RESEARCH
http://dx.doi.org/10.17159/2519-0105/2021/v76no5a5

 

Quality of root canal treatment performed by undergraduate students at the Wits Oral Health Centre

 

 

E Patel^I; AAM Ehbesh^II; IE Munshi^III; S Tootla^IV

^IBDS, MSc (Dent), Department of Paediatric and Restorative Dentistry, School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. ORCID Number: 0000-0002-7683-4867
^IIBDS, MSc (Dent), Department of Conservative Dentistry and Endodontics, Faculty of Dentistry and Oral Surgery, Alasmarya University, Zliten, Libya
^IIIBSc, BCHD, MDent, Department of Oral Rehabilitation, School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
^IVBCHD, MScDent, Department of Paediatric & Restorative Dentistry, School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa

Correspondence

 

 

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ABSTRACT

PURPOSE: In 2012, the School of Oral Health Sciences at the University of the Witwatersrand modified its undergraduate endodontic curriculum which led to a need to assess the impact of curriculum changes on root canal treatment outcomes. This study was an audit of root canal treatment performed by undergraduate BDS students using postoperative radiographs, and compared the results between different undergraduate clinical years of study.
METHODOLOGY: Postoperative periapical radiographs of patients treated by undergraduate students were examined to assess length, density and taper. Two independent investigators were first calibrated, and thereafter assessed 299 endodontic cases that were performed by third, fourth and fifth year students during the 2013-2015 period at the Wits Oral Health Centre.
RESULTS: 68.9%, 73.6% and 70.9% were found for adequate length, acceptable density and acceptable taper of root Alling respectively. The most acceptable length, density and taper results were seen in patients treated by final year students, while the lowest results were observed in the fourth year student cohort. There was a tendency for third year students to overfill due to over-instrumentation of anterior teeth.
CONCLUSION: The change in the curriculum has been justified, though room for improvement exists. The superior result found in the 5th year student cohort was most likely due to their relative experience, and the use of rotary instrumentation and dental operating microscopes. Endodontic teaching should further emphasize the importance of length control during endodontic treatment and more stringent steps may be necessary during patient allocation and clinical supervision of fourth year dental students.

Keywords: Quality, root canal treatment, undergraduate student.

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ACRONYMS

AC: Apical Constriction

CDJ: CementoDentinal Junction

AF: Apical Foramen

AP: Apical Periodontitis

AAE: American Association of Endodontists

ESE: European Society of Endodontology

NiTi: Nickel-Titanium

PTN: ProTaper Next files

Mx: Maxillary

Mn: Mandibular

 

INTRODUCTION

Root canal treatment is a complicated procedure that requires careful attention to detail and meticulous execution. This allows for effective cleaning and shaping of the root canal while avoiding any procedural error that may impact treatment outcome. A prerequisite to achieving treatment at a high standard of care includes inventive training of dental students to elicit high quality treatment.

Quality guidelines in root canal treatment

The European Society of Endodontology (ESE) in 2013 expressed their concern that despite tremendous technical advances in endodontics, studies continue to exhibit displeasing technical results for endodontic treatment in European societies.¹ The ESE 2013 guidelines quote several studies to prove that these results are a reflection of the achievement of the initial proficiency shown in undergraduate training where requirements remain va-riable.^2-6 The society also emphasized the necessity of ensuring that undergraduate practice is performed to a standard that confirms thorough understanding of the crucial factors that play a role in clinical outcomes.

The ESE (2006) reported a set of guidelines for undergraduate syllabi, to promote the advancement of high quality undergraduate dental teaching. According to these guidelines, the student is expected to possess the ability to perform nonsurgical endodontic treatment on single and multi-rooted teeth. The guidelines also included the expectation that students should identify and know how to avoid any iatrogenic errors that might occur with conventional endodontic treatment.^7,10 Educational guidelines dictate that dental schools ensure the competence of each graduating student in the field of endodontics.¹¹

Eleftheriadis and Lambrianidis (2005) proposed that the assessment of technical outcomes of endodontic treatment and the detection of iatrogenic errors are based on the immediate postoperative radiographs.² Consequently, the ESE (2006) advised that the quality of root canal Alling should be assessed through postoperative radiographs.¹⁰

The use of periapical radiographs in root canal treatment

Periapical radiographs are commonly in endodontic treatment for preoperative diagnostic assessment, working length determination, master apical file fit, master cone and postoperative assessment of the quality of obturation.

Endodontic treatment success is often predicted by the quality of the root canal treatment, as depicted on postoperative radiographs. Although Siqueira (2001) agrees with this recommendation, he cautions that the radiographic judgement of the root filling may not be indicative of root canal sealing.¹² The author concluded that the major cause of failure of most well-treated endodon-tic treatment cases is due to persistence of infection. It should be recognized that periapical radiographs represent a two dimension image and have limitations, such as the superposition with adjacent tooth structures, especially in the region of the maxillary molars.^13,14

Numerous studies have used postoperative radiographs to assess the quality of root canal treatment. Table 1. describes studies that assessed the quality of endodontic treatment performed by undergraduate students by examining postoperative radiographs. Although there is considerable consistency among the studies listed, not all the studies used the same criteria.

Criteria used to determine the quality of root canal treatment

Various studies have shown that the outcome of root canal treatment is dependent on the technical quality of the root canal filling.^24-26 In addition, studies have also used the absence of voids and the length of root fillings as assessment criteria.^24,27,28 Furthermore, Santos et al. (2010) considered the length, density and taper of root canal fillings in their assessment of the quality of root canal treatment, while Bottacz-Rzepkowska and Pawlicka (2003) concluded that the radiographic technical quality of root canal treatment is more related to the health of the periapical area, rather than substandard root fillings.^29,30 Ramachandran Nair (2003) reinforced the view that the primary cause of postoperative apical periodontitis (AP) in well-treated teeth is due to the presence of microbial infection.³¹

When examining postoperative radiographs, several criteria act as predictors of successful endodontic treatment outcome. Some of which include: (1) length of root canal filling, (2) density of the root canal filling, and (3) taper of the root canal.

Length of the root canal filling

The length of the root canal filling is an important evaluative parameter and is determined by measuring the apical terminus of the obturation from the radiographic apex of the tooth on postoperative radiographs. Zhong et al. (2008) showed that microbes and their by-products are responsible for the failure of endodontic treatment in teeth with inadequate length of condensed obturation material and a low density of the obturation.³²

Underfilling results in voids in the apical region of the canal which subsequently provides spaces for bacterial colonization. On the other hand, overfilling of the obturation material is the extension of a semi-solid or solid core root canal material beyond the apical foramen.³³ Schaeffer et al. (2005) stated that extruded obturation material beyond the radiographic apex correlated with a decreasing prognosis of root canal treatment while Siqueira (2001) associated overfilling with intraradicular and/or extraradicular concomitant infections.^12,34 The ESE has suggested that the working length should be determined between 0.5 -2 mm from the radiographic apex.¹⁰ This is the guideline that is prescribed at the University and was thus used in this study.

Density of the root canal filling

The density of the root filling is another essential factor that influences the outcome or prognosis of endodontic therapy. Kirkevang et al. (2000) found that the presence of voids in root canal Allings have a substantial impact on the incidence of AP.³⁵ Furthermore, Hommez et al. (2002) found that the incidence of AP had a 47.1% occurrence in samples of non-homogeneous root canal filling, and a 27.7% occurrence in samples of homogeneous root canal filling.³⁶ Periapical radiographs are used to determine the quality of root canal treatment by qualifying the homogeneity of obturation, which depends on the absence or presence of voids.⁶ In this study, the presence of voids in the root filling was considered unacceptable.

Taper of the root canal filling

The taper of the root canal is defined by Schilder (1974) as a continuous tapered funnel shape of the root canal system to enable cleaning and facilitate obturation.³⁷ Root canal taper is a reflection of shaping the root canals and not the obturation. Arvaniti and Khabbaz (2011) reported that there was no substantial difference in root canal cleanliness between the different tapers (0.04, 0.06 and 0.08) in root canals that were prepared to an apical size 30.38 Zogheib et al. (2012) assessed the influence of different tapered preparation on the sealing ability of Real Seal 1 at the apical 5 mm of the obturated canals using micro-CT for analysis.³⁹ The results showed that the smallest taper size (0.04) had significantly greater volume of voids, while the large taper sizes (0.06 and 0.08) revealed fewer voids. In this study any inconsistent taper of canal preparation from crown to apex was considered unacceptable. Table 2 portrays the results of various studies utilizing length, density and taper to determine the quality of the root canal treatment.

Following the implementation of the revised endodontic curriculum at the Wits School of Oral Health Sciences in 2012, no study has been done to assess the impact of the curriculum change on treatment outcomes. The aim of this study was to assess the quality of root canal treatment performed by undergraduate students at the Wits Oral Health Centre.

 

MATERIALS AND METHODS

This was a retrospective study, composed of 299 postoperative periapical radiographs of patients treated by 3^rd, 4^th and 5^th year undergraduate dental students, in the Wits Oral health Centre at the School of Oral Health Sciences (University of the Witwatersrand), between January 2013 and December 2015.

The endodontic patients' radiographs were examined using a magnifying lens (2x magnification) and an endodontic ruler in a dark room using a radiographic viewer. Twenty cases, not included in the study sample, were used to compare the interrater agreement between the two main investigators. Ethical clearance and permission to conduct the study was obtained from the Human Research Ethics Committee (Wits University) and the Risk Assesment committee (Wits Oral Health Centre).

Criteria for study inclusion incorporated all teeth endo-dontically treated by the third, fourth and fifth year undergraduate students under supervision, teeth with complete root apices excluding 3^rd molars, completed root canal treatment, patient files with postoperative radiographic records of good condition, and postoperative radiographs exhibiting a minimum of 2 mm beyond the root apex. Any teeth with complex anatomy such as severe root canal curvature, root fracture, or root resorption (external or internal) prior to root canal obturation were excluded from the study.

The three main criteria assessed on the postoperative radiographs were: length, density and taper. Length of the root Alling was characterised as 'Adequate' where the root Alling was 0-2 mm from radiographic apex, "Overfilling" when the root filling extending beyond the radiographic apex, and "Underfilling" when the root filling was >2 mm from the radiographic apex.

The Density of the root filling was regarded as "Acceptable" when there were no voids between root filling and root canal walls or within the root filling, and "Unacceptable" when voids were present between root filling and root canal walls or within the root filling. The taper of the root canal was regarded as "Acceptable" when there was a consistent taper from the orifice to the root apex, and "Unacceptable" when the taper was inconsistent.

IBM SPSS 24.0 was used for analysis. Cohen's Kappa was used to measure the inter-rater reliability of the root canal treatment variables between two clinicians. Descriptive statistics of frequency and percentages were used for data summary. Inferential statistics using Fischer's exact test were used to determine the association between independent and dependent variables.

 

RESULTS

Inter-rater agreement was determined using Cohen's kappa across the three assessed parameters. The results was determined as 1.00 (length of root filling), 0.93 (density), and 0.77 (taper).

The distribution of the 299 included patient cases for the third, fourth and fifth year students were 85, 106 and 108 respectively. The distribution of tooth location and position are shown in Table 3.

The quality of the root canal filling was determined by reporting the length, density and taper of the root canal filling. The total number of canals with adequate length was 68.9%, while total acceptable density of root filling was 73.6%, and the total acceptable taper of root filling was 70.9%.

The adequate length and overfilling results were higher in teeth with straight roots, than in teeth with moderately curved roots where a higher frequency of underfilling was noted. Figure 1 and Figure 2 summarizes the results of length, density and taper by tooth type and location across the three years of study.

 

 

The highest acceptable density and taper was recorded for central incisors, while the lowest was noted in sec-ond molars. 'Acceptable' density and taper was greater in teeth with straight roots than in teeth that had moderately curved roots.

Acceptable root canal filling

An acceptable root canal filling is based on length and density or length, density and taper of the filling (Figure 3). Acceptable root filling based on the length and density were greater than 63% in all years. However, the treatment performed by the fifth year students (71.9%) revealed the highest acceptable root filling when compared to the third year students (69.4%) and the 4^th year students (63.2%).

 

 

Acceptable root canal filling based on the length, density and taper were greater than 55% in all student years. However, the teeth treated by the 4^th year students were the least acceptable result (55.7%) when compared to the 5^th year (68.5%) and 3^rd year (63.5%) students, as shown in Figure 3.

The Fischer's exact test was used to examine the association between year of study and the quality of root canal filling. The test revealed that there was no significant association between the year of study and all the measures of quality of the root canal filling (p>0.05).

 

DISCUSSION

A new undergraduate curriculum was implemented in 2012 at the University of Witwatersrand, whereby the endodontic undergraduate preclinical course began in the second year, instead of the third year of study. Several changes were made to the didactic and clinical teaching schedule.

The absolute minimum clinical quota for undergraduate students at Wits Oral Health Centre is shown in Table 4. All clinical requirements (quota) for clinical students must be completed by the penultimate month of their final year of study.

 

 

The staff: student ratio is 1:7 for preclinical teaching and 1:5 for clinical teaching at the Wits Oral Health Centre.

The preclinical staff:student's ratio was superior to those described by other authors with ratios of (1:8),¹¹ (1:12)¹⁹ and (1:15).²³ The time dedicated to preclinical endodontic teaching at Wits University is 60 hours, which is greater than the University Dental School and Hospital, Cork (48 hours),¹¹ Glasgow Dental Hospital and School (32 hours)¹⁹ and the University of the West Indies (54 hours),²¹ while it was similar to the University of Jordan (56 hours).²³

The clinical staff: student's ratio at Wits University of 1:5 was lower when compared to several other universities including Jordan University of Science and Technology (1:6),¹⁷ Aristotle University of Thessaloniki (1:8),² University Dental School and Hospital, Cork (1:8),¹¹ Glasgow Dental Hospital and School (1:12 for 5^th year),¹⁹ King Saud University (1:7 for 4^th year and 1:2 for 5^th year),²⁰ the University of the West Indies (1:10)²¹ and Anally the University of Jordan with a ratio of 1:12.²³ It is important to consider the influence of staff:student ratio when considering the outcomes of patient treatment under supervision. It is expected that a lower ratio allows for greater supervision decreasing the opportunity for mishaps while improving treatment quality and outcome.

Standard endodontic protocol in the 3^rd and 4^th years included the step-back preparation and lateral condensation obturation techniques. Stainless steel K-files with a triangular cross section were used with all files and cones being ISO 2% tapered. A 2% sodium hypochlorite irrigation solution was advocated for irrigation, coupled with the use of EDTA (RC Prep) for chelation and lubrication. The use of 2.5x magnifying dental loupes was compulsory for all endodontic procedures. The root canal sealer available in the WOHC polyclinic was Topseal (Dentsply, South Africa).

The 5^th year students predominantly utilised rotary instrumentation for canal preparation which included ProGlider (Dentsply, South Africa) files for glide path preparation followed by Protaper Next (Dentsply, South Africa) files to complete canal preparation. The endodontic clinical protocol specified certain radiographs that should be taken during and after every root canal treatment.

Thus, no additional radiographs were required for this retrospective study. Teeth were excluded from the study when these radiographs were unreadable or unavailable. Standard endodontic protocol ensured that all endodon-tic radiographs be taken using an Endo Rinn® instrument, at a preset exposure to ensure image quality.

The European Society of Endodontology (1992) recommended that students have to perform endodontic treatment on uncomplicated teeth (single and multirooted), and they have to be familiar with problems encountered in complicated endodontic treatments.⁷

The ESE, in their definition of uncomplicated treatment, included tooth curvature of less than 15° from the axis of the roots. The 3^rd year students treated only the anterior teeth of which 75.3% were straight, while the 4^th year students treated posterior teeth (61.3%) for the first time in the clinic, of which 58.5% were moderately curved teeth.

These differences in the complexity of cases between the different student groups explain why the result of the 3^rd year students in general was better than the 4^th year students. There was a significant difference in the number of roots and root curvature of the teeth treated between the 3^rd, 4^th and the 5^th year students (p<0.001). One method to limit relatively difficult cases being allocated to novice undergraduate students is for supervisors to screen and allocate patients accordingly to ensure careful patient selection for students in the different clinical years of study.

The third year students had the lowest percentage of underfilled canals when compared to the 4^th and 5^th year students (16.5%, 29.2% and 19.4% respectively). Yet interestingly, the 3^rd year students had the highest number of overfilled canals (14.1%, 7.5% and 6.5% respectively). This was attributed to this these students only treating anterior teeth with relatively wider and straight canals with little difficulty in finding the full length. However, a possible explanation for their high rate of overfilling is their inexperience and their inability to confine the instrumentation to within the canal. Thus, the high rate of overfilling was possibly due to over-instrumentation.

Thus, it is advised that greater emphasis be placed on working length control throughout canal preparation procedures during preclinical teaching. The density and taper of maxillary teeth treated by the 3^rd year students was better than in the mandibular teeth. The simple explanation for this is the relative difference in the size of the canals; that maxillary teeth have larger canals than man-dibular teeth.

In this study, 35.5% of the teeth assessed were treated by the 4^th year students. 61.3% of these teeth were posterior teeth with 58.5% of them presenting moderately curved roots. With the exception of overfilling, the results of the main criteria assessed (length, density and taper) show that the fourth year students produced the lowest quality rating among all student years.

Anterior teeth treated by the 4^th year students displayed a higher prevalence of adequate length, underfilling, acceptable density and taper when compared to posterior teeth. These results were attributed to the inexperience of this student cohort in treating posterior teeth. In addition, the inexperience of the students were compounded by the allocation of relative challenging root canal anatomy cases.

75% of treated teeth by the 5^th year students were posterior teeth, with 72.2% of these teeth presenting with moderately curved roots and 67.6% being multirooted teeth. The 5^th year students had the best adequate length and overfilling results which highlighted the impact of experience in the ultimate quality of root canal treatments, more so when treating teeth with more challenging anatomy. In addition, the use of rotary endodontic systems and more advanced methods of magnification account for the superior findings in this student group.

Total acceptable root canal filling

The total acceptable root canal filling of this study, based on the length and density, was 67.9%. This result was higher than the studies by Eleftheriadis and Lambrianidis (2005) at 55.3%, and Khabbaz et al. (2010) at 54.8%. Similar to other studies, the 5^th year student cohort performed superior.⁶

The total acceptable root filling based on the length, density and taper was 62.5%, which was better than the University of Pretoria study by Mostert & Jonker (2016) (59,66%), Barrieshi-Nusair et al. (2004) (47.4%), Er et al. (2006) (33%) and Smadi et al. (2015), which was 29.2%.^17,18,23,40 Again, similar to Balto (2010), the 5^th year student cohort performed superior to earlier years of study.²⁰ Table 5. and Table 6. summarize the results of previous studies across the 3 parameters assessed, and include the results of this study for comparison.

 

CONCLUSIONS

The results of this study indicated that the quality of root canal treatment performed by undergraduate students is similar to other studies conducted at various dental schools around the world. The change in the curriculum has been justified, though room for improvement exists. There was a tendency for third year students to overfill due to over-instrumentation of anterior teeth.

The 5^th year students had better results because of their relative experience and the opportunity to use dental operating microscopes. Endodontic teaching should further emphasise the importance of length control during endo-dontic treatment and more stringent steps may be necessary during patient allocation and clinical supervision of fourth year dental students.

 

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Correspondence:
Ebrahim Patel
Department of Paediatric and Restorative Dentistry, School of Oral Health Science
7 York Road, Parktown
Johannesburg, 2193, South Africa.
Email: ebrahim.patel@wits.ac.za

 

 

Author affiliations:
1 . Ebrahim Patel: Principal author - 45%
2 . A Alaali M Ehbesh: Second author - 35%
3 . Ismail E Munshi: Third author - 15%
4 . Saidah Tootla: Fourth author - 5%