170 



ADVENTURES IX RADIOISOTOPE RESEARCH 



Table 2. Analyses of Dentine of Human Teeth 

 (% in Dry Dentine) 



Slight hypoplasiii Severe hypoplasia 



Ash 

 Ca . 

 P .. 

 CO2 

 Mg 

 CI . 



Bowes and Murray give the following average figures for the compo- 

 sition of the enamel: 



Table 3. Analyses of Enamel of Human Teet 



H 



Slight liyiioplasia Severe h^-poplasia 



Ash 

 Ca . 

 P .. 



95.38 

 37.07 

 17.22 



94.67 

 35.81 

 17.72 



Slight hypoplasia Severe hypoplasia 



CO, 

 Mg" 

 CI . 

 Fe 



1.952 

 0.464 

 0.3 

 0.25 



2.434 

 0.477 

 0.19 



As is seen from the above figures phosphorus is the second most 

 abundant mineral constituent of the teeth, its share in the dentine 

 amounting to 13.5 — 13.8% and in the enamel to 17.2 — 17.7% while 

 in the dentine ash 18.2—18.4% in that of the enamel 18.4 — 19.4% 

 w^ere found. In the ash of the incisors of rats an even higher phosphorus 

 content of 20% was found. Bone ash contains an only slightly lower 

 amount of phosphorus than tooth ash, the values found varying betw^een 

 17.9 and 18.5%. 



In distinction to the chief constituents of the teeth the minor consti- 

 tuents vary within wide limits. The composition of the mineral consti- 

 tuents of the teeth corresponds approximately to a mixed crystal of the 

 minerals hydroxide-apatite and carbonate apatite, the former predomi- 

 nating strongly. As in apatite minerals the OH ions of the tooth apatite 

 can be replaced to a certain extent by F ions for example. The degree 

 of replacement of 0H~ by F^, will depend primarily on the fluorine 

 content of the blood during the development period of the tooth and 

 also on that which circulates in the fully calcified tooth. The fluorine 



