1 | P a g e

12

Rahaf Al-Jafari

Marah Qaddourah

…

Aya Al-asmar

2 | P a g e

This sheet contains the unavailable slides 😂+ if you are following with the record you may notice a little difference in sequence.

Dental Composite

• Dental Composite:

*A white restoration, may be used as a facing or a filling material.

*A product which consists of at least two distinct phases, normally formed by blending

together components having different structures and properties.

• You can use it to cover a defected tooth as a result of;

Abrasion, erosion, dental caries, or as esthetic restoration.

(Most common in elderly people).

• What is the purpose of blending components together?

Ans: *To produce a material having properties which could not be achieved from any of

the individual components alone.

*To get the advantages of all used materials in one produced material.

• Dental composites were developed in the 1960s. They quickly replaced acrylic resin and

silicate restorative materials. Their use continues to expand and replace other materials.

Composition of Composite

1. Mainly resin Matrix. (The main former of composite)

2. Filler (Filler doesn’t combine with resin matrix so we use point #3) (improve the quality

of the composite)

3. Silinating coupling agent. (The glue between 1+2) (Adhesion material)

4. Inhibitors, Modifiers and Opacifiers.

5. Initiator and Activators.

Minimal amounts of them may:

Increase shelf- life, increase working

time, decrease setting time, gives

optimal proprieties which are better for

clinical applications.

4+5

3 | P a g e

➢ Resin Matrix: (Main component)

• (Bis-GMA + TEGDEMA)

75 : 25

1. Bis-GMA: Biphenol A, and Glycidylmethacrylate.

* Main former of the resin matrix.

* 75%

2. TEGDEMA: Trithylene glycol dimethacrylate.

* Is a diluent organic chemical added to control the

viscosity of the final product.

* Only 25%; not a large percentage, why? Because it results a high shrinkage for the

material, although if we didn’t put this percentage the material becomes highly

viscous, and we can’t adapt it in the cavity.

3. UDMA: Urethane dimethacrylate.

* UDMA shrinkage is lower than GMA, but has other disadvantages; so, the main

product of the composite we use (Bis-GMA +EGDEMA), Not UDMA.

• Composite polymerization:

* The composite material we use is soft as a paste.

* In the past: They used to use chemical cure; (The material takes time to set by itself

when it is exposed to light).

* Nowadays: They use light cure mainly; (You shape the material as you want, once

you put the light it gets rigid).

- This rigidity called polymerization.

- By this rigidity, we don’t have to tell the patient not to eat on it till 15 minutes….

- The material gets its optimal strength by exposing it to the light cure.

* Polymerization of resin is responsible for Hardening and Bonding through forming

highly cross-link plastics.

*C=C is the functional group of both, principle monomers and the diluents.

Scanning electron microscope image for

fillers, glasses in the matrix.

4 | P a g e

• Modified matrix:

* Composite is a trend material, although may have shortcomings, pitfalls and

disadvantages, so they overcome those by modifying the matrix. (The matrix is the

reason of the pitfalls).

* So, they used inorganic materials other than the main organic (GMA, TEGDEMA,

UDMA), such as:

- Inorganic (ormocers).

- Acid (compomers).

- Ring open (silorrane).

* The question is: Why they are working in the matrix? Why they don’t want the

organic matrix? Why they are searching for adding acid, inorganics and fillers…?

Ans: The organic matrix has many shortcomings!

1. The weakest phase in the material.

Amalgam after 15 years remains the same with its cusps, while composite

doesn’t; because it is not strong enough to bear occlusal loads during

mastication.

2. The least wear- resistance phase of dental composite.

The matrix wears a lot, so the fillers overcome and improve the quality of the

composite.

3. Absorbs water.

All organic matrixes absorb water, thus hydrolyzes the material and makes

microleakage.

4. Stains and discolors.

Microleakages increase the ability to discolor the composite by stains.

To sum up: because those shortcomings they;

* Searched for inorganic ways to modify the matrix.

* They added fillers.

➢ Filler:

• Quartz, glass, Ceramic and/or silica.

• The first type of fillers was natural quartz materials (sand). They are strong, hard and

chemically stable in oral environment.

After trying; Those materials have many

disadvantages so they are not used now.

Organic ورجعو استخدمو ال

5 | P a g e

• They wanted to modify this filler (quartz filler), why?

Ans: Because in radiograph quartz appears black (as caries).

- if the composite is white, quartz appears black (we can identify it); but we can’t

know either it is quartz or caries???

- if the composite is black, quartz appears black (we can’t identify it)

Note: There are many reasons for having the composite radiopaque, we will know

them later on.

• So, how they modified the filler?

Ans: By the replacement of natural quartz with engineered glass material.

• The second type; Engineered glass materials which are formulated to have the proper

strength, hardness, chemical and optical proprieties for the usage in dental material.

• Different types, shapes, concentrations, sizes and combinations of fillers, are major

factors controlling properties.

For example: Material 20% filler, or 15% filler, or 5% small particles and 10% large

particles….

• They could play and manipulate the fillers as they want, why?

Ans: Because fillers affect the mechanical and physical properties of composites:

1. Hardness (rigidity, strength, abrasion)

* Organic matrix wears easily and not strong enough, so automatically by logic

(More filler; More rigid; Stronger; abrasion resistant)

2. Coefficient of thermal expansion.

* The material becomes more to the tooth structure, so thermal expansion becomes

better.

For example: Drinking hot water, and the material thermal expansion differs

than the tooth. If the thermal expansion was higher than the tooth; the material

expands more than the tooth, and vice versa.

-This difference could lead to micro gaps between the tooth and the material;

which leads to sensitivity and secondary caries.

3. Setting contraction.

* The MAIN disadvantage that all dental markets are trying to overcome, is

polymerization shrinkage or setting contraction.

6 | P a g e

* When the material gets rigid, it shrinks, and detaches from the sides.

* So, we have many ways to minimize the shrinkage. (لحتى نحل هاي المشكلة)

4. Color and opacity.

So that’s why we have different shades.

• Advantages of filler addition:

1- Reinforcement of the matrix resin resulting in

increased surface hardness (Vickers), strength, and

decreased wear (abrasion resistance).

2- Reduction in polymerization shrinkage. (sides

detaching increase)

3- Reduction in thermal expansion and contraction.

(becomes close to tooth coefficient)

4- Improved workability by increasing viscosity

(liquid monomer plus filler yields a paste consistency)

5- Reduction in water sorption (because we reduce the

organic matrix), softening, and staining.

6- Increased radiopacity and diagnostic sensitivity

through the incorporation of strontium (Sr) and barium

(Ba), glass. سوري الصورة مش واضحة بس النه فش ساليدات...

• Composites are most often classified by size of their filler particles:

1- Macrofill: strong but; rough surface, high wear, discolor X -Matrix + large filler particles, with occlusal load easier to chip away –> organic

matrix remains –> abrasion increases.

-Matrix + small filler particles, with occlusal load harder to chip away –>abrasion

decreases. So, they made midfill

2- Midfill: Hybrids (glass and silica), highest filler loading and highest strength, class I,

II, IV.

-If large particles chipped away, small particles remain.

3- Minifill: Hybrids (glass and silica), intermediate strength, less wear, smooth surface

(rough surface decreased), ant. and post. .√

-When strength decreases, become more esthetic.

(macrofill <midfall< minifill < microfill) by esthetic.

7 | P a g e

4- Microfill: Radio lucent, ESTHETIC,

smoothest surface, best wear resistance, lowest

strength, lowest filler conc. And size, anterior

restorations and class V.

-why it is the best esthetic? Because high

polishing, small particles makes it prettier

wow :P.

- But those small fillers are not as much

strong as hybrid; that gives intermediate

strength, esthetic, and sustain ant. + post.

forces.(سو الهايبرد أحسن إشي ألنو خير األمور أوسطها)

5- Small filler particles condensed together to give a large filler particle.

To sum up: all the modifications purpose to get a strong and esthetic material at the same

time.

➢ Silane coupling agent: The Dr. said that she doesn’t want us to know anything about it except:

It is very important for reinforcement of the polymer by the filler. Two constituents should

be bounded together.

➢ Inhibitors:

• Are added to the resin systems to minimize or prevent spontaneous or accidental

polymerization of monomers. مثال لما نفتح العلبة ما تنشف بسرعة

• Inhibitors have strong reactivity potential with free radicals.

• Thus, inhibitors have two functions:

1- Extend the storage lifetime for all resins. (shelf-life increase)

2- Ensure sufficient working time.

➢ Activator/initiator:

• Polymerization is achieved via a chemical reaction (chemical cure) or light activation

(light cure)

* Chemical cure: two pastes:

- Initiator (activator): benzoyl peroxide

- Accelerator: a tertiary amine

(e.g. N, N-dimethyl-p-toluidine)

When you add both together,

polymerization starts

8 | P a g e

*Light cure: - Photosensitizer (initiator): camphoroquinone.

- Activator (accelerator): Blue light 400-500 nm wavelength.

* Dual cure: chemical + light

- You rigid it by light, but some of it needs time (chemical)

- We mainly use it in veneers, when you put composite and the crown above it, light

cannot penetrate the crown to reach the composite, it only can reach the sides; so,

the rest should be chemically cured. (لحتى تتصلب لحالها)

- Cure: is the reaction between activators and initiator.

• As the light is very bright, direct viewing of the light

source will damage the eye, so even indirect (reflected)

observation of the curing light is contra-indicated (light

shields should be used) (either glasses or as you can see

in the picture بيجي درع واقي منه وفيه).

• Why nowadays we use light cure rather than chemical cure?

Ans:

1- Less voids (air bubbles)

-Any material requires mixing produces voids, and any material produces voids is

weak.

-So, as we know light cure doesn’t require mixing.

2- Color stability

-The accelerator (tertiary amine) absorbs water and makes discoloration.

-This accelerator is not found in light cure.

3-Working time and setting time under operator’s control. (very important)

-While you are shaping the composite it may become rigid, as in chemical cure.

-This doesn’t happen in light cure. (under my command)

Clinical application of composite

Two reasons why we don’t put composite as a bulk material:

1- The depth of cure: (the depth of penetration)

• The thickness of composite cured by a typical light source is called the depth of cure

=2mm.

9 | P a g e

-When you put a thick composite and light cure it; only around 2 mm will get rigid.

• The depth of cure varies depending on:

1- The time of light exposure.

2- The composite products.

3- The shade of the composite.

2-Incremental addition:

• The depth of cure is the first reason why we put the incremental layer (كتير مهم)

Cure ملم بدهم 2ما بزبط احط الحشوة مرة وحدة الزم طبقات، كل

• Placing dental composites in layers or what is commonly called incremental addition

has two benefits:

1- Assure adequate polymerization.

2- Minimize polymerization shrinkage.

• Configuration C factor = bounded / unbounded دايما بتجيب سؤال عنو باالمتحان

(The more the C factor the more the polymerization shrinkage)

Imagine a tooth and you want to put a composite in it

*If you put the composite as a once;

-Bounded surfaces=5 ماسكين السن

-Unbounded surfaces=1 للهوا

C factor = 5 (High polymerization shrinkage + as time pass, around the tooth we

can notice discoloration)

Number 1 in the picture or Class II )الحشوة على جانب السن(

*If you put the composite incrementally;

- Bounded surfaces =3 )يمين+االرضية+جوا(

- unbounded surfaces= 2 )الواجهة االمامية+ فوق(

C factor = 3/2 (Polymerization shrinkage decreases)

Note: *NEVER put a composite directly on two walls that

oppose each other. االحسن حشوة يمين وحشوة يسار وحشوة بالوسط

*If you put it on opposing walls, the center of shrinkage is in between, and it is going to

detach from the sides.

➢ Air inhibition: (oxygen inhibited layer)

• When composite materials are placed in increments, each increment chemically bonds

to the previous increment.

10 | P a g e

• The last surface (the last micrometers of the layer) is exposed to the air, and the oxygen

that is found in the air prevents the full polymerization of the material, so when you use

light cure and examines the layer with probe you will notice that the material is steaky

(unreacted material), which helps the next layer (newly set composite) to be chemically

bonded to it, when you finish; you start polishing the surface and removing the oxygen

inhibited layer, and the strong material remains.

• Chemical bounding occurs because addition polymerization is inhibited by the

atmosphere’s oxygen.

➢ Unreacted C=C bonds

• Not only can composite materials be placed in layers and bond together, but new

composite will bond to old composite because not all C=C bonds react when dental

composite sets, typically only about 75% of the C=C bonds react.

• So, it is possible to repair or add to a composite restoration by cleaning the surface and

adding new material.

➢ Shades: (very technique sensitive)

• Although composite has many disadvantages but it is very popular, why?

Ans: There is no material as the esthetic of composite.

• Opaque materials are designed to prevent the underlying color from showing through.

They are used to hide stained or discolored dentine.

- First you put a dark layer that mimics dentine, then layering as enamel, and translucent

incisal edges (no dentine).

- When you buy composite kit, you will find all the previous colors, even if the patient

has hypocalcification, fluorosis, white flakes! => you find materials in the composite kit

for them.

• To stimulate the translucency of enamel, some products come with shades called

“incisal” or translucent shades. These shades may actually be more translucent or they

may just have a blue appearance that mimics incisal edges.

• More common in anterior teeth, because posterior teeth are exposed to occlusal forces.

• Some people composite discolors from the margins because of contamination.

11 | P a g e

Note: *Contamination is another disadvantage of dental composites.

*Contaminations are: gingival fluid, blood, saliva…. (failure composite)

Types and properties of dental composite

1- Macrofilled composites 4- Hybrid composites

2- Midfilled composites 5- Flowable composites

3- Microfilled composites 6- Condensable composites

➢ Flowable composites:

• Flow into the cavity preparation due to their lower viscosity (more fluid).

• Manufactured have decreased the filler content of the material to reduce viscosity and

increase flow of these materials → a weaker, less abrasion resistant material results.

• Flowable composites are typically used as the initial increment of a composite

restorations and then covered with a hybrid material.

We don’t use it as a typical composite, we may use it in class II, to reach deep cavities,

then we put the typical composite on it.

➢ Condensable composites:

• These composites are again an attempt to make placement of the material easier.

Put it as a bulk then light cure it, and it polymerizes. But it has high polymerization

shrinkage.

• They have a filler particle feature that inhibits the sliding of the filler particles by one

another.

• A (thicker, stiffer feel) results and the manufactures call these products condensable.

Detecting composite restorations

• They do feel a bit softer than enamel to a sharp explorer.

• They appear either radiopaque or radiolucent on radiographs depending on the filler in

the product.

12 | P a g e

• They have evolved from being very radiolucent to having a radiopacity somewhat like

tooth structure.

• Barium and other heavier elements have been added to the engineered glass that is the

starting material in the manufacturing of fillers.

" ن مي عال

ال

مد لله رب ح ال ن ر دعوآهم آ خ "و آ

موفقين��