MICROLEAKAGE
Introduction :
The goal of operative dentistry, undoubtedly is to restore the tooth to
its form and functions...
Clinical implications :
1) Post-operative sensitivity :
• Due to direct communication between oral fluids and pul and it.
...
4) Marginal discolouration :
• Evident in esthetic restorations
• It leads to accumulation of subsurface interfacial stain...
o Leads to leaky rest margins.
(Table 23.1 Sikri page 551)
2) Polymerization Shrinkage :
• Occurs with polymeric materials...
o Presence of water
o Swear layer
o Composition of enamel and dentin
o Surface roughness etc.
b) Influence by operator :
•...
Best way – remove natural smear layer but not smear plugs
Replace with sterile, inert and non toxic synthetic smear layer.
Factors controlling bacterial penetration :
a) Size and nature of the gap :
• Varies with different rest materials – 10-50...
GIC, silicates, compromise – release fluoride into gaps
Have antimicrobial effect
Silver, tin, mercury – antimicrobial eff...
Restorative materials and microleakage :
I. Fresh mix condensed – does
not adapt closely
10-15 µm gap
but it is self seali...
Measures to reduce :
Amalgam microleakage :
1) Types of alloys :
• Different types have different leakage
• Spherical allo...
3) Burnishing :
• Adapt material to margins – (so decrease microleakage)
• Spherical alloys – no reduction in micreleakage...
7) Bonded amalgams
Have shown to over come microleakage
8) Use of gallium alloys
It has high wetting ability
II. Microleak...
Effects marginal integrity
Prevention :
1) Proper manipulation
• Liquid/powder ratio-if lower – increase solubility
• Plac...
• As they tear away material at margin – marginal ditching
4) Protection from moisture
• During fonishing – apply Vaseline /petroleum jelly
• Final protection – 2 coats of varnish/u...
Within limits of can with stand its bond strength
In exceeded plastic/elastic deformation
Separation of interface
• Mastic...
Greater flexibility during shrinkage decreases contracting forces
It has larger water absorption capability
So decrease M.L.
2) Cavity design :
Conservative :
So decrease polymerization sh...
Facial and lingual bevels in proximal box
Increases M.L. (75%)
(1998 (48))
3) Acid etching technique and bonding :
a) Enam...
Result in increase permeability
So bacterial ingress
Recently  hydrophilic resins – create open tubules and porous intert...
Degrades the bond
• If resin fully infiltrated into deminalized dentins - high modulus of
elasticity
• If resin fails infi...
Lead to debonding
Small/multiple increments – Poly. Shrinkage controlled
Mostly preffered in class II
ClassV
Inserts :
(Be...
• Allows composite resin to flow during initial setting
• So minimizes stresses at interface
• And also prolonged curing a...
7) Delaying the Finishing :
Time :
• Microleakage depend on time :
• Many authors advocati to delay finishing by 24 hours....
So deduces the poly. Shrinkage.
 GIC :
• Chemical bond
• Hydrophilic
• C.T.E. close to tooth
• Fluoride reservoir
 Bilayering technique / sandwich techn...
Microfilled preferred than hybrid luting reins.
Because less heavily filled materials (hybrid) tend to lose earlier by wea...
4) Condensation – induce elastic compression
Adapts strong.
Microleakage may be due to :
• Improper compaction – in spaces...
5) Restoration build up:
Done in convex form
Material should be always be banked on the cavity walls ahead of the
center.
...
• cement line may be exposed to oral environment
↓
as margins are not adequately and beveled and burnis heal
↓
because it ...
burnishing done immediately
o If rest have close fit within 20µms
↓
degradation of cement is resisted
↓
increase life of r...
Measures to reduce microleakage :
• Operator skill and patience.
• Advances in adhesive technology
Resin luting cements be...
Different tests –
1) Dyes
2) Chemical tests
3) Radioactive isotopes
4) Neutron activation analysis
5) Scanning electron mi...
• Solutions
• Particle suspensions of different particle sizes
Technique
• Immersion of restored tooth in dye solution for...
• Dyes may bind to tooth / restorations.
Eg : basic fuschin bonds to carious dentin and mistaken for large gap.
• Some dye...
↓
Bombardment with neutrons takesplace
↓
Activates Mn55
to Mn56
↓
Radiation is emitted by tooth is measured to quantify th...
• Results are qualitative and not quantitative
• Marginal gaps of 0.5-1µm or larger – allow bacterial penetration
↓
smalle...
• Inability to use invivo
• Drying effect of compressed air
• Some air may leak before it enters tooth
Advantage :
• Tooth...
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Microleakage/ orthodontic course by indian dental academy

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Microleakage/ orthodontic course by indian dental academy

  1. 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. 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. 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. 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. 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. 6. Best way – remove natural smear layer but not smear plugs Replace with sterile, inert and non toxic synthetic smear layer.
  7. 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. 8. GIC, silicates, compromise – release fluoride into gaps Have antimicrobial effect Silver, tin, mercury – antimicrobial effects.
  9. 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. 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. 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. 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. 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. 14. • As they tear away material at margin – marginal ditching
  15. 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. 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. 17. Greater flexibility during shrinkage decreases contracting forces
  18. 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. 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. 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. 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. 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. 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. 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. 25. So deduces the poly. Shrinkage.
  26. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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 :

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