The maintenance of pulp vitality in teeth affected by deep caries is controversial, with restorative dentists and endodontists offering diverging opinions [1
]. Although it is agreed that “minimally invasive” management strategies are preferable, the definition of “minimal” is a source of debate. Systematic reviews analyzing approaches to vital pulp treatment (VPT) have highlighted that primary studies focus on the invasiveness of the operative procedure, i.e., indirect or direct pulp capping versus partial or full pulpotomy, as well as the type of capping material that is placed [4
]. The outcome measure is invariably the survival, rather than the health of the pulp. Notably, other patient-related outcomes have not gained the same attention [6
]. A key patient-centered outcome measure after VPT is postoperative pain, and the subsequent need to see a dentist on an emergency visit to have root canal treatment performed [7
]. A randomized controlled trial reported unbearable postoperative pain after VPT procedures to be common, occurring in 7–8% of cases without pulp exposure and 51–63% of cases with pulpal exposure [8
], however, other randomized clinical trials have shown considerably less postoperative pain, with severe pain accounting for less than 10% of pulp capping cases [9
]. These results highlight that although unbearable pain is possible after management of carious-exposure with VPT, it is not clear how commonly it occurs; however, it does appear to be more likely than after more invasive treatment strategies such as a full pulpectomy [10
As caries is a biofilm-induced disease [11
], treatments aim to arrest lesion progress. Histologically, as the carious infiltration of the dental hard tissues progresses through the dentin towards the pulp, inflammatory reactions in the pulp tissue increase concomitantly [12
], which rationalizes the focus on the invasiveness of tissue removal during VPT. However, there are other and perhaps more efficient ways to disinfect the dentin/pulp wound. Instead of removing these tissues physically, an alternative and less invasive strategy is to chemically debride the wound. This strategy, i.e., wound lavage, has gained little attention in conservative dentistry, and no randomized trials with an adequate number of patients could be identified [5
]. This is surprising, as wound disinfection is a core principle in interventional medicine [14
]. However, despite the apparent importance of this procedure, published data on the advantages/disadvantages of individual solutions are sparse, even in a non-dental context [15
]. A reason for this may be that wound cleansing studies date back to a time before the dawn of evidence-based medicine. Notably, a 0.5% sodium hypochlorite (NaOCl) solution was identified as the ideal antiseptic to cleanse open wounds during the Great War [16
]. In theory, an NaOCl solution would be ideal to wash the dentin/pulp wound in caries-affected teeth, because NaOCl has unique features, including a high efficacy against biofilms combined with semi selective tissue-dissolving properties on necrotic rather than vital soft tissue [17
]. There appears to be a trend in recent VPT trials to use NaOCl solutions for this purpose, without the clinical data to support this [18
]. On the other hand, while NaOCl has its clear benefits, it may also cause pain because of its caustic potential [19
This is a first communication from an ongoing randomized trial on the impact of wound lavage on the outcome of direct pulp capping in carious exposures. Here, we report on discomfort after the intervention and from early painful failures, defined as being within the first three months, when 2.5% NaOCl or physiological saline were used to wash the pulp after exposure. The research question asked whether cleaning the pulp wound using an inert sterile solution (physiological saline) resulted in reduced early postoperative pain levels along with higher early treatment failures, defined as an emergency visit to have a pulpectomy (root canal treatment) performed within 3 months after the intervention, compared with a lavage using 2.5% NaOCl.
The patient recruitment and all of the pulp capping procedures were completed after 13 months, which included 96 patients requested by the power analysis, who satisfied the inclusion criteria. Approximately 20 to 30 new patients were seen by the investigators per day during their six-day working week, equaling a number of close to ten thousand patients that were pre-screened for the study, resulting in 128 individuals being identified as potential study participants over the study period. Of the 128 potential participants, 27 were excluded, as they had moderate pain (NRS-11 > 3) from the potential study tooth at the day of intervention. Five other individuals who satisfied the inclusion criteria opted out because they could not adhere to the review commitments (Figure 1
The patient groups allocated to the two treatments under investigation were broadly similar in terms of potential confounding factors (Table 1
). The difference in mean age was the only variable that differed significantly (p
< 0.05) between groups. However, the patient’s age had no significant influence on the occurrence of early treatment failure, and neither did gender, tooth type, cavity class, the jaw the tooth was in, or the operator performing the treatment (p
> 0.1 for all pairwise tests).
The preoperative NRS-11 scores were also similar between groups, with a tendency of the teeth allocated to the 2.5% NaOCl group to cause more preoperative discomfort (Figure 2
). This difference, however, was not significant (p
= 0.1336). On days 3 and 7, the NRS scores became significantly lower in the NaOCl compared with the saline group (p
= 0.0010 day 3; p
= 0.0007 day 7; Figure 2
). Twelve patients from the saline group reported to the clinic and received root canal treatment due to unbearable pain from the treated tooth within the first 3 months. One of these patients returned on the first day after intervention, with further emergencies treated on days 12, 17, 19, 20, 28, 31, 42, 44 (two patients), 61, and 71. One patient from the NaOCl group presented with unbearable pain on day 17. This difference between groups was also highly significant (p
= 0.0008). All of the patients who came as emergencies reported spontaneous pain with an intensity of 7–9 on the NRS-11 scale.
The number of failed cases was not large enough to correlate the post-operative pain levels to early treatment failures; however, the one case that reported discomfort at level 5 on day 7 in the NaOCl group (Figure 2
) was the same case that appeared on day 17 for emergency root canal treatment. In the saline group, from the two patients who reported level-4 discomfort on day 7, one appeared as an early failure (day 20).
This is the first study to demonstrate a significant effect of the pulp lavage agent on patient-related treatment outcomes. Painful failures of dental procedures on vital teeth are an event that dentists want to avoid, because these emergencies can be hard to manage under local anesthesia [26
]. Moreover, painful experiences during or after dental treatments can induce dental anxiety in patients, which, in turn, makes them avoid dental treatments [27
]. Washing the dentin/pulp wound with a 2.5% NaOCl solution, which is a simple and inexpensive treatment step that any dentist can manage, significantly reduced both postoperative discomfort and early painful failures in comparison with a control treatment using an inert saline solution. We believe this finding to be both novel and clinically important, and therefore wish to publish these results as rapidly as possible, before the full one-year observation period including the non-painful failures was complete.
In general, pulp exposure should be avoided in asymptomatic cases, with consensus documents suggesting the removal of all deep caries and resulting pulp exposure to be overtreatment [1
]. In cases of extremely deep caries, pulp exposure is considered inevitable [3
], and for that reason, this cohort of patient were selected for possible inclusion in this study, as indirect pulp capping was not an option. Others may argue that after exposure it is good practice to remove at least a portion of the superficial pulp tissue in a partial or full pulpotomy, techniques which have been shown to yield good clinical results [4
]. However, as has been pointed out in recent reviews of the relevant literature, the existing data are heterogeneous and the treatment strategies are so varied that it prevents any conclusions as to which level of intervention is most appropriate to maintain pulp vitality and reduce patient pain [5
]. In the management of deep/extremely deep caries, each treatment option offers specific advantages and disadvantages, which need to be considered on an individual basis [29
]. The current results, however, strongly suggest that disinfection may be more important than the actual volume of pulp tissue removal in avoiding pain and preventing the early failure of the procedure.
It is theoretically possible that NaOCl application to the exposed pulp tissue resulted in the cytotoxicity of neurogenic sensors, which could account for the reduction in evident pain compared with saline lavage in this study. NaOCl exposure to vital tissue in vivo has been linked with neurological damage after extrusion from the root canal into the alveolar bone [30
]. Similarly, NaOCl has also been shown to be cytotoxic in vitro when in contact with dental pulpal cell populations, particularly in higher concentrations of 6% [31
], which is higher than the 2.5% employed in this study. Cytotoxicity was evident after several hours of incubation, and not within the 30 s contact time employed in this study.
Although this study followed a double-blind design, confounding by guessing the treatment solution by its smell cannot be unequivocally excluded. In future studies on this topic, the operators should wear respirators or take other extra measures to exclude bias from smelling the agent they apply. The randomization led to two fairly uniform groups (Table 1
). No factor other than the randomized treatment was associated with the outcomes under investigation. Although statistically significant, an age difference that occurred after the randomization process is unlikely to be clinically important, as several recent studies have not shown patients’ age to be a predictably significant factor in the success of pulp capping in mature teeth [32
]. A further potential issue with this study relates to pulp exposure and the later arrest of hemorrhage being achieved in every case allocated to the treatment. In any clinical trials, this is unusual, but can be explained by the large number of patients presenting with deep and extremely deep caries at the university clinic. Unfortunately, the prevalence of caries in India is high [34
], while there remains considerable value for patients in attending respected dental colleges. Close to ten thousand patients were screened at the department of Conservative Dentistry and Endodontics during the recruitment period for this study (13 months), which may explain how this well-defined group of cases could be identified in this relatively short period of time. Furthermore, patients with pain prior to treatment were excluded. Pain associated with deep caries is a predictor for advanced inflammation and irreversible pulpitis as defined histologically [13
]. Therefore, despite the fact that all the teeth under investigation had caries close to the pulp, they were asymptomatic and responded within normal limits to pulp sensibility testing. Therefore, they were likely to be no more than reversibly inflamed, which explains why the bleeding from the pulp space could be stopped with relative ease [35
The pain assessment tool used in this study is both validated and reliable [25
]. Although new online and other established pain intensity scales are available, including the visual analogue scale (VAS) or verbal rating scale (VRS), the NRS scale is considered a practical and reliable index with a good track record [36
], and is readily applicable to dentistry [37
]. The response rate regarding this outcome was 100% (discounting the one patient who appeared after one day as an emergency; Figure 1
). The result of immediate postoperative pain/discomfort reduction observed in this investigation was not expected, as we had hypothesized that NaOCl solutions can have inflammatory effects on vital tissues [19
]. On the other hand, on clean-cut pulp wounds, the type of material or medicament that is in contact with the wound surface may not exert a significant role in terms of postoperative pain [38
]. The finding that there was actually less postoperative pain when an NaOCl solution was used for wound lavage rather than saline would suggest that early painful events are likely to be due to infection rather than chemically induced inflammation, although we cannot speculate if the results would have been similar if a stronger NaOCl (e.g., 5%) had been used in this study.
For cases presenting with unbearable pain requiring root canal treatment (pulpectomy), an open approach was chosen, i.e., patients were not recalled at the 3-months interval. A 3-month recall visit would have missed the dynamic presentation of this early failure group, which by definition is unscheduled.
Overall, these results strongly support the use of a 2.5% NaOCl solution for wound lavage after carious exposures. Most recent studies on VPT used NaOCl solutions for this purpose, while older investigations did not [5
]. This trend was likely propagated by endodontic researchers clinically working with microscopes and knowing about the unique features of NaOCl in terms of necrotic tissue and biofilm dissolution [3
]. However, hitherto, the recommendation to use NaOCl solutions for the current purpose has not been substantiated by any data. Interestingly, dentin wound disinfectants used to be popular, especially in the form of a dentin washing solution containing benzalkonium chloride, a quaternary ammonium compound (Tubulicid, Dental Therapeutics, Nacka, Sweden). Whether such solutions are helpful in washing dentin/pulp wounds under carious exposures, however, remains to be investigated. NaOCl, which happens to be the core component of a product for chemical caries removal (Carisolv, MediTeam Dental, Göteborgsägen, Sweden), uniquely debrides necrotic soft tissues and biofilm. Furthermore, if followed by a rinse with an inert solution, it does not interfere with dentin bonding. To the contrary, by dissolving an organic material that may have been exposed in the acid environment of the carious lesions, it can improve the bond strengths and hence may just be the perfect agent for the current purpose [39
]. Nevertheless, future studies could compare different antimicrobial agents for the lavage of the dentin/pulp wound. Moreover, the ideal concentration of NaOCl solutions could be defined.