ROEN0110

12 I I special _ endo-implant algorithm optimise the use of existing methods and materials and develop new ones to prevent and treat apical periodontitis. Varyingdegreesofsterilityoftheroot-canalspace are achieved by mechanistic removal, the chemical reactivity and fluid dynamics of irrigants and their introduction to the canal space; however, the proto- cols used today cannot predictably provide sterile canals. As none of the elements of endodontic therapy (host defence system, systemic antibiotic therapy, instrumentation and irrigation, inter-ap- pointmentmedicaments,permanentrootfilling,and coronal restoration) can alone guarantee complete disinfection, it is of utmost importance to aim for the highest possible quality at every phase of the treatment. In the classic study by Sjogren et al., 55 single- rooted teeth with apical periodontitis were instru- mented and irrigated with sodium hypochlorite and root filled. Peri-apical healing was followed-up for five years. Complete peri-apical healing occurred in 94% of cases that yielded a negative culture. In cases in which the samples were positive prior to root filling, the success rate of treatment was just 68%—a statistically significant difference. These findings emphasise the importance of eliminating bacteria from the root-canal system prior to obtura- tion. This objective cannot be reliably achieved in a one-visittreatmentofnecroticpulpsbecauseitisnot possibletoeradicateallinfectionfromtherootcanal withoutthesupportofaninter-appointmentantimi- crobial dressing.25 Sodium hypochlorite (NaOCl) is the most widely used irrigating solution. It is a potent antimicrobial agent and lubricant that effectively dissolves pulpal remnants and organic components of dentine, thus preventingpackinginfectedhardandsofttissueinto the apical confines. Hypochlorous acid (HClO) is the active moiety responsible for bacterial inactivation. NaOCl is used in concentrations varying from 0.5 to 5.25%; the in vitro and in vivo studies differ signifi- cantly in terms of the effectiveness of the range of concentrations as invitroexperiments provide direct access to microbes, higher volumes are used and the chemicalmilieucomplexityofthenaturalcanalspace are absent as compared to in vivo experimentation. Siqueira et al. found no difference (invitro) between 1%, 2.5% and 5% NaOCl solutions in reducing the number of bacteria during instrumentation.26 What has been demonstrated is that the tissue dissolving effects are directly related to the concentration used.27 PerhapsthemostmisunderstoodaspectofNaOCl irrigation is the need for the quantities of irrigation required due to the morphological and anatomical variations in the volumetric size of the root-canal anatomy. Siqueira et al. demonstrated that regu- lar exchange and use of large amounts of irrigant should maintain the antibacterial effectiveness of the NaOCl solution, compensating for the effects of concentration.28 Fig. 6_All CBCT units provide correlated axial, coronal and sagittal multiplanar volume reformations. Basic enhancements include zoom or magnification and visual adjustments to narrow the range of gray scale, in addition to the capability to add annotation and cursor-driven measurement. Fig. 7_Strategic extension of the access perimeter is too often undervalued in terms of successful endodontic treatment outcomes. The shape of the chamber must be regressed to its native state to ensure that axial interference is negated as an instrument traverses the length of the root-canal space. Fig. 8a_Dystrophic calcification confoundseventhemostexperienced clinician. The key to identification of the orifices is to regress the inner space using the continuum, cusp tip, pulp horn and canal orifice. In lieu of an ultrasonic tip, which tends to chop the stone and scatter debris, gross removal is best done with a diamond bur in a high-speed handpiece. The fine removal of residue can be done with a multi-fluted carbide bur to trace the fusion lines. Fig. 8b_Keeping the chamber wet with alcohol improves optics and highlights colour disparities. The most important tool for orifice identification in addition to dyes is a micro-etcher. The satin finish produced highlights the disparity betweenthenaturaltoothstructureof the floor and the secondary and tertiary dentine of the calcified orifice. roots1_2010 Fig. 6 Fig. 7 Fig. 8a Fig. 8b

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