Lecture one -----------------------------------------------------------------د.احمد غانم
Endodontics may be simply defined as the branch of dental science concerned with the study of anatomy, physiology, pathology, and treatment of the dental pulp and periradicular region. Endodontic treatment includes any procedure designed to maintain the health of all, or part of, the pulp. When the pulp is diseased or injured, treatment is aimed at maintaining or restoring the health of the periradicular tissues, usually by root canal treatment, but occasionally in combination with endodontic surgery.
The principle of endodontics is to clean, shape and fill the root canal system. We also can add the principle of doing a root canal in such a fashion that we can restore the tooth and reestablish the occlusion. It is not particularly beneficial if we do a root canal yet destroy the tooth in the process. It is absolutely crucial for the success of the root canal that we be able to restore the tooth and prevent microleakage
If these are the principles to endodontics, the four keys to endodontics are:
Diagnosis is certainly the most difficult aspect of endodontics,
Access is certainly the key to successful clinical endodontics.
Shaping of the canal is done by either hand or engine-driven instruments.
Cleaning is done by irrigating the canal system with one of a number of solutions that may be antibacterial and have tissue-dissolving ability.
Obturation is achieved with gutta-percha and a root canal sealer.
The cleaning and shaping phase of endodontic treatment is regarded as the most important. When the canal is clean, it is important that the system is not recontaminated by microorganisms. Because of the complex anatomy of the root canal system, complete disinfection is almost impossible to achieve. It is important, therefore, that any remaining microorganisms in the dentinal tubules are prevented from multiplying by the use of an antimicrobial dressing followed by three-dimensional filling. Recontamination from the oral cavity must be avoided, and the importance of a good coronal seal cannot be overestimated.
The tooth remains very much alive after endodontic therapy, because its living root surfaces are nourished by the adjacent tissues of the gums and jaw. Only the interior of the tooth loses living tissue with root canal treatment.
Saving a tooth this way is better for your health than extraction, and is less costly than replacing the missing tooth.
Is Endodontic Treatment Effective?
YES!!! Routine endodontic therapy is among the most effective procedures in modern dental or medical practice. Research studies of conventional endodontic therapy document success rates of about (100% - endodontist abilities).
The keys to success are accurate:
Diagnosis, selection of appropriate cases for treatment,
Use of proper endodontic techniques, along with meticulous attention to detail and sterility during treatment.
Following proper endodontic therapy and restoration, treated teeth typically last a lifetime.
In the rare instances when endodontic treatment is not successful, the tooth can often be retreated successfully. Endodontic re-treatment can be done using conventional methods.
SCOPE OF ENDODONTIC
The extent of the subject has altered considerably in the last 50 years. Formerly, endodontic treatment confined itself to root canal filling techniques by conventional methods; even endodontic surgery, which is an extension of these methods, was considered to be in the field of oral surgery. Modern endodontics has a much wider field and includes the following:
Diagnosis of oral pain.
Protection of the healthy pulp from disease or injury.
Vital pulp therapy (direct and indirect capping).
Pulpotomy (conventional and partial).
Root canal treatment of infected root canals.
Surgical endodontics, which includes apicectomy, hemisection root amputation and replantation.
Value of Endodontics: Saving irreplaceable teeth
Avoiding free end saddles
Providing teeth for multiple splint abutments
Preservation of alveolar bone
Avoiding total edentulism
Facilitating restoration: after fracture of a tooth resulting in insufficient supra-gingival structure for a crown
Aid in accommodating attachments like keys and keyways
Limiting number of artificial teeth in RPD
Preserving teeth with greater bulk ( posterior ) to serve as RPD abutments
Retaining the most posterior bridge abutment Preserving enough teeth for use with a fixed bridge
Lessening of bridge span
Help to obtain a more esthetic prosthetic result
The Dental Pulp: The dental pulp is a connective tissue encased in a rigid hard tissue. It consists of cells, ground substance, and neural and vascular supplies. The pulp, in conjunction with the dentin that surrounds it, is referred to as the pulpo-dentin complex. Dentin is a specialized connective tissue of mesenchymal origin. It is laid down by highly differentiated and specialized odontoblasts and forms the bulk of the mineralized portion of the tooth Tubules contain the long narrow odontoblastic process. It is uncertain whether these processes travel to the midpoint of the dentin or the full distance to the dentin-enamel junction. The tubules are filled with fluid and fluid exchange may occur from the pulp outwards or from the enamel towards the pulp.
Peritubular dentin lines the tubules and is laid down by the odontoblast process. Peritubular dentin is thought to form as a normal consequence of aging and may be accelerated by stimuli such as caries, attrition, and abrasion. Occlusion of dentinal tubules by this process and by mineral crystals is called sclerosis and gives aged teeth their characteristic translucency.
Primary dentin forms during tooth development. Secondary dentin forms once the teeth are fully developed and is laid down evenly over the entire pulpal surface; it is also known as physiological or regular secondary dentin
Odontoblasts cell bodies are separated from mineralized dentin by an unmineralized layer known as predentin. Odontoblasts form a single layer of cells, but in histological section appears as a multilayered structure because their nuclei are at different levels. Odontoblasts are incapable of further division once fully mature, and if damaged, may be replaced from undifferentiated mesenchymal cells. The remainder of the pulp consists of ground substance into which are embedded fibroblasts and inflammatory cells and a complex network of blood vessels and nerve fibers.
The Functions of the Pulp
The primary function of the pulp is formative and defensive. Defense reactions are essential to the survival of the pulp. The pulp has also been thought to act as a sensory organ that warns against disease (i.e., loss of tooth substance) by eliciting pain, but this is a relatively poor warning system considering the number of teeth whose pulps become irreversibly inflamed, apparently without warning. Any tooth deformation resulting from loads may be detected by proprioceptors in the pulp. Although the existence of a proprioceptive mechanism has not been proven, it does offer an explanation for the susceptibility of pulpless teeth to fracture.
The Vascular Supply of the Pulp
The vascular system of the pulp helps it to overcome problems of encapsulation within the rigid tooth. Arterioles from the dental arteries (A. facialis) enter through the apical foramina and pass centrally through the pulp, giving off lateral branches, which divide further into capillaries. Smaller vessels reach the odontoblastic layer, where they divide extensively to form a plexus below and within the odontoblastic layer. Venous return is collected by a network of capillaries, which unite to form venules coursing down the central portion of the pulp. The unique feature in this arrangement is the arteriovenous shunt, which prevents build-up of unsustainable pressure in the rigid environment. Lymphatic vessels have not been definitely confirmed. In general, with age, the blood supply diminishes and its architecture becomes simpler. This diminished blood supply may render a pulp more susceptible to irreversible damage.
The Nerve Supply of the Pulp
The dental pulp is richly innervated with sensory and autonomic nerve fibers. These enter the pulp with the blood vessels through the apical foramina. As the nerve bundles pass coronally they divide into smaller branches and form the dense plexus of Raschow. Individual axons may branch into many terminal filaments, which in turn may enter the dentinal tubules; one axon may innervate up to 100 dentinal tubules. Some tubules may contain several nerve fibers.
The autonomic nerve supply consists of sympathetic fibers, which control the microcirculation. The sensory innervation consists of two (possibly three) types of fibers. The faster conducting A-d-fibers are thought to be responsible for sharp, localized dentinal pain experienced during drilling, probing, air drying, application of hyperosmotic fluids, and heating or cooling dentin. The common feature of these stimuli is that they cause rapid movement of fluid in the dentinal tubules, which cause mechanical distortion of tissue in the pulp-dentin border and stimulates the A-d-fibers (the hydrodynamic theory). Opening dentinal tubules by acid etching may increase sensitivity of dentin. Conversely, blocking the tubules, for example by composite resins or naturally by sclerosis, prevents fluid flow and desensitizes dentin.
Stimulation of the slower conducting, unmyelinated C-fibers are thought to give rise to the duller, throbbing, less localized pain. The C-fibers are activated by thermal, mechanical or chemical stimuli reaching the deeper parts of the pulp
A third type of nerve, the A-ß-fibers, is myelinated and has the most rapid conduction velocity. These fibers are thought to respond to non-noxious mechanical stimulation of the intact crown and may be important in regulating mastication and loading of teeth, but they also respond to stimulation of dentin.
The Periradicular Tissues—Cementum
Cementum covers the radicular dentin. The cementum is primarily an inorganic tissue and is more impervious than dentin. Cellular cementum contains cementocytes which communicate with each other via canaliculi and with dentin. It is usually found in the apical and furcation regions of the tooth. Sharpey’s fibers may be embedded in cellular cementum. Acellular cementum forms the innermost layer of cementum and is devoid of cells. It covers almost the whole root surface in a thin hyaline layer. It contains closely packed mineralized periodontal fibers. Intermediate cementum is found at the cementodentinal junction and has characteristics of both cementum and dentin. The function of cementum is to provide attachment for the periodontal ligament fibers, which suspend the tooth from the alveolar bone, and repair.
The Periradicular Tissues— Periodontal Ligament
The periodontal ligament is a dense fibrous connective tissue that supports the tooth and attaches it to its socket. Its principal component is collagen, which is embedded in a gel-like matrix. The fibers are arranged in specific groups with individual functions. These include gingival, transseptal, alveolar crest, horizontal, oblique, and apical fibers. Functional adaptation may take place in the broad zone known as the intermediate plexus. The main cells of the ligament are fibroblasts with occasional inflammatory cells. The root sheath of Hertwig, which helps root formation, does not totally involute once root formation is complete, but degenerates into what resembles a perforated bag of epithelial cells, sometimes described as the rests of Malassez. These cells can proliferate when stimulated by inflammation to form a cyst.
The blood supply to the periodontal ligament originates from the inferior dental artery. Arterioles enter the ligament near the apex of the root and from lateral aspects of the alveolar socket and branch into capillaries within the ligament in a polyhedric pattern along the long axis of the tooth. Collagen fibers run through the spaces. The blood vessels are closer to the bone than to the cementum. Venules drain the apex through apertures in the bony wall of the socket and into the marrow spaces.
Nerve bundles enter the periodontal ligament through numerous foramina in the alveolar bone. They branch and end in small rounded bodies near the cementum. The nerves carry pain, touch, and pressure sensations and form an important part of the feedback mechanism of the masticatory apparatus.
Functions of the periodontal ligament includes proprioceptive functions and acting as a viscoelastic cushion because of its fibers and hydraulic fluid systems (blood vessels and their communication with vessel reservoirs in the bone marrow and interstitial fluid of the ligament). The ligament has great adaptive capacity; it responds to functional overload by widening to relieve the load on the tooth. Vascular communications between the pulp and periodontium form pathways for transmission of inflammation and microorganisms between the tissues.
The Periradicular Tissues—Alveolar Bone
Alveolar bone supports the teeth by forming the other attachment for fibers of the periodontal ligament. It consists of two plates of cortical bone separated by spongy bone. In some areas, alveolar bone is thin with no spongy bone. The alveolar bone and cortical plates are thickest in the mandible. The shape and structure of the trabeculae of spongy bone reflect the stress-bearing requirements of a particular site. The surfaces of the inorganic parts of bone are lined by osteoblasts responsible for bone formation. Those cells which become incorporated within the mineral tissue are called osteocytes and maintain contact with each other via canaliculi; osteoclasts are responsible for bone resorption and may be seen in the Howship’s lacunae.
Pulp space or cavity : it is arbitrary divided into the pulp chamber (coronal) and root (radicular) canals. Pulp chamber usually described as that portion within the crown, it is a single cavity, the dimensions and shape were vary according to the outline of the crown and the structure of the roots and the age. There are projection or prolongations in the roof of the pulp chamber that correspond to the various major cusps or lobes of the crown which is called (pulp horn). In multirooted teeth the depth of the pulp chamber depends upon the position of the root furcation and my extend beyond the anatomical crown.
In the young teeth the outline of the pulp chamber resembles the shape of the exterior of the dentine. With the age the dentinal tubules and pulp chamber becomes reduced in size particularly in the areas where there has been caries, attrition, aberration and exposure to operative treatment, So the CHAMBER MAY THEN BECOME IRREGULAR IN OUTLINE, in addition to reduction in the content of the pulp. For example, in molars, the roof and floor of the chamber show more dentin formation, eventually making the chamber almost disclike in configuration…..
The root canals are continuous with the pulp chamber and normally their greatest diameters is at the pulp chamber level which is called “canal orifices”. Because the roots tend to taper toward the apex, the canals also have a tapering from which ends in constricted openings at the root end, the “apical foramina” . it is possible for any root of tooth to have a number of apical foramina. The branching of the main canals to these foramina called Accessory canals and the root apex referred to as a delta system because of its complexity. Generally , these aberrations are neither detectable nor predictably negotiable and are neither well debrided nor obturated.
Lateral canals can be found anywhere along the root length and tends to be at right angles to the main root canals especially in the coronal (furcal) and middle third if the roots. The accessory and lateral canals may demonstrated only by histological examination. The presence of these canals in teeth with diseased pulps and periradicular areas allows an interchange of inflammatory break down and bacteria from the pulp to the periradicular area and viscera which may influence the outcome of root canal treatment success and maintenance of periodontal health.
Apical foramen: As the epithelial root sheath proliferates downward and away from crown, it enclosed more dental papilla until only a basal (apical) opening remains. At the first the foramen located usually at the end of anatomic root. With the age and development it becomes smaller and more eccentric. This eccentricity is more pronounced as apical Cementum forms, changing again as Cementum deposition continues passively or in association with coronal wear and tooth drifting. it is possible for any root of tooth to have a number of apical foramina especially in the multirooted teeth, the largest on referred as apical foramen and smaller as accessory canals. Apical foramen size in the mature tooth ranges usually 0.3-0.6 mm, the largest diameters being found on the distal canal of lower molars and palatal root of upper molars. Foramen size and location are unpredictable and difficult to accurately determined clinically. The average distance between the apical foramen and the most apical end of root ranged 0.2-2.0 mm. furthermore, the apical constriction tends to occurs about 0.5-1.0 mm from apical foramen (coronally). Ideally the apical constriction should be used as a natural “stop” in root canal treatment, and the integrity of the constriction should be maintained during treatment if complications are to be avoided.
Root and canal anatomy
Although root shape in cross section is variable, there are six general configurations: round, oval, deep oval, bowling pin, kidney (bean), and hourglass.
Shape and location of canals are related greatly by root shape. Different shapes may appear at any level in a single root teeth. One root may contain tow canals, a basic rule is to assume that the root contains two canals until proved otherwise. The most frequent roots includes: upper premolars, MB root of upper molars, lower incisors, lower premolars and distal root of lower molars. Most canals are curved, and most curvatures occur in a facial-lingual direction. Therefore, a curved canals is often undetectable on routine radiograph. As a rule, when 2 canals occur in a root thy tend to be round to oval. In the deep facial-lingual root with root mesial or distal concavities (hourglass or kidney bean shaped), a single canal may have a bowling pin or hourglass shape. Regardless of the shape in the cervical third, in the apical curvature the root (and canal) tends to become more round to oval.
The number of canals in a root reflects the facial-lingual depth and shape of the root at each level, the deeper the root, the more likely that there are the 2 separate definitive canals. If the root tapers toward the apical third there is a greater likelihood that the canals will converge to exit as a single canal.
Irregularities and aberrations are frequent in fact, commonplace. This is particularly true in posterior teeth. Such aberrations include : hills and valleys in canal walls, intercanal communications (isthmuses between canals) and others
Types of configurations of root canal
Oral pain often is difficult to pinpoint. Because of the vast network of nerves in the mouth, the pain of a damaged or diseased tooth often is felt in another tooth or in the head, neck or ear. An endodontist may be helpful in either diagnosing or treating this type of pain. All endodontically treated teeth require special restorative care and treatment (either a filling, inlay, onlay, or crown) after endodontic care is finished.