Endodontics

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Chapter 7

Endodontics

Steven Levine

Diagnosis

1. What is the proper role of the pulp tester in clinical diagnosis?
The pulp tester excites the nervous system of the pulp through electrical stimulation. However, the pulp tester suggests only whether the tooth is vital or nonvital; the crucial factor is the vascularity of the tooth. The pulp test alone is not sufficient to allow a diagnosis and must be combined with other tests.
2. What is the importance of percussion sensitivity in endodontic diagnosis?
Percussion sensitivity is a valuable diagnostic tool. Once the infection or inflammatory process has extended through the apical foremen into the periodontal ligament (PDL) space and apical tissues, pain is localizable with a percussion test. The PDL space is richly innervated by proprioceptive fibers, which make the percussion test a valuable tool.
3. Listening to a patient’s complaint of pain is a valuable diagnostic aid. What differentiates reversible from irreversible pulpitis?
In general, with reversible pulpitis, pain is elicited only on application of a stimulus (e.g., cold, sweets). The pain is sharp and quick but disappears on removal of the stimulus. Spontaneous pain is absent. The pulp is generally noninflamed. Treatment usually is a sedative dressing or a new restoration with a base. Irreversible pulpitis is generally characterized by pain that is spontaneous and lingers for some time after stimulus removal. There are various forms of irreversible pulpitis, but all require endodontic intervention.
4. What are the clinical and radiographic signs of an acute apical abscess?
Clinically, an acute apical abscess is characterized by acute pain of rapid onset. The affected tooth is exquisitely sensitive to percussion and may feel “elevated” because of apical suppuration. Radiographic examination may show a totally normal periapical complex or slightly widened PDL space because the infection has not had enough time to demineralize the cortical bone and reveal a radiolucency. Electric and thermal tests are negative.
5. Discuss the importance of inflammatory resorption.
Resorption after avulsion injuries depends on the thickness of cementum. When the PDL does not repair and the cementum is shallow, resorption penetrates to the dentinal tubules. If the tubules contain infected tissue, the toxic products pass into the surrounding alveolus to cause severe inflammatory resorption and potential loss of the tooth.
6. After a luxation injury, ankylosis and replacement resorption can occur. How does this process take place?
After extensive dental trauma that affects a large part of the root surface, an acute inflammatory response ensues. Because of the inflammatory response, the root surface loses its cementum. The cells that repopulate the root surface are often bone cells instead of periodontal ligament cells, which migrate more slowly. Thus, the migratory precursor bone cells produce bone that forms where cementum was and directly contacts the root without any attachment complex, such as the PDL. This bone ingrowth, which continually forms and resorbs the root, is characteristic of replacement resorption.
7. A patient presents with a gumboil, or fistula. What steps do you take to diagnose the cause or determine which tooth is involved?
All fistulas should be traced with a gutta percha cone because the originating tooth may not be directly next to the fistula. Fistulas positioned high on the marginal gingiva, with concomitant deep probing and normal response of teeth to vitality testing, may have a periodontal cause.
8. Why is it often difficult to find the source of pain in endodontic diagnosis when a patient complains of radiating pain without sensitivity to percussion or palpation?
Teeth are often the source of referred pain. Percussion or palpation pain may be lacking in a tooth in which the inflammatory process has not reached the proprioceptive fibers of the periodontal ligament. The pulp contains no proprioceptive fibers.
9. What is the anatomic reason that pain from pulpitis can be referred to all parts of the head and neck?
In brief, nerve endings of cranial nerves (CNs) VII (facial), IX (glossopharyngeal), and X (vagus) are profusely and diffusely distributed within the subnucleus caudalis of the trigeminal cranial nerve (CN V). A profuse intermingling of nerve fibers creates the potential for referral of dental pain to many sites.
10. Is there any correlation between the presence of symptoms and histologic condition of the pulp?
No. Several studies have shown that the pulp may actually degenerate and necrose over a period of time without symptoms. Microabscess formation in the pulp may be totally asymptomatic.
11. Describe the process of internal resorption and the necessary treatment.
Internal resorption begins on the internal dentin surface and spreads laterally. It may or may not reach the external tooth surface. The process is often asymptomatic and becomes identifiable only after it has progressed enough to be seen radiographically. The cause is unknown. Trauma is often but not always implicated. Resorption that occurs in inflamed pulps is characterized histologically by dentinoclasts, which are specialized, multinucleated giant cells similar to osteoclasts. Treatment is prompt endodontic therapy. However, once external perforation has caused a periodontal defect, the tooth is often lost.
12. How can one deduce a clinical impression of pulpal health by examining canal width on a radiograph?
Although not a definitive diagnostic tool, pulp chamber and root canal width on a radiograph may suggest pulp health. When compared with adjacent teeth, very narrowed root canals usually indicate pulpal pathology, such as degeneration caused by prior trauma, capping, pulpotomy, or periodontal disease. Conversely, root canals that are very wide in comparison to adjacent teeth often indicate prior pulp damage that has led to pulpal necrosis.
13. What is the significance of the intact lamina aura in radiographic diagnosis?
The lamina aura is the cribriform plate or alveolar bone proper, a layer of compact bone lining the socket. Because of its thickness, an x-ray beam passing through it produces a white line around the root on the radiograph. Byproducts of pulpal disease, passing from the apex or lateral canals, may degenerate the compact bone; its loss can be seen on a radiograph. However, this finding is not always diagnostic, because teeth with normal pulp may have no lamina aura.
14. Which radiographic technique produces the most accurate radiograph of the root and surrounding tissues?
The paralleling or right angle technique is best for endodontics. The film is placed parallel to the long axis of the tooth and beam at a right angle to the film. This technique allows the most accurate representation of tooth size.
15. What is the definition of a true combined lesion?
A true combined lesion is caused by endodontic and periodontal disorders that progress independently. The lesions may join as the periodontal lesion progresses apically. Such lesions, if any chance of healing is to occur, require endodontic and aggressive periodontal therapy. Usually, the prognosis is determined more by the extent of the periodontal lesion.
16. Why does the radiographic examination not show periapical radiolucencies in certain teeth with acute abscesses?
One study showed that 30% to 50% of bone calcium must be altered before radiographic evidence of periapical breakdown appears. Therefore, in acute infection, apical radiolucencies may not appear until later, as treatment progresses.
17. Why do pulpal-periapical infections of the mandibular second and third molars often involve the submandibular space?
Extension of any infection is closely tied to bone density, proximity of root apices to cortical bone, and muscle attachments. The apices of the mandibular second and third molars are usually below the mylohyoid attachment; therefore, infection usually spreads to the lingual and submandibular spaces. The masticator space is often also involved.
18. A patient presents with a large swelling involving her chin. Diagnostic tests reveal that the culprit is the lower right lateral incisor. What factor determines whether the swelling extends into the buccal fold or points facially?
A major determining factor in the spread of an apical abscess is the position of the root apex in relation to local muscle attachments. In this particular case, the apex of the lateral incisor is below the level of the attachment of the mentalis muscle; therefore, the abscess extends into the soft tissues of the chin.
19. A middle-aged woman has been referred for diagnosis of multiple radiolucent lesions around the apices of her mandibular incisors. The patient is asymptomatic, the teeth are normal on vitality tests, no cortical expansion is noted, and the periodontium is normal. Medical history and blood tests are normal. What is your diagnosis?
The most likely diagnosis is periradicular cemental dysplasia or cementoma. This benign condition of unknown cause is characterized by an initial osteolytic phase in which fibroblasts and collagen proliferate in the apical region of the mandibular incisors, replacing medullary bone. The teeth remain normal to all testing. Eventually, cementoblasts differentiate to cause reossification of the area. Treatment is to monitor over time.

Clinical Endodontics (Treatment)

20. What endodontic treatment guidelines should be followed for patients taking bisphosphonates?
The literature suggests that patients taking intravenous (IV) bisphosphonates are at a much higher risk for developing bisphosphonate-associated osteonecrosis of the jaw (BONJ) than patients taking oral bisphosphonates. As recommended for patients with osteoradionecrosis, if the coronal structure is nonrestorable, it is prudent to perform nonsurgical endodontic treatment on involved teeth that would usually be extracted, even if only the roots are retained.
21. What is current thinking on use of the rubber dam?
The dam is an absolute necessity for treatment. It ensures a surgically clean operating field that reduces the chance of cross-contamination of the root canal, retracts tissues, improves visibility, and improves efficiency. It protects the patient from aspiration of files, debris, irrigating solutions, and medicaments. From a medicolegal standpoint, use of the dam is considered the standard of care.
22. What basic principles should be kept in mind for proper access opening?
Proper access is a crucial and often overlooked aspect of endodontic practice. The root canal system is usually a multicanaled configuration with fins, loops, and accessory foramina. When possible, the opening must be of sufficient size, position, and shape to allow straight-line access into the canals. Access of inadequate size and position invites inadequate removal of caries, compromises proper instrumentation, and inhibits proper obturation. However, overzealous access leads to perforation, weakening of tooth structure, and potential fracture.
23. What is current thinking on the use of irrigating solutions in endodontics?
Irrigating solutions, used in copious amounts during instrumentation, are critical in root canal therapy. Constant irrigation helps remove dentinal debris to prevent blockage, can dissolve organic tissue in the root, and exerts an antimicrobial effect in the root canal. Sodium hypochlorite, minimally in a 0.5% solution, exerts an antimicrobial effect, and a 2% chlorhexidine irrigation can eradicate Enterococcus faecalis biofilm in vitro and in vivo.
24. Of what materials are endodontic files made?
Hand instruments such as K-files, Hedstrom files, reamers, and K-Flex files are made from stainless steel. In the past, these instruments were made of carbon steel, but stainless steel bends more easily, is not as brittle, and can be autoclaved without dulling.
More recently, the explosion of nickel-titanium rotary and hand instruments has occurred. Nickel titanium (Ni-Ti) is very flexible and resists fracture well. The alloy has good elastic flexibility because of its low elastic modulus. The alloy is approximately 55% nickel and 45% titanium by weight, and its superelastic behavior allows the files to return to their original shape after the file is removed from the canal.
25. Describe the metallurgic characteristics of nickel titanium rotary instruments that influence their use?
Ni-Ti is a metallic alloy that exists in two crystalline forms, austenite and martensite. The transformation of the instrument between these two phases occurs when stresses that are applied suddenly change, such as the speed of use of the rotary or resistance, such as rotation around a narrowing curved canal. At such times, instrument separation can occur. The austenite phase occurs mainly at higher temperatures, whereas the martensite phase is predominant at lower temperatures and has higher fatigue resistance then the austenite form. Ni-Ti or nitinol wire has been subjected to a thermomechanical process that resulted in the manufacture of M-wire instruments, which exist more in the martensite phase at room temperature, versus the conventional Ni-Ti wire, which is in the austenite phase at room temperature. The M-wire instruments have much greater resistance to cyclic fatigue.
26. What are the characteristics of a K-file?
The K-file is made by machine grinding of stainless steel wire into a square shape (some companies produce a triangular shape). The square wire is then twisted by machines in a counterclockwise direction to produce a tightly spiraled file.
27. What are the characteristics of a reamer?
A reamer is made by machine twisting of a triangular stainless steel stock wire in a counterclockwise direction but into a less tightly spiraled instrument than the K-file.
28. How does the K-flex file differ from a reamer?
The K-flex file is produced from a rhomboid or diamond-shaped stainless steel stock wire twisted to produce a file. However, the two acute angles of the rhombus produce a cutting edge of increased sharpness and cutting efficiency. The low flutes made from the obtuse angles form an area for debris removal.
29. How does filing differ from reaming?
Filing establishes its cutting action on withdrawal of the instrument. The instrument is removed from the canal without turning. Thus, it basically uses a push-pull motion. Reaming is done by placing the instrument in the canal, rotating, and withdrawing.
30. What is the recommended use for Gates-Glidden and Reeso drills?
These two types of engine-driven instruments, especially the Gates-Glidden drills, are useful in the new recommended instrumentation technique of step-down preparation. They are helpful for the initial coronal preparation of the canal, thereby allowing easier, more efficient, and less traumatic apical preparation.
31. What is RC-prep? How is it used?
RC-prep is composed of ethylenediaminetetraacetic acid (EDTA) and urea peroxide in a Carbowax base. Its use as a canal lubricant is also enhanced by combination with sodium hypochlorite, which produces a bubbling action, allowing enhanced removal of dentinal debris and permeability into the tubules.
32. What is the “Tooth Slooth”?
Diagnosis of tooth fractures is often difficult. This simple but highly effective and well-designed instrument allows biting force to be applied one cusp at a time into an indentation (the cusp receptacle on the Slooth), thereby selectively examining each cusp separately in an attempt to locate a weakness caused by fracture.
33. What is the status of the acceptability of root canal obturation materials?
Gutta percha remains the most popular and accepted filling material for root canals. Numerous studies have demonstrated that it is the least tissue-irritating and most biocompatible material available. Although differences occur among manufacturers, gutta percha contains transpolyisoprene, barium sulfate, and zinc oxide, which provide an inert, compactible, dimensionally stable material that can adapt to the root canal walls.
N-2 pastes and other paraformaldehyde-containing pastes have not been approved by the U.S. Food and Drug Administration (FDA). Several studies have shown conclusively that such root-filling pastes are highly cytotoxic in tissue culture; reactions to bone include chronic inflammation, necrosis, and bone sequestration. Compared with gutta percha, the pastes are highly antigenic and perpetuate inflammatory lesions. Therefore, they are not considered the standard of endodontic care.
Recently, Resilon has been gaining popularity as an obturation system. It is a thermoplastic synthetic polymer root-filling material, containing bioactive glass and radiopaque fillers. The RealSeal technique, which uses Resilon, involves smear layer removal and then the use of a self-etching primer and sealer to provide a chemical bond between the filling material and sealer.
34. Thermafil has become a popular technique. Describe some of its basic characteristics.
Thermafil is a patented endodontic obturation technique that has become popular. After proper débridement and shaping of the root canal, the final working length is confirmed with an Ni-Ti verifier, which passively reaches the apical constriction. A corresponding Thermafil obturator made of a radiopaque plastic material (flexible central carrier), with a layer of alpha phase gutta percha, is selected. The obturator is heated and, on heating, the gutta percha is said to have excellent flow properties. The carrier and heated gutta percha are inserted to working distance and severed.
35. What is the proper apical extension of a root canal filling?
The proper apical extension of a root canal filling has been discussed extensively, and the debate continues. In the past, recommendations were made to fill a root canal to the radiographic apex in teeth that exhibited necrosis or areas of periapical breakdown and to stop slightly short of this point in vital teeth. It is now generally recommended that a root canal be filled to the dentinocementum junction, which is 0.5 to 2 mm from the radiographic apex. Filling to the radiographic apex is usually overfilling or overextending and increases the chance of chronic irritation of periapical tissues.
36. Describe the walking bleach technique.
The walking bleach technique is used to bleach nonvital teeth with roots that have been obturated. The technique involves the placement of a thick white paste composed of sodium perborate and Superoxol (35% H2O2) in the tooth chamber with a temporary restoration. Several repetitions of this procedure, along with in-office application of heat to Superoxol-saturated cotton pellets in the tooth chamber, are efficacious.
37. Extensive cervical resorption after bleaching of pulpless teeth with the walking bleach technique using Superoxol, sodium perborate, and heat has been reported. What is the cause?
In approximately 10% of all teeth, defects at the cementoenamel junction allow dentinal tubules to communicate from the root canal system to the PDL. These tubules remain open, without sclerosis, if the tooth becomes pulpless at a young age. It is thought that the bleaching agents may leach through the open tubules to cause the resorption. Therefore, a barrier of some type is recommended, such as zinc, phosphate cement, or some type of light canal bonding agent.
38. The treatment of cracked teeth is among the most complex decisions in endodontics and restorative dentistry. What tools should be used for the diagnosis of cracked teeth?
1. Bite test with cotton roll and bite stick
2. Periodontal probing
3. Pulp testing
4. Transillumination
5. Methylene blue dye staining
6. Use of the microscope
7. Radiographs will not directly show a crack but will reveal lateral defects in long-standing cracks causing periodontal defects.
39. Describe the crown-down pressureless technique of root canal instrumentation.
With the crown-down pressureless technique, the canal is prepared in a coronal to apical direction by initially instrumenting the coronal two thirds of the canal before any apical preparation. This technique, popularized by Marshall and Pappin, minimizes apically extruded debris and eliminates coronal binding of instruments, thereby making apical preparation more difficult.
40. What is the balanced forced concept of root canal instrumentation and preparation?
The balanced force technique, popularized by Roane and Sabala in the mid-1980s, is based on the idea of balancing the cutting forces over a greater area and focusing less force on the area where the file tip engages dentin. The instruments of choice are K-type files, especially the Flex-R file, made with a triangular cross section and modified tip. This design allows for a decreased cross-sectional dimension, an increase in flute depth, and greater flexibility. The technique involves a quarter turn clockwise, with slight apical pressure, to engage dentin and then a half to three-quarter turn counterclockwise to remove debris from the first turn. After a few turns, the file is removed, cleaned and the canal copiously irrigated. Using a continuous motion, canals can be prepared with less ledging, less zipping of the apex, and lower chance of perforations.
41. What is the frequency of fourth canals in mesial roots of the maxillary first molars?
In an extensive study of maxillary first molars, 70% of the mesiobuccal roots contained a larger buccal and smaller lingual canal or two separate canals and foramina. This finding shows the importance of searching for a fourth canal to ensure clinical success.
42. What about the manner of storage of an avulsed permanent tooth and its relationship to postreplantation success?
After 15 to 20 minutes of extraoral exposure, the cell metabolites in the periodontal ligament have been depleted and need to be reconstituted before replantation. If available, the best storage media is Hanks’ Balanced Salt Solution. This solution is biocompatible and can keep the periodontal ligament cells viable for hours because of its ideal pH and osmolality. Research has shown that soaking an avulsed tooth in this solution for 30 minutes prior to replantation can achieve a 90% success rate. This solution is available as Save-A-Tooth, is found in schools, and is prevalent at sporting events. If not available for storage, the best alternatives are saliva, milk, or saline.
43. What is the current guideline for how long to splint an avulsed, mature tooth with complete root formation?
A replanted mature tooth (root fully formed) should be splinted for a minimal period of 1 week. This amount of time is usually sufficient to ensure that periodontal support is adequate, because gingival fibers are usually healed by this time.
44. What is the current thinking on the need for prophylactic root canal treatment on a mature, avulsed permanent incisor with closed apical foramen, where injury occurred less than one hour prior to treatment?
Andreasen recommended that for an avulsed permanent incisor with mature apical formation (≤1 mm), endodontic treatment should be performed prophylactically because the chance of pulp necrosis is extremely high. However, treatment should be delayed for 1 week after replantation because the root canal procedure and extraoral handling could adversely affect the periodontal ligament fibers. Therefore, replant and then splint for 1 week to allow periodontal fiber splicing; perform prophylactic endodontic treatment prior to splint removal.
45. What is the recommendation for endodontic therapy for the avulsed permanent incisor (apex > 1 mm) in which treatment is initiated within 3 hours of injury?
Andreasen recommended that in such cases, it is justified to replant and wait for possible revascularization of the pulp. However, the radiographic examination should be accomplished at 2 and 3 weeks postreplant to examine for any evidence of apical periodontitis and root resorption. If any evidence is fond, endodontic therapy should be started immediately, with calcium hydroxide placed to arrest root resorption.
46. When an avulsed tooth is replanted, what are the recommendations concerning rigid or functional splinting?
Studies have shown that an early functional stimulus may improve the healing of luxated teeth. It is advantageous to reduce the time of fixation to the time necessary for clinical healing of the periodontium, which may take place in a few weeks. Andreasen noted that prolonged rigid immobilization increases the risk of ankylosis; thus, the splint should allow some vertical movement of the involved teeth.
47. What is the physiologic basis for the use of calcium hydroxide pastes for resorptive defects and avulsed teeth?
The theory behind the use of calcium hydroxide pastes is that areas of resorption have an acidic pH of approximately 4.5 to 5. Such areas are more acidic than normal tissue because of the effects of inflammatory mediators and tissue breakdown products. The basic pH of calcium hydroxide neutralizes the acidic pH, thereby inhibiting the resorptive process of osteoclastic hydrolases.
48. What is the current thinking on the use of intracanal medications in endodontic practice?
The use of intracanal medications has changed greatly over the years. In the early years of endodontics as a specialty, many intracanal agents were used, such as formocresol, cresatin, and PBSC (penicillin-bacitracin-streptomycin-chloramphenicol paste). Calcium hydroxide pastes have become popular because several studies have shown their antibacterial effects. Their high pH can cause inactivation of bacterial enzymes, neutralize endotoxins, and dissolve organic tissue.
More recently, a 2% chlorhexidine gel has been studied and used as an intracanal agent, and a combination of calcium hydroxide and chlorhexidine has been found to be effective against E. faecalis, an organism shown to be prevalent in failed endodontic cases.
Therefore, the use of intracanal calcium hydroxide or chlorhexidine is considered of great importance in cases of treatment failure, teeth with apical lucencies, or teeth with persistent symptoms.
49. Discuss the variations of postoperative pain in one-visit versus two-visit endodontic procedures.
Several studies have shown no difference in postoperative pain in one-visit versus two-visit endodontic procedures. One study found that single-visit therapy resulted in postoperative pain approximately half as often as multiple-visit therapy.
50. What is the treatment of choice for an intruded maxillary central incisor with a fully formed apex?
Repositioning or surgical extrusion should be done immediately, with splinting for 7 to 10 days. Because pulpal necrosis is the usual outcome, pulpectomy prior to splint removal and placement of calcium hydroxide are recommended. Close observation every few months is needed.
51. What is the desired shape of the endodontic cavity (root canal) for obturation in lateral and vertical condensation techniques?
The canal should be instrumented and shaped so that it has a continuously tapering funnel shape. The narrowest diameter should be at the dentinocemental junction (0.5 to 1 mm from apex) and the widest diameter at the canal opening.
52. Are electronic measuring devices for root canal of any clinical value in endodontic practice?
Yes. Electronic measuring devices have been shown by several investigators to be accurate. In general, they work by measuring gradients in electrical resistance when a file passes from dentin (insulator) to conductive apical tissues. When the tip of the file contacts apical tissue, the circuit is complete, resistance decreases, and current can flow. This is announced to the operator by a signal such as flashing lights, beep, or dial readout, depending on the unit. These units are useful when the apex is obscured on a radiograph by sinus superimposition, other roots, or osseous structures.
53. What is the accepted material of choice for pulp-capping procedures?
Over the years, many materials have been studied for pulp capping. The importance of a biocompatible substance on an exposed pulp can prevent bacterial microleakage and protect the pulp against irritation caused by an operative procedure and toxicity of operative restorative procedures. For many years, calcium hydroxide was the material of choice for pulp capping and is still widely used. Calcium hydroxide, applied to exposed pulp, seems to cause necrosis of the underlying tissue, but the tissue contiguous to this forms calcific bridges. More recently, MTA (mineral trioxide aggregate) applied to pulp has been shown to stimulate dentin bridges, but with no significant differences from the use of calcium hydroxide. Recent studies have also shown that Biodentine, a calcium silicate cement with dentin-like mechanical properties, can stimulate reparative dentin when it contacts vital pulp tissue.
54. Describe the process of apexification.
Apexification involves the placement of agents in the pulpless permanent tooth, with an incompletely formed apex, to stimulate continued apical closure. Calcium hydroxide pastes have traditionally been the material of choice to achieve this, but a newer technique, gaining popularity, involves the use of MTA. The difference is that the traditional calcium hydroxide technique is performed over several visits, depending on the inductive effect of the calcium hydroxide to form a hard tissue barrier. The MTA technique is a one-visit technique during which the MTA is placed apically to form an apical barrier; MTA has been shown to support new hard tissue formation in the apical area of immature necrotic teeth.
55. Describe the process of regenerative endodontic treatment, sometimes called pulpal revascularization, that is often used for the treatment of nonvital immature teeth?
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May 10, 2015 | Posted by in General Dentistry | Comments Off on Endodontics
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