The importance of working length
Grove (1930) stated that ‘the proper point to which
root canals should be filled is the junction of the dentin
and the cementum and that the pulp should be severed
at the point of its union with the periodontal membrane’.
The cementodentinal junction (CDJ) is the anatomical and histological landmark where the periodontal
ligament begins and the pulp ends. Root canal
preparation techniques aim to make use of this
potential natural barrier between the contents of the
canal and the apical tissues (Schilder 1967). It is
generally accepted that the preparation and obturation
of the root canal should be at or short of the apical
constriction. An in vivo histological study found that
the most favourable histological conditions were when
the instrumentation and obturation remained short of
the apical constriction and that extruded gutta-percha
and sealer always caused a severe inflammatory
reaction despite the absence of pain (Ricucci & Langeland
1998).
The problem clinicians face is how to accurately
identify and prepare to this landmark – the ‘working
length’ – and achieve maximum success. Epidemiological
studies have reported that the best prognosis is
when the root filling lies within 2 mm of the radiographic
apex (Sjo¨gren et al. 1990). The variations in
anatomy of tooth apices both by age and tooth type
make this task all the more challenging.