C0093067x ove A. Peters



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Cleaning and Shaping of the Root Canal System




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Ove A. Peters




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Christine I. Peters




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FRAMEWORK FOR ROOT CANAL TREATMENT




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Clinical endodontics encompasses a number of treatments, but perhaps the most important is treating pulps and root canal systems (with or without periradicular pathosis of pulpal origin) so that patients can retain their natural teeth in function and esthetics. The treatment of traumatic dental injuries and prophylactic treatment of vital pulps to maintain vitality are different from pulpectomies in which root canal instrumentation is required. However, endodontic therapy essentially is directed toward one specific set of aims: to cure or prevent periradicular periodontitis.295




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Routine orthograde root canal treatment is a predictable and usually highly successful procedure both in relatively straightforward (Fig. 9-1) and more difficult cases (Figs. 9-2 and 9-3). In recent studies and reviews, favorable outcome rates of up to 95% were reported for the treatment of teeth diagnosed with irreversible pulpitis22,62,90; favorable outcome rates of up to 85% were reported for necrotic teeth.61,91,200,207




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Figure 9-1 Effect of routine root canal treatment of a mandibular molar. A, Preoperative radiograph of tooth #19 shows radiolucent lesions adjacent to both mesial and distal root apices. B, Working length radiograph shows two separate root canals in the mesial root and two merging canals in the distal root. C, Posttreatment radiograph after shaping of root canal systems with nickel-titanium rotary files and obturation with thermoplasticized gutta-percha. D, Six-month recall radiograph after restoration of tooth #19 with an adhesively inserted full ceramic crown; some periradicular bone fill can be seen. E, One-year recall radiograph shows evidence of additional periradicular healing. F. Five-year recall radiograph; the tooth not only is periapically sound, but also clinically asymptomatic and fully functional.






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Figure 9-2 Root canal treatment in a case of apical and interradicular pathosis. A, Preoperative radiograph of tooth #19 shows an interradicular lesion. B and C, Postoperative radiographs after root canal preparation and obturation. Note the lateral canal in the coronal third of the root canal. D and E, Two-month recall radiograph suggests rapid healing. (Courtesy Dr. H. Walsch.)






To date, many treatment modalities, including nickel-titanium (NiTi) rotary instruments, have not been shown to have a statistically relevant impact on treatment outcomes.200 This poses a real problem in the age of evidence-based therapy, because a new therapeutic technique should provide a better result than standard procedures in clinical tests. The small number of relevant prospective clinical studies is only partly offset by numerous in vitro experiments. This chapter includes pertinent information from such studies, as well as results from our own experiments, because rotary nickel-titanium instruments have become widely used adjuncts in root canal treatment.

FRAMEWORK FOR ROOT CANAL TREATMENT




Body_ID: HC009001




Clinical endodontics encompasses a number of treatments, but perhaps the most important is treating pulps and root canal systems (with or without periradicular pathosis of pulpal origin) so that patients can retain their natural teeth in function and esthetics. The treatment of traumatic dental injuries and prophylactic treatment of vital pulps to maintain vitality are different from pulpectomies in which root canal instrumentation is required. However, endodontic therapy essentially is directed toward one specific set of aims: to cure or prevent periradicular periodontitis.295




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Routine orthograde root canal treatment is a predictable and usually highly successful procedure both in relatively straightforward (Fig. 9-1) and more difficult cases (Figs. 9-2 and 9-3). In recent studies and reviews, favorable outcome rates of up to 95% were reported for the treatment of teeth diagnosed with irreversible pulpitis22,62,90; favorable outcome rates of up to 85% were reported for necrotic teeth.61,91,200,207




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Figure 9-1 Effect of routine root canal treatment of a mandibular molar. A, Preoperative radiograph of tooth #19 shows radiolucent lesions adjacent to both mesial and distal root apices. B, Working length radiograph shows two separate root canals in the mesial root and two merging canals in the distal root. C, Posttreatment radiograph after shaping of root canal systems with nickel-titanium rotary files and obturation with thermoplasticized gutta-percha. D, Six-month recall radiograph after restoration of tooth #19 with an adhesively inserted full ceramic crown; some periradicular bone fill can be seen. E, One-year recall radiograph shows evidence of additional periradicular healing. F. Five-year recall radiograph; the tooth not only is periapically sound, but also clinically asymptomatic and fully functional.






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Figure 9-2 Root canal treatment in a case of apical and interradicular pathosis. A, Preoperative radiograph of tooth #19 shows an interradicular lesion. B and C, Postoperative radiographs after root canal preparation and obturation. Note the lateral canal in the coronal third of the root canal. D and E, Two-month recall radiograph suggests rapid healing. (Courtesy Dr. H. Walsch.)






To date, many treatment modalities, including nickel-titanium (NiTi) rotary instruments, have not been shown to have a statistically relevant impact on treatment outcomes.200 This poses a real problem in the age of evidence-based therapy, because a new therapeutic technique should provide a better result than standard procedures in clinical tests. The small number of relevant prospective clinical studies is only partly offset by numerous in vitro experiments. This chapter includes pertinent information from such studies, as well as results from our own experiments, because rotary nickel-titanium instruments have become widely used adjuncts in root canal treatment.

Pathophysiology of Endodontic Disease




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Many prospective and perioperative factors have been suggested as links to favorable treatment outcomes in endodontic therapy. Such factors include the patient's age and gender, the position of the tooth in the arch, extension of the root canal filling, and the use of certain interappointment dressings, such as calcium hydroxide Ca(OH)2. The presence of a periradicular osseous lesion (i.e., "apical periodontitis") appears to be a relevant prognostic factor that reduces the likelihood of a favorable outcome for root canal treatment; however, lesion size by itself is not an indication for endodontic surgery (see Chapter 20). Fig. 9-4 shows two cases in which large osseous lesions were treated by orthograde approaches; at recall appointments, the teeth were asymptomatic, and a reduction in lesion size was evident in both cases.




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Figure 9-3 Root canal treatment in a case with unusual and complicated anatomy. A, Preoperative radiograph of tooth #7 in a 12-year-old boy shows a substantial periradicular lesion and evidence of additional radicular anatomy (i.e., a dens-in-dente type II according to Oehlers' classification).187 B, Working length radiograph shows three separate root canals. C, Posttreatment radiograph months after shaping of the root canal systems with a nickel-titanium rotary system aided by ultrasonically activated K-files and dressing with calcium hydroxide four times for about 2 weeks each. Note the substantial periradicular bone fill. D, One-year recall radiograph shows evidence of periradicular healing. E, Two-year recall radiograph shows sound periradicular tissues.






Some may question whether lesions such as the ones in Fig. 9-4 are in fact cysts. Several studies have demonstrated that lesion size shows little correlation with the incidence of radicular cysts34,151,181,184; only histologic examination can prove whether a radiolucency is in fact a cyst. True cysts are believed to heal only after surgical enucleation,183 whereas the noncystic majority of apical processes heal predictably by orthograde endodontic treatment without surgery. An orthograde approach, therefore, appears to be beneficial in clinically asymptomatic cases and should include recall appointments at appropriate intervals (see Chapter 24).




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If clinical symptoms persist or begin after endodontic therapy, surgery may be performed in addition to orthograde root canal treatment. In the case shown in Fig. 9-5, a large lesion that extended into the maxillary sinus and nasal cavity was treated surgically 1 week after orthograde therapy of teeth #7 and #8, which included removal of two instrument fragments. The lesion was completely enucleated during surgery, and a tissue biopsy specimen was submitted for histologic processing; the lesion was diagnosed as a radicular cyst. As expected in this case, the patient reported discomfort after surgery. This supports the preference for a nonsurgical approach whenever possible.




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When root canal therapy is part of a comprehensive treatment plan, a favorable outcome for the root canal portion is a prime requirement. Extended bridgework and removable dentures depend on healthy periradicular tissues, just as they depend on healthy marginal and apical periodontal tissues. Fig. 9-6 presents a case in which a removable denture seemed unavoidable at the first examination. After extractions and root canal therapy were performed, small-unit, fixed partial dentures were placed. These reconstructions remain fully functional and allow this patient to benefit from the natural dentition.




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Figure 9-4 Potential of root canal treatment in cases of substantial periradicular destruction. A, Preoperative radiograph of teeth #8 and #9 shows a large lesion. Neither tooth responded to cold tests. B, Two-year followup radiograph shows bone fill. The canals were shaped with rotary and hand instruments, and obturation was performed using laterally compacted gutta-percha with AH Plus as the sealer. C, Preoperative radiograph of tooth #4, which has a previously filled root canal; a large periradicular lesion and insufficient obturation can be seen. D, Two-year postoperative radiograph shows evidence of bony healing after nonsurgical retreatment. (A and B courtesy Dr. M. Zehnder; C and D courtesy Dr. F. Paqué.)





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