Evaluation of soft tissues simulant materials in cone beam computed tomography.

Objectives: To evaluate different materials in simulating soft tissues and to analyze the influence of these materials on the mean (MPIV) and standard deviation of pixel intensity values comparing them to a gold-standard in CBCT images.
Methods: Images of three piglet heads with their soft tissues intact (gold-standard) and different simulant materials were acquired: ice, modelling wax, and ballistic gelatin, with the same thickness of the original soft tissues. The pixel intensities were measured in dental, bone and soft tissues regions, in the mandible and maxilla, for all the groups. Analysis of variance, Dunnet's, Pearson's and linear regression tests were performed.
Results: The simulators did not significantly change the MPIV of teeth in comparison with the gold-standard ( p = 0.1017). Only ice ( p = 0.0156) affected the MPIV of bone. Wax ( p  = 0.001) and ice ( p = 0.0076), but not ballistic gelatin ( p = 0.5814), altered the MPIV of soft tissue regions. When assessing the influence of the location (mandible or maxilla) among the simulants, the differences were significant only for the soft tissue regions. Standard deviation was not influenced by simulants ( p > 0.05), but ballistic gelatin presented the lower variability.
Conclusions: The ballistic gelatin was the best soft tissue simulant since it had the lowest influence on the pixel intensity values for all regions.