Ion release characteristics, precipitate formation and sealing ability of a potential new root canal filling material

Abstract

Aim To test a new polycaprolactone (PCL)/bioactive glass (BAG) composite as a root filling material capable of producing a seal under moist conditions by precipitation.Methodology Formulations of PCL/BAG composites were made using the solvent casting method and then modified into a form physically deliverable into root canals. Root canals of single‐rooted extracted human teeth were modified by de‐coronation and removal of the apical 2 mm of the root. Canal instrumentation was performed with gates glidden drills (1% NaOCl and 17% EDTA irrigation) to achieve a degree of standardization of shape. The canals were filled with the composites using warm vertical compaction (the composites are thermoplastic and behave like gutta‐percha) but without root canal sealer. A group of obturated teeth (n = 6 per composite formulation) was monitored for ion release (Na+, Ca2+, PO43‐, P2O74‐, P3O93‐ and P5O105‐) into solution from the apical portion using ion chromatography. Three composite formulations were used to fill 10 roots each and half (n = 5) exposed to saline, whilst others were sectioned immediately; both were examined by light and scanning electron microscopy to evaluate adaptation, precipitate and film formation. A further group of 30 roots was obturated to evaluate seal formation by dye penetration; a control group (n = 10) consisted of conventional gutta‐percha and Roth's sealer delivered in like manner to the test material; two test groups (n = 10 each) were obturated with a composite formulation producing the optimal precipitate, the apices of teeth in one group were immersed in saline for 7 days and the other not.Results All samples released various amounts of ions which followed inversely to the concentration of iron oxide within the bioactive glass. Adaptation of the experimental material was better than the gutta‐percha control groups. The formation of precipitate was evident in some specimens; in others film formation and dentine tubule entry by the material was observed. The dye penetration test showed that composite root filling specimens immersed apically in saline for 7 days had significantly less leakage (almost none) than those not immersed in saline at all (P < 0.001) or the gutta‐percha control (P < 0.001).Conclusions Polycaprolactone–bioactive glass composites may have potential as ‘sealer‐free’ root filling material because of their ion release, precipitate formation and short‐term seal.