JM: How is the phase out of dental amalgam affecting clinicians in daily practice?
AB: Technically, the approach is still a ‘phase-down’ of the use of amalgam, due to the environmental impact of mining and disposing of mercury. There are already restrictions in place, as advised by SDCEP guidelines, requiring the use of alternative materials in children and pregnant/breast-feeding women in the UK and other countries. Several Scandinavian countries have banned the use of amalgam in dentistry for many years.
Primarily, practitioners are now having to master the use of adhesive direct plastic materials – glass-ionomers and resin composites – as prevention of caries takes a more prominent position in minimum intervention oral healthcare plans, especially in the post-pandemic era. There is still some resistance to the changes, but the clinical indications for the use of amalgam as the first-choice, go-to restorative material are nowadays limited.
JM: The profession and industry often refer to an ‘amalgam alternative’ – is this a fair description of what is required clinically?
AB: I wouldn’t describe the development of new restorative biomaterials as ‘amalgam alternatives’ or ‘amalgam replacements’. Amalgam itself is an old material with several useful mechanical properties and has served the profession well in the era of ‘surgical’ caries management, where teeth have been cut to serve its purpose. However, with the advent and implementation of minimally invasive dentistry, a biological operative approach is now required, without the need for standardised cavity shapes being prepared specifically for the restorative material.
Amalgam has limited or no biological benefits with regards to caries management. Therefore, research and development in biomaterials needs to be searching for better materials, rather than alternatives or replacements. These ideally will provide a stimulus for biological healing of dental tissues, simple and reliable chemical adhesion mechanisms in the normal oral environment to provide a retentive seal and suitable strength and aesthetics to provide long-lasting, durable, load-bearing restorations in teeth.
JM: What are the specific advantages of GC’s glass hybrid technology over traditional resin composites and mercury-free glass-ionomers in this field?
AB: The beauty of glass hybrid ionomer technology is the fact that the conventional glass-ionomer chemistry is enhanced. The relative weaknesses of glass-ionomer cements (GICs) are in their relative lack of physical durability and strength in function, when compared to tooth structure and the other restorative materials currently in use. It appears, from the currently available laboratory and clinical data, that the glass hybrid technology improves these qualities, making it a more viable definitive restorative material, while fulfilling many of the requirements of a companion material for minimally invasive dentistry.
JM: What are the clinical indications of glass hybrid materials, their physical and mechanical properties, clinical application and expected longevity?
AB: Glass hybrid materials can be placed in situations where conventional GICs would normally be considered. Due to their improved strength, early clinical trial evidence is showing a potential for its use in occlusal posterior restorations, as a definitive alternative. The resin coat that is applied seems important in this regard. The jury is still out regarding its use in posterior load-bearing proximal cavities, but further improvements and trial data may change this view in the future.