What do systematic reviews say?

Ultrasonic instrumentation used alone (any ultrasonic device designed specifically for root canal treatment and capable of the active or passive removal of dentine within the root canal) vs Hand instrumentation used alone (files and reamers used manually)

The review found no eligible studies for this question.

• Hand and ultrasonic instrumentation for orthograde root canal treatment of permanent teeth 2008 · Cochrane All outcomes
  No eligible randomised controlled trials were identified.
  Studies not reported
  No studies found

Hand instrumentation in conjunction with (as an adjunct to) an ultrasonic device designed specifically for root canal treatment and capable of the active or passive removal of dentine within the root canal vs Hand instrumentation used alone (files and reamers used manually)

The review found no eligible studies for this question.

• Hand and ultrasonic instrumentation for orthograde root canal treatment of permanent teeth 2008 · Cochrane All outcomes
  No eligible randomised controlled trials were identified.
  Studies not reported
  No studies found

Placebo (sham irradiation, laser inactive) vs Control (no laser device used)

Placebo (sham irradiation, laser inactive) led to lower maximum pain (verbal rating scale, VRS) compared with control (no laser device used); GRADE not reported.

• Endodontic procedures for retreatment of periapical lesions 2016 · Cochrane All outcomes

  first postoperative week
  RR 0.04 [0.00, 0.61]
  1 study · 48 participants
  GRADE not reported

Low‐level laser therapy vs Placebo (sham) laser therapy

• Endodontic procedures for retreatment of periapical lesions 2016 · Cochrane All outcomes

  first postoperative week
  Maximum pain (VRS): 0 per 1000 (placebo) vs 0 per 1000 (LLLT); effect not estimable; 52 participants. No high-pain events in either group.
  1 study · 52 participants
  Very low