Lecture 11, Resin Composite Restorations II (2008 Lecture)

8/3/2019 Lecture 11, Resin Composite Restorations II (2008 Lecture)

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Resin composite restorations (2)

Advantages of resin composite as a post restorative material:

1.Esthetics. Some patients prefer all their teeth to be filled withcomposite which is tooth colored, unlike amalgam which is silver

(unaesthetic).

2.Conservation and preservation of tooth structure. If we comparecomposite preparation to amalgam preparation we notice that in

composite prep we are more conservative because we depend on

the adhesion of the composite on the tooth structure by using the

adhesive or bonding agent, while we need mechanical retention

for the amalgam prep.

- The prep tends to be shallower. For example in class V andclass 2 the cavity can be shallower.

- The prep tends to have narrower outline form. We dont needthe retentive form or the mechanical retention like inamalgam.

- Prep has rounder line angles. In amalgam we have definite lineangles while in composite we have more rounded line angles.

(Refer to slide 2) This is an example of a tooth that is prepared for

composite, we have 2 one distal and one medial cavity and

occlusal and buccal pit, for composite we can prepare these

cavities separately but if we are going to prepare for amalgam we

have to connect these cavity preparations together to make it like

an MOD because we need more retention. So again for

composite we have more conservation of tooth structure.


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3.Another advantage is adhesion to the tooth structure. Foramalgam we must remove all the undermined enamel because

amalgam doesnt add to the strength of the tooth structure so we

have to remove it because under occlusal forces the underminedenamel might fracture later on, for composite sometimes we can

leave some undermined enamel tooth structure because the

composite strengthens the remaining tooth structure by binding

to the enamel and dentin tooth structure. So the comp can

strengthen the remaining tooth structure where as amalgam cant

by the advantage of the bonging.

4.Low thermal conductivity. Amalgam can transmit heat forexample while drinking hot drinks whereas composite has low

thermal conductivity compared with amalgam. We compare

composite to amalgam because they are both direct restorations,

and also compare it to GIC to some extent.

5.Elimination of galvanic current. We said that this is an disadv ofamalgam

6.Radio opacity. This means on the radiograph it appears white.Why is this important? To know that there is restoration, to

detect for recurrent caries in margins, if we have open gap

between the restoration and the tooth, or overhangs. Before they

use to use microfilled composite which are not radio opaque so

we cant tell if there is a restoration, they look like the tooth

structure or like an empty area. But now all the available

composites are radio opaque.

7.Alternative to amalgam. This is an adv, so now have more choicesif we cant put amalgam we can put composite for post teeth.


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As any other material weve taken in dentistry we have adv and

disadv so we dont have an ideal material for direct restoration, each

one has adv and disadv. When we do restoration we have clinical

situation to compare to adv disadv, indication of each material andthen we choose what material to use that is best suitable for the

case that we are going to treat clinically.

Disadvantages:

1.Polymerization shrinkage. As we said in the last lec how when thecomposite polymerizes, the double bonds will become single bong

leading to volumetric shrinkage, the volume of the composite willdecrease, so when this happens it might affect the tooth, there

will be a gap between the tooth and the restoration, because

when we put the material its soft its not polymerized then we use

the light to cure it, once the composite polymerizes the volume

will decrease, we call this polymerization shrinkage. So there

might be a gap, this gap will cause what >> (the 2nd

and the 3rd

disadvantages)

2.Secondary caries.3.Post operative sensitivity. Because we have a gap now so the

fluids can pass through the gap into the dentinal tubules leading

to sensitivity. U should know that the polymerization shrinkage in

the post teeth is more because your binding to more tooth

surfaces (mesial, distal and so on) like when you bind to class 1 u

bind to how many surfaces > 4, therefore there will be no relief of

polymerization shrinkage, whereas in class 3 we bind to less

surfaces. So the highest polymerization shrinkage is in class 1 and

less in class 2 and it keeps decreasing in the other classes. It s not

imp to know details its just imp to know that polymerization


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shrinkage is more in post teeth than in ant teeth and in class 1

more than in any other class.

4.Decrease wear resistance. When 2 materials come together onematerial will take from the other, this is what we call wear.Because on the occlusal surface of the post teeth, when we

restore class 1 or 2 the force is more, so the wear is going to be

more in the post but this is overcome with the new composites

called universal composite and we can use it for both ant and post

restorations. They still wear but to a lesser extent.

5.Other mechanical properties. You took them maybe in dentalmaterial, fracture toughness, high degree of elastic deformation,and CTE. All of these have also improved with the newer

composites because of the filler loading increase; like in

nanocfillers, they have improved physical properties. Now the CTE

in composite is very important because its different form the

tooth structure, in GIC the CTE is similar to dentine but composite

CET is higher, meaning if we have hot or cold the material will

either contract or expand so because of this composite and dentin

will expand and shrink at different degrees leading to cracking and

crazing of the tooth which will cause tooth fracture later on (and

also fracture to the restoration). But in GIC because the CTE is

very close to dentine, so they used to call it a dentine

replacement material because they expand and shrink at the

same degree.

6.Water sorption. Composite can absorb or adsorb water, but this isalso improved in the new composites.

7.Variable degree of cure. And this is more in the self cure than thelight cure, during the mixing the two pastes. But now variable


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degree of cure in the depth of the composite and thats why we

have to cure it in increments because the light does not exceed 1-

2 mm of increment.

8. Inconsistent dentin boding (marginal leakage). Also this isimportant. Although composite adheres to tooth structure this is

an adv, but the adhesion has some problems.

9.Technique sensitive. so we have to have moisture control , wehave to be very delicate when we acid etch the dentine, too much

water and too much dryness is not preferable, we have to have in

between because it will affect the bonding this is what we mean

by technique sensitive, and moisture control (no blood no salivano water) during placement.

Indication for post composite, where should we put it:

1.Esthetics should be a prime consideration. So if the pt is willingto put an esthetic restoration in his post teeth then esthetics is

the prime consideration because its tooth colored.

2.The faciolingual width of the cavity prep should be restrictedto no more than one third of the intercuspal distance and in

class 2 the gingival margin should be on the enamel. Which

means in class 1 the occlusal coverage for composite should be

minimal, y3ni if the width which is the faciolingual width or we

can say the isthmus width in class 1 should not exceed 1/3 ofthe intercuspal distance this is theoretically, sometime we

dont stick to this rule sometimes I put composite even if the

cavity prep was more, but ideally speaking it should be this

way, we said the wear resistance is less with composite so if


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more tooth structure is removed, this means more composite

is exposed to forces leading to wear. For class 2 gingival margin

should be on enamel, this is imp, we have 2 problems here 1) if

the gingival margin extends below CEJ or below enamel,moisture control will be difficult, 2) bonding to enamel is

better than bonding to dentine, and so if we go deeper into

the gingival floor we will start binding to dentin, so binding to

enamel in the long run is more reliable than to dentine.

3.Centric occlusal stops should be primarily on enamel. This isrelatively the same as the 2

ndpoint, which if the occlusal table

increases the occlusal forces or the occlusal stops or occlusaltouching will be on enamel. We want it more on enamel than

on the restoration.

4.The pt should not exhibit excessive wear from the clenching orgrinding. We call this parafunctional habit, and this is reflected

by the pt, how do we know? They will develop wear facet on

their teeth which is the loss of some enamel on the occlusal

surface this means the pt has parafxnal habits, when pt has

bruxism (when pt tends to press on their teeth while they are

sleeping). Btw the teeth must touch each except during eating

so if they have parafunction, that means that the pts teeth

come in contact in times other than eating, y3ni more than the

functional habits (eating) >> resulting in loss of enamel tooth

structure

5.The tooth must amenable to isolation. Moisture control.Now we are going to talk about something which is related to

class 1 composite...it is easy, it doesnt need a lot of talking


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because in class 1 we want to remove caries and put

composite as usual. (The dr said she wanted to add on the

slide)

Before we talk about class 1 were going to talk bout

PRR it is something like class 1 but we do it with composite we

call it preventive resin restoration:

Limits preparation to pits and fissures that are carious. If the resultant

cavity is limited to narrow and shallow opening of the fissures, a resin

sealant (fissure sealant) or flowable composite is placed. If the

additional tooth structure is removed, resin composite is placed in the

cavity and then remaining fissures and composite are covered by

fissure sealant.

Which means sometimes the occlusal fissures as u saw when we were

practicing caries removal in the lab on natural teeth, sometimes ur in

between if its occlusal caries or fissure caries or staining, so sometime

Im not sure if it is or not and the pt is high caries risk so Im not going

to send him home because Im not sure, so what we do usually is PRR. I

open the fissures or grooves with a small round bur on high speed just

to investigate them, if we have deep fissure and stained fissures and we

are not sure those are carious or not, because it s very difficult

sometime to diagnose caries on occlusal. Btw the occlusal caries cant

appear on the radiograph, 7ata if we took bitewing, only if they become

involved in dentine they will appear. So if the fissures are deep and

stained I use a very small round bur on high speed and open the

fissures, then we do acid etching and put fissure sealant to block the

fissure on all the occlusal table (opened and not opened or if they

arent carious). Now lets say that we discovered that there some caries


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(in the first situation it was limited to enamel, it didnt got to dentine so

we put sealant or flowable composite), but if it extended to dentine

then we have to etch, bond, composite then we cover all the fissures

and composite with sealant. Both of these situations are called PRR.

Advantages of PRR: Conservation of tooth structure: we dont want to remove too th structure from

the beginning.

Enhanced aesthetics. Improved seal of the aesthetic material to the tooth structure. Minimal wear of the tooth, because there is a limited amount of the structure

missing.

Good longevity: it lasts a long time in the patients mouth. Indications of PRR:

PRR is indicated when there is a minimal to moderate loss of the tooth structure,

and its not indicated when there is an obvious lesion (we put restoration

directly).

Technique we use in PRR:- We use a small round bur to open the fissure on high speed because we are

cutting enamel

- Removal of the carious dentin and the unsupported enamel.- Acid etching and bonding as any composite restoration.- In case of shallow cavity (limited to the enamel), sealant of flow-able

composite is used.

- Resin composite is used to fill deep areas if the cavity is extended to the dentin-

Then the sealant is placed to cover the composite and the unprepared fissuresand pits.

Preparation composite in deep areas fissure sealant all over the occlusal

surface


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Class II composite restoration:- Pre-wedging: it means that we put the wedge

before preparing the tooth, and this has a lot

of advantages.The most common issue that occur after doing a

class II composite restoration is leaving a light or

even a small proximal contact between the teeth,

this result in food debris accumulation and may

cause irritation to the gingival, so our goal is to

keep a good tight proximal contact.

- The matrix band we use is thick, so after applying the composite and removing theband it will leave a space between the two teeth caused by the thick matrix band.

- So in pre-wedging, we put the wedge and the teeth will separate from each other,then we prepare the cavity while the wedge is there, then we put the matrix band

and apply the composite with a little bit extra amount, then we remove the wedge

and the teeth will come in contact.

- The other advantage of pre-wedging is protecting the gingival from the bur in class IIpreparation.

- And also protecting the adjacent tooth by separating it from the other tooth- The preparation of class II composite restoration should be limited to the carious

tooth structure.

- If there is two separate lesions on one tooth we work on each one separately becausewe are not depending on the mechanical retention.

- Bevel placement on class II composite is a controvertible issue,, there is an argumentswither to do it or not.

- The composite should be applied in the cavity by increments, because relatively wehave a deep cavity so we are not sure if the light will pass through all the restoration

and reach the bottom, also it helps in minimizing the polymerization shrinkage.

This problem was solved in the amalgam restorations by condensing the amalgam against the matrix band

The result should not be a very tight contact or a light contact,, just something in between


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Matrix bands:There is two types of matrix bands we use in composite.. There is the metal one and the

celluloid strips we have used in the anterior restorations, and each one have advantages

and disadvantages.- The metal matrix bands is easier to handle and control , and this is opposite to the

celluloid strips which is very hard to control it

- The problem with the metal matrix bands that it doesnot pass light and this is solved by extra light curing the

composite from Buccal and lingual areas after removing

the bands.

- We have another type of matrix band which we use inthe private clinics: its called sectional matrix bands and

ring, these bands have two advantages:

& they are thinner than the metal band& the ring can do a little separation between the teeth and

replace the wedge.

Finishing of class II composite restoration:- We use a finishing diamond burs to remove the excess composite on high speed,

also we use the strips for the inter proximal excess.

- And for producing the detail anatomy we use a flame shaped diamond burs

- Aluminum Oxide for smoothening.

THE END

DONE BYAfnan Hamad & Abdullaziz Alyahyawi

Sectional matrix band and ring

Lecture 11, Resin Composite Restorations II (2008 Lecture)

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