Chairside measurement of the marginal and internal fit of crowns: a new intraoral scan–based approach
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To investigate the marginal and internal fit of crowns, a new intraoral scanner–based digital approach for chairside measurement (D-IOS) was systematically analysed and compared with the conventional silicone replica technique (CV-SR) and digital 3D analysis software (D-GOM).
Materials and methods
Two models, representing different clinical situations, were constructed, and the first molar was prepared for a full-coverage crown. On the basis of an intraoral scan (Trios 3), copings of three different materials (non-precious alloy, zirconium dioxide, and resin composite) with two different cement spaces (80 μm, 50 μm) were manufactured. The fit of the copings was investigated by all three methods (CV-SR, D-IOS, D-GOM). Therefore, the cement space was visualized with low-viscosity silicone and digitalized with a second intraoral scan. Evaluation of fit by the D-IOS-method was measured in the intraoral scanner software, whereas for analysis by D-GOM, both intraoral scan datasets were transferred to 3D analysis software (GOM Inspect). The CV-SR-method was used as a control group. For all copings, the measurements were repeated five times. The data were analysed with ANOVA.
No significant differences between the three evaluation methods and the coping materials were shown. However, in the occlusal area, the internal gap was significantly higher compared to the internal gap in the marginal and axial areas regardless of the cement space setting (p < .05). The target parameter of the cement spaces did not match the actual measured internal gaps.
All three evaluation methods and coping materials can be used for the measurement of fit within different clinical situations.
The digital chairside measurement implemented in the intraoral scanner software enables an easy, applicable evaluation of fit of crowns without additional laboratory devices or special software applications.
KeywordsInternal fit Marginal fit Chairside Intraoral scanner Replica technique CAD/CAM
The authors would like to thank our biostatistician, Dr. Johannes Herrmann, for the statistical analysis. Furthermore, we gratefully acknowledge the support of our dental technician Thorsten Landgraf (Zahntechnikzentrum Eisenach, Germany).
The work was supported by the Department of Prosthodontics, Justus-Liebig-University in Giessen, Germany.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The use of human teeth was approved by the local ethics committee.
For this type of study, formal consent is not required.
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