Pulp necrosis

The dental pulp is located in the centre of a tooth, made up of living connective tissue and cells. It is surrounded by a rigid, hard and dense layer of dentine The rise in pressure is commonly associated with an inflammatory exudate causing local collapse of the venous part of microcirculation. Tissues get starved of oxygen thus causing venules and lymphatics collapse which may lead to localized necrosis. A common clinical sign associated with the histopathology will be varying levels of suppuration and purulence. Following the spread of local inflammation, chemical mediators such as IL-8, IL-6 and IL-1 are released from necrotic tissues leading to further inflammation and odema, which advances to total necrosis of the pulp. Necrosis is a histological term that means death of the pulp. It does not occur suddenly unless there has been trauma. The pulp may be partially necrotic for some time. The area of cell death enlarges until the entire pulp is necrotic. Bacteria invade the pulp which causes the root canal system to become infected. Teeth that have total pulpal necrosis are usually asymptomatic except for those that have inflammation which has progressed to the periradicular tissues. == Aetiology and Causes ==

Pulp necrosis arises due to the cellular death within the pulp chamber – this can occur with or without the involvement of bacteria. Causes • Dental Caries • Dental Trauma • Dental Treatment • Pulpitis • Infection Dental Caries The influx of bacteria and growth of a carious lesion (if gross and left untreated) inevitably leads to the centre of the tooth – the pulp chamber. Once this tissue damaging process reaches the pulp it results in irreversible changes – necrosis and pulpal infection. Dental Trauma When a tooth is displaced from its normal position as a result of dental trauma, it can result in pulp necrosis due to the apical blood supply being compromised. This might be due to displacement of the tooth through avulsion or luxation. Furthermore, if the tooth is severely damaged, it could lead to inflammation of the apical periodontal ligament, and subsequently pulp necrosis. In irreversible pulpitis where the inflammation of pulpal tissues are not reversible, pulpal blood supply will become compromised and therefore necrosis of pulpal tissues will occur. == Signs and symptoms ==

Pulp necrosis may or may not arise with symptoms. Signs and symptoms of pulpal necrosis include; • Pain • Abscess and/or fistula • Internal root resorption • Increased tooth mobility There are additional signs of pulp necrosis which may be detected during radiographic assessment:-; • Untreated caries • Extensive/deep restoration • Previous pulp capping However, in some cases there may be no radiographic signs. For example, pulp necrosis caused by dental trauma which may only manifest/present itself with time, resulting in clinical changes. Teeth with said discolouration need to be treated with special care and further investigations are required before pulp necrosis can be diagnosed. Abscess and/or fistula Alterations in the gingiva such as fistulas or abscesses and radiographic signs such as periapical lesions and external root resorption are used in some studies to diagnose pulp necrosis however other studies state that these factors alone are not enough to diagnose a necrotic pulp. Internal root resorption Internal root resorption may be an indication of pulpal necrosis though it is not possible to diagnose accurately with radiographic presentation of this alone. This is because the pulp tissue apical to the resorptive lesion will still be vital to allow active resorption to take place, it provides the clastic cells with nutrients via a viable blood supply. == Diagnosis ==

There are a plethora of ways to diagnose pulp necrosis in a tooth. The diagnosis of pulp necrosis can be based on the following observations: negative vitality, a periapical radiolucency, a grey tooth discoloration and even peri-apical lesions. This altered translucency in the tooth is due to disruption and cutting off of the apical neurovascular blood supply. Thermal Tests Thermal testing is a common and traditional way used to detect pulp necrosis. These tests can exist in the form of a cold or hot test, which aims to stimulate nerves in the pulp by the flow of dentine liquid at changes in temperature. The liquid flow leads to movement of the odontoblast processes and mechanical stimulation of pulpal nerves. The cold test can be done by soaking a cotton pellet into 1,1,1,2 tetrofluoroethane, also known as Endo ice refrigerant spray. The cotton pellet will then be placed onto the middle third of the intact tooth surface. The clinical study done by Gopikrishna indicated the tooth to be diagnosed as having necrotic pulp if subjects felt no sensation after two 15-second applications every two minutes. It is worthy to note that a control test should be performed on the adjacent tooth to ensure further accuracy of results. Pulse Oximeter Test The pulse oximeter test is a more accurate way to test for necrotic pulps as it primarily tests for vascular health of the pulp as compared to its nervous response. This method involves taking measurements of blood oxygen saturation levels, making it non-invasive and an objective way to record patient response regarding pulpal diagnosis. For the purposes of evaluating pulp vitality, it is imperative that the probes fit the anatomical contours and shape of the measured teeth. A study was done to assess the accuracy of pulse oximetry in comparison to thermal and electrical tests. Customized pulse oximeter dental probes were placed on the crown of the tooth, with oxygen saturation values recorded after 30 seconds of monitoring each tooth. The values were taken as a positive response (i.e. vital pulp) within the range of 75-85% oxygen saturation and a negative response below 75%, indicating pulp necrosis. also suggests that a pulse oximeter is more accurate than cold testing in diagnosing pulp necrosis, however comments raised regarding the validity of the evidence stated that the pulse oximeter adaptors were built by the respective authors causing some degree of bias in the experiments. == Management & Treatment ==

The most basic treatment for teeth with pulpal necrosis is root canal treatment. This involves the use of biologically accepted mechanical and chemical treatment of the root system, followed by the placement of a root filling, allowing healing of the periradicular tissues to occur. Pulpal regeneration can be considered if the following criteria are met: • Incomplete root development and incomplete apex closure • Apexogenesis is not applicable as there is apical closure Pulpal regeneration involves the removal of the necrotic pulp followed by the placement of medicament into the root canal system until it is non-symptomatic. Apical bleeding is then induced to create a clot at the apex which will be sealed by Mineral Trioxide Aggregate. In an immature permanent tooth pulpal necrosis causes the development of the root to stop. This causes the walls of the root to become fragile and thin which can make these teeth more prone to cervical root fracture and ultimately the tooth may be lost. These teeth in the past were treated with the calcium hydroxide apexification technique. A disadvantage of this was that it required multiple visits over a prolonged time and there could be an increased risk of cervical root fracture due to an increase in exposure to calcium hydroxide. The apical barrier technique with mineral trioxide aggregate was then used. The advantage of this technique over apexification was that it shortened the number of appointments and the healing outcomes were better. A disadvantage of both these techniques was that it did not allow the root to mature and so regenerative endodontic procedures (REPs) were utilised. A systematic review conducted by Kahler, et al. (2017) showed similar clinical outcomes for teeth treated with REPs versus calcium hydroxide apexification/MTA apical barrier technique. They suggested that it should be considered as a first line treatment option in immature teeth with pulpal necrosis. They did state that a thorough discussion with the patient would be necessary as teeth treated with REP's can show variable root maturation and adverse outcomes. == References ==