Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.

1. T 3 days the response ranges from slight to moderate; at 5 and 8 weeks the
inflammatory process is slight and a zone of reparative dentin has formed underlying the
cavity. Inflammatory cells may still persist at the later time periods, presumably because
of stimulation caused by the continued release of some calcium ions. Typical responses
are shown in Figs. 7-11 and 7-12.
One function of calcium hydroxide liners is to serve as a contact dressing
in the event of exposure of the pulp. At.3 days the response of an exposed of the pulp to
calcium hydroxide may range from slight to severe, and these same responses may be
maintained at 5 and 8 weeks. The reason for the range or response to various Ca (OH)2
compounds is that the cement may be in a water-soluble form or the solubility may be
restricted by the cement bin compounded in a resin. Formulations using a water-base
carrier of calcium hydroxide may cause a zone of necrosis adjacent to the compound.
Beyond the zone of necrosis, healing occurs and a dentinal bridge forms (Fig 7-13 A).
The resigned salicylate Ca (OH)2 liners stimulate healing with no zone of necrosis;
therefore dentin is laid down adjacent to the liner (Fig 7-13 B) an indication that the
formative cells, the odontoblasts, began forming dentin in contact with the liner. Calcium
gydroxide is the most effective liner now available for treating pulp exposures with
subsequent formation of a reparative dentin bridge. Adder exposure the pulp organ goes
through a relatively uncomplicated wound-healing process in manner similar to that of
skin if the tissue is not infected. Usually in a deep carious lesion the Helen process is
complicated by the presence of bacteria. When a pulp is exposed, hemorrhage initially
occurs and a blood clot forms at the expenses of the connective tissue at the site. Healing
then progresses with resolution of the clot by homeless, and proliferating fibroblasts of
dentin. The resin-filled Ca (OH)2 liners offer a major advance in pulp-would
management. Healing takes place with minimal inflammation, and reparative dentin
forms at the initial site of exposure with minimal loss of pulp size (Fig.7-13,B) There is
evidence that these materials break down in time and create a gape between the rest
ration and the cavity wall.
Varnishes.
Numerous investigators have analyzed the effects of the application of
“thin layer” liners such as copal varnishes and polystyrenes under silicates and zinc
phosphate cements. These liners are used in such thin layers that they do not provide
thermal insulation, but they serve to isolate the tubule contains from the cavity. They also
inhibit penetration of bacteria of chemical subnstancex resulting from the setting of a
restoration. They should prevent penetration of components of amalgam into dentin and
reduce marginal leakage. Several applications may be nbeccssary to prevent penetration
of bacteria or acids
Composites. Chemically accelerated composites placed in cautious with
approximately 0.5 mm of remaining dentin generally show a moderate response ate 3
days (Fig 7-14.) The response to ultraviolet (UV) accelerated composites after 3 days is
moderate to slight. The milder response to the UV-accelerated materials may be a result
of the lack of chemical acceleration, which provides fewer chemicals to affect the tissue.

2. The inflammatory response diminishes as the postoperative time increases to 5 to 8
weeks, with an increase in the quantity of reparative dentin. The response to both
chemical-and UV accelerated composites cause reparative dentin to from underlying the
cavity floor. This dentin appears to be regular, containing dentinal tubules and few if any
cell inclusions (Fig.7-15) Because of the moderate initial response to these materials, it is
recommended that a protective line such as calcium drooled be used. With a liner, the
pulp response to the composite system is minimal.
Amalgams. Since amalgam is the most commonly seed restorative
material, the pulpal response it produces has received a great deal of attention.
Investitures agree that in cavities of average depth, the pulp is affected mainly by the cold
and hot stimuli that result from the thrall conductive properties of the amalgam. In deep
cavities, pain is a characteristic of unlined cavities and 5 weeks. Aspiration of
obontoblasts into dentinal tubules underlying the cavity has en seen. The response to
amalgam is minimal in shallow cavities. There is a significant difference in pulpal
response in the unlined cavity and those lined with cluclum hydroxide, sine oxide-
eugenol, or varnishes. Several reasons are advanced for the presence of pulpal damage
soon after the placement do an unlined amalgam. Marginal leakage has been reported to
cause some damage to the pulp after the placement do amalgam restorations. The
margins of newly placed amalgam restorations show significant microleakage (Fig.7-16)
In summary, puple response to silver amalgam restorations occurs shortly after their
placement and is probably a result of cavity preparation and marginal leakage. Leaching
of toxins from amalgams that may penetrate dentin is dependent on the size o the
molecules and the patience of the tubules. There is a significantly improved response
when the cavity is lined, and the patebct if the tubules. There is a significantly improved
response when the cavity is lined, and the amalgam rarely causes irreversible damage to
the pulp.
A number of silver amalgams with high copper contents are currently in
clinical use. These have been introduced because their resistance to corrosion and creep
is higher than that for the conventional silver amalgams containing the y2 phase. At 3
days the pulpal responses elicited by these highcopper amalgams appeared similar to
those of conventional amalgams in unlined cavities. At 5 weeks they elicited only slight
pulpal response. AT 8 weeks the inflammatory response was again reduced.. bacterial
tests on the high-copper amalgam pellets revalued little inhibitory effect on stereotypes of
S. Mutants, which indicates that the elements are firmly incorporated in the amalgam and
thus unlikely to be released into the oral environment. Although the newly introduced
high-copper amalgams appear to be biologically acceptable, it is suggested that liners be
used in all deep cavities.
Gold. Cast gold restorations very widely in size because of tooth-
coverage requirement . it has been said that pulp reaction to cast gold crowns is a
dressily of the type of cement used to retain the restoration. In shallow cavities Sine

3. phosphate cement serves to stimulate reparative dentin. In deep cavities the pulp should
be protected from the zinc pjhospjhate cement mix because of the free acid available, as
discussed previously. The pulp responds more favorable to the improved zinc
oxideeugenol cements.
The condensation of cohesive gold is a factor in pulp response. A
moderate to severe inflammation was reported at 10 to 20 days, but after 35 days spoons.
Condensation of gold thus causes a short-term severe response that stimulates reparative
dention formation. If a base is required, pulpal inflammation is reduced. There are no
irreversible changes, and the use of cohesive gold thus causes a shortterm severe response
that stimulates reparative denotation is reduced . there are no irreversible changes, and
the use of dchoesive gold may be considered biologically sound. Among all restorations
evaluated, gold foil showed the least marginal leakage; however, the leakage does not
decrease with age.
Usage tests on inflamed teeth
Pulps used for the testing of dental materials are usually normal
(noninflamed ) pulps from intactnoncarios teeth. There is concern that liners, cements,
and restorative agents will respond differently to an inflamed rather than a normal pulp.
After all, this is the situation in which most materials must function in human teeth. To
gain information about this factor, a number of investigators have propose developing a
model of inflamed teeth for testing these materials. The several methods proposed are as
follows (1) soft carious dentin from freshly exrtracted human teeth is placed in the floor
of cavities and covered with cment for 4 to 7 days (Fig 7-17) (2) a gutta-percha
temporary filling is placed in the cavity for 4 to 7 days, or (3) the cavity is left open to the
oral enviroment for 4 to 7 days. Days . After this time the carious dentin or gutta-percha
is removed, the the cavities are dried with cotton pellects. And the test material is placed
on the floor of the cavity and sealed with amalgam. The carious dentin produces a sever
localized pulp reaction the gutta-percha causes a slight to moderate one, and the open
cavities produce varied responses. Thus the carious dentin and gutta-percha rechnics are
the ones widely used today in animal research to produce pulpitis before a material is
tested. Efforts have been made to quantify and qualitfy the technic of bacterial insult.
For example, recent studies in which 1 u1 each of lactobacillus casei and Streptococcus
mutans were sealed in cavities resulted in sevr pulpitis in soe cases and less in others.
This variability in response has resulte in the continued use of human carious dentin.
A further advanc in technology is the use of a Brown and Bren stain for
determining the presence of bcteria. This stain clarly demonstrates the personce and
location of both gram positive and gram-begative bacteria after routine histological
preparation. Thew presence of bacteria in the dentinal tubules an dpulp can be corrclated
with pulp response. Serapings from a cavity can also be cultured by routine
microbiological procedures to ascertain the presence and identity of bacteria at the site.

4. The use of the inflamed pulp in the evaluation of dental material is gaining
popularity since this closely resembles the situation in which thse materials will be used
in man. Not onl is the pulp evaluated, but also the type of reparative dntin. The pulp
evaluated, but also the type of reoaratuve debtin. The idealk response is regular tubular
dentin. Other types of irregular entin may form that may contain few tubules or
osteodentin or a combinatiuon of these (Fig 7-18) irregular dentin or osteodentin with cell
inclusion indicates a more severe response to the dental material.
GINGIVAL RESPONSE
Since usage tests in man and animals are carried out at sites that are
appropriate for their intended use, various dental materials have been placed in
subgnigival cavities and the response of the gingiva evaluated in manner similar to pulpal
eveluations. One of the difficulties of this type o study is nthe normal presence of some
degree of inflammation in the giviva. To avoid this condition, a prophylaxis is performed
before the cavity preparation and placement of the material in a sunbgingival cavity. It
has been shown that bacterial plaque is the most important factor in gingival
inflammation, and surface roughness of the restorative material, open or overhanging
margins, plaque accumulation retained by rough surfaces or marins is also an important
factor.
Operative Procedures
Trauma caused by rotatidng instruments is a reversible condition. Even
prophylaxis with a rubber cup and pumice will cause loss of the sulcal epithelium, which
will beal completely in 8 to 14 days. If subgingival margins exist, inflammation may
occur ;and time for healing must be allowed before assessment of the effects of the
restorative ageents is made. It has been suggested that subgingival is made. It has been
suggested that subgingival cavity preparations be raised to a level even with the crest of
the gingiva since this causes the least inflammatory response. Even the best operative
procedures produce some degree of gingival margins. Before restorative evaluation,
good oral hygiene and normal-appearing gingiva must be attained.
Restorative materials
After oral prophylaxis and cavity preparation (class V test
Cavities) the material, mixed accordin to the manufacturer’s recommendations, is placed
in a subgingival cavity, and its effects are onserved after short (7-da7) and long (30-day)
terms.Responses are categorized as slight, moderate, or severe. A slight response is
characterized by a few rond cells in the epithelium and abjacent connective tissues. A
moderate response is indicated by numerous round cells in the connective tissue and a
few ncutorphils in the epithelium A severe reaction is evidenced by an increase in the
responses in each category and thinned or absent epithelium.

5. Cements
Zonc polycarboxylate cement produces the mildest gingival reaction of all
cements tested, with mainly slight but a few moderate responses. Gew inflammatory
cells are present in epithelium and connective tissue.
Zinc oxide-eugenol cements cause slight to moderate response with a few
severe responses and thinned epithelium. This wide range or responmse is of interest and
may be a result of variations in damage to the tissue.
Ethoxybenzoic acid cements show slight to moderate responses, with more
moderae than slight. To modeerate response with a few severe responses and thinned
eithelium. This wide range of response is of interest and may be a result of variations in
damage to the tissue.
Ethoxybenzoic acid cements show slight to moderate responses, with more
moderate than slight.
Silicates
In general, silicates elicit moderate gingival responses, with a few slight
and severe responses. Epithelial cell proliferation occurred in some arease epithelial cells
polit away, and there were a few instances of dense cellular infiltration. Most of these
changes pesisted at 30 days. Again, the wide range of response may be a result of thin or
think mixes; the think mixes allow more free acid to afect the adjcent tissue. Surface
irregularity is an important factor and should be eliminated.
Composites
Composite resins placed sunbgingivally in class V cavity preparations in
subjects withpreviously normal gingiva developed marginal gingivitis. It was found that
plaque forms more readiluy on the surface of composite resins than on tooth enamel,
even though the resins are finished and polished according to the manufacturer’s
directions. It is he importance of develping materials for dental use that are well
tolerated by the oralk tissues cannot be overstated. Testing regimens have involved
manuy different methods including: tissue culture studies; subdermal implantation in
animals; and in-use testing methods in nboth methods there have been variations in
technique and widely different results have been ontained in differefnt centres which the
samd material has been evaluated.
Recently, nboth the british Standards institutre (BSI) have set our
protocols for the nbiological testing of dental materials. These include general systemic
toxicity tests as well as in-use dental evaluiation. The propocols are complex and
demand the use of different animal models. To date there is no record of any material
being sunjected to the complete protocol in one laboratory.
The major biologifcal concern with restorative materials has been their
efect on the dental pulp. Much of the early wsork concentrated on the chemical toxicity
of materials caused by, by for example, the acidity of cements or free monomer in resin

6. systems. Recent reports have demonstrated that bacterial contamination(see below) may
modify the response of the pulp to these aspects of materials. Indeed, it has been shown
that much of the damage kpreviously attributed to the chemical toxicity of materials such
as silicate and phosphate cement was caused by bacterial action.
Potential sources of bacterial contaminiation of the floors of cavities are:
(a) the original carious lesion;
(b) saliva and/or plaque which may become smeared over the cavity walls and
floors duridng cavity preparation;
(c) bacterial ingrowth which may occur down cavity walls following insertion of
the restoration. At present there is no restortive material which gives a perfect
marginal seal and it sis accepted that all restorative materials sufer from some
degree of marginal leakage. With careful technique, this is least with the
modern adhesive restorative materials and most marked where there is a
setting contraction. Removed by normal cavity cleasing, i,e by hand
instruments and water-spray. It may be divided into an outer layer which
follows the contour of the cavity wall, and an inner layer which forms plugs’
in the ends of the dentinal tunbules (Fig 17.3; see also Fig 18.2p, 363).
DENTINE CLEANSERS AND CONDITIONERS
(SEE ALSO Chptter 18)
After cavity preperation with rotary instruments the Dentine walls and
floor of the cavity will be covered with the Dentine ‘Smer Layer’ (see Chpter 16) this
consists of a layer. Irregurally shaped hrd tissue particles of dentine (& perhapes animal)
debris ranging in size from beolow 0.5 um to more than 15 um. Which are not removed
by normal cavity cleansing. i.i., by hand instrument and water spray. It may be devided
into an outer layer which follows the contour of the cavity wall. And an iner layer which
forms “Plugs” in the ends of the dentinal tubuls (fig. 17.3 & fig 18.2 p 363)
There is considerable debate as to how much of the smear layer should be
removed. Some authorities advocate its totald removal (With lower molecular weight
acids.)but this can be criticized because it ipens up and widens the ends of the dentinal
tubules, with three possile significant disadvantages.
(a) It renders the tubules much more susceptibnle to invasion b bacteria and their toxins:
this will invariably produce and adverse pulp response.
(b) It increases the permeability of the dentine to certain irritant dental materials.
(c) It allows an outflow of fluid from the dentinal tunbules which will wet the dentine
surface, this in turn making it more difficult to achieve an adequate seald with any
lining or base.tuibwe’ to prepare the dntine in abrasion avities to receive galss-
ionomer cements. In these cavities, the dentine, as a result of exposure to saliva, will
be coated with a thin film of mucins which, if left, act as a separating agent threrby
preventing the bonding of the alassinomer cement to the dntine. In this sitution,
shorr apliction times (of a few seconds) would remove the mucns Pulp irritation is

7. not usually a problem because the coronal pulp is normally completely onbliterated
by repartive dentine in theeth with abrasion cavities. However, such adids hould not
be applied to freshly cut dentine.
(d) More recently, polycrylic acid has been sunbstituted for the citric acid is some
demtome pmdotopmers supplied with glss-ionomer cements. This has a much hiher
molecular weight than citric acid, and a 25-second application of a 10% solution of
polyacrylic acid is recommended for conditioning freshly cut dentine. The effects of
polyacrylic acid on the smear layer have yet to be investiated fully.
LINING MATERIALS
The trditional view of the function of a lining is that it is necessary
promarily to protect the pulp from thermal and/ or chemical injury and hence also from
postoperative pain. The mechanisms of pin sensation in dentine do, however, remain
incomopletely understood. Some authorities associate it with the movement.
It has been demonstrated in the laboratory that to achieve ideal thermal
instulation wtih dental lining materials and cements, a thickness of 1.0-1.5 mm is
necessary (Fig.17.6) There authors and others have advocated lining thicknesses of 0.5-
0.75mm (Fig.17.6) However, these orders of thickness appear to be only rerely achieved
with some materials (e.g clacim hydroxidesee below), yet patients arely complain of
thermal sensitivity when well adapted thin linings are placed.
The current view is that much of the pupal damage kproveiously attributed
to the chemical composition of lining and filling materials (e.g. silicate cement and resin)
was in fact caus by tjhe ingrowth of bacteria at the margind if these restorations. It
appears, therefore that the most important function of a lining is to seal the dentinal
tubules, thus preventing pulp damage caused by any bacteril ingroth sich occus at the
restoration margins as a result of mucroleakage.
The following are the important features of lining material.
Ideally, it should.
(a) seal dentine;
(b) be bactericida;
(c) non-toxic and bland to the pulp;
(d) have adequate physical proprties-mecgabucal;thermal etc;
(e) induce remineralizatio or huyperminewralization of dentine on cavity floors
(this reduces the permebility of the dntine to any bacteria dwhich do gain access);
(f) be adhesive to dentine and major restdorative materials.
Calcium hydroxide
Whilist tis precese mode of action is unclera, clacium hydroxide is the
material of choice for both pulop capping and lining the deep cavity. The proprietary
hard-setting clacium hydroxice materials seve well as universal lining materials. As a
pulp-capping material, calcium hdroxide fis unique in its ability to rormite dentine

8. bridge formation. In the deep cavity it induces some remineralization of any softened
dentine remaining on the cavity floor. Studies with labelled calcium hydroxide have
demonstrated that calcium ions do not move from the dmaterial itself, but they dcome
from the bloodstream.
The proprietary calcium hdroxide lining materials appear to seal the
dentine adequatcly, and they are bacteicidal. Certinly they are active against many
microorganisms, but there are resistant strains. Many authorities attach improtance to
the alkaline PH. Which is considered to counteract the acidity in the deeper parts of
carious lesions in dentine. Propriearty calcim hydroxide materials are presented in
combination with a number of different setting rsins, which appears to be bound into the
resin and not released.
The film thickness chieved with thes proprietary materials is usually less
than 0.5 mm (Fig.17.7) and though they are the weakest of all the standard lining
materials, they are adequately strong to withstand the packing of amalgam. However,
they re not suitabfle for use in thick sections or to block out undercuts under gold or
procelain in restorations. Care should be taken to use an acid-resistant calcium
hydroxide material if acid etching dof the enamel parts of the cavity walls is to take
place; some propritary clacium hdroxide liners are solunble in phosphoric acid
(fid.17.8.)
Zinc oxide/eugenol-based cement
The resin-bonded frofms of these are physically stronger cements and they
also induc remineralization of softened dentine. They from the best seal of any of the
dental cements and they are truly bnactericidal to may oral bacyteria. However, the
phenolic group in the eugenol are pulpal irritants and they produce persistent chronci
inflammation (Fig 17.9) if placed on a pulp exposre. There is some evidence to suggest
that a similar effect occurs nin very deep cavities even where there is no exposure, and a
sublining of calcium hydroxide is there for desirable in these situations.
In cavities with a reasonable residual dentine thickness, zinc koxide/
eugenol is a excellent lining material. It is also a satisfactory material for building up a
thick base over calcium hydroxide when required. It should not be used under
composite resin restorations, as the eugenol may inhibit polmerzation. Any excess
engenol will also stain the dentine, which is a cosmetic pronblem in anterior teeth.
The ethoxydenzoic acid (EBA) cements are modified zince oxide/eugenol
cements with superior mechanical properties, achieved buy sunstituting two-thirds of the
zinc oxide with fused quartz.
zinc phosphate cements.
These were the first widely used lining and luting materials in dentistry
and in this latter role they are still pupuilar. However, they are irritant to the pulp-
dentine complex, early reports attrinbutig this to their very acidec settfing pH of 2. This
is only transient, and they rapidly become neutral after setting. Their toxicity is now

9. consideted to be caused largely nby bacterial ingrowth at the margins, following a
settifng contraction.
Zinc polycarboxylate cements
These cements were introduced in 1968 as the first materials which
adhered to both enamel and dentine. They are presented as both linin and luting
cementsf. However, presented as both lining and luting cements. However, they are
didfficult to manipulate well and in use they adsorb water, which leads to a deterioration
of their mechanical properties, including their bond strentth.
Studies of their effect on the pulp have produced variabfle results, with
sosme relports of sever inflammation and others which fdemonstrate an apparentluy
mild response. In any but the shallowest cavity, a calcium hydroxide sunblining should
be placed. The polycarboxylate cements play a useful role as materials to replace lost
dentine or block ot undercuts in preparations which are to receive cast or cermic
restorations.
Glass-ionomer cements (Polyalkenoate cements)
Glass-inomer cements are now availabfle for use as lining and luting cements, as well as
being restortive materials their proncipal advatage lies in their forming a molecular bond
with the dentine (and the enamel), though the seal produced is not necessaril perfect;
nbcteria have been demonstrated in the interface between glassionomer restorations and
the tooth (Fig 17.10) This probably reflects the difficulty in the clinical situation of
bringing the material into even contact with the cavity surface. This ingrowth of
bacteria appeas to be responsinble for at least part sdof the pulpal damage that has been
reported after placefment of glss-ionomer cements in deep cavities.
Recent reports have sugested that glass-ionomers applied to dentine may also produce
chemical damage in the pilp. This is manifested b damage to pulp cells and an
inhinbition of calcific repair, rather than by inflammation. It is therefore necessary to
place a sunlining (calcium hydroxide) in the deepest parts of all cavities that are to
receive glass-ionomer cement where dentine has been freshly cut. In abrasion cavidties
the cornal pulp is normally completely obliterated by calcific material and a lining is not
required. There have been reports of pulpal hypersensitivity following the use of glass-
ionomer lutin cement for crowns.
Now of the glass-ionomer materials has physical properties suitable for the
long-term restoration of occlusal surfaces, though they have a number of useful
indidcation (see p.367.) As a straight glass-ionomer centnt or in the form of a cement
(see p. 368), the material appears to hve an improtant role in building up dentine prior to
the application of composite resion (see Gig 14.57). Used in this manner it protects the
pulp and dentine tubules from the effects of the acid used to etch the enmel prior to
composite bonding. This acid treatment also serves to roughen the surface fof the glass-
ionomer, so enabling an effective bond with the composite. Although there have been
criticisms regardifng disrupation of the surface integrity of glass-ionomer cments

10. following acid application and treatment with acid cannot be recommended.
Fortunateluy restorative suystems have become availabfle in which acid treatment dof
the glass-ionomer ‘lining’ is no longer necessary.
Varnishes
Varnishes are apploed sparingly to cavity perparations (inclding the cavity
walls and margins) for amalgam, as they reduce the intial microleakage which occurs
with amalgam restorations. Some clinicians use then routineluy, especially in the USA
They have a special place in sealing the cavity walls and dentine din minimal cavities
where there is insufficiefnt depth to fwarrant a cemfent lining .
The majority of varnishes consist of natural resine, e.g copla or shellac
dissoved in n organic solvent sucjh as ether dor ethl acetate. Whenapplied, the solvent
evaporates leaving a resion coating on the dentine and enamel. It is necessary to apply
at least two coats of the varnish to achivee fa viod-free films and hence a seal
(Fig.17.11).
Most varnishes are clear liquids. It is important to replace the cap on the
bottle to prevent evaporation of the solvent leadifng to thickening of the varnisjh which
makes it impossinle to apply in thin layers. It is necessary to add thinner to the bottle
from time to time .
FURTHER READING
Amussen E., jorgenson K.D. (1972) A microscopic investigation of the adaption of some
plastic filling materials to dental cavity walls. Acta odont. Scand 30-3-21.
Brannxstron M (1981)
Dentine and pulp in restorative dentistry Nacka: Dental Therepeutics AB (Also London
Wolfe Medical Publications, 1982)
Causton B.E. (1984) Improved bonding of composite restorative to dentine brit dent J;
156: 93-95.
Morrandt G. (1977) Dental instrumentaion and pulpal injury.1 Biological and physical
factors. L Brit. Endodont Soc., 10:55-63.
Pateson R.C. Watts A. (1981) Dental instrumentation and pulpal injury.2
Clinical considentations J.brit Endodont. 10:55-63.
Paterson R.C. Watts A kinner’s science of dental materials, 7th
edn. Philadephia:W.B
Saunders.

11. Wats A. (1979) Bacterial contamination and the toxicity of sillicate andc zinc phosphate
cement. Brit.dent J., 146:7-13.use a clear plastic matrix band to enhance curidng in the
less accessinle regions of the cavity while the band is till in place. Unfortunately,
however, the handing properties of plastic matrix bands somethimes make them
awkward to use. Clear plastic wedges can be used to transmit the light to the cervi cal
region of the restoration.
The maximum reliabfle depth of cure that cn nbe achieved with light is
about 2mm This means that an incremental techniquer is usually necessary to ensure
complete curing (Fig.18.5) Most opertors limit themselves to a thickness of 1.5 mm for
each application. The composite should be applied first to exposed parts of the dentine,
because the bond to dentine is fweaker thand to enanel; if resin is applied across enamel
and dentine, the disparity in strenght of the bond, togerther with the more repid cure
achieved in contact with the enamel, may cause the resin to pull away from the dentine.
In general, the material should fbe applied to the more remote parts of the cavity first.
As the resin shrinks towards the curidng light, placement dof the light
against the baccal and lingual tooth surfaces is advised prior to curing from the occlusal
direction. This will assist the increments of resin shrinking towards the cavity floor.
Finishuing of composite restorations
Any gross excesses should be trimmed with tungsten carbide or find diamond bursm
usifng water spray as a coolant. High or low speed can nbe used, the latter allowing
more control where only small amounts of excent material dare present. Fine abrasive
strips and/or discs have been developed for final dshaping and polishing and these are
veruy effective. Asmussen’s wsorks suggests that only gross excesses should fbe
removed immediately. Since all composites absorb some water over the first 24 hours
after their insertion and undergo hygroscopic expansion, his argument is that if the final
dfinishing is delayed until this reduced to a minimum. Nevertheless, many practitioners
go against this advice, for they feel that the practicalities of the situatioin demand that
finishing and polishing should fbe undertaken at the same visit at which the restoration
is placed. Certainly, it can be argued that once the rubber dam has been removed,
attention to detail (e.g. that of achieving the final approximal contour) becomes more
difficult; and the cervical margin is then likely to relate to moist gingival tissues and
therefore be less accessile.f The hybrids can be polished, but a high gloss will not be
achieved.
The danger of leakage at the gingival margins of class ii restorations
makes regular checks essential
Disadvadntages and contraindications of composites
The main drawacks of the posterior composites are:
(a) polymerization shrinkage;
(b) possinly unsatisfactory were characteristics;
(c) difficulty in achieving anatomical form.
(d) Polymerization shrinkage

12. This is inevitable by the very nature sof the material and it will tend fto be greater in
bigger cavities where larger volumes of resin are used. When the acid etch technique is
used, polymerization shrinkage can lead to inward bendifng of the cusps. The long-term
implications of this are unknown, but it certainly seems reasonabfle to tae all steps to
minimize it (sewe ‘Dynamics of the restored tooth P.3569).
Leakage is a likely consequence of polymerizqtion shrinkage and this is
especially liabfle to occur at the cervical dmargins of restorations where there is tlittle or
no enamel for bonding purposes. Such leakage may be the reason for the sensitivity to
hot and cold which sometimes follows the placing of these restorations. It certainly
contraindicates their use in patinents whose caries is not properly controlled, or where
there is poor oral hygiene.
Wear
The newer posterior composites appear to wear favourably. Though it fis pruudent to
avoid their use in patients with marked attriotion. The consequences of wer of the
opposing and adjacent teeth hve still to be evaluated in the long term.
GLASS-IONOMER CEMENTS
Glass-ionomer centnts consist of aluminosilicate glass mixed with an aqqueous solution
of polyacrllic acid and related polyacids. This forms a set mass of unconsumed glass
particles embedded in a matirxx of poluacrylate gel. Some of the moe recently
inrroduced glass-ionomer cements contain other acids such as polymaleic acid and
itaconic acid. Glass-ionomer cenents dhave the ability to bond chemically to both enamel
and dentine. Theyu were first introduced in the 1970.s when dthey found thedir greatest
clinical use in the restoration, without mechanical preparation, of cervical
erosion/abrasion lesions.
The adhesion of glass-ionomer cements has been attributed to penetration
of carboxylate grops into the huydroxyapatite of the senamel and dentine, with
displacement o phosphate ions. Electrical neutrality is maintained by the displacement
dof calcium ions along with the phosphate ions.
As restorative materials, the glass-ionomer cements have the distinctly
bebeficial characteristic of leaching flouried; this should help to prevent secondary caries.
The al;so pick up fresh fluoride ions from the moth, e.g from fluoride toothpaste; these
ions then become available to the adjacent enamel. Co,pared with the composites, certain
of the mechanical; properties of the glassionomer cemefnts are poorer.
Clinical lhandling properties
Glass-ionomer cements require particular care during handling. They tend to stick to
metal instruments and to pull away from cavity walls during manipulation. Thus, while
being contoured they tend to ‘drag’ away from the cavity margins. These materials are
moisture sensitive and the cavity must be kept completely dry during placement. After
placement they should be kept dry for several hours by coating with varnish or
restorative resin (polymerized), to prevent disruption of the gel. The earlier materials

13. could not be trimmed during the initial 24 hours, though some of the newer materials
have been modified and can be trimmed during the visit at which they are placed.
However, a better surface finish is obtrained if final finishing is delayed for 24 hours.
Indications and uses
1. Erosion/abration lesions in permanent teeth. Provision of mechanical retention
in these cavities is difficult and glass-ionomer cements cements can be used
without this.
2. Class I and II and V cavities in deciduous teeth. Recent clinical trials have
demonstrated that glass-ionomer cements can be used satisfactorily to restore
these lesions in deciduous teeth.
3. Class III and V cavities, especially in caries-prone individuals.
4. Repair cavities. The fluoride leaching properties of the glass-ionomer
cements make them a fist-choice material for repairing restorations in regions
where future secondary caries is a realistic possibiliy, such as at the cervical
margins of crowns
5. Deep cervical and root cavities. In cavities which extend towards the edge of
the anatomical crown, the cervical margin often consists of thin and friable
enamel with a prism direction that is complex and not conducive to good
etching. If composite resin is placed against such a margin there wilkl be a
very real risk of an unsatisfactory seal. Similarly a seal could not e expected
when the cavity margin is entirel in cementum or dentine. Subject to
satisfacytory isolation(usually with rubber dam,) glassionomercompositre
sandwich restoration (Fig. 18.6). With this laytter m,ethod thefirst=placed
glass-ionomer material is addapterd against the vulnerable cervical margin to
achieve the best p[osible seal. In the coronal part of the cavity tyhe glass-
inomer cemnt forms a lining onluy. This can then be coated with a bonding
agent consistintg of a halophoshorus ester of Bis-gma.This will bond
chemically both ytop the glas-inomer and to the compsite resin which
completes the restoration. This twopart restoration provides the hbbest
possible marinasl seal aesthertis and function that can be achived with a
plastic restoration in these difficult cavities.
6. Fissure sealing in deciduous and permanent teeth. Because of the turgid nature
of the material this use is onl;u recommended where the vfissure is well
opened up either naturallu or by a bur(as when investigation the extent of the
caries present in a sealantrestoration technique; see chapter 13)
7. As luting cements. Thisa had been made possible y a reduction in the particle
size. The materialxs have the advantage that they adher to enamel, dentine and
metalic ions.They will therefore adhere to metal cast9ings.
CERMET CEMENTS
The term cermet derives form ceramic plus metal. These materials are made by
mixing metalllic fillers of silver or gold with moltern glass and sintering them.
The resultant poiwder is mixed with a sloution of polumaleic acid. Suyccessful

14. clinicasl trial result jhave been had prevented its commercial
introduction.However expense had prevented its copmmercial introdution. The
silve-based material had been mark eted and the following remarks refer to this.
Clinical handling properties
The materiual is presented in capsules for mechanical mixing and a special
applicator allows the capsule contents toi be syringed directly into the cavity.It is
difficult to work with:the cemtn sticks to metal; inmstruments;and it had a
relatively short settint toime of 1.5minutes. It is difficult to achieve any packin
pressure and carvinmg and contouroing require special care as the material tends
to draw away form, the cavituy margins. Once set the cement must not be left
esposed to air, or large cracks will form as it dries oit: it should bre varinisjhed to
prevent moisture contmination. It can only be poli9shed to a dull lustre finish.
Examination of finished restorations reeveals a pitted and cracked surface and
there are frequent voids at the margins presumaly caused by a setting contraction.
Indications and uses
Wheres further development work is necessary before the use of cemt cement can
be supporyted without reservartion the following uses have been suggested.
1. Restorations in deciduous teeth.
2. Class I restorations in permanent molars.
3. Building up lost dentine under composite restorations including in insrtances
where an internal or tunnerl preparation had been made to restore a posterior
tooth with apporoximal caries.
4. As a core material for crowns in broken down permanent teeth.
FUTURE DEVELOPMENTS
In view of the considerable amount of pulp damager that can be produced by
bacterial ingrowth at restoration marins the following areas should be seen as
improtant for development with respect to both composite resins and glass-
ionomer cements.
1. Techniques to improve the wetting of the cavity walls
Inflammation:

15. The defense elements of the body that are mobilized to the site of injury are
present in the blood. To achieve this mobilization a series of changes occurs in the
microcirculation of the injured area. These changes are dominated by arteriolar
vasodilatation and increased permeability through contraction of the endothelial cells of
the post capillary venules. These vascular and hemodynamic changes are mediated by a
variety of chamecal mediatrors realsed in the injured area: histamine (from the granuales
of mast cells and baspohil leukocytes); serotonin (in humans, from the dense granuales of
blood platelets); kinins (pep0tides formed through cleavage of kinigonens of by
kininogensses): anaphylatoxins (peptides formed through cleavage of the third and fifth
complemlent components releasing the anaphylatoxins C3a and C5a, which in induce
degranulation of mast cells and basophils); and prostaglandins and leukotrienes
(arachidonic acid derivatives)
Exudation develops as a result of increased vascular permeability Leukocytes that
have marginated adjacent to the vascular endothelium and adhered to the endothelial cells
and pseudopods through the gaps between the endothelial cells and escape from the
vascular lumen. Once outside the endothelial cells,d they migrate toward the site of
injury under the influence of chemotactice factors (both bacterial and endogenous in
origin; the latter include C5a, the activaterial and endogenous in origin; the latter include
C5a the activated triple complex C567, and certain lymphokines secreated by T and B
lymphocytes)

16. Neutrophils are the first leukocytes to arrive at the site of injury. They are the
predominant cells of acute inflammation. However, virtually nany type of injury results
in initial accumulation of neutrophils. 30
These involves a sespiratory burst with increase
in oxygen consumption and generation of reactive oxygen radicals that the are
bactericidal but can also induce tissue injury.
Whereas the neutrophils are the predominant cells of acute inflammation,
macrophages, lymphocytes, and plasma cells are the predominant cells of chronic
inflammation. What leads to chronicity is persistence of the irritant, and this is often
accompanined by the development of a cell- mediated immune reaction.
Macrophages are derived from the mamocytes of blood. Monocytes are not end
cells. Their half-life in the circulatin is about I day. They leave the circulatioun to form
different components of the mono nuclear phyagocyte system.
Macrophagea are efficient phagocytes. Not only do they phagocytose bacterial,
buyt also they ingest tissue debrise to clean up the area in preparation for repair. They
also play an essential role in the development of immune reactions through antigen
processing aznd antigen presentation to lymphocytes. Among their secretory products are
lysoszyme, certain components of the complement system, interferon, collagenase,
fibronectin, fibroblast- activating factor, and angiogenesis factor.
Lymphocytes are the essential cells of the immune system. Two major types are
recognized , T and B cells. Lymphocytes are the essential cells of cell- mendiated
immune reactions. B lymphocytes are the essential cells of humoral immunity. Intricate
interactions take place between macrophagea and T and B lymphocytes, and T helper

17. cells are essential for the induction of a humoral immune response to certain agigens. T
suppressor cells regulate both humoral and cellmediated immune reactions.
Plasma cells, which are derived from B lymphocytes, synthesize and secrete
immugoglobulins. Eosinophils may be encountered in inflamed tissues, including
inflamed pulp. They phagocytose antigen antibody complexes and contain enzymes that
inactivate some of the chemical mediators released in areas of injury. Undetected
microscopic exposure of the pulp is of utomost importance. Each of these causes of
iatrogenic pulp injury will be briefly considered.
Preparation of the Cavity:
Dentin is a vital tissue. That fact the dentin is a hard tissue and that it does not
bleed on cutting may give rise to a false sense of security. Avoide heat generation and
dentin desiccation during cavity preparation. Heat dissiopation and prevention of
desiccation can both be accomplished through the use of a water coolant. With the
present day high –speed instrumention, the use of a water coolant with collant is
mandatory. A simple rule to follow to eliminate two sources of iatrogenic pulp injury
(heat and desiccation) is “never cut dry.
Insertion of the Restorative Material:
Physical forces generated during condensation of amalgam and direct gold
restorations can lead to pulp injury 26, 27
This is particularly. The major requirements of a
cement base with such me tallic restorations are as follows:

18. A hard – shtting calcium hydroxide preparation or a reinforced zinc oxide and eugenol
cement, a calcium hy-droxide liner or a stronger base. Howeer, with this cement , a
calcium hydroxide liner or a caviry varnsh should be applied prior to the insertion of the
cement to protect the pulp from chemical irritation.
Irritational Qualities of Restorative Materials.
A major cause of iatrogenic pulp injury is chemical irritation by the restorative
material. According to their irritational qualities, restorative materials can be classified
into three major groups:
Group I -- Low irritaitonal potential : gold, amalgam, zincoxide and eugenol
cement, polycarboxylate cements, and glass ionomer cements.
Group II -- Moderate irritational potential : zinc phosphate cements, and glass
ionomer cement.
Group III – High irritaitonal potential : silicate cement and resins.
Group I. Biologically, gold and amalgam are relatively insert. Any primary from
physical forces incident to condensation and possibly from thermal shock and
electrogalvanism caused by the high conductive qualities of these materials. Measures to
protect the pulp from such injury have already been outlined.
Zine oxide and eugenol (ZOE) has a low irritational potential. Its pH, when
freshly mixed, is 7. 19
The low irritational potential of ZOE makes it ideal as a negative
control in stuies that evaluate pulp reaction to restorative materals. Zinc oxide and
eugenol also has an obtundent effect on the pulp. Eugenol inhibits the synthsis of
prostaglandin; it will of ionglammation and also contribnute to pain sensation in areas of

19. injury. Furthermore, the hygroscopic qualities of ZOE may result in withdrawal of fuild
from the pulp through the dentinal tubules thus reliving pressure on sensory nerve
endings of the pulp. Zinc oxide and placed over an exposed pulp, ZOE dies not stimulate
reparative dentinogenesis ; on the contrary, it elicits a low-grade inflame-matory
response.
Polycarboxylate cements have a low irritational potential . 9
They are remarkabluy
innicucous, despite a pH of 1.7 of the rapid rise of the pH during setting of the cement.
Furthermore, the large molecular proteins would limit its diffusion through the tissues.
Group II. Zinc phosphate cement has an irritaional potential that ios intermediate
between ZOE and silicate cement. Three minutes after thereafter, approaching neutrality
in 24 hours. 19
Thus, damage to the pulp would occur during the first few hours after
insertion of the cement. This damage could be prevented by application of a calcium
hydroxide liner or a cavityvarnish prior to placement of the cement.
Group III. Silicate cements have ahigh irritational potential. These cements have
a pH below 3 at the time of insertion ; the pH remains below neutrality even after one
month. 19
The high irritational potential of silicate cement makes it ideal as a materials.
A calcium hydroxide liner or a cavity varnish prior to placement of the cement.
Resins, whether unfilled or coposits, and the latter, whether conventional or
microfilled,autopolymerizing or photoactivated with ulraviolet or visible light are
irritating to the pulp. Their irritational potential is comparable to that of silicate cement.
Which component of the composite resin elicits pulp injury? In a study of pulp reactions
to eight components of composite resins, none of the components tested elicited

20. significant pulp injury 24
It appears likely that reactive radicals generated during the
polymerization of the resin are responsible for pulp injury by these materials. Pulp injury
by the resin resto ration can be totally abrogated through the application of a hardsetting
calcium hydroxide base beneath the resin.
FACTORS THAT INFLUENCE PULP REACTIONS TO RESTORATIVE MATERIALS
The most important single factor in determining the intensity of pulp reaction to
restorative materials is the thickness of remaining dentin. With most materials, 2 mm of
remaining dentin affords adequate pulp protection 22
The presence of reparative dentin is
influential; materials –laced ever freshly cut dentin are more damaging. The undetected
microscopic exposure of the pulp is of utomost importance. Numerous studies have
shown that pulp exposure can occur without climnically detectable bleeding. Only
through examination of serial histologic sections of the cavity and the underlying pulp.
Because it is impossible to determine cavity floor thickness clipically and because
microscopic exposure of the pulp may occur without being clinically detectable, these
two simple rules should be followed to protect the pulp from iatrogenic injury due to the
inherent irritation of restorative materials and the clinically undetected undetected
microscopic exposure;
1. Use a protective base or liner with materials in groups II and III regardless of
cavity depth.

21. 2. Use a protective base or liner in all deep cavities where the possibility of
microscopic exposure exists, regardless of the material to be used for
restoration.
Bacteria
Another potential source of pulp injury is bacteria, either residual microorganisms
left on the cavity floor or bacteris that gain access to the cavity after restoration3.
While bacteria may contribute to pulp injury when cavities are deep, they cannot be
considered solely responsible for pulp irritation to exclusion of the inherent irritational
potential of the restorative materials.
In the past, highly irritating chemicals were used for sterilization of the cavity. Because
vital Wheledentin has been shown to resist bacterial invasion and deep cavities should
have a protective base of calcium hydroxide preparation or ZOE, and both have been
shown to have antibacterial properties, the need for cavity sterilization is highly
questionable.7,16
A safe and effective means for cavity cleansing is simply rinsing the
cavity with warm water.22
ACID ETCHING
Resin restorations leak badly. The acid-etch technique was developed to improve
the marginal seal between the cavity and the restoration. Acid etching of enamel is safe,
provided a protective base of a calcium hydroxide preparation is applied over exposed

22. dentin prior to etching. Acid etching of dentin markedly increases its permeability. 18
Not
only does it remove the amorphous smear layer over cut dentin, which plugs the orifices
of the dentinal tubules, but it also demineralizes the peritunbular dentin resulting in
increased tubular diameter. Such patent tubules provide easy access of irritants to the
pule.24
PROTECTIVE BAES
The ideal protective base should be well tolerated by the dental pulp. It should
stimulate reparative dentinogenesis in case an undetected microscopic exposure of the
pulp exists. It should provide adequate protection of the pulp from irritant components
of the restorative material. It should have an obtundent effect on the pulp. It should have
an antibacterial effect to eliminate bacteria in residual carious dentin when used with
indirect pulp from thermal shock and electric conductivity to protect the pulp from
thermal shock and electrogalvanism when used with metallic restorations. It should
exhibit low acid solubility so that it will not disintegrate when used with the acid etching
technique in case the acid accidentally comes in contact with the material. I t should not
be affected by the restorative material nor should it in any way affect the restorative
material.
A protective base which fulfills all of these criteria remains to be developed.
However, ZOE and hard-setting calcium hydroxide bases fulfill many of these criteria.
With resin restorations, used with or without the acid- etching technique, calcium

23. hydroxide bases should be used. Zinc oxide and dugenol cement obviously is unsuitable,
as it interferes with resin polymerization.
With other restorative materials, either ZOE or calcium hydroxide bases are
satisfactory. However, if there is the slightest chance of a microscopic exposure of pulp,
a calcium hydroxide base should be used because ZOE does not enhance reparative
dentinogenesis. On the contrary, when placed in contact with an exposed pulp, ZOE
elicits a low- grade chronic inflammatory reaction.
PULP CAPPING
Numerous materials have been investigated as pulp-capping agents- However,
calcium hydroxide preparations have best withstood the test of time. There has been a
widespread concern among dentists that calcium hydroxide exerts a persistent stimulating
effect on the pulp that results in eventual obliteration of the pulp. Some also believe.
That calcium hydroxide may, on occasion, cause persistent inflammation of the pulp or
internal resorption.
Pulp reactions to three capping agents were investigated in mon keys at intervals
ranging from 15 to 880 days 13-15
with a calcium hydroxide preparation, there was
initially a high rate of reparative dentinogenesis. The rate, however diminished with
time, and there was no evidence of pulp obliteration in any of the specimens, even at 880
days after capping. A polycarboxylate cement was specimens, even at 880 days after
coapping a polycarboxylate many of the pupls capped with it should pulp necrosis or
severe inflammation. Interestingly, the pulp that survived showed persistent

24. inflammation with areas of obliteration of the radicular pulp. It was apparent that the
stimulus for eventual obliteration of the pulp is persistence of inflammation rather than a
direct effect of any medicament applied over the pulp.
BIOLOGIC EVALUATION OF DENTAL MATERIALS.
Historically, biologic evaluation of dental materials lagged behind evaluation of
their physical properties. It should be obvious that the biologic properties of dental
materials are just as important as their physical, chemical, and mechanical properties. In
1972, the Council of Dental Materials and Devices of the American Dental Association
published a series of guidelines for biologic evaluation of dental materials. 4
In 1979 the
American National Standard Institute/American Dental Association Document No. 41
was approved by the ADA counable guidelines for biologic testing of dental materials.
Tests for biologic testing of dental materials. Can be classified into screening
tests and usage test.
In the usage tests, the dmaterials are evaluated in suitable laboratory animals,
show that the material is safe, the material is then ready for evaluation in humans.

25. It is through such extensive biologic testing along with tests that evaluate the
physical chemical, and mechanical properties of dental materials, that the dentist will be
assured that the material he uses are both safe and effective.
REFERENCES
1) Avery, J.K : Dentin.In Bhaskar, S.N. (ed) Orban’s Oral Histology
Embryology, Edition 9. St. Louis, C.V. Mosby Co., 1980.
2) Brannstrom M., and Lind, P.O. Pulpal response to early dental caries JU.
Dent. Res 44:1045, 1965.
3) Brannstrom, M and Nyborg, H: Cavity treatment with a microbicidal
fluoride solution: Growth of bacteria and effect on the pulp. J prostht.
Dent., 30:303 1973.
4) Council on Dental Materials and Devices: Recommended standard
practices for biological evaluation of dental materials: J Am Dent. Assoc.,
84:382, 1972.

26. 5) Council on Dental Materials and devices: Amercian National Standards
Institute/ Amercian Dental Association document No. 41 Recommended
standard practices for biological evaluatin of dental materials J Am Dent
Assoc. 99.897,1979.
6) Dickey, D.M., Kafrawy, A.H. and Mitchel, D.F. Clinical and microscopic
pulp response to a composite restoration material J Am Dent Assoc.,
88:108, 1974.
7) Fairbourn, D.R. Charbenau, G.T., and Loesche, W.J Effect of improved
dycal and IRM on bacteria in deep carious lesions J Am dent Assoc
100:547,1974.
8) Fischer, F.M. Karraway, A.H. Mitchel, D.F. Studies of reparative dentin
in monkey teeth using vital dyes J. Dyes J Dent Res 49:1537,1970.
9) Kafrawy, a.H. and Mitchel, D.F. Pulp reactions to open cavities later
restored with silicate cement J Dent. Res., 53:15, 1970.
10) Kafrawy, A.H. and Mitchel, D.F., pulp reactions to open cavities later
restored with silicate cement. J Dent Res ., 42:874, 1963.
11) Kuttler, Y: Classification of dentine into primary, secondary and tertiary,
Oral surg 12:996, 1959.
12) Langeland, K., Dowden, W.E Tronstad L., et al: Human pulp changes of
iatrogenic origin oral surg., 32:943,1971.

27. 13) MeWalter, G.M. Kafrawy, A.H. and Mitchel, D.F. Rate of reparative
dentiogenesis under a pulp capping agent in moneys.J. Dent Res.,
56:93,1977.
14) MeWa;ter.G.M. Kafrawy, A.H., and Mitchell, D.F. pulp capping in
Monkeys J, Dent. 36:90, 1973.
15) MeWalter, G.M. Kafrawy, A.H. and Mitchell, D.F. Rate of reparative
dentiogenesis under a pulp capping agent in monkeys J Dent Res., 56:93,
1977.
16) Mjor, I,A. the penetration of bacteria into experimentally exposed human
coronal dentin Scand. J. Dent Res. 82:191, 1974.
17) Mohammed. Y.R. Van Huysen, G.V and Boyd, D.A. Filling base materials
and the unexposed and exposed tooth pulp. J Prosthet Dent. 11:503.1961.