Methods and models to study irrigation

The success of endodontic treatment depends on the eradication of microbes from the root canal system and prevention of reinfection. The factors that remain a challenge in the irrigation and disinfection of the root canal include biofilm resistance, poor penetration of the irrigant, and exchange of irrigants in the highly complex root canal anatomy. Progress in the search for better irrigants and irrigant delivery is necessary. A variety of different study models have been used in endodontic research on irrigation. In this article, the various models are discussed in light of relevant literature.     

A review of instrumentation kinematics of engine‐driven nickel–titanium instruments

Over the years, NiTi alloys have become indispensable materials in endodontic treatment. With technological advancements in metallurgy, manufacturers have attempted to produce instruments with enhanced features. In parallel with these developments, endodontic motors have undergone improvements in terms of torque control and kinematics that are adjustable in different directions. This review presents an overview of the advancements in instrumentation kinematics and the effect of instrumentation kinematics on root canal shaping procedures and instrument performance. The literature search for this narrative review was conducted in Google Scholar, Scopus, PubMed and Web of Science using the keywords ‘kinematics and endodontics’ and ‘reciprocation and endodontics’. In addition, historical literature was searched using the keyword ‘nickel–titanium and endodontics’. Overall, 143 articles were included up to 2015.     

The properties and applications of chlorhexidine in endodontics

Microorganisms and their by‐products are considered to be the major cause of pulp and periradicular pathosis. Hence, a major objective in root canal treatment is to disinfect the entire root canal system, which requires that all contents of the root canal system be eliminated as possible sources of infection. This goal may be accomplished using mechanical instrumentation and chemical irrigation, in conjunction with medication of the root canal system between treatment sessions. To reduce or eliminate bacteria, various irrigation solutions have been advocated. Chlorhexidine is a cationic molecule, which can be used during treatment. It has a wide range of antimicrobial activity. Its cationic structure provides a unique property named substantivity. The purpose of this paper is to review the structure and mechanism of action of CHX, its antibacterial and antifungal activity, its effect on biofilm, its substantivity (residual antibacterial activity), its tissue solvent ability, its interaction with calcium hydroxide and sodium hypochlorite, its anticollagenolytic activity, its effect on coronal and apical leakage of bacteria, its toxicity and allergenicity and the modulating effect of dentine and root canal components on its antimicrobial activity. A Medline search was performed from 1981 to the end of March 2008 and was limited to English‐language papers. The keywords searched on Medline were ‘chlorhexidine AND endodontics’, ‘chlorhexidine AND root canal therapy’, ‘chlorhexidine AND substantivity’ and ‘chlorhexidine AND toxicity’. The reference lists of each article were manually checked for additional articles of relevance.     

Endosonics – The ultrasonic synergistic system of endodontics

Abstract Endosonics is an ultrasonic synergistic system of root canal instrumentation and disinfection. Specially made endosonic dies and diamond instruments are energized by means of a Cavitron ultrasound generator (above 20 kHz frequency). An endosonic insert is designed to allow the traditional endodontic irrigant, sodium hypochlorite, to pass through and along the endo-sonic files. The irrigant is activated by the ultrasonic energy imparted from the energized instruments and the root canal becomes an ultrasonic bath. Thus, endosonics is a synergistic system. The ultrasonic energy makes the files vibrate and oscillate, facilitating the instrumentation of the root canal and, in addition, activates the irrigant for canal disinfection.     

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??Root canal debridement and infection control are two of the main steps in root canal therapy. Bacteria will be present as biofilm colonies inside the root canal??and it will be well within fins??intercanal anastomoses??apical ramification??apical furcation or lateral accessory canal. Meanwhile??during the cleaning and shaping process??smear layer can be produced??which can be used for the viable bacteria inside the complex anatomical structure to sustain growth and activity. In addition??due to the complexity of the root canal system??the conventional irrigation and disinfection technology is superficial??then the smear layer and Enterococcus faecalis biofilms are difficult to remove. In recent years??lasers??as a novel adjuncting irrigation tool??are used clinically??such as Er??YAG laser and Er??Cr??YSGG laser. As is reported??laser-activated irrigations can effectively remove the smear layer and the infection and obtain better disinfection rates. So in this a review??we made a summary of the effect of laser-activated irrigations on endodontics.     

激光活化荡洗在根管治疗中的作用

根管清理和感染控制是根管治疗的两个重要步骤。在根管内细菌以生物膜的形式存在,其可隐藏在根管峡部、根尖分歧、根尖分叉、侧枝根管等复杂的解剖结构中;同时,在根管预备过程中可产生玷污层,玷污层能为细菌的生长繁殖提供基质,其也可附着于上述复杂的解剖结构中。由于根管系统的复杂性,难以通过常规的冲洗消毒方法彻底清除菌斑生物膜,近年来激光作为一种新型的辅助冲洗消毒的工具逐渐应用于临床,最为常用的是铒激光（Er∶YAG和Er,Cr∶YSGG激光）,研究报道激光辅助根管荡洗可有效去除玷污层并清除根管内的感染,从而获得更好的消毒效果。文章就激光活化荡洗在根管治疗中的作用做一概述。     

Factors affecting irrigant extrusion during root canal irrigation: a systematic review

The aim of the present study was to conduct a systematic review and critical analysis of published data on irrigant extrusion to identify factors causing, affecting or predisposing to irrigant extrusion during root canal irrigation of human mature permanent teeth. An electronic search was conducted in Cochrane Library, LILACS, PubMed, SciELO, Scopus and Web of Knowledge using a combination of the terms ‘irrigant’, ‘rinse’, ‘extrusion’, ‘injection’, ‘complication’, ‘accident’, ‘iatrogenic’, ‘root canal’, ‘tooth’ and ‘endodontic’. Additional studies were identified by hand‐searching of six endodontic journals and the relevant chapters of four endodontic textbooks, resulting in a total of 460 titles. No language restriction was imposed. After applying screening and strict eligibility criteria by two independent reviewers, 40 case reports and 10 ex vivo studies were included in the review. A lack of clinical studies focusing on irrigant extrusion during root canal irrigation was evident. The reviewed case reports focused mainly on the clinical manifestations and management of the accidents and did not provide adequate details on the possible factors that may influence irrigant extrusion. The data from the included ex vivo studies were inconclusive due to major methodological limitations, such as not simulating the presence of periapical tissues and not assessing the validity of irrigant detection methods. The extensive variability in the protocols employed hindered quantitative synthesis. The choice of factors investigated in ex vivo studies seems not to have been driven by the available clinical evidence. These issues need to be addressed in future studies.     

Irrigation dynamics associated with positive pressure,apical negative pressure and passive ultrasonic irrigations: A computational fluid dynamics analysis

Complexities in root canal anatomy and surface adherent biofilm structures remain as challenges in endodontic disinfection. The ability of an irrigant to penetrate into the apical region of a canal, along with its interaction with the root canal walls, will aid in endodontic disinfection. The aim of this study was to qualitatively examine the irrigation dynamics of syringe irrigation with different needle tip designs (open‐ended and closed‐ended), apical negative pressure irrigation with the EndoVac® system, and passive ultrasonic‐assisted irrigation, using a computational fluid dynamics model. Syringe‐based irrigation with a side‐vented needle showed a higher wall shear stress than the open‐ended but was localised to a small region of the canal wall. The apical negative pressure mode of irrigation generated the lowest wall shear stress, while the passive‐ultrasonic irrigation group showed the highest wall shear stress along with the greatest magnitude of velocity.     

Passive ultrasonic irrigation of the root canal: a review of the literature

Ultrasonic irrigation of the root canal can be performed with or without simultaneous ultrasonic instrumentation. When canal shaping is not undertaken the term passive ultrasonic irrigation (PUI) can be used to describe the technique. In this paper the relevant literature on PUI is reviewed from a MEDLINE database search. Passive ultrasonic irrigation can be performed with a small file or smooth wire (size 10-20) oscillating freely in the root canal to induce powerful acoustic microstreaming. PUI can be an important supplement for cleaning the root canal system and, compared with traditional syringe irrigation, it removes more organic tissue, planktonic bacteria and dentine debris from the root canal. PUI is more efficient in cleaning canals than ultrasonic irrigation with simultaneous ultrasonic instrumentation. PUI can be effective in curved canals and a smooth wire can be as effective as a cutting K-file. The taper and the diameter of the root canal were found to be important parameters in determining the efficacies of dentine debris removal. Irrigation with sodium hypochlorite is more effective than with water and ultrasonic irrigation is more effective than sonic irrigation in the removal of dentine debris from the root canal. The role of cavitation during PUI remains inconclusive. No detailed information is available on the influence of the irrigation time, the volume of the irrigant, the penetration depth of the instrument and the shape and material properties of the instrument. The influence of irrigation frequency and intensity on the streaming pattern as well as the complicated interaction of acoustic streaming with the adherent biofilm needs to be clarified to reveal the underlying physical mechanisms of PUI.     

Photodynamic therapy: An adjunct to conventional root canal disinfection strategies

Although chemical‐based root canal disinfectants are important to reduce microbial loads and remove infected smear layer from root dentin, they have only a limited ability to eliminate biofilm bacteria, especially from root complexities. This paper explores the novel photodynamic therapy (PDT) for antimicrobial disinfection of root canals. The combination of an effective photosensitizer, the appropriate wavelength of light and ambient oxygen is the key factor in PDT. PDT uses a specific wavelength of light to activate a non‐toxic dye (photosensitizer), leading to the formation of reactive oxygen species. These reactive oxygen molecules can damage bacterial proteins, membrane lipids and nucleic acids, which promote bacterial cell death. In, addition PDT may enhance cross‐linking of collagen fibrils in the dentin matrix and thereby improving dentin stability. The concept of PDT is plausible and could foster new therapy concepts for endodontics. The available knowledge should enable and encourage steps forward into more clinical‐oriented research and development. This article discusses PDT as related to root canal disinfection, including its components, mechanism of action, reviews the current endodontic literature and also highlights the shortcomings and advancements in PDT techniques.     

A big role for the very small—understanding the endodontic microbial flora

Apical periodontitis, an inflammatory process around the apex of a tooth root, is primarily a sequel to microbial infection of the pulp space. The microbial flora is composed of a restricted group of the total oral flora, selected by environmental pressures of anaerobiosis, nutrition and competition with other species and inhabits the root canal as a biofilm of coaggregated communities in an extracellular matrix. The untreated infected canal is generally composed of a polymicrobial mix with approximately equal proportions of Gram-positive and Gram-negative species, dominated by obligate anaerobes.
The type of microbial flora in the root-filled tooth with persistent apical periodontitis has very different characteristics. These infections are characterized by one or just a few species, predominantly Gram-positive micro-organisms with an equal distribution of facultative and obligate anaerobes. Enterococcus faecalis has been a conspicuous finding in most studies.
Because the primary aetiological problem is infection, endodontic treatment is directed at control and elimination of the root canal flora by working in a sterile way. Based on current knowledge, the best available method for obtaining clean, microbe-free root canals is by instrumentation with antimicrobial irrigation reinforced by an intracanal dressing with calcium hydroxide.     

Laser applications in endodontics: an update review

The search for new devices and technologies for endodontic procedures always has been challenging. Since the development of the ruby laser by Maiman in 1960 and the application of the laser for endodontics by Weichman in 1971, a variety of potential applications for lasers in endodontics have been proposed. With the development of thinner, more flexible and durable laser fibres, laser applications in endodontics have increased. Since laser devices are still relatively costly, access to them is limited. The purpose of this paper is to summarise laser applications in endodontics, including their use in pulp diagnosis, dentinal hypersensitivity, pulp capping and pulpotomy, sterilisation of root canals, root canal shaping and obturation and apicectomy. The effects of lasers on root canal walls and periodontal tissues are also reviewed.     

氢氧化钙糊剂与根管内感染控制

感染控制对根管治疗的成功至关重要。尽管随着器械及设备的进步，对根管的清理及成形取得了很大的进展；然而，由于根管系统解剖结构错综复杂，使得获取清洁根管面临各种问题。例如：机械预备的宽度有限，不能彻底清理感染牙本质；冲洗技术的运用虽然可以去除根管器械预备后形成的玷污层，但对细菌内毒素的清除还是难以达到理想的效果，而残留的微生物、毒素等若得不到清除可能会在根尖周组织形成持续感染。因此，除外机械预备和冲洗，根管封药也是感染根管治疗过程中的重要步骤。氢氧化钙糊剂以其高效的抗菌作用在临床得到广泛使用。文章将对根管封药的必要性、氢氧化钙的作用机制及临床应用做一介绍。     

Review of ultrasonic irrigation in endodontics: increasing action of irrigating solutions

Introduction: Effective irrigant delivery and agitation are prerequisites for successful endodontic treatment. Ultrasonic irrigation can be performed with or without simultaneous ultrasonic instrumentation. Existing literature reveals that ultrasonic irrigation may have a very positive effect on chemical, biological and physical debridement of the root canal system as investigated in many in vitro studies. Objective: The purpose of this review article was to summarize and discuss the available information concerning ultrasonic irrigation in endodontics. Methods: This article presents an overview of ultrasonic irrigation methods and their debridement efficacy. In this paper the relevant literature on passive ultrasonic irrigation is reviewed. Information from original scientific papers or reviews listed in MEDLINE and Cochrane were included in the review. Results: The use of ultrasound in the irrigation procedure results in improved canal cleanliness, better irrigant transfer to the canal system, soft tissue debridement, and removal of smear layer and bacteria. There are many in vitro studies, but there is a need to standardize protocols, and correlate the clinical efficacy of ultrasonic devices with improved treatment outcomes. Understanding the basis of ultrasonic irrigation is fundamental for clinicians and researchers to improve the design and use of ultrasonic irrigation. Key words:Ultrasonic irrigation, ultrasound, smear layer, endodontics.     

根管系统内管间峡区的研究进展

根管管间峡区是同一牙根内、两根管间，含有牙髓或牙髓生成组织的一种狭窄带状结构。常规根管治疗难以对根管管间峡区进行机械清理、成形及充填，可因管间峡区的存在而最终导致治疗失败。对根管管间峡区的诊断和治疗，是牙髓外科手术成功的关键。牙科手术显微镜、内镜等先进设备的引进有助于提高根管管间峡区的诊断精确度和治疗成功率。     

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提要：产黑色素类杆菌是感染根管内的优势菌，与自发性疼痛、脓肿、根管内恶臭等牙髓病和根尖周病的临床症状关系密切。有效地去除产黑色素类杆菌对治疗牙髓病和根尖周病具有重要意义。本文从几种临床根管消毒方法对产黑色素类杆菌抑菌作用方面进行综述。     

Final Endodontic Irrigation with 70% Ethanol Enhanced Calcium Hydroxide Removal from the Apical Third

IntroductionThe purpose of this study was to evaluate the cleanliness of root canal walls and dentinal tubules after attempting to remove the calcium hydroxide dressing with different irrigant solutions and the use of nonactivated irrigation or passive ultrasonic irrigation (PUI).MethodsAfter root canal instrumentation, 80 single-rooted teeth were filled with calcium hydroxide mixed with propylene glycol and 0.1% rhodamine B dye and inserted into canals with a Lentulo spiral. The calcium hydroxide dressing was initially removed with 10 mL saline solution and reinstrumentation with the master apical file. Then, the samples were randomly assigned into 8 experimental groups (n = 10) according to the irrigant solution with or without PUI: 2.5% sodium hypochlorite, 17% ethylenediaminetetraacetic acid + 1.25% sodium lauryl ether sulfate (EDTA-T), 37% phosphoric acid, or 70% ethanol. A final flush with 5 mL saline solution was performed. The percentage of clean root canal walls and the depth of clean dentinal tubules were measured with images of confocal laser scanning microscopy. The groups were compared using the 2-way analysis of variance test with the Bonferroni post hoc test for depth analysis and the Kruskal-Wallis with Dunn post hoc test for the perimeter analysis.ResultsIrrigation with 70% ethanol presented a significantly higher percentage of clean root canal walls and a higher depth of clean dentinal tubules when compared with irrigation with 2.5% sodium hypochlorite and 17% EDTA-T for both irrigation methods (P < .05). No differences were observed between nonactivated irrigation or PUI protocols (P > .05).ConclusionsSeventy percent ethanol enhanced calcium hydroxide removal from the apical root third compared with 2.5% sodium hypochlorite or 17% EDTA-T.     

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在过去的20多年里，牙科领域在技术方法、材料和设备上有许多令人鼓舞的进展。牙体牙髓专业也同样有很多革命性突破。根管治疗是牙体牙髓的最基本操作，治疗时的照明和放大是两个最关键的影响因素。牙科显微镜的应用使根管治疗进入了精细时代。本文对牙科显微镜的发展及在牙体牙髓领域的应用做了较为详尽的介绍。     

Laser-activated irrigation within root canals: cleaning efficacy and flow visualization

Aim  To test ex vivo the efficiency of laser-activated irrigation in removing dentine debris from the apical part of the root canal and to visualize in vitro the fluid dynamics during the activation of the irrigant by laser, using high-speed imaging at a relevant timescale.
Methodology  Root canals with a standardized groove in one canal wall filled with dentine debris were irrigated with syringe irrigation, ultrasonically or laser-activated irrigation (LAI) using 2% sodium hypochlorite as irrigant. The quantity of dentine debris after irrigation was determined. Visualization of the fluid dynamics during activation was achieved using a high-speed camera and a glass model.
Results  Laser-activated irrigation was significantly more effective in removing dentine debris from the apical part of the root canal than passive ultrasonic irrigation or hand irrigation when the irrigant was activated for 20 s.
Conclusions  The in vitro recordings suggest that streaming, caused by the collapse of the laser-induced bubble, is the main cleaning mechanism of LAI.     

Complete Healing of a Large Cystic Lesion Following Root Canal Treatment with Concurrent Surgical Drainage: A Case Report with 14-Year Follow-Up

We describe complete healing of an extensive cystic lesion by using a conservative approach: root canal treatment with concurrent surgical drainage. A silicone Foley catheter drain was modified into a surgical drainage stent, which was then used for 4 weeks. Disinfection of the root canal was achieved by the use of hand files and irrigation with 5.25% NaOCl for a minimum of 30 minutes. The irrigant changes were performed at 5-minute intervals, and no intracanal dressing was used. At subsequent follow-up examinations, cone-beam computed tomography and periapical radiographs confirmed that complete healing had occurred around the periapical and lateral areas of affected teeth. This case report indicates the potential for healing of large cystic lesions by nonsurgical root canal treatment.