Hydroxyl Ion Diffusion through Radicular Dentine When Calcium Hydroxide Is Used under Different Conditions

Area of Science:

• Endodontics
• Dental Materials Science
• Biomaterials

Background:

• Calcium hydroxide (Ca(OH)₂) is widely used in endodontics for its antibacterial properties, attributed to its high pH.
• Understanding hydroxyl ion diffusion through dentine is crucial for optimizing Ca(OH)₂-based intracanal medicaments.

Purpose of the Study:

• To investigate the diffusion of hydroxyl ions from various calcium hydroxide formulations through dentine.
• To evaluate the effect of Ledermix and the smear layer on pH and diffusion in dentine cavities.

Main Methods:

• Dentine cavities (deep and shallow) were prepared in teeth.
• pH was measured in cavities over 12 weeks for control and experimental groups using different Ca(OH)₂ formulations (Calmix, Calmix/Ledermix, Calasept Plus/Ledermix, Pulpdent/smear layer).

Main Results:

• Calmix alone (Group 2) demonstrated significantly higher inner and outer dentine pH compared to all other groups.
• Mixing Ca(OH)₂ with Ledermix resulted in comparable hydroxyl ion release but lower overall pH and diffusion than Ca(OH)₂ alone.
• The presence of a smear layer significantly inhibited pH diffusion.

Conclusions:

• Calcium hydroxide alone provides superior hydroxyl ion diffusion and higher pH in dentine compared to formulations mixed with Ledermix.
• Ledermix incorporation reduces the efficacy of Ca(OH)₂ in maintaining high pH within dentine.
• The smear layer acts as a barrier, impeding the diffusion of hydroxyl ions and reducing the effectiveness of intracanal medicaments.