Methods: A metal master die of maxillary first right molar was manufactured and 15 silicone impressions were taken. Adjacent master casts of each impression were produced with a standardized procedure using three gypsum materials (n=5) (Implantat-Rock (A), Picodent-camtec-rock (B), Esthetik Base Gold (C)). Afterwards master casts were scanned with an optical scanner (CEREC inLab). Zirconia crown copings were designed using the CEREC tooth database. Presintered zirconia blocks were milled in the CAM unit. The internal adaptation was evaluated by a replica technique. After removal from the master casts, the replicas were segmented, and measurements of the film thickness were performed with a light microscope. Descriptive statistics and a 1-way analysis of variance were used to analyze the differences in the marginal gap.
Results: The internal adaptation of zirconia crown copings are shown in Table 1. Significant differences could only be detected between the gypsum materials A vs. B and B vs. C.
gypsum material A B C
n 5 5 5
Mean 114 102 113
SD 70 58 57
Min 6 11 3
Max 1632 1010 282
Table 1 – Internal adaptation of zirconia crown copings [µm].
Conclusion: Within the limitations of this in vitro – study, following conclusions were drawn: 1. The mean internal adaptation was in a clinical acceptable range when the aforementioned gypsum materials were used. 2. The highest internal adaptation was determined when gypsum material B was used.