Prevalence of periradicular radiolucencies and its association with the quality of root canal procedures and coronal restorations in an adult urban Indian population.

AIMS: The aim of this cross-sectional study was to determine the prevalence of periradicular radiolucencies (PR) from an urban adult Indian population and to investigate the quality of root canal procedures and coronal restorations and their association with prevalence of PR in root-filled teeth. SETTINGS AND
DESIGN: Cross-sectional study.
MATERIAL AND METHODS: A total of 1,340 subjects (18+ years of age) who reported for non-emergency dental care to 5 different dental care centers had their panoramic radiographs taken during the period from January to December 2013. The periradicular status of 30,098 teeth in these radiographs was evaluated using the Periapical Index Score (PAI). The assessment of the technical quality of the procedure was evaluated based on the criteria of root canal filling length and quality of coronal restoration. STATISTICAL ANALYSIS USED: The data was analyzed statistically by chi-squared test and odds ratio.
RESULTS: PR was found in 65% of subjects (n = 865) and 5.8% (n = 1,759) of the 30,098 teeth evaluated (4.30% untreated teeth and 1.53% were root-filled teeth). In all, 4.1% of the teeth (n = 1,234) had some filling material in the root canal(s) and the prevalence of PR in these root-filled teeth was 37.4%, while the remaining 62.6% of root canal-filled teeth showed no evidence of PR. PR occurred significantly more often in teeth where root canal filling was filled more than 2 mm short of radiographic apex or when root filling extruded through the apex.
CONCLUSIONS: The prevalence of PR in teeth with untreated root canals in India is 4.30%, which is more than twice the weighted world average, while the prevalence of root-filled teeth (4.1%) is lower than the world average (9.6%). The prevalence of PR in root-filled teeth in India is comparable to that in other populations. Inadequate root canal treatment and poor quality of coronal restoration were associated with increased prevalence of PR.

INTRODUCTION

A cross-sectional study is the best method to assess the status of a disease or the outcome of a treatment intervention in a population.[1] On the other hand, longitudinal studies that evaluate the quality and prognosis of endodontic treatment have been frequently done in dental schools or in specialist clinics in a controlled scenario.[2345] Longitudinal studies may not possibly reflect the situation in an average dental clinic and overlook the quality of root canal filling in routine community general dental practice.[6] Thus, a cross-sectional survey based on patients reporting to general practitioners for non-emergency dental care would provide a more accurate assessment of the burden of disease in the general population as well as quality of treatment being provided. Many cross-sectional studies confirm the high prevalence of periradicular radiolucencies (PR) that vary from 0.5-13.9% overall and PR rates of over 33% in root-filled teeth have been reported in various worldwide populations.[1] The aim of this multi-centric cross-sectional study was to determine the prevalence of PR and its association with the quality of root canal procedures and coronal restorations in an adult urban Indian population.

MATERIALS AND METHODS

Patient selection

The sample consisted of 1,340 subjects aged 18 and above presenting consecutively as new patients seeking routine non-emergency dental care at 5 dental care centers (each representing the five urban metropolitan cities namely Chennai, Bangalore, Hyderabad, Delhi and Pune in India) during the period from January to December 2013. Patients who were younger than 18 years or having less than 8 remaining teeth were excluded. The scientific and ethical committee of the university approved the study and written informed consent was obtained from all the patients.

Radiographic examination

All the participants had full mouth panoramic radiographs taken. The digital images were examined using Photoshop 6.0 software (Adobe Systems Inc., San Jose, CA, USA) at a ratio of 1:1. Two examiners were calibrated to record the findings independently using 50 panoramic radiographs that were not included in the study. The intra-observer agreement on PAI scores on the 50 test patients produced a kappa score of 0.81. When in disagreement a third observer, a highly experienced endodontist, was consulted.

Radiographic evaluation

The presence or absence of PR in each of the sample teeth (n = 30,098) was evaluated on the basis of the periapical index (PAI).[7] The evaluation of PR was made using a scale ranging from 1 to 5. A healthy tooth corresponded to PAI 1 (normal periradicular structures) or PAI 2 (small changes in bone structure), whereas diseased teeth were scored as PAI 3 (changes in bone structure with some mineral loss), PAI 4 (periodontitis with well-defined radiolucent area), and PAI 5 (severe periodontitis with elements indicating expansion of the lesion). The worst score of all canals was taken to represent the PAI score for multi-canaled teeth.

The evaluation of the quality of root canal filling and coronal restorations was based on the criteria described by Tavares et al.,[8] which is a modification of Tronstad et al's.,[9] criteria:

Root Canal Procedure

Adequate: All canals obturated. No voids present. Root canal fillings end from 0-2 mm short of the radiographic apex.

Inadequate: Root canal fillings end more than 2 mm short of the radiographic apex or grossly overfilled. Root canal fillings with voids, inadequate density, unfilled canals, and/or poor compaction.

Coronal restoration

Adequate: Any permanent restoration that appeared intact on a two-dimensional radiograph.

Inadequate: Any permanent restoration with detectable radiographic signs of overhangs, open margins or recurrent caries, or presence of temporary coronal restoration. Teeth with no coronal restorations, permanent or temporary, were also included in this group.

The data obtained were statistically analyzed by means of the chi-squared test with significant level set at 5% (P ≤ 05) and the reliability was determined using odds ratio.

RESULTS

The periradicular status of 30,098 teeth was evaluated for 1,340 patients radiographically. The presence of PR was detected in 5.8% (n = 1,759) of the 30,098 teeth evaluated. In all, 65% (n = 865) of the 1,340 subjects had a prevalence of at least 1 PR. The number of PR lesions per patient varied widely from 1 to 7 [Table 1]. A significantly high proportion of the sample population (28.8%) showed evidence of at least 1 PR lesion. More than 21% of the subjects had 2 PR lesions while 15% of the population had 3 and above PR lesions per patient.

Table 1

Number of teeth with periradicular radiolucencies (PR) in different patients

The prevalence of PR in the tested adult urban Indian population was 5.8% (Teeth with untreated canals with PRà 4.3% and root-filled teeth with PRà 1.53%). The teeth with the highest prevalence of PR were the maxillary and mandibular right first molars (11.86% and 17.16% respectively), followed by maxillary left first molar (9.83%).

There were 1,234 teeth (4.10%) with root canal filling material, denoting previous attempts at root canal procedures. Maxillary teeth had been root filled significantly more often than mandibular teeth (P ≤ 0.001). The mandibular right first molar and the maxillary left first molar were the most common root-filled teeth. The least common were the mandibular lateral incisors.

PR was seen associated with 462 (37.4%) of the 1,234 root-filled teeth. The remaining 1,297 cases of PR were associated with teeth that had not been root filled. The logistic regression analysis of root filling as an independent variable for the variable ‘periapical status’ demonstrated that root filling affected significantly the periapical status (X2=2326, P ≤ 0.001; odds ratio with 95% confidence interval: 11.18 < 14.44). Of 517 teeth with unsatisfactory length/extension of root canal, PR was associated in 332 (64%) teeth [Table 2a].

Table 2a

Correlation between the length of root canal filling and periradicular status

The correlation between the quality of root canal treatment and the periradicular status was determined radiographically. PR was more commonly associated with teeth in which the root canal was filled less than 2 mm from the radiographic apex compared to teeth that has been adequately filled (X2=284.7, P ≤ 0.001, odds ratio with 95% confidence interval: 4.25 < 7.04). When there was extrusion of filling material through the apex, PR was around 86% (P ≤ 0.001; odds ratio with 95% confidence interval: 5.49 < 28.50) [Table 2b].

Table 2b

Regression table of the periradicular condition root canal-filled teeth

The correlation between the quality of coronal restorations and the periapical status was also determined [Table 3a]. PR was associated with teeth that had inadequate coronal restorations more often than with teeth in which the coronal restorations were adequate (X2=12.91, P ≤ 0.001, odds ratio with 95% confidence interval: 1.23 < 2.00) [Table 3b].

Table 3a

Correlation between periapical and coronal status of root-filled teeth

Table 3b

Regression table of the periradicular condition of coronal status of root-filled teeth

DISCUSSION

The subjects selected in the present cross sectional survey consisted of individuals seeking routine non-emergency dental care at 5 dental centers (each representing the five largest urban metropolitan cities in India). This study evaluated more than 30,098 teeth representing 1,340 urban adult subjects radiographically. The sample size and population was chosen to be more representative of the urban general population being assessed.

Cross-sectional surveys provide data that are observational in nature. Cross-sectional studies have also the advantage of analyzing large sample sizes thereby diluting interpretation biases. The data analyzed has its limitation of being restricted to the available information at one point of time.[8] However, cross-sectional surveys are less prone to be biased in comparison to longitudinal studies.[10]

PAI scoring system has been used as a means of assessment of PR in many epidemiological studies.[61112] In comparison to the full mouth series of periapical radiographs, panoramic radiographs have lower patient radiation doses and diagnostic sensitivity reaching 86-96%.[13] Hence, PAI scoring of panoramic radiographs was preferred in the present study because it provides a validated and categorized description of periapical lesions confirmed by histological evaluation.[14]

The prevalence of PR in our urban adult Indian study population was around 5.8%. This is comparable to the weighted world average (5.4%) of prevalence of PR.[1] However, the burden of untreated disease i.e., teeth with untreated canals showing PR in our study was high (4.30%, n = 1,297). This is more than twice the weighted world average of 2.1% [Table 4]. This is broadly equivalent to an average of at least one PR lesion per adult.

Table 4

Prevalence of periradicular radiolucencies (PR), root canal treatment (RCT), and treated and untreated teeth with PR in a weighted world population in comparison with our study

Root canal-treated teeth in our study were estimated to be around 4.1% of the sample population, which is lower than the weighted world average of 9.6% [Table 4]. A high proportion (37.4%) of the teeth that had received root canal therapy had PR. This high prevalence of PR in root-filled teeth is in close agreement to other populations in varied geographic locations.[1516] The combined finding of the high prevalence of PR in untreated teeth and lower prevalence of root-filled teeth than other populations represents a huge therapeutic challenge considering the current population of India is 1.21 billion with 31.16% being urban settlements. The quality of endodontic treatment has a strong influence on the status of the periradicular tissues.[21718] An evaluated root filled tooth was considered to be inadequate when the root filling was more than 2 mm short of radiographic apex or when there was evidence of root filling extrusion. In the current study, 61.7% of inadequately root-filled teeth were diagnosed having PR [Table 4], while other studies show varying PR rates from 31.5%[19]; 39.3%[15] to 67.6%.[16]

The limitation of this study is that a two-dimensional radiograph does not take into consideration the possibility that many lesions could be reducing in size or healing although they might still be showing a radiographic presence. This may be considered a minor drawback in this form of cross sectional prevalence studies. The other drawback of radiographic assessment employed in this study would be the potential for voids along inadequate root fillings to be invisible because of superposition of root filling materials.[20] This limitation could be overcome by using cone-beam computed tomography (CBCT) instead of two-dimensional radiographs.[21] The newer CBCT technology could be employed as a more objective tool for assessment in future cross-sectional trials.

PR was noticed in 86.5% (n = 45) of teeth when filling material was radiographically evident extruding beyond the apex. Failure in overfilled teeth can be a result of previous over instrumentation of an infected root canal that propelled infected dentin chips to the periradicular tissues.[22] In grossly under-filled cases, a long segment of the root canal is highly likely to have not been cleaned, leaving enough space for proliferation of residual microorganisms.[23]

The results of the present study also showed a significant influence of the coronal restoration on periradicular status. Almost 44.6% (n = 185) of root-filled teeth showed evidence of PR when the coronal restoration was inadequate. In similar studies on the influence of coronal restorations, the prevalence of PR was around 42.3%[15] and 51%[24] when coronal restorations were found to be radiographically compromised.

CONCLUSION

The prevalence of PR in teeth with untreated root canals in India is more than twice the weighted world average. The prevalence of root canal treatment (4.1%) was found to be considerably lower while the prevalence of PR in root-filled teeth in India is comparable to that in other populations. This study reiterates that inadequate root canal treatment and poor quality of coronal restoration are associated with an increased incidence of PR.