Micro-leakage Of Restorations 000

Definition: penetration of fluids, bacteria, ions along restoration / tooth structure interface. It is affected by : tooth & restoration & the condition of the oral cavity.

Effects Of Micro leakage 1- Penetration of bacteria , bacterial products & saliva into gap between restoration & cavity walls. 2- pulpal irritation , inflammation, & even necrosis can result from this penetration. 3-marginal discoloration & staining ( bad esthetics ). 4- bacteria can demineralize the cavity walls adjacent to the restoration leading to caries recurrence. 5- deterioration of the physical & biological properties of the restoration.

Recurrent of caries

discoloration

Methods Of Assessment & Recording The Severity Of Micro-leakage At Tooth \ Restoration Interface: 1- air-pressure technique. 2- bacterial penetration. 3- dyes ex: basic fusin or methylene blue. 4- radio-active isotopes. 5- scanning electron microscope (S.E.M.)

Dye penetration

Factors Affecting The Occurrence & Severity Of Micro Leakage: 1- dimensional changes in restorative materials during & before completion of the setting reaction. 2- dimensional changes of restorative materials after completion of the setting reaction. 3- solubility in the oral cavity . 4- inadequate condensation of the restorations. 5- occlusal loads. 6- presence or absence of smear layer.

1- Dimensional Changes Of Restorative Materials During & Before Completion Of The Setting Reaction. A- polymerization shrinkage of resinous restorations. B- contraction & expansion of amalgam. C- setting contraction of G.I.C. D- setting contraction of silicate cement.

2- Dimensional Changes Of Restorative Materials After Completion Of The Setting Reaction. A- difference in coefficient of thermal expansion between restoration & tooth structure . ex: * Amalgam about 2-3 times more than that of tooth. ** Acrylic resin about 7 times than that of tooth. B- modulus of elasticity. C- wear . D- creep. E- hygroscopic expansion.

C0fficient of thermal expansion of restorative materials relative to tooth enamel C.T.E (x 106 /C Tooth (crown enamel) 11.4 Dentin 8.3 Aluminous porcelain 6.6 Pure titanium 8.5 Type II glass ionomer 11.0 Pure gold 14.0 Dental amalgam 25.0 Composites 20.0-25.0 Denture resin 81.0 Pit and fissure resin 58.0 Inlay wax 400.0

3- Solubility In The Oral Fluids: * Solubility of glass ionomer cement. * Solubility of silicate cement. * Solubility of luting cement. - Zinc phosphate cement. - Zinc polycarboxylate cement.

4- Inadequate Condensation Of Restorations: Poor condensation of restoration against cavity walls leads to voids along the cavity margins & in the restorative material itself. This contribute to a higher degree of micro-leakage & inferior mechanical properties.

5- Occlusal Loads: A- in class II : application of occlusal forces on class II restored teeth may cause elastic deformation of the tooth substance. The facial & lingual walls can flex away from the restoration toward the outside , & so, increase width of the gap.

B- occlusal forces transferred from the restoration may create hygroscopic pressure on the fluid in the gap ( between tooth surface & restorative material ) which can be pushed together with bacteria into the dentinal tubules towards the pulp.

6- Presence Or Absence Of Smear Layer.

Microleakage Of Different Restorative Materials I – amalgam . II – composite . III – glass ionomer restorations . IV – indirect constructed restorations .

I- Amalgam Restorations All freshly seated amalgam restorations are leaky & that is why the use of 2 layers of copalite cavity varnish on the walls & margins of the prepared cavity in order to reduce the leakage around the restoration.

By aging in the oral cavity , the amalgam restorations will undergo tarnish & corrosion. The corrosive products of sulfides & oxides will precipitate along the interface leading to gradual closure of the micro spaces between the material & the walls of the cavity.

II– Composite Restorations: The freshly seated acid etched composite resin restorations exhibit tightly sealed margins against micro leakage opposite to amalgam.

These leakage proof margins are due to micro pores created by acid etching technique & the subsequent low viscosity resinous sealant which forms tiny micro tags providing retention & sealing at the restoration margins.

So At First : This hybrid combination blocks the leaky interface. But Due To : 1- Direction & degree of polymerization shrinkage. 2- temperature cycle in the oral cavity. 3- modulus of elasticity of the material. 4- type & magnitude & direction of masticatory forces applied to restoration . this relation soon ruptures creating a marginal gap.

Microleakage between Bacteria inside dentinal tooth and restoration tubule

This Marginal Gap Creates An Increasingly Deteriorating Conditions For Both Tooth & Restoration : For Tooth In Form Of : * Hypersensitivity * recurrent caries. * Pulpal affection.

* Physical. Restoration In Form Of : * Chemical. * Esthetical degradation. Due to leak out of ingredients & hydrophilic nature of the resinous matrix.

III – Glass Ionomer Restorations: Freshly applied G.I.C. Exhibit tightly sealed margins due to: 1- their adhesive potential. 2- low setting contraction . 3-coffecient of thermal expansion & contraction near that of tooth structure . by time : these tightly sealed margins will deteriorate due to solubility in oral fluids specially with increased acidity of oral fluids & ingested materials.

Resin modified glass ionomer

IV – Indirect Constructed Restorations . They are cemented by luting cements. Intra-coronally or extra-coronally Their Leakage Are Affected By : 1-solubility of materials . 2-its adhesive properties. 3-the length of the margins. 4-the nature of the marginal joint. 5-the type of bevel. 6-the acidity of oral fluids.

Composite Inlay It has many advantages over direct composite: 1- control of polymerization shrinkage. Which occurs outside patient mouth & only small luting cement leakage. 2- better mechanical properties (compressive strength, tensile strength & hardness.) Due to combined photo & thermal initiation & polymerization curing modalities.

3- better reproduction of the contour, contact & occlusal relations of the future restoration 4- better marginal adaptation. As the dual curing adhesive cement seals the marginal gap specially at the critical inconspicuous gingival marginal area. Specially after introduction of ultra-sonically aided cementing seating devices ( seimens sono-cem) . that provide a remarkable decrease in the film thickness & superior adaptation for the highly viscous adhesive resinous cement.

Prevention Of Microleakage 1- cavity preparation. 2- smear layer removal. 3- conventional varnish.

Complete infiltration partial removal complete removal

1- Cavity Preparation A- all cavity walls are smooth, clean & dry for maximum adaptation of the restoration. B- all unsupported enamel must be removed to prevent further fracture & marginal defects.

2- Smear Layer Removal: To obtain maximum adaptation of the restoration to the prepared cavity walls superficial smear layer removal should be removed , because it may interfere with adaptation & as a potential area for bacterial growth. N.B: It is essential to leave the deep portion of the smear layer “smear plug” which acts as natural cavity liner inhibiting bacterial penetration into dentinal tubules I.E : Decrease dentine permeability.

3- Conventional Varnish: Amalgam restorations are susceptible to early penetration at the amalgam / tooth interface. * The use of cavity varnish has been accepted as the most reliable method of reducing micro-leakage around amalgam restorations. * The conventional varnishes composed of resin dissolved in organic solvent such as acetone , chloroform or ether. * Two applications of copal varnish were more effective than one only.

Limitations Of Conventional Varnishes 1-donot bond at tooth structure or amalgam , but reduce only micro-leakage but not prevent it. 2- it acts as a mechanical barrier in the gap allowing micro-leakage between the amalgam & varnish , & between varnish & tooth structure. 3- it is not sufficient in reducing dentin permeability. 4- partial dissolution of the varnish .

NAno leakage Is nano metrisized spaces around the collagen fibrils within the hybrid layer that have not been completely infiltrated by resin

-It occur at the button of the hybrid layer or scattered along its thickness -The deeper the etching into dentin the higher the degree of nano leakage because the degree of resin infiltration not equal to depth of demineralization

Bonding to dentin in total etch adhesive system Dentinal substrate after etching the Dentinal substrates after priming smear layer has been removed the blue the water replaced by hydrophilic coloration represent the water content primer

After adhesive resin aplication

After polymerization resin infilterate polymerized dentin

Bonding to dentine in self etch adhesive system (after preparation smear layer and smear plug)

After application of acidic resin after application of adhesive

-For this reason the degree of nano leakage with self etching system is less than systems using acidic conditioners as single step -Nano leakage accelerates degradation of the bond and failure of the restoration

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