43 DENTAL ASIA MARCH / APRIL 2018 Clinical Feature Cycling of oral pHduring cariogenic challenges inƪuoridated hydroxyapatite Fig. 4 Glass ionomers create an ion enriched harder dentin surface adjacent to the glass ionomer surface. Fig. 3 & 3B Examples of glass ionomers, Riva Self Cure (SDI) and Equia Forte (GC). These are bioactive materials that remineralise. If ƪuoride is present in the plaque ƪuid, it will penetrate the enamel, along with the acids at the subsurface, adsorb to the apatite crystal surface and protect the crystals from dissolution. 6 This coating makes the crystals similar to ƪuorapatite (critical pH of 4.5), ensuring that no demineralisation takes place until the pH reaches this point. Fluoride present in solution at low levels among the enamel crystals can markedly decrease demineralisation . 7,8 When the pH returns to 5.5 or above, the saliva which is supersaturated with calcium and phosphate, forces minerals back into the tooth. 8 Fluoride increases remineralisation by bringing calcium and phosphate ions together and is also preferentially incorporated into the remineralised surface, which is now more acid resistant. The beneƤts of ƪuoride are maintained long-term through the mechanism of fluoride reservoirs . Fluoride is retained intraorally after ƪuoride treatments suchasƪuoridated toothpasteandƪuoride varnish application and is then released into the saliva over time. 9,10 Fluoride can remain on teeth, mucosa, dental plaque or within bioactive restorative materials. Fluoride retention is clinically beneƤcial since it can be released during cariogenic challenges to decreasedemineralisationand enhance remineralisation. 5 When the enamel and dentin no longer have adequate structure to maintain their mineral framework, cavitation takes place and simple remineralisation is an insu ƥ cient treatment. Tooth preparation and restoration are now required. Bioactive restorative materials replace dental hard tissues and help to remineralise the remaining dental structures. Glass ionomer cements and their derivatives, such as resinmodiƤed glass ionomers, compomers and giomers, fall into this category. Glass ionomer cements encourage remineralisation Glass ionomer cements were developed in the early 1970s. They are particularly valuable for caries control in high caries risk patients and in areas where location or isolation create restorative challenges (Fig. 3). Glass ionomers have a true chemical bondwith dental tissue. They encourage remineralisation of the surrounding tooth structure and prevent bacterial microleakage through ion-exchange adhesion with both enamel and dentin. 11 A new, ion-enriched layer is created at the tooth-glass ionomer interface. This layer contains phosphate and calcium ions from the dental tissues, and calcium ( o r s t r o n t i um) , p h o s p h a t e a n d a l um i n um f r om the glass ionomer c e m e n t . 1 1 T h e r emi ne r a l i s a t i on p r oc e s s c r ea t e s a ha r de r den t i n surface (Fig. 4). 12,43 Restoration fracture is usually cohesive, leaving the ion exchange layer Ƥrmly attached to the cavity wall. The dentinal tubules are sealed and protected from bacterial penetration. 13 To eliminate the physical property disadvantages of glass ionomers and harness their remineralising benefits, dental researchers have produced an assortment of glass ionomers derivatives: resin modiƤed glass ionomers, compomers and giomers. Twoproductlinesinthiscategoryare: ActivaBioACTIVERestorative (Pulpdent, Watertown, MA) (Fig. 5) and the BeautiƤl giomer family of restorative materials including Beautifil II and BeautiƤl Flo Plus (Shofu Dental, San Marcos, CA) (Fig. 6). Studies have shown ACTIVA’s remineralisation potential through ƪuoride release and recharge and calcium release. 14,15 Giomers are used i n r e s t o r a t i v e d e n t i s t r y a s equivalent to composite resin, in all their applications. Fig. 5 Activa BioACTIVE Restorative (Pulpdent) is a bioactive restorative material that remineralises.