Comparison of the accuracy for three dental impression techniques and index: an in vitro study.
OBJECTIVE
This in vitro study compared the dimensional accuracy of stone index (I) and three impression techniques: tapered impression copings (T), squared impression copings (S) and modified squared impression copings (MS) for implant-supported prostheses.


METHODS
A master cast, with four parallel implant abutment analogs and a passive framework, were fabricated. Vinyl polysiloxane impression material was used for all impressions with two metal stock trays (open and closed tray). Four groups (I, T, S and MS) were tested (n=5). A metallic framework was seated on each of the casts, one abutment screw was tightened, and the gap between the analog of implant and the framework was measured with a stereomicroscope. The groups' measurements (80 gap values) were analyzed using software (LeicaQWin - Leica Imaging Systems Ltd.) that received the images of a video camera coupled to a Leica stereomicroscope at 100× magnification. The results were statistically analyzed with Kruskal-Wallis One Way ANOVA on Ranks test followed by Dunn's Method, 0.05.


RESULTS
The mean values of abutment/framework interface gaps were: Master Cast=32 μm (SD 2); Group I=45 μm (SD 3); Group T=78 μm (SD 25); Group S=134 μm (SD 30); Group MS=143 μm (SD 27). No significant difference was detected among Index and Master Cast (P=.05).


CONCLUSIONS
Under the limitations of this study, it could be suggested that a more accurate working cast is possible using tapered impression copings techniques and stone index.
Department of Dental Materials and Prosthodontics, Araraquara Dental School, Univ Estadual Paulista, Araraquara, SP, Brazil. Electronic address: erica.fobusp@yahoo.com.br.
Erica Dorigatti
ED
de Avila
Luiz Antonio Borelli
LA
Barros
Marcelo Antonialli
MA
Del'Acqua
Sabrina Maria
SM
Castanharo
Francisco de Assis
Fde A
Mollo
D003734:Dental Casting Investment; D003760:Dental Impression Materials; D003761:Dental Impression Technique
D003734:Dental Casting Investment; D003760:Dental Impression Materials
Dental implant; Impression material; Impression technique; Transfer coping