J Adv Prosthodont.  2014 Feb;6(1):22-29. 10.4047/jap.2014.6.1.22.

Evaluation of different approaches for using a laser scanner in digitization of dental impressions

• Lee WS
• Kim WC
• Kim HY
• Kim WT
• Kim JH

• KMID: 2176566
• DOI: http://doi.org/10.4047/jap.2014.6.1.22

Abstract

PURPOSE
This study aimed to investigate the potential clinical application of digitized silicone rubber impressions by comparing the accuracy of zirconia 3-unit fixed partial dentures (FPDs) fabricated from 2 types of data (working model and impression) obtained from a laser scanner.
MATERIALS AND METHODS
Ten working models and impressions were prepared with epoxy resin and vinyl polysiloxane, respectively. Based on the data obtained from the laser scanner (D-700; 3Shape A/S, Copenhagen, Denmark), a total of 20 zirconia frameworks were prepared using a dental CAD/CAM system (DentalDesigner; 3shape A/S, Copenhagen, Denmark / Ener-mill, Dentaim, Seoul, Korea). The silicone replicas were sectioned into four pieces to evaluate the framework fit. The replicas were imaged using a digital microscope, and the fit of the reference points (P1, P2, P3, P4, P5, P6, and P7) were measured using the program in the device. Measured discrepancies were divided into 5 categories of gaps (MG, CG, AWG, AOTG, OG). Data were analyzed with Student's t-test (alpha=0.05), repeated measures ANOVA and two-way ANOVA (alpha=0.05).
RESULTS
The mean gap of the zirconia framework prepared from the working models presented a narrower discrepancy than the frameworks fabricated from the impression bodies. The mean of the total gap in premolars (P=.003) and molars (P=.002) exhibited a statistical difference between two groups.
CONCLUSION
The mean gap dimensions of each category showed statistically significant difference. Nonetheless, the digitized impression bodies obtained with a laser scanner were applicable to clinical settings, considering the clinically acceptable marginal fit (120 microm).

Keyword

Digitization of impression bodies; Dental CAD/CAM system; Zirconia three-unit FPDs; Marginal gap; Internal gap

MeSH Terms

Bicuspid
Denmark
Denture, Partial, Fixed
Molar
Seoul
Silicone Elastomers
Siloxanes
Silicone Elastomers
Siloxanes

Figure

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  Fig. 1 Image magnified of a quarter silicone replica at the margin area.

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  Fig. 2 Cross-sectional view of locations for gap width measurements on silicone replicas: P1, marginal gap; P2, cervical gap (400 µm above P1); P3, 1/3 of axial from marginal gap; P4, 2/3 of axial from marginal gap; P5, axio-occlusal transition gap; P6, occlusal gap (1/2 of P5and P7); P7, central gap.

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