Dentinogenesis and the calciotraumatic response to the injection of lead or fluoride ions.

A number of ions can disturb the formation of dentine resulting in a calciotraumatic response. The calciotraumatic response following the injection of sodium fluoride was investigated using backscattered electron imaging in the scanning electron microscope and compared with the response to lead acetate. With fluoride, there was formation of a hypermineralized band succeeded by a relatively hypomineralized band, but with lead acetate, only a hypomineralized band was produced. However, there were some differences in the response between the labial and lingual dentine with both ions. In the labial dentine following injection of sodium fluoride, the onset of hypermineralization was less abrupt than in the lingual dentine. Furthermore, the transition from hypermineralization to relative hypomineralization was more abrupt in the labial dentine. Sometimes there was an increased thickness of labial dentine between the hypermineralized layers towards the apex of the tooth and this dentine was less homogeneously mineralized. Normal incremental lines were occasionally seen both labially and lingually. Lead acetate produced a more severe disruption of dentine formation labially than lingually. These differences in response may be related to the pattern of mineralization labially and lingually and to the systemic effects following the injection of sodium fluoride.