springer series on biofilms: vol. 9 - the root canal biofilm

The Root Canal Biofilm

Springer Series on Biofilms

Luis E. Chávez de PazChristine M. SedgleyAnil Kishen Editors

Springer Series on BiofilmsLuis E. Chávez de Paz – Christine Sedgley – Anil Kishen EditorsThe Root Canal Biofilm

This book presents the current state of research on the basic scientific aspects of root canal biofilm biology within a clinically applicable context. Root canal biofilms are complex polymicrobial structures adhering to the root canal surface that are formed by microorganisms invading the pulpal space of teeth, and are associated with persistent root canal infections. Concerted efforts to study root canal biofilms have been made in the past decade, resulting in the publication of observational and experimental studies that detail the morphology and biology of these structures in infected root canals. In addition to confirming that bacteria in root canals do not exist in free-floating planktonic states as previously assumed, this new information on root canal biofilm infections has provided an opportunity to re-evaluate conventional clinical protocols and improve endodontic therapeutic measures.


General Biological Aspects

Chapters 1-3

Part 1

Observational and Experimental Evidence

Chapters 4-7

Part 2

Outcome and Strategies of Treatment

Chapters 8-11

Part 3


Chapter 1 - Ecology and Physiology of Root Canal Microbial Biofilm CommunitiesLuis E. Chávez de Paz and Philip D. Marsh

Microbial communities formed in root canals of teeth constitute the heart of the infected root canal ecosystem, and yet their establishment and development remains challenging to measure and predict. Identifying the ecological and physiological drivers of microbial community colonization, including resistance (insensitivity to disturbance) and resilience (the rate of recovery after disturbance), is important for understanding their response to antimicrobial treatment. This chapter will provide an overview of the ecological and physiological factors that are relevant for root canal microbial communities in terms of their establishment and endurance in root canal ecosystems. Initially, insights from ecological and physiological parameters that are useful for defining and measuring activities in root canal biofilm communities will be reviewed. The ecological progress of root canal infections will be discussed in terms of three ecological processes: 1) selection of successful root canal colonizers by habitat filtering, 2) selection of resistant bacteria to major disturbances in the environment (e.g. provoked by antimicrobial therapy in endodontics) and 3) resilience of the community after the disturbance. Finally, current methods for analyzing these ecological processes will be described, as these are key elements for identifying the biological features of individual microorganisms and of root canal microbial communities.


Chapter 2 - Molecular Principles of Adhesion and Biofilm Formation Jens Kreth and Mark C. Herzberg

Oral bacteria are responsible for oral health and disease, including caries, periodontal disease and endodontic infections. The development of oral diseases is intimately linked with the ability of oral bacteria to form an adherent multispecies consortium named biofilm. The oral biofilm provides a protective environment for the bacterial population and its formation is a genetically controlled process. In this chapter, we present a general overview of developmental mechanisms employed by individual members of the oral biofilm. The species composition of the oral biofilm and the oral microbiome is discussed historically and in the context of newly developed next-generation sequencing techniques. Furthermore, biofilm-specific regulatory mechanisms and phenotypic traits are explained to provide the reader with a comprehensive overview of oral biofilm formation and its role in health and disease.


Chapter 3 - Antimicrobial Resistance in Biofilm Communities Christine Sedgley and Gary Dunny

Biofilms are composed of microcolonies encased in an extracellular polymeric substance (EPS) matrix. Wide-ranging differences exist between the biofilm and planktonic states in growth, structure, behavior, and physiology, all of which can have profound effects on their susceptibility to antimicrobials. Other factors that can contribute to the decreased susceptibility of biofilm microorganisms to antimicrobial agents include provision of a physical barrier to antimicrobial agents by the EPS matrix, facilitation of horizontal gene transfer of DNA trapped within the extracellular matrix, quorum sensing and stress responses resulting in the recruitment and expression of resistance determinants such as multidrug resistance efflux pumps, the presence of persister cells that survive antibiotic treatment, and metabolic heterogeneity throughout the biofilm resulting in slow growth and protection against antibiotics active on rapidly growing bacteria. While further work is needed to fully understand antimicrobial resistance in biofilm communities, including the multi-species biofilms found in root canal infections, the accumulative effects of various processes, rather than individual involvement, are likely to be important. It is clear that much remains to be learned about the critical events in the development of antimicrobial resistance in biofilm communities.


Chapter 4 - The Use of Scanning Electron Microscopy (SEM) in Visualizing the Root Canal Biofilm Linda Peters, Brandon Peterson, David E. Jaramillo and Luc van der Sluis

Apical periodontitis is caused by microorganisms in planktonic or biofilm state present in the root canal system and/or attached to the outer apical root surface. Knowledge about the microorganisms and biofilm structure within and external to the root canal system is important in order to effectively treat apical periodontitis. Scanning Electron Microscopy (SEM) has been used to visualize and morphologically describe the presence of biofilm and microorganisms associated with teeth with apical periodontitis. However, because of the high vacuum conditions associated with SEM procedures, hydrated structures such as the biofilm matrix are not readily visualized. In addition, the identification of specific microbial species is problematic without the utilization of a combination of different techniques. This chapter provides a short outline of the applications of SEM in endodontics with the intention to describe the benefits and shortcomings of this microscopic technique.


Chapter 5 - Bacterial Biofilms and Endodontic Disease: Histo-Bacteriological and Molecular Exploration José F. Siqueira Jr., Domenico Ricucci and Isabela N. Rôças

Recent evidence brought about by morphological studies have indicated that apical periodontitis is a disease caused by or at least highly associated with bacterial biofilms. Histobacteriological studies revealed that biofilm-like structures are the main form in which bacteria infecting the root canal system are organized. Bacterial biofilms can be found in virtually all areas of the root canal system, including the main canal, apical and lateral ramifications, isthmuses and recesses. Biofilms are very frequent in the apical part of root canals of teeth with primary or post-treatment apical periodontitis. Morphology of endodontic biofilms can vary from case to case and a unique pattern has not been established. Bacterial biofilms are expected to be even more prevalent in the root canals of teeth associated with longstanding pathologic processes, including large apical radiolucencies and cysts. The bacterial diversity associated with endodontic biofilms is broader than previously anticipated, and several culture-difficult or as-yet-uncultivated bacteria can participate in these communities. The clinician should be aware that, when performing root canal treatment or retreatment, s/he is dealing with a biofilm infection, which may be very difficult to reach and eradicate, and may require special strategies for successful management.


Chapter 6 - Laboratory Models of Biofilms: Development and Assessment Anil Kishen and Markus Haapasalo

Microbial-biofilms are surface-adherent consortiums formed by microbes in response to environmental influences. Currently, there are several reports on the existence of bacterial biofilms in infected root canal systems. Consequently it is mandatory to simulate such biofilm modes of bacterial growth in laboratory models for applied microbiological experiments pertaining to endodontics. This chapter covers different considerations for developing biofilm models in endodontics. In addition, different types of in vitro root canal biofilm models and the methods of assessments are described in this chapter.


Chapter 7 - Root Canal Anatomy: Implications in Biofilm Disinfection Marco A. Versiani and Ronald Ordinola-Zapata

The primary goals of endodontic treatment are to debride and disinfect the root canal space to the greatest possible extent, and to seal the root canal system as effectively as possible, aiming to establish or maintain healthy periapical tissues. Treating complex and anomalous anatomy requires knowledge of the internal anatomy of all types of teeth before undertaking endodontic therapy. Recently, three-dimensional imaging of teeth using micro-computed tomography has been used to reveal the internal anatomy of teeth to the clinician bringing new perspectives on the overall quality of the endodontic treatment, confirming the inability of shaping tools in acting within the anatomical complexity of the root canal. Besides, the disinfecting effects of instruments and irrigants may be additionally hampered in the presence of complex anatomy such as accessory canals, ramifications, intercanal connections, fins, isthmuses, and apical deltas, which cannot be properly accessed and cleaned by conventional techniques. These hard-to-reach areas may also be packed with dentin debris generated and pushed therein by endodontic instruments, interfering with disinfection by both preventing the irrigant flow into them as well as by neutralizing its efficacy. This chapter is focused on the complexity of root canal anatomy and discusses its relationship on the understanding of the principles and problems of cleaning procedures.


Chapter 8 - Biofilm-Associated Infections in Root Canals Treatment and Outcomes Kishor Gulabivala and Y-L Ng

Root canal infections are essentially characterized by microbial biofilms that adhere to the root canal dentine and extend to the apical foramina and in some cases beyond. Primary objectives of root canal treatment are to eliminate these biofilms by using chemo-mechanical treatment protocols and to prevent reinfection. Desired outcomes of effective treatment are the discontinuation of destructive aspects of the host immune response and apical healing. This chapter reviews different treatment factors and their influence on the outcome of biofilm-associated infections in root canals.


Chapter 9 – Root Canal Irrigation Luc van der Sluis, Christos Boutsioukis, Lei-Meng Jiang, Ricardo Macedo, Bram Verhaagen and Michel Versluis

The aims of root canal irrigation are the chemical dissolution or disruption and the mechanical detachment of pulp tissue, dentin debris and smear layer (instrumentation products), microorganisms (planktonic or biofilm) and their products from the root canal wall, their removal out of the root canal system and their chemical dissolution or disruption. Each of the endodontic irrigation systems has its own irrigant flow characteristics, which should fulfill these aims. Without flow (convection), the irrigant would have to be distributed through diffusion. This process is slow and depends on temperature and concentration gradients. On the other hand, convection is a faster and more efficient transport mechanism. During irrigant flow, frictional forces will occur, for example between the irrigant and the root canal wall (wall shear stress). In this chapter the irrigant flow and wall shear stress produced by different irrigation systems will be described. Furthermore, the effect of the flow on the biofilm and the chemical effect of irrigants on the biofilm will be discussed.


Chapter 10 – Inter-Appointment Medication with Calcium Hydroxide in Routine Cases of Root Canal Therapy Gunnar Bergenholtz, Calvin Torneck and Anil Kishen

This Chapter discusses the use of an inter-appointment application of calcium hydroxide in the endodontic treatment of teeth with apical periodontitis, from a historic and evidence-based perspective. Despite a long history of clinical use, and the publication of numerous in vitro, in vivo, and treatment outcome studies, strong scientific evidence in support of its use in this capacity, is still not available. Today’s “best scientific evidence” is based primarily on a just a small number of studies that by today’s standard, are not considered “strong”. However, given that elimination of bacteria from the root canal before placement of a root canal filling appears to enhance the treatment outcome, inter-appointment placement of calcium hydroxide could be an easy and appropriate way of promoting it. Any perceived advantage of its use, however, must be balanced by the risk of altering the physical properties of the root dentin due to its caustic action, particularly when it is present in the root canal for a long period of time. While clinical confirmation of an increased risk of root fracture in calcium hydroxide treated fully developed teeth is still not verifiable, prudence dictates that caution should be exercised when calcium hydroxide is used in this manner in permanent teeth that are not completely developed.


Chapter 11 – Advanced Therapeutic Options to Disinfect Root Canals Anil Kishen

Bacterial biofilms in the root canals are challenging targets to eliminate completely using conventional antimicrobial irrigants and medicaments. Therefore, advanced endodontic disinfection strategies are being tested to enhance the antibiofilm efficacy during root canal treatment. The primary goal of such treatment options are to eliminate intracanal bacterial biofilms from the anatomical complexities and uninstrumented portions of the root canal system, without producing deleterious effects on host tissues. This chapter describes the challenges offered by bacterial biofilm as a therapeutic target and discusses the current antibiofilm options such as nanoparticles, photodynamic therapy, lasers, ozone, herbs and enzymes based approaches in root canal disinfection.


CONTRIBUTORS

• Gunnar Bergenholtz, Institute of Odontology, The Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden• Christos Boutsioukis, Department of Endodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands• Luis Chávez de Paz, Endodontics, The Swedish Academy for Advanced Clinical Dentistry, Gothenburg, Sweden• Gary Dunny, Department of Microbiology, University of Minnesota, Minneapolis, MN, USA• Kishor Gulabivala, Unit of Endodontology, UCL Eastman Dental Institute, University College London, London, UK• Markus Haapasalo, Division of Endodontics, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada• Mark C. Herzberg, Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, & Mucosal and Vaccine

Research Center, Minneapolis VA Medical Center, Minneapolis, MN, USA• David E. Jaramillo, Department of Endodontics, University of Texas Health Science Center, Houston, TX, USA• Lei-Meng Jiang, Department of Endodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands• Anil Kishen, Department of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Canada• Jens Kreth, College of Dentistry, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA• Ricardo Macedo, Department of Endodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands• Philip D. Marsh, Division of Oral Biology, School of Dentistry, University of Leeds, and Public Health England, Porton Down, Salisbury, UK


CONTRIBUTORS

• Y-L Ng, Unit of Endodontology, UCL Eastman Dental Institute, University College London, London, UK• Ronald Ordinola-Zapata, Department of Endodontics, Bauru Dental School, University of São Paulo, Bauru, Brazil• Linda B. Peters, Center for Dentistry and Oral Hygiene, University Medical Center Groningen, Groningen, The Netherlands• Brandon Peterson, Center for Dentistry and Oral Hygiene, University Medical Center Groningen, Groningen, The Netherlands• Domenico Ricucci, Private practice, Cetraro, Italy.• Isabela N. Rôças, Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de

Janeiro, RJ, Brazil• Christine Sedgley, Department of Endodontology, School of Dentistry, Oregon Health & Science University, Portland, OR, USA• José F. Siqueira Jr., Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio

de Janeiro, RJ, Brazil• Calvin Torneck, Department of Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Canada• Luc van der Sluis, Center for Dentistry and Oral Hygiene, University Medical Center Groningen, Groningen, The Netherlands• Bram Verhaagen, Physics of Fluids group, University of Twente, The Netherlands• Marco A. Versiani, Department of Endodontics, Dental School of Ribeirão Preto, University of São Paulo, Brazil• Michel Versluis, Physics of Fluids group, University of Twente, The Netherlands


The editors assembling the root canal biofilm project at some coffee shop at the Hynes Convention Center in Boston, during the American Association of Endodontists Annual Session, April 2012.

springer series on biofilms: vol. 9 - the root canal biofilm

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