Dental Composites II
Dr.sahar taha
Date:16-3-2011
DENTAL MATERIAL
Types :
The main 6 types are:
1. macrofilled composites
2. microfilled composites
3. small-particle composites
4. hybrid composites
5. flowable composites
6. condensable composites
we will talk about every type
macrofilled composites
§ As its name indicate ,macrofilled mean the particles are large (macro) ,this type is the first type of composite to be developed in the 1960s
§ the type of the filler is quartz with particle size = 10-25 microeter
*quartz is naturally existing filler
§ Its filler content is 70-80% by weight
And as we studied before when the filler content increased ,the physical properties become better
So when they first made it they thought that 70-80% gives an indication that this is good physical properties,but they discovered later that were not what they want or expected
And u should notice that ( filler content by weight is different from by volume ) ,so 70-80%by weight is equal nearly to 50%by volume
(by volume) is more related to the physical and mechanical properties and the types of the composites than (by weight) ,so we give more attention to it
Because its about the surface area of the filler content and the surface area of the weakest phase
physical properties are determined by the volume percent ,so it is the most admirable for the scientists ,but the weight percent is easier to calculate than the volume percent because sometimes we have big particles and we crash them in certain ways and get many sizes and the shape is irregular so it is very hard to calculate the surface area or volume percent for these particles so it is easier to calculate the weight percent
sometimes they have regular shape,so it is easy to calculate the volume percent
again,the large size of the filler cause the rough surface to be bigger and the wear resistance less ( friction with the tooth structure and-or food bolus will result in removing these large filler particle from the matrix causing a huge dimensional change and a huge area with less abrasion
resistance matrix so its abrasion is very high
so this type has fair physical and mechanical properties except for the wear resistance and surface roughness
some properties of the macrofilled composites :
§ the large size of the filler results in restoration that feels rough to the dental explorer and can appear rough to the eye
§ plaque accumulation and staining is greater than other types *
§ the typical macrofilled (with its high content of quartz)will turn slightly gray when rubbed with an instrument in procedures using a metal spatula to mix chemical cure composites,BECAUSE the quartz has glass and its hard so it will easily abrasio يحك the metallic instrument and the metallic particles will go in the composite and made it gray
§ the strength and other physical properties EXCEPT (wear resistance and surface roughness ) are adequate for restoring the low stress-bearing surfaces of the POSTERIOR teeth
why posterior teeth?
because the posterior teeth are rough and we can’t use this composite for anterior teeth because it will show and will look like something wrong with the tooth
why low-stress bearing surfaces?
Because this composite has low wear resistance
§ excessive wear when used for class I and II restorations limited posterior use**
§ its strength is fair,its abrasion resistance is poor, its abrasion is high , its thermal expansion is fair,and its current uses is few
*any rough surfaces in the oral cavity will be subjected to more attachment of bacteria and more bad deposition of material and this is a huge disadvantage
** class I & II they are where the caries occur on the occlusal surface of the posterior teeth
Class I on the occlusal surface and II on the occlusal but on one of the proximal surfaces (mesial and distal )
We will take this in the forth year .
Microfilled composites
Because of the many disadvantages of the first type ,they tried to develop another type of composites
§ This type was developed in late 1970s
*when the diameter of the particles or size decreases,the amount of matrix needed to encircle this part will be more because the surface area of many small particles will be bigger than few big particles
*So when the surface area bigger ……the amount of matrix needed will be bigger and then the percentage of the filler will be less
§ The problem with the microfilled is the low percent of fillers 40-50% and that was the largest amount they could put
§ The particles size is far smaller than macrofilled, 0.03 to 0.5 micrometer
§ The very small particles are typically fused silica
*some girl asked the Dr. about the difference between the silica and quartz ,the dr. answered silica is synthesized and quartz is naturally existing ,but basically ther are the same
*the more the particles are smaller ,the more there is silica more than quartz so it will be synthesizing
§ Since the particles are very small that mean we can get very nice polishing surface and this is a huge advantage, so it can be polished to very soomth and lustrous surface similar to enamel,it is very nice for anterior teeth
§ The surface area of the very small filler particles require much more resin (big surface area) to wet the surface of the filler particles,the high resin content results in (disadvantages )
*high coefficient of thermal expansion
*lower strength
*more wear,less wear resistance cuz of the more the matrix ,the more the wear
*has viscosity
*more setting contraction
§ Smooth,lustrous composite restorations were a significant improvement over the available macrofilled composites
§ It is used when the esthetics الجمال are the dominant concern (classes IV,V) like in anterior teeth ,and we don’t use it in the posterior teeth because of the low abrasion resistance and the low strength
§ ***It is used in class V restorations ,at the CEJ,as it has a low strength it has a specific use in the cases of the areas of CEJ on the buccal surface ,because these areas are low stress-bearing areas (they are not an occlusal or insical areas so there is no much stress on them ) so what happens on these areas?
When the opposite teeth comes together ,they exert some later forces on each other in the mastication and occlusion,so there will be a micro flexing movement in these areas ,so if we put something that extra hard like a macrofilled so it will not flexe with the structure and will come out of the tooth,but if we put sth that has low modulus of elasticity and flexes with the tooth better than the strong composites
** the main forces on the teeth are the axial or the vertical forces , but because our teeth’s surface are not flat but have cusps inclines so every vertical force on these surfaces will have a vertical vector and a lateral vector and this affect the most the CEJ area ; because the CEJ area are the weakest area ,the root for example is embedded in the bone.
The lateral forces from the occlusion will affect mostly the CEJ area
§ Its strength is low,its abratsion resistance is good(small particles)
§ Thermal expansion is poor
§ Current uses in class III,IV,V and veneer
**veneer : a thin layer of dental restorative material
Small- particle composites
§ Were developed in the 1980s
§ Because we haven’t got the ideal composites, we had to have sth else ,and the fine or small particle were developed ,this type is between the macro and micro composites
§ Were filled 80-85% by weight with average particles 1-5 micrometer in size ,this is give it good strength so it can be used in the occlusal surfaces of the posterior teeth in class I,II restoration
§ Abrasion resistance and thermal expansion are good
§ Wear has got better than macrofilled ,and the strength than the microfilled
§ With least amount of resin,its composites have the least polymerization shrinkage and best physical properties
§ The problem that every particle that is bigger than 1 micro, will be visible to the human eye,so while the surface is not as rough as macrofilled ,it is not as smooth as microfilled
§ With this improvement ,it wasn’t good enough for use in the anterior teeth and limited use for the posterior teeth (class I,II)
§ U can use either silica or quartz
Hybrid composites
§ Developed in late 1980s
§ As the name indicate ,it mixed two kinds or sizes of particles or fillers
§ It is between the micro and small particles,so we can get a good composite
§ Their filler content is 75-80 % by weight
§ Average size is 0.5-1 micro in size but have a wider range of particles 0.1-3 micro
§ They are strong and polish well
§ Their abrasion resistance is very good,and the thermal expansion is good
§ Their physical properties as good as the small particles
§ They are acceptable for the posterior teeth (class I,II)
§ Their finishing is good but not as good as the microfilled,still it is one of the best ,so we can use it for anterior teeth (class III,IV) .In the finishing ,the microfilled is the best due to the smallness of the particles
§ This type is universal, u can use it every where
Flowable composites
§ Viscosity is related to the fillers content, when the fillers increase ,the viscosity increases
§ So we want it fowable,that’s means almost no filler content or very very small filler content
§ Decrased filler content>>>>reduce viscosity >>>>increase flow of these material >>>>a weaker .lees abrasion resistance material>>>very quick wear>>>can’t put it on the occlusal surface only and directly
§ They are typically used as an initial increment then covered with a hybrid material,they used to cover the details in the teeth
§ They come in syringes ,injected directly into the cavity
§ We should be careful not the two layer to be separated ,cuz we will have problems
§ Sometimes we use it in the fissures on the occlussal surface ,because these fissures are the first site of caries,so we filled it with this composites
Condensable composites
§ Their placement easier
§ Inhibits the sliding of the filler particles by one another
§ A thicker ,stiffer feel results
§ High viscosity ,more filler content >>> use in the posterior teeth not on the anterior
§ Don’t differ a lot than the hybrid
Best of luck,
Yasmine El-Chalbi
Dedicated to all of you my friends and colleagues
Especially to
Hala ,yamine,eman,raghad,sally,rawan,layal
Hello all this is mouhamed Garalleih, I would like to correct some mistakes in my sheet, dental material, lec# 5
Page1: *note that the sitting reaction of composite is addition polymerization. (add the word addition)
Page2: under history: first paragraph: silicate restoration- instead of- fabricate restoration
Page 10: last paragraph: camphorquinone -instead of- anthraquinone.
(Sorry for the mistakes and you are more than welcomed to correct any other mistakes you find J J)