Effetto di pH acido sull’usura di smalto naturale opposto a materiali monolitici CAD-CAM

ABSTRACT TITLE: Two-body wear of natural enamel against CAD-CAM monolithic materials with acidic pH. Purpose: The aim of this in vitro study was to evaluate the effect of different acidic mediums on wear rate and pattern of CAD-CAM monolithic materials and enamel. The null hypothesis was that different pH do not influence the wear of neither CAD-CAM materials (1) neither sound enamel (2). Materials and Methods: Ninety-six rectangular specimens were prepared using different CAD-CAM monolithic materials: nanohybrid composite (Grandio Blocks, Voco), resin-infiltrated ceramic (Cerasmart, GC), lithium disilicate (E-Max, Ivoclar), cubic zirconia (Katana STML, Noritake). After storage in distilled water at 37 °C for 2 days, the specimens were tested with a chewing machine with a sound intact upper premolar as antagonist (80N loads, 100.000 cycles). Testing was performed using water, Coca-cola, Red Bull as abrasive medium. Wear analysis of the CAD-CAM materials and the sound enamel was performed using a 3D profilometer and analyzed with two-way analysis of variance and post-hoc pairwise comparison procedures. Worn surfaces were examined with scanning electron microscopy. Results: Statistical analysis of the sound enamel wear loss after simulated chewing cycles identified a significant influence of factor “material” (p=0.00001), of the factor “solution” (p=0.0015) and their interactions (p=0.0193). The lower wear rate was observed on zirconia < lithium disilicate < hybrid ceramic < CAD-CAM composite. Coca-Cola and Red Bull equally induced a significantly implemented volumetric wear than water. A correlation between enamel and cubic zirconia wear pattern was observed on SEM images. Conclusion: The acidic environment significantly increase the enamel wear when opposing to zirconia, while the low pH did not affect the wear of the materials. Thus, the null hypothesis that CAD-CAM monolithic materials do not show neither a wear rate (1) neither superficial roughness (2) influenced by acidic beverages with an enamel antagonist, are partially accepted.