Medical

Communication

Biosci. Biotech. Res. Comm. 10(3): 571-579 (2017)

Area-metric analysis of the quality of obturation of

four different techniques: An ex vivo study

Yazdan Shantiaee

, Setareh Rostami

, Shiva Shojaeeian

and Sanaa Jabbari

Associate Professor, Dental School of Shahid Beheshti University of Medical Sciences, Tehran, Iran

Dentist, Shahid Beheshti University of Medical Scineces, Tehran, Iran

Assistant professor, Department of Endodontics, Dental school of Shahid Beheshti University of Medical

Sciences, Tehran, Iran

Post Graduate Student, Department of Endodontics, Dental School of Shahid Beheshti University of Medical

Sciences, Tehran, Iran

ABSTRACT

The aim of this study was to compare different obturation techniques in straight canals in term of the percentage of

gutta-percha  lled area (PGFA) and percentage of sealer  lled area (PSFA) and voids. The obturation time was also

compared. Straight root canals of 40 extracted human premolars were instrumented with Mtwo rotary  les and  lled

as follows: Control: cold lateral compaction with standard master and accessory cones. CLS group: cold lateral com-

paction with 0.04/35 master cone and standard accessory cones. CLNS group: cold lateral compaction with 0.04/35

master cone and non-standard medium- ne (MF) accessory cones. WLS group: warm lateral compaction with 0.04/35

master cone and standard accessory cones. AH26 sealer was used. The teeth were sectioned horizontally at 3, 6 and

9 mm from the apex. The total area of each section and the PGFA, PSFA and percentage of voids were calculated.

Data were analyzed using repeated measures ANOVA and Kruskal-Wallis test.The CLNS was the fastest method with

a signi cant difference with the control group (P<0.05) while WLS required signi cantly more time than all other

techniques (P<0.05). In the apical and coronal thirds, CLNS yielded signi cantly lower PGFA (P<0.05). In the middle

third, WLS yielded signi cantly higher PGFA than CLNS (P<0.05). Cold lateral compaction using gutta-percha master

cone with 4% taper and MF accessory cones is not ef cient for obturation of canals. Also, warm lateral compaction

has no superiority to cold lateral compaction in straight canals.

KEY WORDS: COLD LATERAL CONDENSATION, SEALER, WARM LATERAL COMPACTION, OBTURATION, GUTTA-PERCHA

571

ARTICLE INFORMATION:

*Corresponding Author: Sanaa_jabbari@yahoo.com

Received 12

July, 2017

Accepted after revision 27

Sep, 2017

BBRC Print ISSN: 0974-6455

Online ISSN: 2321-4007 CODEN: USA BBRCBA

Thomson Reuters ISI ESC and Crossref Indexed Journal

NAAS Journal Score 2017: 4.31 Cosmos IF: 4.006

reserved.

Online Contents Available at:

http//www.bbrc.in/

DOI: 10.21786/bbrc/10.3/35

572 AREA-METRIC ANALYSIS OF THE QUALITY OF OBTURATION OF FOUR DIFFERENT TECHNIQUES BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Yazdan Shantiaee etal.

INTRODUCTION

Achieving a hermetic apical, lateral and coronal seal is

an important factor to prevent entry of microorganisms

into the canal and periapical tissues, and depends on

proper cleaning and shaping and ef cient obturation

of root canal system (Wu etal. 1993; Mollander etal.

1998; Schafer etal. 2012). Advances in formulations of

root canal irrigating solutions and rotary devices have

greatly enhanced proper cleaning and shaping of root

canal system. Homogenous, three-dimensional  lling of

root canal space by gutta-percha and sealer can greatly

increase the success of endodontic treatment (Wu etal.

2002). Gutta-percha cones must be compacted next

to each other with a very thin layer of sealer between

gutta-percha cones and canal wall to minimize voids

(Gordon et al. 2005). Gutta-percha dimensions do not

change over time (Wu etal. 2009) but sealer undergoes

shrinkage and dissolution (Al-Hadlaq etal. 2010; Nica

etal. 2012). Following dissolution of sealer over time,

voids are created in the canal, which can compromise

the seal and enable entry and accumulation of micro-

organisms and subsequent development of periapical

lesions and eventual treatment failure (Jarret etal. 2004;

Schafer etal. 2012).

If the volume of gutta-percha mass compared to that

of sealer increases, less voids will be created over time

and coronal and apical seal will not be compromised.

This would increase success of endodontic treatment

(Kazemi etal. 1993; Kontakiotis etal. 1997; Wu etal.

2009). A systematic review reported that canals  lled

with adequate, homogenous gutta-percha mass showed

primary endodontic success (Ng et al. 2008). Another

study reported that homogeneity of gutta-percha mass

had a signi cant positive effect on periapical health and

success of endodontic treatment (Lee etal. 2012).

Root canal  lling length should be equal to the work-

ing length to ensure that the entire prepared space is

 lled with gutta-percha (Kojima etal. 2004; Schaeffer

etal. 2005). Thus, maximum penetration of master and

accessory gutta-percha cones must be ensured. The taper

of master and accessory gutta-percha cones is an impor-

tant factor affecting the penetration depth of gutta-per-

cha into the canal such that the greater the compatibil-

ity of taper of gutta-percha with that of root canal, the

more homogenous and regular their arrangement would

be in the canal. Some authors believe that using a single

gutta-percha cone that matches the taper and size of

prepared canal would have the best adaptation to canal

walls (Whitworth, 2005; Schafer etal. 2013).

Several methods have been suggested for root canal

obturation such as lateral compaction, vertical con-

densation, single-cone obturation with a gutta-percha

cone that matches the size and taper of prepared canal

(Schafer et al. 2012), use of a solid core covered with

gutta-percha, injection of soft, plasticized gutta-percha

into the canal and use of physically and chemically

modi ed gutta-percha with higher adaptation (Skinner

etal. 1987; Whitworth, 2005; Schafer etal. 2013). Each

of these techniques has its own advantages and disad-

vantages, and no consensus has been reached on the

superiority of one technique over the others (Aqrabawi

etal. 2006; Ng etal. 2007).

Lateral compaction is a commonly used root canal

obturation method due to its simplicity (Cailleteau etal.

2009). This technique can be practiced in most clinical

situations and enables length control during compac-

tion (Gilhooly etal. 2001). However, its main drawback

is that it cannot create a homogenous mono-block of

gutta-percha. Master and accessory gutta-percha cones

are placed next to each other but remain separate and

the space between cones is expected to be  lled with

sealer, which undergoes shrinkage and dissolution over

time. In thermoplastic methods such as warm vertical

condensation and warm lateral compaction, heat is used

to cause physical changes in gutta-percha and increase

its plasticity and adaptation to the canal walls. Warm

lateral compaction allows length control and at the same

time, heat results in adherence of gutta-percha cones

to each other and formation of a solid mass (Jacobsen

etal. 1993).

Considering the need for decreasing working time in

dental of ce, gutta-percha cones with 4% and 6% tapers

and non-standard medium  ne (MF) and  ne- ne gutta-

percha cones were introduced to the market for faster

obturation of root canals. However, deep penetration

of accessory cones with greater taper is dif cult. Stud-

ies on penetration depth of spreader alongside a master

cone with 2% taper and master cones with higher than

2% taper showed greater penetration depth of spreader

next to master cone with 2% taper (Bal etal. 2001; Wil-

son etal. 2003). Thus, complete penetration of accessory

cones to the working length and obtaining an apical seal

with the use of these gutta-percha cones is a matter of

debate. This study has aimed to assess the quality of root

canal  lling by measuring the percentage of gutta-percha

(PGFA) and sealer  lled areas (PSFA) and voids in use of

four different obturation techniques. Duration of obtura-

tion was also compared among the four methods.

MATERIAL AND METHODS

This in vitro, experimental study was conducted on

40 single-canal maxillary and mandibular premolars

with straight canals. The teeth were randomly divided

into four groups (n=10). The highest mean difference

expected for PGFA among the groups was considered to

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS AREA-METRIC ANALYSIS OF THE QUALITY OF OBTURATION OF FOUR DIFFERENT TECHNIQUES 573

Yazdan Shantiaee etal.

be 0.13 with a standard deviation of 14% according to a

study by Schafer etal. in 2012. Considering 80% power

of study and type one error of 5%, sample size was cal-

culated to be 10 in each group.

The inclusion criteria were single-rooted premolar

teeth extracted for orthodontic or periodontal reasons

with a straight canal and one apical foramen and no

visible root caries, no fracture or crack and no internal/

external root resorption or calci cation on radiographs.

The teeth had mature apices.

The exclusion criteria were presence of voids after

 lling and incorrect working length. Teeth with no api-

cal constriction or fracture during cleaning and shap-

ing were also excluded. After collection, the teeth were

immersed in 3% sodium hypochlorite solution (Rakh-

shan, Tehran, Iran) at room temperature for two days.

Calculus (if any) was removed using a universal curette

(Hu-Friedy, USA) and the teeth were evaluated under a

stereomicroscope (SZX9; Olympus, Tokyo, Japan) at 20

magni cation to ensure absence of root cracks. Paral-

lel periapical radiographs were obtained in mesiodis-

tal and buccolingual dimensions to assess root canal

anatomy. After access cavity preparation using 836  s-

sure and 801 round burs (SWS, Switzerland), a #15 K

 le (Mani, Tokyo, Japan) was introduced into the canal

until its tip was visible at the apex. The teeth were then

radiographed and canal curvature was determined. The

selected 40 teeth had straight canals and #20 K  le was

the largest initial  le compatible with their root canal.

The crowns were then cut at the cementoenamel junc-

tion using a diamond disc (D & Z, Germany).

To determine the working length, a #15 K  le (Mani,

Japan) was introduced into the canal such that its tip

was visible at the apex; working length was determined

1mm short of this length. All canals were cleaned using

#15 and #20 K  les (Mani, Japan) and then by Mtwo

rotary NiTi  les (VDW, Germany) with an endodontic

motor (NSK, Japan) with slow pull and push brushing

motion to the working length as recommended by the

manufacturer in the following order: 0.04/10, 0.05/15,

0.06/20, 0.06/25, 0.05/30, 0.04/35. A #10 K  le (Mani,

Japan) was used after each rotary  le for patency and

17% EDTA gel (Calasept, Nordiska Dental) was used

as chelator. Root canals were rinsed with 2cc of 1.5%

sodium hypochlorite (Rkhshan, Tehran, Iran). Smear

layer was removed by rinsing the canals with 5cc of

17% EDTA for one minute followed by a  nal rinse with

saline. The root canals were dried with paper points (Ari-

adent, Tehran, Iran) and the teeth were randomly divided

into four groups of 10 and  lled with AH26 sealer (Dent-

sply DeTrey-Germany) and gutta-percha (Metabiomed,

Korea) as follows:Control group: #35 standard gutta-

percha (2% taper) as master cone and standard accessory

cones were used in cold lateral compaction technique.

CLS groups: #35 standard gutta-percha (4% taper)

as master cone and standard accessory cones were used

in cold lateral compaction technique (cold lateral com-

paction with standard gutta-percha).CLNS group: #35

standard gutta-percha (4% taper) as master cone and

non-standard MF accessory cones were used in cold lat-

eral compaction technique (cold lateral compaction with

non-standard gutta-percha).WLS group: #35 standard

gutta-percha (2% taper) as master cone and standard

accessory cones were used in warm lateral compaction

technique (warm lateral compaction with standard gutta-

percha).Root canal  lling with cold lateral compaction

technique was done as follows: Following root canal

preparation and drying, a standard gutta-percha cone

with 2% taper was used in the control group and with

4% taper in the CLS group to the working length. Api-

cal third of master cone was dipped in sealer and placed

into the canal, rotated in counter clockwise fashion and

removed. A proper size spreader was also selected based

on canal taper to reach 1mm of the working length with

master cone in the canal. Accessory cones were placed

and cut at the ori ce. No pressure was applied for verti-

cal condensation.

Cold lateral compaction in CLNS group was the same

as in the control and CLS groups with the exception of

4% taper of master cone and selected spreader. Also, non-

standard MF accessory cones were used. In WLS group,

the same procedures were followed with the exception

that after placement of master cone with 4% taper, the

thinnest tip of Obtura (E & Q Master Meta Biomed-Korea)

that could reach 2-4mm of the apex adjacent to master

cone was chosen and inserted as deep as possible into

the canal. After removal, #25  nger spreader was placed

adjacent to the heated master cone, removed immediately

and replaced with an accessory cone with 2% taper. This

process was repeated until complete obturation. Time

required for obturation of each canal was also calculated

from the time of placement of the  rst gutta-percha to

completion of obturation using a chronometer (reported

in minutes). A control radiograph was also obtained from

the mesiodistal direction to ensure complete obturation.

The teeth were incubated at 37C and 100% mois-

ture for 14 days for completion of setting of sealer.

Using an endodontic motor, root surface was marked

at 3, 6 and 9 mm from the apex and the teeth were

 xed to IsoMet cutting machine (Buehler IsoMet Low

Speed Saw 11-1180) from the coronal part using glue.

The roots were sectioned horizontally under copious

water. The slices were immersed in sodium hypochlo-

rite solution for one minute to eliminate dentin chips

and were then rinsed with 17% EDTA (Calasept Nord-

iska Dental) for one minute followed by a rinse with

water. The slices were photographed at 40 magni ca-

tion under a stereomicroscope (SZX9; Olympus, Japan).

574 AREA-METRIC ANALYSIS OF THE QUALITY OF OBTURATION OF FOUR DIFFERENT TECHNIQUES BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Yazdan Shantiaee etal.

Photographs were saved in TIF format and assessed in

Adobe Photoshop CS6 1301.2 software. In this software,

the total surface area of the canal in each section and

the percentage of gutta-percha  lled area (PGFA) and

percentage of sealer- lled area (PSFA) were separately

calculated on each image in pixels. The percentage of

void areas [total area of section-(PSFA+PGFA)] was also

calculated. These values were reported for each section.

All measurements were made by an examiner blinded to

the group allocation of teeth (Figure 1). The values were

recorded in Microsoft Excel 2013.

The PGFA and PSFA data in different sections were

analyzed using repeated measures ANOVA. Obturation

time data were analyzed using ANOVA and data of per-

centage of voids were analyzed using the Kruskal Wallis

test. The mean and standard deviation of PGFA, PSFA

and void area were reported. For the comparison of the

mean PGFA and PSFA, repeated measures ANOVA was

used (since data were normally distributed). The Kruskal

Wallis test was used to compare the mean area of voids

in different sections. Data were analyzed using SPSS

version 21 (SPSS Inc., IL, USA).

RESULTS AND DISCUSSION

Table 1 shows the mean PSFA, PGFA and void area val-

ues in apical, middle and coronal sections. Table 2 shows

the mean time of obturation in the groups. Table 3 shows

the P values for the comparisons. As seen in Table 3,

in the apical section, CLNS group showed signi cantly

lower PGFA than other groups (P<0.05). PGFA of WLS

group was signi cantly higher than that of other groups

followed by CLS, control and CLNS groups, respec-

tively. The difference of WLS with CLNS was signi -

cant (P<0.05) but its difference with other groups was

not signi cant (P>0.05) in this respect. The CLS group

showed higher PGFA than the control group but this dif-

ference was not signi cant (P>0.05).

In the middle section, WLS showed higher PGFA than

other groups followed by CLS, control and CLNS groups,

respectively but only the difference between WLS and

CLNS was signi cant (P<0.05). The CLNS group showed

lower PGFA than other groups but this difference only

for WLS was signi cant (P<0.05). The CLS showed

higher PGFA than the control group but this difference

was not signi cant (P>0.05).In the coronal section, the

CLNS group showed signi cantly lower PGFA than other

groups (P<0.0001). The PGFA in WLS group was higher

than that in other groups followed by CLS, control and

CLNS groups. The difference between CLNS and WLS

was signi cant (P<0.0001) but other differences were

not signi cant (P>0.05). The CLS group showed higher

PGFA than the control group but this difference was not

signi cant (P>0.05).

As seen in Table 4, in the apical section, the CLNS

group showed signi cantly higher PSFA than other

groups (P<0.05). The PSFA in WLS group was lower than

that in other groups followed by CLS, control and CLNS

groups, respectively. The difference between WLS and

CLNS was signi cant (P<0.0001) but other differences

were not statistically signi cant (P>0.05). The CLS group

showed lower PSFA than the control group but this dif-

ference was not signi cant (P>0.05). In the middle sec-

tion, WLS group showed lower PSFA than other groups

followed by CLS, control and CLNS groups, respectively.

Only the difference between the WLS and CLNS groups

was signi cant (P<0.05). The CLNS group showed higher

PSFA than other groups but this difference only with

WLS was signi cant (P<0.05). The CLS group showed

lower PSFA than the control group but this difference

was not signi cant (P>0.05).

In the coronal section, the CLNS group showed sig-

ni cantly higher PSFA than other groups (P<0.0001).

PSFA of WLS group was lower than that of other groups

followed by CLS, control and CLNS groups, respec-

tively. The difference of WLS and CLNS was signi cant

(P<0.0001) but the difference with other groups was not

statistically signi cant (P>0.05). In general, in all sec-

tions, the WLS group showed higher PGFA and lower

PSFA than other groups followed by CLS, control and

CLNS groups, respectively. The difference between WLS

and CLNS in terms of PGFA and PSFA only in the mid-

dle third was statistically signi cant (P<0.05). The CLNS

group in all sections showed lower PGFA and higher

PSFA than other groups and this difference in the api-

cal and coronal section was statistically signi cant. The

CLS group compared to the control group showed higher

PGFA and lower PSFA in all sections but these differ-

ences were not statistically signi cant (P>0.05).

No signi cant difference was noted in apical, middle

and coronal sections of the four groups in terms of voids

(P>0.05).

As seen in Table 5, the mean time required for root

canal obturation in WLS group was signi cantly longer

than that in other groups (P<0.0001) followed by the con-

trol, CLS and CLNS groups, respectively. The mean time

required for root canal obturation in CLNS group was sig-

ni cantly shorter than that in the control group (P<0.05).

Three-dimensional obturation of root canal system is

necessary to prevent bacterial reentry and ensure long-

term success of endodontic treatment (Raina etal. 2007;

Michaud etal. 2008). Finding an ef cient technique with

the greatest ability to provide a hermetic seal is impor-

tant to guarantee the success of endodontic treatment

(Haikei etal. 2006). This study compared the quality of

obturation of straight root canals prepared with Mtwo

rotary  les and  lled with four obturation techniques by

measuring the surface area  lled with gutta-percha and

Yazdan Shantiaee etal.

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS AREA-METRIC ANALYSIS OF THE QUALITY OF OBTURATION OF FOUR DIFFERENT TECHNIQUES 575

Table 1. Mean PSFA, PGFA and void area in the apical, middle and coronal sections of the four groups

Mean

(%)

Standard

deviation

Maximum Minimum

Mean

(%)

Standard

deviation

Maximum Minimum

Mean

(%)

Standard

deviation

Maximum Minimum

Apical

control 6.08 2.37 9.67 2.61 92.85 2.18 96.36 89.33 0.06 0.18 0.6 0

CLS 6.09 2.25 9.62 2.56 93.90 2.25 97.42 90.39 0 0 0 0

CLNS 16.79 9.92 20.31 13.26 83.20 9.92 79.69 86.72 0 0 0 0

WLS 5.03 3.44 8.55 1.50 94.96 3.44 98.48 91.45 0 0 0 0

Middle

control 4.43 2.33 7.07 2.73 95.09 2.33 97.27 92.91 0.47 0.84 2.20 0

CLS 3.96 3.17 6.36 2.02 95.80 3.17 97.98 93.62 0.50 1.59 5.05 0

CLNS 7.78 4.98 10.42 6.07 91.75 5.01 93.92 89.57 0.46 1.45 4.60 0

WLS 3.95 2.33 6.12 1.77 96.04 2.33 98.22 93.86 0 0 0 0

Coronal

control 5.29 4.69 9.20 2.23 94.28 4.69 97.75 90.81 0.42 0.90 2.50 0

CLS 5.23 3.59 9.11 2.15 94.46 3.48 97.93 90.99 0.40 0.81 2.50 0

CLNS 19.2 8.54 24.13 17.16 79.35 8.54 82.82 75.88 1.44 1.84 4.56 0

WLS 4.39 3.14 8.21 1.24 95.26 3.14 98.73 91.79 0.34 0.83 2.68 0

Yazdan Shantiaee etal.

576 AREA-METRIC ANALYSIS OF THE QUALITY OF OBTURATION OF FOUR DIFFERENT TECHNIQUES BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS

Table 2. Obturation time in the four groups

MinimumMaximumStandard

deviation

Mean

(minutes)

Group

5.207.600.606.41Control

4.506.900.825.66CLS

3.906.200.825.03CLNS

6.5010.301.188.43WLS

Table 3. P values for the comparison of PGFA in the apical, middle and coronal sections of the four groups

WLS CLNS CLS Control

Coronal Middle apical coronal Middle apical coronal middle apical Coronal Middle Apical

Control 1 1 1 <0.0001* 0.203 0.001* 1 1 1

CLS 1 1 1 <0.0001* 0.067 0.001* 1 1 1

CLNS <0.0001* 0.045* <0.0001* <0.0001* 0.067 0.001* <0.0001* 0.203 0.001*

WLS <0.0001* 0.045* <0.0001* 1 1 1 1 1 1

*Signi cant.

Table 4. P values for the comparison of PSFA in the apical, middle and coronal sections of the four groups

WLS CLNS CLS Control

Coronal middle apical coronal Middle apical coronal middle apical Coronal Middle Apical

control 1 1 1 <0.0001* 0.206 0.002* 1 1 1

CLS 1 1 1 <0.0001* 0.068 0.001* 1 1 1

CLNS <0.0001* 0.046* <0.0001* <0.0001* 0.068 0.001* <0.0001* 0.206 0.002*

WLS <0.0001* 0.046* <0.0001* 1 1 1 1 1 1

*Signi cant.

Table 5. P values for the comparison of obturation

time in the four groups

ControlCLSCLNSWLSGroup

-0.280.01<0.0001Control

0.28-0.43<0.0001CLS

0.010.43-<0.0001CLNS

<0.0001<0.0001<0.0001-WLS

sealer using area-metric analysis. The results showed

that root canal obturation with non-standard accessory

cones and a master cone with 4% taper decreased the

gutta-percha mass and increased the sealer area. Use

of a master cone with 4% taper had no positive effect

on quality of obturation or working time. Warm lateral

compaction in straight canals had no superiority over

cold lateral compaction and took longer to accomplish.

In our study, root canals were prepared using Mtwo

rotary system since Schafer etal. (2016) in 2016 showed

that root canals  lled with gutta-percha of Mtwo rotary

system had higher quality of obturation compared to

those  lled with gutta-percha of Reciproc and WaveOne

systems. Also, we wanted to compare the percentage

of area  lled with gutta-percha in case of using gutta-

percha with 4% taper. Thus, Mtwo was a suitable choice

for this purpose since #35 gutta-percha in Mtwo system

has 4% taper. Although master cone in our study was

#35 with 4% taper (matched single cone of Mtwo sys-

tem), not all the prepared canals follow the shape and

taper of  nal  le after preparation with the  nal rotary

 le, so we designed a group in which we placed acces-

sory gutta-percha cones between single cone and canal

walls to assess the possibility of improving the qual-

ity of obturation. Apical seal is an important param-

eter in success of endodontic treatment and improper

apical seal results in development of periapical lesions.

The results of our study showed that in the apical third,

use of non-standard gutta-percha alongside the master

cone with 4% taper signi cantly decreased the apical

seal and quality of obturation and decreased PGFA and

increased PSFA. Also, our results showed that use of

standard gutta-percha with 2% and 4% taper along with

2% accessory cones did not cause a signi cant change

in quality of obturation in the apical third. Although

PGFA in 4% gutta-percha group was higher and PSFA

was lower than that in other groups, these differences

were not signi cant and no difference in voids was

noted either. Based on our results, warm lateral com-

Yazdan Shantiaee etal.

BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS AREA-METRIC ANALYSIS OF THE QUALITY OF OBTURATION OF FOUR DIFFERENT TECHNIQUES 577

paction had no superiority over cold lateral compaction

since no difference was noted between the two groups in

any of the assessed parameters.

Comparison of the mean time of obturation among the

groups showed that the mean time of obturation was sig-

ni cantly longer in WLS group compared to other groups.

This time in CLNS group was signi cantly shorter than

that in the control group. The CLS and control groups

were not signi cantly different in this regard. Schafer

etal. in 2012 compared the quality of root canal obtura-

tion with 2% and 4% taper gutta-percha cones by micro-

scopic area-metric analysis and found no signi cant dif-

ference between the two types in the apical region. None

of them provided a better apical seal. Romina etal.(2009)

performed area-metric analysis of root  lling and showed

equal apical seal in use of gutta-percha cones with 2%

and 4% taper. Our results were in agreement with those of

the afore-mentioned studies.

We found no signi cant difference in time of obtu-

ration between the use of gutta-percha cones with 2%

and 4% taper, which was in agreement with the results

of Schafer etal.(2012). Our results regarding the use of

non-standard MF gutta-percha cones in comparison

with the use of standard gutta-percha showed that use

of non-standard cones along with a master cone with

4% taper decreased PGFA and increased PSFA in all sec-

tions and this difference in the apical and coronal thirds

was signi cant. Thus, use of MF accessory cones along

with 4% gutta-percha does not provide suitable apical

seal. In contrast to our results, VanGheluwe and Wilcox

in 1996 found no signi cant difference in apical seal of

standard and non-standard gutta-percha cones. Differ-

ence in the results of the two studies may be due to the

use of curved roots in their study. Use of warm lateral

compaction method in our study increased PGFA and

decreased PSFA in all sections, although insigni cantly.

No difference was noted in terms of voids. No signi cant

difference between warm and cold lateral compaction

techniques in our study may be due to our small sam-

ple size and use of straight canals because cold lateral

compaction in straight canals is much easier and yields

better results than in curved canals.

Thus, future studies with larger sample sizes are required

to compare these two methods in curved canals. Collins

etal. (2006) compared warm and cold lateral compaction

and warm vertical condensation and concluded that warm

lateral compaction signi cantly increases the volume of

gutta-percha mass in the canal compared to cold lateral

compaction. Difference between our results and theirs

may be due to different methodology since we performed

area-metric analysis while they used replication of canal

irregularity. Moreover, they used D11T spreader in their

study, which is very  ne and made of stainless steel, and

can penetrate to 1mm of the working length while we used

 nger spreader penetrated to 2mm of the working length.

Moreover, they used non-standard MF gutta-percha while

we used standard cones with 2% taper.

Several methods are available for assessment of the

quality of root canal  lling such as dye penetration

(McRobert etal. 997), microbial leakage models, repli-

cation of canal irregularity (Jacobson etal. 2008) and

three-dimensional analysis by micro-computed tomog-

raphy (CT) (Hammad etal. 2009). These methods have

advantages and limitations. Dye penetration and micro-

bial leakage are more commonly used due to simplic-

ity and acceptable accuracy; however, smaller size of

dye particles than some bacteria (Nielsen et al. 1995)

and complexity and time consuming nature of microbial

leakage (Sequeira etal. 2000) are among the drawbacks

of these techniques.

Area-metric analysis has been used by many research-

ers for assessment of the success of endodontic treat-

ment in vitro. Thus, this method was used in our study.

The limitations of this method include two-dimensional

analysis of the root canal  lling and lower accuracy

than micro-CT. Moreover, dentin chips and smear layer

created during sectioning in this method may decrease

the quality of images and cause erroneous determina-

tion of borders between gutta-percha, sealer and voids.

To overcome this limitation, we immersed the slices in

sodium hypochlorite solution for one minute after sec-

tioning followed by one minute in 17% EDTA and then

rinsed them to eliminate the smear layer and dentin

chips. Considering the higher accuracy of micro-CT for

three-dimensional assessment of quality of obturation,

further studies with the use of micro-CT on both straight

and curved canals are required to obtain more accurate

information on this topic.

CONCLUSION

Root canal obturation with non-standard accessory

cones and a master cone with 4% taper decreases the

gutta-percha mass and increases the sealer area and

therefore, compromises the quality of root canal  lling.

Use of a master cone with 4% taper has no positive effect

on quality of obturation or working time. Warm lateral

compaction in straight canals has no superiority over

cold lateral compaction and takes longer to accomplish.

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