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Calcium chelating agents, such as ethylenediaminetetraacetate are toxic to urothelium. Their capacity to form complexes with calcium ions, which is the basis for their chemolytical effectiveness, also determines their toxicity. A decrease of chemolytical effectiveness by prior saturation of the chelator with Ca2+ or by lowering the pH to levels unfavourable for calcium binding significantly diminishes tissue injury. Exchange of Mg2+ ions does not, however, diminish tissue damage. The clinical use of calcium ligands is therefore unsafe.

Solutions, based on calcium chelating agents, with excellent prospects as litholytic agents in vitro were tested on toxicity to the mucosa of the bladder of the rat. The following compounds were tested at a concentration of 12.5 mM., buffered with triethanolamine 0.2 M at pH 8 and 8.5: ethylenediaminetetra acetic acid with as cation H2+, Li+, Na+, K+, and Cs+, trans-cyclohexane-1.2 diaminetetra acetic acid (cations H+, Na+, K+), diethylenetriamine penta acetate (cations H+, Na+, K+), disodiumethyleneglycol-bis (2 aminoethyl) tetra acetic acid and disodium hydroxyethylethylenediamine tetra acetate. All agents were found to be very noxious to the bladder mucosa of the rat and are unlikely to be safe for clinical use.

Although microradiography is considered to provide qualitative as well as quantitative information about the demineralization process of root surfaces, there are several difficulties, especially when dealing with an erosive lesion type. The present study proposes a new approach to microradiographic evaluation which can solve some of the problems. A procedure for determining the position of the original surface of any erosive lesion site is presented, thereby tracking this position with an accuracy of 23 pm. Biologic variations and processing related factors, resulting in distorted surface as well as mineral profiles can be adjusted by normalizing the lesion profile with respect to the mineral profile of adjacent border fields. A routine is described by which the former is related to its pre-demineralization status.