Ex-vivo evaluation of the intrapulpal temperature variation and fracture strength in teeth subjected to different external bleaching protocols

Abstract

This study evaluated the influence of bleaching protocols on intrapulpal temperature and fracture strength of the bleached teeth. Ninety maxillary incisors were assigned to 9 groups (n=10): G1: 35% carbamide peroxide (35% CP), G2: 38% hydrogen peroxide (38% HP), G3: halogen light, G4: LED-laser, G5: 35% CP + halogen light, G6: 38% HP + halogen light, G7: 35% CP + LED-laser, G8: 38% HP + LED-laser, and G9: no treatment (control). Pulp space was widened, a thermocouple was introduced through the apex up to the pulp chamber and the temperature was recorded (°C). The fracture strength (kN) was determined using an Instron machine. Data were analyzed by ANOVA and Tukey's test (p<0.05). The halogen light alone (1.10 ± 0.24) (G3) and associated with 38% HP (1.15 ± 0.30) (G6) produced the highest temperature increase, statistically different (p<0.05) from the other groups. G1 (0.15 ± 0.06) and G6 (0.19 ± 0.07) produced the lowest values, statistically different (p<0.05) from G5 (0.65 ± 0.49). The bleaching protocols increased the temperature, but no increment exceeded the critical value of 5.6°C. Neither 35% CP nor 38% HP or the light sources alone altered the fracture strength of the teeth.

Fracture resistance of endodontically-treated teeth submitted to bleaching treatment with hydrogen peroxide and titanium dioxide nanoparticles photoactivated by LED-laser

“…However, the similar results among the experimental groups is in accordance with other studies 7,15,23 , except in relation to the G4, since there were no studies conducted with this treatment protocol. Despite this bleaching agent presenting a lower hydrogen peroxide concentration, the fracture resistance reduction presented in this study was also similar to other experimental groups.…”

“…There is some controversy about the negative effects of the bleaching agents on the coronal fracture resistance of endodontically-treated teeth 6,7,15,22 . However, the similar results among the experimental groups is in accordance with other studies 7,15,23 , except in relation to the G4, since there were no studies conducted with this treatment protocol.…”

“…This system provides increased temperature, pigment activation and accelerates the catalysis of hydrogen peroxide 7 . On the other hand, it also can produce or accentuate fractures lines and/or cracks 6 , reducing the fracture resistance of teeth, mainly after several treatment sessions, as previously discussed.…”

“…Light sources may be used to activate the bleaching agents, increase the reaction and accelerate the bleaching process by hydrogen peroxide 6,7 . On the other hand, transparent bleaching agents present lower light absorption compared to bleaching agents associated with pigments [8][9][10] .…”

Influence of the Number of Bleaching Sessions on Fracture Resistance and Dentin Microhardness of Endodontically Treated Teeth

“…21 The LED device presents a blue light with a wavelength of 470 nm, similarly to previous studies 14,21 and infrared laser emitting 0.2 W of power, with a wavelength of 808 nm. Coelho et al 11 observed that neither 35% carbamide peroxide nor 38% hydrogen peroxide or the light sources alone changed the teeth fracture resistance.…”