A study in two centres of variations in the time of apical barrier detection and barrier position in nonvital immature permanent incisors.

Objectives: To study barrier formation in nonvital, immature permanent incisors being treated using the apexification technique in two centres, and to establish the effect of the frequency of change of calcium hydroxide (CaOH) on barrier detection times.
Design: A retrospective study of the time of detection and the position of barriers.
Results: There were no significant differences between the two centres in terms of the average frequency of change of each CaOH dressing, the distribution of barrier detection times or the position of barriers (P > 0.05). There was a total of 107 teeth and the time of barrier detection was significantly earlier in more frequently dressed teeth (P = 0.013). Of the teeth with a barrier detection time of less than 9 months, 60.7% were dressed more frequently than every 3 months, as opposed to 39.1% of teeth with longer barrier times (P = 0.027). The mean time of barrier detection for all cases was 43.3 weeks. The majority of barriers were located at or near the apex.
Conclusion: The frequency of change of CaOH can increase the speed of barrier detection but does not appear to affect the position.