Objectives of root filling Currently, it is not possible to effect optimal sterilization of the root canal space, nor can biofilms be completely eradicated from the interfacial dentin. Thus, the aim involves three basic requirements from a root filling: 1. Stop coronal leakage after the root canal is filled and the final restoration placed. 2. Entomb surviving microflora in the interfacial dentin so that they cannot reassert their presence and communicate with the periradicular tissues. 3. Prevent influx of periapical fluids to provide nutrients for residual microflora in the root canal space.2 Lateral- and carrierbased obturation Many in vitro, in vivo and clinical outcome studies have been performed primarily on single cone or lateral condensation techniques. It is apparent that they fail in their primary function of sealing the root canal space long term.3-4 Sabeti et al found no diffence in the outcome when a canal was root-filled compared to left empty. This study and others emphasize the poor quality of our current root filling techniques and the importance of the coronal restoration for successful root canal treatment outcomes.5-6 A study by Gihooly et al showed that multiphase gutta-percha obturation had significantly less apical dye leakage than lateral condensation in curved canals (P < 0.05).7 Success based on degree of density is not the issue as gutta-percha does not bond to dentin. Sealer remains the dominant concern re: leakage over the long term. Fig. 2 shows that when tested in an in vitro model, microbes will permeate the length of the canal space in two hours if only gutta-percha is present in the canal without DE GP SE Fig 1a. SEM of cut root filled with gutta-percha and AH Plus sealer. Note the gap between the gutta-percha (GP) and sealer (SE). (Courtesy of Dr. Eldeniz, AU.) Figs 1b (top) and 1c (above). Image shows molar roots filled with bioceramic sealer cut at different distances from the apex. A single gutta-percha point is used as a cold plugger to create hydraulic pressure that moves the sealer to the apical pulp stump and fills any irregularities in the root canal space. Human Saliva Penetration of Coronally Unsealed Obturated Root Canals 30 22,5 15 7,5 Negative Vertical Cond GP Only Positive Lateral Cond Fig 2. In vitro evaluation of saliva penetration of root canals. Note that the seal achieved with guttapercha alone is indistinguishable from the negative control. (from Khayat et al). dentaltown.com \\ NOVEMBER 2017 79http://www.dentaltown.com