Shemesh, H.

English

International Migration, Integration and Social Cohesion online publications

UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)UvA-DARE (Digital Academic Repository)New insights into the root canal wallShemesh, H.Publication date2009Link to publicationCitation for published version (APA):Shemesh, H. (2009). New insights into the root canal wall. [Thesis, fully internal, Universiteitvan Amsterdam].General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s)and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an opencontent license (like Creative Commons).Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, pleaselet the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the materialinaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letterto: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. Youwill be contacted as soon as possible.Download date:09 Mar 2023     Chapter I   Introduction                  9 10New insights into the root canal wall Introduction         Endodontology is concerned with the study of the form, function and health of, injuries to and diseases of the dental pulp and periradicular region, and the prevention and treatment of apical periodontitis, caused by infection (European Society of Endodontology, 2006). The technical aim of the endodontic treatment is the shaping and cleaning of the root canal system and the filling of the canals as if to prevent coronal leakage and entomb remaining microorganisms, preventing them from irritating the periapical tissues (Sundqvist et al.1998). Recent evidence show that endodontic therapy may not always result in favorable and predictable outcomes. Moreover, it seems that clinical endodontic research neglected important issues concerning the outcome of the treatment like low sensitivity of conventional radiographs in detecting periapical lesions and low recall rates (Wu et al. in print).         In order to investigate the effectiveness of procedures during endodontic therapy, two major approaches could be taken: randomized clinical studies comparing the results of treatments and in vitro / ex vivo investigations. Randomized clinical studies have a higher level of evidence when compared to other studies but are difficult to perform not only because of the need to standardize conditions but also because experimenting on human beings requires a set of preconditions which are nowadays hard to meet. When human subjects are difficult to investigate and control, animals may provide more relevant information on the outcomes of different treatments. Experimenting with animals is controversial in most countries and strict rules and requirements make these investigations time consuming and expensive.  The next step in considering an investigation method is in vitro studies. These laboratory tests aim at investigating different materials and methods in laboratory conditions using models, extracted teeth and special machinery.     The common substrate for all endodontic procedures is the root canal itself, but different aspects of the root canal treatment from the root canal wall perspective were seldom addressed. The root canal wall is made of dentine which has a complex relationship between morphology and function (Kishen et al. 2000). This could possibly affect procedures we use during root canal treatment, which are roughly divided into two important steps: Cleaning of the root canal system (including mechanical instrumentation) and filling. These pose challenges to the clinician and researcher while there is still no consensus as to the preferred method or material of choice.   Cleaning and instrumentation of the canal        The objective of mechanical instrumentation is to remove the main bulk of infected material and its nutritional supply, facilitate irrigation and appropriately shape the canal for the filling procedure (Hülsmann et al. 2005). There are numerous problems associated with the preparation procedures and their effect on the root canal walls:  1.  A debate exists as to the formation, importance and faith of the smear layer which is created during the preparation procedures (Şen et al. 1995). This debate is addressed in a few studies in this thesis checking the influence of the removal of the smear layer on the effectiveness of the filling to prevent leakage, and the propagation of light through the dentinal tubules.  2.   In infected root canals microorganisms could be attached to the root canal walls in the form of biofilms (Svensäter & Bergenholtz 2004, Chavez de Paz 2007) which are resistant to cleaning procedures and disinfectants. Biofilms are difficult to image and investigate, and existing investigation methods involve preparation procedures that damage the structure and vitality of the biofilm. This thesis checks the ability of an ultrasound scan to image the 3D structure of biofilms nondestructively.   3.  The canal anatomy is complex and often long-oval in form (Wu et al. 2000). Efficient instrumentation and cleaning of such canals is extremely challenging. It is important to visualize and to have knowledge of internal anatomy relationships before undertaking endodontic therapy. This thesis explores the 11feasibility of optical coherence tomography as a non destructive method to look at the anatomy of the root canals and associated structures.  The root canal filling       The purpose of filling the root canal is to prevent the growth of bacteria remaining after canal preparation and the passage of fluids and bacterial elements from the pulp cavity into the periapical tissues (Sundqvist et al.1998). However, it seems that current filling materials and techniques fail to provide a leak-free seal (Wu & Wesselink 1993, Eldeniz & Ørstavik 2009).  A variety of laboratory-based experimental models are used to detect and measure leakage along root fillings. The fluid transport set-up is often used to measure leakage of water through root canal fillings (Wu et al. 1993). Xu et al. (2005) proposed and used a new model that measures the leakage of glucose molecules. The glucose leakage model is relatively easy to assemble and use and could give quantitative leakage measurements which are based on a chemical reaction between specific enzymes and glucose. This reaction is very sensitive, measured by a spectrophotometer and could detect minute concentration changes of glucose. This thesis uses the glucose penetration model in order to compare the sealing ability of various materials and methods and to further assess the advantages and limitations of this model.      Both mechanical instrumentation and obturation of the root canal could introduce defect in the root canal wall (Wilcox et al. 1997). These defects could eventually propagate into vertical root fractures and might have clinical significance. The procedures that mostly cause these defects are debatable (Lertchirakarn et al. 1999). Evidence exists as to the role of lateral compaction of gutta percha in the formation of vertical root fracture (Dang and Walton 1989), but the ability of other endodontic procedures to cause dentinal defects was not studied yet. The recent introduction of different Ni-Ti files used with engine-driven mechanical forces to endodontics could be a contributing factor in the formation of such defects. This thesis explores the influence of different endodontic procedures on the formation of defects like craze lines and vertical root fractures in the root canal wall.    Objectives of the thesis       The aim of this thesis was to suggest new methodologies to measure, image and explore the root canal walls and related interfaces and to present new insights into the root canal wall associated with endodontic treatment procedures. Specifically, 3 approaches were taken:   1.   Leakage measurements using the penetration of glucose through root canal fillings as a new model for assessing the sealing ability of different materials and methods. 2.   The application of novel imaging technologies for non destructive high resolution characterization of the root canal wall and related structures. 3.   Studies into the ability of different types of files and filling methods to inflict defects on the root canal wall.   Outline of the thesis - In chapter II, the glucose penetration model for leakage tests is tried. Different experiments are presented using this model and its ability to detect leakage patterns through different materials, set ups and conditions. Comparison between performance of different materials and methods as observed with this new model and the already established fluid transport model were also made. The limitations of this model to reliably detect leakage through root canal fillings are discussed. - In chapter III new endodontic applications for novel imaging techniques are suggested. Ultrasound scans for imaging live biofilm without damaging its delicate 3D structures and vitality. Optical coherence tomography for intra-canal imaging, showing the root canal walls and related structures nondestructively and without using ionized radiation.   - In chapter IV the formation and incidence of dentinal defects in the root canal wall after different preparation and filling procedures are discussed. Comparison is made between the lateral compaction technique and a non compaction technique, and between the use of hand files and different rotary Ni-Ti systems.   12References:   Quality guidelines for endodontic treatment: consensus report of the European Society of        Endodontology.(2006)  International Endodontic Journal 39, 921-930. Chavez de Paz LE. (2007) Redefining the persistent infection in root canals: possible role of biofilm communities. Journal of endodontics 33,652-62. Dang DA, Walton RE (1989) Vertical root fracture and root distortion: effect of spreader design. Journal of Endodontics 15, 294-301. Eldeniz AU, Ørstavik D (2009) A laboratory assessment of coronal bacterial leakage in root canals filled with new and conventional sealers. International Endodontic Journal 42:303-12. Hülsmann M, Peters OA, Dummer PMH (2005) Mechanical preparation of root canals: shaping goals, techniques and means. Endodontic Topics  10, 30-76. Kishen A, RamamurtyU, Asundi A (2000) experimental studies on the nature of property gradients in the human dentine. Journal of Biomarials research 51: 650-9.  Lertchirakarn V, Palamara JE, Messer HH (1999) Load and strain during lateral condensation and vertical root fracture. Journal of Endodontics 25 99-104.  Şen BH, Wesselink PR, Türkün M (1995) The smear layer: a phenomenon in root canal therapy. International Endodontic Journal  28,141-8.  Sundqvist G, Figdor D, Persson S, Sjögren U (1998) Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 85,86-93. Svensäter G, Bergenholtz G (2004) Biofilms in endodontic infections. Endodontic Topics 9,  27-36. Wilcox LR, Roskelley C, Sutton T (1997) The relationship of root canal enlargement to finger spreader induced vertical root fracture. Journal of Endodontics 23, 533-4.  Wu MK, De Gee AJ, Wesselink PR, Moorer   WR (1993)  Fluid transport and bacterial penetration along root canal fillings. International Endodontic Journal 26:203-8.      Wu MK, Wesselink PR (1993) Endodontic leakage studies reconsidered. Part I. Methodology, applications and relevance. International endodontic journal 26, 203-8. Wu MK, R'oris A, Barkis D, Wesselink PR (2000)  Prevalence and extent of long oval canals in the apical third. Oral Surg Oral Med Oral Pathol Oral Radiol Endod  89,739-43. Wu MK, Shemesh H, Wesselink PR (2009) Limitations of previously published systematic reviews evaluating the outcome of endodontic treatment. International Endodontic Journal in-print Xu Q, Fan MW, Fan B, Cheung GS, Hu HL (2005) A new quantitative method using glucose for analysis of endodontic leakage. Oral Surg Oral Med Oral Pathol Oral Radiol Endod  99,107-11.  13

New insights into the root canal wall

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New insights into the root canal wall

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