Next-Generation Flowable Composites

 Next-Generation Flowable Composites

INTRODUCTION

The early 1990s was the time the use of composite materials in dentistry began to take shape. The initial composites were tooth-colored restoratives composed of organic resin matrices ,

and inorganic fillers consisting mainly of quartz in rather large particle sizes, making restorations rough and difficult to polish. 

Although the aesthetics were a significant advantage over its predecessors, this new material’s polishability was a great concern; thus, a variety of newer materials have emerged in response to the ever-growing needs expressed by dental practitioners. Composite resins derive their physical properties/handling characteristics from their reinforcing filler particles and their viscosities from their resin matricies.  Recently, composite categories have evolved based on resin type and filler size and now include universal composites, microfills, and bulk-fill (flowable and packable) and flowable composites. 

Increasing the filler load in a composite material improves its overall physical properties as well as resistance to the functional wear placed on the restorative material. The material’s viscosity is directly affected, as the increase in filler loading will result in a higher viscosity material, while less filler material will result in a low-viscosity-based material. In many clinical situations, there is a need to have a less viscous composite resin instead of a putty-like consistency in order for it to better adapt to the cavity walls. This led to the advent of new flowable composite resins that were introduced in late 1996.

Flowable composite with it's ease of application makes it more preferable to be used by dentists .

In their early configurations, flowable, resin-based composites were conventional composites with filler loads ranging from 37% to 53% (volume); compare that to the range of 60% to 72% (volume) for most of today’s conventional hybrid materials. By altering the percentage of filler, the viscosity of the material becomes modified. This allows manufacturers to package their materials in small syringes with small-gauge needles, allowing for easy dispensing, especially into smaller preparations, which would otherwise be challenging to fill without voids.

Fast-forward to the year 2020, and you will see that flowable composites have evolved into much more of a widely based restorative option than ever before. The challenges flowable composites faced were in the areas of strength and fracture toughness, wear-resistance, and polymerization shrinkage as well as in modulus of elasticity. Manufacturers’ technological advancements have seen increased percentages of filler materials now in the range of 70% to 80% by volume.

 The ability of manufacturers to insert submicron particles and join them into nanoclusters has dramatically changed the physical properties of flowables. The changes can be seen in the literature supporting their overall increase in flexural strength as well as compressive strength.The concern of polymerization shrinkage is still certainly in the mindset of many practitioners, and rightfully so, as flowables still have greater shrinkage than conventional composites.8 With the argument still clear, one must turn to how to best handle the flowable composite in relation to polymerization shrinkage. In regard to the placement of flowable composite, one must look at 2 very important factors related to cavity configuration and depth of material. Cavity design is dictated by the phenomenon we all call the C-factor. What we have come to learn about this, in relation to flowables, is that a horizontal placement, rather than the traditional layering protocol of incremental layering, helps to decrease the C-factor and thus decreases the shrinkage stress. Secondly, by placing the layers of flowable in no more than 1-mm increments, you will receive the most favorable outcome in regard to the shortcomings of flowable composites.10 The improved filler component has also improved the aesthetic and optical qualities of flowables by allowing the passage of light through the materials, much like that of natural tooth structure, to create a restoration that merges effortlessly with the surrounding natural dentition. The smaller particle size also leads to a much faster and easier polishing due to the lack of “plucking” that one would experience with more dated materials containing large-particle-size fillers. Utilizing various shades of flowable layered over each other for subtle color combinations gives practitioners unparalleled freedom in developing natural-looking restorations. The following case will highlight the use of a flowable composite to restore an undetectable Class V lesion on a mandibular canine. 

Flowable composite as fissure sealing material :

the use of flowable composite as a fissure sealing material can slightly increase the retention rate of sealants compared with conventional resin-based sealants.