3D-Precision of Dies Made with Different Impression Materials and Techniques

Objectives: The precision of a dental impression is an important and determining factor for the fit of dental restorations. A three-dimensional, non-destructive, computer-aided analysis has been established for the assessment of impression precision applying non-contact digitizing. Aim of this study was the examination of a new range of impression materials.

Methods: Duplicate dies (n=10) of a real model were made with five two-phase impression materials (Flexitime Putty/Flexitime Medium/Light Flow, Flexitime fast&scan Putty/Flexitime fast&scan Medium/Light Flow, Heraeus Kulzer; Honigum Heavy/Light, DMG; Germany), scanned by two different digitizers (Model Scan=MSC); (ODKM97, Fraunhofer IOF, Germany; D700, 3Shape, Denmark) and compared to the corresponding virtual CAD-model. For two materials, the impression itself was digitized (impression scan=ISC) with D700. The differences to the CAD-model were calculated (geomagic, Geomagic Inc., USA) and statistically analyzed with one-way ANOVA (SPSS 19.0, IBM, USA).

Results:

Material	Impression technique	Digitizing	Mean pos. [�m]	SD	Mean neg. [�m]	SD
Honigum	two-stage	MSC-ODKM97	11,1*	2,4*	-11,5*	1,4*
	one-stage	MSC-ODKM97	10,6*	1,3*	-10,2*	1,1*
Flexitime light	one-stage	MSC-ODKM97	10,3	1,7	� -8,9	0,6
	one-stage	MSC-D700	16,2	1,5	� -8,2	0,7
Flexitime medium	one-stage	MSC-ODKM97	14,5	3,3	� -9,0	1,2
	one-stage	MSC-D700	16,1	1,3	� -8,3	0,5
Flexitime fast&scan light	one-stage	MSC-ODKM97	10,3	1,7	� -8,7	0,6
	one-stage	MSC-D700	14,3	1,1	� -7,7	0,4
	one-stage	ISC-D700	� 6,4	1,1	� -5,7	0,3
Flexitime fast&scan medium	one-stage	MSC-ODKM97	� 9,2	2,1	� -8,5	0,5
	one-stage	MSC-D700	14,5	0,8	� -7,7	0,5
	one-stage	ISC-D700	� 5,8	0,4	� -5,6	0,4

*Data based on a former evaluation

Conclusion: All materials showed a high, clinically suitable precision with no significant differences. MSC with ODKM97 resulted in statistically significant lower deviations (material dependent p=0.009 to p=0.014) compared to D700. The ISC showed excellent values and significantly higher precision than the MSC as long as the ratio of width and height (1:1.5) was strictly kept. Further studies concerning tooth geometry are needed.