A2 ◊Page A1 ENDO TRIBUNE Dental Tribune Middle East & Africa Edition | 1/2020 1c 1d Fig. 1c: Canals were filled with EndoSequence BC Sealer and sectioned at sequential distances from the apex. The gutta-percha cone facilitates dispersion of the sealer into the apical seat and irregularities of the root canal space (attribution Drs Trope and Debelian). Fig. 1d: Microstructure of calcium orthophosphate cement after hardening. Mechanical stability is provided by the physical entanglement of crystals. Fig. 2: Chart shows in vitro evaluation of saliva penetration in the root canals. The seal achieved with gutta-percha alone is indis- tinguishable from the negative control (attribution Drs Khayat et al.). Fig. 3: Table shows expansion/shrinkage of popular sealers. Silicone and epoxy-resin sealer expand slight- ly before shrinking. By contrast, bioceramic sealer ex- pands slightly on setting but does not shrink. 4a 4b 5a 5b Fig. 4a: Chemistry associated with the hydration reaction of bioceramic material (calcium sili- cates) with water (moisture present in canal and tubuli) creates calcium silicate hydrate and calcium hydroxide. Fig. 4b: Precipitation reaction of the bioceramic (calcium phosphate). The hydroxyapatite co-precipitated within the calcium silicate hydrate phase produces a com- posite-like structure, reinforcing the set cement. The bioactivity of the calcium-silicate-based materials has been shown to produce mineralisation within the subjacent dentine substrate, extending deep within the tissues (attribution Dr Martin Trope). Fig. 5a: After irrigation, the canal is dried (moisture enhances set of bioceramic sealer) and a mated taper gutta-percha cone is fit to working length (final ir- rigation with EDTA results in higher bond strength values for bioceramic sealer than either CHX or NaOCl).39 Fig. 5b: Bioceramic gutta-percha and sealer show promise of resistance to the fracture of endodontically treated teeth; in an in vitro study.40 condensation enabled gutta-percha to replicate the microstructural anatomy of the root canal space to a demonstrably greater degree than any previous technique.18, 19 Despite the enhanced rheology, gutta-percha neither adhered to nor penetrated the interfacial dentine. The sealer was integral to achiev- ing a positive treatment outcome. Schilder and Goodman20 established the hypothesis that warm vertical condensation pushed a greater vol- ume of filler material into the apical space and theoretically the mate- rial would not shrink on cooling; however, regardless of enhanced gravitometrics, leakage studies on gutta-percha alone and gutta-percha and sealer showed their inability to create an impervious apical seal.21 Carrier-based obturation The prototype of carrier-based ther- moplasticised gutta-percha obtura- tors was developed by Dr WB John- son in 1978. Traditionally, the beta formulation of gutta-percha was used for its improved stability, hard- ness and reduced stickiness. Alpha phase gutta-percha was chosen for CB as it demonstrates low viscosity, it flows with less pressure or stress and creates a more homogenous filling.22 The latest iteration of carrier-based obturators is GuttaCore (Dentsply Sirona), a system made entirely of gutta-percha with a core obturator prepared with cross-linked gutta-per- cha. This method of obturation ap- pears to have significantly less voids and gaps than lateral compaction.23 The volume of sealer is the weak link in the chain of success; volume must be minimised by the density of the core/filler regardless of the technique used. With the new ar- ray of equipment for identifying, shaping and cleaning the root canal space, reliance on ineffective ma- terials and techniques mandate a paradigm shift in root filling. When tested in an in vitro model, microbes will permeate the length of the canal space in two hours if only gutta-per- cha is present in the canal without sealer. The leakage can be delayed for up to thirty days with the use of sealer. Traditional sealers generally shrink on setting and wash out in the presence of tissue fluids24 (Fig. 3), whereas bioceramic sealer do not. Bioceramic nano-technol- ogy: the reckoning Bioceramic materials (calcium phos- phate) include alumina, zirconia, bioactive glass, hydroxyapatite and resorbable calcium phosphates.25–29 They are used as joint or tissue re- placements in both medicine and dentistry as they are chemically and dimensionally stable, biocompat- ible and osteoconductive. Biocer- amic sealers are composed of tri- calcium silicate, dicalcium silicate, colloidal silica, calcium phosphate monobasic, calcium hydroxide and a thickening agent. Zirconium oxide is used as the radiopacifier and the material is aluminium- free. The chromogenic effects of all root sealers increase when excess sealer is not removed from coro- nal dentine of the pulp chamber.30 Bioceramics are ideal for use in en- dodontics as they are not affected by moisture or blood contami- nation and, therefore, technique sensitivity is not an issue, unlike most other sealers where moisture negates their performance. Being that they are hydrophilic, residual moisture in the canal and dentinal tubuli are biochemically a positive factor. In the context of creating an impervious seal, they are dimen- sionally stable and expand slightly on setting, ensuring a long-term seal due to the hydration reaction forming calcium hydroxide and later dissociation into calcium and hydroxyl ions.31 In vitro testing by Prati and Gandolfi stated that bi- oceramic materials can expand by 0.2–6 % of their initial volume.32 In addition, they are shown to pen- etrate into dentinal tubules at a greater degree than AH Plus in both single cone and warm vertical tech- niques at 2 mm to apex (P < 0.05).33 Bioceramic material may be an es- sential element in indirect and di- rect pulp capping and pulpotomy proce-dures that are an integral part of endodontic therapy’s goal of maintaining the vital pulp to en- sure a healthy per-iradicular peri- odontium. For all these reasons, premixed bioceramic materials are seen as an alternative material of choice for pulp capping, pulpot- omy, perforation repair, root end filling and obturation of immature teeth with open apices, as well as for sealing root canal fillings of ma- ture teeth with closed apices.34, 35 6 7 8a 8b 9a 9b 10 Fig. 6: An aliquot of EndoSequence BC sealer is injected into the coronal and middle thirds of the root canal space using tips designed for the sealer cartridge. Fig. 7: The Lentulo spiral is calibrated 2 to 3 mm short of the apical terminus. Slow-speed rotation in a forward mode disperses the sealer flow down the tip of the spiral. Fig. 8a: The pre-selected gutta-percha cone is buttered with sealer and slowly intro- duced into the canal to seating. The gutta-percha at the i nterface of the orifice is marked and the cone retrieved in a counter-clockwise manner. Fig. 8b: A 2 to 3 mm segment is removed from the coronal aspect of the gutta-percha cone. The cone is then buttered with sealer, reintroduced into the canal space and tapped to seating with a condenser. It is not advisable to use heat to remove the gutta- percha as it desiccates the bioceramic sealer. Fig. 9a: The depth of the footing is calibrated for core and post-channel creation. Fig. 9b: Endodontic biominimalism is extended by the use of fibre posts of small tip size and matched taper. Fig 10: Postoperative radiograph of tooth #36 (degenerated pulp with periradicular extension— attribution Dr Nasseh). When setting, the pH of the biocer- amic is above 12 due to a hydration reaction forming calcium hydroxide and dissociation into calcium and hydroxyl ions, which could explain the antibacterial properties of bioce- ramics (Fig. 4a). The release of cal- cium hydroxide and its interaction with phosphates on contact with tissue fluids forms hydroxyapatite. This may explain the osteoconduc- tive potential of the material (Fig. 4b).36 Calcium phosphate is the main inorganic component of the hard tissues (teeth and bone). Con- sequently, the literature notes that many bioceramic sealers have the potential to promote bone regenera- tion. The amount of Ca2+ released from Endo-sequence BC Sealer is far higher than that from AH Plus mainly after seven days. A concord- ance was also observed between pH and the amount of Ca2+ released in both analysed materials. A possible explanation for the high amount of Ca2+ released by bioceramic ce- ments could be associated with setting reactions, including hydra- tion reactions of calcium silicates.37 A scientific paradigm shift in root filling As the root filling paradigm shifts to bioceramic sealers, the practitioner can execute a bio-minimalistic an- timicrobial protocol for root canal treatment, leaving a thicker and stronger root. Bioceramic sealer is used with a dedicated gutta-per- cha cone impregnated and coated with nanoparticles of bioceramic, thus eliminating the gap between the core and sealer. This combina- tion has been shown to be similar or better than conventional en- dodontic sealers as observed in in vitro and in vivo animal studies.38 Bioceramic dispersion protocols – In order to ensure an exact shape at the apical terminus (circular or ovoid) and intimacy of fit of the bioceramic nanocoated gutta- percha cone, an .02 stainless steel file is used to refine the apical seat. – The gutta-percha cone designed for use with bioceramic sealer is fit to working length is impreg- nated with bioceramic nanopar- ticles, mated to the taper of the prepared canal, EndoSequence BC Points (Brasseler USA, Figs. 5a & b). – When used with anatomically dedicated files (XP-3D Shaper and Finisher (Brasseler USA), the apical seat created minimises sealer ex- trusion (tug back is not required). – T raditional compaction tech- niques require maximal volume of the gutta-percha core and minimal volume of sealer. Bi- oceramic dispersion root filling requires minimal gutta-percha and maximal sealer volume. – 0.05 mm of the apical tip of the dedicated gutta-percha cone is re- moved to prevent sealer extrusion. – The master apical file coated with sealer is used in a coun- ter clockwise motion to de- posit sealer at the apical seat. – An aliquot of EndoSequence BC sealer is injected into the coronal and middle thirds of the root canal space using In- tra Canal Tips designed for (Fig. 6). the sealer cartridge – A lentulo spiral positioned no less than 2 to 3 mm short of the api- cal seat is used to flow the sealer down the tip of the spiral (slow- speed in forward mode) (Fig. 7). – The gutta-percha cone delivers the bioceramic sealer from the coronal reservoir to the apical seat without heat or pressure; the bi- oceramic capillary condensation of sealer adheres to the interfa- cial dentine and disperses into the dentinal tubuli to develop an impervious apical and intraca- nal seal (Figs. 8a & b, Figs. 9a & b). – In contrast to lateral condensa- tion, carrier-based obturation and warm vertical condensation, the gutta-percha cone must be delivered slowly and incremen- tally to length. The preservation of dentine resulting from the integration of the XP-3D file sys- tem and the EndoSequence BC gutta-percha point is shown in the postoperative radiograph (Fig. 10). – Calibrated “beds” are developed for footings or cementation of fibre posts. The fibre post (.04 taper) determines the depth of the post channel created by the instrumentation before the ob- turation. This drillless method prevents additional intracanal dentinal weaking, Fibre posts with a #50 tip and .04 taper are invari- ably the maximum size necessary in molars and premolars. In ante- rior teeth, the tip size is depend- ent on the intracanal diameter. Conclusion All variables in an equation are inter- dependent. In the case of endodontic success, each procedural event is a ccountable for positive treatment outcomes; however, r egardless of its importance, if a concomitant event does not provide a suitable biologic conclusion, failure ensues. Biomini- malism in root canal space prepara- tion requires a root filling material that replicates the internal anatomy of the root canal space, adheres to interfacial dentine and creates an impervious, irreversible seal at all portals of exit. The last mile of the bi- oceramic endodontic marathon will be to obviate the need for a gutta- percha core of any formulation. Editorial note: A list of references is available from the publisher. in This article was published roots — international maga- zine of endodontics, Issue 1/19. About the author Dr Kenneth Serota graduated with a DDS from the University of Toronto Faculty of Dentistry in Canada and re- ceived his Certificate in Endodontics and Master of Medical Sciences from the Harvard– Forsyth Dental Center, Boston in Massachusetts in the US.