Root Canal Dentin and Calcium Hydroxide Points Interaction in PBS

Objective: This study is an extension of our previous work (2009 IADR Abst. 568) primarily aimed at characterizing the interface between root canal dentin and a calcium hydroxide containing gutta percha (CHGP) point after 16 m exposure to a phosphate buffer saline (PBS) solution.

Method: Canals in extracted single-rooted human teeth were endodontically prepared and obturated with CHGP points (Coltene) without any sealer. For comparison, canals were similarly filled with traditional GP points using a sealer (Roth). All filled teeth (n=3 for each material) were stored in PBS at pH = 7.2 and 37^oC for 16 m.  Following exposure, the teeth were sectioned perpendicular to the canals, polished and examined by SEM and EDXA.

Results: PBS exposure led to the emergence of a thick (~125μm) dense circular layer between dentin and CHGP.  The layer contained mainly Ca, P, and O, and is presumed to be hydroxyapatite (HA). It was firmly bonded to dentin. Dentinal tubules adjacent to this layer were filled with deposits containing mainly Ca, P, and O. Root canals filled with GP points remained virtually unaffected by PBS exposure.

Conclusions:

1. Despite the absence of a sealer, the calcium hydroxide point, CHGP, has been found to be effective in sealing open tubules, and in forming an apatitic barrier at the dentinal interface.
2. The above effects are attributed to calcium hydroxide, a component of CHGP. Though CH is sparingly soluble, it is highly bioactive, and spontaneously forms HA in a biological fluid.
3. The observed mineralizing effect of CHGP is similar to that reported for MTA (Dentsply-Tulsa), a root end filling material (2002 IADR Abst. 3156).