A Guide to Selecting Dental Composites

You have a lot of choices when it comes to dental composites. However, as many marketing companies will tell you and clinicians will agree, all composites are not created equal. Choosing the best material requires assessing the particulars of the case and the details of your composite.

There are a few different ways to distinguish one composite from another. Some are more pertinent to performance than others. Let’s take a closer look at the types of dental composites and how they affect the potential outcomes for your restorations. 

The two physical properties of dental composites that most clinicians evaluate are mechanical and esthetic:

• Mechanical properties refer to the strength of the composite, how it wears in the patient’s mouth, as well as its bond strength and adhesion. In other words, how it performs physically. 

• Esthetic properties refer to the finish and polish of the material, or, to put it simply, how it looks. 

Dental composites have since been working to improve both of these areas in different ways since they were first introduced as a restorative material. Composites are made up of a few elements that, when combined, work together to make a flexible and durable dental material. One of the components of any composite is the fillers, which are typically pieces of glass or ceramic that are included in the resin matrix to give composite its strength. 

At first, materials developers used the filler size to improve mechanical properties and esthetics. In the middle part of the 20^th century, the filler sizes in the first dental composites were much larger than they are today, coming in at 10-50 micrometers.¹ These are macrofills. When it came to the first resin composites’ mechanical properties, bigger was better; these composites with large fillers were strong and durable. 

However, macrofills did not finish and polish well. Moreover, the large particles were sometimes big enough to see with the naked eye and would sometimes chip off the resin holding them together.² So began the push to develop composite resins with smaller particle sizes. 

After the macrofills came the microfills with particle sizes that were smaller than 100 nanometers (nm). However, these composites introduced a new challenge. Microfills polished well and looked beautiful but were not strong enough to hold up to the bite forces in the posterior.³

Hybrids came next, which used a mixture of filler sizes to take advantage of macrofills’ strength and microfills’ esthetics. This mixture proved beneficial, and, as a result, many of the composites used today are a form of hybrid.⁴

However, the filler sizes today have decreased further on the nanoscale, with particles smaller than 20nm. Most composites today are nanocomposites. The most significant benefit of working with filler sizes measured on the nanoscale is that they capitalize on the principles of nanotechnology and its quantum effects. 

The filler size of nanocomposites mimics the physical, chemical, mechanical, and optical properties that occur in nature.⁵ Their size means they can have different properties than if they were larger. The tiny fillers work together to create larger groups of materials, allowing the group to have different properties then they would as individual particles. This process improves nanocomposites’ esthetics and mechanical properties over their larger filler-sized composite predecessors.  

Once reaching a satisfactory level of mechanical properties and esthetics, other characteristics influence what composite dentists choose. Some prefer a high radiopacity so that they can detect it on an X-ray in the future. The propensity for shrinkage is another consideration, although many materials today have stress blockers that help prevent sensitivity-causing material shrinkage of the material during polymerization. 

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Perhaps one of the most significant considerations when selecting composite is handling. 

Dental composites are technique-sensitive restorative materials, especially compared to one of their popular antecedents, amalgam. A multitude of little steps make up composite placement technique, and perfecting the details of each is crucial. With method driving much of the success for a composite restoration, many clinicians prefer to use a composite that “feels good in their hands.” 

There are three basic categories for handling properties in dental composites today, each with benefits to how they can be used for dental restorations:

• Bulk Fills: As the name implies, bulk fills require fewer layers to fill a preparation. Per the Journal of Adhesive Dentistry, their most significant distinguishing difference from the other types of dental composite is their increased depth of cure.⁶ Improvements in translucency for composite materials make it possible to cure a layer as thick as 4 mm. The translucency allows the curing light to penetrate deeper into the material. Furthermore, improvements in the bulk fill materials have also produced similar results to multi-layer composites for marginal gap widths and dentin adaptability.⁷

• Flowables: Flowables are also aptly named as their viscosity allows for increased fluidity for these dental composites. They are often packaged in a syringe with a small gauge needle to facilitate use in tight or small preparations.⁸ While the first flowable dental composites had reduced filler content to facilitate their physical properties, the flowable composites after 2010 have filler content similar to their more viscous composite counterparts. 

• Universals: These composites are not defined by their layers or their viscosity, but instead for their intended use.Universal composites are designed to be the most versatile.  

When to use the different composite types has a lot to do with the restoration you are treating. For example, you might use one type of composite for anterior restorations and a different one for posterior restorations.

Many clinicians prefer to use bulk-fills in the posterior because they have a reputation for strength and durability, which makes them an excellent match for the bite forces there. Moreover, using fewer layers means fewer chances for technique problems, like air pockets and voids. Also, clinicians put bulk fills in the back because the translucency that increases the depth of cure produces esthetics better suited to areas less likely to be seen than prominent positions in the front.

Flowable composites also have many uses in dental restorations. Their unique handling properties allow these composites to get into the small recesses of a preparation that their thicker counterparts cannot penetrate. Many clinicians use flowable to line the bases of their restorations, particularly deep preps in the posterior, because their self-leveling properties make them an optimal base. It also helps prevent voids when you pack a bulk-fill composite on top of it in a Class II restoration. Other uses for flowable composites, per the Journal of Conservative Dentistry, include occlusal caries preparations, sealants for pits and fissures, minimally invasive Class II Restorations, as well as other noncarious lesions.⁹

Universal composites have the broadest applications. Formulated for use in anterior and posterior restorations, universals aspire to produce consistent results no matter where you place them or what adhesive system you use with them. They are also designed for indirect and direct restorations meaning they can bond to dentin or be used as adhesive primers for indirect restorative materials. In other words, you are meant to use universal composites for whatever you want, wherever you want. 

There are many variables to consider when choosing which composite to use where for your restorations. In reality, however, the most influential variable is a personal preference.  Per the European Journal of Esthetic Dentistry, most clinicians are concerned with chair time and the difficulty of achieving proper esthetic results.¹⁰ Moreover, the researchers suggest that success is more in the manual skills of the clinician and mastering the techniques that will simplify placement.¹¹

“In this profession,” the authors write in the article, “success should not be measured solely by exceptional results, but rather by a good everyday standard with regard to time management and limiting long-term risk.”

References

[1] Lavigne, Courtney. “Dental Composites: Types and Recommendations.” Speareducation.com. 18 January 2017. Updated in January 2018. Web. 15 January 2020. < http://www.speareducation.com/spear-review/2017/01/dental-composites-in-2017-what-to-look-for-and-what-to-get>.

[2] Ibid.

[3] Ibid.

[4] Ibid.

[5] “What’s So Special about the Nanoscale?” nano.gov. Web. 14 December 2018. < https://www.nano.gov/nanotech-101/special>.

[6] Van Ende, Annelies & De Munck, Jan & Lise, Diogo & Meerbeek, Bart. (2017). Bulk-Fill Composites: A Review of the Current Literature. The journal of adhesive dentistry. 19. 10.3290/j.jad.a38141. From Web: https://www.researchgate.net/publication/316524305_Bulk-Fill_Composites_A_Review_of_the_Current_Literature

[7] Agarwal, Rolly Shrivastav et al. “Evaluation of cervical marginal and internal adaptation using newer bulk fill composites: An in vitro study” Journal of conservative dentistry: JCD vol. 18,1 (2015): 56-61. From web: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4313481/

[8] Baroudi, Kusai and Jean C Rodrigues. “Flowable Resin Composites: A Systematic Review and Clinical Considerations” Journal of clinical and diagnostic research : JCDR vol. 9,6 (2015): ZE18-24

[9] Shaalan, Omar Osama et al. “Clinical evaluation of flowable resin composite versus conventional resin composite in carious and noncarious lesions: Systematic review and meta-analysis” Journal of conservative dentistry : JCDvol. 20,6 (2017): 380-385

[10] Devoto, Walter & Saracinelli, Monaldo & Manauta, Jordi. (2010). Composite in everyday practice: How to choose the right material and simplify application techniques in the anterior teeth. The European journal of esthetic dentistry : official journal of the European Academy of Esthetic Dentistry. 5. 102-24.

[11] Ibid.