Effect of digitizing techniques on the fit of implant-retained crowns with different antirotational abutment features

Statement of problem. The development of computer-aided design/computer-aided manufacturing technology has enabled the fabrication of implant-retained restorations. However, information on the marginal and axial accuracy of restorations fabricated by different digitizing techniques with different antirotational abutment features is not sufficient.
Purpose. The purpose of this in vitro study was to evaluate the influence of digitizing techniques on the fit of implant-retained crowns with 2 antirotational features.
Material and Methods. An experimental working cast housing a tissue-level dental implant was created. Resin-retained abutments with different antirotational features were connected to the implant. Optical impressions of 2 abutment types were obtained separately with 1 chairside and 2 laboratory approaches. Alumina silicate restorations were milled from chairside optical impressions, and ceramic oxide cores were milled from laboratory optical impressions. Restoration fit was evaluated from axial sections of restorations with silicone materials representing the marginal and axial gaps. Axial and marginal fits were measured on digital photographs of the sectioned specimens with a computer program. Two-way ANOVA was used to compare differences between abutments with 2 different antirotational features and digitizing techniques separately for the marginal and axial fits of single implant-retained crowns. A post hoc least significant difference test was used to compare digitizing techniques (a1?4.05).
Results. Significant differences in the marginal fit of single-implant-retained crowns were found among digitizing techniques (P1?4.011) and between antirotational features (P<.001). No significant difference in the axial fit of single-implant-retained crowns was found among digitizing techniques (P1?4.905) or between antirotational features (P1?4.075).
Conclusions. Within the limitations of this in vitro study, the marginal fit of single-implant-retained crowns was affected by antirotational abutment features. Furthermore, digitizing techniques were found to play an important role in the marginal fit of single-implant-retained restorations.

Clinical Implications
Digitizing techniques and antirotational abutment features may affect the marginal accuracy of single-implant-retained crowns.

G.Aktas, N. O?Özcan et al. Effect of digitizing techniques on the fit of implant-retained crowns with different antirotational abutment features J of Prosthet Dent 2013 (article in press)