Simulated occlusal adjustments and their effects on zirconia and antagonist artificial enamel

Abstract

PURPOSE The aim of this study was to evaluate the effect of occlusal adjustments on the surface roughness of yttria-tetragonal zirconia polycrystal (Y-TZP) and wear of opposing artificial enamel. MATERIALS AND METHODS Twenty-five Y-TZP slabs from each brand (Lava, 3M and Bruxzir, Glidewell Laboratories) with different surface conditions (Control polished - CPZ; Polished/ground - GRZ; Polished/ground/repolished - RPZ; Glazed - GZ; Porcelain-veneered - PVZ; n=5) were abraded (500,000 cycles, 80 N) against artificial enamel (6 mm diameter steatite). Y-TZP roughness (in µm) before and after chewing simulation (CS) and antagonist steatite volume loss (in mm 3 ) were evaluated using a contact surface profilometer. Y-TZP roughness was analyzed by three-way analysis of variance (ANOVA) and teatite wear by two-way ANOVA and Tukey Honest Difference (HSD) ( P =.05). RESULTS There was no effect of Y-TZP brand on surface roughness ( P =.216) and steatite loss ( P =.064). A significant interaction effect ( P <.001) between surface condition and CS on Y-TZP roughness was observed. GZ specimens showed higher roughness after CS (before CS − 3.7 ± 1.8 µm; after CS − 13.54 ± 3.11 µm), with partial removal of the glaze layer. Indenters abraded against CPZ (0.09 ± 0.03 mm 3 ) were worn more than those abraded against PVZ (0.02 ± 0.01 mm 3 ) and GZ (0.02 ± 0.01 mm 3 ). Higher wear caused by direct abrasion against zirconia was confirmed by SEM. CONCLUSION Polishing with an intraoral polishing system did not reduce the roughness of zirconia. Wear of the opposing artificial enamel was affected by the material on the surface rather than the finishing technique applied, indicating that polished zirconia is more deleterious to artificial enamel than are glazed and porcelain-veneered restorations.

Effect of artificial aging on optical properties and crystalline structure of high‐translucency zirconia

“…In this study, it was demonstrated that there was no effect of any aging protocol on the surface roughness of the monolithic zirconia surface. Supporting these findings, a study found no changes in the surface roughness of polished HT zirconia after 500,000 chewing cycles against artificial enamel 29 . Another study reported no differences in the surface roughness of polished zirconia after 1.2 million chewing cycles against steatite combined with 10,000 thermocycles 51 .…”

“…The long‐term stability of Y‐PSZ materials in the oral environment is a concern, and the correlation between HA and in vivo oral challenges is not well established, 26,27 means that data obtained from in vitro studies might not be relevant when considering challenges presented to the material in the oral cavity. There is currently a lack of studies evaluating the effect of temperature, pH changes, and humidity, as well as other factors, like mastication, on the properties of zirconia intended for dental application 28–30 . Therefore, the objective of this study was to compare the effect of HA and a novel aging model simulating clinical challenges on the optical and surface properties of high translucency (HT) monolithic zirconia.…”

Ciencia y evolución del dióxido de zirconio, de la prioridad mecánica a la necesidad estética

“…El desgaste superfi cial de las cerámicas al darse por un mecanismo de microfractura, difi eren de las resinas que se desgastan a través de abrasión por fatiga (14), según algunos investigadores la resistencia a la fractura y la rugosidad de superfi cie son las razones principales para el desgaste (12), más no los valores de dureza (7,13); Alfrisany et al, encuentran que las superfi cies de zirconia causan menos desgaste a las superfi cies de esmalte antagonista en comparación al ocasionado por cerámica feldespática, pero recomienda que las superfi cies de zirconia no deben ser glaseadas, ya que, cuando comparan las superfi cies solo con acabado y pulido ocasionan menos desgaste que cuando están glaseadas (20), aunque otros estudios muestran que no hay diferencia estadísticamente signifi cativa entre ambos (8,12); cabe mencionar que si bien el glaseado es un método para brindar a la superfi cie de la restauración un alto brillo, las capas pueden desgastarse dentro de los 6 meses posteriores a la restauración. Para otros autores, el procedimiento de pulido, no agrega ninguna capa a la superfi cie de dicha restauración, entonces en términos de corto plazo la superfi cie glaseada lucirá como una superfi cie sin acabado ni pulido, ocasionando mayores desgastes (11).…”

Wear of dental ceramics

“…For that, the tests can be performed in distilled water at room temperature [50], in 33% glycerin lubricant [58] or in those two combined [59]. The literature also reports the use of normal saline emulsion [60] or artificial saliva [61,62].…”