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The International Journal of Oral & Maxillofacial Implants



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Int J Oral Maxillofac Implants 25 (2010), No. 2     15. Mar. 2010
Int J Oral Maxillofac Implants 25 (2010), No. 2  (15.03.2010)

Page 247-257, PubMed:20369082

Parameters of Passive Fit Using a New Technique to Mill Implant-Supported Superstructures: An In Vitro Study of a Novel Three-Dimensional Force Measurement-Misfit Method
Tahmaseb, Ali / Van de Weijden, J. J. / Mercelis, Peter / De Clerck, Renaat / Wismeijer, Daniel
Purpose: The objectives of this study are to describe, in vitro, a novel technique to measure the misfit of digitally designed and manufactured implant-supported frameworks according to a new concept based on computer-guided surgery in combination with previously placed mini-implants. Also, the digitally created framework and an impression-based milled structure were compared using strain gauge measurements.
Materials and Methods: Acrylic resin and plaster models were prepared to represent the edentulous mandible. After insertion of three mini-implants in the acrylic resin model, a cone-beam computed tomographic scan was performed. The data were imported to planning software, where six implants were virtually inserted. A drill guide and titanium framework were designed and milled using a fully digital computer-aided design/computer-assisted machining protocol. Six implants were inserted using the drill guide attached to the mini-implants. After an impression was made of the acrylic resin model with six implants, the second model (plaster model) was prepared. A second milled titanium structure was fabricated following optical scanning of the acrylic resin model. Strain gauge measurements were done on both structures attached to both models. To validate the results, a high-accuracy industrial optical scanning system was used to capture all connection geometry and the measurements were compared.
Results: The accuracy of the digital superstructures was 19, 22, and 10 µm with standard deviations (SD) of 19.2 (17.9), 21.5 (28.3), and 10.3 (10.1) µm for the x-, y-, and z-axes, respectively. For the impression-based superstructure the measured misfit was 11, 20, and 17 µm, with SD 11.8 (10.5), 19.7 (11.7), and 16.7 (8.2) µm for the x-, y-, and z-axes, respectively.
Conclusion: The misfit of the digitally designed and produced superstructure on the digitally planned and inserted implants was clinically insignificant.

Keywords: dental implants, guided surgery, misfit, superstructure