Vital pulp therapy: the past, present and future

Our understanding of pulp histopathology

Early studies demonstrated a poor correlation between clinical symptoms and the histological status of the pulp.^32–34 It was believed that clinical symptoms can only determine the probable state of the pulp.³⁴ Ricucci et al showed that clinical diagnosis matched the histological diagnosis in 96.6% of cases when the histological diagnosis was normal pulp/reversible pulpitis, and in 84.4% of irreversible pulpitis histological diagnoses.³⁵ This study not only showed a ‘good’ correlation between clinical and histological diagnosis, but it also demonstrated that dentists are more likely to make the wrong diagnosis when the clinical situation suggests irreversible pulpitis than when signs and symptoms are indicative of normal pulp/reversible pulpitis. Therefore, dentists are more likely to unnecessarily perform an RCT when the pulp is savable than to opt for VPT when the pulp is unsavable, when relying on the clinical signs and symptoms to determine their treatment. Furthermore, this study demonstrated that pulp pathology occurs in compartments and can vary in severity and stage according to the corono-apical level. Following carious pulp exposure, the most coronal pulp undergoes coagulation and liquefactive necrosis and is colonized by heavy bacterial infection, forming a micro-abscess.³⁵ The extent of the micro-abscess depends on several factors, such as rate of caries progression and time of detection following pulp exposure. If detected early, and the pulp is only partially necrotic, the pulp surrounding the micro-abscess exhibits accumulation of polymorphonuclear leukocytes, macrophages and lymphocytes. Further peripherally, the inflammatory reaction tapers off, and normal pulp tissue can be encountered in the same tooth.³⁵ This means that if the layers of necrotic/infected and severely inflamed pulp could be removed and covered with a biomaterial that allows healing, the remaining pulp can remain healthy and functional. This was supported later by clinical studies that demonstrated high success rates for VPT even in the presence of clinical signs and symptoms suggestive of irreversible pulpitis.^13,29,30

The introduction of calcium silicates

For many years, the gold standard material for pulp capping was calcium hydroxide.³⁶ However, calcium hydroxide does degrade over time³⁷ and it provides a poor seal because it has no inherent adhesive properties.³⁸ Moreover, calcific bridges (tertiary dentine) that form following calcium hydroxide capping were shown to exhibit multiple tunnel defects.^39,40 These could potentially provide pathways for bacterial microleakage, resulting in inflammatory changes in the pulp.³⁹ This was reflected in clinical studies, which showed discouraging outcomes that tended to decline over time when calcium hydroxide was used as the capping material.^21,23

Calcium silicates have been used to cap pulps exposed mechanically or cariously.⁴¹ Calcium silicates are bioactive materials that stimulate mineralization and cell differentiation.⁴² They were shown to have excellent sealing ability and their solubility is minimal.⁴² They upregulate angiogenesis by releasing dentine matrix components.⁴³ The use of MTA as the capping material results in a milder inflammatory reaction, less hyperaemia and necrosis, and the formation of a thicker reparative dentine bridge compared with calcium hydroxide.⁴⁴ Recent studies have shown a high success rate for VPT performed using calcium silicates as the capping material.^30,45–48

Simplifying VPT

Partial pulpotomy seems to be the most technically demanding procedure among the range of VPT procedures. The aim is to excise the irreversibly damaged coronal pulp and dress the remaining ‘healthy’ pulp with a biomaterial that promotes pulpal healing. However, it is not easy to determine how much pulp should be excised. The current recommendation is to remove the obviously diseased pulp material (necrotic and or severely inflamed) and to observe the marginal dentine and the excised pulp (under magnification) for its vascularity, presence of yellowish liquefaction, and time needed to achieve haemostasis.^8,31 Furthermore, the wound surface area that is created during partial pulpotomy is significantly larger than that created during direct pulp capping or full pulpotomy (at least in molar teeth). Thus, haemostasis can be more challenging and more post-operative pain can be anticipated. It is entirely plausible to suggest that bigger wounds may take longer to heal with more possibility for error and contamination.

A full coronal pulpotomy procedure achieves the same objectives of partial pulpotomy, namely preserving the radicular vital pulp, allowing complete root development (in the immature tooth) and avoiding an unnecessary and potentially difficult RCT while there is a similar success rate to partial pulpotomy.^13,30 It has the advantage of being easier to perform and teach, has a better chance of removing the damaged pulp, and results in a smaller wound surface area. Furthermore, it can be performed without the need for magnification, which is often missing in the primary dental care setting. The obvious disadvantage of full pulpotomy could be the loss of sensation to thermal stimulation, although this is not absolute.

Therefore, to simplify VPT, the authors suggest dividing the exposed inflamed pulps into three categories:

The term ‘asymptomatic irreversible pulpitis’ should be reconsidered

The term asymptomatic irreversible pulpitis was adopted by the American Association of Endodontists (AAE) and the American Board of Endodontics in 2008.²⁶ It is described as ‘a clinical diagnosis based on subjective and objective findings indicating that the vital inflamed pulp is incapable of healing, and that root canal treatment is indicated. These cases have no clinical symptoms and usually respond normally to thermal testing, but may have had trauma or deep caries that would be likely result in exposure following removal’.²⁶ While histological studies have shown that the pulp can be irreversibly inflamed without exhibiting any symptoms, there are two main concerns with this definition:

This term was revised in 2020 in the AAE's 10th edition of the ‘Glossary of Endodontic Terms’.⁵⁰ Asymptomatic irreversible pulpitis was defined as: ‘A clinical diagnosis based on subjective and objective findings indicating that the vital inflamed pulp is incapable of healing. Additional descriptors: no clinical symptoms but inflammation produced by caries, caries excavation, trauma’. Recently, the AAE published a position statement on vital pulp therapy that stated that a ‘pretreatment diagnosis of irreversible pulpitis is not necessarily an indication for pulpectomy, as more conservative treatment could be considered’.⁵¹ While the revised definition removed the advice that root canal treatment is indicated when a diagnosis of asymptomatic irreversible pulpitis is made, it still states that the inflamed pulp is incapable of healing. Therefore, the term asymptomatic irreversible pulpitis may still be confusing and may result in overprescription of pulpectomy and RCT. The authors suggest reconsidering both the definition and treatment recommendations for this disease category.

Rubber dam isolation during deep caries management should become mandatory

Recent guidelines and reference to the literature related to managing deep caries, including handling of vital pulp tissue is essential. Rubber dam remains the gold standard isolation technique and, in addition to many other benefits, provides a surgically clean field and aseptic environment for the restorative/endodontic procedure. However, less than 20% of UK dentists frequently use rubber dam in endodontic therapy⁵² and only 29.2% of primary care dental professionals within the UK used rubber dam for deep caries management.⁵³ Ireland discussed the use of rubber dam as early as 1962, stating, ‘probably no other technique, treatment or instrument used in dentistry is so universally accepted and advocated by the recognized authorities, and so universally ignored by practising dentists’.⁵⁴ Rubber dam isolation during deep caries excavation should become mandatory because the lack of an aseptic environment may preclude the use of VPT techniques.⁵⁵ Additionally, when removing coronal pulp tissue, a new sterile bur using sterile saline as an irrigant/coolant would be advisable to minimize any additional infection risk.