Root canal

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Root canal
Human tooth diagram-en.svg
Details
Identifiers
Latin canalis radicis dentis
MeSH D014092
TA98 A05.1.03.049
TA2 932
FMA 55674
Anatomical terminology

A root canal is the naturally occurring anatomic space within the root of a tooth. It consists of the pulp chamber (within the coronal part of the tooth), the main canal(s), and more intricate anatomical branches that may connect the root canals to each other or to the surface of the root.

Contents

Structure

At the center of every tooth is a hollow area that houses soft tissues, such as the nerve, blood vessels, and connective tissue. This hollow area contains a relatively wide space in the coronal portion of the tooth called the pulp chamber. These canals run through the center of the roots, similar to the way graphite runs through a pencil. The pulp receives nutrition through the blood vessels, and sensory nerves carry signals back to the brain. A tooth can be relieved from pain if there is irreversible damage to the pulp, via root canal treatment.

Root canal anatomy consists of the pulp chamber and root canals. Both contain the dental pulp. The smaller branches, referred to as accessory canals, are most frequently found near the root end (apex), but may be encountered anywhere along the root length. The total number of root canals per tooth depends on the number of the tooth roots ranging from one to four, five or more in some cases. Sometimes there are more than one root canal per root. Some teeth have a more variable internal anatomy than others.

An unusual root canal shape, complex branching (especially the existence of horizontal branches), and multiple root canals are considered as the main causes of root canal treatment failures. (e.g. If a secondary root canal goes unnoticed by the dentist and is not cleaned and sealed, it will remain infected, causing the root canal therapy to fail).

Root canal system

The specific features and complexity of the internal anatomy of the teeth have been thoroughly studied. Using a replica technique on thousands of teeth, Walter Hess made clear as early as 1917 that the internal space of dental roots is often a complex system composed of a central area (root canals with round, oval or irregular cross-sectional shape) and lateral parts (fins, anastomoses and accessory canals). In fact, this lateral component may represent a relatively large volume, which challenges the cleaning phase of the instrumentation procedure in that tissue remnants of the vital or necrotic pulp as well as infectious elements are not easily removed in these areas. Thus, the image of root canals having a smooth, conical shape is generally too idealistic and underestimates the reach of root canal instrumentation.

Contents

Procedures for root canal Root Canal Illustration Molar.svg
Procedures for root canal

The space inside the root canals is filled with a highly vascularized, loose connective tissue, called dental pulp . The dental pulp is the tissue of which the dentin portion of the tooth is composed. The dental pulp helps complete formation of the secondary teeth (adult teeth) one to two years after eruption into the mouth. The dental pulp also nourishes and hydrates the tooth structure, making the tooth more resilient, less brittle and less prone to fracture from chewing hard foods. Additionally, the dental pulp provides a hot and cold sensory function.

Variation

Root canal pulp removed, cleaned and made ready for filling and placing a crown Root Canal Edited.png
Root canal pulp removed, cleaned and made ready for filling and placing a crown

Root canals presenting an oval cross-section are found in 50–70% of root canals. In addition, canals with a "tear-shaped" cross section are common when a single root contains two canals (as occurs, for example, with the additional mesial root seen with the lower molars), subtleties that can be more difficult to appreciate on classical radiographs.

Recent studies have shown that use of cone-down CT scans can detect accessory canals that would have been missed in 23% of cases, which can in turn lead to apical periodontitis. The upper molars, in particular, are predisposed to have an occult accessory canal in nearly half of patients. [1]

Clinical significance

Root canal is also a colloquial term for a dental operation, endodontic therapy, wherein the pulp is cleaned out, the space disinfected and then filled.

When rotary nickel titanium (NiTi) files are used in canals with flat-oval or tear-shaped cross sections, a circular bore is created due to the rotational action of the metal. Also, small cavities within the canal such as the buccal or lingual recesses may not be instrumented within the tooth, potentially leaving residual disease during disinfection.

Tissue or biofilm remnants along such un-instrumented recesses may lead to failure due to both inadequate disinfection and the inability to properly obturate the root-canal space. Consequently, the biofilm should be removed with a disinfectant, commonly sodium hypochlorite, during root canal treatment.

See also

Related Research Articles

<span class="mw-page-title-main">Human tooth</span> Calcified whitish structure in humans mouths used to break down food

Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla or the mandible and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.

<span class="mw-page-title-main">Endodontics</span> Field of dentistry

Endodontics is the dental specialty concerned with the study and treatment of the dental pulp.

<span class="mw-page-title-main">Toothache</span> Medical condition of the teeth

Toothache, also known as dental pain or tooth pain, is pain in the teeth or their supporting structures, caused by dental diseases or pain referred to the teeth by non-dental diseases. When severe it may impact sleep, eating, and other daily activities.

<span class="mw-page-title-main">Pulp (tooth)</span> 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.

A pulp polyp, also known as chronic hyperplastic pulpitis, is a "productive" inflammation of dental pulp in which the development of granulation tissue is seen in response to persistent, low-grade mechanical irritation and bacterial invasion of the pulp.

<span class="mw-page-title-main">Dentin dysplasia</span> Medical condition

Dentin dysplasia (DD) is a rare genetic developmental disorder affecting dentine production of the teeth, commonly exhibiting an autosomal dominant inheritance that causes malformation of the root. It affects both primary and permanent dentitions in approximately 1 in every 100,000 patients. It is characterized by the presence of normal enamel but atypical dentin with abnormal pulpal morphology. Witkop in 1972 classified DD into two types which are Type I (DD-1) is the radicular type, and type II (DD-2) is the coronal type. DD-1 has been further divided into 4 different subtypes (DD-1a,1b,1c,1d) based on the radiographic features.

A post and core crown is a type of dental restoration required where there is an inadequate amount of sound tooth tissue remaining to retain a conventional crown. A post is cemented into a prepared root canal, which retains a core restoration, which retains the final crown.

<span class="mw-page-title-main">Scaling and root planing</span> Dental procedure

Scaling and root planing, also known as conventional periodontal therapy, non-surgical periodontal therapy or deep cleaning, is a procedure involving removal of dental plaque and calculus and then smoothing, or planing, of the (exposed) surfaces of the roots, removing cementum or dentine that is impregnated with calculus, toxins, or microorganisms, the agents that cause inflammation. It is a part of non-surgical periodontal therapy. This helps to establish a periodontium that is in remission of periodontal disease. Periodontal scalers and periodontal curettes are some of the tools involved.

<span class="mw-page-title-main">Root canal treatment</span> Dental treatment

Root canal treatment is a treatment sequence for the infected pulp of a tooth which is intended to result in the elimination of infection and the protection of the decontaminated tooth from future microbial invasion. Root canals, and their associated pulp chamber, are the physical hollows within a tooth that are naturally inhabited by nerve tissue, blood vessels and other cellular entities. Together, these items constitute the dental pulp.

Apical periodontitis is typically the body's defense response to the threat of microbial invasion from the root canal. Primary among the members of the host defense mechanism is the polymorphonuclear leukocyte, otherwise known as the neutrophil. The task of the neutrophil is to locate and destroy microbes that intrude into the body – anywhere in the body – and they represent the hallmark of acute inflammation.

<span class="mw-page-title-main">Pulpotomy</span>

Pulpotomy is a minimally invasive procedure performed in children on a primary tooth with extensive caries but without evidence of root pathology. The minimally invasive endodontic techniques of vital pulp therapy (VPT) are based on improved understanding of the capacity of pulp (nerve) tissues to heal and regenerate plus the availability of advanced endodontic materials. During the caries removal, this results in a carious or mechanical pulp exposure (bleeding) from the cavity. During pulpotomy, the inflamed/diseased pulp tissue is removed from the coronal pulp chamber of the tooth leaving healthy pulp tissue which is dressed with a long-term clinically successful medicament that maintains the survival of the pulp and promotes repair. There are various types of medicament placed above the vital pulp such as Buckley's Solution of formocresol, ferric sulfate, calcium hydroxide or mineral trioxide aggregate (MTA). MTA is a more recent material used for pulpotomies with a high rate of success, better than formocresol or ferric sulfate. It is also recommended to be the preferred pulpotomy agent in the future. After the coronal pulp chamber is filled, the tooth is restored with a filling material that seals the tooth from microleakage, such as a stainless steel crown which is the most effective long-term restoration. However, if there is sufficient remaining supporting tooth structure, other filling materials such as amalgam or composite resin can provide a functional alternative when the primary tooth has a life span of two years or less. The medium- to long-term treatment outcomes of pulpotomy in symptomatic permanent teeth with caries, especially in young people, indicate that pulpotomy can be a potential alternative to root canal therapy (RCT).

Combined periodontic-endodontic lesions are localized, circumscribed areas of bacterial infection originating from either dental pulp, periodontal tissues surrounding the involved tooth or teeth or both.

<span class="mw-page-title-main">Apical foramen</span> Opening in the tip of the root of a tooth

In dental anatomy, the apical foramen, literally translated "small opening of the apex," is the tooth's natural opening, found at the root's very tip—that is, the root's apex—whereby an artery, vein, and nerve enter the tooth and commingle with the tooth's internal soft tissue, called pulp. Additionally, the apical foramen is the point where the pulp meets the periodontal tissues, the connective tissues that surround and support the tooth. The foreman is located 0.5mm to 1.5mm from the apex of the tooth. Each tooth has an apical foreman.

Pulp necrosis is a clinical diagnostic category indicating the death of cells and tissues in the pulp chamber of a tooth with or without bacterial invasion. It is often the result of many cases of dental trauma, caries and irreversible pulpitis.

In dentistry, the smear layer is a layer found on root canal walls after root canal instrumentation. It consists of microcrystalline and organic particle debris. It was first described in 1975 and research has been performed since then to evaluate its importance in bacteria penetration into the dentinal tubules and its effects on endodontic treatment. More broadly, it is the organic layer found over all hard tooth surfaces.

<span class="mw-page-title-main">Pulp stone</span>

Pulp stones are nodular, calcified masses appearing in either or both the coronal and root portion of the pulp organ in teeth. Pulp stones are not painful unless they impinge on nerves.

<span class="mw-page-title-main">Regenerative endodontics</span> Dental specialty

Regenerative endodontic procedures is defined as biologically based procedures designed to replace damaged structures such as dentin, root structures, and cells of the pulp-dentin complex. This new treatment modality aims to promote normal function of the pulp. It has become an alternative to heal apical periodontitis. Regenerative endodontics is the extension of root canal therapy. Conventional root canal therapy cleans and fills the pulp chamber with biologically inert material after destruction of the pulp due to dental caries, congenital deformity or trauma. Regenerative endodontics instead seeks to replace live tissue in the pulp chamber. The ultimate goal of regenerative endodontic procedures is to regenerate the tissues and the normal function of the dentin-pulp complex.

An Endodontic crown or endocrown is a single prostheses fabricated from reinforced ceramics, indicated for endodontically treated molar teeth that have significant loss of coronal structure. Endocrowns are formed from a monoblock containing the coronal portion invaded in the apical projection that fills the pulp chamber space, and possibly the root canal entrances; they have the advantage of removing lower amounts of sound tissue compared to other techniques, and with much lower chair time needed. They are luted to the tooth structure by an adhesive material. The ceramic can be milled using computer-aided techniques or molded under pressure. Endocrowns can be an alternative to conventional crown restorations.

In the dental specialty of endodontics, periradicular surgery is surgery to the external root surface. Examples of periradicular surgery include apicoectomy, root resection, repair of root perforation or resorption defects, removal of broken fragments of the tooth or a filling material, and exploratory surgery to look for root fractures.

Periapical granuloma, also sometimes referred to as a radicular granuloma or apical granuloma, is an inflammation at the tip of a dead (nonvital) tooth. It is a lesion or mass that typically starts out as an epithelial lined cyst, and undergoes an inward curvature that results in inflammation of granulation tissue at the root tips of a dead tooth. This is usually due to dental caries or a bacterial infection of the dental pulp. Periapical granuloma is an infrequent disorder that has an occurrence rate between 9.3 to 87.1 percent. Periapical granuloma is not a true granuloma due to the fact that it does not contain granulomatous inflammation; however, periapical granuloma is a common term used.

References

  1. Karabucak, B; Bunes, A; Chehoud, C; Kohli, MR; Setzer, F (February 10, 2016). "Prevalence of Apical Periodontitis in Endodontically Treated Premolars and Molars with Untreated Canal: A Cone-beam Computed Tomography Study". Journal of Endodontics. 42 (4): 538–41. doi:10.1016/j.joen.2015.12.026. PMID   26873567.