Ultrastructural Change of Enamel Exposed to a Normal Pulsed IMd-YAG Laser

Abstract

The ultrastructural changes of the enamel surface occurring due to normal pulsed Nd-YAG laser irradiation were examined by scanning electron microscopy. The melted and recrystallized enamel in the lased enamel surface was observed. A coalescence of enamel globules was caused by 10 pulses of laser irradiation. In the case of excessively repeated irradiation (3 applications of 10 pulses), new particles of enamel crystal were produced which had a larger size than the original and measured about 0.2–1.0 μm in diameter. In some portions, large-sized hexagonal particles were also observed. In fractured surfaces of enamel, the shapes of the new particles of enamel crystal varied and included granules, needles and columns. The column structure had various appearances such as being well packed, along with piled granules and hollow columns, as well as having intercrystal or intracrystal voids. It was suggested that a distinctive polygonal column shape of more than 2 μm in length might be formed in the process of homogeneous melting at high temperatures followed by uniform cooling and contraction. The recrystallized layer demonstrated significant acid resistance but was a little fragile. These results greatly support the hypothesis that a larger crystal size may cause acid resistance in enamel exposed to pulsed laser.

Protective Effect of Adhesive Systems associated with Neodymium-doped Yttrium Aluminum Garnet Laser on Enamel Erosive/Abrasive Wear

“…Its effectiveness can be related to its ability to decrease the enamel permeability, reducing the diffusion of acids during the erosive challenges, minimizing thereby the demineralization. 13 In addition, the laser irradiation raises the surface temperature to 650°C, favoring the formation of pyrophosphate, which can reduce the dissolution of hydroxyapatite, replacing the apatite carbonate which is more soluble for hydroxyapatite or fluorapatite in the presence of fluoride. 11 On the contrary, the results in the literature regarding its effectiveness are conflicting.…”

“…This modified surface shows a reduction of interprismatic areas, and consequently, less acid diffusion, increasing the demineralization resistance. 13 Furthermore, laser irradiation promotes the formation of pyrophosphate, which can reduce the dissolution of hydroxyapatite, replacing the more soluble apatite carbonate for hydroxyapatite or fluorapatite in the presence of fluoride.…”

Conventional and experimental treatments for pit and fissure sealing associated with ND:YAG laser

“…In view of the results presented, irradiation with Nd:YAG laser was the most effective preventive treatment, showing the lowest mean depth of caries formed values, which differed statistically from the values of the control group, as presented in Tables 1 and 2. This may be explained by the interaction of laser with dental tissue, because irradiation with Nd:YAG laser is absorbed by the hydroxyapatite and converted into heat, promoting the melting and resolidification of the enamel structure. The irradiated surface presented reduced interprismatic spaces, and consequently, less diffusion of acids, reducing demineralization of the superficial enamel [33,34]. Furthermore, irradiation with laser favored the formation of pyrophosphate, which may reduce the dissolution of hydroxyapatite, replacing the carbonate of more soluble apatite with hydroxyapatite, or fluorapatite in the presence of fluoride [35,36].…”

“…The authors expected that hydroxyapatite would help with protection against the action of caries, and in view of the expectations, they found that group HA, with or without association with laser, also presented a behavior similar to those of conventional treatments in regard to protection against the development of caries. With the association of laser irradiation, the authors expected melting and fusion of the material and enamel structure and later solidification, thus diminishing enamel permeability and protecting the surface against the action of caries [33,34]. Because this was an innovative, hardly explored methodology, no similar studies were found to make comparison with the literature possible.…”

Impact of welding the dental enamel walls of the fissure system using semiconductor laser: In-Vitro study

“…Tagomori et al [9] found that the irradiated enamel surfaces dependably show higher surface roughness in comparison with the untreated ones. Also, Marquez et al noticed that the lased surface usually displays 3 layers: un-changed enamel crystals in the internal side of the tooth, fused crystals in the intermediate area and hexagonal hydroxyapatite columns, isolated by voids and micro cracks in the outer surface [10].…”