On the last blog, A Guide In Choosing Better Composite Resins Part 2, I’ve discussed simply the function of resins in composite resins. On this blog, I will try to achieve simpler explanation on how fillers or inorganic materials can affect the type of composite resins you buy. My intention is not to delve into so much on its technicalities but to discuss the topic in a manner that you will be able to correlate it to your preferences, so, you can buy the right composite resins for your practice according to the what is important to you or base on your clinical case at hand.
Fillers or inorganic materials is one of the component materials of composite resins which is considered as the solid particles bounded together in matrix by silane coupling that affects the following characteristics of composite resin:
(1) Strength of Composite Resins
(2) Decrease Thermal Expansion
(3) Minimize Polymerization Shrinkage
(4) The Amount of Expansion Caused by Water Sorption
So, let’s take it one by one, on how the filler content of your composite resins will affect its mechanical, esthetic and handling properties. The filler content of your composite resins are affected by the following factors:
I. Type of Filler Used
II. Size of the Filler
III. Shape of the Filler
IV. Weight Volume of the Filler in relation to its Volume Resin Content and Coupling Agents.
V. Optical Index
How can the type, size, shape and weight volume of the fillers affect on the type composite resin you need to use in your dental restoration?
TYPE OF FILLER:
Fillers commonly used in manufacturing composite resins are the following:
A. Methacrylates- is the most well-known materials found in the hybrid composites. However, there are disadvantages in using methcrylates as fillers in composite resins, these are the following:
(1) Volumetric shrinkage
(2) Bacterial Adhesion
(3) Side effects due to Monomer Release
The manufacturers of composite resins, though, continue to try to improve and reduce the weakness of methacrylates. To reduce these negative effects, manufacturers have worked on materials adapting the individual components. The fillers is made on the following type of materials:
(4) Other Proprietary Oxides
To make you easily understand how these type of fillers affect your composite resins, I will try to give an example :
(1) When Quartz are used, the composite resin is clinically inert, strong and hard with high esthetic value. However, quartz can be difficult to polish and potentially can cause abrasion to the opposing natural or restored teeth.
(2) When Amorphous Silica are used, its composition and refractive index are of the same as quartz but it has less hardness with less crystalline-effect.
(3) When Glass Fillers with Heavy Metals are used, they have adequate refractive index and provide good radiopacity. However, it is not as inert as quartz and amorphous silica. It also weakens under exposure of acidic juices and oral fluids; more susceptible to wear and tear, thus, has a shorter functional lifetime.
The technology to develop the use methacrylates also gave birth to what we commonly hear as nanohybrids. They are advertised as universal composites which according to manufacturers can be used both in anterior and posterior restorations. These composites can have different types of filler particles:
(a) Prepolymerized, finely milled Agglomerated Nanoclusters
(b) Larger (submicron-sized) Glass or Silica particles in the range of 0.4 microns
(c) Individual nano-sized particles with a common size of 0.05 microns
Some Example of Brands of Nanohybrids:
(1) 3M Filtek Supreme XTE and Filtek Z250 XT
(2) Ivoclar-Vivadent IPS Empress Direct and Tetric Evo Ceram
(3) Coltene-Whaledent Miris 2 and Synergy D6
(4) Kerr Herculite Ultra and Premise
(5) GC G-aenial and Kalore
(6) Dentsply Esthet-X HD
(7) Tokuyama Estelite Sigma Quick
(8) Voco Grandio
(9) Kuraray Clear l Majesty
(10) Edelweiss Edelweiss Direct System Composite Resin
B. Organically Modified Ceramics (ORMOCERS)- the methacrylate has been partially replaced by an inorganic network. According to some studies done, the biocompatibility was not improved in all brands who uses this type of fillers.
Example of Brand of ORMOCERS: Voco Admira
C. Compomers- its goal is to combine the positive properties of glass ionomers with composite technology. However, it only partially succeeded on its aim because the fluoride release is low. The fluoride release of compomers increases quickly initially within 24 hours, but is also quickly decreases in due time. Compomers are most suitable for restorations in the deciduous dentition due to their low abrasion resistance.
Some Example of Brands of Compomers:
(1) Dentspyl Dyract
(2) Ivoclar-Vivadent Compoglass
D. Siloranes- Manufacturers have addressed problems related to shrinkage of resin-based materials in different ways, including increasing molecular weight and developing materials with ring-shaped molecules such as siloxanes and oxirans. These materials replaces the chain monomers in the composite matrix via ring- shaped molecules. These materials are hydrophobic and need to be bonded to the dental hard tissue with a specific adhesive system. But, it shows the following advantages:
(1) Low shrinkage leads to a lower contraction stress.
(2) Low water absorption and water solubility.
(3) Good mechanical properties.
Unfortunately, its been found in certain studies that these type of composites have low-translucent colors, thus, it can only be recommended to posterior restorations.
Example of Brand of Siloranes: 3M Filtek Silorane LS
SIZE & WEIGHT VOLUME OF THE FILLER:
Clinically, when you want to define the mechanical properties of your composite resins according to the size and filler weight-volume content, there’s a simple guide to follow. The size and the filler weight volume content of your fillers can be translated by the function you need from the composite resin in order to get your preference of importance. Your preferences maybe dependent on your dental case at hand. Thus, it correlates to the composite resin you want to buy. By rule, as the filler’s size and volume content increases, the following also increases in functional value:
(1) Reduction Polymerization Shrinkage
(2) The Coefficient of the Thermal Expansion becomes more like the natural tooth structure
(3) Increase on the hardness and abrasion-resistance against the opposing structure whether natural or restoration
(4) Increase on color stability
(5) Increase the depth of cure necessary
(6) Increases the stiffness of your restoration thus less in flexural strength
(7) Reduction on resistance to toothbrush abrasion and wear of the hydroxyapatite content of your natural tooth.
SHAPE OF THE FILLER:
In terms of shape of the fillers, ideally spherical shape of fillers incorporates the ability of load of more inorganic fillers thus improves its flexural strength that makes your restoration less prone to fracture.
OPTICAL | REFRACTIVE INDEX:
Optical or Refractive Index is also crucial quality when it comes to choosing the type and brand of the composite resins we buy. This affects the aesthetic value of your restoration, thus, becomes a critical factor of consideration. Refractive Index is affected when it comes to the type of fillers used.
What does it mean exactly?
Refractive Index means the degree of translucency similar to the tooth structure. Depending on what degree of refractive index that the manufacturer follows either the enamel which has refractive index of 1.6 degrees or dentin which has a refractive index of 1.5 degrees.
So, why is the degree of translucency important?
Translucency means the ability of your composite material to allow light to pass through, thus allows the appearance of the underlying background to show through. It can be described as partial opacity or a state between complete opacity and complete transparency. A higher value for the translucency parameter represents greater translucency; if the material is completely opaque, the value of this parameter is zero. Remember, translucency is significantly affected by polymerization, and the direction of change with polymerization (higher or lower) differs from one composite to another. Therefore, in cases where esthetics are critical, it is highly advisable to perform shade matching using polymerized composite. The translucency of tooth-colored restorative materials is considered a crucial optical property, comparable in importance to the shade of your composite resin, since the translucency will strongly affect the appearance of your restoration. The level of translucency can't be defined by the shade of the composite resin because each brands are created in different degrees of translucency by manufacturers. This means when we compare the level of translucency of same composite shade of one brand of composite resin to another, it may differ in degree, thus, sometimes we prefer the chameleon or masking effect of one brand better than another brand.
For Example: Ivoclar-Vivadent Tetric EvoCeram A2 is more translucent than Ultradent Vi-L-Escence A2
Knowledge of the relative translucency of proprietary composites can assist you in the choice of product to achieve optimal esthetic results when attempting to either duplicate the optical properties of the tooth being restored or overcome the effects of discoloration or the dark background of the cavity. Generally, the “opaque” and “dentin” composites had relatively low translucency, the “universal” or “body” composites had intermediate translucency, and the “enamel” composites had relatively high translucency. Your knowledge of the relative translucency of proprietary composites can assist you in your choice of material and the achievement of optimal esthetics.
Therefore, to even simplify more the explanation of what’s the relevance of knowing filler type, size, shape, volume and refractive index of our composite resins in clinical sense is that it addresses our understanding on what to use on each specific case we encounter in our clinic. Although, for economical reasons, we prefer to believe to the idea of one composite fits all, it is truly not the case. However, having said that, knowing what you generally encounter in your restorative cases in your clinic and understanding more how composite resins work based on its content, you will be able to choose the right type of composite you need to buy and use.
For you to be able to properly relate the 3 blogs I’ve written so far, I will give you an example in regards to my own preferences and what I actually use most of the time. However, please take note that I am NOT advertising these composite resins for you to buy. These are composites I truly use in my practice and have given me the results according to my preferences relative to my case at hand as I’ve mentioned in A Guide In Choosing Better Composite Resins Part 1. I am mentioning them to give you an idea on how you will be able to properly buy your composite resins NOT according to price and promotions it gives you but according to what you really want and need in your own dental practice to provide higher esthetic and durability value.
On my practice, after testing most of the brands of composites, I found that I prefer to buy individual syringes rather than buying sets of composites because I have discovered different preferences of brands and type of composite resins that I want to use according to my goal/s to achieve on restorative case at hand. Generally, I must have a less translucent shade, that provides more opacity for cases with no backing tooth structure such as Black’s Class IV Classification, Class V or those restorations which need masking due discoloration. On this I prefer, Ultradent’s Vit-L-Escence less translucent Enamel Shades Pearl Frost, Pearl Neutral. And, for cases of discoloration or porcelain repair to mask the metal, I used Opaque White. I require higher opacity as well for amalgam replacements, such as a combination of Ultradent’s Vit-L-Escence Enamel Shade Pearl Frost and its B1 Dentin shade or Ivoclar-Vivadent Tetric Evo Ceram Bleach L and B1 to be effective in masking the amalgam stains. For Nanohybrids, which I prefer to use in anterior restorations with backing tooth structure, I found higher or partial dentin translucency of nanohybrids effective, so, I can achieve higher esthetic value that can adapt to the shade necessary to look similar to the adjacent and opposing teeth or chameleon effect for single restoration, which I consider the most challenging restorative case esthetically. On this cases I prefer Vit-L-Escence, Edelweiss Direct System Composite Resin or Kerr Premise. I prefer, on the other hand, the use of Microhybrids on posterior restorations because the level of translucency is not as critical for me but higher level of abrasive-resistant quality is. For flowable composites, higher filler content and continuous fluoride release are critical for me as I normally used this type of composite resin for Black’s Class V Classification, sandwich technique as well as for sealants in adult pit and fissure cavities and in my very few pediatric restorative cases. In luting composites, I would choose any brand as long as I can also use it at the same time as a core build-up. Therefore, it must have good compressive strength and hardness for posterior restorations while having an acceptable flexural strength and elasticity to be good in anterior cases.
To make your restorations even better, I highly recommend the use of chlorhexidine (NOT the Mouthwash PLEASE) as an anti-bacterial agent before bonding and composite resin placement. Moreover, a resin-based base & liner is something I use all the time on the axial walls of any of my restorations because I want to ensure anti-bacterial protection in all of my restorations especially if I don’t use rubber dam for isolation. And, the use of composite wetting resin of Ultradent to solve any of my handling problems on my composite resins such as becoming flaky or sticky. I just find it easier to blend any composites with its use.
In conclusion, only you can define the level of importance of what type of composite resins you really need in your practice. However, knowing more about its content and understanding how it works in relation to your preference will enable you to wisely buy, choose, and use the right composite resin for your case satisfying both your and your patient’s need.
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