RESUMEN
PURPOSE: To evaluate the effect of cheek retractors on the accuracy of capturing peripheral borders in totally edentulous digital scans by comparing the conventional impression technique to digital scans made using two different cheek retractors. MATERIAL AND METHODS: Sixteen edentulous maxillary impressions were made using three techniques: the conventional impression technique, using modeling thermoplastic compound and zinc oxide eugenol paste; the digital intraoral scanning technique using the DIO scan retractor (DIO); and using the Br.nemark lip retractor (BRAN). The control impressions of each patient were poured, scanned using a desktop scanner, then transferred into a three-dimensional analysis software. DIO and BRAN groups were scanned using an intraoral scanner, imported, and superimposed using best fit algorithm on the corresponding control. The root mean square for the whole surface and for particular interest regions were calculated to assess the degree of trueness. The patients' perceptions of the impression techniques were the secondary outcomes. Statistical analyses were performed using the one sample T-test and Wilcoxon test (α=.05). RESULTS: Significant discrepancies were found for BRAN and DIO compared to the control. No significant discrepancies were found when comparing RMS of BRAN and DIO at different regions. Scan retractors had a significant impact on patient satisfaction, with patients preferring DIO. CONCLUSIONS: Edentulous intraoral scans made using cheek retractors had similar deviations when compared to each other but diverged from the conventional impression in edentulous maxilla. Patient preferences for intraoral scans over conventional impressions were confirmed. CLINICAL IMPLICATIONS: The use of different retracting methods during intraoral scanning of totally edentulous maxillary arches does not affect the peripheral border registration.
RESUMEN
PURPOSE: The aim of this study was to compare and evaluate the retention of two new attachment systems used for implant-supported overdentures subjected to insertion-removal cycles. MATERIALS AND METHODS: Twenty custom-manufactured polyvinyl chloride models mimicking implant-retained over-dentureresin blocks were fabricated and divided into two groups (n = 10): group 1 ('Kerator' attachment) and group 2 ('EMI' attachment). Each model received two parallel implants (JD evolution®) 20 mm apart and was subjected to cyclic retention forces of 10, 100, 1000, 5000, 10000 and 14600 cycles using a universal testing machine in a 0.9% sodium chloride water solution at 22° C. Data were analyzed using one-way analysis of variance; the level of significance was set at a < 0.05. RESULTS: The 'Kerator' and 'EMI' attachment systems reported a significant decrease in retention (64 and 56.6% respectively) after 14600 insertion-removal cycles (p < 0.001). The 'EMI' attachment showed significant higher loss of retention than the 'Kerator' attachment all along the 14600 cycles (p < 0.05) except for cycles 100 and 5000 (p > 0.05). CONCLUSION: Within the limitations of this in vitro study, both attachments reported satisfactory retentive values during the 14600 cycles, the 'Kerator' attachment showed better retention than the new 'EMI' attachment. The initial retentive force of both attachments has gradually decreased. CLINICAL SIGNIFICANCE: Both attachment systems evaluated in this study can be used in clinical practice for implant-supported overdentures.