Analisi dei metodi di mantenimento dei margini di chiusura nelle protesi senza struttura in metallo

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Objectives We used scanning electron microscopy (SEM) to comparatively evaluate damage to the finish line of metal-free dental crowns produced by dental hygiene maintenance procedures performed with different types of manual and mechanical instruments. Materials and methods Twenty-one extracted teeth (all in good condition) with chamfered margins were divided into seven identical groups. The three teeth in each group were fitted with metal-free crowns (1 zirconium oxide, 1 aluminum oxide, and 1 ceramic) and treated with the following: steel-tipped ultrasound (US) device ( group 1); polyether ether ketone (Peek)-tipped US device ( group 2; steel scaler ( group 3); polycarbonate curette ( group 4); red ring handpiece with soft rubber tip ( group 5); prophylaxis paste applied with cups on a contra-angle handpiece ( group 6); soft glycine-powder air polishing ( group 7). All instruments were used by the same operator under standard conditions. After the completion of decontamination protocols, the crowns were examined with SEM. The three teeth of group 1 were also subjected to SEM before the treatment (as an untreated control group). Results Compared with their respective untreated controls, the treated crowns all displayed surface modifications. Those treated with the steel-tipped US device or the steel scaler displayed sulci and scratches on the surface of the area inspected. Only light scratches were seen on the crowns treated with the Peek-tipped US device. In the groups treated with devices designed to remove plaque only, no appreciable changes were observed. In group 7 (treated with soft glycine air polishing), the aluminum and ceramic crowns displayed tiny “craters” a few microns in diameter (magnification 1000×), but no significant changes were observed in the zirconium crown from this group. Conclusions The results of this study suggest that deplaquing alone may be the method of choice in this setting. Of the methods tested, it was the only one that did not produce morphological or structural damage to the metal-free crowns. However, if tartar has to be removed from the finish line of the crown, the only solution is the Peek-tipped US device, which proved to be the most effective and least aggressive of the methods tested.