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cosmetic dentistry - beauty & science

research _ conservative dentistry I dentine (softened tooth structure that cannot be remineralised)16 and the preservation of affected dentine(infectedtoothstructurethatcanbehealed and remineralised; Fig. 1). The slow-speed Smart- Burs II relies on the hardness of the tooth structure, and not tissue staining, to determine the end-point scientifically. Its specifically designed Knoop hard- ness (harder than diseased dentine but softer than healthy dentine) allows the bur to remove soft cari- ous dentine selectively while not cutting the harder healthy dentine. A carbide or diamond bur can inadvertently penetrate through the thin remaining dentine into the pulp (Figs. 2 & 3). SmartBurs II, however, is de- graded by healthy dentine and ceases to cut (Figs. 4 & 5). These burs are used after the initial caries access preparation has exposed the deep, underlying caries. In cases in which the caries is exposed (Fig. 6), these instruments can typi- cally be utilised without the need for local anaesthetic because they do not traumatise or open healthy dentinal tubules (Fig. 7). _Cavity disinfection It is well established that some bacteria remain in the prepared tooth structures, no matterhowthoroughthepreparationprocess, anddespiteatactilefirmnessandnon-stained appearance. It is now possible to greatly de- creasethelikelihoodofviablebacteriabeneath therestorationbychemotherapeuticmethods that can penetrate as far as 2 to 3 mm into the remaining enamel or dentine. These tech- niques effectively destroy bacterial viability andpermitthesubsequentremineralisationof compromised tooth structures. The technologies that have been shown to be effective surface bactericides are: _ASEPTIM Plus Photo-Activated Disinfection system (SciCan; Fig. 8):17 This compact unit utilises tolonium chloride to stain liposomes specifically in bacterial cell walls. The stain is subsequently targeted by a red diode light that releases oxygen ions (Fig. 9). These ions break the liposomesopen,rupturingthecellwalls,andkilling the bacteria. _The ions are immediately, and selectively, toxic to bacteria. A very low level of ozone concentra- tion is required for a comprehensive bactericidal effect.18–20 _HealOzone (CurOzone USA; Fig. 10): The ozone ions are generated remotely and introduced to the tip-sealed tooth surface through a handpiece. The high concentration of ozone is very effective in bacterial wall disruption and destroys bacteria within 20 to 40 seconds (Fig. 11).21–24 HealOzone unit is available at www.ukdent.com. I 15cosmeticdentistry 3_2012 Fig. 6 Fig. 7 Fig. 10 Fig. 11 Fig. 8 Fig. 9