Factors affecting the outcome of full pulpotomy in permanent posterior teeth diagnosed with reversible or irreversible pulpitis

Compared with endodontic therapy, partial or complete pulpotomy conform to the principle of minimal invasion by maximizing the preservation of the living pulp tissue to retain its strong sensory, defense, nutrition, and regeneration functions²⁴. A pulpotomy may substantially decrease the loss of tooth structure and the induced stresses caused by endodontic procedures, which would make the post-endodontically treated tooth more vulnerable to irreparable fracture²⁵. Without the need for complex endodontic procedures, a pulpotomy is a more time-efficient and operator-friendly treatment. Iatrogenic endodontic complications can also be decreased. Thus, pulpotomy has been recently introduced as an option for the management of permanent teeth with irreversible pulpitis^{11,12,13,14,15}. However, it is difficult to determine which cases are suitable for pulpotomy instead of endodontic treatment, and the factors affecting the clinical outcomes remain unclear.

In this study, 105 teeth with pulpitis caused by caries and severe tooth wear were treated by pulpotomy. The overall success rate was 90.8% at the 12-month review, demonstrating the feasibility of pulpotomy for the treatment of mature permanent teeth with symptomatic pulpitis. No statistically significant difference was found between cases with caries and those with severe tooth wear. However, age appears to have a significant impact on treatment outcomes. The success rates in group 1 (18–39 years), group 2 (40–59 years), and group 3 (≥ 60 years) were 100%, 85.7%, and 81.5% respectively, and Significant differences in success rate were found between groups 1 and 2 (P = 0.043), and groups 1 and 3 (P = 0.014). Though the small sample size of group 2 might make the statistic look significant between groups 1 and 2, the obvious statistical difference between groups 1 and 3 can also suggest that strict case selection should be considered for vital pulp therapy in older patients. It is critical to involve more cases in this study for assessing the significance of age.

The current treatment approaches for tooth hypersensitivity caused by severe tooth wear, such as topical application of desensitizing agents, adhesive applications, and laser irradiation, are often ineffective, or provide only short-term efficacy^26,27,28. In some cases of severe tooth wear with persisting hypersensitivity, root canal treatment is ultimately required²⁷. This study demonstrated that cases of severe tooth wear treated with pulpotomy were completely free of hypersensitivity after the treatment, suggesting that pulpotomy could be a unique solution to eliminate these symptoms. Severely worn teeth often have a narrow pulp chamber and a calcified root canal due to reparative dentin deposition in response to chronic stimuli resulting from dentin exposure²⁹, making root canal treatment more difficult. In this prospective cohort study, the clinical success rate of pulpotomy in cases of severe tooth wear reached 85.2%, with no radiographic abnormalities (Figs. 2, 3) such as canal obliteration or periapical rarefaction, making it comparable to conventional root canal treatment³⁰. Although the evidence gleaned from a 12-month review is insufficient, it provides preliminary proof of the practicability of treating severe tooth wear with pulpotomy. A further long-term randomized clinical trial comparing root canal treatment and pulpotomy in teeth with severe attrition and hypersensitivity should be conducted to provide more convincing evidence.

Both caries and tooth wear with pulpitis were included in this study. Vitality testing, periapical radiography, and more critically, clinical observation of the pulp tissue conditions under the microscope, were applied to confirm the vital status of the pulp tissue. Although the causes of caries and severe tooth wear are different, both can cause pulp tissue inflammatory response and subsequent infection and necrosis. Histological studies have shown that in the early stages of pulpitis, bacteria invade only the superficial layer of the pulp and then colonize the necrotic pulp. Once the pulp is infected by bacteria, it is considered irreversible pulpitis, which is incapable of self-healing²². However, the pulp tissue is equipped with innate and adaptive immune defense mechanisms that can confine the necrotic tissue and bacterial colonies by temporarily surrounding them with immune-inflammatory cells^22,31. If no treatment is rendered, the pulp infection will gradually spread to the entire pulp, causing complete necrosis of the pulp tissue. In theory, if the infected pulp is promptly removed, the rest of the pulp may remain healthy; this is the basis for successful pulpotomy treatment³¹. Therefore, precisely discerning the affected pulp tissue, and removing the infected portion, could greatly improve the success rate of pulpotomy.

This study reported the outcomes of pulpotomy on permanent teeth among different aged populations: group 1 (aged 18–39 years), group 2 (aged 40–59 years), and group 3 (aged above 60 years). Age was found to be a critical factor that affected the treatment outcomes for pulpotomy. Group 1 (18–39 years) had a significantly higher success rate than groups 2 and 3 (aged above 40 years). The results corroborate a recent study that demonstrated a significant difference in the success rate of direct pulp capping between adult patients aged under 40 years and those aged over 40 years¹⁹. Although some of the available studies deny the effect of age on the efficacy of pulpotomy¹⁶, others found that deciduous teeth and young permanent teeth have a very high success rate, suggesting that age may affect the outcome of pulpotomy in mature permanent teeth^32,33. In this study, the nine failed cases all occurred in patients aged over 40 years. The correlation between age and success rate could be attributed to the compromised reparative potential of aged pulp and its vulnerability to external insults⁹, resulting from the decreased proliferation and differentiation capacity of dental pulp stem cells, reduced root canal space, and reduced vasculature with aging³⁴. Interestingly, all the failed cases occurred within 12 months, and seven out of the nine failed cases occurred within 6 months. Elmsmari et al.³⁵ conducted a systematic review and concluded that partial pulpotomy is an adequate treatment option for permanent posterior teeth with carious exposures, and that 6 months can be considered a suitable period for evaluating success after a partial pulpotomy. Our finding that the majority of failed cases occurred within 6 months postoperatively supports the contention that 6 months is a critical time point for reviewing, although a long-term clinical and radiographic review at around 4 years postoperatively is essential as it is recommended for assessment of the success of root canal treatment^30,36.

Of the nine failed cases in patients aged over 40 years, one was diagnosed with apical periodontitis 6 months postoperatively (Fig. 6). Clinical examination found that the tooth had occlusal trauma, which suggested that in addition to the factor of age, the patient’s occlusal habits and trauma history during the follow-up period may have affected the treatment outcomes. Six early failure cases presented with pain on hot and cold stimulation, a certain degree of spontaneous pain, and nocturnal pain. In four cases the pain started at 2 weeks, and in two cases, at 2 months. As previously reported, errors in preoperative diagnosis and assessment of the pulp status are likely contributing factors³⁷. Another failed case presented with asymptomatic periapical periodontitis at a 1-year review, with no history of postoperative discomfort. One failed case with symptoms of acute pulpitis at the 12-month follow-up was caused by an operator error during the replacement of the crown restoration. However, long-term follow-up is still in progress, and the outcomes need to be further verified.

Some limitations should be acknowledged in this study. First, the inclusion criteria in this clinical study were comparatively conservative. According to Wolters ‘Endolight’ minimally invasive endodontic approach³⁸, severe pulpitis with exacerbated pain at night is an indication for pulpotomy; however, this condition was excluded from our study. This could partially explain our relatively high success rate. Second, with MTA as the capping material, tooth discoloration commonly occurs, although this was explained to the patient before the procedure. As it showed in Fig. 5, discoloration was obviously on the treated teeth during the 12-month visits. Studies have shown that the selection of pulp capping material plays a crucial role in the preservation of vital pulp. Commonly used pulp capping materials include calcium hydroxide, bioceramic MTA, and new nano bioceramic materials. MTA has been reported to be superior to calcium hydroxide as a pulpotomy medicament³⁹ because of its better biocompatibility, antibacterial properties, and edge sealing. MTA is difficult to handle, and has a long setting time, toxic elements in its composition, and the potential to cause tooth discoloration⁴⁰. Improved materials, such as Biodentine, iRoot BP, and NeoMTA, have been developed to overcome the drawbacks and have been applied in vital pulp therapy in mature permanent teeth^41,42. Additionally, this study only judged from a clinical point of view that aging is an important factor affecting the efficacy of pulpotomy. Further basic research at the cellular level needs to be conducted to confirm this conclusion. Finally, the follow-up time in this study was not sufficient, although further follow-ups are ongoing to closely monitor the progress of the treated teeth.