preparation. The open and often diverging apices of immature permanent teeth create
technical difficulties for the controlled condensation of root filling materials, and a
root end closure (apexification) procedure is usually required to produce an apical
calcific barrier against which filling materials may be packed (697HFig. 12.21). The most
important pre-condition for calcific barrier formation is the elimination of micro-
organisms from the root canal system by thorough canal debridement and the long-
term application of a non-toxic, antimicrobial medicament such as non-setting
calcium hydroxide.
Traditional root end closure of this sort may take 9-24 months before definitive canal
obturation and restoration is possible.
Operative procedure (698HFig. 12.22)
- Access with a high-speed, medium tapered fissure bur. In the pulp chamber use
safe-ended burs to remove the entire roof without the danger of overcutting or
perforation. - Remove loose debris from the pulp chamber with hand instruments, accompanied
by copious, gentle irrigation with sodium hypochlorite solution (1-2%). - Gates Glidden drills may be used to improve access to canals for instruments and
irrigant. They should not be used deep in the canals of immature teeth where they may
overcut and create a strip perforation. - Canal preparation involves two processes: cleaning with irrigants to free the root
canal system of organic debris, micro-organisms and their toxins; and shaping with
enlarging instruments, to modify the form of the existing canal to allow the placement
of a well-condensed root filling. In canals which are often as wide as this, little
dentine removal and shaping is needed. Sodium hypochlorite solution (1-2%) as an
irrigant will continue dissolving organic debris and killing micro-organisms deep in
the canal. - Working apically, files are directed around the canal walls with a light rasping
action to remove adherent debris. Instrumentation is frequently punctuated by high-
volume, low-pressure irrigation to flush out debris. - Irrigant is delivered either by pre-measured, 27 gauge needle and syringe or with the
aid of sonic/ultrasonic energy. The latter involves flooding the canal with irrigant
before inserting a small (size 16-20) file attached to a sonic/ultrasonic unit to stir the
irrigant in the canal. Wall contact with the file should be avoided, as the action is
liable to cause turbulence in the irrigant which scrubs the walls of debris. - Provisional working length should be 2-3 mm from the radiographic apex, estimated
from an undistorted pre-operative periapical film. A working length radiograph is then
taken to establish a definitive working length 1 mm short of the radiographic root
apex. Further gentle filing and irrigation is then continued to the definitive working
length. - Dry canal with pre-measured paper points to avoid inadvertent over-extension and
damage to the periapical tissues. - Fill canal with a relatively fluid proprietary calcium hydroxide paste such as
Ultracal (Optident, UK. This may be syringed into the canal via a disposable flexible
tip (699HFig. 12.22 (d)) or alternatively spun into the canal with a spiral paste filler. The
antimicrobial and mild tissue solvent activity of non-setting calcium hydroxide will
continue to cleanse the canal, and its high pH is believed to encourage calcific root