Abstract –  Background: Non-setting calcium hydroxide (Ultracal XS®) is recommended by the International Association of Dental Traumatology as the initial medicament following avulsion and replantation for mature teeth. There is experimental evidence to suggest Ledermix®, placed as an alternative inter-visit dressing may improve periodontal healing. Aim: This study investigated, using a multi-centre randomized controlled trial, the effect of two root canal medicaments, Ledermix® and Ultracal XS®, on periodontal healing of avulsed and replanted teeth. Material and methods: Children were recruited if they fulfilled all inclusion criteria. Treatment followed a standardized protocol. Assessment of periodontal healing or ankylosis was made clinically and radiographically by an experienced, ‘blinded’, clinician at 12 months. Results: Over 200 patients were assessed for eligibility at five centres. Twenty-nine patients were eligible for inclusion. Final analysis involved 22 patients with 27 teeth. Ankylosis was detected in four of the 12 teeth in the Ledermix® group and nine of 15 in the Ultracal XS® group. No significant difference between medicaments was found in the proportion of teeth or patients showing periodontal healing. Discussion: There was no significant difference in periodontal healing between the two medicaments at either a tooth or patient level. The numbers recruited fell short of an estimated power calculation. For patients meeting the inclusion criteria and completing the trial, periodontal healing was seen in 52% of teeth at the 12-month assessment between both groups. The only factor found to significantly influence the periodontal outcome was dry time.