Re-mineralising, antibacterial composites and adhesives for more durable, conservative and pain less tooth restoration

Dental caries is caused by specific acid producing bacteria that demineralise enamel and dentine. If left unchecked, infection of the dentine pulp complex and associated pain occurs. Treatment costs then escalate several folds, particularly if root canal procedures or tooth replacement with implants is ultimately required. Dental caries is the most common disease in humans. Almost 40% of UK adults have at least one untreated carious tooth. This rises to 60-90% for children or across the whole population in deprived nations. Pain and tooth loss from dental caries is associated with significant adverse impact on quality of life. Damaged or infected tooth structure must be partially or totally replaced in order to halt disease progression, preserve function and improve aesthetics. Tooth restoration treatments have enabled the UK population to keep its teeth for longer. The financial cost of restoration maintenance, however, is high due to their limited lifetime expectancy. Amalgam restorations are increasingly being replaced by more aesthetic white composites. Composites have good strength and wear resistance but the procedures used to bond them to teeth are complex and require a skilled dentist. The main reason for composite replacement is adhesive failure due to combined bacterial and enzyme action. This failure enables microgap formation between the tooth and restoration through which more bacteria and enzymes can penetrate. As composites have no antibacterial action re-infection subsequently occurs. An alternative method of treatment is the ART approach. The atraumatic restorative technique (ART) was originally developed for regions of the world with limited electricity supply and no access to dentists and the associated infrastructure eg dental chair, compressed air etc. It is also favoured, however, by children due to reduced use of local anaesthetics / drills and greater procedure simplicity. It uses hand instruments to remove the bulk of the carious tissue and then a glass ionomer cement (GIC) to seal the cavity. Sealing halts the spread of any remaining infection. The good durability of the GIC / dentine bond has enabled this method to succeed in small cavities but failure in larger restorations is common due poor GIC strength. The aim of this study is therefore to develop new materials that are simpler to place, have the high strength of composites but the dentine adherence durability of GICs. These new materials contain a combination of components from dental composites and GICs but also calcium phosphate bone cements. In addition they contain antibacterial agents used in mouth washes and food preservatives. Effective antibacterial properties will enable the materials to be placed without the need for total removal of infected dental tissue. Furthermore the materials will release calcium phosphates that can undo the demineralisation damage caused by bacteria and thereby stabilise dentine against enzymes. This will enable a higher percentage of the original tooth structure to be preserved. Further smart features of the new materials will include their increase in antibacterial and calcium phosphate release in the presence of bacteria. Moreover, they will have the ability to self repair after any damage caused by chewing or large temperature variations (for example upon drinking hot drinks or eating ice cream). The conclusion will be increased restoration longevity and reduced pain and cost associated with dental caries.

The major beneficiaries of the proposed research will be the very high numbers of patients with dental caries which still remains one of the most common human diseases throughout the world. Use of the new dental materials under development will mean that patients have longer lasting antibacterial dental restorations that can actively respond if disease returns. Given that dental treatment costs the economy of the UK hundreds of millions of pounds every year this will have significant cost benefit. The antibacterial and re-mineralising material features will allow for simplified tooth restoration procedures. This will particularly benefit children, anxious patients and people in regions of the world with limited access to dental staff and supporting dental infrastructure. Furthermore, as very similar materials are simultaneously being developed within our group for bone repair, beneficiaries extend to the very large number of patients with bone defects arising via trauma or disease (e.g. osteoporosis and cancer). Moreover, the new materials are capable of providing sustained release of components that can aid treatment of disease. This proposal focuses upon antibacterial and calcium phosphate release but with, for example, addition of strontium ions improved bone repair is also possible. These ions are currently used in high oral doses to treat osteoporosis but their release from bone adhesives would provide a localised, more effective treatment with substantially reduced side effects. Similarly, sustained and localised release of anticancer drugs would enable reduced ill effects of these often highly toxic compounds. Further beneficiaries include one new and a further established family UK business working with us to develop the materials. These companies will speed up delivery of formulations to the public. Our current aim is a new bone adhesive in clinical trials by 2012 and tooth restoration materials available in 2014. These companies will ultimately supply the formulations through their international sales teams to clinicians. This will provide both UK jobs and income from overseas. These companies furthermore provide early funds to support fundamental research by students and staff within UCL. The work additionally encourages overseas students whose fees help support UK universities whilst simultaneously aiding international development.