Predictors of apical periodontitis in root canal treated teeth from an adult Nepalese subpopulation: a cross-sectional study

The current study aimed to evaluate the prevalence and determining factors of AP in root canal treated teeth from an adult Nepalese subpopulation of Madhesh Province. The findings of this study demonstrate that the AP prevalence in root treated teeth was 31.7%, which is comparable to earlier studies that used panoramic radiographs [23, 24]. A systematic review with meta-analysis [11] showed AP presence in 36% of cases. High AP prevalence observed in this study was mostly associated to the higher prevalence of teeth with inadequate root canal therapy.

This study marks the inaugural research effort of its kind conducted in the Madhesh Province. The sample examined consisted of patients who visited dental OPD of NMCTH Birgunj, situated in the Madhesh Province of Nepal. Similar screening criteria based on dental school patient selection have been employed in several other prevalence studies [16, 21, 24]. As NMCTH Birgunj stands as the sole dental institute and tertiary care referral dental center in Madhesh Province, individuals from all districts of the province avail themselves of its specialized dental services. Madhesh Province, located in the southeastern Terai region of Nepal and bordering Koshi Pradesh to the east and north, Bagmati Province to the north, and India’s Bihar state to the south and west, exhibits a population distribution of 50.1% males and 49.9% females [25]. Nonetheless, it is crucial to note that our subjects did not constitute a random sample of the Madhesh province population; rather, they were individuals actively seeking dental treatment. Therefore, the results are limited to the specific group studied and may not be applicable to the general population. However, in this study, the AP frequency and its associations with variables can be identified.

Based on the existing data, Nepal has a dentist-to-population ratio of 1:20000, nearly three times below the World Health Organization’s (WHO) recommended ratio [26]. The majority of practitioners in the province are general dentists, and the distribution of specialization in subdisciplines is limited. Regrettably, instances of quackery and fraudulent dental practices are noted within the province [26].

In the present study, panoramic radiograph was used to score the periapical status. Several epidemiological studies have used dental panoramic radiographs for evaluating the AP and the technical quality of RCT [16, 24]. Panoramic radiographs were employed in this study due to their availability, given that full-mouth periapical radiographs were not routinely taken in our college. With panoramic images, all teeth present can be visualized on one radiograph and a large amount of data is comfortably accumulated without exposing the individuals to extra radiation. These features make panoramic radiographs beneficial compared to full-mouth periapical radiographs [24]. Additionally, in the identification of periapical lesions, no significant difference has been found between the sensitivities of panoramic and full-mouth periapical radiographs [27, 28]. Contemporary panoramic machines generate higher-quality radiographic images, including improved clarity in the anterior region. Consequently, panoramic radiographs are considered a suitable diagnostic tool for assessing apical lesions in epidemiological studies related to dental care [27, 28].

Our study sample consisted of more females (56.97%) than males (43.02%), which may reflect the considerable interest of females within Nepal in receiving dental treatment. The predominance of female patients has also been shown in similar epidemiologic studies; however, those studies reported that gender did not correlate with the presence of AP [29, 30]. According to our results, females are less likely to have AP development in root canal-treated teeth than males. It is difficult to clarify the observed gender difference in our study. It would make sense if the males underwent root canal treatment when their teeth were in worse condition than females, potentially resulting in a poorer prognosis for therapy in males. Unfortunately, in this study, the preoperative condition, as well as details about the individuals who performed endodontic treatment, were not known. Future studies could help in understanding gender differences in the development of periapical lesions in root-filled teeth. In alignment with our study, Bürklein et al. [31] also observed a gender difference and linked it to diverse biopsychosocial factors affecting pain perception, including genetic factors, endogenous opioid function, sex hormones, pain coping, and gender roles. They further added that women tend to be more pain-sensitive and are more likely to seek dental care [31]. Corroborating our findings on gender differences, Jakovljevic et al. [6], in a meta-analysis, emphasized that despite conflicting outcomes in primary studies regarding the role of gender as a predisposing factor for the development of AP, numerous investigations have highlighted significant variations in oral hygiene practices between males and females.

More than half of the cases evaluated in the present study had inadequate root canal treatment. Similar findings have been observed in earlier studies conducted on different populations [32‐34]. When analysing the causes of inadequate quality of RCTs, it was found that the most common cause was short obturation. This finding is consistent with previous studies [35, 36]. According to Strindberg [37], the success rate of endodontic treatment was highest when the root canal filling length was 1 mm shorter than the apex. The existence of microorganisms in the non-instrumented portions of the root canal may have caused the failure in teeth having short root fillings [38].

Previous studies have shown a lower apical disease rate in teeth with adequately filled root canals [19, 39]. Similar findings were observed in this study where 89.8% of adequate root treated teeth showed absence of AP. Furthermore, consistent with the earlier findings [21, 24], adequately root canal-treated teeth had significantly better periapical health than inadequately treated teeth. According to Siqueir Jr et al. [38], the major aetiological factor of post-treatment AP is persistent intra-radicular infection resulting from inadequate treatment which is similar to the finding of this study. Actually, multivariate logistic regression analysis demonstrated that the quality of root canal therapy was the most significant predictor of AP in root treated teeth. Compared to the teeth with adequate root canal treatment, AP was present approximately eight times more frequently in teeth with inadequate treatment. On the other hand, few cross-sectional studies [40, 41] have revealed no significant relationship between the quality of root canal therapy and the AP presence.

10% of teeth, despite having adequate quality RCTs, still had AP in the current study. This shows that the RCT quality is not the solitary factor affecting the periapical health of endodontically treated teeth. As stated by Moreno et al. [42], the coronal restoration quality is another factor that may affect the apical status. Similar to their findings [42], only 46% of the coronal restorations were classified as adequate in this study. The most common cause of inadequate quality restorations was recurrent caries. This emphasizes the significance of an adequate coronal seal after endodontic treatment. In univariate analysis, significantly better periapical health was found in teeth with adequate coronal restorations compared to the inadequate restorations. This result is analogous with the studies performed in Kuwait [43] and Jordan [29]. However, corresponding to the findings of Bukmir et al. [30], when the multivariate logistic regression was applied, this relationship did not remain significant. The presence of other significant variables in the multivariate model may have influenced this outcome.

In this study, a significant association was found between the type of coronal restoration and presence of AP. This is in agreement with the study by Frisk et al. [44]. This association may be due to the microleakage occurring from poor marginal integrity of the restorations which could not be identified clinically [44]. Moreover, other determining factors of AP might also have influenced the periapical status of the root-treated teeth. Contrary to this association, El Ouarti [45] found no relationship between coronal restoration type and AP.

Combined data for coronal restoration and root canal treatment quality yielded noticeable results. When both coronal restoration and root canal treatment were adequate, only 2.2% of the treated teeth had AP, however if both were inadequate, 53.91% of the teeth had AP. This strongly denotes that both factors i.e., quality of endodontic treatment and quality of coronal restoration play important roles in maintaining the periapical health of root treated teeth. Significantly worse outcome and remarkably increased odds for AP was found when either root canal treatment or coronal restoration was inadequate or when both were inadequate. The meta-analysis conducted by Gillen et al. [46] validated this finding, which showed that the odds for healing capacity of AP increase in teeth with both adequate endodontic treatment and adequate coronal restoration.

The main limitation of the present study was the usage of OPGs for assessing the periapical status. Disadvantages of OPGs are well known including a two-dimensional image of three-dimensional structures, superimposition, anatomic noise and geometric distortion. Furthermore, to be radiographically apparent, apical radiolucency should reach approximately 30-50% of the bone mineral loss. Thus, AP might be existing though not identified radiographically [47]. Cone beam computed tomography (CBCT) surpasses panoramic and periapical radiographs, as three-dimensional view permits more accurate estimation of the size and location of the lesion in addition to the detection of lateral voids and missed canals in the evaluation of technical quality [48]. But all dental practices are not equipped with CBCT [49]. More notably, owing to augmented risk of radiation, the CBCT indications are highly regulated, mostly limited to the zone of interest instead of the complete dentition [50].

Other limitations of this study were the lack of information concerning the evaluated cases which may affect the root canal treatment outcome, for example the operator factor, whether trained or untrained doctor performed the treatment in single or multiple visits and whether permanent restoration was placed just after root canal treatment completion. Furthermore, there was no information about the absence or presence of periapical radiolucency before root canal treatment (no preoperative radiograph was available), elapsed time of endodontic treatment, microbiological environment of the root canal, periodontal status and oral hygiene habits of the patients. Further prospective controlled trials are recommended to evaluate the detail role of each factor responsible for AP, clinically and radiographically.