Edentulous jaw impression techniques: An in vivo comparison of trueness

Statement of problem. Simplified edentulous jaw impression techniques have gained popularity, while their validity has not yet been evaluated. Purpose. The purpose of this clinical study was to compare the trueness of maxillary edentulous jaw impressions made with irreversible hydrocolloid (ALG), polyvinyl siloxane (PVS), PVS modified with zinc oxide eugenol (ZOE) (PVSM), and an intraoral scanner (TRI) with a conventionally border-molded ZOE impression (control). Material and methods. Twelve edentulous maxillary impressions were made with the impression techniques. The analog impressions were scanned using a laboratory scanner, imported into 3-dimensional comparison software, and superimposed against the corresponding control. Trueness was evaluated by calculating the effective deviation known as root mean square (RMS) for the entire surface (ES) and for specific regions of interest such as peripheral border, inner seal, midpalatal suture, ridge, and posterior palatal seal. The secondary outcomes for this study were the patients' perception of the impression techniques. Statistical analyses with the Wilcoxon tests were carried out (alpha=.05). Results. For ES, significant differences were found when comparing ALG (1.21 +/- 0.35 mm) with PVS (0.75 +/- 0.17 mm; P=.008), PVSM (0.75 +/- 0.19 mm; P=.012), and TRI (0.70 +/- 0.18 mm; P=.006) but not among the other groups. Significant differences were found for peripheral border when comparing ALG (2.03 +/- 0.55 mm) with PVS (1.12 +/- 0.32 mm; P=.006), PVSM (1.05 +/- 0.29 mm; P=.003), and TRI (1.38 +/- 0.25 mm; P=.008), as well as TRI and PVSM (P=.028). Significant differences were also found for inner seal when comparing ALG (0.74 +/- 0.36 mm) with PVSM (0.52 +/- 0.13 mm; P=.041), as well as TRI (0.8 +/- 0.25 mm) versus PVS (0.56 +/- 0.14 mm; P=.005) and PVSM (P=.005). The difference at the ridge was significant when comparing PVS (0.18 +/- 0.07 mm) with PVSM (0.28 +/- 0.19 mm; P=.015) but not among the other groups. A significant difference was also found for posterior palatal seal when comparing PVS (0.55 +/- 0.41 mm) with PVSM (0.60 +/- 0.43 mm; P=.034). Patient perceptions showed significantly better satisfaction scores for ALG (1.83 +/- 2.03) and PVS (3.17 +/- 2.40) than for TRI (4.08 +/- 2.71), PVSM (4.58 +/- 2.35), and ZOE (6.83 +/- 1.75). Conclusions. Edentulous impressions made with PVS, PVSM, and TRI had similar deviations and may yield clinically acceptable results. Irreversible hydrocolloids are contraindicated for definitive impression making in completely edentulous jaws.