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Apicectomy with retrograde filling is a well-established
technique to treat tooth with persistent periapical infections
in which conventional root treatment is not accessible. A root-
end filling material is often placed to prevent the egress of
irritants into the periradicular tissues. Unfortunately, no
materials can fulfill all the requirements of ideal retrofilling
material. The main reason of failure of apical surgery is due
toun-hermetic seal. Microleakage can occur at the apex with two
avenues. The first is by apical microleakage alone the interface
between the filling material and the canal wall.The second way
is by the flow of fluids and substances along the opening
tubules at the resected root end.The purpose of this in vitro
study was to investigate the effect of Nd:YAG laser on the
adaptation and the apical seal following apicectomy and
retrograde filling with amalgam and light curing glass ionomer
cement respectively. By the way,the permeability ofdentinal
tubules in the resected root bevel under the irradiation of Nd:
YAG laser is also been evaluated.One hundred and five extracted
human single canal teeth were selected and prepared as the
conventional methods.Expect for the control(10 teeth)and
observation(5 teeth)group,the other teeth were randomly assigned
to 6 group of 15 teeth.The six groups were arranged in three
pairs,laser and unlaser groups.The apical 2mm of teeth from
group1 to group4 were resected.A class I cavity(diameter 1.5mm&
2.0mm in depths).The retrograde cavity of resected roots in half
of the sample in each pair was lased by using Nd:YAG (6W,50pps)
laser.After that,light curing glass ionomer cement was
retrofilled in group1 &group2 and amalgam was retrofilled in
group3 and group4.The apices of all the roots within group5 and
group6 were resected at 45 degrees with respect to the long axis
of the tooth(commencing lingually 1mm from the anatomical apex).
The resected roots in group5 was also lased by using Nd:YAG
laser.The duration of lasing was judged with the cleanliness of
the residual chinese ink.An electrochemical method was used to
evaluate the apical seal and permeability on the resected root
end.After application of 2 layers of nail polish to the
unoperative surfaces of each tooth(including the whole tooth of
positive control group),then,all species were immersed in 1%
potassium chloride solution.If leakage occurs,the solution will
penetrate through the apical seal and reach copper wire placed
through the coronal opening into the canal.A potential of 12V
was applied between each specimen and the graphite rod and
measurement of the current flow were obtained at 24 hour
intervals for approximately 30 days.After analyzing the data
statistically,we found that the microleakage of the laser-
treated and retrograde glass ionomer group(group1)is
significantly less than the other threes.There are no
differences between the retrograde amalgam group whether the
laser-treated or not(group3 and group4).Also it is important
that the permeability of laser-treated root end was
significantly less than untreated specimens.In qualitative
observation,resolidification and recrystalization of the melted
areas appeared to be incomplete and discontinuous over the
resected laser-treated root end.As for the retrograde cavity,
irradiation of laser can result in a cutting-like surface and
created a beneficial enviroment for glass ionomer cement to
adaptation and adhesion.Moreover,wesuggest that combining laser-
treated and light curing glass ionomer filling can reduce the
microleakage and permeability over the resected roors.
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