To ensure complete cure and to minimize problems associated with polymerization shrinkage, composite resins, used for direct restorations, have traditionally been placed and cured incrementally, one layer at a time, with none exceeding 2 mm.1 But, especially in deep cavities, this process can be time consuming and fraught with multiple opportunities for operator error.2
Bulk-fill materials were developed to address some of the problems inherent in composite placement. Typically more translucent, and containing more photoinitiators than conventional composites, they allow deeper cures. The addition of certain kinds of chemicals and fillers helps combat shrinkage.1
Although the jury still appears to be out on whether these materials are better at mitigating the effects of polymerization shrinkage than their nonbulk-fill counterparts,1,3–5 there is little question about the ability of bulk-fill materials to save time in the operatory. And by eliminating steps during placement, they also minimize operator error.
Packable or Flowable Composites
Bulk-fills are typically defined as any composite material that can be placed in layers greater than 2 mm. True bulk fills today are considered to be materials that can be placed and cured in a single layer up to 5 mm with minimal shrinkage. They must also offer at least a 4 mm depth of cure, adapt well to internal tooth anatomy, and be self-leveling to eliminate the need for manipulation, which could cause air bubbles.2
While packable bulk-fills are available, many of the products sold as bulk-fill composites are flowables, likely due to their ability to adapt to anatomy. But where conventional flowables are often used primarily as bases and liners, bulk-fill flowables may be used in 4 mm increments. It has typically been recommended, however, that they be capped with a higher viscosity material for esthetics and to better withstand occlusal forces.2
Innovations in this product category are never known to lag. Among the relative newcomers is a bioactive bulk-fill material that can be used to replace dentin, preserving pulp vitality, promoting pulp healing, and helping to remineralize dentin.
Another entry is a single-step, bulk-fill composite system that is delivered via sonic handpiece. The sonic waves liquefy the material, allowing it to take on flowable characteristics, resulting in excellent adaptation. Once the handpiece is deactivated, the material resumes its high-viscosity, sculptable characteristics.
Perhaps the newest development is a bulk-fill flowable that features spherical fillers, said to enhance physical properties and esthetics. Beginning as a translucent material placed and cured up to 4 mm, it becomes more opaque and toothlike upon curing. And because of the supra-nano-size filler content, which can withstand occlusal forces and polish to a high luster, it doesn’t require capping.
Isolation Improves Outcomes
To cure properly, most composites require a dry field during placement. This means that a good isolation system can make or break your restoration. The Isolite 3, Isodry, or Isovac, not only isolate the field of operation, but offer hands-free suction and soft-tissue retraction, courtesy of a flexible, transparent mouthpiece, which also prevents flying debris from being aspirated during cavity prep. In the case of the Isolite 3, shadowless illumination is ensured via either bright white light or a cure-safe amber light.
Composite resin materials, applied under the right conditions, are proven game changers in dentistry. It will be exciting to see how they’ll impact restorative dentistry as they continue to evolve.
- Lowe RA. Clinical update on composite restoratives. Decisions in Dentistry. 2017;3(7):37–42.
- Stone R. The incredible bulk. Mentor. 2012;3(4):18–23.
- Kamalak H, Kamalak A. Evaluation of polymerization shrinkage of dental composites by micro-computed tomography. Biomed Res. 2018;29:844–852.
- Yu P, Yap A, Wang XY. Degree of conversion and polymerization shrinkage of bulk-fill resin-based composites. Oper Dent. 2017;42:82–89.
- Gupta R, Tomer AK, Kumari A, Perle N, Chauhan P, Rana S. Bulkfill flowable composite resins — a review. Int J Appl Dent Sci. 2017;3:38–40.