ABSTRACT
The purpose of this study was to investigate the effect of laser irradiation on the enamel surface spectroscopically. Polished bovine enamel surface was irradiated with an Er:YAG laser apparatus and chemically analyzed using X-ray photoelectron spectroscopy (XPS). XPS detected core electron peaks such as carbon (C 1s) and nitrogen (N 1s), as well as calcium (Ca 2s, Ca 2p, Ca 3s, Ca 3p), phosphorous (P 2s, P 2p), and oxygen (O 1s), from the control enamel surface. After irradiation, XPS revealed that the intensity of C 1s peak slightly decreased while that of N 1s diminished below the detection limit. Detailed C 1s narrow scan spectrum of the Er:YAG laser-irradiated enamel surface showed that C-O/C-N, C = O/-CON=, -COO-, and CO,3(2-) components, attributed to the specific composition of enamel and any common carbon contamination in surplus, relatively decreased. The binding energies of Ca 2p and P 2p, delta (Ca 2p, P 2p), and the Ca/P ratio of lased enamel were found to be different from those of non-lased enamel. It was also shown that Er:YAG laser ablation caused surface alterations to the apatitic inorganic components of tooth tissue.
Subject(s)
Dental Enamel/chemistry , Dental Enamel/radiation effects , Lasers , Animals , Cattle , Electron Probe Microanalysis , Erbium , Infrared Rays , Surface Properties/radiation effectsABSTRACT
Each dental adhesive contains a specific functional monomer that determines its actual adhesive performance to tooth tissue. 4-methacryloxyethyl trimellitic acid (4-MET) is well-known as one of the functional monomers mostly available and consequently widely used in commercial adhesives. We therefore characterized the chemical interaction of 4-MET with hydroxyapatite (HAp) using X-ray Photoelectron Spectroscopy (XPS). XPS revealed that the peak representing -COO- of 4-MET shifted to a lower binding energy, when 4-MET was adsorbed onto HAp. Deconvolution of this shifted peak disclosed two components with a peak representing unreacted carboxyl groups and ester groups, and a peak suggesting chemical bonding of other carboxyl groups to Ca of HAp. XPS spectra of HAp treated with 4-MET also disclosed the surface to be enriched in calcium and decreased in phosphorus, indicating that phosphorus was extracted at a relatively higher rate than calcium. It can thus be concluded that true chemical bonding of 4-MET with calcium present in HAp occurred, as it was proven using XPS.
