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Future Innovation and Research in Dental Restorative Materials E.D. Rekow, C.H. Fox, T. Watson and P.E. Petersen ADR 2013 25: 2 DOI: 10.1177/0022034513502205 The online version of this article can be found at: http://adr.sagepub.com/content/25/1/2
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Future Innovation and Research in Dental Restorative Materials E.D. Rekow1*, C.H. Fox2, T. Watson3, and P.E. Petersen4 1
King’s College London Dental Institute, Central Office, Guy’s Tower, Guy’s Hospital, London SE1 9RT, UK; 2International Association for Dental Research, 1619 Duke Street, Alexandria, VA 22314, USA; 3King’s College London Dental Institute, Department of Biomaterials, Biomimetics, and Biophotonics, Guy’s Tower, Guy’s Hospital, London SE1 9RT, UK; and 4World Health Organization, Oral Health Programme, Chronic Disease and Health Promotion, 20 Ave Appia, Geneva, CH-1211, Switzerland; and 4School of Dentistry, Dept. for Community Dentistry and Graduate Studies, Centre for Health and Society, Oester Farimagsgade 5, Copenhagen, DK-1014, Denmark; *corresponding author, dianne [email protected] Adv Dent Res 25(1):2-7, 2013
This is information presented at the IADR Dental Materials Innovation Workshop, December 10-12, 2012, King’s College London, UK. Sponsored by the International Association for Dental Research, FDI World Dental Federation, World Health Organization, United Nations Environmental Programme, and King’s College London Dental Institute.
INTRODUCTION
A
n unfortunate reality is that, despite being preventable, dental caries remains a ubiquitous disease globally. Worldwide, nearly 100% of the population in the majority of countries are affected (WHO, 2003; Petersen et al., 2005). Consequently, the need for restoration remains great. Many dental restorative materials exist, but there are challenges from numerous sources about the future and long-term viability of these materials. Among these are the United Nations Environmental Programme’s (UNEP) concern with controlling the use of mercury in products, including dental amalgam (Petersen, 2009), potentially endangering the future of amalgam, despite its world-wide acceptance as an excellent restorative material. Some restorative materials are not available in developing countries, a situation further exacerbated by the difficulties in successful use of the materials when electricity is not available, creating challenges in the use of light-cured materials and refrigerated storage demands. Concern with clinical performance of other materials prompted the US National Institutes of Health to request proposals supporting the design and development of novel dental composite restorative systems that demonstrate significant
DOI: 10.1177/0022034513502205 © International & American Associations for Dental Research
lifetime superiority over currently available Bis-GMA/TEGDMA-based systems (http://grants.nih.gov/grants/guide/rfa-files/ RFA-DE-13-001.html). Together, these challenges prompted the International Association for Dental Research (IADR), the World Health Organization (WHO), the United Nations Environmental Programme (UNEP), the FDI World Dental Federation (FDI), and King’s College London Dental Institute to sponsor a joint workshop in December 2012 to explore innovations in dental materials, with particular emphasis on direct restorative materials. It is recognized, however, that the availability and acceptance of new materials depend on factors far broader than their properties alone. Consequently, we engaged a dynamic group of experts to address the full scope of hurdles to design, produce, approve, and utilize any new but especially innovative materials. These experts were drawn from both dental and non-dental academic institutions, and industry, along with those from policy, research funding, and professional organizations. The presentations were thought provoking and the discussion lively. This issue of Advances in Dental Research offers highlights and summaries of the conversations in the following sessions: Session 1: The Challenge (Stephen Bayne, Moderator) •• A Global Perspective on Dental Caries Prevention and Treatment – presented by Poul Erik Peterson, WHO, Geneva, Switzerland, who tailored his remarks around the following questions: — What key aspects of restorative materials are required to effectively leverage caries prevention? — Will caries prevention ever be higher priority than treatment for dentists? Will prevention as a priority depend on payment schemes? — What is the potential impact of global high-speed communication on rapid progress in caries prevention? •• A Review of the UNEP Process to Develop a Treaty on Mercury – presented by David Piper, UNEP Deputy, Chemicals Branch, Geneva, Switzerland, who summarized the process, progress, and timetable of the complexities of reaching international agreement on mercury in the environment. •• Human Safety of Current Dental Restorative Materials – presented by Gottfried Schmalz, University of Regensburg, Germany, who tailored his remarks around the following questions:
Key Words biomedical research, dental restoration, private-public sector cooperation, dental economics, dental materials, patient advocacy.
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Adv Dent Res 25(1) 2013 Future Innovation and Research in Dental Restorative Materials 3 — What
is an acceptable risk-benefit ratio for restorative materials? — Do any current materials, used according to recommendations, pose a true biological threat to humans? — What is of greater concern from a biological standpoint, the materials as placed or their degradation by-products? •• Environmental Safety of Current Dental Restorative Materials – presented by Daniel Meyer, American Dental Association, Chicago, IL, USA, who tailored his remarks around the following questions: — What are the technical issues for using, maintaining, replacing, and recycling dental restorative materials? — What are the costs of safely managing and recycling restorative materials in a wide range of environments around the world where dental care is delivered? — Are current production methods for dental restorative materials environmentally friendly? If not, what processes can be improved, and how? — What additional challenges are introduced in resourcepoor settings? Session 2: Design Parameters/Specifications for an Ideal Dental Restorative Material (Dianne Rekow, Moderator) •• Clinical Characteristics – presented by Stephen Bayne, University of Michigan, Ann Arbor, MI, USA, who tailored his remarks around the following questions: — What are the clinical delivery and management systems that are needed for something to succeed in a wide range of environments? — What are the key properties (physical, chemical, mechanical, biological, and clinical) that a new successful restorative material should display vs. time? — Should manufacturers devote more time and effort to designing the easiest material to use, or invest more in clinical training for materials that are of highest quality but are more technique-sensitive? — What is more important for materials development: adequate performance in the hands of most professionals or optimal performance in the hands of highly skilled professionals? •• The Setting: Intra-oral and across the Globe – presented by Ricardo Carvalho, University of British Columbia, Vancouver, BC, Canada, who tailored his remarks around the following questions: — What different facilities and conditions exist in different regions of the world that preclude the delivery and use of a universal, ideal direct restorative material? — Is it an option for manufacturers to develop 2 or 3 levels of quality for their materials for different regions (i.e., lower cost and more easily delivered materials that are of acceptable, but not top of the line, quality)? — Should more effort be directed toward the development of alternative functional materials that can be produced locally at low cost? — What can be done to enhance the training of ‘less skilled’ personnel to deliver restorative dentistry in remote and difficult environments? •• Economic Considerations within the Health Care System – presented by Jimmy Steele, University of Newcastle,
Newcastle, UK, who tailored his remarks around the following questions: — What is a good model for understanding costs across different health care systems around the globe? — What is a practical way to weigh the cost/benefits of treatment vs. prevention and health? — What is a practical way to weigh the cost/benefits of repair vs. replacement of defective restorations?
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Session 3: Outside-the (cavity-Prep)-Box Thinking (Van Thompson, moderator) Adhesion and Adhesives – presented by Bamber Blackman, Imperial College, London, UK, who tailored his remarks around the following questions: — Are there testing and modeling methods used in engineering and materials science that would be of use to dental bonding? — Are there new adhesive technologies that could be applied to dentistry? — What outside environments are as hostile as the mouth, and what can we learn from them with respect to adhesive technologies? Managing the Tooth-Restoration Interface – presented by Tim Watson, King’s College London Dental Institute, London, UK, who tailored his comments around the following questions: — What is the full range of interfaces that are truly involved at the tooth-restoration zone (internal interfaces like fillerresin, restoration with bonding system, bonding system with tooth structure, damage zone on prepared tooth structure, potential interfaces with repair systems, and others)? — What are the challenges (adhesion, color sealing)? — Is there evidence that adhesion is critical for successful, durable restorations? Is the degradation of adhesives and adhesive layers really a clinical concern to be addressed for enhanced durability of dental restorations? Advances in Polymer Chemistry – presented by Jeffrey Stansbury, University of Colorado, Boulder, CO, USA, who tailored his comments around the following questions: — Can we eliminate BPA-based monomer systems in dentistry? — Is it possible to achieve high levels of reaction conversion in future products? — What is the best route to the development of polymers that are resistant to degradation by oral fluids, bacteria, enzymes, etc.? Polymeric Composites – presented by Linda Schadler, Rensselaer Polytechnic Institute, Troy, NY, US, who tailored her comments around the following questions: — What are the practical upper limits for toughness and fracture strength of polymer composites? — What are the new fabrication technologies for mesostructures? — What is the meso-structure and how would you characterize the special meso-contributions to properties? Nanomaterials – presented by Raymond Pearson, Lehigh University, Bethlehem, PA, US, who tailored his comments around the following questions:
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Are the current worries about nano-sized fillers warranted and, if so, is there a way to address these worries? — What are the 2 or 3 major property gains in working with materials with nano-structure? — What are the practical size ranges for nano-phases in nano-materials? •• Functional Dental Materials That Promote Remineralization – presented by Grayson Marshall, University of California San Francisco, San Francisco, CA, USA, who tailored his comments around the following questions: — What is the biological balance (availability of CA, PO4, F, and other ions) for effective remineralization? — Do we need to worry about ion-depletion of functional dental materials? — Are zones remineralized by functional dental materials more resistant to repeated demineralization? — What is the impact of reduced saliva flow on the potential of functional dental materials? •• Bio-inspired Complex Materials – presented by Rafael Libanori, ETH Zürich, Zürich, Switzerland, who tailored his remarks around the following questions: — What special processing methods/conditions are needed for these materials? — What are the properties of these materials? — What is the long-term functionality of these materials? — How well do these materials provide esthetics? Session 4. Incorporating New Materials and Techniques into Clinical Practice (Nigel Pitts, Moderator) •• Accelerating the Research to Regulatory Approval Process: The NIH/FDA Example – presented by James Drummond, NIH/NIDCR, Bethesda, MD, USA, who tailored his remarks around the following questions: — What should granting agencies solicit for future materials discovery and development strategies to shape their funding focus areas? — Should government granting agencies partner more closely with industry in co-funding mutually beneficial research, product testing, and evaluation? — Should government regulatory and funding agencies cosponsor symposia and workshops investigating ways to hasten the process of product approval? — How do environmental concerns factor into the development of a funding agency’s strategic planning and resource allocation? •• Intellectual Property/Patent and Regulatory Hurdles – presented by Rainer Guggenberger, 3M ESPE, Seefeld, Germany, who tailored his remarks around the following questions: — How do current regulatory processes across the globe negatively affect the development and marketing of new dental materials? — Is it possible for industry to partner with academia more closely to develop new products by establishing mutually beneficial ‘incubators’ at research-intensive schools? — What are the challenges, inconsistencies, and enforcement problems of a global patent system? •• Incorporating New Materials into Dental Education – presented by Patrick Ferrillo, International Federation of Dental
Adv Dent Res 25(1) 2013
Educators and Associations, San Francisco, CA, USA, who tailored his remarks around the following questions: — Should dental schools teach the latest materials being promoted by key opinion leaders to best prepare students for future dental practice? — Should students be required to participate in research during dental school to emphasize the importance of this process in materials development and use? — Should dental students become a ‘testing ground’ for new material types and brands to gain insight about the technique-sensitivity of new products? •• Incorporating New Materials into Current Practice—presented by Stuart Johnston, a dental practitioner representing FDI and the British Dental Association, UK, who tailored his remarks around the following questions: — What is the minimum in vitro and clinical evidence that practitioners need to make choices about using a new material? — On whom/what do practitioners most rely for information when choosing a new material? — How can this information be delivered to practitioners most efficiently and at the lowest cost?
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Session 5: Ensuring the Global Availability of High-quality Dental Restorative Materials (Jack Ferracane, moderator) Strategy with WHO, UNEP, Regional and National Regulatory Bodies – presented by Julian Fisher, FDI World Dental Federation, Geneva, Switzerland, who tailored his comments around the following questions: — Should there be a review of the effectiveness of existing dental materials that involves all interested groups and recurring on a five- or ten-year cycle? — Would it be helpful to have a research and development priority list developed and revisited on a routine basis to ensure that the world’s needs for new materials are met? An open conversation with industry representatives addressing the following questions: — What is the normal half-life for a new product? — How will competitors deliver a new product that might not be patented by any one of them? What if a new restorative material was ‘open source’? — Should manufacturers agree to purchase certain base components from single sources to ensure a uniform level of quality around the world? Role of National Dental Associations – presented by JeanLuc Eiselé, FDI World Dental Federation, Geneva, Switzerland, who tailored his comments around the following questions: — How should dental groups interact with the research base/ agencies? — How much influence should the national dental associations have? — How should the media be engaged? Research Advocacy Targeted at Government and Privateindustry Sources – presented by Christopher Fox, IADR, Alexandria, VA, USA, who tailored his comments around the following questions: — What are the politics of coordinating university, government, NGO, and corporate interests while cooperating to leverage a new strategy for patient care?
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Adv Dent Res 25(1) 2013 Future Innovation and Research in Dental Restorative Materials 5 — —
How do you ‘manage change’ in such a complex structure? How do dental materials research individuals (academics, etc.), advocate for change?
Session 6: Developing a Prioritized Agenda for Dental Materials Innovation and Research (moderated by Timothy Watson and Christopher Fox) •• This group discussion continued discussion from previous sessions, summarized challenges, and articulated research and advocacy priorities. In recent years, UNEP has expressed concern over the impact of mercury on the environment. In response to this, the WHO Global Oral Health Programme organized a Technical Consultation in Geneva in 2009 with the aim of identifying the scientific evidence on dental restorative materials, analyzing the conditions of providing dental care around the globe, and exploring the policies related to use of dental materials. WHO was the major catalyst for the workshop. Mercury-containing dental amalgam, with ever-improving formulations, has been successfully used throughout the world for over 150 years (Petersen, 2009). Amalgam has been shown to be exceptionally versatile, performing well in multiple classes of restoration, and, in the vast majority of low- and middle-income countries, is the preferred material for direct restorations. However, in the past decades, awareness and recognition of the environmental implications of mercury have increased. In 2001, the UNEP Governing Council requested a global assessment of mercury and its compounds. By 2007, UNEP formalized a Global Mercury Partnership with the objectives of: (1) minimizing and, if possible, eliminating the mercury supply; (2) minimizing and, where feasible, eliminating unintentional mercury releases to air, water, and land; (3) continuing minimization and elimination of global use and demand for mercury; and (4) promoting development of non-mercury technologies where suitable economically feasible alternatives do not exist (Reinhardt, 1988; Hilt et al., 2009). In 2009, the WHO Global Oral Health Program organized a technical meeting to assess the scientific evidence on use of dental restorative materials, including dental amalgam; the implications of using alternative restorative materials; and the quality of existing materials and the future needs for dental restorative materials. The complexity of developing new materials is often underappreciated. The patient, the restorative material, and the clinician or operator doing the restoration all contribute significantly to the clinical outcome (Fig.). Within each of these components, there are myriad factors that influence choices. Globally, only approximately 60% of the population worldwide has access to proper oral health care (Hosseinpoor et al., 2012); the density of qualified dentists varies from 1 out of 560 people in Croatia to 1 out of 1,278,446 in Ethiopia (Glick et al., 2012). Oral health varies dramatically throughout the world and even within small geographic regions. For instance, within London boroughs alone, percentages of children with dmft rates greater than zero vary from 19.9% to over 50% (http://www .nwph.net/dentalhealth/caveat.htm). Furthermore, a patient’s perceived value of dentistry in general and in saving a tooth specifically is necessarily influenced by his/her economic
condition: Without the resources to feed one’s family, health care is not likely to be a high priority. The availability of direct restorative materials and the introduction of new, especially innovative materials are surprisingly complex. Currently, 3 classes of restorative materials currently exist in addition to amalgam: resin-based composites, glassionomer cements, and resin-modified glass-ionomer. Yet none offers the same combination of ease of handling and clinical longevity as amalgam (Petersen, 2009). Alternative materials, some with extraordinary characteristics and material properties, are being explored in laboratories both within the dental community and in the wider materials science community. These include materials that promote remineralization (Gower, 2008; Banerjee et al., 2011; Bertassoni et al., 2011), improved adhesion and fracture resistance (Blackman et al., 2013), advances in polymer chemistry and composite resin systems (Moraes et al., 2011; Liu et al., 2012), and integration of the advantages of nanocomposites (Akcora et al., 2009; Dittanet and Pearson, 2013) and bioinspired complex materials (Erb et al., 2012; Libanori et al., 2012). However, existence of the material is a necessary but far from sufficient criterion to ensure its availability. Safety considerations are critical. Dental materials have been shown to have very low toxicity compared with those used in cosmetics (Orton and Wilkinson, 2004; Gawkrodger, 2005). Yet for some, there remains what might best be called the ‘emotional toxicity’ of amalgam. The introduction of any new material faces an array of regulatory hurdles. Many are similar to those of the US Food and Drug Administration, where materials similar to those already in use are more straightforward than innovative ones. Unfortunately, there is little agreement between and among countries about the amount of testing needed to prove similarity or differences, creating expensive demands on manufacturers. Not surprisingly, this can result in limited geographic distribution of products or a decision not to pursue some potentially exceptionally performing materials because they are too costly to bring to the market. The environmental impact of materials is clearly evident in the UNEP actions described above. It is important to appreciate that the environmental impact spans the material’s lifetime – from acquisition of the raw materials through removal from the patient. For amalgam, mercury, of course, is a major constituent in its production. It has also been the focus of best practices for amalgam waste, which aim to minimize mercury discharge into the environment (Fan et al., 2002). Similar birth-to-death considerations must be considered for all materials. Obviously companies make restorative materials available. It would be naïve to assume that profitability of the product is not important. It is notable, however, that a social responsibility ethos in many companies delivers materials and services in some markets and regions that are not profitable. The clinician or operator treating the patient and placing the restoration is immensely important in determining clinical outcomes. Comparison of failure rates between controlled clinical studies and practice-based studies suggests that both failure rates and restoration failure modes can differ dramatically (Bayne, 2012). Surely some of this difference results from
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Rekow et al.
Acknowledgments
Research and Advocacy • Demographics • Oral health • Tooth condion • Perceived value
Paent
• Funding • Partnerships
Restorave Material(s)
• State of the science • Innovaons • Material properes • Safety • Regulatory constraints • Environmental impact • Geographic locaon • Corporate priories
Clinician/ Operator
Adv Dent Res 25(1) 2013
• Operator skill • Paent behaviors
Clinical Outcome
• Materials available • Educaon • Health care system • Informaon resources • Paent oral health • Tooth locaon/condion
Figure. Interdependencies of factors contributing to innovation and research in dental restorative materials.
material choices and proper diagnosis. Those, in turn, are influenced by the education of the clinician/operator. There need not necessarily be a direct correlation between years of academic training study and effectiveness, however, as has been shown by at least short-term successes with restorations placed by nondentists (Bader et al., 2011; Freeman et al., 2013). It is tempting to assume that treatment decisions depend upon only the patient and the clinician. However, the health care system can profoundly influence decisions about whether, when, how, and how quickly treatment can be rendered and new materials introduced (Coulter et al., 2004). It will be further informed by the information resources upon which the clinician relies for understanding expectations about the performance of alternative materials. These can range from advertisement claims, to proclamations and recommendations by peers and spokesmen, to high-quality laboratory research (which may or may not reliably predict clinical performance), to long-term clinical studies (where the product may no longer be available). Few would argue the value of research in improving clinical outcomes. Yet, disappointingly, research funding for new dental materials has apparently not been a priority for funding agencies. Similarly, funding support to train the next generation of materials scientists with a focus on dental materials has been disappointingly low. Consequently, the emphasis of materials science research has now shifted from university- to corporate-based settings. While many excellent scientists engage in corporate research, corporate priorities and intellectual property considerations can potentially limit the wide sharing of discoveries. Undoubtedly, advocacy plays an important role in reducing barriers to progress. Advocacy for increased funding for innovation in materials and investment in future scientists is obvious. But there is also a strong need to harmonize regulatory barriers. There is a burning need to overcome the considerable obstacles preventing delivery of excellent health care throughout the world. IADR has built solid relationships with funding, policy, and professional organizations. Capitalizing on these relationships, its leaders and members are well-positioned to make a difference to materials science and oral health.
Without the support of IADR, WHO, FDI, and UNEP, we would not have been able to define the content of the workshop. The following corporations were instrumental in providing scientific expertise and unrestricted grants to IADR for support of the workshop: 3M ESPE, Dentsply De Trey GmbH, Dentsply International, DMG Dental-Materials Gesellschaft bH, GC Corporation, Ivoclar Vivadent AG, and Kerr Corporation. We thank the numerous attendees, who provided their own support to share their ideas and expertise with us. We acknowledge the efforts of Tim Watson, Steve Bayne, and Jack Ferracane in drafting the questions that formed the basis for the presentations, and we recognize the valuable notes of the discussions summarized by Mathilde “Tilly” Peters and Sally Marshall. C.H. Fox serves as the Executive Director of the International Association for Dental Research. The authors received no financial support and declare no potential conflicts of interest with respect to the authorship and/or publication of this article.
References Akcora P, Liu H, Kumar SK, Moll JL, Brenicewicz BC, Schadler LS, et al. (2009). Anisotropic self-assembly of spherical polymer-grafted nanoparticles. Nat Mater 8:354-359. Bader JD, Lee JY, Shugars DA, Burrus BB, Wetterhall S (2011). Clinical technical performance of dental therapists in Alaska. J Am Dent Assoc 142:322-326. Banerjee A, Pabari H, Paolinelis G, Thompson ID, Watson TF (2011). An in vitro evaluation of selective demineralised enamel removal using bioactive glass air abrasion. Clin Oral Investig 15:895-900. Bayne SC (2012). Correlation of clinical performance with ‘in vitro tests’ of restorative dental materials that use polymer-based matrices. Dent Mater 28:52-71. Bertassoni LE, Habelitz S, Marshall SJ, Marshall GW (2011). Mechanical recovery of dentin following remineralization in vitro – an indentation study. J Biomech 44:176-181. Blackman BRK, Kinloch AJ, Sanchez FSR, Teo WS, Williams JG (2013). The fracture behaviour of structural adhesives under high rates of testing. Eng Fract Mech 76:2868-2889. Coulter I, Yamamoto JM, Marcus M, Freed J, Der-Martirosian C, GuzmanBecerra N, et al. (2004). Self-reported oral health of enrollees in capitated and fee-for-service dental benefit plans. J Am Dent Assoc 135:1606-1615. Dittanet P, Pearson RA (2013). Effect of bimodal particle size distributions on the toughening mechanisms in silica nanoparticle filled epoxy resin. Polymer 54:1832-1845. Erb RM, Libanori R, Rothfuchs N, Studart AR (2012). Composites reinforced in three dimensions by using low magnetic fields. Science 335:199-204. Fan PL, Batchu H, Chou HN, Gasparac W, Sandrik J, Meyer DM (2002). Laboratory evaluation of amalgam separators. J Am Dent Assoc 133:577-584. Freeman R, Lush C, Macgillveray S, Themessl-Huber M, Richards D (2013). Dental therapists/hygienists working in remote-rural primary care: a structured review of effectiveness, efficiency, sustainability, acceptability and affordability. Int Dent J 63:103-112. Gawkrodger DJ (2005). Investigation of reactions to dental materials. Br J Dermatol 153:479-485. Glick M, Monteiro da Silva O, Seeberger GK, Xu T, Pucca G, Williams DM, et al. (2012). FDI Vision 2020: shaping the future of oral health. Int Dent J 62:278-291. Gower LB (2008). Biomimetic model systems for investigating the amorphous precursor and pathway and its role in biomineralization. Chem Rev 108:4551-4627.
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Adv Dent Res 25(1) 2013 Future Innovation and Research in Dental Restorative Materials 7 Hilt B, Svendsen K, Syversen T, Aas O, Qvenild T, Sletvold H, et al. (2009). Occurrence of cognitive symptoms in dental assistants with previous occupational exposure to metallic mercury. Neurotoxicology 30:1202-1206. Hosseinpoor AR, Itani L, Petersen PE (2012). Socio-economic inequality in oral healthcare coverage: results from the World Health Survey. J Dent Res 91:275-281. Libanori R, Erb RM, Reiser A, Le Ferrand H, Süess MJ, Spolenak R, et al. (2012). Stretchable heterogeneous composites with extreme mechanical gradients. Nat Commun 3:1265. Liu J, Howard GD, Lewis SH, Barros MD, Stansbury JW (2012). A study of shrinkage stress reduction and mechanical properties of nanogel-modified resin systems. Eur Polym J 48:1819-1828. Moraes RR, Garcia JW, Barros MD, Lewis SH, Pfeifer CS, Liu J, et al. (2011). Control of polymerization shrinkage and stress in nanogelmodified monomer and composite materials. Dent Mater 27:509-519.
Orton DI, Wilkinson JD (2004). Cosmetic allergy: incidence, diagnosis, and management. Am J Clin Dermatol 5:327-337. Petersen PE (2009). Future use of materials for dental restoration. Geneva: World Heath Organization. URL accessed on 6/10/2013 at: http://www. who.int/oral_health/publications/dental_material_2011.pdf. Petersen PE, Bourgeois D, Ogawa H, Estupinan-Day S, Ndiaye C (2005). The global burden of oral diseases and risks to oral health. Bull World Health Organization 83:661-669. Reinhardt JW (1988). Risk assessment of mercury exposure from dental amalgams. J Public Health Dent 48:172-177. WHO (2003). The World Oral Health Report 2003: Continuous Improvement of Oral Health in the 21st Century - the Approach of the WHO Global Oral Health Programme. Geneva: WHO. URL accessed on 6/10/2013 at: http://www.who.int/oral_health/publications/report03/en/index.html
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Future Innovation and Research in Dental Restorative Materials E.D. Rekow, C.H. Fox, T. Watson and P.E. Petersen ADR 2013 25: 2 DOI: 10.1177/0022034513502205 The online version of this article can be found at: http://adr.sagepub.com/content/25/1/2
Published by: http://www.sagepublications.com
On behalf of: International and American Associations for Dental Research
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Future Innovation and Research in Dental Restorative Materials E.D. Rekow1*, C.H. Fox2, T. Watson3, and P.E. Petersen4 1
King’s College London Dental Institute, Central Office, Guy’s Tower, Guy’s Hospital, London SE1 9RT, UK; 2International Association for Dental Research, 1619 Duke Street, Alexandria, VA 22314, USA; 3King’s College London Dental Institute, Department of Biomaterials, Biomimetics, and Biophotonics, Guy’s Tower, Guy’s Hospital, London SE1 9RT, UK; and 4World Health Organization, Oral Health Programme, Chronic Disease and Health Promotion, 20 Ave Appia, Geneva, CH-1211, Switzerland; and 4School of Dentistry, Dept. for Community Dentistry and Graduate Studies, Centre for Health and Society, Oester Farimagsgade 5, Copenhagen, DK-1014, Denmark; *corresponding author, dianne [email protected] Adv Dent Res 25(1):2-7, 2013
This is information presented at the IADR Dental Materials Innovation Workshop, December 10-12, 2012, King’s College London, UK. Sponsored by the International Association for Dental Research, FDI World Dental Federation, World Health Organization, United Nations Environmental Programme, and King’s College London Dental Institute.
INTRODUCTION
A
n unfortunate reality is that, despite being preventable, dental caries remains a ubiquitous disease globally. Worldwide, nearly 100% of the population in the majority of countries are affected (WHO, 2003; Petersen et al., 2005). Consequently, the need for restoration remains great. Many dental restorative materials exist, but there are challenges from numerous sources about the future and long-term viability of these materials. Among these are the United Nations Environmental Programme’s (UNEP) concern with controlling the use of mercury in products, including dental amalgam (Petersen, 2009), potentially endangering the future of amalgam, despite its world-wide acceptance as an excellent restorative material. Some restorative materials are not available in developing countries, a situation further exacerbated by the difficulties in successful use of the materials when electricity is not available, creating challenges in the use of light-cured materials and refrigerated storage demands. Concern with clinical performance of other materials prompted the US National Institutes of Health to request proposals supporting the design and development of novel dental composite restorative systems that demonstrate significant
DOI: 10.1177/0022034513502205 © International & American Associations for Dental Research
lifetime superiority over currently available Bis-GMA/TEGDMA-based systems (http://grants.nih.gov/grants/guide/rfa-files/ RFA-DE-13-001.html). Together, these challenges prompted the International Association for Dental Research (IADR), the World Health Organization (WHO), the United Nations Environmental Programme (UNEP), the FDI World Dental Federation (FDI), and King’s College London Dental Institute to sponsor a joint workshop in December 2012 to explore innovations in dental materials, with particular emphasis on direct restorative materials. It is recognized, however, that the availability and acceptance of new materials depend on factors far broader than their properties alone. Consequently, we engaged a dynamic group of experts to address the full scope of hurdles to design, produce, approve, and utilize any new but especially innovative materials. These experts were drawn from both dental and non-dental academic institutions, and industry, along with those from policy, research funding, and professional organizations. The presentations were thought provoking and the discussion lively. This issue of Advances in Dental Research offers highlights and summaries of the conversations in the following sessions: Session 1: The Challenge (Stephen Bayne, Moderator) •• A Global Perspective on Dental Caries Prevention and Treatment – presented by Poul Erik Peterson, WHO, Geneva, Switzerland, who tailored his remarks around the following questions: — What key aspects of restorative materials are required to effectively leverage caries prevention? — Will caries prevention ever be higher priority than treatment for dentists? Will prevention as a priority depend on payment schemes? — What is the potential impact of global high-speed communication on rapid progress in caries prevention? •• A Review of the UNEP Process to Develop a Treaty on Mercury – presented by David Piper, UNEP Deputy, Chemicals Branch, Geneva, Switzerland, who summarized the process, progress, and timetable of the complexities of reaching international agreement on mercury in the environment. •• Human Safety of Current Dental Restorative Materials – presented by Gottfried Schmalz, University of Regensburg, Germany, who tailored his remarks around the following questions:
Key Words biomedical research, dental restoration, private-public sector cooperation, dental economics, dental materials, patient advocacy.
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Adv Dent Res 25(1) 2013 Future Innovation and Research in Dental Restorative Materials 3 — What
is an acceptable risk-benefit ratio for restorative materials? — Do any current materials, used according to recommendations, pose a true biological threat to humans? — What is of greater concern from a biological standpoint, the materials as placed or their degradation by-products? •• Environmental Safety of Current Dental Restorative Materials – presented by Daniel Meyer, American Dental Association, Chicago, IL, USA, who tailored his remarks around the following questions: — What are the technical issues for using, maintaining, replacing, and recycling dental restorative materials? — What are the costs of safely managing and recycling restorative materials in a wide range of environments around the world where dental care is delivered? — Are current production methods for dental restorative materials environmentally friendly? If not, what processes can be improved, and how? — What additional challenges are introduced in resourcepoor settings? Session 2: Design Parameters/Specifications for an Ideal Dental Restorative Material (Dianne Rekow, Moderator) •• Clinical Characteristics – presented by Stephen Bayne, University of Michigan, Ann Arbor, MI, USA, who tailored his remarks around the following questions: — What are the clinical delivery and management systems that are needed for something to succeed in a wide range of environments? — What are the key properties (physical, chemical, mechanical, biological, and clinical) that a new successful restorative material should display vs. time? — Should manufacturers devote more time and effort to designing the easiest material to use, or invest more in clinical training for materials that are of highest quality but are more technique-sensitive? — What is more important for materials development: adequate performance in the hands of most professionals or optimal performance in the hands of highly skilled professionals? •• The Setting: Intra-oral and across the Globe – presented by Ricardo Carvalho, University of British Columbia, Vancouver, BC, Canada, who tailored his remarks around the following questions: — What different facilities and conditions exist in different regions of the world that preclude the delivery and use of a universal, ideal direct restorative material? — Is it an option for manufacturers to develop 2 or 3 levels of quality for their materials for different regions (i.e., lower cost and more easily delivered materials that are of acceptable, but not top of the line, quality)? — Should more effort be directed toward the development of alternative functional materials that can be produced locally at low cost? — What can be done to enhance the training of ‘less skilled’ personnel to deliver restorative dentistry in remote and difficult environments? •• Economic Considerations within the Health Care System – presented by Jimmy Steele, University of Newcastle,
Newcastle, UK, who tailored his remarks around the following questions: — What is a good model for understanding costs across different health care systems around the globe? — What is a practical way to weigh the cost/benefits of treatment vs. prevention and health? — What is a practical way to weigh the cost/benefits of repair vs. replacement of defective restorations?
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Session 3: Outside-the (cavity-Prep)-Box Thinking (Van Thompson, moderator) Adhesion and Adhesives – presented by Bamber Blackman, Imperial College, London, UK, who tailored his remarks around the following questions: — Are there testing and modeling methods used in engineering and materials science that would be of use to dental bonding? — Are there new adhesive technologies that could be applied to dentistry? — What outside environments are as hostile as the mouth, and what can we learn from them with respect to adhesive technologies? Managing the Tooth-Restoration Interface – presented by Tim Watson, King’s College London Dental Institute, London, UK, who tailored his comments around the following questions: — What is the full range of interfaces that are truly involved at the tooth-restoration zone (internal interfaces like fillerresin, restoration with bonding system, bonding system with tooth structure, damage zone on prepared tooth structure, potential interfaces with repair systems, and others)? — What are the challenges (adhesion, color sealing)? — Is there evidence that adhesion is critical for successful, durable restorations? Is the degradation of adhesives and adhesive layers really a clinical concern to be addressed for enhanced durability of dental restorations? Advances in Polymer Chemistry – presented by Jeffrey Stansbury, University of Colorado, Boulder, CO, USA, who tailored his comments around the following questions: — Can we eliminate BPA-based monomer systems in dentistry? — Is it possible to achieve high levels of reaction conversion in future products? — What is the best route to the development of polymers that are resistant to degradation by oral fluids, bacteria, enzymes, etc.? Polymeric Composites – presented by Linda Schadler, Rensselaer Polytechnic Institute, Troy, NY, US, who tailored her comments around the following questions: — What are the practical upper limits for toughness and fracture strength of polymer composites? — What are the new fabrication technologies for mesostructures? — What is the meso-structure and how would you characterize the special meso-contributions to properties? Nanomaterials – presented by Raymond Pearson, Lehigh University, Bethlehem, PA, US, who tailored his comments around the following questions:
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Are the current worries about nano-sized fillers warranted and, if so, is there a way to address these worries? — What are the 2 or 3 major property gains in working with materials with nano-structure? — What are the practical size ranges for nano-phases in nano-materials? •• Functional Dental Materials That Promote Remineralization – presented by Grayson Marshall, University of California San Francisco, San Francisco, CA, USA, who tailored his comments around the following questions: — What is the biological balance (availability of CA, PO4, F, and other ions) for effective remineralization? — Do we need to worry about ion-depletion of functional dental materials? — Are zones remineralized by functional dental materials more resistant to repeated demineralization? — What is the impact of reduced saliva flow on the potential of functional dental materials? •• Bio-inspired Complex Materials – presented by Rafael Libanori, ETH Zürich, Zürich, Switzerland, who tailored his remarks around the following questions: — What special processing methods/conditions are needed for these materials? — What are the properties of these materials? — What is the long-term functionality of these materials? — How well do these materials provide esthetics? Session 4. Incorporating New Materials and Techniques into Clinical Practice (Nigel Pitts, Moderator) •• Accelerating the Research to Regulatory Approval Process: The NIH/FDA Example – presented by James Drummond, NIH/NIDCR, Bethesda, MD, USA, who tailored his remarks around the following questions: — What should granting agencies solicit for future materials discovery and development strategies to shape their funding focus areas? — Should government granting agencies partner more closely with industry in co-funding mutually beneficial research, product testing, and evaluation? — Should government regulatory and funding agencies cosponsor symposia and workshops investigating ways to hasten the process of product approval? — How do environmental concerns factor into the development of a funding agency’s strategic planning and resource allocation? •• Intellectual Property/Patent and Regulatory Hurdles – presented by Rainer Guggenberger, 3M ESPE, Seefeld, Germany, who tailored his remarks around the following questions: — How do current regulatory processes across the globe negatively affect the development and marketing of new dental materials? — Is it possible for industry to partner with academia more closely to develop new products by establishing mutually beneficial ‘incubators’ at research-intensive schools? — What are the challenges, inconsistencies, and enforcement problems of a global patent system? •• Incorporating New Materials into Dental Education – presented by Patrick Ferrillo, International Federation of Dental
Adv Dent Res 25(1) 2013
Educators and Associations, San Francisco, CA, USA, who tailored his remarks around the following questions: — Should dental schools teach the latest materials being promoted by key opinion leaders to best prepare students for future dental practice? — Should students be required to participate in research during dental school to emphasize the importance of this process in materials development and use? — Should dental students become a ‘testing ground’ for new material types and brands to gain insight about the technique-sensitivity of new products? •• Incorporating New Materials into Current Practice—presented by Stuart Johnston, a dental practitioner representing FDI and the British Dental Association, UK, who tailored his remarks around the following questions: — What is the minimum in vitro and clinical evidence that practitioners need to make choices about using a new material? — On whom/what do practitioners most rely for information when choosing a new material? — How can this information be delivered to practitioners most efficiently and at the lowest cost?
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Session 5: Ensuring the Global Availability of High-quality Dental Restorative Materials (Jack Ferracane, moderator) Strategy with WHO, UNEP, Regional and National Regulatory Bodies – presented by Julian Fisher, FDI World Dental Federation, Geneva, Switzerland, who tailored his comments around the following questions: — Should there be a review of the effectiveness of existing dental materials that involves all interested groups and recurring on a five- or ten-year cycle? — Would it be helpful to have a research and development priority list developed and revisited on a routine basis to ensure that the world’s needs for new materials are met? An open conversation with industry representatives addressing the following questions: — What is the normal half-life for a new product? — How will competitors deliver a new product that might not be patented by any one of them? What if a new restorative material was ‘open source’? — Should manufacturers agree to purchase certain base components from single sources to ensure a uniform level of quality around the world? Role of National Dental Associations – presented by JeanLuc Eiselé, FDI World Dental Federation, Geneva, Switzerland, who tailored his comments around the following questions: — How should dental groups interact with the research base/ agencies? — How much influence should the national dental associations have? — How should the media be engaged? Research Advocacy Targeted at Government and Privateindustry Sources – presented by Christopher Fox, IADR, Alexandria, VA, USA, who tailored his comments around the following questions: — What are the politics of coordinating university, government, NGO, and corporate interests while cooperating to leverage a new strategy for patient care?
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Adv Dent Res 25(1) 2013 Future Innovation and Research in Dental Restorative Materials 5 — —
How do you ‘manage change’ in such a complex structure? How do dental materials research individuals (academics, etc.), advocate for change?
Session 6: Developing a Prioritized Agenda for Dental Materials Innovation and Research (moderated by Timothy Watson and Christopher Fox) •• This group discussion continued discussion from previous sessions, summarized challenges, and articulated research and advocacy priorities. In recent years, UNEP has expressed concern over the impact of mercury on the environment. In response to this, the WHO Global Oral Health Programme organized a Technical Consultation in Geneva in 2009 with the aim of identifying the scientific evidence on dental restorative materials, analyzing the conditions of providing dental care around the globe, and exploring the policies related to use of dental materials. WHO was the major catalyst for the workshop. Mercury-containing dental amalgam, with ever-improving formulations, has been successfully used throughout the world for over 150 years (Petersen, 2009). Amalgam has been shown to be exceptionally versatile, performing well in multiple classes of restoration, and, in the vast majority of low- and middle-income countries, is the preferred material for direct restorations. However, in the past decades, awareness and recognition of the environmental implications of mercury have increased. In 2001, the UNEP Governing Council requested a global assessment of mercury and its compounds. By 2007, UNEP formalized a Global Mercury Partnership with the objectives of: (1) minimizing and, if possible, eliminating the mercury supply; (2) minimizing and, where feasible, eliminating unintentional mercury releases to air, water, and land; (3) continuing minimization and elimination of global use and demand for mercury; and (4) promoting development of non-mercury technologies where suitable economically feasible alternatives do not exist (Reinhardt, 1988; Hilt et al., 2009). In 2009, the WHO Global Oral Health Program organized a technical meeting to assess the scientific evidence on use of dental restorative materials, including dental amalgam; the implications of using alternative restorative materials; and the quality of existing materials and the future needs for dental restorative materials. The complexity of developing new materials is often underappreciated. The patient, the restorative material, and the clinician or operator doing the restoration all contribute significantly to the clinical outcome (Fig.). Within each of these components, there are myriad factors that influence choices. Globally, only approximately 60% of the population worldwide has access to proper oral health care (Hosseinpoor et al., 2012); the density of qualified dentists varies from 1 out of 560 people in Croatia to 1 out of 1,278,446 in Ethiopia (Glick et al., 2012). Oral health varies dramatically throughout the world and even within small geographic regions. For instance, within London boroughs alone, percentages of children with dmft rates greater than zero vary from 19.9% to over 50% (http://www .nwph.net/dentalhealth/caveat.htm). Furthermore, a patient’s perceived value of dentistry in general and in saving a tooth specifically is necessarily influenced by his/her economic
condition: Without the resources to feed one’s family, health care is not likely to be a high priority. The availability of direct restorative materials and the introduction of new, especially innovative materials are surprisingly complex. Currently, 3 classes of restorative materials currently exist in addition to amalgam: resin-based composites, glassionomer cements, and resin-modified glass-ionomer. Yet none offers the same combination of ease of handling and clinical longevity as amalgam (Petersen, 2009). Alternative materials, some with extraordinary characteristics and material properties, are being explored in laboratories both within the dental community and in the wider materials science community. These include materials that promote remineralization (Gower, 2008; Banerjee et al., 2011; Bertassoni et al., 2011), improved adhesion and fracture resistance (Blackman et al., 2013), advances in polymer chemistry and composite resin systems (Moraes et al., 2011; Liu et al., 2012), and integration of the advantages of nanocomposites (Akcora et al., 2009; Dittanet and Pearson, 2013) and bioinspired complex materials (Erb et al., 2012; Libanori et al., 2012). However, existence of the material is a necessary but far from sufficient criterion to ensure its availability. Safety considerations are critical. Dental materials have been shown to have very low toxicity compared with those used in cosmetics (Orton and Wilkinson, 2004; Gawkrodger, 2005). Yet for some, there remains what might best be called the ‘emotional toxicity’ of amalgam. The introduction of any new material faces an array of regulatory hurdles. Many are similar to those of the US Food and Drug Administration, where materials similar to those already in use are more straightforward than innovative ones. Unfortunately, there is little agreement between and among countries about the amount of testing needed to prove similarity or differences, creating expensive demands on manufacturers. Not surprisingly, this can result in limited geographic distribution of products or a decision not to pursue some potentially exceptionally performing materials because they are too costly to bring to the market. The environmental impact of materials is clearly evident in the UNEP actions described above. It is important to appreciate that the environmental impact spans the material’s lifetime – from acquisition of the raw materials through removal from the patient. For amalgam, mercury, of course, is a major constituent in its production. It has also been the focus of best practices for amalgam waste, which aim to minimize mercury discharge into the environment (Fan et al., 2002). Similar birth-to-death considerations must be considered for all materials. Obviously companies make restorative materials available. It would be naïve to assume that profitability of the product is not important. It is notable, however, that a social responsibility ethos in many companies delivers materials and services in some markets and regions that are not profitable. The clinician or operator treating the patient and placing the restoration is immensely important in determining clinical outcomes. Comparison of failure rates between controlled clinical studies and practice-based studies suggests that both failure rates and restoration failure modes can differ dramatically (Bayne, 2012). Surely some of this difference results from
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Acknowledgments
Research and Advocacy • Demographics • Oral health • Tooth condion • Perceived value
Paent
• Funding • Partnerships
Restorave Material(s)
• State of the science • Innovaons • Material properes • Safety • Regulatory constraints • Environmental impact • Geographic locaon • Corporate priories
Clinician/ Operator
Adv Dent Res 25(1) 2013
• Operator skill • Paent behaviors
Clinical Outcome
• Materials available • Educaon • Health care system • Informaon resources • Paent oral health • Tooth locaon/condion
Figure. Interdependencies of factors contributing to innovation and research in dental restorative materials.
material choices and proper diagnosis. Those, in turn, are influenced by the education of the clinician/operator. There need not necessarily be a direct correlation between years of academic training study and effectiveness, however, as has been shown by at least short-term successes with restorations placed by nondentists (Bader et al., 2011; Freeman et al., 2013). It is tempting to assume that treatment decisions depend upon only the patient and the clinician. However, the health care system can profoundly influence decisions about whether, when, how, and how quickly treatment can be rendered and new materials introduced (Coulter et al., 2004). It will be further informed by the information resources upon which the clinician relies for understanding expectations about the performance of alternative materials. These can range from advertisement claims, to proclamations and recommendations by peers and spokesmen, to high-quality laboratory research (which may or may not reliably predict clinical performance), to long-term clinical studies (where the product may no longer be available). Few would argue the value of research in improving clinical outcomes. Yet, disappointingly, research funding for new dental materials has apparently not been a priority for funding agencies. Similarly, funding support to train the next generation of materials scientists with a focus on dental materials has been disappointingly low. Consequently, the emphasis of materials science research has now shifted from university- to corporate-based settings. While many excellent scientists engage in corporate research, corporate priorities and intellectual property considerations can potentially limit the wide sharing of discoveries. Undoubtedly, advocacy plays an important role in reducing barriers to progress. Advocacy for increased funding for innovation in materials and investment in future scientists is obvious. But there is also a strong need to harmonize regulatory barriers. There is a burning need to overcome the considerable obstacles preventing delivery of excellent health care throughout the world. IADR has built solid relationships with funding, policy, and professional organizations. Capitalizing on these relationships, its leaders and members are well-positioned to make a difference to materials science and oral health.
Without the support of IADR, WHO, FDI, and UNEP, we would not have been able to define the content of the workshop. The following corporations were instrumental in providing scientific expertise and unrestricted grants to IADR for support of the workshop: 3M ESPE, Dentsply De Trey GmbH, Dentsply International, DMG Dental-Materials Gesellschaft bH, GC Corporation, Ivoclar Vivadent AG, and Kerr Corporation. We thank the numerous attendees, who provided their own support to share their ideas and expertise with us. We acknowledge the efforts of Tim Watson, Steve Bayne, and Jack Ferracane in drafting the questions that formed the basis for the presentations, and we recognize the valuable notes of the discussions summarized by Mathilde “Tilly” Peters and Sally Marshall. C.H. Fox serves as the Executive Director of the International Association for Dental Research. The authors received no financial support and declare no potential conflicts of interest with respect to the authorship and/or publication of this article.
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