Andrei Agop

By Lucia Marin Biolan, Andrei Bedros Agop and Doriana Forna

The deposition of hydroxyapatite thin films has become a topic of interest in medical applications. This dental film applied on the surface of the tooth may act as a highly resistant and flexible artificial enamel, protecting teeth and removing tooth sensitivity. Other possibilities include whitening and coating enamel-deficient structures. We obtained this flexible film of hydroxyapatite using laser ablation. The plasma plumes were generated by an Nd:YAG nanosecond laser in a vacuum chamber. We used the pulsed laser deposition (PLD) technique and conducted investigations using optical emission spectroscopy (OES), laser-induced breakdown spectroscopy (LIBS), and Raman spectroscopy. Initially, a thin film of HA was deposited on a soluble substrate and heated, followed by immersion into pure water to dissolve the substrates. The originality of our approach consists in the fact that the flexible HA film can be obtained in pure state, because it grows without a substrate, using just a base and lateral supports between, on which it will grow vertically. In order to verify the compatibility and the “stickiness” of HA on the teeth, we chose to grow the film between the roots of a tooth. In this case, besides the film, we also obtained HA microfibers. We tried to bind the film on an extracted tooth. A protocol must be established in order to allow the bonding of the film to the surface of the tooth, knowing that contaminants such as saliva or sulcular fluid increase bonding strength to enamel or dentin. We realized an efficient bonding as HA absorbs protein, the mineral also participates in this ionic exchange, and we strengthened the tooth structure. The main purpose of our research is to rebuild the dentine layer or enamel and close the dental channels. Our experiments led to the creation of an HA foil that has the role of protecting teeth against cariogenic bacteria and could even have cosmetic effects by teeth whitening. This dental plaster acts as an artificial HA enamel, very resistant and flexible, protecting the tooth and eliminating dental sensitivity. Being very thin, it is invisible once applied on teeth and can be observed only by examination under a strong light.

Part of the book: High Energy and Short Pulse Lasers

By Maricel Agop, Decebal Vasincu, Daniel Timofte, Elena Simona Bacaita, Andrei Agop and Stefan Andrei Irimiciuc

In the present chapter, we show that the use of the nondifferentiable mathematical procedures, developed in the Scale Relativity Theory with constant arbitrary fractal dimension, simplifies very much the dynamics analyses in the case of complex systems. By applying such a procedure to various complex systems dynamics (biological structures, ablation or discharge plasmas, etc.), we are able to observe that it starts from a steady (oscillating state) and as the external factor is varied the system undergoes significant changes. The systems evolve asymptotically through various transition, toward a chaotic regime (like bifurcations or intermittencies), but never reaching it. Another important reveal from the study of the system’s dynamics was the presence of various steady states depending on the resolution scale at which the theoretical investigations are performed.

Part of the book: Fractal Analysis

By Stefan Andrei Irimiciuc, Norina Forna, Andrei Agop, Maricel Agop, Stefan Toma and Doriana Forna Agop

Understanding the underline fundamental mechanism behind experimental and industrial technologies embodies one of the foundations of the advances and tailoring new materials. With the pulsed laser deposition being one of the key techniques for obtaining complex biocompatible materials with controllable stoichiometry, there is need for experimental and theoretical advancements towards understanding the dynamics of multi component plasmas. Here we investigate the laser ablation process on Cu-Mn-Al and Fe-Mn-Si by means of space-and time-resolved optical emission spectroscopy and fast camera imaging. In a fractal paradigm the space–time homographic transformations were correlated with the global dynamics of the ablation plasmas.

Part of the book: Practical Applications of Laser Ablation