Oct 10, 2004 ... Introduction. Endodontics is the branch of dentistry concerned with the ... In
recent years, advances have been made in various aspects of ...
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Recent Advances in Endodontics Dr Robert PY Ng BDS, MSc, MClinDent, MRD RCSEd, AdvDipEndodont, FRACDS, LDS RCSEng Assistant Professor, Faculty of Dentistry, The University of Hong Kong
Dr Robert PY Ng
Introduction Endodontics is the branch of dentistry concerned with the aetiology, prevention, diagnosis and treatment of diseases and injuries that affect the dental pulp, tooth root and periradicular tissues.1 At the beginning of the last century, focal infection theory had severely threatened the existence of the discipline. Since then, the issue of focal infection has reappeared and become a concern in dentistry, but a definite causal effect has not been shown.2 In recent years, advances have been made in various aspects of endodontics, from diagnosis to treatment. This has been made possible mainly by a better understanding of the pathophysiology of the pulp and periradicular tissues and the emergence of new technologies.
Diagnosis of Pulpal/Periradicular Diseases Diagnosis of pulpal and periradicular diseases has been made difficult due to the inaccessibility of the diseased tissues for direct inspection. Indirect signs, such as radiographic findings, presence of pain and swelling, have been used to aid in the diagnostic process. However, it has been shown that the correlation between pulpal inflammation and pain is poor3 and the radiograph is not a very sensitive tool in detecting minor changes in the periradicular tissues.4 The various methods of testing pulp sensibility each have their own drawbacks. It has been suggested that by sampling pulpal fluids to detect certain inflammatory markers, the pulpal status could be determined more accurately.5 Hopefully, this would differentiate between reversible and irreversible pulpitis and thereby allowing the selection of the correct treatment modality either to preserve or to extirpate the inflamed pulp. It is important, especially in cases of trauma, to determine whether the dental pulp has retained its blood supply. Traditionally, this has been inferred by testing the sensibility of the dental pulp but errors could occur. With the advent of laser Doppler flowmetry (LDF), the blood supply in a tooth could be assessed and its vitality determined accurately. Due to a possible loss of nerve supply in traumatised teeth, LDF is useful as a tool to monitor the vitality and recovery of such teeth from trauma.6
Prevention of Pulpal Diseases Although caries and restorative procedures could cause pulpal inflammation, the predominant cause of pulpal inflammation is microbial microleakage.7 Much effort has
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been used to improve the properties of dental materials in order to control microleakage. These improved materials are used to reduce the gap at the restorationcavity wall interface or to coat exposed dentine surface. However, during function, a tooth would deform, the physical barrier formed by these materials would break down as they could not deform to the same degree as the tooth. Until this stumbling block is overcome, it is unlikely that any dental materials could achieve a total and permanent seal against microleakage. From a biological perspective, adherence of bacteria to exposed tooth surfaces is a prerequisite to establishment of bacterial colonies and biofilms leading to subsequent microleakage. It is likely that research into preventing bacterial adherence onto tooth surfaces would provide the answer to microbial microleakage
Treatment of Exposed Pulp The outcome of direct pulp capping depends on the presence of a healthy pulp, asepsis as well as the absence of microbial microleakage. Traditionally, calcium hydroxide had been the material of choice as a direct pulp capping agent. Recently, adhesive materials have been suggested as a replacement for calcium hydroxide, but the reported results have been equivocal.8,9 A recently introduced material - mineral trioxide aggregate (MTA), has been shown to be highly biocompatible.10 MTA is capable of stimulating dentine bridge formation adjacent to the exposed dental pulp. Direct pulp capping with MTA has been reported to result in less inflammation, hyperaemia, necrosis and thicker dentinal bridges and more frequent odontoblastic layer formation with MTA than calcium hydroxide. Apart from direct pulp capping, MTA is also suitable for repair of root perforation, obturation of incompletely formed roots and as a root end filling material.11
Root Canal Treatment The process of root canal treatment aims to remove microorganisms, organic and inorganic debris from the root canal system by mechanical instrumentation with files and chemical disinfection with irrigating solutions and intra-canal medicaments. Given the complexity of the root canals, preparation of the root canals is fraught with difficulties and iatrogenic problems are not uncommon. One of the common obstacles faced by the operator in root canal treatment is the location of the root canals. In teeth
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with large deposits of reparative dentine and sclerotic canals, location of the root canal orifices could be problematic. Naturally, a thorough knowledge of root canal anatomy and fine tactile sense are essential. However, with the help of good magnification and illumination provided by an operating microscope, in experienced hands, location of root canals could be made easier.12 In addition, using a microscope, with the help of a suitable dye, minute crack lines could be more easily identified.12 Apart from helping to locate canals, an operating microscope (or some other form of magnification) is invaluable in endodontic retreatment.12 With its enhanced vision and lighting, an operator could carry out various procedures, such as bypassing or removing separated instruments, negotiation of ledged canals, repair of root canal perforations and placement of materials such as MTA, more efficiently. A new breed of endodontic files, made from a nickeltitanium (Ni-Ti) alloy, has been introduced. The Ni-Ti alloy has the desirable property of superelasticity, which makes endodontic files made of this alloy very flexible. These files are able to prepare curved canals concentrically and reduce the incidence of iatrogenic errors13, with comparable ability to remove intra-canal bacteria as stainless steel hand files.14 Furthermore, because of its flexibility, the files could be manufactured with an increased taper and potentially could enable the operator to complete root canal preparation with less time and effort. In an ideal world, in order to preserve the maximal amount of tooth substance after endodontic therapy, its root canals should not be mechanically prepared but cleaned thoroughly with irrigants. A group of researchers in Switzerland has pioneered a method called the Noninstrumentation Technique, using a partial vacuum system to deliver the irrigant into the root canal system.15 This could be a potentially useful system but at present, is still regarded as experimental. Various alternative methods to enhance disinfection of root canals have been introduced recently. Photo-activated disinfection (PAD) is a process whereby microorgansisms are sensitised by a photoactive agent, tolonium chloride. When the agent is stimulated by a light of an appropriate wavelength, radicals are released and bacteria are ruptured.16 Ozone gas is a powerful oxidative agent and is potently bactericidal.17 For endodontic purposes, it has been suggested that ozonated oil should be used instead, although there has been no reports on its efficacy. Ozonated oil has been claimed to be equally bactericidal and has a long shelf life. Numerous types of lasers are available and some of them such as, Er:YAG, Er,Cr:YSSG and Ho:YAG, appear to be promising in root canal preparation.18 These types of laser have been touted by their manufacturers as replacement of traditional root canal files but further development and scientific proof of their efficacy are required. Cold lateral condensation of gutta-percha with sealer is the most widely used root canal obturation technique practised by dentists. The technique is easily mastered and requires little ancillary equipment. However, it has been shown in leakage studies that the apical seal produced by cold lateral condensation is far from ideal.19 Various thermoplasticised
Dental Bulletin gutta-percha techniques have been reported to produce a better apical seal 19 and it has been shown that the same technique could fill a higher percentage of lateral canals.20 However, to some researchers, gutta-percha is not the ideal root canal obturation as potentially a path for leakage is always present between the canal wall and the obturation material.21 A resin-based obturation material has recently been introduced to eliminate this weak link. By bonding the obturation material to the root canal wall, a monobloc of root dentine and composite resin would be formed and minimise microleakage.21
Surgical endodontics When a patient does not wish to undergo non-surgical endodontic retreatment or when the procedure is not indicated, then surgical endodontics should be considered in order to preserve the tooth. The use of an operating microscope and miniaturised ultrasonic tips and hand instruments has revolutionised surgical endodontics.22 An operating microscope provides co-axial lighting and a range of magnification from x 5 to x 30. This will enable the operator to examine the apical region of a root for crack lines and the resected root end for presence of any accessory anatomical features such as fins or isthmuses between root canals.22 Using specially designed miniaturised ultrasonic tips to prepare the root end cavities enables the operator to perform root resection at approximately right angle to the long axis of the root, as opposed to a forty-five degrees root resection in earlier days.22 Some of the advantages of this modern approach are minimising the risk of iatrogenic errors, reducing the number of exposed dentinal tubules and preservation of root dentine. MTA was originally tested as a root end filling material before its wider applications in endodontics, such as direct pulp capping, were recognised. MTA has been shown to promote deposition of cementum on its surface and to be perfectly compatible with the periapical tissues 23 . Compared to other root end filling materials with a longer history of use, such as amalgam, IRM or Super EBA cement, little or no inflammatory cells could be detected in the vicinity of MTA but the same cells would be present around the older materials in greater quantity.23 However, the handling properties of MTA are not as user friendly as the other materials and its use would require some practice.
Conclusion There have been advances in all aspects of endodontics, which allow the operator to provide high quality endodontic treatment. Regardless of whether the treatment is preservation of the exposed pulp, first time root canal treatment, root canal retreatment or surgical endodontics, the key to success is still the attainment of sterility within the root canal system.24 Unless this is achieved, endodontic treatment is likely to fail, despite all the new equipment and technology at our disposal. Moreover, it is interesting to note that the success rates of first time root canal treatment and root canal retreatment reported in the literature have not changed significantly since the second half of the last century.24 THE HONG KONG
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Dental Bulletin References 1 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
European Society of Endodontology. Consensus report of the European Society of Endodontology on quality guidelines for endodontic treatment. Int Endod J 1994; 27: 115-124. Slots J. Casual or causal relationship between periodontal infection and non-oral disease? J Dent Res 1998; 77: 1764-1765. Seltzer S, Bender IB, Zionitz M. The dynamics of pulp inflammation: correlations between diagnostic data and actual histologic findings in the pulp. Oral Surg Oral Med Oral Pathol 1963; 16: 846-871. Bender IB, Seltzer S. Roentgenographic and direct observation of experimental lesions in bone: I. Oral Surg Oral Med Oral Pathol 1961; 27: 152-160. Gulabivala K. Advances in endodontics. Prim Dent Care 2000; 7: 105-107. Emshoff R, Moshen I, Strobl H. Use of laser Doppler flowmetry to predict vitality of luxated or avulsed permanent teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004 (In press). Brown e RM, Tobias RS. Microbial microleakage an d pulpal inflammation: a review. Endod Dent Traumatol 1986; 2: 177-183. Pameijer CH, Stanley HR. The disastrous effect of the ‘total etch’technique in vital pulp capping in primates. Am J Dent 1998; 11: S45-S54. Cox CF, Hafez AA, Akimoto N, Otsuki M, Suzuki S, Tarim B. Biocompatibility of primer, adhesive and resin composite on non-exposed and exposed puls of non-human primate teeth. Am J Dent 1998; 11: S55-S63. Koh ET, McDonald F, Pitt Ford TR, Torabinejad M. Cellular response to mineral trioxide aggregate. J Endod 1998; 24: 543-547. Torabinejad M, Chivian N. Clinical applications of mineral trioxide aggregate. J Endod 1999; 25: 197-205. Carr GB. Microscopes in endodontics. J Calif Dent Assoc; 20: 55-61. Pettiette MT, Metzger Z, Phillips C, Trope M. Endodontic complications of root canal therapy performed by dental students with stainless steel K-files and nickel-titanium hand files. J Endod 1999; 25: 230-234.
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14. Dalton BC, Ø rstavik D, Phillips C, Pettiette M, Trope M. Bacterial reduction with nickel-titanium rotary instrumentation. J Endod 1998; 24: 763-767. 15. Lussi A, Nussbächer U, Grosrey J. A novel non-instrumented technique for cleansing the root canal system. J Endod 1993; 19: 237-241. 16. Seal GJ, Ng Y-L, Spratt D, Bhatti M, Gulabivala K. An in vitro comparison of the bactericidal efficacy of lethal photosensitization or sodium hypochlorite irrigation on Streptococcus intermedius biofilms in root canals. Int Endod J 2002; 35: 268-274. 17. Baysan A, Lynch E. Effect of ozone on the oral microbiota and clinical severity of primary root caries. Am J Dent 2004; 17: 56-60. 18. Kimura Y, Wilder-Smith P, Matsumoto K. Lasers in endodontics: a review. Int Endod J 2000; 33: 173-185. 19. Gulabivala K, Holt R, Long B. An in vitro comparison of thermoplasticised gutta-percha obturation techniques with cold lateral condensation. Endod Dent Traumatol 1998; 14: 262-269. 20. Goldberg F, Artaza LP, De Silvio A. Effectiven ess of different obturation techniques in the filling of simulated lateral canals. J Endod 2001; 27: 362-364. 21. Shipper G, Ø rstavik D, Teixeira FB, Trope M. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (Resilon). J Endod 2004; 30: 342-347. 22. Rubinstein RA, Kim S. Short-term observation of the results of endodontic surgery with the use of a surgical operating microscope and Super-EBA as root-end filling material. J Endod 1999; 25: 43-48. 23. Torabinejad M, Pitt Ford TR, McKendry DJ, Abedi HR, Miller DA, Kariyawasam SP. Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys. J Endod 1997; 23: 225-228. 24. Friedman S. Chapter 15: Treatmen t outcome and prognosis of endodontic therapy. In: Essential Endodontology. Ø rstavik D, Pitt Ford TR (eds), Blackwell Science Ltd. 1998: 367-401.
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