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Clinical Considerations for Pulp Pathology and Repair
Pulp stones (or denticles) are sometimes present in the pulp. These can be mineralized masses of dentin complete with dentinal tubules and odontoblastic processes (also known as true); in other cases, they are amorphous in structure (also known as false). They can be free or unattached to the outer pulpal wall or they can be attached to the dentin at the dentin-pulp interface. Pulp stones are formed during tooth development and also later as the pulp ages and they may be due to microtrauma. They are quite common and may fill most of the pulp chamber. They are detected as radiopaque masses in radiographs and may be a problem during endodontic therapy.
However, when the pulp is injured by cavity preparation through mechanical or chemical injury and even by extensive caries or other types of injury, it may undergo inflammation with pulpitis (pul-pahy- tis). This inflammation of pulpitis initially remains localized within the confines of the dentin. However, the pressure from this confined pulpitis can result in extreme pain as the inflammatory edema presses on the afferent nerves contained in the pulp (see earlier discussion). New studies also show that nicotine use by cutting vascularity also weakens the ability for the pulp to fight illness and disease; the risk of endodontic therapy is increased over 70%.
Knowing the exact anatomy of a tooth's pulp chamber using radiographs, especially the extension of the pulp horns into the overlying cusps, is important when practicing proper restorative dentistry. Research now shows that when a caries lesion encroaches pulp that is diagnosed as healthy or with reversible pulpitis, only the coronal portion of the pulpal tissue (immediately adjacent to the caries) has signs of inflammation but not the entire pulp tissue as was previously thought. Therefore, the clinician can treat the cari- ous exposed or indirect exposed pulp tissue with a pulp cap or pul- potomy-without the need for a pulpectomy (see discussion next). Calcium hydroxide has now been replaced with a bioceramic mate- rial for coverage of exposed or indirectly exposed pulpal tissue. A permanent restoration is then completed over the area to prevent any infection.
Irreversible pulpitis can later cause a pulpal infection in the form of a periapical abscess or cyst in the surrounding periodontium, spreading through the apical foramen or any accessory canal. This is an example of the communication between the pulp and the surround- ing periodontium, where disease states can extend between the tissue types, which ends up involving both. However, rarely does infection or other diseases of the periodontium involve the pulp.
If the pulp dies from the infection with irreversible pulpitis due to bacterial invasion of the pulp tissue, it must be surgically removed by a pulpectomy. An inert radiopaque rubbery material (gutta-per- cha) is then placed within the pulp chamber, including into the radicular pulp within each pulp canal during endodontic (or vital pulp) therapy. This is also referred to as "root canal treatment" by the patient.
When the pulp is removed by this treatment, the tooth is no longer vital because its nutritional source from the vascular pulpal tissue has been removed. Thus the endodontically treated tooth may darken and become brittle and break during mastication. The darkening is due to leftover degradative products from pulpal necrosis with the death of the pulp tissue that were passed along the dentinal tubules.
A permanent full-coverage restorative crown is placed on the treated natural crown to protect it from breaking and to prolong retention of the tooth as well as to improve its appearance if tooth colored. Internal or external nonvital whitening may also be necessary to reduce darkening with certain esthetic restorations or if coverage is deferred. If an abscess or cyst formation develops in the periodontium as a result of pulpitis, further surgery (apicoectomy) must be performed to remove the apical lesion.
Dental Professionals must try to prevent injury to the pulp during preventive procedures and restorative treatment. Such iatrogenic injury to the pulp can result from the heat or vibrations emitted by an older Dental professionals must try to prevent injury to the pulp during dental handpiece during cavity preparation as well as excessive coronal polishing, causing mechanical injury. The pulp can also undergo chemical injury by various restorative materials placed during cavity preparation (see earlier discussion). Newer water-cooled handpieces with rapid rotation, which minimize the heat and vibrations on the tooth as well as selective polishing techniques, are now used success- fully to reduce the incidence of pulpal damage.
Liners are also currently placed over dentin when using toxic chemical restorative materials to prevent future pulpal damage. Then cement bases are placed after the liner to protect the pulp from restorations that can serve as thermal conductors, such as gold inlays/crowns or silver amalgams. Tertiary types of dentin will also fill in around the sensitive pulp after the restoration has been placed within 6 months to a year, thereby reducing future pulpal pain.
The vitality of the dentin-pulp complex during health and after injury depends on pulpal tissue cell activity and the signaling processes that regulate the cell's behavior. This is especially true regarding the DPSCs present within the cell-rich zone of the pulp. Research has led to a better understanding of the molecular control of cellular behavior. Growth factors play a pivotal role in signaling the events of tissue formation and repair in the dentin-pulp complex.
Harnessing these growth factors can provide exciting opportunities for biologic approaches to dental tissue repair and the blueprint for replacement tissue engineering of the tooth. These approaches offer significant potential for improved clinical management of dental disease and maintenance of tooth vitality.
In addition, work is continuing directly with the DPSCs because this particular type of stem cell has the future potential to differentiate into a variety of other cell types that were originally derived from the embryonic mesenchyme, including muscle, bone, cartilage, and fat as well as dental tissue, such as dentin, cementum, PDL, and lamina pro- pria. This embryonic origin of DPSCs from neutral crest cells (NCCs) explains their multipotency.
The viable DPSCs are very simple to collect, without any mortality and morbidity. This is a noncontroversial topic since they can be col- lected without the involvement of any ethical issues. Being an autolo- gous transplant, they also do not possess any risk of immune reaction or tissue rejection and hence immunosuppressive therapy is not required. And they may also be useful for close relatives of the donor such as grandparents, parents and siblings. Apart from these considerations, banking is more economical when compared to cord blood and may be complementary to cord cell banking.
The DPSCs are most viable in primary teeth; permanent molars (such as thirds) also have the cells, though fewer. Processing has to be quick after removal and the freezing process is the same as used to store cord blood stem cells using cryopreservation. The dental pulp can be easily cryostored for long periods and it can be used to form a cryo- bank for adult tissue regeneration. The DPSCs retain their potential after cryopreservation; the cryopreservation of the whole dental pulp leads to a safe recovery.
Teeth that merely fall out may have damaged pulp and may not be a useful source, especially if viability standards are not set. Studies strongly support the use of telomere length and CD271 expression as viable markers of high proliferative capacity and multipotent DPSCs populations. Consequently, if such superior DPSC populations are to be fully exploited for regenerative medicine, studies must use these and other potential markers of DPSC proliferation and senescence.
In the latest research studies, the DPSCs have also shown great potential to be used in regenerative medicine for dental-related problems including the treatment of various human diseases, including brain, eye, heart, liver, bone, skin, and muscle diseases. Regenerative medicine is the emerging field of using stem cells to repair, replace, or enhance biologic function lost to injury, disease, congenital abnormalities, or aging.
In addition, identification of the genes controlling odontoblast differentiation might lead to development of methods enabling induction of tertiary dentin formation under carious lesions. Identification of the genes active during dentinogenesis might lead to recognition of regulatory factors, which would cause secondary dentinogenesis to proceed at the rate of primary dentinogenesis filling in any cavity formed, so that present-day restorations would become a thing of the past.
