J Adv Prosthodont.  2017 Aug;9(4):287-293. 10.4047/jap.2017.9.4.287.

Accuracy of a separating foil impression using a novel polyolefin foil compared to a custom tray and a stock tray technique

• Pastoret M
• Krastl G
• Bühler J
• Weiger R
• Zitzmann N

• KMID: 2398076
• DOI: http://doi.org/10.4047/jap.2017.9.4.287

Abstract

PURPOSE
To compare the dimensional accuracy of three impression techniques- a separating foil impression, a custom tray impression, and a stock tray impression.
MATERIALS AND METHODS
A machined mandibular complete-arch metal model with special modifications served as a master cast. Three different impression techniques (n = 6 in each group) were performed with addition-cured silicon materials: i) putty-wash technique with a prefabricated metal tray (MET) using putty and regular body, ii) single-phase impression with custom tray (CUS) using regular body material, and iii) two-stage technique with stock metal tray (SEP) using putty with a separating foil and regular body material. All impressions were poured with epoxy resin. Six different distances (four intra-abutment and two inter-abutment distances) were gauged on the metal master model and on the casts with a microscope in combination with calibrated measuring software. The differences of the evaluated distances between the reference and the three test groups were calculated and expressed as mean (± SD). Additionally, the 95% confidence intervals were calculated and significant differences between the experimental groups were assumed when confidence intervals did not overlap.
RESULTS
Dimensional changes compared to reference values varied between -74.01 and 32.57 µm (MET), -78.86 and 30.84 (CUS), and between -92.20 and 30.98 (SEP). For the intra-abutment distances, no significant differences among the experimental groups were detected. CUS showed a significantly higher dimensional accuracy for the inter-abutment distances with -0.02 and -0.08 percentage deviation compared to MET and SEP.
CONCLUSION
The separation foil technique is a simple alternative to the custom tray technique for single tooth restorations, while limitations may exist for extended restorations with multiple abutment teeth.

Keyword

Dental impression; Stock tray; Custom tray; Separating foil; Accuracy

MeSH Terms

Reference Values
Silicon
Tooth
Silicon

Figure

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  Fig. 1 (A) Machined mandibular complete-arch metal model with special modifications before replacement of the right second premolar, (B) Second premolar with modified overlay preparation with reference lines on the occlusal plane.

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  Fig. 2 Distances measured on the master model and on the casts in the 3 different groups. (A) Intra-abutment distances (d1 - d4), (B) inter-abutment distance ×1, (C) inter-abutment distance ×2.

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  Fig. 3 Deviation of the measured intra-abutment (d1 - d4) and inter-abutment distances (x1 and x2) in the 3 experimental groups (CUS: custom tray, MET: stock metal tray, SEP: separating foil technique) compared to the master model (reference). Each error bar represents the 95% confidence interval of the mean.

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