The Ultimate Bonding Experience

Douglas L. Lambert, DDS, and Paul C. Belvedere, DDS

An interview with Dr. Damon Adams, editor-in-chief of Dentistry Today, and 2 opinion leaders in restorative dentistry—Paul C. Belvedere, DDS, and Douglas L. Lambert, DDS—on the present and future state of direct composites and adhesive dentistry.

Both of you have a very unique relationship that I believe our readers would like to know about. Would you care to elaborate?
Dr. Belvedere: Our relationship goes back to when I first met Doug, as a new patient in my practice, when his family moved to Minnesota in 1970. During the next few years, discussions about post-high school plans and career choices blossomed. I remember there was a strong interest in a business curriculum so that he could follow in his father’s footsteps, but it was apparent that Doug was also intrigued by what I did as a dentist. The opening was there! So, my approach was to take him into the lab, hand him a piece of wax and an instrument, and ask him to mimic a shape. The start of a dental career was born.

With Doug as a regular patient, we continued to keep in touch and visit together periodically. I monitored his scholastic progress from afar, watching him graduate from business school and then enter dental school at the University of Minnesota. My practice was growing substantially, so bringing on a partner was about to become a necessity. I knew the principal requirements for a strong “dental marriage” were solid ethics and morals, a good home life, and the dental aptitude and skill set of the individual. All of these elements were A+ with Doug. Our “dental marriage” became a reality.

Dr. Lambert: As I reflect back over the 40-plus years that we have known each other, Paul epitomizes what a true mentor and friend should be to any young person interested in a dental career. The ability to nurture a spark and then fan the flame has created a very positive environment for practicing together. His guidance set the tone for us and continued when it was time to expand with another partner, Dr. Sandra Houck, in our practice in 1993, and most recently with my daughter, Dr. Elizabeth Lambert. Paul is an amazing innovator and educator who has always worked constantly to improve techniques, materials, and systems for the good of dentistry. I think of him as the “MacGyver of dentistry” because of all the contributions he has made, and the many innovative products he has developed for the profession.

You are both highly regarded in the field of resin-based dentistry. Direct composites have changed in a multitude of ways during your careers. How has that impacted your practice?
Dr. Belvedere: My first work with tooth-colored restoratives began with an acrylic product from DeTrey, developed in 1949, called Sevriton Cavity Seal. That led to an opportunity to work with a new dental products division of 3M as they pursued the development of a material based on Bowen’s Resin and a glass powder filler. I placed my first composites in patients in 1964, sparking my desire to restore teeth to their natural shade with this “resin-based composite.” In the mid-1970s, I began using the Nuva Ultraviolet Light for pit and fissure sealants, which naturally led to using the Nuva Fil restorative as an adjunct to achieving more aesthetic results for my patients. Visible light curing began to evolve, and by the early ‘80s, both materials and techniques were expanding. An invitation from Ivoclar Vivadent to become a consultant presented a chance for me to expand my knowledge base of resins and the forerunners of the current bonding agents. The physical properties and handling characteristics of the composite resin materials, used mostly for anterior aesthetic restorations in the beginning stages, gradually improved throughout time. However, these materials required development of new placement and handling techniques, especially for posterior applications, so we began creating matrices and protocols to overcome some of the hurdles that we encountered. Composites were not amalgam, so use of the same matrix bands, instruments, and thought processes to complete a restoration were unacceptable. There had to be a better way!

Figure 4. The importance of the proper matrix can be appreciated with the Margin Perfect Matrix positioned on the lateral incisor to achieve complete isolation during the bonding process. A pink tint (Pink Opaquer [Pulpdent]) was applied after the dentin adhesive to neutralize effects of the dark shade from the endodontically treated tooth No. 7 prior to placing the body and enamel shaded composites.

Dr. Lambert: It’s truly amazing to me to see the progress that we have made in composite resins during my 30 years in practice. Thanks to the due diligence of the manufacturers and their research teams, we have really reached a pinnacle for direct resins. Composites have become a mainstay in all of our offices, since they offer a patient the most simple and cost-effective way to achieve an aesthetic change in the mouth. They have reached widespread use within the dental community, but certainly not without a experiencing a learning curve along the way. Composites have been met with doubt and skepticism throughout the years as a result of a long list of shortcomings such as poor wear resistance, microleakage, bodily fracture, marginal breakdown, recurrent decay, postoperative sensitivity, inadequate interproximal contacts and contours, color degradation, and inability to polish or to maintain polish. Couple these physical and mechanical shortcomings with suspect placement techniques and one can readily see that the potential for success by the early adapters of composites was greatly challenged. After years of trial and error, protocols have been developed for both anterior and posterior composites that ensure predictability, reproducibility, and also efficiency in their placement.

Let’s discuss the “learning curve” concept. Dr. Belvedere, are there differences in the way you approach anterior versus posterior composite restorations? If so, what are they?
Dr. Belvedere: Let’s face it, the ideal solution to the anterior/posterior use of resin-based composites is to have one technique using one set of restorative materials universally throughout the mouth. In the beginning, I believe the manufacturers of restoratives started the differentiation with their combinations of filler particle material, particle size, and particle shape, and then told the profession where and when to use it. The desire to increase the compressive strength of a restorative that would be formulated for posterior teeth led to the use of more crush-resistant restoratives; however, they failed to maintain a polished surface and had poor aesthetic qualities. Those filler particles were also lost through function, called “plucking,” resulting in excessive wear. This led to the requirement of more tooth mimicking materials for use in the aesthetic zone. With the advent of the microfills, polishability and aesthetics were finally achieved, but the resistance to compressive forces was not great enough to use in all posterior applications.

Today, the nanohybrid materials fulfill all of the requirements for the anterior/posterior challenge of direct composite restorations. One product with one technique being used for all areas of the mouth is the ultimate goal for direct composite placement, and it is the rule for today. That’s not to say there still aren’t challenges out there in the world of composite resins. Isolation of the preparation, control of the fluid and semi-fluid resins so that the result will anatomically replicate missing tooth structure, and thorough polymerization after placement are all of great importance.

Light energy is the key to polymerization success, especially with the posterior teeth. Initially, knowing what level of energy was actually being delivered presented another challenge. Doug and I completed some early, unpublished research in 1986 on light-curing units, collaborating with a gentleman named Walter Strauss, who was working on the concept of measuring curing light output. Dentists did not know what they were using, as there was no way to measure curing light energy at that time. This led to the first prototype radiometer. Ultimately, the first commercial radiometers came onto the market thanks to the efforts of Demetron and Joshua Friedman, DDS.

Figure 8. Class II preparation isolated with the Palodent Plus matrix system (DENTSPLY Caulk). (Note the excellent adaptation of the band to the gingival seat.)	Figure 9. Completed Class II direct composite (utilizing Prime & Bond Elect [DENTSPLY Caulk], SureFil SDR Flow [DENTSPLY Caulk], and TPH Spectra HV composite [DENTSPLY Caulk]) in a bulk-fill technique.

With the advent of visible light curing, the profession struggled by continuing to use stainless steel matrix systems designed for amalgam placement. I felt there was a need for clear matrix posterior bands so that the curing energy could be directed into the most critical areas of the restorations, which are the gingival and proximal margins. Mylar film was used to make “in-house” posterior matrix bands that could be positioned using a Tofflemire retainer, the same as the amalgam techniques. Mylar was used for these matrices because it stretches when tightened around teeth, and with proper wedging, the gingival margin areas become sealed, preventing low viscosity dentin/enamel adhesives from penetrating beyond the prepared surfaces and causing one of the reasons for postoperative sensitivity. These matrices were then produced for the profession, called Contact Molar Bands (Ivoclar Vivadent).

At the same time, as I continued working with Dr. Freidman at Demetron, concentrating light guides of 4 and 8 mm were made available. Using the 4-mm light guide, and 2 curing lights (one from the buccal, one from the lingual), the curing energy could now be concentrated in the areas such as the gingival/proximal corners, to bond the resins in these critical places before shrinkage could affect the gingival marginal seal. The resulting technique is called trans-enamel-polymerization (TEP), or through-the-tooth curing.

The most positive results of TEP occur when placing Class I restorations while using 2 lights from the sides, rather than one light from the occlusal only. By having the energy reach the resins by transmission through tooth structure, the bond to that tooth structure transmitting the light energy will take place before shrinkage can damage the marginal seal; which would occur if the energy entered the composite from the occlusal position only. This paved the way for the start of the bulk placement technique.

Dr. Lambert, could you enlighten us as to your thoughts on the various options currently available for enamel and dentin adhesion?
Dr. Lambert: I believe the first thing we have to understand is that there is a distinct difference between enamel and dentin, and we have to respect that difference. Our bonds to enamel after exposure to acid etching are micromechanical, strong, and consistent. Dentin poses a different set of concerns. It can vary from patient to patient, from one tooth to another, and can change within the depth of the preparation. Dentin is also roughly composed of 12% to 13% water, and we are asking a basically hydrophobic material (resins within an adhesive) to attach or bond to it. There is also the issue of the smear layer—whether to remove it or incorporate it into the final product. That has been a debated topic for decades. However, it seems that the current consensus is to leave it on the surface and utilize chemistries to infiltrate it, with the hope of reducing the potential for the dreaded postoperative sensitivity.

Today’s bonding systems can be grouped into 3 categories: total-etch (etch and rinse), self-etch, and the newly developed universal adhesives.

The total-etch technique has been the gold standard in direct composites since Buonocore first pioneered the concept, and it involves applying a phosphoric acid of 30% to 40% concentration to the enamel and dentin for a prescribed length of time—usually 15 to 20 seconds on enamel and 10 seconds on dentin—then the etchant is rinsed off with a water spray. This method opens itself up to several variables, such as the following: over- or under-etching the tooth surfaces, inability to remove all the acid when rinsing, overdrying the dentin, or leaving too much water on the surface; all of which can be a problem possibly contributing to sensitivity for the patient after placement of the composite, especially in the posterior. This led to advances and the creation of the self-etch systems as a way to circumvent some of these issues.

The self-etch adhesive systems eliminate the separate phosphoric etch step, but still allow for the demineralization process to take place. However, because these self-etch products rely on water to initiate the demineralization, excess water remaining during the polymerization sequence has been shown in some studies to compromise bond strength, so the manufacturers may suggest rubbing or scrubbing of their self-etch adhesives, plus the use of multiple coats to ensure more predictable results. Enamel etch patterns have also come under scrutiny with the self-etch systems, especially if the enamel was not cut with a rotary instrument. The use of a phosphoric acid as a selective-etch on enamel only, which is then rinsed off prior to the application of the self-etch resin, has been suggested as a way to improve this shortcoming.

The newest entrants into the adhesive arena are the universal systems. Many are based on previously developed adhesive chemistry, and allow us to bond to a multitude of materials including composite, porcelain, and the newer high-strength polycrystalline ceramics such as lithium disilicate and zirconia. They can be used with or without a separate acid etch step to achieve a good result, offering us more flexibility when selecting an adhesive system to purchase.

The subject of bulk-fill versus layering for posterior composites has gained a lot of popularity recently. What are your views on this topic?
Dr. Belvedere: First, let’s consider the literature. There are numerous bodies of work that support the use of large increment, or bulk-filling, of direct composites; these include published studies from Verluis and his colleagues in the mid-1990s to, most recently, Campodonico et al in 2011. As I mentioned previously, our early hands-on research laid the groundwork for the basic concepts that allowed us to successfully bulk-fill composites prior the advent of many of the newly advanced materials. Today, from a clinical standpoint, the application of the bulk-filling concept requires the combination of materials, matrices, light energy and light position, to allow the practitioner to feel confident in utilizing this technique on a daily basis.

Dr. Lambert: I think the fact that many manufacturers have recently introduced numerous products into the marketplace, that are specifically designed to be used in a bulk-fill manner—such as low shrink/low stress flowables and materials that will cure 4 to 6 mm in depth—speaks volumes for the concept of placing posterior composites in large increments. Couple that with the use of the fantastic “ring” matrix systems for isolating our Class II restorations, and it creates a very efficient and practical modality for obtaining a predictable result. For the anteriors and Class Vs, the Margin Perfect Matrix (marginperfectmatrix.com) is the most efficient matrix system available. Both advancements support what we have been doing successfully for more than 20 years based on research, common sense, and some of our own gut feelings. Posterior composites are fun to do and should not be a daunting task!

Your combined clinical experience is nearly 90 years. How have you translated that into your practice techniques and the success you achieve with composites?
Dr. Lambert: It is said that “you begin at the beginning,” and nothing could be truer as it relates to direct resins. Taking the time to research the materials that you are using, and understanding the strengths and weaknesses of each component will go a long way to achieving the desired outcome. Combine that with solid resources such as the appropriate matrix for proper isolation, the application of the enamel/dentin adhesive chemistry, and the ability to create a mold into which to inject your composites will yield more predictable results. Couple that with the selection of an LED light source with sufficient energy to cure the composite, whether you chose to layer or not, and refining your finishing and polishing techniques to minimize the time needed to complete these tasks. Efficiency is the key, since the only thing we have to sell is our time; if we can achieve an excellent result in fewer steps and in less time, we can take care of more patients.

Dr. Belvedere: Proper understanding of the manipulation of our composite materials, the longevity of our contemporary composites, and the ability to reinforce them with structural fibers gives us the opportunity to expand their uses, such as creating fiber-reinforced posts and direct composite fiber-reinforced bonded tooth replacements. The ability to replace congenitally missing lateral incisors in adolescents, or even lost teeth in geriatric patients, offers creative solutions to these aesthetic and functional challenges. Our long-term clinical success of 15 to 20 years for many of these bridges demonstrates the requirement of sharing these techniques with our colleagues. The advancement in the science of resin-based composite has been a savior in the search for metal-free restoration of human dentition.

What do you see possibly arriving in the future for resin-based dentistry?
Dr. Lambert: With the worldwide push to discontinue the use of amalgam due to environmental concerns, the search for alternative materials that can totally replace the “silver filling” continues. Even with all of the advances, composite resins and glass ionomers meet some of the criteria for the profession, but, as of yet, not all.

Dr. Belvedere: The World Health Organization, along with other international governing bodies, developed a model for an acceptable alternative based on ease of use, longevity, and cost. They coined the term biologic biomaterial and described it as “a restorative solution that would seal the interface between tooth and restoration, be adhesive, have little or no shrinkage, interact favorably with carious dentin and enamel, be easy to use in a variety of settings, fracture and wear resistant, repairable, aesthetic, cost-effective; all with zero toxicity.” Now that would be a great gift for all of dentistry, but it would likely require a major breakthrough in material science. Until then, our hopes and faith will lie with the manufacturers and research chemists to develop a tooth substitute material (resin-based or not) that does not rely on a bonding agent or involve multiple steps wrought with potential operator error, and would offer the same or better physical properties than we currently have available.

Dr. Adams: I want to thank you both for taking your time to share your clinical expertise, insight, and candid opinions with us on the topic of direct resin composites. I am sure that your leadership by example, in sharing your experiences that have been led by a model that included years of mentoring, personal and professional friendship, and a love for our noble profession, will be a beacon of inspiration for others who might have similar practice opportunities. Based on your volume of work together and dedication to the profession, this has truly been the ultimate bonding experience! Congratulations on an amazing career experience, together!

Dr. Belvedere graduated from Loyola Dental School, Chicago, in 1955, but began teaching as a student instructor in 1954. He has been teaching continuing education to practicing dentists for more than 30 years. He maintained an active general and cosmetic practice in Edina, Minn, until 2010. He is an adjunct professor and helped create and is co-director of the postgraduate program in aesthetics and contemporary dentistry at the University of Minnesota School of Dentistry. He is also an associate professor at State University of New York at Buffalo, NY. He is on 3 editorial teams and has published 32 papers, 2 chapters in aesthetically oriented books, and teaches through a multimedia presentation. He has presented more than 700 lectures as the featured lecturer to state dental societies, study groups, and dental schools internationally. He can be reached via email at velvytooth@aol.com.

Disclosure: Dr. Belvedere is the inventor and producer of the Margin Perfect Matrix.

Dr. Lambert graduated from the University of Minnesota Carlson School of Management in 1980 and the University of Minnesota School of Dentistry in 1984, where he received the Outstanding Senior Student Award and the Quintessence Award. He is a Fellow in the American College of Dentists, the Pierre Fauchard Academy, the Academy for Sports Dentistry, and the American Society for Dental Aesthetics, and is a Diplomate of the American Board of Aesthetic Dentistry. He has held many societal positions in organized dentistry, including past president of the Minneapolis District Dental Society, 6 years as a trustee to the Minnesota Dental Association, and a delegate to the ADA. Dr. Lambert is senior partner in an aesthetic-based practice in Edina, Minn. He also serves as an independent consultant and clinical researcher for many dental manufacturers and is the team dentist for the Minnesota Lynx of the Women’s National Basketball Association. He is part of the educational team for the postgraduate course in aesthetic and comprehensive dentistry at the University of Minnesota School of Dentistry and is a member of Catapult Elite. He has authored and co-authored several articles and has presented lectures and hands-on seminars internationally. He has been recognized as one of the Leaders in Continuing Education by Dentistry Today for 13 consecutive years, and has been honored as a top dentist by Minneapolis/St. Paul and Minnesota Monthly magazines for the past 12 years. He can be reached at (952) 922-9119 or via email at ddssmile@aol.com.

Disclosure: Dr. Lambert is a shareholder of Margin Perfect Matrix.