Comparison of First Accessory Cone Penetration after Using Stainless-Steel and Ni-Ti Spreaders in Curved Resin Blocks.

0.16 MB·English

by  Mohammadzade Akhlaghi, Nahid

ORIGINALARTICLE
Comparison of First Accessory Cone Penetration
after Using Stainless-Steel and Ni-Ti Spreaders in
Curved Resin Blocks
Nahid Mohammadzade Akhlaghi1*,Nasrin Roghanizad1,Zohreh Khalilak1,
NedaRezaie2
1.DepartmentofEndodontic,DentalSchoolofIslamicAzadUniversityandIranianCenterforEndodonticResearch,Tehran,Iran
2.GeneralPractitioner,Tehran,Iran
ABSTRACT
INTRODUCTION: The purpose of this study was to compare first accessory gutta-percha
penetration after the use of nickel-titanium (Ni-Ti) or stainless-steel spreaders in curved resin
blocks.
MATERIALS AND METHODS: Forty resin blocks with 30º and 45º curvatures (20 blocks for
each) werepreparedand#30masterconeswereplacedincanals.Inpartone, under20Newton
pressure, Ni-Ti or stainless-steel spreaders were placed alongside the master cone and their
penetration was measured witha millimeter ruler. Inparttwo, after removingthe spreader, one
of the accessory cones (#15, #20 or MF) was substituted in the canal and its penetration was
measured.TheMann-UWhitneytestwasusedforthefinalevaluation.
RESULTS: In both curvatures, the penetration of Ni-Ti spreaders were significantly more than
stainless-steelspreaders(p<0.005).Penetrationofthefirstaccessorycones(#15andMF)inNi-
Ti spreader group were also significantly more than stainless-steel group (p<0.05) (in both
curvaturegroups).
CONCLUSION: This study showed that Ni-Ti spreaders and #15 accessory cones penetrated
deeper incurved canalsthan stainless spreadersand #15 accessorycones. Therefore, the use of
NiTispreaderinlateralcondensationtechniqueissuggestedforbetterresults.
Keywords:Gutta-Percha;Nickel-Titanium;RootCanalObturation;Stainless-Steel
Received:24Jan2007;Revised:07Jun2007;Accepted:19Aug2007
*Correspondingauthorat:NahidMohammadzadeAkhlaghi,DepartmentofEndodontics,DentalSchoolofIslamic
Azad University, Number 3, 10th Neyestan St., Passdaran Ave., Tehran, Iran. Tel: [phone], E-mail:
[email protected]
INTRODUCTION canals (8). This might be addressed to the
inflexibility of stainless steel spreaders that in
Placement of endodontic spreaders alongside turn leads to an inadequate apical seal (2) and
the master cone to the depth of 0.5 to 1 wedging effect of the spreader that may cause
millimeter short of the workinglengthhas been root fracture, if the operator attempts to force it
advocated for optimum obturation. The to the proper length (9). Sobhi and Khan (10)
accessory cones should be placed to the same reported significantly deeper penetration of
length as the penetration of spreader; to obtain nickel-titanium (Ni-Ti) finger spreaders than
favorable void less obturation (1-2). Studies the SS spreaders. Also they showed easer
have shown that the lateral condensation penetration of NiTi finger spreader than the SS
technique provides an excellent apical seal (3- spreaders especially in curved canal. Berry et
4). al. (8) showed that no statistically significant
However, in curved canals the results of this difference in penetration of two types of
technique will not be predictable (5-7). This spreaders was found in straight canals. As the
may be due to inadequate condensation of canal curvatures increased the penetration of
gutta-percha (GP) because of inability of SS spreader was decreased. But the ability of
stainless-steel (SS) spreaders to penetrate to NiTi spreader to approach the apex was not
within 1 mm of the working length in curved affected by an increase in root canal curvature.
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Akhlaghietal.
Willson and Bumgarthner (11) reported no of ten blocks in each. In part one #25 (B/0.02)
significant difference between Ni-Ti and SS SS or Ni-Ti finger spreaders (Maillefer
spreader penetration using 0.02 tapered gutta- Densply, Ballaigues, Zwitzerland) were put
percha in small canal curvature of (0 to 20 alongside the master gutta-percha cone and
degrees). Both Ni-Ti and SS spreaders remained for 5 sec in canals under 20 Newton
penetrated to a greater depth as canal (~2 kg) pressure applied byan Instron machine
curvaturesincreasedtogreaterthan20degrees
(Instron Corp., Canton, ME, USA). Spreader
(11). Schmidte et al. (2) showed that the
penetration was measured by a millimeter ruler
average depth of penetration of a Ni-Ti
calibrated in 0.5 mm increments. In part two,
spreader with conjugation of a master gutta-
all of the resin blocks were used three times.
percha cone when using a standardized 1.5 kg
Each time after removal of spreaders, one of
force was significantly greater than that for a
the 0.02 tapered accessory cones #15, #20 or
SS spreader. But, when the differences
conventional MF accessory gutta-percha cone
between depth of spreader and accessory cone
(Diadent, Burnaby, B.C., Canada) was put
penetrationcompared; there was no significant
alongside its master cone and the penetration
difference between the Ni-Ti and SS
was measured in each group. The results were
spreaders. Several studies have shown that the
compared and evaluated by Mann-U Whitney
size of the accessory cones relative to the
spreader size has been a noticeable problem test.
(12-14). To eliminate confusion in sizing,
Hartwell et al. (12) successfully urged that RESULTS
spreaders be manufactured in standardized
sizes. Five resin blocks (two of 30º curvature groups
The purpose of this study was to compare first and three of 45º curvature groups) were
accessory cone penetration after using Ni-Ti or discarded because of file breakage and canal
SSspreadersincurvedcanalsofresinblocks. obstruction. The average working length of the
canalswas16.8mm.
MATERIALSANDMETHODS In part one of the study, comparison of SS and
Ni-Ti finger spreader penetration alongside the
Forty resin blocks with 30º and 45º curvatures master gutta-percha cone showed that in both
were used in this study. Canals were prepared 30º and 45º curvatures Ni-Ti spreaders
using Passive Step Back technique (15) by K- penetrated significantly further than SS
Flexofiles (Maillefer Dentsply, Ballaigues, spreaders (p<0.005). With regard to the
Switzerland). curvature of the canals, both spreaders'
First, canal length was determined by a #10 K penetration was more in 30º curvatures
file (Maillefer Dentsply, Ballaigues, compared with 45º curvatures. However, the
Switzerland). The working length (WL) was difference was only significant in the SS
established 1 mm shorter than the canal length. spreader group, but not significant for the Ni-Ti
After pre-flaring by GG #2, 3 canals were spreadergroup(Figure1).
prepared within WL to #30 master apical file Part two of the study showed accessory cone
(MAF)andflaredbyGG#2,3andstepbackto #20 penetrated less than #15 and MF accessory
K-file #45 with 1 mm increments. After conesineitherspreaderorcurvedgroupsOnthe
removing each file or GG drill, 2 mL of saline other hand #15 and MF first accessory cone
was used for irrigation. Canal patency was penetrated significantly more in the Ni-Ti
checked by #10 file. After finishing the canal spreader group (p<0.05). Number 20 cones
preparation, #30 GP cone with 0.02 tapered also penetrated farther in the Ni-Ti spreader
(Diadent, Burnaby, B.C., Canada) was placed group, but the differences were not significant
inthecanaltotheWL. (Table 1).
Resin blocks were divided into two In the SS spreader group both #15 and MF
experimental groups 30º and 45º curvatures cones penetrated significantly more in a 30º
twenty blocks of each. Each of these two curvature compared to the 45º curvature
groupswasclassifiedintoSSandNi-Tigroups (p<0.005). In the Ni-Ti spreader group, the
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Accessoryconepenetration
and wider preparation in curved canals
comparedtostraightcanals.
Dulaimi and Wali (16) also concluded that
space prepared by flaring the canal will affect
the amount of spreader penetration. Berry et
al. (8) reported no significant difference
between SS and Ni-Ti spreader penetration in
straightcanals.
In the second part of the present research, it
was realized that the penetration of accessory
cones in the Ni-Ti spreader groups was further
than SS spreader groups. This was unlike the
Figure1. ComparisonofSS/Ni-Tispreaderpenetration results of Schmidt et al. (2) which showed no
in30ºand45ºcurvatures significant difference between first accessory
cone penetration in both spreader groups. In
Table 1. Comparison of first accessory cone penetration their study, a #35 file was chosen as the master
after using Ni-Ti/SS finger spreaders in 30º and 45º apicalfile.Canalswereobturatedusing#30Ni-
curvedcanals(mean±SDinmm) Ti/SSspreadersand#25accessorycones.
30º 45º The size of the accessory cones relative to the
GP
SS Ni-Ti SS Ni-Ti
spreader size has been discussed and shown in
15 16.1±0.5 16.4±0.5 15.6±0.4 16.1±0.4
several studies to be a significant problem (12-
20 15.5±0.7 15.8±0.6 15.1±0.5 15.1±0.6
MF 16.1±0.6 16.4±0.4 15.4±0.5 16.0±0.4 14). Hartwell et al. urged that spreaders be
madeinstandardizedsizes(12).
penetration of the first #15 accessory cones in According to the present study, accessory cone
both curvatures was not significantly different penetrationin30ºcurvatureswasmorethanin45º
(p>0.05). curvatures. The penetration of #15 or MF
accessory cones, in both spreader groups and
DISCUSSION curvatures, was further than that of #20 cones.
SincethetaperingofMFaccessoryconesarenot
According to the results of this study, adjustedwith0.02taperingof handfiles it seems
penetration of Ni-Ti spreaders in both 30º and that the use of MF accessory cones will cause
45º curvatures was significantly more earlyobturationofcoronalpartofthecanal.
compared with SS spreaders. This is similar to
the results of Sobhi and Khan (10), Schmidt et CONCLUSION
al. (2) and also Wilson and Baumgartner
studies (11). Regardless of the degree of This in vitro study showed that Ni-Ti spreaders
curvature, all of them found that Ni-Ti and #15 accessory cones penetrated further in
spreaderspenetratedfurtherintothecanal. curved canals. Therefore, their use in the lateral
The present study also found that Ni-Ti condensation technique is suggested for better
spreader penetration in both curvatures was results.
similar, while SS spreader penetration was
influencedbythedegreeofrootcurvature. ACKNOWLEDGEMENT
This result was the same as the findings of
Berry et al. (8). Sobhi and Khan (10) also The authors wish to thank Mr. Mirkarimi for
found that an increase in the canal curvature hishelponstatisticalanalysisinthisstudy.
will reduce the ease of spreader penetration.
However, Wilson and Baumgartner (11)
ConflictofInterest:‘Nonedeclared’.
showed that penetration of Ni-Ti and SS
spreadersincurvaturesunder20ºwerelessthan
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