School of Dentistry, University of Western Ontario, London, Ontario, N6A 5C1, Canada.
Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7, Canada.
Arch Oral Biol. 2021 Jan;121:104965. doi: 10.1016/j.archoralbio.2020.104965. Epub 2020 Nov 2.
Clarifying the discrepancy between frequently high oxalate concentrations present in saliva, but negligible amounts of calcium oxalate deposits found on oral surfaces.
Studying the calcium oxalate concentration range that can lead to heterogeneous crystallization in the oral cavity. a) Minimum: calcium oxalate monohydrate (COM) seed crystals were pre-grown ([Ca] = [CO] = 1 mM, 30 min, 37 °C), and then re-immersed for ≥6 h to find the solubility equilibrium concentration (no growth, no dissolution). The concentrations tested were [Ca]/[CO] : 0.055/0.050, 0.060/0.055, 0.070/0.065 and 0.080/0.075 mM. Supersaturations were calculated via the Debye-Hückel-theory and COM morphologies examined by scanning electron microscopy (SEM). b) Maximum (at the heterogeneous/homogeneous crystallization equilibrium): hydroxyapatite (HA) seed crystals were used to heterogeneously crystallize COM (37 °C, 24 h), using oxalate concentrations between 0.2 and 0.5 mM and calcium concentrations of 0.5 mM. COM-forming oxalate consumption was spectroscopically examined; COM precipitates were investigated by SEM; and HA identity was confirmed by X-ray analysis.
Within the concentration range of [Ca]/[CO]:0.060/0.055 mM (minimum) and [Ca]/[CO]:0.50/0.25 mM (maximum) COM precipitates heterogeneously. In terms of mass, this corresponds to a range of 8.04-36.53 mg/l (daily) or an average of 14.32 mg COM (mimicking e.g. plaque mineralization). Higher concentrations react homogeneously (mimicking precipitation within saliva).
In vivo, only ∼0.05 % oxalate present in saliva reacts with oral surfaces daily, corresponding to ∼0.0665 μmol/l or ∼9.72 μg COM per day. Calcium-consuming calcium phosphate formation and phosphoproteins such as statherin obviously hinder intraoral COM formation.
阐明唾液中经常存在高浓度草酸盐与口腔表面发现的草酸盐钙沉积量可忽略之间的差异。
研究可导致口腔内异质结晶的草酸盐钙浓度范围。a) 最小值：预先生长草酸钙一水合物（COM）晶种晶体（[Ca]=[CO]=1mM，30 分钟，37°C），然后再重新浸入至少 6 小时以找到溶解度平衡浓度（无生长，无溶解）。测试的浓度为[Ca]/[CO]：0.055/0.050、0.060/0.055、0.070/0.065 和 0.080/0.075mM。通过德拜-休克尔理论计算过饱和度，并用扫描电子显微镜（SEM）检查 COM 形态。b) 最大值（在异质/同质结晶平衡时）：使用羟磷灰石（HA）晶种使 COM 异质结晶（37°C，24 小时），使用 0.2 至 0.5mM 的草酸盐浓度和 0.5mM 的钙浓度。用光谱法检查形成 COM 的草酸盐消耗；用 SEM 研究 COM 沉淀物；用 X 射线分析确认 HA 身份。
在[Ca]/[CO]：0.060/0.055mM（最小值）和[Ca]/[CO]：0.50/0.25mM（最大值）范围内，COM 沉淀物异质沉淀。就质量而言，这相当于 8.04-36.53mg/l（每日）或 14.32mg COM 的平均值（模拟例如菌斑矿化）。更高的浓度则均匀反应（模拟唾液中的沉淀）。
在体内，只有唾液中存在的约 0.05%的草酸盐每天与口腔表面反应，相当于每天 0.0665μmol/l 或 9.72μg COM。消耗钙的磷酸钙形成和唾液蛋白如唾液蛋白明显阻碍口腔内 COM 的形成。
