While the treatment of dentin hypersensitivity (DH) with oxalates is a common practice in dentistry, clinical studies have not established the efficacy of the compound, a conjugate base of oxalic acid.
Researchers at the University of Washington School of Dentistry sought to clear up the matter with a systematic review of clinical trials that compared oxalate treatment to no treatment at all and those that used a placebo (Journal of Dental Research, December 29, 2010).
More than a dozen different ways of diagnosing dentin hypersensitivity exist, and it is treated with varrious strategies, most of which "seek to occlude the exposed dentin with restorative materials, laser treatment, resin-based sealants, or pharmacological agents," the researchers noted. However, oxalates have a particularly high level of acceptance and an extensive history of use.
The team pared down 677 unique citations to 12 reports and subjected them to a detailed analysis. Nine of them were split-mouth trials and eight evaluated a type of monohydrogen-monopotassium oxalate.
Dentists -- 40% of whom use oxalates to treat dentin hypersensitivity, according to a recent survey -- may be surprised by the researchers' key conclusion: that oxalates were no more effective than a placebo in treating DH.
While the review suggests that only 3% monohydrogen-monopotassium may be worthy of this acceptance, the authors acknowledge that "analysis of current data, taken together, cannot determine whether a lack of effect was from a truly ineffective treatment or study design limitations."
Determining the efficacy of oxalates is a challenging proposal, the researchers noted, due in part to dentin hypersensitivity's "intermittent nature," coupled with robust placebo effects. Even so, the authors criticize previous clinical trials, noting that "the effect of DH treatments remains unclear because of the diverse and sometimes lax methods that have been used to assess efficacy."
The authors found the selection of treatments to be tested in these studies to be curious as well. Of them, the second-most common examined was a combination of 3% monohydrogen-monopotassium and 30% dipotassium oxalate. The "paradox" that the authors note stems from the fact that 30% dipotassium oxalate alone had no effect in the studies reviewed, while favorable results existed for the usage of 3% monohydrogen-monopotassium.
Consequently, it appears as though "some sort of interference or competition between these two treatments, or important and as-yet-unidentified factors in how the two treatments are applied" exists, the authors noted. As a result, they see no significant reason to use this complex regimen medically.
Looking ahead to future dentin hypersensitivity trials involving oxalates, the researchers recommend strict study protocols that include randomization and allocation concealment. The standardization of pain measurement receives particular focus, since many of the studies reviewed used different stimuli to elicit pain, and treatments decreased DH pain for some stimuli, but not others, they wrote.
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