This randomized placebo-blind study aimed to evaluate the effect of
laser phototherapy (LPT) on
pain caused by symptomatic irreversible
pulpitis (SIP). Sixty patients diagnosed with SIP were randomly assigned to treatment groups (n = 15): G1 (control), G2 (
laser placebo-
sham irradiation), G3 (
laser irradiation at 780 nm, 40 mW, 4 J/cm2), and G4 (
laser irradiation at 780 nm, 40 mW, 40 J/cm2). Spontaneous
pain was recorded using a VAS score before (T0), immediately after (T1), and 15 min
after treatment (T2).
Local anesthetics failure during emergency endodontic treatment was also assessed. There was no
pain difference in T1 and T2 between the experimental
laser groups (G3 and G4) and the placebo group (G2). The 4-J/cm2 (G3) irradiation resulted in significant increase in the
local anesthetics failure in lower jar teeth. This effect could be suggested as consequence of the LPT improvement in local circulation and vasodilatation that would result in the increase of
local anesthetic agent absorption. The application of 780-nm
diode laser irradiation, at 4 and 40 J/cm2, showed no effect in reducing the
pain in SIP in comparison to the placebo group. The fluence of 4 J/cm2 showed a negative effect in
local anesthetics, resulting in significant increase of complimentary
local anesthesia during emergency endodontic treatment. This work provides evidence of the consequence of LPT application on teeth with symptomatic irreversible
pulpitis. LPT should be avoided in teeth with
pain due to irreversible
pulpitis.