What You Can’t See Can Hurt You! Ensuring Success Via Full Polymerization of Composites

Dr. Douglas L. Lambert
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We place both anterior and posterior direct composite restorations in our practices every day. And yet, their use is not always as simplistic as it might seem, and their implementation requires a meticulous technique for success. Composite fillings have been described as the “bread and butter” of procedures for general dentists, with the number of restorations exceeding 122 million per year.1 However, their utilization can become very frustrating when postoperative problems arise, especially after the placement of a Class I or Class II composite.

It has been nearly 50 years since direct posterior composite resins were first introduced as an alternative to metallic restorations, most specifically amalgams. During that time, they have been met with doubt and skepticism, which was borne out by myriad shortcomings, such as poor wear resistance, micro-leakage, marginal breakdown, bodily fracture, post-op sensitivity, recurrent decay, inadequate interproximal contacts and contours, color degradation, and an inability to polish or maintain polish. Although the profession has managed to conquer many of the shortcomings, some of these issues remain a challenge to us in placing posterior composites.

Having a High Success Rate is Vital for Practice Growth
Reputation could be considered a currency in dentistry. It’s so easy to search for reviews of almost any product or service today. Our practices are no exception. Increasing the success rate of your posterior composites equates to reducing the likelihood of getting a call from a recently treated patient with some level of post-op sensitivity or a negative review being posted on social media. Factor in the loss of revenue and opportunity cost for in-office adjustments or perhaps having to remove and replace the new restoration, and it becomes paramount for us to consider a clinical pathway to successful patient outcomes. The success of a light-cured composite restoration can be dependent on several things: the preoperative condition and preparation of the tooth itself, isolation of the bonding site, adhesive dentistry and material selection, the use of bases and liners, placement techniques, light-curing technology, and finishing and polishing methods. By considering 6 simple steps—a “checklist manifesto”—for our direct posterior resins, we can eliminate many of these pitfalls and challenges (Table 1).

Many Improvements Have Been Made in Composite Materials
Thanks to the due diligence of our dental manufacturers, numerous advancements have occurred over the past several years in the resin materials themselves, enamel and dentin bonding agents, curing-light capabilities, and the placement and finishing of these composites, which have all led to improved patient outcomes. The traditional 2.0-mm layering technique is still the mode of choice for many in the profession. This technique has been used historically for 2 major reasons: (1) materials have had limited curing depth, preventing more extensive polymerization of larger increments; and (2) using smaller layers in an effort to control shrinkage and stress issues due to polymerization reactions. Thanks to enhanced technology on many levels, however, larger-increment or bulk-fill materials are gaining popularity because they allow clinicians to reduce the number of steps and the time required to place the resin. Many are formulated to reduce polymerization shrinkage stress and strain during light activation. Their composition varies among manufacturers and are BIS-GMA or urethane methacrylate-based derivatives, newer resin-based chemistries with additional entrants into the market under the monikers of bioactive, giomer, or ormocer technologies. These bulk-fill (one-increment) and semi-bulk fill (2-increment) composites may be categorized by their viscosities: flowable and denser body or paste forms (Table 2). Their use offers the practitioner numerous options for restoring Class I and Class II preparations. The vast majority allow for curing depths in the 4- to 5-mm range with varying curing times and energy requirements. Flowable bulk-fill materials may or may not require a top layer (Figures 1 and 2). Paste forms can create efficiencies in placement with the ability to fill a moderate depth prep in one application (Figures 3 and 4). Some are enhanced with ultrasonic energy. Even the traditional approach of the 2.0-mm increment has had an upgrade with the advent of new shade-matching chemistry (Figures 5 and 6).

The Importance of Curing Lights
Advances in the materials themselves are only one part of the equation, however. Perhaps the most underappreciated aspect of our entire composite protocol is the key role our curing lights play in obtaining the desired results. It is one of the 6 key steps to a successful composite technique. Nearly a decade ago, Price2 introduced the 4 C.O.R.E. principles, which outlined basic parameters for us to evaluate and follow in our light-curing regimen. They focus on the properties of the curing light itself (output, beam profile, and beam collimation), operator technique (placement and orientation of the light tip), restoration characteristics (location, size, and depth of the prep), and energy requirements (material selection and spectral emission to match photo initiators). The consequences of improper light curing are daunting. Insufficient polymerization adversely affects both the physical and chemical properties of the restoration. This includes potential inflammatory responses from the pulp, lower bond strengths, more water sorption, weaker physical properties, microleakage, sensitivity, and recurrent decay, all of which affect the clinical success of our composite restorations and patient outcomes.

Many of these C.O.R.E. principles can be applied to our daily practices just by paying a little more attention to detail. One such details is the care taken in placement and orientation of the light guide to allow for the energy emitted from the tip to properly and adequately initiate the photoreaction. One new LED light even has a vibrating system that alerts the user when they stray from the proper position. Some lights lose significant intensity over distance, making them less effective at delivering energy at clinically relevant distances.3 Another detail is keeping the light guide free of debris and residual resin or covering the light guide with a disposable barrier that does not reduce the light energy for polymerization. LED lights may produce heat during use that can contribute to patient post-op sensitivity related to the soft tissue or the pulp. Simple heat management techniques, such as breaking up longer curing times to allow heat to dissipate or applying a cool stream of air that will keep temperatures from reaching levels where tissue might be at risk of damage, are easy to do.

Is Your Curing Light Functioning Properly?
Yet, one of the more challenging aspects of light curing composites is the question of how well the curing light we use functions with the light-curable materials we employ daily in our own offices. The particular material you are exposing to the light source will play a role in the energy needed to polymerize and the length of exposure time. LEDs have become the leading technology for our light-curing necessities. Halogen and some of the first LED lights produced outputs ranging from 300 to 500 mW/cm2, but curing lights today can emit outputs between 1,000 and 5,000 mW/cm2. Composites can vary significantly in the amount of curing energy required to polymerize them. This can occur between manufacturers or within the same product line or in light vs dark shades, flowables vs body composites, and so forth. Every composite has its own energy requirement to reach its full potential. This data is available for all resins and bonding agents from the manufacturer but is cumbersome to correlate ourselves. Even the instructions from the companies for use of materials and curing lights can be difficult to decipher, unclear, or insufficient. The correlation of adequate light curing with the material selection is critical to ensure that you are maximizing the benefits for the best clinical performance.

One new technology to hit the market is checkUP (BlueLight Analytics). It is a platform that helps deliver great curing results every time. It utilizes a light meter that connects via Bluetooth to any mobile device running iOS or Android and contains a database of lights and light-cured materials. Based on the unique output from each light in the office, the software provides a set of curing times for each material by shade and increment as derived from the instructions for use. The management software can be easily implemented as part of the office’s regular preparation protocols, replacing the need to manage all those instructions somewhere and avoiding wasting time looking for them when they are needed. According to BlueLight Analytics, data collected from tens of thousands of light curing units used in practice have shown one in 4 to be out of manufacturer specification (ISO 10650-2018) (Figure 7). Therefore, relying solely on the manufacturer’s stated output is a risk. When coupled with the ability to troubleshoot the pairing of a composite with your curing light, it becomes a quantifiable relationship. The software will not only correlate the energy output of the light tested with guidelines for maximal curing depth for a particular exposure time but can also alert you to the length of continuous curing time when heat buildup may be an issue. It stores this data and updates it for us as we test our lights on a periodic basis and continually add new materials to our armamentaria. This knowledge enhances our confidence to know that the LED lights we use with our materials are performing at their peak levels for our patients (Figure 8).

CLOSING COMMENTS
Dental composites have become a mainstay in our practices and a ubiquitous part of our clinical routines. The use of composite resins throughout the patient’s dentition have made them a universal restorative for many. Challenges still abound for the clinician, especially in Class I and Class II applications. Advances in the resin chemistry of the materials have afforded the profession numerous options for placement by utilizing larger increments in bulk- and semi-bulk fill techniques. Understanding the relationship between these contemporary materials and today’s LED light sources is a logical and predictable way to improve our composite protocol and to ensure that we are delivering the best and most successful dentistry possible for our patients.


References

  1. National Institutes of Health. NIH funds six grants to build next generation dental composite [press release]. September 5, 2013. https://www.nih.gov/news-events/news-releases/nih-funds-six-grants-build-next-generation-dental-composite. Accessed January 7, 2020.
  2. Price RB. Light energy matters. J Can Dent Assoc. 2010;76:a63.
  3. Catelan A, de Araújo LS, de Silveira BC, et al. Impact of the distance of light curing on the degree of conversion and microhardness of a composite resin. Acta Odontol Scand. 2015;73:298-301.

Dr. Lambert graduated from the University of Minnesota Carlson School of Management and the University of Minnesota School of Dentistry where he received the Outstanding Senior Student Award and the Quintessence Award. He is a Fellow in the American College of Dentists, the International College of Dentists, the Pierre Fauchard Academy, the Academy for Sports Dentistry, and the American Society for Dental Aesthetics. He is a Diplomate of the American Board of Aesthetic Dentistry. He has been recognized as one of the Leaders in CE by Dentistry Today for 16 consecutive years and was honored as a Top Dentist by Minneapolis/St. Paul and Minnesota Monthly magazines for the past 15 years. Dr. Lambert is a past president of the Minneapolis District Dental Society, was Trustee to the Minnesota Dental Association for 6 years, and has been a delegate to the ADA. He has authored numerous articles, presented lectures and hands-on seminars nationally and internationally, and is part of the education team for the post-graduate course in Comprehensive, Esthetic and Implant Dentistry at the University of Minnesota School of Dentistry and the Catapult Group. He serves as an independent researcher for many dental manufacturers and as the team dentist for the Minnesota Lynx of the WNBA. Dr. Lambert’s practice in Edina, Minn, emphasizes cosmetic, comprehensive, and sports dentistry. He can be reached via email at ddssmile@aol.com.

 

Disclosure: Dr. Lambert reports no disclosures.

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