1. A 42 year-old female patient, unsatisfied by the esthetics of her smile, asked for the rehabilitation of the maxillary incisors by means of fixed prostheses, substituting 4 previous metal-ceramic single crowns.
2-6. After the study of the case and the routinary clinical and laboratory analyses, the previous restorations were removed and the preparations of the abutment teeth were revised, making 1 mm circumferential chamfers.
7. The periodontal tissues were conditioned to a healthy state using a temporary fixed acrylic resin prosthesis, that was relined so as to make the gingival tissues properly scalloped.
8-9. After 3 weeks of provisionalization, the precision impressions were taken using an optical impression using the Itero intraoral scanning system.
10-19. As regards the digital impression, the Itero intraoral scanning system was used. This system is based on a confocal laser scanning technique with focal planes at 50 microns, it records 300-350 images per abutment and it is provided with autofocus up to 3 cm. About 100-110 static shots per arch are taken and then they are merged by means of specific reference points identified by the software, which is able to reduce the mean error interpolating the images. The gingival tissues were displaced using a single #2 retraction cord without any astringent agent. The optical impression was taken using the Itero system and a dedicated intraoral scanner. The impression procedure suggested by the software was followed: after gently removing each retraction cord, the three-dimensional morphology of each abutment was recorded. The image was taken as soon as the software interpolated correctly each abutment surface. Moreover, the system needed to record the morphology of the teeth adjacent to the abutments (2 per each emiarch) as well as of the antagonist teeth, in order to acquire the occlusal reference points necessary to the CAD phase.
20-21. Differently, a stereolitographic working model of the scanned area was obtained from the digital impression.
22. Zirconia single cores with a thickness of 0.5 mm were produced and tried in.
23. The fit of the frameworks was checked intraorally using a black silicon disclosing agent inside the zirconia cores, so as to highlight any pressure spot on the internal surface of each crown.
24-25. Then, the marginal precision of each coping was checked using a stereomicroscope (30x), gently displacing the marginal tissues apically by means of metal anatomical gingival divaricators. In all crowns no clinically relevant marginal misfit was noticed.
26-29. Zirconia copings were veneered by means of dedicated ceramics; after the intraoral tryin, the esthetic evaluation was made in accordance with the patient.
30-32. Finally, it was decided to cement the zirconia-ceramic single crowns using a resin luting agent. The occlusal contacts were carefully checked and balanced both in centric occlusion and in lateral and protrusive movements. Good marginal adaptations was observed.
33-35. The look and the smile of the patient were pleasant and improved.
36-38. At 2 year recall, the relation between periodontal tissues and crowns was excellent.
Work by Dr. Roberto Sorrentino DDS, MSc, PhD