Original Articles
Comparison of impression materials for direct multi-implant impressions,☆☆

https://doi.org/10.1016/S0022-3913(00)70136-3Get rights and content

Abstract

Statement of problem. Given that meticulous implant prosthodontic procedures are recommended to obtain the best possible intraoral fit, impression materials that are suitable for use with a direct impression technique warrant further investigation. Purpose. This in vitro study compared the amount of torque required to rotate a square impression coping in an impression and evaluated the accuracy of solid implant casts fabricated from different impression materials. Material and methods. Two direct transfer implant impressions were made using 8 impression materials; the torque required to rotate an impression coping in the impressions was calculated. Ten direct transfer implant impressions were made from the master model and poured in a die stone (Resin Rock) for 3 of the 8 initial impression material groups. Linear distances between steel balls placed on each abutment replica were measured with a traveling microscope to determine distortion in the impression procedure for each group. Data were analyzed (P =.05) with ANOVA and Ryan-Einot-Gabriel-Welsch multiple range test for post hoc. Results. With a 1-way ANOVA, average torque values among the material groups differed significantly (P =.001). Polyether (medium consistency) was found to produce the highest overall torque values, followed by addition silicone (high consistency), and then polysulfide (medium consistency). Statistically significant difference was also found among the 3 material groups’ mean absolute cast error using a 1-way ANOVA (P =.0086). Implant casts made from polyether (medium) or addition silicone (high) impressions were significantly more accurate than casts made from polysulfide medium impressions. Conclusion. On the basis of the results of this study, the use of either polyether (medium) or addition silicone (high) impression is recommended for direct implant impressions. (J Prosthet Dent 2000;83:323-31.)

Section snippets

Material and Methods

This in vitro study compared the torque required to rotate direct square impression copings in 8 impression material groups. Those material groups that produced torque values detectable by a torque-measuring unit were then compared for implant cast accuracy. An implant master model (Anderson Precision Machining, Inc, Iowa City, Iowa) was milled from a solid aluminum block. Five stainless steel abutment replicas (DCA 174, Nobel Biocare USA Inc, Chicago, Ill.) were cemented symmetrically in an

Results

Of the impression materials tested (Table I), torque values were detected for only 3: polyether (medium), addition silicones (high), and polysulfides (medium) (Fig. 7).

. Comparison of tested direct implant impressions for torque and group mean absolute cast error.

Impression coping position did not produce a statistically significant difference within material groups’ torque values (P =.1866), and a significant interaction effect was not identified between impression coping position and

Discussion

Methodologic and clinical considerations shed light on the relevance of these findings. The sensitivity of the Compudriver device (Consolidated Device Inc, City of Industry, Calif.) was used arbitrarily as a selection criterion for differentiating between impression material groups to be tested in the accuracy phase of this study. Thereby, impression materials that lacked rigidity to prevent possible rotation of the copings were eliminated from further consideration for viable accuracy. Several

Conclusion

The properties of an impression material, including rigidity and accuracy, can influence the accuracy of the implant impression, the accuracy of the solid implant cast, and ultimately, the accuracy of the cast implant framework. Choosing an impression material for multi-implant–retained prosthesis requires consideration of several factors, including material accuracy, clinician’s experience with material, length of time before the impression is poured, and amount of intraoral undercuts.

Within

Acknowledgements

I would like to thank Drs Steve Rosenstiel and Alan Carr for their encouragement and review of the manuscript. Thanks also go to Dr William Johnston for the statistical assistance and Dr Peter Monaghan for his suggestions regarding the measuring technique.

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    This project was supported in part by funds from The Ohio State University College of Dentistry and presented in part at the 1999 International Association of Dental Research Annual Session as a finalist for the 1999 Arthur R. Frechette Prosthodontic Research Award competition.

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    Reprint requests to: Dr Alvin G. Wee, Section of Restorative Dentistry, Prosthodontics and, Endodontics, College of Dentistry, the Ohio State University, 305 W 12th Ave, Columbus, OH 43210-1241, FAX: 614-292-9422, E-MAIL: [email protected]

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