Dental composite is a resin-based material used by dentists to restore teeth, commonly referred to as a tooth-colored filling. This versatile material is designed to mimic the appearance of natural tooth structure, making it a preferred choice for visible restorations. Flowable composite is a specialized variation that possesses a lower viscosity, meaning it is more fluid than its traditional, putty-like counterpart. This fluidity allows the material to be injected and settle easily into the smallest spaces within a tooth preparation.
What Makes Flowable Composite Unique
The distinct physical properties of flowable composite result from modifications to its internal composition. Like all resin composites, it consists of a resin matrix and inorganic filler particles. However, the ratio is altered to achieve fluidity. Flowable composites have a reduced percentage of filler content, typically ranging from 37% to 53% by volume, compared to the 50% to 70% found in conventional restorative composites.
This lower filler load reduces internal friction, which in turn lowers its viscosity. The resulting low viscosity permits the material to flow readily and thoroughly wet the surfaces of a cavity preparation, improving adaptation. A consequence of the reduced filler content is a decrease in mechanical strength and stiffness, measured by the elastic modulus, which is typically 20% to 30% lower than traditional composites.
The lower elastic modulus makes the material more flexible, allowing it to act as a shock absorber. This flexibility is beneficial because it helps dissipate stresses caused by polymerization shrinkage, which occurs when the material hardens. It also helps buffer the forces of chewing that the tooth will undergo after the restoration is complete. Therefore, this material is reserved for areas that do not bear the full force of chewing or where flexibility is desirable.
Common Uses in Dentistry
The unique handling characteristics of flowable composite make it suitable for specific clinical applications where traditional composite would be less effective. One frequent use is as a cavity liner or base layer in deeper preparations before a denser composite is placed on top. Applying a thin layer first ensures excellent marginal adaptation at the deepest part of the cavity, where packing a traditional material is difficult.
Its ability to flow into narrow, irregular spaces makes it the material of choice for pit and fissure sealants on the chewing surfaces of back teeth. The material effectively penetrates the deep grooves and depressions, protecting them from decay. Flowable composite is also used to treat small, conservative carious lesions, particularly those classified as Class I (on the occlusal surface) or Class V (on the smooth surfaces near the gum line).
The material’s flexibility is useful for Class V restorations, which occur on the sides of the tooth near the gums, often due to erosion or abrasion. These areas are prone to bending forces during chewing. The lower elastic modulus allows the composite to flex with the tooth, which enhances the longevity of the restoration. It is also employed to repair minor chips, fractures, or marginal defects in existing restorations where a small amount of material is needed.
How Flowable Composite is Placed
The procedure for placing flowable composite is straightforward. The material is typically packaged in small syringes with fine, flexible dispensing tips that allow for direct application into the prepared tooth area. The dentist injects the material slowly, starting at the deepest part of the preparation, allowing it to self-level and eliminate air pockets as it fills the space.
Once the material is correctly positioned, it is cured using a specialized dental curing light, much like traditional composite. This light-curing process initiates a chemical reaction that sets the resin matrix and makes the material rigid. The thickness of the material layer and the intensity of the light determine the curing time.
Because the material flows smoothly and is often used in thin layers or small areas, it requires minimal contouring and finishing. The dentist may use fine burs or polishing instruments to smooth the surface and check the bite after curing is complete. This ease of application and reduced finishing time contributes to the material’s efficiency in clinical practice.