Jh. Meurman et al., TRANSFORMATION OF HYDROXYAPATITE TO FLUORAPATITE BY IRRADIATION WITH HIGH-ENERGY CO2-LASER, Caries research, 31(5), 1997, pp. 397-400
High-energy laser irradiation has been shown to cause crystalline tran
sformations in apatites, which may lead to the formation of tricalcium
phosphates with a resulting decrease in acid resistance. Depending on
the nature and energy density of laser irradiation used, however, an
increase of acid resistance of dental enamel has also been reported af
ter laser irradiation. The aim of the present study was to investigate
the phase transformation of hydroxyapatite (HA) to fluorapatite (FA)
in a model system that incorporates sodium fluoride (NaF) into apatite
structure by using laser irradiation. A CO2 laser was used at energy
densities ranging from 21 to 500 J/cm(2). Synthetic HA mixed with NaF
(10:1) was the target of laser irradiation. The crystalline structures
were then investigated using X-ray diffraction analysis. The results
showed that a phase transformation of HA to FA could be realized, and
that the threshold energy density needed was 38 J/cm(2). Not only is t
he finding crystallographically important, but it also opens new persp
ectives for future research regarding the development of laser technol
ogy for clinical purposes.