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4.2.4 A X-Ray photo to show the whole length and the root canal of the teeth.
4.2.5 The endo file should not be too big nor too small to avoid cutting
through the apical foramen.
4.2.6 Mark an anatomized symbol on the diseased tooth and memorize it on
the case history. This symbol should be marked on the health bridge or on the
tooth filed integrated. The position of the mark should be on the incisal edge of the
anterior tooth or on the spire of the molars. For those bridge that’s broken
obviously. This symbol should be on the tooth surface supported by the dentin
instead of on the suspended enamel.
4.2.7 The acute inflammation surrounding the apex has been gone and the
infected material has been cleaned. It is also necessary to get rid of the pulp and
necrosis tissue.
4.2.8 The following cases are not suited for a normal measurement：
a) The size of the root similar to the size of apical foramen
In this case, the measurement result of the length of the root canal will be
shorter（than its real because of the hypoplasia of the root.（Pic 10）
b）Bleeding or the blood overflow from the apical foramen
In this case, the blood will overflow from the root canal and reaches gingival
that the blood and the gingival will be on a conducting state which will cause an
inaccurate result while measuring. The measurement can be continued when the
bleeding is stopped.（Pic 11）
c）The tooth crown is broken
The tissue of the gingival may reach the cavity of the endo hole at the broken
point which will cause inaccuracy because of the electronic conduction. The
measurement can be continued when the crown is fixed by gypsum or other
insulators.（Pic 12）
