The anterior teeth of 5 young adult dogs, previously submitted to thermal stimuli during 3 days, had suffered cavities preparation with burs mounted in air turbine, under water or air cooling. The cavities were lined with zinc oxide-eugenol or paraffin and filled with silver amalgam. After 30 days, the pieces were removed and processed for microscopical analysis. The results obtained have permitted us to reach the following conclusions :
1) Teeth submitted to thermal stimuli in which cavities were prepared and lined with paraffin have showed a more intense pulpal inflammatory reaction, when the cavities were prepared under air spray than under water spray.
2) The cavities lining with zinc oxide-eugenol has produced, 30 days after the preparation, absence of pulpal inflammatory reaction independent of the method of cooling.

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In Part 9 and the present Part the authors examined dynamic properties and inner structures of polysulfide rubber products by dissolution test as well as by preparing stress relaxation curves, stress-strain curves and rigidity-temperature curves by means of free torsion oscillation method. The results can be summarized as follows :
1) The examination on stress relaxation at 30°C showed that the cured products having manganese group oxidizing agents had moduli of elasticity higher than those of the products having lead peroxide as oxidizing agent, though they showed a slight tendency to decrease almost rectilinearly.
The examination on stress relaxation at 100°C revealed that the modull of elasticity showed a tendency to decrease from around 10²sec. This phenomenon is considered to indicate an intermediate behavior between polyisobutylene, non-cross-linked rubber, and cross-linked polysulfide rubber. Furthermore, the stress at 100°C intermittently measured for three hours showed a slight tendency to increase with the lapse of time, but the difference being hardly considered to be of special significance, no conclusive evidence was given to show that the strees relaxation was caused by chemical action.
2) By fixed-velocity extension tests, stress-strain curves were prepared and 3S/ (α-α-2) vs. α-1 was plotted. As the result it was made clear that the curves became almost rectilinear showing typical behavior of cross-linked rubber, which could be represented by Mooney-Rivlin's formula.
3) According to rigidity-temperature curves prepared by means of free torsion oscillation method, the test materials not heat-treated had low rigidity as compared with the heat-treated materials, and the curves showed descending tendencies at lower temperatures though gently. This is presumably due to the fact that the heat-treatment made substances which until then remained unreacted in the test materials react and made rigidity high.
All rigidity-temperature curves having wide plateau ranges from 0°C to 130°C showed typical behavior of cross-linked rubber.
4) To examine whether a test material is soluble in solvents is one of the effective method to determine the test material to be linear high-molecular substance or cross-linked high-molecular one. The dissolution state of cured products completely hardened by 5 hours heat-treatment at 100°C was therefore examined by using various solvents and as a result it was made clear that the test pieces swelled badly in tetrahydrofuran and other strong solvents, and though partially brownish precipitates were seen, the original shapes of test pieces were kept unchanged. From this result it was presumed that these kinds of polysulfide rubber were of loose-reticulated structure.

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