Laser-induced compositional changes on enamel: a FT-Raman study.
Preventive effects of lasers on enamel caries have been documented in the past few decades. However, its specific mechanism remains uncertain.


OBJECTIVE
To evaluate the laser-induced change of enamel compositions, including carbonate and organic matters using Fourier-transform Raman spectroscopy (FT-Raman).


METHODS
Twelve windows (1 mm x 1 mm), created on six defect-free primary incisors, were characterized by FT-Raman microscopy (1024 nm) before and after Er:YAG laser treatment (Fidelis) with 5.1 J/cm(2)-2 Hz-5s. To assess the statistical significance of laser effects, Raman peaks assigned to nu(1) phosphate, type-A/B carbonates, and organic matters were evaluated with the paired-samples t-test.


RESULTS
The standardized intensity of type B carbonate decreased significantly from 0.117 to 0.106 (p=0.029), whereas the standardized intensity of carbonate A remained unchanged (p=0.467). Related to organic matters, the standardized intensity of peaks at 2940 cm(-1) and in the ranges of 1200-1600 cm(-1) decreased significantly, with p=0.005 and p<0.001, respectively. Revealing enamel crystallinity, the bandwidth of nu(1) phosphate on lased surfaces appeared to be unaltered after laser treatment (p=0.477).


CONCLUSIONS
Laser treatment may provide caries-preventive effect on enamel through reduction of carbonate and modification of organic matters.
Liu
Yuanyuan
Y
Department of Preventive Dentistry, Faculty of Dentistry, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119074, Republic of Singapore.
Hsu
Chin-Ying Stephen
CY
D000538:Aluminum Silicates; D000577:Amides / Q000032:analysis; D002244:Carbon / Q000032:analysis; D002254:Carbonates / Q000032:analysis; D003461:Crystallography; D003743:Dental Enamel / Q000737:chemistry / Q000528:radiation effects*; D004871:Erbium; D006801:Humans; D006860:Hydrogen Bonding; D007834:Lasers; D009930:Organic Chemicals / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D015019:Yttrium
D000538:Aluminum Silicates; D000577:Amides; D002254:Carbonates; D009930:Organic Chemicals; D010710:Phosphates; D015019:Yttrium; D002244:Carbon; D004871:Erbium