Temperatures recorded in air and on direct contact with the insert tip of the System-B Heat Source are shown in Table 1. It must be emphasized that 2 mm from the end of the insert tip (thus, where the higher temperature is recorded), data obtained by means of a thermocouple revealed lower temperatures than the ones shown on the display. In particular, by setting the instrument at 250 8C the temperature reached by the instrument was 123 8C at the tip, and 160, 158 and 66 8C, respectively, at 2, 4 and 20 mm from the tip (Table 1).
The distance between the apex and the deepest point reached by the insert tip was also recorded (Tables 2 and 3); mean values obtained revealed a deeper penetration in group 2 (2.86 mm) thangroup1 (3.26 mm) owing to the differences of the apex diameter (respectively, 0.30-0.35 and 0.20-0.25 mm).
Values of increments in temperature (DT) of the guttapercha of the tested specimens revealed by the thermocouple at points A and C are shown in Tables 2 and 3 (respectively for specimens of groups 1 and 2). DT recorded in point A revealed a mean value of 0.5 _0.5 8C for group 1 and 0.9 _1.1 8C for group 2 (Table 4). It must be emphasized that point A was set 1.5 mm from the apex, and thus in the specimens in which the insert tip arrived at 1mm from the foramen, the thermocouple was very close to the surface of the insert tip. DT values recorded at point C gave a mean value of 4.1 _1.7 8C for group 1 and 3.9 _1.81 8C in group 2 (Table 4).
Statistical analysis revealed that the data were normally distributed (Kolmogorov-Smirne Test). Lower and upper 95% were determined for each group (Table 4). The statistical analysis revealed that 95% of DT values at point A of group 1 were between 0.2 and 0.8 8C, whilst in group 2 were between 0.3 and 1.6 8C. Similarly,95% of the data at point C of group1were distributed between 3.1 and 5.1 8C, and in group 2 were between 2.9 and 4.9 8C (Table 4).
The two-way anova revealed a statistical difference between DT recorded at points A and C at both groups (P < 0.05), but no difference could be determined between the two groups as no relationship with the different apex diameter was found.
Table 1. Temperature recorded in air with a thermocouple in direct contact with the tip of the System-B-Heat Source.
Table 2. Increments of temperature in (DT) recorded at point A (1.5 mm from the apex) and C (2 mm from the CEJ) of specimens of group1 (apical diameter 0.20-0.25 mm).
Table 3. Increments of temperature (DT) recorded at point A (1.5 mm from the apex) and C (2 mm from the CEJ) of specimens of group 2 (apical diameter 0.30-0.35 mm).
Table 4. Statistical analysis of the increments of temperature (DT) recorded at points A and C of the two groups considered in the study.