The post-amalgam revolution has begun!

With the decision to phase out dental amalgam in the European Union, the search for alternative restorative materials and treatment concepts has been initiated. An evaluation of the current situation reveals that many suitable approaches are already available, while some work still needs to be done. This is the essence of the three lectures held during the 3M Symposium titled “The post-amalgam revolution” that took place on Friday, July 27, 2018 during the IADR/PER General Session in London.

by Dr Sigrid Hader and Christiane Stein, Germany.Date of Original: November 2018 - 3M Dental Magazine

Minimally-invasive caries removalThe first speaker, Prof Avijit Banerjee (King’s College London Dental Institute), focused on contemporary operative concepts for carious lesion management. Leveraging a huge body of scientific evidence, he stressed that it is time to move away from the classical concept of cavity preparation towards less invasive procedures. Study results are already available to show that it is no longer necessary to excavate all dentine bacterial biomass (i.e. infected and affected dentine)

to prevent further disease progression. Instead, only the superficial layer of infected necrotic dentine needs to be removed. In addition, peripheral caries removal must be ensured in order to be able to seal the cavity and to arrest the lesion under the lining. Arrest is only possible if a complete seal can be obtained and maintained, which is the case whenever starting and finishing in healthy enamel.

For long-term success, the speaker recommended that a balance must be achieved using minimally invasive operative concepts, between the quality of the tooth substrate retained (affected dentine or healthy enamel at the cavity periphery), the chemistry of the restorative material used and the clinical handling of both the material and tooth structure. Its imperative long-term success revolves around the maintenance of pulp sensibility and tooth structure, as opposed to assessing the quality of the restoration itself – consider the complete tooth-restoration complex.

IADR Symposium with approximately 200 participants.

Future restorative materialsThe fact that there is still a need for improvement of direct restorative materials was highlighted by Prof Timothy Watson (King’s College London Dental Institute). He provided an insight into what is happening to the weakened carious substrate in the context of restoration and what is going on at the interface between the tooth tissue and restorative materials. The available evidence shows that, using resin-based adhesive systems for bonding, a hybrid layer is formed also on caries-affected dentine, but that this layer is prone to hydrolytic degradation, meaning that the interface is going to break down over time. According to the speaker, the use of materials that can reinforce the hybrid layer and encapsulate the collagen fibrils might be a solution.

Some of the available bioactive materials already have this ability, as revealed using different methods of optical analysis including fluorescence and Raman spectra. These materials are able to induce changes in the mineral content of affected and infected dentine, so that a rebuilding of the dentine structure seems possible. However, the commercially available products are usually used for temporary restoration only and have unfavourable optical properties. Hence, Prof Watson expressed the need for stronger, more aesthetic and simpler-to-use materials that offer this desired effect.

A resin-based, self-adhesive hybrid ionomer material is currently being developed: Initial laboratory studies have revealed that it is not losing its retentive properties on the tooth over time. The speaker presented images from fluorescence analysis which confirm that, unlike composite material, the experimental material is clearly able to improve the properties of the carious dentine. This hints to the fact that the experimental formulation might contribute to simpler and clinically successful aesthetic restorative procedures.

Prof Avijit Banerjee lecturing about minimally-invasive operative techniques.

Prof Timothy Watson unveiling the truth about future restorative materials.

Prof Ivo Krejci during his passionate plea for the placement of onlays instead of crowns.

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Onlays instead of crowns

Finally, Prof Ivo Krejci (University of Geneva) presented his concept of restoration replacement or re-dentistry. In line with scientific study results, he never places ceramic crowns and opts for composite onlays instead. Even endodontically treated teeth do not receive a post and core restoration and a crown, but an endocrown which is very similar to an onlay. These types of restorations are possible today due to the availability of high-performance dental adhesives. What is important for the success of endocrowns is the availability of a sufficiently large surface for bonding, which might be calculated in the future during treatment planning with the aid of an intraoral scanner and finite element analysis.

In order to avoid catastrophic fractures after the replacement of amalgam restorations, the speaker promotes a reinforcement of the tooth. His hypothesis is that the fractures originate from an existing fissure or fracture underneath the amalgam restoration. Especially high-copper amalgams (introduced after the 1970s) seem to induce fissures that lead to tooth fractures.

Hence, these restorations should be replaced as soon as possible. In order to reinforce the tooth, the speaker includes a glass-fiber network in the adhesive layer on the prepared tooth surface. On top of this layer, he applies light-curing composite instead of a resin cement to lute the composite onlay. One of the benefits of this type of restoration is that there is no need for a perfect fit, as a monoblock is created and slight inaccuracies are compensated by the composite filling material. This makes the procedure very simple and leads to good clinical results.

Speakers and organisers of the 3M Symposium.

3M employees at the company’s booth during the IADR/PER General Session.

Outlook In the end, all speakers agreed that minimally invasive operative techniques and materials supporting these procedures are the way forward in restorative dentistry. The concepts presented by them have already proven their worth in the clinical environment. Now, it is time that general dental practitioners start implementing them in their dental offices.

Successful event

Not only the symposium, but the whole congress in London was a huge success for 3M. More than 20 employees from Seefeld, St. Paul and Loughborough (UK) were present to showcase their research results in poster presentations and oral sessions and to network with visitors at the 3M booth as well as in the presentation area.

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Dr Sigrid Hader

Dr Sigrid Hader obtained her Doctor of Medicine (MD) and PhD degrees at the University of Cologne in Germany as well as certificates in Emergency Medicine and Immuno-Allergology from the Université Paris V in France. She worked as a medical consultant and clinical research manager for large medical and pharmaceutical companies before joining the dental products division of 3M in 2005. She is now a Global Scientific Affairs Manager responsible for prosthodontic products based in Seefeld, Germany.

Christiane Stein

Christiane Stein is educated in Pharmaceutical Sciences. She worked at the chair of pharmaceutical technology, Ludwig Maximilians University Munich for several years. Afterwards, she was employed in a pharmacy in Munich and in the drug regulatory department of a pharmaceutical company before joining the company 3M ESPE in Seefeld as a Regulatory Affairs Manager – Drug Registration in 1998. Since 2004, she holds the position of a Scientific Affairs Manager, currently responsible for direct restoratives.

Contact: Dr Sigrid Hader Scientific Affairs Manager 3M Oral Care shader@3M.com

Contact: Christiane Stein Scientific Affairs Manager 3M Oral Care christiane.stein@3M.com

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Published by 3M Oral Care. 3M, “3M Science. Applied to Life.” and Espertise are trademarks of 3M. 3M Health Care Academy is a service mark of 3M. All other trademarks are owned by other companies. Please always follow the 3M Product Instructions For Use for best clinical results. © 3M 2019. All rights reserved.

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