Topically applied desensitizing agents. Before the discovery of local anesthetics, dentists would use toxic chemicals such as silver nitrate, zinc chloride, potash and arsenic compounds to obtund dentin. Now, less toxic materials are used for desensitization (Table 1 53–59 ). View this table: [in this window] [in a new window] TABLE 1 Solutions and products tested in clinical trials. Fluoride. Fluorides such as sodium fluoride and stannous fluoride can reduce dentin sensitivity. 53 Fluorides decrease the permeability of dentin in vitro, 22 possibly by precipitation of insoluble calcium fluoride within the tubules. Potassium nitrate. Potassium nitrate, which usually is applied via a desensitizing toothpaste, also can reduce dentin sensitivity when applied topically in an aqueous solution 54 or an adhesive gel. 55 Potassium nitrate does not reduce dentin permeability in vitro, 22 but potassium ions do reduce nerve excitability in animal models. 26,37 Oxalate. In 1981, Greenhill and Pashley 22 reported that 30 percent potassium oxalate caused a 98 percent reduction in dentin permeability in vitro. Since then, numerous oxalate-based desensitizing products have become available. Oxalate products reduce dentin permeability and occlude tubules more consistently in laboratory studies 60,61 than they do in clinical trials. 36 Some studies indicated that oxalates significantly reduced sensitivity, 56–58 while others reported that the effects of oxalate did not differ significantly from those of a placebo. 53,58 Calcium phosphates. Calcium phosphates may reduce dentin sensitivity effectively. 59 Calcium phosphates occlude dentinal tubules in vitro 62,63 and decrease in vitro dentin permeability. 64 Adhesives and resins. Because many topical desensitizing agents do not adhere to the dentin surface, their effects are temporary. Stronger and more adhesive materials offer improved and longer-lasting desensitization (Figure 3 ). In the 1970s, Brännström and colleagues 65 suggested using resin impregnation to desensitize dentin. Current DH treatments involve using adhesives, including varnishes, bonding agents and restorative materials. Practitioners should be aware that clinical trials of adhesive desensitizing materials tend to be pragmatic. Many of these trials are single-blind studies because true double-blind conditions are difficult to achieve. Table 2 53,66–77 presents a list of products tested since 1999 that claim to occlude tubules in hypersensitive dentin. View this table: [in this window] [in a new window] TABLE 2 Adhesives and resins tested in clinical trials. Other procedures. Ionto-phoresis. This procedure uses electricity to enhance diffusion of
