Braz J Oral Sci. 15(1):45-50

Original Article Braz J Oral Sci.
January | March 2016 - Volume 15, Number 1  

Factors associated with the technical 
quality of root canal fillings performed by 

undergraduate dental students in a Malaysian 
Dental School

Choon Yoong Wong1, Yan Xia Liaw1, Jhiew Zhan Wong1, Lee Chian Chen1, Abhishek Parolia1, Allan Pau1

1International Medical University, School of Dentistry, Division of Clinical Dentistry, Kuala Lumpur, Malaysia

Correspondence to:
Abhishek Parolia

Division of Clinical Dentistry, School of Dentistry,
International Medical University, 126, Jalan Jalil

Perkasa 19, Bukit Jalil
57000 Kuala Lumpur, Malaysia

E-mail: abhishek_parolia@imu.edu.my

Abstract

Aim: A retrospective clinical audit was carried out on records of endodontic treatment performed by 
dental undergraduates. The audit was performed to evaluate the technical quality of root canal fillings 
performed by dental undergraduates and determine the associated factors. Methods: 140 records of 
patients who had received root canal treatment by dental undergraduates were evaluated through 
periapical radiographs by two examiners (κ =0.74). The root canal fillings had their quality evaluated 
according to extent, condensation and presence of procedural mishap. Possible factors associated 
with technical quality such as tooth type, canal curvature, student level and quality of record keeping 
were evaluated. Data were statistically analyzed using chi-square test (p<0.05). Results: Among 
the 140 root-filled teeth, acceptable extent, condensation and no-mishap were observed in 72.1%, 
66.4% and 77.9% cases respectively. Overall, the technical quality of 68 (48.6%) root-filled teeth 
was considered acceptable. Overall, non-acceptable root canal fillings were significantly more 
likely to be observed in molars (69.2%), moderately and severely curved canals (71.4%) and junior 
students (61.5%). There was no association between acceptable root canal fillings and quality of 
record keeping. Conclusions: The technical quality of root canal fillings was acceptable in 48.6% 
cases and it was associated with tooth type, degree of canal curvature and student seniority.

Keywords: Endodontics. Root Canal Therapy. Education.

Introduction
 
Endodontic treatment encompasses procedures designed to maintain the health of 

all or part of the dental pulp. When the dental pulp is diseased, endodontic treatment 
aims at preserving healthy periradicular tissues. However, if apical periodontitis occurs, 
the treatment aims restoring the periradicular tissue health.

The purpose of endodontic treatment is to disinfect the entire root canal system and 
maintain asepsis1. The European Society of Endodontology stated that an appropriate 
endodontic treatment involves the following parameters: exposure of a good quality pre-
operative radiograph, administration of local anesthesia, isolation of tooth, preparation of 
access cavity, determination of working length, shaping, cleaning and obturation of the 
root canal system1. There is substantial evidence that the technical quality of root canal 
fillings has a significant impact on the outcome of the treatment and long-term retention 

http://dx.doi.org/10.20396/bjos.v15i1.8647122

Received for publication: April 06, 2016
Accepted: June 27, 2016



46

of endodontically treated teeth1. Many studies reported that root 
canal fillings placed within 0-2 mm of the radiographic apex are 
associated with lesser chances of radiographic and clinical failures 
than those that are under-filled or over-filled2-6. 

Clinical audit is defined as a quality improvement process that 
seeks to improve patient care and outcomes by systematic review 
of care against explicit criteria and the implementation of change. 
The use of clinical audit in endodontic treatment has been widely 
reported5,7-14. 

This study was a clinical audit on technical quality of root canal 
fillings performed by undergraduates. The aims of this study were 
to evaluate the quality of root canal fillings performed by dental 
undergraduates in a Malaysian Dental School and to determine 
factors associated with the technical quality of root canal fillings.

Material and methods

The present study was restricted to patients who attended 
the School of Dentistry, International Medical University, Kuala 
Lumpur, Malaysia, for root canal treatment. A retrospective clinical 
audit was carried out on the records of endodontic treatment 
performed only by undergraduate students. All 142 electronic 
records of endodontic treatment performed by dental undergraduates 
from January 2011 to April 2013 were retrieved and printed. 
Inclusion criterion of this study was endodontic treatment completed 
by dental undergraduates. Incomplete endodontic treatment and 
records without post-operative radiographs were excluded. Two 
records were excluded due to incomplete treatment and missing 
postoperative radiograph respectively. The remaining 140 records 
fulfilled the inclusion criteria. Two fourth year dental undergraduates 
carried out the audit after undergoing training in clinical audit, 
which consisted of: 

• A 2-h seminar on the principles and practice of clinical audit.
• Desktop research on criteria for assessing the technical quality 

of root canal fillings and quality of record keeping. 
• Development of audit checklist form and protocol for auditing 

the records.
• Training on radiographic evaluation of root canal fillings by 

an endodontist.

Root Canal Treatment Procedure 
The dentist first examined patients who attended IMU Oral 

Health Centre seeking for treatment and then referred these cases 
to undergraduate students or endodontic specialists based on the 
complexity of the tooth/root canal and economic concern of the 
patients. The subjects were patients who had a specific endodontic 
disease needing emergency treatment. After thorough clinical 
examination and considering the technical difficulties related to 
root canal therapy, the endodontic staff allotted these patients to 
different cohorts of undergraduates based on their seniority and 
competency level.

The chief concern of the patient was obtained together with 
patient’s medical, dental, pain history. Appropriate investigations 
were carried out to come to a diagnosis. All root canal procedures 
were performed using a rubber dam and aseptic technique. Access 
cavities were prepared using endodontic access burs (Dentsply 

Factors associated with the technical quality of root canal fillings performed by undergraduate dental students in a Malaysian Dental School

Braz J Oral Sci. 15(1):45-50

Maillefer, Ballaigues, Switzerland). The working lengths (1 mm 
short of the radiographic apex) were established using electronic 
apex locators and reconfirmed radiographically.

The hybrid technique was used for shaping and cleaning 
procedures. The coronal two-thirds of the canals were prepared 
sequentially using Gates Gliden burs, (Dentsply Maillefer) and 
K-Flex file (Dentsply Maillefer). The apical third was instrumented 
to the master apical file 1 mm short from the radiographic apex. 
Root canals were further instrumented with step-back enlargement to 
three sizes larger than the master apical file. Finally, circumferential 
filing was done to complete the shaping of the root canal. 2% 
sodium hypochlorite (Clorox Company, Broadway, Oakland, 
CA, USA), saline (to flush sodium hypochlorite and prevent any 
interaction in between sodium hypochlorite and EDTA) and 18% 
ethylenediaminetetraacetic acid (EDTA, Ultradent Products Inc., 
South Jordan, UT, USA) were used as irrigants. 

All patients were treated in multiple visits and non-setting 
calcium hydroxide (Calcicur, Voco Gmbh, Cuxhaven, Germany) as 
an intracanal dressing and reinforced zinc oxide temporary cement 
(IRM, Dentsply Caulk, Milford, DE, USA) or Cavit (3M ESPE, 
St. Paul, MN, USA) as a temporary restorative materials were used 
between appointments.  

In the subsequent visits all root canals were filled using gutta-
percha points with AH plus (Dentsply Maillefer) root canal sealer 
using lateral compaction technique. Following, all root canals were 
sealed with glass ionomer cement (GC Corporation, Tokyo, Japan) 
and thereafter the most suitable post- endodontic coronal restorations 
(amalgam/composite/post and core) were placed after assessing the 
amount of remaining tooth structure.

 
Evaluation of the technical quality of root canal fillings

Three periapical radiographs were examined for each root 
canal filling: pre-operative, working length determination and 
post-operative. Two examiners evaluated independently all the 
radiographs. Radiographs were examined in the form of full 
screen images that could be enhanced and zoomed in on the 
computers. If disagreement in interpretation occurred between the 
examiners, the radiographs were re-evaluated until an agreement 
was reached. Kappa value for inter-examiner agreement was 0.74. 
The technical quality of root canal fillings was evaluated according 
to condensation of root canal fillings, extent of root canal fillings 
and presence of procedural mishaps (Table 1)8. For a multi-rooted 
tooth, all canals were evaluated simultaneously and an overall score 
was given to the tooth (e.g. technical quality of a multi-rooted 
tooth was considered acceptable only when the technical quality 
of all the root canals was acceptable).

Possible factors associated with the technical quality 
of root canal fillings
Anatomical characteristics of tooth: For each root-treated tooth, the 
tooth type and complexity (root canal curvature) were assessed. 
The complexity (root canal curvature) was determined based 
on the pre-operative radiographs according to the Schneider’s 
classification of curvature15. Tooth with moderate (10-20°) and 
severe curvature (25-70°) canals were combined and compared 
against tooth with straight canal (5° or less).



47Factors associated with the technical quality of root canal fillings performed by undergraduate dental students in a Malaysian Dental School

Braz J Oral Sci. 15(1):45-50

Variables Criteria Definition
Condensation Acceptable No void identified in root canal filling or between 

root canal filling and root canal walls
Non-acceptable Presence of void in root canal filling or between root 

canal filling and root canal walls
Extent Acceptable Root canal filling material is within the root canal 

system and within 2 mm of the radiographic apex
Under-filled Root canal filling material is >2 mm short of the 

radiographic apex
Over-filled Root canal filling material is extruded beyond the 

radiographic apex
Mishap No mishap No mishap identified 

Ledge Root canal filling is at least 1 mm shorter than
the working length and is deviated from the
original canal curvature

Perforation Apical termination of filled canal is different
from the original canal terminus or root canal
filling material is extruded through the apical 
foramen

Separation of
instruments

Separated instrument identified 

Others Other mishaps identified
Overall Acceptable Acceptable condensation and extent of root canal 

filling with no mishap
Non-acceptable Non-acceptable condensation and/or non- accept-

able extent of root canal filling with/without mishap

Table 1 - Criteria used to assess technical quality of root canal fillings.

Student seniority: Third and fourth year undergraduates were 
combined and compared to fifth year undergraduates.
Quality of the record keeping of endodontic treatment: Evaluation 
of quality of record keeping was based on the records of each 
endodontic treatment performed by undergraduate students. All the 
records were audited independently by two examiners against the 
set of criteria that had been previously developed accordingly to 
the European Society of Endodontology guideline1. The presence 
or absence of recording of each criterion (total=17) was observed: 
use of an electric pulp test, use of local anesthesia, name of local 
anesthesia, dosage of local anesthesia, use of rubber dam isolation, 
working length, reference point of working length, size of initial 
apical file, size of master apical file, applied intracanal dressing, 
medication prescribed including analgesics and antibiotics, size of 
master cone, pre-operative radiograph, working length radiograph, 
master cone radiograph, post-operative radiograph and advice on 
final restoration in the follow-up visit.

Statistical analysis
Data were entered into SPSS 18.0 (SPSS, Inc., Chicago, IL, 

USA) for analysis. The frequency distributions of the technical 
quality of root canal fillings were calculated. Chi-square tests were 
performed to determine associations between the technical quality 
of root canal fillings and possible associated factors (e.g. tooth 
type, root canal curvature, student seniority and quality of record 
keeping). The significance level was set at p<0.05. 

Results

Technical quality of root canal fillings
The present study reviewed the records 140 root-filled teeth. 

The distribution of this sample according to the tooth type and 
student seniority is in Table 2. Sixty-five (46.4%) teeth were treated 
by third and fourth year undergraduates and the remaining by the 
fifth year undergraduates. The most commonly treated tooth types 
were molars (37.1%), followed by premolars (32.9%), incisors 
(23.6%) and canines (6.4%). The condensation of root filling 
was acceptable in 93 (66.4%) cases, extent was acceptable in 101 
(72.1%) cases and no mishaps were observed in 109 (77.9%) cases 
(Table 3). Overall, the technical quality of 68 (48.6%) of all 140 
root-filled teeth was considered acceptable (Table 3).

Possible factors associated with the technical quality 
of root canal fillings

Among the different tooth types, mishaps were significantly 
more likely to be observed in molars (32.7%, Table 4) compared 
to premolars (8.7%, p<0.05). Overall non-acceptable root canal 
fillings were significantly more likely to be noted in molars (69.2%) 
compared to other tooth types (p<0.01). Under- and over-extended 
of root canal fillings were significantly more likely to be observed 
in moderately and severely curved canals (47.6%) compared to 
straight canals (24.4%, p<0.05). Overall non-acceptable root canal 
fillings were significantly more likely to be observed in moderately 
and severely curved canals (71.4%) compared to straight canals 
(47.9%, p<0.05). According to student seniority, non-acceptable 
condensation was more common among third and fourth year 
students (49.2%) compared to fifth year students (20.0%, p<0.01). 
Similarly, non-acceptable extent was more common among junior 
students (36.9%) compared to senior students (20.0%, p<0.05). 
Overall non-acceptable root canal fillings were significantly 
associated with junior students (61.5%) compared to senior students 
(42.7%, p<0.05).



curved canals18. Under-filled and over-filled root canal fillings 
occurred more frequently in teeth with curved canals and this 
may be attributed to the failure to realize canal curvature before 
preparation of the root canal system, leading to internal and 
external transportation, over-preparation, and straightening of the 
curved canals. In consequence, the loss of apical stop may result 
in over-filling of root canals. To improve the technical quality 
of root canal fillings in the molars and teeth with curved canals, 
endodontic training must emphasize the difficulties of treating 
molars and teeth with curved canals. Increase in pre-clinical 
laboratory training and addition of seminars would be beneficial for 
students to familiarize with necessary procedures and precautions 
required for managing molars and teeth with curved canals. The use 
of dental magnification such as magnifying loupes and operating 
microscopes while performing molar endodontics would enhance 
visualization of the treatment field and increase accuracy of the 
endodontic procedures22. In addition; the use of rotary instruments 
may be considered, especially for molar endodontics20,23. However, 
it is not used by our undergraduate students. 

48

Student seniority Incisors Canines Premolars Molars Total (%)
3rd and 4th 19 3 24 19 65 (46.4%)
5th 14 6 22 33 75 (53.6%)
Total (%) 33 (23.6%) 9 (6.4%) 46 (32.9%) 52 (37.1%) 140 (100.0%)

Table 2 - Distribution of teeth in the sample.

Discussion

The key findings of this retrospective study were that the 
technical quality of root canal fillings performed by the fifth year 
dental undergraduates were superior to the third and fourth year 
undergraduates, and the overall technical quality was better in 
anterior teeth and teeth with straight canals irrespective of student 
seniority. Overall, the technical quality of root canal fillings 
performed by dental undergraduates in this study was considered 
acceptable in nearly half the sample. This result is lower than 
those reported for Scottish13, Lithuanian9, Irish11, Greek10, Iranian16, 
Turkish17 and Serbian students18, but better when compared to 
Turkish8, French12, Jordanian19, Saudi Arabian7 and Spanish 
students20. Wide variations in proportions of acceptable root canal 
fillings have been reported in the literature. They may be related to 
the different criteria used in evaluation, size and types of selected 
sample and the training the students received. For example, the 
Lithuanian study9 did not take procedural mishap into account 
for evaluation of the technical quality and the findings were only 
based on condensation and extent of root canal fillings. Lynch 
& Burke (2006) reported that 63.0% of root canal llings were 
technically acceptable11. However, only single-rooted teeth were 
included in their study as compared to the present study, which 
evaluated the technical quality performed on both single-rooted 
and multi-rooted teeth. 

In the present study, non-acceptable root canal fillings were 
more common in the molars compared to the incisors, canines 
and premolars. The reason for this was the high incidence of 
procedural mishaps in the molars. This is consistent with results 
reported by Balto et al.7, Moussa-Badran et al.12, and Moradi et 
al.21. The high incidence of procedural mishaps may be attributed 
to the anatomy of molars (e.g. multiple root canals and greater 
canal curvatures) and difficulty to have adequate coronal access 
during the procedure21. The results also highlighted that non-
acceptable root canal fillings were more common in teeth with 

Variables Criteria Definition
Condensation Acceptable 93 (66.4%)

Non-acceptable 47 (33.6%)
Extent Acceptable 101 (72.1%)

Under-filled 19 (13.6%)
Over-filled 20 (14.3%)

Mishap No mishap 109 (77.9%)
Ledge 12 (9.3%)
Perforation 16 (11.4%)
Separation of instruments 1 (0.7%)
Others 1 (0.7%)

Overall Acceptable 68 (48.6%)
Non-acceptable 72 (51.4%)

Table 3 - Acceptable and non-acceptable root canal fillings 
performed by undergraduate students.

Total Total of overall non-acceptable
Non-acceptable 
condensation

Under-filled and 
over-filled Mishap

Tooth type Incisors 33 16 (48.5%) * 9 (27.3%) 8 (24.2%) 8 (24.2%) **
Canines 9 2 (22.2%) 0 (0.0%) 1 (11.1%) 2 (22.2%)
Premolars 46 18 (39.1%) 16 (34.8%) 10 (21.7%) 4 (8.7%)
Molars 52 36 (69.2%) 22 (42.3%) 20 (38.5%) 17 (32.7%)

Complexity Straight 119 57 (47.9%)** 39 (32.8%)   29(24.4%)** 25 (21.0%)
Moderate and severe 21 15 (71.4%) 8 (38.1%) 10 (47.6%) 6 (28.6%)

Student seniority 3rd and 4th 65 40 (61.5%)** 32 (49.2%)* 24 (36.9%) ** 14 (21.5%)
5th 75 32 (42.7%) 15 (20.0%) 15 (20.0%) 17 (22.7%)

Quality of record keeping Good  † 69 33 (47.8%) 20 (29.0%) 19 (27.5%) 14 (20.3%)
Poor  † 71 39(54.9%) 27 (38.0%) 20(28.2  %) 17 (23.9%)

Table 4 - Non-acceptable root canal fillings according to tooth type, complexity, student seniority, and quality of record keeping.

*p <0.01. ** p <0.05. † good quality of record keeping (11-17 criteria recorded in record); poor quality of record keeping (<11 criteria recorded in record).

Factors associated with the technical quality of root canal fillings performed by undergraduate dental students in a Malaysian Dental School

Braz J Oral Sci. 15(1):45-50



49Factors associated with the technical quality of root canal fillings performed by undergraduate dental students in a Malaysian Dental School

The technical quality of root canal fillings performed by 
fifth year dental undergraduates was significantly better than by 
the third and fourth year undergraduates. On one hand, this is 
to be expected as the fifth year dental undergraduates are more 
experienced; however, all patients treated by undergraduates 
should expect the same high quality endodontic treatment 
regardless the student’s seniority. To minimize the percentage of 
non-acceptable root canal fillings performed by third and fourth 
year dental undergraduates, closer supervision is recommended as 
well as case selection according to the degree of difficulty24. Simple 
cases of endodontic treatment (e.g. anterior teeth and teeth with 
straight canals) should be treated by third and fourth year dental 
undergraduates whilst a little bit more complex cases (including 
molar teeth with a slight root curvature) should be treated by the 
fifth year dental undergraduates. Moreover, teeth with moderate 
or high level of difficulty should be referred to specialists. This 
will allow the third and fourth year dental undergraduates to gain 
adequate competency in managing simple cases prior to performing 
more complex cases of endodontic treatment. 

In this retrospective study, only half of the clinical records 
kept by dental undergraduates met the criteria of good record 
keeping, despite implementation of general guidelines on record 
keeping for endodontic treatment in the dental clinic. This finding 
emphasizes the need to reinforce the guidelines on record keeping. 
Although the present results showed that the quality of record 
keeping had no significant association with the technical quality 
of root canal fillings, inadequate record keeping may increase the 
opportunities for potential litigation by the patients25. Therefore 
it is mandatory for the dental undergraduates to record details of 
the procedure performed to avoid medicolegal issues. 

In all cases performed by dental undergraduates, the working 
length measurement (i.e 1 mm before the apex) was established 
using electronic apex locators and reconfirmed radiographically, 
which is routinely used in most of the dental schools26. The 
instruments used for canal preparation were stainless steel hand 
K Flex files and Gates Glidden burs (Dentsply Maillefer). Canal 
preparation was carried out using a combination of crown down and 
step back technique. This technique has been shown to be useful 
for teaching dental undergraduates11. 2% sodium hypochlorite 
(Clorox) and 18% EDTA (Ultradent Products Inc.) were used as 
irrigants. Alternate use of sodium hypochlorite and EDTA hwas 
found to be very effective in removing the smear layer from the 
root canals27,28. Calcium hydroxide (Calcicur, Nordiska Dental 
AB, Angelholm, Sweden) was used as an intra-canal medicament 
that provides antimicrobial activity and prevents recontamination 
of the root canal system29,30. Lateral compaction technique with 
gutta-percha points and AH plus (Dentsply Maillefer, USA) root 
canal sealer was used to obturate all the canals, a technique used 
in other countries2,8,31.

There are a few limitations in this retrospective study. The 
sample size is relatively small and the radiographical analysis 
does not entirely reflect the technical quality of root canal fillings 
because it is not a direct indication of the disinfection quality. 
Besides that, a single periapical radiograph only provides a two-
dimensional image. Therefore it is sometimes difficult to separate 
superimposed anatomical structures (e.g. multiple root canals) 
while evaluating the radiographs16.

In conclusion, the technical quality of root canal fillings 
performed by dental undergraduates was acceptable in nearly 
half the cases. The results have highlighted points that should be 
considered during the case selection for undergraduate students and 
also in the teaching of endodontics. Factors found to be associated 
with the technical quality of root canal fillings were tooth type, 
root canal curvature and student seniority.

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Factors associated with the technical quality of root canal fillings performed by undergraduate dental students in a Malaysian Dental School

Braz J Oral Sci. 15(1):45-50