Effect of Root Canal Dressings on Extraradicular pH in a Sealed Apex Model: An In Vitro Study

Endodontic treatment is mandatory after severe dental trauma such as avulsion or intrusion. Initial intracanal dressing with calcium hydroxide should be avoided according to international guidelines due to potential periodontal ligament damage by pH elevation. However, whether an intracanal dressing is able to alter the extraradicular site remains unclear. This in vitro study quantified extraradicular pH changes through dentinal diffusion of calcium hydroxide or Ledermix in a sealed-apex model in human teeth.

Thirty-five cryopreserved human premolars were prepared with or without cemental defects and received UltraCal XS, Ledermix, or saliva as an intracanal dressing. In the test groups, apices were sealed with composite resin material; the positive control remained with open apices. Teeth were stored in NaCl solution. External pH of the solution was measured on days 1, 3, 5, 7, and 14. A mixed model was applied to determine the effect of group, apical plug, cemental defect, and time on pH alterations.

Calcium hydroxide in teeth without apical sealing caused a sustained external alkalinisation (± pH 12). In teeth with apical sealing, no significant external rise in pH occurred for any dressing over time compared to day 1; only one sealed specimen with calcium hydroxide dressing reached pH 9.1 transiently. The pH in Ledermix and saliva groups remained roughly neutral irrespective of sealing or cemental defects. Mixed-effects modeling identified the apical plug as the only significant factor (p < 0.05); presence of cemental defects or days after treatment had no significant effect on pH.

In a sealed-apex model, intracanal dressings did not raise the external pH significantly by dentinal diffusion. Therefore, the results do not support the advantage of a certain intracanal dressing in endodontic treatment after severe dislocation injuries of teeth without open apices with respect to maintained physiological pH.