Dahllite formation

The nature of mineral phases present in bone, dentin, enamel and other phosphatic tissues, and their mode of formation have been subjects of lively discussions among health scientists and crystallographers. Bioscientists most commonly accept the viewpoint that the inorganic phase of bones or teeth is principally hydroxyapatite, Caio(P04)6(OH)2, and deviation in Ca/P ratio from common hydroxyapatite (Ca/P = 1.667) observed in mineralized tissues is explained by the presence of amorphous phosphates. In contrast, many crystallographers favor the idea of carbonate apatite, i.e. dahllite, as the major crystalline phase in biophosphates and they doubt the existence of amorphous phases. The topic has been reviewed14,15,22,28, 37,44,47,348-358) no common consent has yet been reached. In the following an attempt is made to at least coordinate the controversial findings. 

In vitro systems have been studied extensively and the common enzyme, carbonic anhydrase, has been found to function as a catalyst in the precipitation of dahllite (McConnell et al., 1961), whereas other substances act as inhibitors to this precipitation. Included in the latter category are pyrophosphate and polyphosphate ions (Fleisch and Neuman, 1961), sulfanilamide (McConnell et al., 1961) and the Mg ion, which tends to favor formation of whitlockite (Trautz et al., 1964). One of the most interesting experiments is the formation of dahllite as an intracellular product of bacteria, which will be discussed later. 

In vitro experiments (McConnell et al., 1961) indicated that a substance which was crystallochemically comparable with oral calculus could be produced both from pooled human saliva and from a calcifiable synthetic solution to which a few mg 1 of carbonic anhydrase had been added. When a few mg 1" of sulfanilamide was added also, such a precipitate did not form, cleeirly indicating an interrelation between the formation of dahllite... 

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