Professor John W. Nicholson

The Bioactivity of Glass-Ionomer Cements

This presentation will review the evidence for the bioactivity of glass-ionomer dental cements. There is currently considerable interest in the possibility of improving the bioactivity of these materials, most typically by including bioactive glass as an additional filler. Such an approach usually assumes that glass-ionomers lack any inherent bioactivity of their own but, as will be discussed, this is not true.
The first artificial material to be described as “bioactive” was the so-called “Bioglass” invented in the USA by Professor Larry Hench in 1969. It was called “bioactive” because it formed a mechanically strong bond to living bone. This characteristic became the defining feature of a bioactive material, i.e. the ability to form a mechanically strong bond to living tissue.
For many years, it has been known that glass-ionomers will form such a bond to vital dentine. However, the significance of this behaviour has been largely overlooked. Nonetheless, it is behaviour that is analogous to that of Bioglass and as such should be taken as evidence that glass-ionomers, too, are bioactive.

Bioglass has two other features that are considered important in making it bioactive, namely that it releases biologically beneficial ions and alters slightly the local pH around the implant. Published studies show that these two behaviours are also displayed by glass-ionomer cements. These materials release ions such as Ca2+ (or Sr2+), Na+, silicate and phosphate, all of which are beneficial biologically. These ions are released in addition to fluoride, a species which also has an active biological role in promoting remineralisation of dentine and enamel.
Overall, by reconsidering much that is known about glass-ionomers, it is clear that they should be considered bioactive, and that this is significant in their clinical role. As more emphasis is placed on bioactivity in dental restorative materials, it is important to recognise this advantage of glass-ionomer cements, and to promote their use in circumstances where this feature is particularly desirable.

Professor John Nicholson is a materials chemist whose work is mainly concerned with glass-ionomer dental cements, though he has also published work on dental implants, bioglass, dental adhesion and resin composites. He graduated in chemistry from Kingston University in London, after which he took his PhD, also in chemistry, at London South Bank University. Following this, he became a member of staff at the UK Laboratory of the Government Chemist, where he worked under the late Dr Alan Wilson, the inventor of the glass-ionomer cement.

After 11 years at the Government laboratory, Professor Nicholson moved to the Dental Institute of King’s College, London, as Head of Materials. There, he led the teaching and research in dental biomaterials. He then moved to become full Professor of Biomaterials Chemistry at the University of Greenwich, and while in this post, was awarded a second doctorate (DSc) for his research contributions to materials chemistry. In 2015, Professor Nicholson changed roles and became Senior Research Fellow in the Dental Physical Sciences Unit at the Institute of Dentistry, Queen Mary University of London. He also became Director of the Bluefield Centre for Biomaterials, London.
Professor Nicholson has published just over 200 scientific papers and five books, as well as additional invited chapters. He was recently named in the Stanford University Top 2% of World Scientists on the basis of his scientific publications.
Professor Nicholson is married with four adult children, and lives near London.