Rettifica e lucidatura alla poltrona della zirconia: rilevanza clinica e suggerimenti

OBJECTIVES The aim of this study is to provide an updated overview on the clinical rel evance and protocols of chairside “grinding” and “polishing” maneu vers of monolithic zirconia prosthet ic restorations based on the data currently available in the literature. MATERIALS AND METHODS The search was conducted using the PubMed/Medline database. The inclusion criteria led to the analysis of all the material selected through the combination of the fol lowing key terms: “monolithic zir conia” AND “chairside” OR “intra oral” OR “clinical” AND “adjust ment” OR “grinding” OR “finishing” OR “polishing”; “monolithic zirco nia” AND “surface roughness”; “monolithic zirconia” AND “wear”. The exclusion criteria do not allow us to examine case reports, re views and works that do not focus on the topic of chairside adjust ments of monolithic zirconia, in tra-oral “grinding” and “polishing” protocols of monolithic zirconia and behavior in terms of bacterial adhesion, mechanical perfor mance and wear of the restoration being treated. Only studies in English were ex amined. RESULTS The latest developments in CAD/CAM technology have made monolithic zirconia restorations an advantageous solution in pros thetic cases with advanced me chanical and aesthetic needs. It is routine for monolithic zirconia res torations to require chairside clini cal adjustments. These maneu vers usually involve the “grinding” and “polishing” phases. The available data shows that the “grinding” phase determines de fects and “microcracks” in the zir conia with repercussions in terms of surface roughness, mechanical resistance, wear, plaque accumu lation, optical properties of the monolithic zirconia restoration. “Polishing” is able to restore the surface characteristics after “grinding” and, unlike glazing, re store the mechanical resistance and improve the wear character istics of the zirconia. “Polishing” must aim for surface roughness (Ra) values of 0.2 µm. CONCLUSIONS After chairside adjustments of monolithic zirconia restorations, applying a “polishing” protocol dedicated to zirconia is currently the first choice for the clinician. The “grinding” maneuvers of the zirconia, together with the in crease in wear and accumulation of biofilm, can lead to a decay of the aesthetic and mechanical properties of the monolithic resto ration to a variable extent based on the crystallographic phases present in the structure. Proper “polishing” can effectively restore surface characteristics af ter “grinding”, prevent crack prop agation, improve wear character istics, all factors that affect the longitudinal prognosis of the res toration. The operating protocols for the dentist include instruments with mandatory sequences with the aim of obtaining the most predict able results. However, these pro cedures require updated proto cols for more advanced “zirco nia-based” materials. CLINICAL SIGNIFICANCE The topic of chairside adjustments of monolithic zirconia restorations is highly topical both due to the relevance it potentially exerts in terms of success of the prosthetic restoration and by virtue of the re cent introduction of new “zirco nia-based” materials which have extended the indications for “full-contour” restorations. Chairside clinical adjustments conducted with correct “grinding” and “polishing” phases contribute to the favorable longitudinal prog nosis of the monolithic zirconia prosthetic restoration.