Unintentional amount of calcium hydroxide extrusion and high alkalinity diffusion distance: an in vitro study

The diffusion of high alkalinity over time following calcium hydroxide extrusion beyond the apical foramen has not been well investigated, particularly in relation to different apical foramen sizes. This diffusion may affect surrounding vital structures and related pain. This study aimed to evaluate the extent of unintentional calcium hydroxide extrusion and to measure the diffusion distance of high alkalinity from various apical foramen sizes over time.

Sixty-three mandibular premolars were divided into 5 groups based on apical foramen sizes of 20, 30, 45, 55, and 70 (n = 12 each) along with three negative controls. For calcium hydroxide extrusion measurement, pipette tips were used to cover the root apex, allowing the extruded calcium hydroxide to be collected in them. Then, calcium hydroxide was delivered into the canal using a polymer tip in the same manner across all groups. The quantity of calcium hydroxide extrusion was determined by comparing the tip weight before and after calcium hydroxide placement. To assess high alkalinity diffusion (pH 10-11), the same teeth were rinsed and reused by embedding them in 2% agar containing universal pH indicators followed by calcium hydroxide delivery. The extent of high alkalinity diffusion was measured by color extension at 0, 2, 6, and 9 h. Kruskal-Wallis test was employed to compare the weights of calcium hydroxide extruded beyond the apical foramen among different apical foramen sizes, as well as the diffusion distances of calcium hydroxide over time. Pearson correlations were used to define the relationship between the apical foramen size and the amount of extruded calcium hydroxide.

The extruded calcium hydroxide was positively correlated with the apical foramen sizes. The high alkalinity distances increased over time. Within two hours, all sizes of apical foramina demonstrated high alkalinity diffusion distances over 10 mm. At nine hours, there was no significant difference among the groups.

Within the limitations of this study, the extent of medicament extrusion was influenced by the size of the apical foramen. High alkalinity can develop within a few hours and may extend several millimeters beyond the physical presence of the medicament. The size of the apical foramen appears to have minimal influence on the diffusion of alkalinity.