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Surgical endodontic therapy is usually necessary when the conventional retreat
ment is ineffective or impossible. Due to the bulky instruments and limited wo
rking space during surgery, most cavities prepared with traditional techniques
and instruments do not meet the ideal characteristics of root-end preparation
as recommended by Arens et al. who advocated that an ideal root-end preparati
on should be parallel to the long axis of the root, 3 mm deep, centered in the
root throughout its depth.Recently, sonic and ultrasonic instruments speciall
y designed for root-end preparation have been introduced. Despite the advantag
es mentioned, recent studies showed a higher risk of crack formation on the re
sected surface after sonic and ultrasonic root-end preparations. However, litt
le work available focus on their relevance between the effects and new root-en
d preparation techniques in a special site. Therefore, the primary aims of thi
s investigation were (1) to evaluate the cleanliness of root-end preparation o
n the canal and isthmus areas under a scanning electron microscope (2) to cali
brate the quality of root-end preparation on the canal and isthmus areas with
the aid of a stereomicroscope and image processing system (3) to measure the r
oot deformation during root-end preparation by use of the strain gauge methods
.Based on the results from this study, the conclusions were as follows:1. The
EIE ultrasonic root-end preparation may produce a relatively uniform and cons
ervative cavity preparation In addition, it could create a cleaner dentinal s
urface with the less amounts of debris and smear layer. However, there was a h
igher incidence of crack formation in the treatment of an isthmus (30%) in thi
s study. Also, the EIE system produced the greatest strain on the root among t
hree root-end preparation techniques.2. The cavities prepared with the microha
ndpiece system were irregular and the larger than those prepared with the EIE
system. Root perforation was noted at the most invaginated area (30%). As for
cleanliness, the cavities created by microhandpiece system showed significantl
y less debridement than those by EIE system. Despite this, the strain generate
d was far lower than that created by EIE system.3. Gouging the root-end surfac
e was often observed under the sonic root-end preparation. However, the strain
created by this system was lower than that generated by microhandpiece system
on the root in this study.
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