Дентин и пульпа зуба: строение и функции.

Part in the center of a tooth made up of living connective tissue and cells called odontoblasts

The pulp is the connective tissue, nerves, blood vessels, and odontoblasts that comprise the innermost layer of a tooth. The pulp's activity and signalling processes regulate its behaviour.

The pulp is the neurovascular bundle central to each tooth, permanent or primary. It is composed of a central pulp chamber, pulp horns, and radicular canals. The large mass of the pulp is contained within the pulp chamber, which is contained in and mimics the overall shape of the crown of the tooth. Because of the continuous deposition of the dentine, the pulp chamber becomes smaller with the age. This is not uniform throughout the coronal pulp but progresses faster on the floor than on the roof or sidewalls. Radicular pulp canals extend down from the cervical region of the crown to the root apex. They are not always straight but vary in shape, size, and number. They are continuous with the periapical tissues through the apical foramen or foramina. The total volume of all the permanent teeth organs is 0.38cc, and the mean volume of a single adult human pulp is 0.02cc. Accessory canals are pathways from the radicular pulp. These canals, which extend laterally through the dentin to the periodontal tissue, are seen especially in the apical third of the root. Accessory canals are also called lateral canals because they are usually located on the lateral surface of the roots of the teeth.

The plexus of Raschkow monitors painful sensations. By virtue of their peptide content, they also play important functions in inflammatory events and subsequent tissue repair. There are two types of nerve fibers that mediate the sensation of pain: A Fibres conduct rapid and sharp pain sensations and belong to the myelinated group, whereas C Fibres are involved in dull aching pain and are thinner and unmyelinated. The A Fibres, mainly of the A delta type, are preferentially located in the periphery of the pulp, where they are in close association with the odontoblasts and extend fibers to many but not all dentinal tubules. The C Fibres typically terminate in the pulp tissue proper, either as free nerve endings or as branches around blood vessels. Sensory nerve fibers that originate from inferior and superior alveolar nerves innervate the odontoblastic layer of the pulp cavity. These nerves enter the tooth through the apical foramen as myelinated nerve bundles. They branch to form the subodontoblastic nerve plexus of Raschkow, which is separated from the odontoblasts by a cell free zone of Weil. This plexus lies between the cell free and cell rich zones of the pulp.

As the dental pulp is a highly vascularised and innervated region of the tooth, it is the site of origin for most pain related sensations. The dental pulp nerve is innervated by one of the trigeminal nerves, otherwise known as the fifth cranial nerve. The neurons enter the pulp cavity through the apical foramen and branch off to form the nerve plexus of Raschkow. Nerves from the plexus of Raschkow provide branches to form a marginal plexus around the odontoblasts, with some nerves penetrating the dentinal tubules. The dental pulp is also innervated by the sympathetic division of the autonomic nervous system. Have a relatively low threshold sensory apparatus. Mainly located at the pulp dentine border at the top of the pulp, and more specifically concentrated in the pulp horn. This is known as the hydrodynamic theory. Stimuli that displaces the fluid within the dentinal tubules will trigger the intradental myelinated A Fibres, leading to the sharp pain sensation
They are heavily influenced by modulating interneurons before they reach the thalamus. C Fibre stimulation often results in a "slow pain", normally characterised as a dull and aching pain. The pulp swells when the protective layers of enamel and dentine are compromised. Unlike irreversible pulpitis, the pulp gives a regular response to sensibility tests and inflammation resolves with management of the cause. No significant radiographic changes are present in the periapical region. Further examination is required to ensure that the dental pulp has returned to its normal state.

Pulp necrosis is when the pulp has died/dying. Causes include untreated caries, trauma or bacterial infection. It is often subsequent to chronic pulpitis. Teeth with pulp necrosis undergo a root canal or extraction to prevent further spread of the infection, which may lead to an abscess.

Necrosis may be symptomatic or asymptomatic. Symptomatic necrosis involves lingering pain response to hot and cold stimuli, spontaneous pain that may cause a patient to awaken during sleep, difficulty eating and sensitivity to percussion. Asymptomatic necrosis is non responsive to thermal stimuli or electric pulp tests, leaving the patient unaware of the pathology. Sequelae of a necrotic pulp include acute apical periodontitis, dental abscess, or radicular cyst and tooth discolouration.

Untreated necrotic pulp may result in further complications, such as infection, fever, swelling, abscesses and bone loss. Two treatment options are available for pulpal necrosis.