Marginal accuracy of all-ceramic copings – generated with four systems

Objectives: The purpose of this study was to evaluate the marginal fit of four all-ceramic systems simulating clinical conditions.

Methods: 20 practitioners took part in a practical phantom head course applying a chamfer preparation on the upper right central incisor for all ceramic restorations. Two impressions were taken using the same technique. Thus, fourty impressions were assigned in groups of ten randomly to four CAD/CAM systems in order to produce master dies: DCS [DCS], Inlab [INL], Kavo Everest [KAV] and Cercon [CER]. Whereas the systems [INL], [KAV] and [CER] used green blanks for manufacturing their copings, [DCS] used HIP-zirconia. The time expenditure for improving the fit on the master dies was measured. Then the accuracy of the copings was documented on the phantom head dies by replica technique with low viscosity silicone, that was stabilised with putty material. The replica samples were cut in oro-vestibular and mesio-distal direction.

The marginal discrepancies were examined under microscope (magnification 50). Statistics were done with SPSS for windows. For testing significant differences the U-test was computed at p≤0.05.

Results: For [DCS] as marginal mean (standard deviation) 80 µm (SD ±60 µm) and as median 69 µm were measured. [CER] delivered a mean (SD) of 105 µm (SD±48 µm) and a median of 100 µm. [INL] revealed a mean of 100 µm (SD ±35) and a median of 99 µm. [KAV] achieved 121 µm (SD ±83) as mean and 108 µm as median. There was found a significant difference between [KAV] and the other systems. The mean time expenditiure for improving the fit was 4:49 [min:sec] for [DCS], 7:31 for [CER], 1:05 for [INL] and zero for [KAV]

Conclusion: All systems achieved sufficient results under phantom head conditions. For [KAV] an improved accuracy could be supposed if an adjustment would have been done.