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Dalia JibreelCons + Sheet 2 24/2/2014

Today we are going to talk about COMPOSITE RESTORATION TECHNIQUE with steps , we always say that when we make a composite filling we first do isolation then bonding then we put the composite (those are the main steps).We are going to talk about acid etching and how we are going to achieve the micromechanical retention? As a dentist you must know what do the acid we put and the bonding agents do to our enamel and dentine.When we do a composite filling the area around the tooth must be well isolated because composite binds micromechanically not mechanically as amalgam .Micromechanical means that there’re some things are going to get inside the structure of the tooth (in tags and pores ) microscopically.

Clinical technique : initial procedures :

1.local anesthesia.

2.cleaning the tooth : we do it for two purposes :

1- to know the real color of the tooth without any plaque ,external stains covering it , the site is more receptive to bonding.

2- to remove anything on the surface that will interfere with bonding.

We do cleaning with pumice to remove plaque , but we want to make sure it doesn’t have high fluoride content because it may interfere with bonding.

3.shade selection :

when we do shade selection we do it prior preparation because color changes due to dryness (tooth dehydration = loss of translucency) , and we do it on the tooth/area under going composite restoration (because sometimes teeth differ in color <some of them might be darker than others> ).

We do it because teeth mainly doesn’t have one color , it has more than one shade (ex. In class IV we might use A2, A3 and incisal shade > in order to achieve natural look ).

Shade guide gives us accurate information like when we put A2 composite shade on 1 mm/2mm/3mm thickness it gives us this shade …

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*the tooth might be divided to different zones of varying color and translucency.

Natural light is preferred.

* hold the entire shade guide near the tooth ,partially covered with the patient lip ,to stimulate the shadow effect , make a decision as quick as possible (30 sec) ( because adaptation of eye receptors occur then we won’t choose the right color).

*a mix of two colors might be necessary.

The last step we most do > we put small amount of composite on the tooth surface without bonding and we cure it , because upon curing the composite change in color.

3. isolation : perfect isolation means using rubber dam … some cases like class 5 , using super gingival retraction cord / cotton buccally and lingually to achieve isolation.

Adv : good bonding to the tooth structure , helps you in placement of the composite , reduce number of bacteria around the cavity .

contamination affect the bonding , also blood and saliva affect bonding and physical properties of the composite

Refraction cord : used in class V … we put it in the sulcus >> push gum away and avoid leakage of fluids inside your cavity.

we can use wedges for isolation. if margins get discolored that means there’s leakage.

4. occlusal assessment :

to determine the natural stop with the opposing teeth to avoid putting bevels or cavosurfaces over there .(example class III : on mesial marginal ridges and distal marginal ridges ) (class V ; mainly doesn’t have occlusion ).

Locate the contact on the tooth to be restored and also on the adjacent tooth .

restorative procedure :

1.matrix placement

2.acid etching

3. enamel and dentine bonding

4. composite insertion

5.finishing and contouring : we can do it in more than one visit not like the amalgam we must do it at the same time.

MATRIX PLACEMENT AND WEDGING :

we must do it before anything

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When a packable material is used a rigid matrix is necessary , to resist the deformation otherwise the matrix maybe flexible (anterior restoration).

MATRICES extends above the marginal ridges and below the gingival margin .

Composite matrices for anteriors : very flexible , very thin and transparent , may have retainer or without. Transparent : in order to transmit light while curing with light cure to all places . but also we can use it in composite restoration for posterior teeth.

Amalgam matrixes for posteriors

Each class has certain matrix (like class V have a kidney shape matrix and called cervical matrix , we just put it on the cavity ) (class III and IV we use MYLER strips , but in large class IV composite matrices we use for it CELULOSE CROWN (transparent )we put in it composite then we adapt it on the tooth).

wedges importance : it separates teeth , hold matrices in place & prevents overhangs(excess material at the gingival margins ).

Advantages of matrices :

1.confine the material to the cavity walls

2.development of the axial contour and contact

3.helps in isolation

4.limits excess material

wedges must be placed gingival to the gingival margin.

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ACID ETCHING :

Applying acid >> will cause micro-roughness (small pores) by demineralization using phosphoric acid (HP3O4) .

Etching and bonding enamel and dentine

*etching on enamel differs than that for dentine because they have different structures

ACID ETCHING (Enamel)Aim : creating micro-undercuts into which the bonding agents can penetrate , once polymerized becomes interlocked with the tooth surface and provides micromechanical retention.Etching of enamel affects the prism ends and core .1.transform the smooth surface of enamel into irregular surface (increase porosity > will increase retention )2.increses surface energy (just like when we drop water on sandpaper > the drop will spread because the wet angle is low ).

*bonding agents have a composition similar to composite without fillers only resin (can get inside and curing occur then it binds to the composite )

Advantages of enamel beveling : will increase surface area , esthetic advantage and also it expose the enamel ends that are more effectively etched >> therefore deeper undercuts will be created .

ETCHENIG ACID (Dentine)

Will also deminerlized but differ than enamel because its structure is not the same , enamel consist of minerals and a little pit organic material , but Dentine is vital tissue (collagen ,lot of minerals & dentinal tubules ).

Etching of dentine affect the inter and peritubular dentine resulting in opening of the dentinal tubules leaving an interconnected network of collagen fibers(because it removed the minerals).

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Dalia JibreelCons + Sheet 2 24/2/2014that results in :

1. Partial or total removal of the smear layer2. Demineralization of the underlying dentine (peri & inter tubular).

* smear layer : residual organic and inorganic debris , produced by tooth instrumentation , when we put the bonding agent if there’s still smear layer it will affect bonding. >>> fills the tubules as plugs , decreasing the permeability of the underlying dentine

demineralization up to 7.5 microns depending on the type of acid , application time and concentration

Demineralized dentine because of the acid etching > > dentinal tubules will increase in diameter.

Acid etching technique :30-40% phosphoric acid concentration.1. they found that if it was less concentrated , it will create a precipitate that it isn’t easily

removed and it will interfere with the adhesion.2. if it was high concentrated, it will dissolve less Ca and resulted in poor etched hat .

Phosphoric acid : blue in color in order to recognize it , either liquid or gel (better) .liquids are used when a large area is to be etched . gels are preferred for better distribution of acid on margins and bevels.

Leave it for 30 second for enamel but for dentine only 15 s because its demineralized and there’s no high sensitivity , so we start from enamel we put it before dentine in 15 seconds ,

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we apply it (0.5mm) beyond the cavosurface margin .(if it touched the adjacent tooth it will cause etching >> but later on demineralization occur after one day ).Then we wash the acid for 30 seconds (we put the acid for 30 seconds = we wash it for 30 seconds) Then we dry the enamel with air syringe >> enamel becomes mat and chalky (etched enamel , frosted appearance).

Wet bonding :

Dentine shouldn’t be over dried , because what left is collagen >>> and when collagen get over dried it will collapse >>> all pores will get blocked >>> no more bonding on dentine and a hyprid layer won’t be formed. So before putting the bonding agent dentine must be moist (shiny).

BONDING : by using bonding agents on both enamel and dentine

Bonding to enamel :Etched enamel (only 10-30 micrometer) >> then we put bonding agent (green in color)(resin without filler) >> then we put the composite (that contain both the filler and resin) >> and bonding occurs (one unit).The bonding resin penetrates to the irregular etched enamel by capillary action. Bonding enamel : bonding is micromechanical

Bonding dentine : When bonding resin is applied to the etched dentine , it penetrates the intertubular dentine forming a resin dentine fusion zone , called the hyprid layer . it also penetrates in the open dentinal tubules forming the resin tags. dentine is a vital tissue , dynamic structure not easily bonded adhesion depends on the formation of the hyprid layer

HYPRID LAYER : dentine in between it bonding agent.

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At the past we used to do priming for dentine before bonding ???

After etching alteration in minerals content of dentine occurs changing its free surface energy to lower value (opposite to what happened to the enamel).

Primers with higher surface energy are used to help in the penetration of the adhesive .

Primers (hydrophilic monomers ) applied first as a surface agent , enhances the wettability of the (hydrophobic ) adhesive resin.

Most modern bonding systems combined the primer and adhesive in one bottle.

(once you etched the dentine its surface energy doesn’t increase not like enamel ). we use the primer because resin is hydrophobic so in order to let it penetrate we first apply the primer which is hydrophilic enhancing the wettability to help bonding agent penetration ).

Bonding technique :

The bonding agent is applied to all surfaces with a brush , the dentine should be uniformly shiny.

Blow air gently onto the dentine and enamel to push the bonding agent inside to spread it and to remove excess (we don’t want to have a thick bonding layer because it will affect bonding because bonding is weak >>> so I want to have a minimum thickness of bonding layer to let composite bind on ).

Then cure for 20 seconds ( because it has resin so it needs polymerization but less than composite.)

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if contamination occurs >>> we should repeat the whole steps from the first step ( because contamination may contain proteins that will bind to the surface so we repeat from the beginning).

COMPOSITE INSERTION :

o A plastic hand instrument (incorporation of air bubbles) or a syringe is used ( as a gun). (we don’t use metal instrument because it might cause composite discoloration).

o Small increments maximum thickness of 1-2 mm are done prior curing to allow proper polymerization of the composite and reduce the polymerization shrinkage stresses.

o Light is placed as close as possible , curing each increment for 40 seconds.o Fill to an excess , after removal of the matrix , cure for 10 sec , from each surface .o When we do increments we don’t put bonding agent again , only the first one).o If we put light for 60 sec that wouldn’t change anything ( because the reaction is

polymerization <monomers changing into polymers> ) ( but if we put it less than 40 >here is the problem we must reput the light again to make sure the reaction is complete).

o The oxygen inhibited layer : it’s the last layer found on the surface that didn’t undergo polymerization due to the presence of oxygen ). (we get advantage from it because when we put a second layer above this one we are sure that they will get contact because no polymerization occurs on this layer).

o We don’t care about the last last last increment we put because we over fill it then we do finishing or we close it with a matrix if we don’t want to finish it (we will see the difference clinically in fourth year >> when we put matrix on class 5 , because its highly polymerized it appear shiny like a glass). ( if we don’t put matrix and we make curing >> the surface will be rough not polymerized because its an oxygen inhibited layer)

The last step is : COUNTOURING , FINISHING and polishing :

We use finishing burs : if there was high amount of composite we start with high speed then we change into low speed.

Aim : is to remove excess material , provide final contour and smooth surface texture. Countering and finishing is done directly after the curing. Special carbide or fine diamond (gives smooth surface) finishing burs are used. For each surface we use different shapes. Polish using rubber cups and polishing paste . Occlusal area : check the contact area with an articulating paper.

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Care must be taken not to remove the centric contact point. Because composite is sticky so we must use burs to get morphology. Sand disks : just like sandpapers (we start with the rough one then we change into the

smooth one ) >>> then we use the rubber or white stone / if we want it to look more shiny we put pumice (like tooth paste) and use a brush.

Finishing disks mainly for labial surfaces. but i recheck the occlusion before all these steps.

Polishing disks Finishing and polishing burs

Diamond bur composite finishing kit.

The EndI wrote everything in the slidesDo not hesitate to ask any questionBest Regards

Dalia Jibreel

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