What’s Trending in Resin-Based Restorations

Resin-based composites are widely used for direct restorations in anterior and posterior teeth due to their esthetic and versatile properties. Besides direct filling materials, they are also offered as prefabricated blocks for chairside and laboratory CAD/CAM indirect partial- and full-coverage restorations.¹

Restorative resin-based composites consist of a matrix, typically a polymerizable resin, and filler particles, enhancing their mechanical strength. Advancements in resin composite technology aim to improve wear resistance, mechanical properties, color match, and overall longevity. Nanofillers and nanotechnology have been introduced over the years to enhance the material's performance and optical characteristics.² Ideal color match of composites with surrounding tooth structures has always been a challenge, despite the availability of various shades as well as stains and modifiers, which can be layered to achieve custom shades and tooth-like appearance. To simplify clinical procedures through the application of composites in bulk instead of layers while still enabling acceptable esthetic results, new compositions and fillers are geared toward optimizing the so-called "chameleon effect," which facilitates improved color match and optical blending with the tooth, some even with only one "universal" shade.³ Other efforts are ongoing to optimize the polymerization process, addressing concerns such as shrinkage and stresses during curing, which are some of the key factors for clinical failures. Bulk-fill composites attempt to accomplish all the above with improved esthetics, an easy-to-use packable consistency, and superior physical properties, especially for posterior teeth. Nevertheless, some challenges, such as polymerization shrinkage, wear resistance, bulk/marginal fracture, secondary caries, and possible health risks remain challenges and continue to be targets of new research and developments.^1,4

Low-shrinkage composites and titanium dioxide nanoparticles to reinforce flowable composites were introduced to improve physical properties and clinical behavior.⁵ Current innovations include the development of smart materials that can be altered by various stimuli such as stress, temperature, pH, and moisture.⁵ There is also a focus on materials that have antimicrobial properties and release ions for stimulating remineralization of dental tissues.⁶ These materials help suppress caries, reduce bacterial acid production, replace lost tooth minerals, and self-heal cracks to increase restoration longevity.⁷ Antibacterial monomers have the ability to eradicate oral pathogenic microflora, not only preventing secondary caries but also supporting overall intraoral and, consequently, general health. An important new direction is the development of eco-friendly "green" composites based on natural resources, which are abundantly available, biodegradable, and cheaper than synthetic composites.⁸

The history of light curing in dentistry dates back to the 1970s, when light curing, as a polymerization method for dental materials, was introduced. Initially, quartz-tungsten-halogen (QTH) curing lights were the standard for clinical use, providing dependability and satisfactory performance.⁹ The evolution of light-curing protocols has been following technological improvements of light-curing devices, involving increasing radiant exitance and narrowing the emission spectrum to the useful wavelength range. Light-emitting diode (LED) technology has become the standard for dental curing lights. LED lights offer advantages such as a longer lifespan, lower heat generation, and a broader spectrum of light that closely matches the absorption spectrum of camphorquinone, a common photoinitiator in resin-based composites. They also offer battery-powered, silent operation, following a trend toward cordless and portable curing lights that provide practitioners flexibility and mobility.

Several advanced curing lights come equipped with features for monitoring the polymerization process in real-time. This helps ensure that dental materials receive adequate light exposure for proper conversion. Some curing lights now offer multiple wavelength options to optimize the curing process for each specific dental material. Among the goals of new developments has always been the reduction of polymerization shrinkage and stresses of resin-based composites.¹⁰ For instance, there have been recommendations to increase the curing time, even for curing lights that deliver more than 1,000 mW/cm².¹¹ Different curing light/irradiation time combinations and distance from the light guide significantly affect the hardness of resin composites.¹² The use of high power intensity over a short period of time has been shown to decrease cytotoxicity, highlighting the potential impact of light-curing methods on the biocompatibility of resin-based composites.¹³ Integration with digital technologies and smart features, such as connectivity to dental software and electronic health records, has become a trend in modern curing lights.

The use of matrix bands in restorative dentistry has evolved significantly over the years as they are essential for direct dental restorations, particularly in the placement of Class II and Class III restorations, providing tight proximal contact, better interproximal contour, and contact areas.

Sectional matrices have become quite popular, and various options are available based on their contour, hardness, stiffness, and translucency. The first sectional matrices exhibited simple shapes, while updated matrices feature more intricate designs, including a prominent curve at the marginal ridge area, a distinct bend at the interproximal-lingual and interproximal-buccal line angles, and the option to be used for subgingival cavities.

The performance of matrix bands in achieving tight proximal contacts in Class II resin composite restorations has been investigated, confirming their significance in achieving the desired clinical outcomes.¹⁴ The performance of transparent bands was comparable to that of metal bands. A randomized controlled clinical trial compared two different matrix band systems in restoring two surface cavities in posterior teeth and found that the sectional matrix band system was superior to the circumferential matrix band system.¹⁵ A cross-sectional survey to evaluate matrix band systems for posterior proximal restorations among Egyptian dentists also revealed a statistically significant difference between sectional matrix systems and circumferential matrix systems regarding the tightness of the proximal contact points.¹⁶ It emphasized the importance of selecting appropriate matrix band systems for optimal clinical outcomes. Sectional matrix bands and elastic rings are helpful in obtaining tight proximal contact and achieve better contour and anatomy with less excess.¹⁷ A contoured sectional metal matrix band with a separation clamp provides the tightest interproximal contact between Class II direct resin-based composite restorations.¹⁸ It is key to understand that an ideal interdental anatomy of Class II direct restorations is critical for maximizing arch continuity, minimizing food impaction, and maintaining dental and periodontal integrity.

Jose M. Ayub, DDS
Visiting Scholar, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Markus B. Blatz, DMD, PhD
Professor of Restorative Dentistry, Chair, Department of Preventive and Restorative Sciences, and Assistant Dean, Digital Innovation and Professional Development, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania