Avaliação in vivo da temperatura pulpar de pré-molares humanos submetidos à luz Led Polywave® em diferentes protocolos e cenários clínicos

Abstract

Objective: To evaluate the pulp temperature (PT) of premolars in real time and pulp temperature increase (ΔT) induced by a light-emitting diode (LED) light curing unit (LCU) in class V preparations, under simultaneous airflow; and during restorative procedure with conventional and bulk fill composite resins. Material and methods: Aproved by local Ethics Committee (protocol #1,954,754 and #255.945), premolars of 26 patients who required extraction for orthodontic reasons were anesthetized and received absolute isolation. An occlusal access was performed with refrigerated highspeed handpiece, and the pulp was slightly exposed. A sterile thermocouple probe was then introduced into the pulp chamber (Temperature Data Acquisition - Thermes WFI, Physitemp). The tooth received a class V preparation, and 3 tests were performed according to the experimental groups. (1) exposition to a light of a polywave LED LCU (Bluephase 20i, Ivoclar Vivadent) with one of the following exposure modes(EM): 10 s at Low power (10s/L); 10 s at High power (10s/H); 30 s at High power (30s/H); 60 s at High power (60s/H); and 5 s in Turbo mode (5s/T). (2) continuous airflow simultaneously at 30 s/H exposure, compared to the control no-air. (3) PT data were collected during the class V restorations with: Tetric N Ceram Bulkfill (Ivoclar Vivadent) single photoactivated for 10 s (High mode, Bluephase 20i, Ivoclar Vivadent); Filtek Z250 in two increments (3M ESPE) photoactivated for 10 s each; Filtek Z350 (3M ESPE) single photoactivated for 40 s. PT was recorded every 0.2 s and the values were submitted to statistical analysis one-way (ANOVA) and Bonferroni Post-test (α = 0.05); paired Student t-test (α = 0.05); and Tukey's test (α = 0.05), respectively. The linear correlation between radiant exposure and PT was established by linear regression analysis. Results: All the EMs tested in the first stage generated an increase in PT (p <0.001). The exposure of 60 s/H generated ΔT of 5.5oC (p <0.001). A positive correlation was observed between radiant exposure and ΔT (r2=0.8962, p<0.001). For the exposures of 30 s/H, both the peak of PT and ΔT were significantly higher for the group without the airflow than with airflow and baseline PT (p <0.001), and the group with airflow had PT values significantly lower than baseline PT values (p = 0.003). For the restorations, only the photoactivation of the Z350 for 40 s (40.2 + 1.7°C) promoted a higher PT increase than baseline (35.0 ± 0.8°C) (p <0.001). PT after photoactivation of bulk fill CR was lower than that observed in other techniques (p = 0.012). Conclusion: Exposures with polywave® LEDs increased PT in most cases below 5.5°C, however the exposures of 60 s presented a risk to pulp vitality. The airflow was able to prevent PT increases, and additionally caused a decrease of the PT after the exposure. For the light cured restorations, the drop in PT during cavity preparation prevented a drastic PT increase during restorative procedures, demonstrating that the radiant exposure added to the exotherm of the materials were not sufficient to elevate PT to harmful levels.