Atomic force microscopy analysis of the surface alterations of enamel, dentin, composite and ceramic materials exposed to low oral pH in GERD.

Dental erosion is a significant topic in medical literature, both for gastroenterology and dental medicine. Dental structure loss has a psychosocial and functional significance. The pathogenesis of dental erosion in patients diagnosed with gastroesophageal reflux disease (GERD) characterized by the presence of an acidic oral environment after reflux episodes, is not well understood. The present study was designed to observe the effect of low oral pH in time on natural surfaces including enamel and dentine, but also on materials used in treating these dental destructions such as composites and ceramics. The acidic oral environment was estimated in relation to salivary pH. In the dental laboratory, 5-mm2 and 1-mm composite pieces of thick enamel, dentine, Emax Ceramic and Nexco Ivoclar were cut in order to be analyzed using atomic force microscopy (AFM) and to observe the surface alterations. Gastric acid was collected and mixed with saliva until a pH value of 6.0 was obtained, in which the pieces were immersed for 24, 120, 240 h. Roughness of each surface was calculated at a microstructure and nanostructure level. The results showed significant alterations in enamel and dentine exposed to a lower pH level beginning even at a short immersion time, in comparison with composites and ceramics which had no alterations. In conclusion, multidisciplinary attention should be given to detect and manage acidity of the oral cavity caused by GERD, in order to prevent dental erosion.

Alexander von Humboldt's contribution to the biomedical sciences and scientific illustration. In honor of his 250th anniversary.

Alexander von Humboldt (1769-1859) is one of the most prominent Germans. His multidisciplinary activity set standards to science at the beginning of modern era. His personality is celebrated worldwide. The Alexander von Humboldt Foundation in Bonn is still preserving his memory and endorsing research in all the fields. This paper is a historical sketch presenting his contributions to the development of medical sciences and also to the progress of scientific illustrations. We also introduce personalities of the Cluj-Napoca medical school who were fellows of the Alexander von Humboldt Foundation.