Pulpitis is mainly caused by bacterial infection which itself is a secondary development of caries (tooth decay).
Pulpitis may be caused by bacteria from dental caries that penetrate through the enamel and dentin to reach the pulp, or it may be mechanical, a result of trauma, such as physical damage to the tooth.
Inflammation is commonly associated with a bacterial infection but can also be due to other insults such as repetitive trauma or in rare cases periodontitis.
[6] In the case of penetrating decay, the pulp chamber is no longer sealed off from the environment of the oral cavity.
Unlike other parts of the body where pressure can dissipate through the surrounding soft tissues, the pulp cavity is very different.
It is surrounded by dentin, a hard tissue that does not allow for pressure dissipation, so increased blood flow, a hallmark of inflammation, will cause pain.
The pulp cavity inherently provides the body with an immune system response challenge, which makes it very difficult for a bacterial infection to be eliminated.
[11] If the teeth are denervated, this can lead to irreversible pulpitis, depending on the area, rate of infection, and length of injury.
This is why people who have lost their dental innervation have a reduced healing ability and increased rate of tooth injury.
The inflammation may be acute or chronic because just like other tissues in the body, the pulp will react to irritants with innate and/or adaptive immune responses.
[13][14] Innate immunity in the pulp is not specific but uses receptors to recognize molecular patterns common to microbes to initiate bacterial killing (phagocytosis).
Although the first two items are not classic components of innate immunity, they are uniquely involved in the initial inflammatory response to caries.
[16] According to the Brännström's hydrodynamic theory, activated nociceptors from fluid movement and other irritants through the patent dentine tubules result in pulp pain.
The inflammatory mediators act on specific receptors relating to nociceptive neurons, leading to the production of second messengers and activation of phospholipases and protein kinases.
The ion channels open based on pain stimuli propagating action potentials in sensory neurons.
Changes in sodium channel (NaCH) expression occur after inflammatory lesions, which may generate different pain states seen when neuronal fibers are activated.
As a result, an increased co-expression of multiple isoforms at demyelinating nodal sites in painful dental pulp.
This isoforms of sodium channels may be a main factor in pain sensations due to their production of axonal excitability properties.
[21] Neuropeptides are increasingly being researched for having a role in molecular mechanisms involved with pain, including ion channels and inflammation.
Substance P (SP) is a neuropeptide produced by capsaicin neuron cell bodies (localized in trigeminal ganglia and dorsal root) and plays a major role in dental pain and inflammation.
[18] Based on the tooth injury, sensory nerve fibers react to pulpitis by growing terminal branches into the adjacent surviving pulp, which also changes the cytochemical phenotype.
Pulp testing is combined with information taken from history, examination and other special investigations such as radiographs in order to reach a diagnosis.
The probe tip of the test device is placed directly onto the tooth surface and an electrical stimulus is produced.
This stimulus causes an ionic change across the neural membrane, inducing an action potential in the myelinated nerves.
This threshold level varies between patients, and is affected by factors such as age, pain perception, tooth surface conduction and resistance.
[18][22] Possible explanations for false-positives include: Studies have indicated that there is little correlation between histopathological status of the pulp and clinical information.
Symptoms include transient pain or sensitivity resulting from many stimuli, notably hot, cold, sweet,[23] water and touch.
This means that once the irritant is eliminated, usually by removal of decay and the placement of a restoration, that the pulp will return to its normal, healthy state.
[23] Today electronic pulp testers are rarely used for diagnosis of the reversibility of pulpitis due to their unreliable nature.
[citation needed] The tooth may be endodontically treated whereby the pulp is removed and replaced by gutta percha.