Dental materials : official publication of the Academy of Dental Materials · 2026
Mechanistic insights into oxalate-based desensitizers: Calcium oxalate deposition and reduced calcium release under acid challenge.
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Oguma Hidetoshi, Yoshihara Kumiko, Nakanishi Ko, Okihara Takumi, Nagaoka Noriyuki, Lee Sungho, Akasaka Tsukasa, Nakamura Mariko, Matsuda Yasuhiro, Fukuda Ryuichi, Inoue Satoshi, Van Meerbeek Bart, Yoshida Yasuhiro
Аннотация
OBJECTIVE: Oxalate salts are used clinically as a desensitizing agent; however, the physicochemical mechanisms underlying its interaction with hard dental tissues are unclear. This study aimed at elucidating how oxalic acid treatment affects the demineralization behavior of hydroxyapatite (HAp), focusing on ion redistribution, phase formation, and the reversibility of its protective effect.
METHODS: HAp powder was treated with oxalic acid solutions at concentrations ranging from 0.001 to 0.5 M. Calcium and phosphorus released from dentin surfaces during oxalic acid treatment and subsequent lactic acid challenge were quantified using inductively coupled plasma optical emission spectrometry (ICP-OES). The solid phases formed following oxalic acid treatment were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The demineralization behaviors of test samples exposed to lactic acid immediately after oxalic acid treatment and those that were washed and dried prior to demineralization were compared.
RESULTS: Oxalic acid treatment of dentin surfaces induced a concentration-dependent redistribution of calcium and phosphorus, with calcium release from the surfaces reducing as the oxalic acid concentration increased. XRD and FTIR analyses revealed the formation of a calcium oxalate phase concomitant with the attenuation of the HAp signals. Demineralization of the HAp surface was markedly suppressed when the calcium oxalate layer remained on the surface. Washing and drying eliminated the protective effect of the calcium oxalate layer, indicating that oxalic acid does not permanently alter the intrinsic acid resistance of HAp.
SIGNIFICANCE: The study findings demonstrated that oxalic acid acts via a reversible surface modification mechanism based on the formation of a stable, low-solubility calcium oxalate layer. This mechanism rationally explains the clinical efficacy of oxalic acid-based desensitizing agents, which are likely to function through the transient suppression of demineralization and occlusion of dentinal tubules rather than long-term mineral reinforcement.
METHODS: HAp powder was treated with oxalic acid solutions at concentrations ranging from 0.001 to 0.5 M. Calcium and phosphorus released from dentin surfaces during oxalic acid treatment and subsequent lactic acid challenge were quantified using inductively coupled plasma optical emission spectrometry (ICP-OES). The solid phases formed following oxalic acid treatment were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The demineralization behaviors of test samples exposed to lactic acid immediately after oxalic acid treatment and those that were washed and dried prior to demineralization were compared.
RESULTS: Oxalic acid treatment of dentin surfaces induced a concentration-dependent redistribution of calcium and phosphorus, with calcium release from the surfaces reducing as the oxalic acid concentration increased. XRD and FTIR analyses revealed the formation of a calcium oxalate phase concomitant with the attenuation of the HAp signals. Demineralization of the HAp surface was markedly suppressed when the calcium oxalate layer remained on the surface. Washing and drying eliminated the protective effect of the calcium oxalate layer, indicating that oxalic acid does not permanently alter the intrinsic acid resistance of HAp.
SIGNIFICANCE: The study findings demonstrated that oxalic acid acts via a reversible surface modification mechanism based on the formation of a stable, low-solubility calcium oxalate layer. This mechanism rationally explains the clinical efficacy of oxalic acid-based desensitizing agents, which are likely to function through the transient suppression of demineralization and occlusion of dentinal tubules rather than long-term mineral reinforcement.