
3) It should be free of potentially sensitizing agents that are likely to
cause an allergic responses.
4) It should have no carcinogenic potential.
 Currently, a new document is being developed that
will meet international needs which is entitled “PRECLINICAL
1

2. EVAULATION OF BIOCOMPATIBILITY OF MEDICAL DEVICES
USED IN DENTISTRY – TEST METHODS”.
 In a broad sense, a BIOMATERIAL can be defined
as any substance, other than a drug, that can be used for any period as a
part of a system that creates/replaces any tissue, organ / function of the
body.
 Thus, when dentists purchase a material, they should
know if it is safe, and if it is safe, how safe it is relative to other
materials.
 To evaluate the biocompatibility of materials various
tests are carried out.
A BRIEF NOTE ON PULPAL REACTIONS
 Dentin protects the pulp and owes its vitality and its
sensitivity to stimulation of the dental pulp.
 This intimate relationship has far reaching clinical
implications.
 The nature of pulp reaction that follows peripheral
injury of the dentin.
1. Depends on the nature of causative
agent.
2

3. 2. Its proximity to the pulp.
3

4. i.e. Attrition; abrasion i.e. Progressive i.e Iatrogenic
and Erosion Dental caries Injuries
PULP
RESPONSE: Mild Irritation Severe Irritation May result in
- Reparative dentine - Inflammation - Inflammation
of pulp of pulp
⇒ As pulp inflammation can also be iatrogenic in origin “Do Not
Harm” is a basic principal that should be followed by all members of
the health profession; as it is ironic that in attempting to correct the
damage caused by dental caries.
- Iatrogenic pulp injury can develop:
1. during the preparation of a tooth for
restoration.
2. during the insertion of the restorative
material.
3. it can be due to inherent irritational
properties of the material; either
a. clinical components of the
material.
b. injurious products generated
during setting of the material.
⇒ PULPAL REACTION can also be caused by Bacteria
4

5. a. Either residual bacteria left behind in the cavity.
b. Or by the bacteria that gain access to the cavity after restoration as a
result of microleakage.
Before restoration; while cavity preparation, a simple rule should be
followed.
“NEVER CUT DRY”
1. Avoid heat generation
by the use of H2O coolant
2. Dentin dessication.
Coming to the restorative materials; depending on their chemical
nature can be grouped as:
MATERIAL RESTORATIVE
MATRIALS
NON-METAL
RESTORATIVE MATERIALS
1. Amalgam.
2. Direct Filling Gold.
DENTAL CASTING ALLOYS
3. Technique Alloy (Gold)
4. Base Metal Alloys
1. Different Restorative
Materials.
2. Acrylic.
3. Composite.
4. Porcelain.
1) Amalgam
 Conventional Amalgam Restorations are considered
inert / mildly irritating to the pulp.
5

6.  Mercury itself does not seem to contribute to any
pulp response.
 It was suggested that physical forces during insertion
of the amalgam is a major factors responsible for greater
responses rather than the toxic, chemical, or thermal properties
of amalgam.
 However, if reparative dentin is already present or if
a cement is placed prior to the insertion of the restoration there is
only little reaction to the conventional forces.
 SOREMARK and ASSOCIATES (1968) Showed
that Hg reached the pulp in humans after 6 days if no cavity liner
was used.
 The rate of diffusion of Hg into enamel and dentin
was inversely related to the degree of mineralization (It was
found that areas in dentin near the amalgam had a high Hg
content).
Thus older patients – there is less penetration of Hg ions.
Non-vital tooth – there is less even less penetration of Hg ions
(because the H2O component in E and D not reduced).
6

7.  It was found that, the discolouration of tooth was
caused by Zn / Sn and not Hg when it gets corroded (instead it
was found that Hg repenetrates the Amalgam and reacts freely
with previously unreacted alloy particles.
 HALSE (1975) confirmed these findings; using
human teeth.
 Lichenoid reactions representing a long-term effect
in the oral mucous membrane adjacent to Amalgam restoration is
quite often.
Buccal mucosa and lateral borders of the tongue.
 For many years a controversy has raged over the
biocompatibility of amalgam restoration because of the presence
of elemental Hg.
 The symptoms of chronic Hg poisoning (element)
are:
Weakness Insomnia
Fatigue Irritability
Anorexia Shyness
Weight loss Tremors in the extremities
 The signs and symptoms of methyl Hg poisoning
(sea food).
- Ataxia (gait disturbances).
- Paresthesia of extremities, lips and tongue.
7

8. - Constriction of visual fields (tunnel viscous).
 Few patients react to extremely small amounts of Hg
with the signs and symptoms of:
1. Mercury poisoning.
2. Multiple sclerosis.
3. Epilepsy.
Dentists diagnosed this condition as “MICROMERCURIALISM
HYPERSENSITIVITY”.
Accepted Hg levels:
Patient with amalgam – the over Hg level
- Normal 0.7ng/ml
Sea food per week
- 2.3 to 5.1ng/ml
2) DIRECT FILLING GOLD
 The pulp responses from the insertion of cohesive
and compacted gold are also associated with condensation,
whether with land instruments / with mechanical pneumatic
instruments.
 The responses develop when the condensation
occurs over freshly cut dentinal tubules, but not when dentinal
tubules are lined with pre-operatively formed reparative dentin
induced from previous episodes of disease / restorative
procedures.
8

9.  Apparently it was found that; DG that is compacted
properly into sound tooth structure produces only a minimal pulp
response.
 Under extremely rare conditions (1:1 million);
patients who have been sensitized to gold restorations with:
1. burning sensations.
2. lichenoid lesions of the oral mucosa.
3. generalized systemic reactions.
9

10.  8.5% of the female patients had presented:
a. lesions of oral lichen planus.
b. Burning mouth syndrome.
 Because of its (Ag) high thermal conductivity
patients experience POST-OPERATIVE SENSITIVTY. For a
woman, who reports that she is allergic to certain metals, the
following 3 options can be pursued if.
1) After a thorough medical history that includes questions on
dermatologic reactions to coins, jewellery / dental metals, we
can conclusively identify the ALLERGEN as the component
of a GOLD BASED / PALLADIUM BASED / BASE
METAL ALLOY (on trial basis).
2) If, the patient states that “she is allergic to gold alloy”; (this
situation is highly unlikely, because the incidence is less than
1% compared with an allergy potential of 10%for women to
Ni under extraoral conditions.
3) If, the patient c/o allergenicity to all metals and if out
examination fails to identify the most probable allergen, the
patient should be referred for medical diagnosis
(dermatologist / allergist).
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11. DENTAL CASTING ALLOYS
We have to select alloys based on individual patients specific,
functional, and economic requirements  There is no one alloy suitable
for all applications for e.g.: certain base metal alloys contain Be, Ni, Co
and Cr and the biocompatibility of each metal varies to different degrees of
tissue tolerance.
1) BERILLIUM : To date there have been no documented cases of Be
toxicity of dental origin.
- However, under uncontrolled conditions, when inhalation of
dust and fumes can be anticipated, the presence of Be
constitutes a recognized health hazard.
- It may result in
Acute form Chronic form
 Responses
vary from contact dermatitis
to severe chemical
pneumatics
 Symptoms
range from coughing, chest
pain and general weakness to
pulmonary dysfunction
11

12.  A high mortality rate of dental technicians was
found due to the inhalation of Be vapour – which resulted in
lung cancer and death.
 Therefore when grinding of Be containing alloys,
there should be adequate local exhaust ventilation.
2) NICKEL : Epidermiologic studies on workers in non-dental
industries have identified Ni and Ni compound as carcinogenic.
 The major hazardous route is aspiration.
 There is no experimental evidence that Ni
compounds are carcinogenic when administered by oral /
cutaneous routes.
 It causes dermatitis (contact) because it is a potential
sensitizing agent and in sensitized patients intra-orally.
1. Burning and tingling sensation during
the first 24 hours and
2. later exhibited a slight erythematous
reaction in the mucosa.
 However, there is no correlation found between the
incidence of Ni hypersensitivity and the presence intra-orally of
Ni alloy restorations.
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13.  Co alloys – have a potential for 1) dermatologic and
2) systemic effects that may result from patient and personnel
exposure to cobalt alloys.
 Although, allergic reactions may be of some
concern, the toxicity potential of Co-Cr alloys appear to be
insignificant.
 Palladium has also some allergic potential but
known patients of this metal allergy have not shown any reaction
in the mucosa, when a study was carried out.
NON-METALLIC RESTORATIVE MATERIALS
 A major cause of iatrogenic pulp injury is
“CHEMICAL IRRITATION” caused by Restorative Materials.
DCNA classified.
 The restorative materials into 3 major groups
according to their irritation qualities.
GROUP I GROUP II GROUP III
1) LOW
IRRITATIONAL
POTENTIAL
- Zn OE
- Polycarbo
xylate
- GIC
2) MODERATE
IRRITATIONA
L POTENTIAL
- Zn phosphate
3) HIGH
IRRITATION
AL
POTENTIAL
- Silicate
cements
- Resins
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14. GROUP I
ZINC OXIDE EUGENOL
 Has low irritational potential.
 Its pH, when freshly mixed is 7.
 ZnO and E have an-OBTUNDENT EFFECT on pulp.
 Eugenol inhibits the synthesis of prostaglandin (it should be
recalled that) are among the.
1) Chemical mediators of inflammation.
2) Contribute to pain sensation in areas of injury.
 HYGROSCOPIC QUALITIES OF ZOE may result in:
1) Withdrawal of fluid from the pulp through dentinal tubules.
[Thus relieving pressure on sensory nerve ending of the pulp].
 It has ANTIBACTERIAL property.
However; placed on an exposed pulp.
ZnOE – does not stimulate reparative dentinogenesis on the contrary; it
elicits a low-grade inflammatory response.
 The low irritational potential of ZnOE makes it ideal as a
negative control in studies that evaluate pulp reaction to restorative
material.
14

15. ZINC POLYCARBOXYLATE:
 It is remarkably INNOCUOUS despite a pH of 1.7 of the
polyacrylic acid liquid of the cement (this is due to the rapid rise of
the pH during setting of the cement).
 The large molecular size of the polyacrylic acid and its
 Tendency to form complexes with proteins would limit its
diffusion through the tissues.
 In this regard polycarboxylate cements are equivalent to ZOE
cements.
 POST-OPERATIVE sensitivity effects are negligible for
both cements.
GLASS IONOMER CEMENT
 The pulp response of GIC is bland.
 This blandness is attributed to the absence of strong acids and
monomers.
 Polyacrylic acid and related polyacids are weak and possess
higher molecular weights that may limit their diffusion through the
DT to the pulp.
 However studies of Pameyir and Stanley (1984) showed that
when anhydrous GIC was permitted to set:
15

16. 1. Under pressure (continuous) - simulating crown
cementation
2. pulp abscesses.
3. response occurred when RD thickness was 0.5nm /
less.
4. intense haemorrhage
 When the RDT was nearly 1mm – the set GIC caused a mean
inflammatory cellular pulp response of 1.67° which exceeded the
acceptable response level of 1.5° (Duralay study).
(Thus this study showed the importance of RDT in determining the
pulp response to GIC luting agents).
 GIC, appear to be pulp irritants only when used as luting
agents.
 Therefore it was recommended that small dab of CH be
applied only to areas of extensive crown preparations whenever
RDT was 1mm of the pulp before the cementation procedure was
carried out.
(This provided the required pulp protection to the critical areas without
decreasing the overall adhesion benefits of the GIC).
Lately, dentin adhesives that seal DT and infiltrate etched dentin
are being used in addition to CH.
GROUP II:
16

17. ZINC PHOSPHATE CEMENT
 It has an irritational potential intermediate to ZnOE and
silicate cement.
 As a base – it is not highly toxic.
 As a luting agent – on pressure, causes – a WIDESPREAD 3
– dimensional lesion involving all the coronal pulp tissue - as the
phosphoric acid within the mix of Zn phosphate cement is forced in
the DT and after ¾ days.
 An young tooth with wide – open DT is more susceptible to
such an intense inflammatory response compared to an older tooth
which has sclerotic / RD (that blocks DT and prevents the acids
from reaching the pulp).
 The pH of the cement 3 minute after mixing is 3.5; the pH
rapidly increases thereafter, approaches neutrality in – 24 hours.
Thus, damage to the pulp occurs during the first few hours after
insertion of the cement.
 This damage can be prevented by:
1. Application of appropriate varnish, DBA. Line thin
was of CH which eliminates 90% of the severity of
the adverse pulp response.
17

18. GROUP III:
SILICATE CEMENT
 It has high irritational potential.
 Being of its high-potential, it is used as an ideal material for
the control in studies that evaluate pulp reactions to restorative
material.
 The pH is below 3, at the time of insertion; and the pH
remains below neutrality even after 1 month.
 A CH base provides adequate pulp protection from quality of
the cement.
RESINS : (TOXICOLOGY)
 There is no indication that commonly used acrylic resins
produce systemic effects in humans.
 The amount of residual monomer in processed polymethyl
(methacrylate) is extremely low.
 The oral mucosa and underlying tissues function as barriers
that significantly diminish the volume of monomer reaching the
blood stream.
 Residual monomer that reaches the blood stream is rapidly
HYDROLYZED to methacrylic acid and excreted (It is estimated
18

19. that the half-life of methyl metacrylate in circulating blood in 20 to
40 minutes).
 Clinical experience indicates that true allergic reactions to
acrylic resins seldom occurs in oral cavity.
Theoretically, such reaction (toxic and allergic) could occur after
contact with the polymer, residual monomer, benzoyl peroxide
hydroquinone, pigments etc.
 The allergic reactions are dose dependent.
 The surface monomer is completely eliminated after 17 hours
of storage in H2O.
 Clinically, most patients reported denture-induced SORE
MOUTH which on evaluation indicates tissue irritation which is
generally related to unhygiene conditions / trauma caused by ill
fitting prosthesis.
 Repeated / prolonged contact with monomer may result in
CONTACT DERMATITIS.
 This condition is commonly experienced by dentists and
dental personnel involved in manipulation of acrylic resins.
 Because of this possibility, dental personnel should refrain
from handling such materials with ungloved hands.
19

20.  The high concentration of monomer in freshly mixed resins
may produce local irritation and serious sensitization of the fingers.
 Finally, inhalation of monomer vapour may be detrimental.
Therefore the use of monomer should be restricted to well ventilated
areas.
COMPOSITE RESINS
 This material whether conventional / microfilled;
autopolymerizing / photo activated (UV/VL) are found
IRRITATING to the pulp.
(a) CHEMICALLY CURED RESIN COMPOSITES:
 The addition of fillers to the direct filling, CCRC in the
1960s and 70s did not reduce their potential for creating severe pulp
responses.
 The filled resin; if not properly LINED, still cause
CHRONIC PULPITIS for an indefinite time even in cavities of
ordinary depth (Depth thickness of approximately 1mm).
 This potential for irritating the pulp persisted because CIRC’s
still required the use of matrix pressure to enhance adaptation to the
cavity walls during polymerization.
20

21.  The response of pulp to composite restorations may take
several days to 3 weeks to develop a massive pulp lesion.
 Some moderate to severe degrees of pulp response could be
expected no matter which proprietary CCRC is used.
 Thus, a thin coating of a hard-setting, Ca(OH)2 cement was
recommended for deep cavity preparations and over areas of all
freshly cut dentin before any composite material were placed.
Lichenoid reactions to Resin Based composites – on long-term
effect
(b) VISIBLE LIGHT CURED RESIN COMPOSITES
 It is important to obtain as complete a polymerization as
possible through the entire composite restoration to minimize pulp
response.
 The level of the pulp response in deep cavity preparations is
more because more chances of incomplete curing of the resin which
permits an even higher concentration of residual unpolymerized
monomers to reach the pulp.
 A question can be raised now “which component of
composite elicits pulp injury?”
21

22.  In a study of pulp reactions to 8 components of composite
resins, none of the components tested elicited significant pulp
injury.
 It appears likely that reactive radicals generated during the
polymerization of the resin are responsible for pulp injury.
 Pulp injury by resin restorations can be totally abrogated
through the application of a hard setting Ca(OH)2 base beneath the
resin.
 With proper light curing technique with incremental layering
composite that were previously quite toxic to the pulp have become
less so with the elimination of the need for matrices and pressure to
gain acceptable adaptation.
CONDITIONING (ETCHING) AGENTS
 As the resin restoration leak badly, acid etch technique was
developed to:
(a) Improve marginal seal between cavity and
restoration.
Acid etching of enamel is safe.
1. Provided a protective base of Ca (OH)2 is applied over
exposed dentin prior to etching.
22

23. Acid etching of dentin:
1. Markedly increases its permeability.
2. Removes the amorphous smear layer over cut dentin
(which plugs the orifices of the DT).
3. It demineralizes the peritubular dentin resulting in
increased tubular diameter. Such patent tubules
provide easy access of irritants to the pulp.
- Studies suggest that only the surface of the dentin 10-µm
depths) needs to be modified and not its deeper layers.
Conditioning techniques that are associated with weaker
acids, shorter periods of application, and the elimination of
rubbing and scrubbing procedures produce a minimal pulp
response and satisfactory bonding.
BONDING AGENTS
 Bonding agents do not appear to be toxic.
 Between 1975 and 1992, some studies demonstrated that
bonding agents helped.
1. Reduce the expected pulp responses induced by the
subsequent placement of the more toxic resin-based
composite materials.
23

24.  Lee pharmaceutical cooperation in 1975
- had produced an “ADHESION BOOSTER” (used either
alone with enamelite, a resin composite / in conjunction with
50% phosphoric acid) that reduced the pulp responses, even
though the acid evidently removed the smear layer and
opened the tubules.
 The resin primer is applied that infiltrate the demineralized
dentin surface (smear layer and tubules) and the exposed collagen
mesh to form a hybrid layer. On this layer a bonding resin is placed
and cured. This plugging of the DT’s prevents the penetration of
toxic components to the pulp from subsequently placed resin-based
composite restorations.
RESIN BASED COMPOSITE CEMENTS (DUAL-CURE):
In 1992 Pameyor and Stanley, found that:
 Only when the dual-cure resin cement received no visible
light energy did the average pulp response level exceed the accepted
level of biocompatibility and resmbled pulp responses similar to
CCRC’s.
 The increase exposure time to visible light is not harmful to
pulp tissue.
24

25. CAVITY VARNISH AND LINERS
 Cavity varnish produces a positive effect on the reduction of
pulpal irritation.
 This effect is because of the reduced infiltration of irritating
fluids through marginal areas.
 The varnish also prevents penetration of corrosion products
of amalgams into the D.T.
 It cannot be used under composite and GIC restoration.
 Cavity liners like Ca(OH)2, GI and ZOE are used for
accelerating the formation of reparative dentin in deep cavities.
LUTING CEMENTS AND THEIR APPLICATIONS
1) For retentive small single tooth castings / 3-unit FPD’s.
 Polycarboxylate (has minimal pulp irritation and lack of
postoperative sensitivity).
 ZnP, GIC, IRM.
2) Long span FPD’s – Zn phosphate / GIC.
3) Sensitive teeth relieving cast restoration – Zn polycarboxylate /
RZOE (blandness).
25

26. 4) Cast restoration in extremely caries active patients – GIC (cause of
F released through the postoperative sensitivity.
5) Porcelain veneers / inlays – Resin cements and liners.
6) Porcelain JC / Dicor – ZnP / Resin – Non irritation to pulp and
sufficient strength and added colour
7) P and C cementation – GIC (Increased strength anticariogenic and
increased flow).
8) Continually dislodged cast – GIC / Resin (with protect).
9) Castings cemented in a wet field – reinforced ZOE (lack of
sensitivity to moisture).
PROTECTIVE BASES
-Ideal bases should be well:
1) Tolerated by the pulp.
2) Should stimulate reparative dentinogenesis. (in case an undetected
microscopic exposure of pulp exists).
3) It should provide adequate protection of the pulp from irritant
component of the restorative material.
4) Abundant effect.
26

27. 5) Antibacterial (to eliminate bacteria in residual carious dentin when
used with IPC).
6) Adequate compressive strength (to withstand forces incident to the
condensation of the material).
7) Low thermal and electric conductivity (to protect the pulp from
thermal shock and electrogalvanism).
8) Should exhibit low acid – solubility and etch tend (in case if the acid
comes in contact with the material).
For i.e.
1. For metallic restoration like amalgam.
a. A hard setting Ca(OH)2 and
reinforced ZOE.
2. For DGF
a. Zn phosphate cement will provide a
stronger base, however; Ca(OH)2 liner /
cavity varnish should be applied prior to
the insertion of the cement – to protect
the pulp from chemical irritation.
PULP CAPPING (In Deep Cavities)
 Numerous materials have been investigated as pulp capping
agents.
27

28.  However, Ca(OH)2 preparations have best withstood the test
of time.
 There has been a widespread concern among dentists that
Ca(OH)2 events a persistent stimulating effect on the pulp that
results in eventual obliteration of pulp.
 Some also believed that it causes persistent inflammation of
the pulp.
 The exact mechanism by which CH generates a dentinal
bridge is not clear but its.
Caustic action associated with its high pH (11 to 13), when
solubilized and its reduction of superficial necrosis.
Were assumed to be the factors responsible for stimulation of
secondary dentin formation.
MICROLEAKAGE
 Brannstrom and colleagues (1971; 74) have proposed that
infection caused by penetration of microorganism from marginal
leakage around the restoration.
 And the residual microorganisms left on the cavity floor
cause a greater threat to the pulp than is the toxicity of
restorative material.
28

29. When cavities are deep – Bacteria + Irritation potential of
restorative materials are responsible for pulpal irritation.
 Bergenholtz (1982) pointed out that although
microorganisms may contribute to pulp responses beneath
reactions; they appear to be unable to sustain a long-standing
irritation to the pulp.
 Unless recurrent caries develops under a clinically –
defective restoration; the dentin permeability to bacteria
decreases over time, allowing the pulp to heal.
 This may partially explain why pulp remain VITAL in most
restored teeth.
 Consequently pulp devitalization occurs due to:
1. Mechanical injury during cutting.
2. Toxicity of restorative material.
3. Action of bacteria.
 Earlier high irritating solution were used for sterilization of
the cavity.
 But the need for cavity sterilization is questionable.
Because:
1. Dentin has shown to resist bacteria invasion.
2. and deep cavities are usually given a protective base
of Ca(OH)2.
29

30. Both of which have shown ANTIBACTERIAL
PROPERTIES
 A safe and effective measures for cavity cleansing is simply
rinsing the cavity with warm H2O.
30