Non-surgical endodontics: contemporary biomechanical preparation of the root canal system

Abstract

Treatment of apical periodontitis requires disinfection of the root canal system through means of biomechanical preparation. This is achieved by a process of shaping the root canal space while simultaneously using antibacterial agents to reduce microbiological load in the root canal system in order for inflammation of the periradicular tissues to resolve and the body to heal itself. The fundamental principles underlying this process have not changed in decades; however, in contrast, the armamentarium available to the clinician continues to evolve rapidly. Nickel-titanium file design has made a significant step forward in the last ten years. Areas of development have focused on the metallurgic properties, motion of the instrument and cross-sectional design. The resulting contemporary designs have allowed the clinician to manage more complex root canal systems more predictably in situations which would otherwise have proved difficult using conventional techniques; effectively, it has made it easier to prepare a root canal. These newer systems also require fewer instruments to prepare a canal and some, which have adopted a reciprocating (rotational) motion, may only require one engine-driven file. Significant energy has been devoted to attempting to enhance efficacy of irrigant activity using different techniques. Although this has shown promise in in vitro studies, this has yet to be shown to translate to an improved clinical success rate based on comparative clinical studies performed. Contemporary biomechanical techniques used to clean and shape the root canal system should result in improved confidence and predictability when managing endodontic disease.

Fig. 1

a) Preoperative periapical radiograph of left maxillary first molar with symptomatic apical periodontitis. b) Postoperative radiograph showing root canal treatment achieving technical operative factors determined by Ng et al. 2008 which significantly improve the outcome of primary root canal treatment. Case displayed was carried out by Shruti Panchani (undergraduate student at Birmingham School of Dentistry)

Fig. 2

Biofilm located in the isthmus between distal buccal and lingual canals of a mandibular first molar seen under operating microscope during retreatment procedure

Fig. 3

Burs designed for radicular access (top to bottom): Protaper Next XA and X-gates

Fig. 4

a, b, c) Developing straight line access - the process of removing coronal and radicular dentine (coronal third) in order to prevent deflection of the file from a straight path until it penetrates deeper into the canal. File is deflected by coronal and radicular third dentine highlighted in panels b and c. This dentine is removed and the file passes deep into the canal along a straight path without deflection (image reproduced with permission from the British Endodontic Society)

Fig. 5

Photograph of root-end of extracted tooth with small file through the foramen, demonstrating the foramen can be distant from the tip of the root (radiographic apex)

Fig. 6

WaveOne Gold primary (25, 0.07) instrument is pre-curved off central axis without permanent deformation due to reduced shape memory compared to conventional NiTi instruments

Fig. 7

ProTaper Next file design with rectangle off-set cross-section along its length which results in only two points of engagement (red arrows). In principle, this creates space for debris to be driven coronally when in motion

Fig. 8

Postoperative periapical radiograph of root treated upper left first molar showing a ‘skinnier' style of preparation than previously produced

Fig. 9

Various safe-ended irrigation needles that direct fluid flow laterally from the needle end and dissipate fluid pressure to help avoid rapid expulsion of the fluid in what would be an apical direction when in the canal (image reproduced with permission from the British Endodontic Society)

Fig. 10

Summary of manual and appliance assisted techniques irrigant enhancement methods