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1. MICROLEAKAGE
Introduction :
The goal of operative dentistry, undoubtedly is to restore the tooth to
its form and functions. One of the requisite of a restorative material is to
adapt itself to cavity walls. Inspite of tremendous improvements in means
and technologies, none of the material could actually join chemically with
the tooth surface. The gap left between cavity walls and the restorative
materials plays important role in the prognosis of the restorative treatments.
Previously pulpal reactions to dental procedures were thought to be induced
by mechanical irritations but bacterial leakage is a greater threat to pulp than
the toxicity of restorative materials. Different authors have termed it as
marginal predation liquid diffusion, fluid exchange, capillary penetration
and etc.
Definition :
Microleakage is defined as “The clinically undetectable passage of
bacteria and bacterial products, fluids, molecular or ions from the oral
environment along the various gaps present in the cavity restoration
interface”.
Possible Routes of Microleakage :
1) Within/via the smear layer.
2) Between the smear layer and cavity varnish/cement.
3) Between the cavity varnish/cement and the restoration.
It has been found that minimum of 1.0 µm space is left at tooth
restoration interface even after employing the adhesive liners and materials.

2. Clinical implications :
1) Post-operative sensitivity :
• Due to direct communication between oral fluids and pul and it.
• Leads to change into local ionic concentrations.
• These acids/basic materials and other substances produce movement
of fluids in tubules.
• Lead to pain in pulp.
• Mostly noticed in
o Proximal cavities
o Cervical cavities
o In resin restorations due to polymergation
shrinkage
2) Secondary Caries/Recurrent Caries :
• Bacteria with average diameter less than 1.0 µm can easily
penetrate the gaps.
• If the gap is 50 µm it this space can produce nutrients for the
bacteria hence inviting recurrent caries.
3) Pulpal pathology :
• Marginal gaps allow bacteria.
• And produce a number of inflammatory components
• Which penetrate dentinal tubules
• And affect pulp leading to pulpal diseases
At gingival wall

3. 4) Marginal discolouration :
• Evident in esthetic restorations
• It leads to accumulation of subsurface interfacial staining
5) Dissolution of the certain materials like cements.
Factors that Influence Microleakage :
a) Properties of restor materials that contribute
microleakage :
Major :
1) Coefficient of thermal expansion
2) Plymerization shrinkage
3) Adhesion.
Minor :
• Creep
• Elasticity
• Resistance to fatigue failures
• Solubility
1) Coefficient of thermal expansion (CTE) :
It is the change in length per with length of a material per degree
change in temperature.
• With increase in temperature  expansion
• With decrease in temperature  contraction
• Ideally rest material should be closely to tooth
C.T.E/contracting
• If C.T.E of 2 very 
o 1 may expand/contract more than other during
change in temperature.

4. o Leads to leaky rest margins.
(Table 23.1 Sikri page 551)
2) Polymerization Shrinkage :
• Occurs with polymeric materials
• Monomer chains are polymerized to form polymer
chain
o There occurs a decrease in volume and increase in
density
o This shrinkage pulls material away from cavity
walls.
• If intermediate adhesive resin used
o Contraction stresses are high
o Occur a break in adhesive bond
o Leads to microleakage
(Table 23.2 Page 551)
3) Adhesion :
Adhesion is the attraction of molecular of two different substances to
each other when they are brought in close contact.
• Lack of adhesion – microleakage
• Adhesion influences by –
o Wetting capabilities
o Surface energies

5. o Presence of water
o Swear layer
o Composition of enamel and dentin
o Surface roughness etc.
b) Influence by operator :
• Improper isolatory
• Poor consternation
• Improper insertion
• Poor cavity designs
• Poor burnishing
• Exposing cement live to the oral cavity.
c) Role of smear layer in microleakage :
Subsequent to instrumentatory of the tooth, the natural deposits
composed of microcrystalline cutting debris embedded within the
denatured collagen is formed on the cut surfaces known as “smear layer”.
• It is 1-2 µm thick
• Consists of blood, saliva, bacteria, enamel and dentin particles.
• Initial cutting debris – may be pushed into tubules
o 1-5 µm-smear plays
• Weather of decrease M.L. – Not clear
o 1 opinion – leave smear layer intact to act as barrier but when
pH level drops – it dissolves
o 2- opinion – remove smear layer
 Because smear layer itself contain bacteria and also
smear layer can present bacterial entry but not bacterial
products and good adaptation of adhesive material.

6. Best way – remove natural smear layer but not smear plugs
Replace with sterile, inert and non toxic synthetic smear layer.

7. Factors controlling bacterial penetration :
a) Size and nature of the gap :
• Varies with different rest materials – 10-50
µms
• But 10 µm is enough for lactobacillus entry.
• Self sealing capability of rest materials
reduce bacterial penetration
• Self sealing may also occur because of
o Deposition of mineral salts of low solutility
o Accumulation of corrosion products
o Calcification of plaque like debris around margins etc.
d) Host defence factors :
• Sclerotic dentin/reparative dentine
• Hydrostatic pressure of pulp increase than
outside pressure of oral cavity
• Plasma proteins in dentinal fluid – act as
natimicrobial agents
• Large molecular weight proteins like
fibrinogen
Make dentin less permeable to bacteria
• Presence of smear plugs – increase M.L.
• Alteration of chemical structure of dentin by
o Leaching of tin/Mercury ions from amalgan
o Leaching of fluoride from GIC and
silicaticement
e) Restorations
Alters dentin
permeability

8. GIC, silicates, compromise – release fluoride into gaps
Have antimicrobial effect
Silver, tin, mercury – antimicrobial effects.

9. Restorative materials and microleakage :
I. Fresh mix condensed – does
not adapt closely
10-15 µm gap
but it is self sealing restorative mat with time
Due to corrosive products
• In low copper – corrosive products formation and accumalation takes
place on gaps.
o Corrosive products like oxides and chlorides often
• In high copper – greater resistance to corrosion
o So slower rate of formatting of corrosive products
o So microleakage for longer period
Due to dimensional changes :
• Quite minimal
• During setting – small contraction initially (when misery
in consumed)
• Followed by small expansion (as crystal matrix is formed)
• High Cu alloys – dimens change very little ±0.2% by volume.
• According to ADA No. 1 – dimechange of 20 µm/cm is allowable for
set amalgam.
• Coefficient of thermal expansion of Amalagm = 25x10-6
/0
C so not
much different between them – do due to C.T.E Moderate leakage.

10. Measures to reduce :
Amalgam microleakage :
1) Types of alloys :
• Different types have different leakage
• Spherical alloy – more leakage and postoperative sensitivity.
Because not closely adapted
And more shrinkage after it sets
• So lateral condensation done
• Better to select lathe cut/advised alloys
2) Condensation of amalgam :
• Condense immediately – as time lapse
Loss of plasticity/increase in internal voids
• Incremental insertion – so proper condensation
• Adequate condensation pressure – 10 pounds with 2 mm condenser
tip
• (c pressure varies with alloys)
• Condensation from center to periphery (stepping process)
Removes air spaces
Pushes material against cavity walls
Decreases microleakage
• Mechanical condensation better.
(Quint Int.23(7)-495-1992)

11. 3) Burnishing :
• Adapt material to margins – (so decrease microleakage)
• Spherical alloys – no reduction in micreleakage.
Because during condensation particles may be pushed
aside.
4) Alloys with lesser creep values :
• Less creep – less M.L.
• According to ADA no.1 creep less than 3% is considered acceptable
o Low copper alloys – 0.8 –8%
o High copper alloys – 0.1 – 1% (decrease M..L)
5) Sealing the cavity wall with varnish
• Presents microleakage (until concision products form)
• But do not exist as long as life of rest.
Limited to six months
6 months enough for corrosion products fill gaps.
• Use of GIC liners – decrease microleakage
6) Sealed amalgam restorations
A coating of unfilled resin is placed over rest margins and adjacent enamel
after etching enamel surface
Resin may wear away
But covers until corrosion products fills gap.

12. 7) Bonded amalgams
Have shown to over come microleakage
8) Use of gallium alloys
It has high wetting ability
II. Microleakage around GIC
:
• Adheres to tooth with chemical bond
But cartoxyl groups of cement and Ca+ of tooth
Hydrophilic so can bond even in wet surfaces
• C.T.E – closely match tooth
• Fluoride releasing property
• Has ability to renew broken ionic bonds
• Highly technique sensitive
• 1st
30 min – moisture – ions are leached out
• 1st
24 hours – more solubility
• 1st
24 hours excess dehydration/dessication
Chalky /crazed/cracked appearance
Which of extends to margins
Leads to microleakage
So coated with varnish/unfilled resins
Using of sharp hand instruments for finishing before material has
completely set.

13. Effects marginal integrity
Prevention :
1) Proper manipulation
• Liquid/powder ratio-if lower – increase solubility
• Placed only after proper cleaning of the surfaces
2) Conditioning of tooth surface before insertion
• Agents – tanic acid
o Poly acrylic acid
o Citric acid etc
• Prior conditionring – increase bonding – decrease microlieakage
• Rapid initial setting – decrease moisture containnation
• But increase microleakage
Due to poly shrinkage
• In light airing GIC
Less water, les carboxylic acid
Decreased wetting
• But water uptake – function f resin component
Reduces microleakage
• Use of compomer as lining /flourable lining reduces microleakage
3) Finishing
• After 24hours
• Use rotary instrument to finish than menual cutting inst.

14. • As they tear away material at margin – marginal ditching

15. 4) Protection from moisture
• During fonishing – apply Vaseline /petroleum jelly
• Final protection – 2 coats of varnish/unfilled resin
Varnish semipermiable
Unfilled resin-more resist water
But varnish preffered –as at adheres closely
III. Microleakage around
composite restorations :
• Unable to bond on their own to tooth (so acid etch, prime, adhesive
area)
• If insufficient enamel thickness – increase M.L.
• It bonds dentin but not completely decrease M.L.
o Due To clinical composition of dentin
o Dentinal fluids
o Smear layer etc
• Polymerization shrinkage
o Range 1.67 – 5.68% light activated (lesser shrinkage than
others)
o If DB agents used
It bonds composite to tooth structure
But shrinkage results in tensile/shear stresses at tooth rest interface

16. Within limits of can with stand its bond strength
In exceeded plastic/elastic deformation
Separation of interface
• Masticatory forces
Repeated plastic/elastic deformation of rest
Enhance M.L
• C.T.E.
22-55X10-6
/0
C  Higher than tooth
so debonding
so microleakage
• Water absorbtion
Absorb water
Cause rest of expand
Compensate poly. Shrinkage – but mechanical prop impaired
Technique sensitive : in class II :
• Placement in gingival areas difficult
• Entarapment of air
• Difficult during condensation (sticky)
• Inadequate bonding to ging – polymerization shrinkage.
Measures to Reduce Marginal Leakage :
1) Choice of material
Microfilled :
Better marginal adaptation (than macrofilled)

17. Greater flexibility during shrinkage decreases contracting forces

18. It has larger water absorption capability
So decrease M.L.
2) Cavity design :
Conservative :
So decrease polymerization shrinkage
Decrease wear
Modified cavity designs :
• Placement of bevels
• Reduced depths
• Rounded internal angles
Shape :
• According to shape size varies
• V-shaped has less M.L. than box shaped cavities
Fig. 23.7, Page 55.7
• Decrease ratio of  decrease microleakage
Bevels :
Bevels on carosurface margins  controvetsial
Some say – bevel – increase surface area
M.L.
Some say – occlusal bevel – not needed
Because of enamel rod directions and rest may be extended to load bearing
areas
Cervical bevel – removes remaining enamel
Increase M.L.
Decrease M.L.
Good marginal adaptation
Volume
Bond area

19. Facial and lingual bevels in proximal box
Increases M.L. (75%)
(1998 (48))
3) Acid etching technique and bonding :
a) Enamel etching :
Etching : Removes surface continuants
Raise surface energy
Increase surface for bonding
Bonding agent drawn by capillary attraction into microporosities
Polymer tags are formed
Provide micromechanical interlocking
Etching depends on :
Thickness of enamel
Cervical enamel
• Thin
• Irregular prism structure
• Devoid of characteristic prism markings
So bonding not intimate near cervical regin
So increase microleakage
Dentin etching :
Earlier – discouraged because of
hydrophobic resin 
it opens and widens tubules

20. Result in increase permeability
So bacterial ingress
Recently  hydrophilic resins – create open tubules and porous intertubular
layer
So close adhesion
Prevents penetration of bacterial / toxins
• Even then- non uniform bonding due to :
• Thickness of smear layer
• Degrees of etching
• Wetting capacity
• Forces of polymerization contraction etc
Another types of leakage :
NANO LEAKAGE by sano et al 1995
Occurs within nano metrisized spaces around collagen fibres within fhydrid
layer
Can occur at bottom or along whole width of hybrid layer
Reduced by using the self etching/self priming systems
Cause for nanoleakage :
• Inability of adhesive resin to infiltrate into demineralized dentin
Leaves pores /spaces /voids
Predispose to accumulation of water/oral fluids

21. Degrades the bond
• If resin fully infiltrated into deminalized dentins - high modulus of
elasticity
• If resin fails infiltrated into deminalized dentins - low modulus of
elasticity
• Contact with water oral fluids deminalized dentin – low modulus of
elasticity
Glass Ionomer bonding agents
So new boding agents based glass ionomer technology or glass ionomer
boding agents
Eg : Scotch bodn multipropose pertac universal bond and
They have carboxylic acid groups which attach to dentin and attach
composite to glass ionomer.
Dilute resin modified glass ionomer cements :
Diluted version
Fingi bond II LC
Completely replaces commotional boding agents as –
• Chemical adhesion
• C.T.E. close of tooth
• Better sealing ability both with enamel /dentin.
4) Cavity filling technique :
Thick / bulk filling – induce significant shrinkage
High stresses generated

22. Lead to debonding
Small/multiple increments – Poly. Shrinkage controlled
Mostly preffered in class II
ClassV
Inserts :
(Beta quarts glass inserts – mega fillers)
Insets with modifiers made of lithium aduminosilicate glass
Give tooth appearance
Available in various sizes and shapes
Inserts are controlled by cavity size and shape
Filler content is more than resin
So decreased contraction
C.T.E. is 4x10-6/0 C which is low
No shrinkage/No matresorption.
Prepolymerised composite balls :
• Greater M.L. than inserts
• Because of high cumulative internal stresses generated during thermal
changes
• But it has beta quartz inserts which has C.T.E. close to dentin which
is expected to reduce additional stresses on the interface.
Soft start polymerization :
• Procedure involves short polymerization at low intensity followed by
the final cure at high intensity.
At gingival
margins

23. • Allows composite resin to flow during initial setting
• So minimizes stresses at interface
• And also prolonged curing allow greater inversion rate of monomer
component.
5) Direction of light source :
• Poly. Shrinkage is directed towards light.
• Curing from occlusal aspect.
Gingival increment shrinks occlusally
• So curing aids –
o Use – light directing wdges
- Flexible light guides
- Focusing tips
Facilate better curing in poor access areas (like gingival margins)
So shrinkage will be towards gingival margin
• Three sited light curing
• Buccal, lingual and gingival
• Better adaptation.
6) Sealing the marginal gaps :
Unfilled low viscosity resins
Applied overall after finishing and polishing
Eg : pit and fissure sealants can be applied
By Lutz et al (1986)

24. 7) Delaying the Finishing :
Time :
• Microleakage depend on time :
• Many authors advocati to delay finishing by 24 hours.
• Study by Fusayama and Kohno 198925
.
• Finishing after 3 month of insertion – considerable M.L.
• Finishing after1 day – almost no M.L.
But study by Yap et al 1998 :
• Finishing after 1 week – more microleakage
Because of stress during finishing effects the already marginal seal.
So finishing should be done immediately.
Variations in finishing techniques :
• Increase M.L – dry finishing
High heat on marginal adaptation
Recommendations :
• Rotary instruments
• Slow speed
• Light intermittent strokes
• With generous air coolants
• Use of soflex discs – good marign adaptation.
8) Use of cavity liners and bases :
 Ca(OH)2 GIC – common base materials
Used in deep cavities for pulp protection
Reduces the bulk of composite

25. So deduces the poly. Shrinkage.

26.  GIC :
• Chemical bond
• Hydrophilic
• C.T.E. close to tooth
• Fluoride reservoir
 Bilayering technique / sandwich technique.
 Light cure GIC better than chemical cure
Because adheres immediately
No ionic leach out
Harden cement resists stresses – so better adaptation
9) Use of composite inlay restorations :
Loting agent :
It bond to tooth using composite cementing medium.
It may be chemically cured/dual cured.
Light curing luting agents should not be preffered.
Because they lead to high conversion (of monomer) rote of inlay and
reduces availability of remaining un converted monomers for
co-polymerization with the luting resin.
Fails to bond chemically with inlay.
Chemically cured preffered than light cured
Because inlay may be 2 mm/more thick
So difficult to cure.

27. Microfilled preferred than hybrid luting reins.
Because less heavily filled materials (hybrid) tend to lose earlier by wear
mechanism.
Composite inlay :
Better
Because poly. Shrinkage takes place before cementation.
But failure of inlay to bond with luting resin so different methods :
1) Use solvent such as ethyl acetate to soften the cavity side of the
restoration.
2) Sound blasting with aluminium oxide abrasive particles of the cavity
side of rest.
3) Etching cavity side with 10% hydrofluoric acid.
10) Expanding matrix resins for dental composites :
• Resins expand slightly during polymerization
• Facilitate bulk placement
• Decrease M.L.
IV. MICROLEAKAGE
AROUND DIRECT GOLD RESTORATIONS:
Adapt to cavity walls more efficiently
Because :
1) High malleability and ductility
So good burnishing and adapts well to margins.
2) Short bevel on cavosurface margins
Facilitate burnishing /polishing
3) Insoluble in oral fluids

28. 4) Condensation – induce elastic compression
Adapts strong.
Microleakage may be due to :
• Improper compaction – in spaces / voids
• Non uniform stepping
• Type of gold selected
• Improper lines of force
• Inadequate condensation pressure.
Measures to reduce leakage :
1) Cohesive gold foils preffered – good seal because mat and
powdered gold are porous:
- Former should be gold foil – internal bulk
Then used an veneer
Prevent leakage
2) Uniform stepping preffered:
- Half to 1.4th
stepping – drive away air spaces
Adapt closely to underlying surface
- Always center to periphery
3) Lines of force:
- 900
to pulpal floor in center
- Then changed to 450 to cavity walls at periphery
4) Condensation force:
10 pounds – average force with 1 mm condenset tip.
Proper adaptation

29. 5) Restoration build up:
Done in convex form
Material should be always be banked on the cavity walls ahead of the
center.
Allows application of force in right direction and thorough adaptation.
6) Surface procedures:
Burnishing, finishing, polishing bring metal closer to tooth surface
Good seal.
V. Microleakage around cast restorations :
No close adaptation – 10-160µms gap
↓
so luting agent required
↓
low viscous luting agent preferred
↓
because it penetrate into irregularities of both tooth and rest
↓
so micromechanical retention
Advantages :
Now – adhesive luting agents available
↓
and also have chemical retention
intermediate cement layer-promote leakage
↓
because of solubility
increase solubility zinc phosphate, silicate, silicophosphate

30. • cement line may be exposed to oral environment
↓
as margins are not adequately and beveled and burnis heal
↓
because it is difficult to burnisher to reach ging areas in class II inlays
↓
when harder gold is used do to burnish
• Excessive taper
↓
excessive loads
↓
rest gives away by rotating on preparation surfaces
↓
break in the cement lute
Measures to reduce microleakage :
• Adhesive luting agents should be preferred
↓
chemical bonding
• In case of gold –
o Bevels placed properly
o Burnishing margins (malleable and ductile)
↓
so close proximity to cement surface, due to permanent deformation
o Good percentage of elongation
Type II and III – 20-35% elongation
o In case of high soluble cements (Zp, ZnSi phosphate, silicole >
0.04 – 0.10% solubility) burnishing should be delayed 24 hrs
↓
This allows for superficial few microns of cement to dissolve
↓
Then burnished
o In case of nonsoluble cements
↓

31. burnishing done immediately
o If rest have close fit within 20µms
↓
degradation of cement is resisted
↓
increase life of restoration
Microleakage around porcelain restorations :
• Dental porcelain is a brittle material
↓
low tensile strength
↓
if strain exceeds 0.1%
↓
fracture
↓
so bonded properly
• Earlier – bonded with luting cements
↓
high rate of failure
• Recently – luting resin cements
↓
dual cure
• Chemical bond strength
Initially improved
↓
later weakened by hydrolysis
↓
decrease bond strength after 1 year
↓
wear of cement lute at interfaces with inlay and tooth
• Interfacial gaps
Varies with diff. systems because of technique sensitivity
• Difficult to prepare ceramic inlays that precisely fit cavity.
• Fired ceramic inlays – depend on operator skill
• Ceramic inlays gaps wider than composite inlays

32. Measures to reduce microleakage :
• Operator skill and patience.
• Advances in adhesive technology
Resin luting cements better than luting cements
↓
as bond degrates with time
↓
ceramic inlay surface treated both mechanically and chemically
↓
1st
– acid etching done
- Hydrofluoric acid – for fired porcelain
- Ammonium bifluoride – for milled / cast ceramics
↓
give micromechanical retention
↓
etched surface than silanated to increase wetting and so improves
chemical retention.
• Resin luting cements should not be applied with one prior tooth bonding
procedures.
• Closure fit of restoration
o Operators skill and patience
o Glass ceramic restorations (dicor) – excellent marginal
adaptation.
Methods to detect microleakage :
Invitro tests tries to simulate oral environment by thermocycling. Yet
the dynamic nature of pulpodentinal complex and its defence mechanisms
cannot be easily simulated in-vitro. More so, the accumulation of plaque and
other agents might vary the microleakage results in vivo.
The various methods are described, however none of these method is
considered perfect till now.

33. Different tests –
1) Dyes
2) Chemical tests
3) Radioactive isotopes
4) Neutron activation analysis
5) Scanning electron microscopy
6) Bacterial studies
7) Electrochemical studies
8) Air pressure
9) Artificial caries
10) Pain perception
11) Reverse diffusion method
1) Dyes :
• Coloured agents like organic dyes used
• Have contrasting colour
• Agents used
o Methylene blue
o India ink
o Crystal violet
o Fluoroscein
o Rhodamine B
o Eosin
o Basic fuschin
o Erythrosine etc
Requirements :
• Should not bond to tooth / restoration
• Should be color stable under all conditions of investigation
Availability :

34. • Solutions
• Particle suspensions of different particle sizes
Technique
• Immersion of restored tooth in dye solution for predetermined period
↓
tooth removed, washed and sectioned
↓
examined under microscope for extent of penetration of dye
Limitations :
• Diff. conc of two dyes vary penetrations times from 5min-1 hr.
• Dyes may bind to tooth / restorations.
Eg : basic fuschin bonds to carious dentin and mistaken for large gap.
• Some dyes may be not colour stable
Eg : aniline blue – colourless in alkaline conditions such as in presence
of Ca(OH)2
2) Chemical tracers :
Reaction bt 1 and more chemicals taken plan
• Chemical used : 50% silver nitrate solution (or) 1% silver chloride
benzene 1,4-diol (hydroquinone) – photographic developer
• Technique
o 2 colourless chemicals react – produce an opaque ppt (usually
silver salt)
o Immerse extracted filled tooth in 50% silver nitrate solutions
which reacts with photographic developer (benzene 1,4 dio)
↓
opaque silver salt produced
Limitations :
• Diff. conc of two dyes vary penetrations times from 5min-1 hr.

35. • Dyes may bind to tooth / restorations.
Eg : basic fuschin bonds to carious dentin and mistaken for large gap.
• Some dyes may be not colour stable
Eg : aniline blue – colourless in alkaline conditions such as in presence
of Ca(OH)2
3) Radioactive isotopes :
• Ca, I, P, C, S, Rb etc used similar to dyes
• Technique
Immersed in isotope solutions
↓
Removed, washed, sectioned
↓
Autoradiographed to detect tracer
Advantages :
They can detect minute amount of microleakage
↓
Because of their small size – 40nm
Whereas dye smallest size is – 120nm
Limitations :
a) Subjective assessment of results (with using
steriomicroscope – subjectivity minimized)
b) High energy isotopes produce scatter on film –
mistaken for increased leakage.
c) Ca – have affinity to tooth / rest material – may
mislead the results
d) Expensive and technique sensitive
4) Neutron activation analysis :
Technique :
Restored tooth soaked in an aqueous solution of non-radioactive manganese salt
↓
Then tooth placed in core of nuclear reactor

36. ↓
Bombardment with neutrons takesplace
↓
Activates Mn55
to Mn56
↓
Radiation is emitted by tooth is measured to quantify the volume of tracer
present.
Limitations :
a) Inability to identify the points where rest. has leaked
b) Heavy exp costs
c) Effort of nuclear engineers and dentists required
d) Mn may be absorbed by tooth / rest
5) Scanning electron microscope :
• It is direct visual observation of rest adaptation to cavity because of high
magnification and depth.
• Used in both invivo and invitro.
• Earlier – used replicas of tooth
• Recently – evaluates rubber base impressions directly
↓
Reduces many steps (in accuracy decreased)
Limitations :
Potential to induce artifacts during specimen preparation.
6) Bacterial studies :
• Test the possibility of bacteria penetrating through or around rest.
Technique :
Immersed in the cultured broths
↓
Filling is removed
↓
Dentin sharing from the base of cavity cultured.
Limitations :

37. • Results are qualitative and not quantitative
• Marginal gaps of 0.5-1µm or larger – allow bacterial penetration
↓
smaller than this gap cannot be detected
↓
smaller than this gap allow toxins
7) Electrochemical studies :
Technique :
Insertion of electrode into extracted tooth in a way that it contacts base of
rest
↓
Once restored teeth sealed to prevent electrical leakage through natural
tooth structure.
↓
Then immersed in a electrolytic bath
↓
Potential is applied between tooth and the bath
↓
Leakage assessed by measuring current flow across as serial resistor
Drawback :
• Unsuitable for metallic rest
• Inability in invivo situations
8) Air pressure :
• Compressed air was used to test the marginal seal
Technique :
Compressed air is introduced through the root canal and pulp chamber
↓
loss of pressure is measured within static system
↓
microscopic examination of air bubbles at margins is noticed – subjective
view.
Disadvantages :

38. • Inability to use invivo
• Drying effect of compressed air
• Some air may leak before it enters tooth
Advantage :
• Tooth need not be destroyed and result can be quantified
a) Artificial caries :