In this study, group comparisons showed no significant differences between the pulp disease groups at any time point. No interactions and no significant differences in changes over time were observed between the two groups. While both groups showed improvement of QoL over time after treatment, this did not differ between the two disease groups. In both groups, patients’ expectations of receiving endodontic treatment remained unchanged after treatment.

First, it is necessary to consider the generalizability of the results and the appropriateness of the comparison between patients with these pulp diseases. In this study, patients were included using the continuous rather than the random sampling method. Typically, a bias in the background factors of both groups was present; however, in this study, no significant differences in social, systemic, or oral health-related factors were found between groups. A slight difference in the average age and the sex of patients with the two dental pulp diseases in Indonesia was observed. However, Indonesia has a heterogeneous treatment environment: high-quality care is generally obtained in metropolitan areas, whereas the number of medical facilities in rural areas is limited [24]. Maintenance costs also vary between urban and rural areas, with urban areas generally being more expensive [25]. The data used in this study were collected from urban areas and therefore our findings may not be applicable to all endodontic patients. However, these results are likely similar to those of endodontic patients in developed countries.

Additionally, this study compared two pulp diseases for which the validity of the comparison between the two diseases had to be confirmed. Irreversible pulpitis usually occurs when infection or damage to nerves or blood vessels deep within the tooth is present. It is characterized by severe, persistent, and referred pain [22, 26]. In contrast, pulp necrosis is a condition in which the nerve tissue of the tooth has undergone necrosis (usually asymptomatic), tooth discoloration and halitosis are present, the infection has spread to the periapical tissue and surrounding bones, and tooth function is lost [16, 27, 28]. Endodontists often ignore the clinical manifestations experienced by patients with these two pulp diseases and then perform endodontic treatment without considering the patient’s QoL, and in particular the effects of these two pulp diseases. Therefore, the comparison made in this study is considered valid, and the results are meaningful.

In previous studies, irreversible pulpitis resulted in a decrease in QoL due to the pain experienced by patients, which was the main impetus for seeking emergency dental care [29]. Our results suggested that the response of QoL improvement on the physical and psychological subscales after endodontic treatment was higher for patients with irreversible pulpitis than for those with pulp necrosis. The decrease in psychological QoL caused by irreversible pulpitis is due to the orofacial referred pain, which reduces social activities of patients, resulting in absenteeism, dependence on analgesics, decreased ability to cope with dependents, lack of sleep, and difficulty in eating and speaking [30].

However, outcome parameters on the expectation parameters for endodontic treatment did not differ over time, between groups, or show interactions. Treatment of diseases with severe clinical symptoms, such as chronic pain, often increases patients’ expectations of the treatment outcomes [31]. Despite this, the treatment of irreversible pulpitis did not change patients’ expectations, possibly due to the lack of explanation by endodontists about the need, importance, and outcome of such treatment. In Indonesia, although inappropriate for medical and dental services, patients’ informed consent is often overlooked [32, 33]. Lack of communication between the dentist and the patient can lead to the patient lacking comprehension of the plan and treatment options [34]. Because immediate treatment is required, time constraints cause difficulty in communication between dentists and patients, as most of these dental treatments have a long duration [35]. Additionally, it is caused by a lack of awareness among dental healthcare providers, such as dentists and dental hygienists, of the importance of informed consent. This lack of awareness and the lack of patient education regarding care will result in patients’ distrust of dental providers [36]. An explanation of the endodontic treatment to be performed by endodontists is needed to increase patients’ expectations of endodontic treatment. Therefore, informed consent for patients with irreversible pulpitis is one of the determining factors by which endodontists can improve the patient’s QoL after endodontic treatment.

Pulp necrosis, which occurs when irreversible pulpitis is not treated properly, is the final stage in the pathological course of caries. In the early stages, symptoms may include severe pain due to pressure caused by pulp inflammation and signs of nerve hypersensitivity around the inflamed area [22, 37]. If not properly treated, the infection can spread to the gingiva and around the face, causing swelling [16]. Because pulp necrosis is an advanced form of irreversible pulpitis, it is plausible that the OHQE scores were lower in this group than in the irreversible pulpitis group at all time points. Additionally, one of the characteristics of advanced pulp necrosis is that it is asymptomatic [27]. Because the OHQE used in this study was an OHRQoL scale that focused specifically on endodontic pain, the significantly low OHQE scores in the pretreatment phase likely reflected the presence of pain. However, the results of this study did not show significant differences between irreversible pulpitis and pulp necrosis groups in the pretreatment phase; thus, patients with relatively symptomatic pulp necrosis may also have been included. Therefore, although endodontic treatment methods for pulp necrosis do not differ significantly, attention should be paid equally to patients with or without symptoms, and treatment explanations and informed consent should be provided to meet patient expectations for endodontic treatment.

Endodontic treatment is effective for irreversible pulpitis and pulp necrosis, followed by prosthetic treatment performed after removal of the infected tissue and subsequent root canal filling [38]. However, endodontic treatment for pulpal necrosis in this study generally required a longer treatment duration than that for irreversible pulpitis. A longer treatment duration is expected to increase the opportunity for dentists to communicate and to provide explanations regarding the treatment to patients. However, an extension of the treatment duration can lead to a decrease in the patient’s QoL, such as an increase in the effort required for the patient to visit the hospital or the occurrence of pain during treatment [39]. In this study, our statistical model investigated an interaction between time and pathological factors, but found none. Therefore, it is important to provide effective questions to endodontic patients, as well as shorten the duration of the endodontic treatment.

The digestive health and sense of taste issues found in this study are concerns that should be addressed by the endodontist before treatment, as both of these can be associated with decreased appetite. The related questions were “Have you felt that your sense of taste has worsened because of dental pain?” and “Have you felt that your digestion has worsened because of dental pain?” The results of the current study are acceptable, as previous research has also indicated that untreated dental caries can lead to both irreversible pulpitis and pulp necrosis, resulting in decreased appetite [40]. Both groups may experience a reduction in appetite because of pain symptoms that cause distress during digestion and tasting. Therefore, endodontists should focus on monitoring the dietary intake of patients with irreversible pulpitis and pulp necrosis to preserve the patient’s digestive health. Furthermore, endodontists also need to pay attention to patient expectations regarding pain reduction after endodontic treatment using the question “Have you ever felt that root canal treatment can eliminate your dental pain?” A previous study showed that immediate treatment of symptomatic irreversible pulpitis or apical periodontitis was more successful in reducing pain [41]. Thus, the results of this study are acceptable. Expectation scores were reportedly lower in patients with pulp necrosis than in those with irreversible pulpitis. The high expectations of patients with irreversible pulpitis in this study may stem from the fact that they endured severe pain before treatment and achieved instant post-treatment pain relief.

This study had a few limitations. First, in this study, data on the periapical status of patients were not obtained. Therefore, all patients likely to have periapical disease may have been included in the classification of patients with pulp necrosis. Second, no data were available on the duration of endodontic treatment in each patient, considering that the need for the duration of endodontic treatment in each patient varies. Third, there were no data on the level of dental health literacy in each patient, which could affect the research results. Lastly, the current study reflected cases in which only one tooth required endodontic treatment, rather than the complete oral health status of the patients. These limitations can introduce bias into the research, resulting in potentially inaccurate findings. In future, prospective observational studies on a larger scale are required to overcome these limitations, reduce the prevalence of bias in research, and ensure that the findings are more representative of the whole population. Additionally, more endodontists are likely to become aware of the subjective judgments of their patients as better research results are obtained.

In conclusion, we found no significant difference in QoL enhancement by endodontic treatment between the two pulp diseases. The physical and psychological subscale scores of the OHQE of each group improved over time. Conversely, patients’ expectations regarding endodontic treatment remained unchanged after treatment. These results indicated that patients continue to lack comprehension of the importance of the endodontic treatment that they have been receiving. Hence, dental providers, particularly endodontists, should contemplate elucidating the significance of endodontic treatment for patients and address the factors that enhance patient expectations.