ANALYSIS OF THE WHITENING SYSTEMS INFLUENCE ON THE TOOTH ENAMEL AT THE MICRO AND NANOSTRUCTURAL LEVEL

Abstract

Correction of the discolored teeth hard tissues is an important issue at modern aesthetic dentistry nowadays. In global dental practice, more and more attention is being paid to the development of methods that ensure the satisfaction of the aesthetic needs of patients. Purpose. To establish the effect of whitening agents at the micro and nanostructural level, to discover the whitening effect on the morphology of the tooth enamel surfaces (in vitro) and to determine the most effective and safe methods of teeth whitening procedures. Materials and methods. All our studies were conducted on permanent teeth that were extracted for orthodontic indications at patients aged from 18 to 39 years. Experimental groups were created, each of which consisted of 10 tooth samples: normal samples (intact teeth); teeth whitening using Opalescence 35 % gel /30 min / 7 times; professional dental hygiene, Air Flow, teeth whitening using Beyond system 35 % H2O2 gel / 12 min + light/ 3 times /remineralization therapy. We have also used SPM methods, such as atomic force microscopy (AFM) and the surface of the samples has been characterized at the macro level by means of digital optical microscopy using a Carl Zeiss NU2E microscope. Results. Typical optical microphotographs of the enamel surfaces of the examined teeth samples processed by the Opalescence technique has shown us affected areas of hundreds microns in size with a broken cellular structure. We have not similar features on the surfaces of teeth bleached with a help of the Beyond system. As follows from the AFM images and the corresponding nanorelief height distributions, the influence of the Opalescence procedure on the enamel relief structure is the most significant. The width of the relief height distribution is the largest and the image contains a lot of nano concavities and a pronounced grain structure. The measured corresponding roughness values of the reliefs of these enamel samples are 6, 16 and 12 nm, for the intact surface and the surfaces treated by the Opalescence and Beyond techniques, respectively. A statistical analysis of the nano grain sizes of the mentioned reliefs confirms the following values: 52±17 nm, 109±31 nm and 79±25 nm. Cross-correlation analysis of grain size samples of treated surfaces (t-test) confirms their statistical significance. Thus, based on the above results of the AFM measurements, it can be stated that whitening procedures definitely modify the nanostructure of the topography of the tooth enamel surface. The roughness of the surface can increase by two or more times and be accompanied by changes in the graininess of the surface of the tooth enamel prisms. The proposed method of evaluating the effect of bleaching on the nanostructure of the enamel relief allows us to effectively evaluate the effect of reagents and choose optimal bleaching agents. Conclusions. 1. Atomic force microscopy is an effective method of detecting the impact of modern bleaching procedures on the nanostructure of enamel surface relief. At the same time, reproducible and statistically significant results can be obtained during research in clearly defined areas of teeth, using fragments of the same sample. 2. Analyzing the microstructure of the enamel at our studies using the AFM, we have found that the professional teeth whitening procedure with a help of Beyond 35 % H2O2 gel, 3 times for 12 minutes with the usage of a lamp and carrying out remineralization therapy after procedure significantly less has destroyed the upper layers of enamel prisms (40-100 nm) in comparison with the Opalescence technique and the best aesthetic effect has been achieved.