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    Serota i Serota i Document Transcript

    • e n d o d o n t i c s An Evidence-Based Endodontic Implant Algorithm: Untying the Gordian Knot; Part I Kenneth S. Serota, DDS, MMSc Study the past, if you would divine the future — Confucius The Endodontic Implant Algorithm — provides highlights in the assessment and identification of determinant factors leading to endodontic failures, in order to help in the decision making process whether or not it is adequate to implement an new endodontic approach vs. extraction and replacement with dental implants — ConfusionO ver the years, endodontics versus a natural state is not a rithm. “We have met the enemy... has diminished itself by en- panacea for successful treatment and he is us”.....The Pogo Papers. abling the presumption that outcomes [Fig 2a, 2b, 2c, 2d].it is comprised of a narrowly de- Scientific doctrine is the corner-fined service mix; root canal ther- In 1992, funding from the stone of Endodontic therapeutics.apy purportedly begins at the Cochrane Collaboration was ob- However, of late, anecdotal testi-apex and ends at the orifice. tained for a UK Cochrane Center mony has become the default set-Nothing could be further from the based in Oxford to facilitate the ting for new paradigms to justifytruth. It is the catalyst and pre- preparation of systematic reviews endodontic treatment modalitiescursor of a multivariate contin- of randomized trials of health care and an encomium to technologicuum, potentially the foundational (2). The Cochrane Systematic advances. The strength of the archpillar of all phases of any rehabili- Review is a process that involves of this or any specialty’s integritytation [Figs 1a, 1b, 1c]. Early di- locating, appraising, and synthe- and relevance must rely on a key-agnosis of teeth requiring end- sizing evidence from scientific stone of randomized clinical trialsodontic treatment, prior to the studies in order to provide infor- and evidence-based treatment out-development of periradicular dis- mative empirical answers to scien- comes. Expert opinions reflectedease, is critical for a successful tific research questions. In 1952, through the looking glass of busi-treatment outcome (1). Esthetics, the enterprising son of an inventor ness models or global tours cannotfunction, structure, biologics and named Ron Popeil created info- replace stringently controlled clini-morphology are the variables in mercials using 30 to 120 second cal assessments distilled from ex-the equation of optimal oral television spots to sell his inexpen- acting independent investigations.health. Interventional or inter- sive array of useful products, in- Science cannot be applied throughceptive endodontics, restorative cluding the Pocket Fisherman and a McLuhanistic rearview mirror ofendodontics, the re-engineering of the Veg-O-Matic food slicer. The technology. The two must symbioti-failing therapy, transitional end- singular goal of an infomercial cally occupy the same space regard-odontics and surgical endodontics was to get the viewer to a phone less of whether that is antitheticalencompass a vast scope of thera- immediately and have them place to the Pauli Exclusion Principle,peutic considerations prior to any their order. No waiting weeks, one of the most accepted laws ofdecision/tipping point to replace a months or even years for the lofty physics; no two objects can simulta-natural tooth. Everything we do marketing goals of branding to neously occupy the same space.as dentists is “transitional”, with pay off. Somewhere along the way,the exception of extractions. No dentistry morphed the two con- In December 2004, Salehrabiresult is everlasting, none are per- cepts. Nowhere is this becoming and Rotstein (3) published an epi-manent; thus our treatment plans more apparent than in the debate demiological study on endodonticmust reflect this reality. Artifice on the endodontic implant algo- treatment outcomes in a largewww.oralhealthjournal.com  November 2009 oralhealth 45
    • e n d o d o n t i c sFIGURE 1a, 1b—Previous endodontic therapy on tooth #2.6 (14) had failed; the FIGURE 1C—“Listening to both sides of aclinician chose to correct the problem with a microsurgical procedure on the MB story will convince you that there is moreroot. This procedure failed over time as well (sinus tract). Radiographic and clini- to a story than both sides [Frank Tyger]”.cal evidence demonstrate the developing apical lesion. The root canal system was The endodontic implant algorithm en-re-accessed, the untreated canal identified, the entire system debrided, disinfected sures that philosophy does not obscureand after interim calcium hydroxide therapy, obturated. One year later, the lesion pragmatism and expediency does nothas healed. While the retrograde amalgam remained in the root end, its presumed denigrate adaptive capacity.ability to effectively seal a complex apical terminal configuration was ill-considered.Everything leaks in time; retreatment is always the first choice for resolution of anunsuccessful endodontic procedure where possible. ologic vectors of pulpal disease and the myriad complexity of thepatient population. The outcomes the algorithm by which sacrifice root canal system had alwaysof initial endodontic treatment of natural structures for orthobio- been understood; as the centurydone by general practitioners and logic replacements can be vali- closed, clinicians were providedendodontists participating in the dated and the engineering prin- with new tools and technology toDelta Dental Insurance plan on ciples and designs that best mimic expand the boundaries and limi-1,462,936 teeth of 1,126,288 pa- clinical dictates. tations of endodontic treatmenttients from 50 states across the procedures [Figs 4a, 4b].USA were assessed in an eight Evolutionary Paradigm Shiftsyear timeline. 97% of teeth were Three surveys have been con- Root canal infections are poly-retained in the oral cavity subse- ducted with the membership of microbic, characterized predomi-quent to nonsurgical endodontic the American Association of nantly by both facultative andtreatment over this period. The Endodontists since the late 1970’s. obligate anaerobic bacteria (9).combined incidence of untoward The first reflected what is now an The necrotic pulp becomes a res-events such as retreatments, api- anachronistic view of emergency ervoir of pathogens, toxic conse-cal surgeries, and extractions was procedures and the standard of quences and their resultant in-3% and occurred primarily within care defining non-surgical ther- fection is isolated from the3 years from the completion of apy during that period (7); the patient’s immune response.treatment. Analysis of the ex- second, done prior to the techno- Eventually, the microflora andtracted teeth revealed that 85% logic advances of the last decade their by-products will produce ahad no full coronal coverage. A of the twentieth century, was periradicular inflammatory re-statistically significant difference hallmarked by a dramatic de- sponse. With microbial invasionwas found between covered and crease in leaving pulpless teeth of the periradicular tissues, anuncovered teeth for all tooth open in emergency situations and abscess and cellulitis may de-groups tested which is consistent a significant decline in the use of velop. The resultant inflamma-with the findings from numerous culturing prior to obturation (8). tory response will initiate eitherinvestigations (4, 5, 6). The report indicated that the con- a protective and/or immuno- cept of “debridement and disinfec- pathogenic effect; additionally, it The purpose of this publication tion” versus “cleaning and shap- may destroy surrounding tissueis to evaluate current trends and ing” was now the focus of the resulting in the five classic signsperceptions pertaining to the biologic therapeutic imperative and symptoms of inflammation;standard of care in endodontics and the need for expansive micro- calor, dolor, rubor, tumor andand provide an evidence based bial strategies was recognized as penuria. Patient evaluation andconsensus on their relevance and being of paramount importance the appropriate diagnosis/treat-application. Part II will address [Fig 3]. The primary patho-physi- ment of the source of an infection46 oralhealth November 2009 www.oralhealthjournal.com
    • e n d o d o n t i c sare of utmost importance. Patients demonstrating signsand symptoms associated withsevere endodontic infection(Table I) should have the rootcanal system filled with calciumhydroxide and the access sealed.In the event of copious drainage,the access can be left open for nolonger than 24 hours, the tooththen isolated with rubber dam,the canals irrigated and driedand calcium hydroxide inserted FIGURE 2a, 2b—Tooth #1.5 (4) was determined to be non-salvageable. It was re-into the root canal space and the moved, the socket stimulated to regenerate and in four month’s time an ANKYLOS®access sealed (10). The antibiotic implant inserted, a sulcus former placed and the tissue closed over the site to allow for osseo-integration to occur.of choice for periradicular ab-scess remains Penicillin VK;however, recent studies have re-ported that amoxicillin in combi-nation with clavulinate (1gmloading dose with 500mg q8h for7 days) was a more effective ther-apeutic regimen (11). Systemic antibiotic adminis-tration should be considered ifthere is a spreading infection thatsignals failure of local host re- FIGURE 2C, 2D—The choice of a natural tooth versus an orthobiologic replacementsponses in abating the dispersion will increasingly be a powerful force in dental treatment plans. The temptation toof bacterial irritants, or if the pa- choose one or the other based on expediency versus complexity, on marketing ver-tient’s medical history indicates sus science is going to be the sine qua non of the standard of comprehensive care.conditions or diseases known toreduce the host defense mecha-nisms or expose the patient to Recursions in the micro-processing radiography should have gener-higher systemic risks. Antibiotic technologies of electronic forame- ated the greatest impact; how-treatment is generally not recom- nal locators begat unprecedented ever, its value remains limited inmended for healthy patients with accuracy levels, improved digital diagnosis, treatment planning,irreversible pulpitis or localized radiographic sensors and software intra-operative control and out-endodontic infections (Table II). enhanced diagnostic acumen, and come assessment. Flat field sen-Numerous studies with well-de- ultrasonic units with a variety of sors still require 3 to 4 parallaxfined diagnosis and inclusion cri- tips designed specifically for use images of the area of interest toteria failed to demonstrate en- when performing both nonsurgical establish better perception ofhanced pain resolution beyond and surgical endodontic procedures depth and spatial orientation ofthe placebo effect (12, 13). minimized damage to coronal and osseous or dental pathology. These radicular tooth structure in the ef- three-dimensional information The sophistication of endodontic fort to locate the pathways of the deficits, geometric distortion andequipment, materials and tech- pulp. The treatment outcome of the masking of areas of interestniques has been steadily iterated non-surgical root canal therapy at by overlying anatomy or anatomicand innovated since the second this point in time is far more pre- noise are of strategic relevance tosurvey. The microscope first intro- dictable than at any other period in treatment planning in generalduced to otolaryngology around our history. and in endodontics specifically1950, then to neurosurgery in the (14)[Figs. 5a, 5b].1960’s, is now standard of care for Diagnosisthe voyage into the microcosmic Of all the technologic innovations Cone beam computed tomogra-world of the root canal system. embraced by endodontics, digital phy (cbCT) produces up to 580 in-www.oralhealthjournal.com  November 2009 oralhealth 49
    • e n d o d o n t i c s ing multiplanar views, the determination of the root canal anatomy and the number of canals, the detec- tion of the true nature and exact location of resorp- tive lesions and the discovery of the existence of vertical and horizontal fractures outweigh concerns about the degree of ionizing radiation and the risks posed (17). Provided cbCT is used in situations where the information from conventional imaging systems is inadequate, the benefits are essential for optimization of the standard of care.FIGURE 3—The degree of complexity of the root canal systemhas been understood for most of the past century. The failure Patel reported that periapical disease can be de-to negotiate the labyrinthine ramifications of the root canal tected sooner and more accurately using cbCT com-system has purportedly been a function of technical limitation pared with traditional periapical views and that therather than comprehension and yet, it took until the mid 70’s true size, extent, nature and position of periapicalto appreciate that thermolabile condensation of an obturating and resorptive lesions can be accurately assessedmaterial could demonstrate a greater occlusive degree of the (18). Using a new periapical index based on conesystem than any other modality. beam computed tomography for identification of api- cal periodontitis, periapical lesions were identified in 39.5% by radiography and 60.9% of cases by cbCT respectively (P < .01). Simon et al compared the dif- ferential diagnosis of large periapical lesions with traditional biopsy. The results suggested that cbCT might provide a faster method to differentially diag- nose a solid from a fluid-filled lesion or cavity, with- out invasive surgery (19, 20). In spite of the presence of artifacts, the learning curve related to image manipulation and the cost, cone beam tomography will invariably be the accepted standard of diagnos- tic care and treatment planning in endodontics inTable I and II—Derived from Antibiotics and the Treatment of the very near future.Endodontic Infections - Summer 2006 - American Associationof Endodontics - Colleagues for Excellence Access An improperly designed access cavity will hamperdividual projection images with isotropic submilli- facilitation of optimal root canal therapy. If the ori-meter spatial resolution enhanced by advanced entation, extension, angulations and depth are inac-image receptor sensors; it is ideally suited for dedi- curate, retention of the native anatomy of the rootcated dento-maxillofacial CT scanning. When com- canal space becomes precarious. The requirementsbined with application-specific software tools, cone of access cavity design can be achieved by concep-beam computed tomography can provide a complete tual and technical regression of the existing con-solution for performing specific diagnostic and sur- figuration to that which one would logically expectgical tasks. The images can be resliced at any angle, to have seen prior to the insults of restoration, func-producing a new set of reconstructed orthogonal im- tion and aging. If tertiary dentin were perceived ofages and studies have shown that the scans accu- as “irritational dentin” or dystrophic calcificationrately reflect the volume of anatomic defects. The considered “decay”, the chamber outline could belimited volume cbCT scanners best suited for end- used to blueprint an inlay configuration for the ac-odontics require an effective radiation dose compa- cess design that literally replicates the “virgin”rable to two or three conventional periapical radio- tooth (Fig 7).graphs and as such are set to revolutionizeendodontics (15, 16) [Fig 6]. Removal of the existing restoration in its entirety and/or preliminary preparation of the coronal tooth Three dimensional pre-surgical assessment of structure for the subsequent full coverage restora-the approximation of root apices to the inferior den- tion will identify decay, fractures, unsupportedtal canal, mental foramen and maxillary sinus are tooth structure and expose the anatomy of the un-essential to treatment planning. The ability of cbCT derlying root trunk periphery which assists in dis-to diagnose and manage dento-alveolar trauma us- covery of the spatial orientation and morphology of50 oralhealth November 2009 www.oralhealthjournal.com
    • e n d o d o n t i c sthe roots. The pulp chamber ceil- composites, when restoring access more efficient technique whiching and pulp stones can be peeled cavities, the best esthetics and provides acceptable esthetics is toaway with a football diamond bur highest initial strength are ob- bulk fill with a glass ionomer ma-to grossly identify the primary tained with an incremental fill terial to within 2 to 3 mm of theorifices. Micro-etching (Danville technique with composite resin, a cavo-surface margin, followed byMaterials, San Ramon CA) thefloor of the chamber, perhaps themost underused of all access tools,is invaluable in the exposure offusion lines and grooves in orderto identify accessory orifices.Troughing with ultrasonic tips ofany design is used solely to tracefusion lines, not effect gross re-moval. The use of ultrasonics to“jackhammer” pulp stones is sim-ply too risky as one approachesthe floor of the chamber, particu-larly if there are no water ports FIGURE 4a—Panel of anatomic prepara- FIGURE 4b—Vertucci FJ - 1984.Two thou-on the tips. Orifice lengthening tions from the classic work by Professor sand four hundred human permanentand widening enables straight Walter Hess of Zurich - The Anatomy of teeth were decalcified, injected withline glide path to the apical third. the root canals of teeth of the permanent dye, and cleared in order to determineThe strategic objective is not to dentition, London, 1925, John Bale, the number of root canals and their dif-impede the file, stainless steel or Sons & Danielsson. ferent morphology, the ramifications ofnickel-titanium rotary along the the main root canals, the location of api- cal foramena and transverse anastomo-axial walls with minimal dentin ses, and the frequency of apical deltas.removal [Figs 8a, 8b]. It is equally as important toproduce a high quality coronalrestoration at the time of sealingthe root canal system (21, 22).Despite research supporting theeffectiveness of coronal barriersand the need for their immediate FIGURE 5A, 5b—Flat field sensors provide a sense of the extent of osseous pathology;placement as a component of the however, the periapical radiographic image corresponds to a two-dimensional as-completion phase of root canal pect of a three dimensional structure. Periapical lesions confined within the cancel-treatment, a universally accepted lous bone are usually not detected. Thus a lesion of a certain size can be detected inprotocol does not exist. Schwartz a region covered by a thin cortex, whereas the same size lesion cannot be detected in a region covered by thicker cortex.and Fransman have described aclinical strategy for coronal seal-ing of the endodontic access prep-aration that lists the followingconsiderations in the protocol; usebonded materials [4th generation(three step) resin adhesive sys-tems are preferred because theyprovide a better bond than theadhesives that require fewer FIGURE 6—All cone beam tomography FIGURE 7—Strategic extension of thesteps], the “etch and rinse” adhe- units provide correlated axial, coronal access perimeter is too often underval-sives are preferred to “self etch- and sagittal multiplanar volume reforma- ued in terms of successful endodonticing” adhesive systems if a eugenol tions. Basic enhancements include zoom treatment outcomes. The shape of thecontaining sealer or temporary or magnification and visual adjustments chamber must be regressed to its nativematerial is used, “self etching” to narrow the range of grey-scale, in state to ensure that axial interference isadhesives should not be used with addition to the capability to add annota- negated as an instrument traverses theself-cure or dual-cure restorative tion and cursor-driven measurement. length of the root canal space.www.oralhealthjournal.com  November 2009 oralhealth 51
    • e n d o d o n t i c s FIGURE 8b—Keeping the chamber wet FIGURE 9—Micro-etching ensures the re- with alcohol improves optics and high- moval of oils and debris as well as lights colour differential. The most im- eliminating the residue in fusion lines portant tool for orifice identification in and fissures. Routine dentin bonding is addition to dyes is a micro-etcher. The then performed. The composite chosen satin finish produced highlights the dis- in this instance is Permaflo(r) Purple parity between the natural tooth struc- (UPI, South Jordan, UT) which enablesFIGURE 8a—Dystrophic calcification con- ture of the floor and the secondary and differentiation of restoration and toothfounds even the most experienced clini- tertiary dentin of the calcified orifice. structure should re-entry be necessary.cian. The key to identification of theorifices is to regress the inner spaceusing the continuum, cusp tip, pulp horn, (24). While our knowledge of per- the samples were positive prior tocanal orifice. In lieu of an ultrasonic tip sistent bacteria, disinfecting root filling, the success rate ofwhich tends to chop the stone and scat- agents and the chemical milieu of treatment was just 68%- a statis-ter debris, gross removal is best done the necrotic root canal has greatly tically significant difference.with a diamond bur in a high speed increased, there is no doubt that These findings emphasize the im-handpiece. The fine removal of residue more innovative basic and clinical portance of completely eliminat-can be done with a multi-fluted carbide research is needed to optimize the ing bacteria from the root canalbur to trace the fusion lines. use of existing methods and mate- system prior to obturation. This rials and develop new ones in or- objective cannot be reliablytwo increments of light-cure com- der to prevent and/or treat apical achieved in a one-visit treatmentposite and if retention of a crown periodontitis. of necrotic pulps because it is notor bridge abutment is a concern possible to eradicate all infectionafter root canal treatment, post Varying degrees of sterility of from the root canal without theplacement increases retention to the root canal space are achieved support of an inter-appointmentgreater than the original state by mechanistic removal, the antimicrobial dressing (25).(23) [Fig 9]. chemical reactivity and fluid dy- namics of irrigants and their in- NaOCl is the most widely usedIrrigation troduction to the canal space; irrigating solution. It is a potentThe complex anatomy of the root however, the protocols used today antimicrobial agent and lubricantcanal space presents a daunting cannot predictably provide sterile which effectively dissolves pulpalchallenge to the clinician who canals. As none of the elements of remnants and organic compo-must debride and disinfect the endodontic therapy (host defense nents of dentin thus preventingcorridors of sepsis with absolute- system, systemic antibiotic ther- packing infected hard and softness to achieve a successful treat- apy, instrumentation and irriga- tissue into the apical confines.ment outcome [Fig 10]. In addi- tion, inter-appointment medica- Hypochlorous acid (HClO) is thetion, the absence of a cell-mediated ments, permanent root filling, active moiety responsible for bac-defense (phagocytosis, a func- and coronal restoration) can alone terial inactivation. NaOCl is usedtional host response) in necrotic guarantee complete disinfection, in concentrations varying fromteeth means the microorganisms it is of utmost importance to aim 0.5%to 5.25%; the in vitro and inresidual in tubuli, cul de sacs and at the highest possible quality at vivo studies differ significantly inarborizations are mainly affected every phase of the treatment. In terms of the effectiveness of theby the redox potential (reduction the classic study by Sjogren et al, range of concentrations as the inpotential reflects the oxidation- 55 single-rooted teeth with apical vitro experiments provide directreduction state of the environ- periodontitis were instrumented access to microbes, higher vol-ment — aerobic microflora can and irrigated with sodium hypo- umes are used and the chemicalonly be active at a positive Eh, chlorite and root filled. Periapical milieu complexity of the naturalwhereas strict anaerobes can only healing was followed-up for 5 canal space are absent than inbe active at negative Eh values) years. Complete periapical heal- the in vivo experimentation. Aand availability of nutrients in ing occurred in 94% of cases that study by Siqueira et al (26) showedthe various parts of the root canal yielded a negative culture. Where no difference (in vitro) between52 oralhealth November 2009 www.oralhealthjournal.com
    • e n d o d o n t i c s FIGURE 10—A vast array of equipment exists in the marketplace to optimize irrigation protocols. Radical change may well be in the offing, however, R&D on bio-active obturating materials may prove to be the defining variable in total asepsis. 1%, 2.5% and 5% NaOCl solutions in reducing the number of bacteria during instrumentation. What has been shown is that the tissue dissolving effects are directly related to the concentration used (27). Perhaps the most misunderstood aspect of NaOCl irrigation is the need for the quantities of irrigation required due to the morphologic and anatomic variations in the volumetric size of the root canal anatomy. Siqueira showed that regular exchange and the use of large amounts of irrigant should maintain the antibacterial effectiveness of the NaOCl solution, compensating for the effects of con- centration (28). Numerous devices have appeared in the endodontic armamentarium to address this sit- uation; EndoVac (Discus Dental) — a negative pres- sure differential device designed to deliver high volumes of irrigation solution while using apical negative pressure through the office high volume evacuation system, Negative Pressure Safety Irrigator (Vista Dental, Racine WI) — device is similar to EndoVac, Rinsendo (Air Techniques, Corona CA) uses pressure suction technology; 65 ml of irrigant are automatically drawn from the at- tached syringe and aspirated into the canal [pres- sure created is lower than manual irrigation], VIbringe (Bisco Canada, Richmond BC) — sonic flow technology facilitates enhanced irrigation through the myriad complexities of the root canal system [Fig 11]. NaOCl cannot dissolve inorganic dentin particles and thus prevent smear layer formation during in- strumentation (29). Chelators such as EDTA and citric acid are recommended as adjuvants in root canal therapy. It is probable that biofilms are de- tached with the use of chelators; however, they have little if any antibacterial activity. Several studies have shown that citric acid in concentrations rang- ing as high as 50% was more effective at solubiliza-54 oralhealth November 2009 www.oralhealthjournal.com
    • tion of inorganic smear layer components and pow-dered dentin than EDTA. In addition, citric acid hasdemonstrated antibacterial effectiveness. Technology and innovation will not negate theneed for optimal preparation (debridement and dis-infection) to eliminate microbial content and itsimpact on a necrotic root canal system. We as a dis-cipline need to be better; however, by the same to-ken, endodontics has shown its commitment to end-less reinvention. In time, that will restructure therole of natural teeth in foundational dentistry, cur-rently diminished by the market forces of implantdriven dentistry. Orthobiologic replacement is not apanacea as random clinical trials increasinglyshow; the severity of peri-implantitis lesions demon-strates significant variability and as such no treat-ment modality has shown superiority. The pendu-lum will continue to swing as the endodonticimplant algorithm becomes increasinglymultivariate.Microstructural Replication — ObturationSteven Covey is known for his book The SevenHabits of Highly Effective People. The habit mostapplicable to endodontics is the second one; Beginwith the End in Mind. The implication of this visionin regard to idealizing the final shape of the rootcanal system to ensure that the obturation repre-sents a totality is profound. The root canal is nega-tive space and as such recovery of its original unaf-fected form is the sine qua non of obturation or moredescriptively — microstructural replication. Perhaps the most significant example of negativespace recovery is Michelangelo’s statuary for thefunerary of Pope Julius II. Four unfinished sculp-tures speak eloquently to this process: the figurewas outlined on the front of the marble block andthen Michelangelo worked steadily inwards fromthis side, in his own words ‘liberating the figureimprisoned in the marble’. This is an exacting de-scription of debridement and instrumentation of theroot canal space prior to root filling after a myriadof pathologic vectors have destroyed the dental pulp,and altered the morphology/topography of the sys-tem [Fig 12]. Incomplete filling of the debrided and sculptedroot canal space is one of the major causes of end-odontic failure (30). Until recently, in vitro testing(dye leakage, fluid transport, bacterial penetration,glucose leakage) was used to evaluate the sealingefficacy of endodontic filling materials and tech-niques by assessing the degree of penetration/absor-bance of these tracers (31, 32, 33). Unfortunately,www.oralhealthjournal.com  November 2009 oralhealth 55
    • e n d o d o n t i c s FIGURE 13—While there is no meta- analysis to elucidate this concern, the incidence of fracture of the mesial root of mandibular molars has been shown FIGURE 12—The artist/clinician recog- to have a significant correlation to cus- nizes that negative space surrounding pal fracturing. an object is equally important as the object itself. In the case of root canal rate when compared with step-FIGURE 11—Numerous investigators have therapy, the positive space is alterable, back canal preparation and lateralshown that the concept of keeping the but must be created in balance with the compaction. Highlighting the ver-apical foramen foramen as small as encompassing negative space to ensure tical condensation of warm gutta-practical does not mean a size 20 or morphologic integrity. percha obturation technique as a25 file. This Schilderian concept shouldread as small as the apical morphology factor influencing success and fail-permits in order to ensure that the free root canal space badly, in three ure simply confirmed a perspec-flow of irrigant to the apical terminus dimensions. This does not critique tive evident to most endodontistsenables more definitive cleaning of the Dr. Schilder’s exposition, but it from years of clinical empiricism.apical segment of the root canal space. does demonstrate that words can easily be misconstrued and alter There is a never ending array ofleakage studies are limited static perspective once they become, as obturation materials, delivery sys-models that do not simulate the Kipling said, ‘the most powerful tems and sealers appearing in theconditions found in the oral cavity drug of mankind’. Ironically, marketplace. Each is hallmarked(temperature changes, dietary in- Schilder’s article came seven by proprietary modifications andfluences, salivary flow). Given the years prior to his treatise on each is heralded as the most sig-historic dominance of in vitro cleaning and shaping the root ca- nificant iteration in obturationtesting, the clinician must be cau- nal system which even to this day since the previous one; today, wetious when extrapolating study remains the iconic standard for practice with a sad truism — mar-findings to the clinical situation, the technical imperatives associ- keting is inexorably directing sci-regardless of manufacturer’s ated with instrumentation. ence. However, gutta-percha inclaims (34). This reliance on in- combination with a myriad of seal-valid testing protocols diminishes The Washington Study by Ingle ers and solvents remains the pri-the “mono-block” assertions ap- indicated that 58% of treatment mary endodontic obturating mate-plied to the new generation of ad- failures were due to incomplete rial. The dominant systems remainhesive obturating materials pro- obturation (39). The corollary is carrier based obturation (Thermafilposed as the “replacement obvious; teeth that are poorly ob- — Tulsa Dental Specialties, Tulsamaterial” for gutta-percha (35). turated are invariably poorly de- OK), Continuous Wave Compaction brided and disinfected. Procedural Technique (Elements Obturation Gutta-percha was introduced errors such as loss of working — Sybron Endo, Orange CA andto dentistry by Edwin Truman in length, canal/apical transporta- Thermoplastic Injection (Obtura III1847(36). The concept of thermo- tion, perforations, loss of coronal Max — Obtura Spartan, Earthlabile vertical condensation of seal and vertical root fractures City MO).gutta-percha was originally de- have been shown to adversely af-scribed by Dr. J. R. Blaney in fect the integrity of the apical seal Resilon (RealSeal —1927(37). The defining article on (40, 41). The Toronto study evalu- SybronEndo Corp., Orange, CA),obturation remains Dr. Schilder’s ating success and failure of end- a high performance industrialclassic on filling the root canal odontic treatment at 4 to 6 years polyurethane was developed asspace in three dimensions pub- after completion of treatment an alternative to gutta-percha.lished some forty years later (38). showed that teeth treated with a There are scattered studies thatLogically, one cannot physically flared canal preparation and ver- show Resilon exhibits less micro-fill the root canal in two dimen- tical condensation of thermolabile bial leakage (42) and higher bondsions; however, one can fill the gutta-percha had a higher success strength to root canal dentin56 oralhealth November 2009 www.oralhealthjournal.com
    • e n d o d o n t i c sFIGURE 14a—The working length has two reference points, coronal and apical.Failure to maintain patency at the minor apical diameter will cause loss of the FIGURE 14b—The volume of irrigant nec-apical reference point as a result of blockage, or ellipticization of the foramen. essary to prevent apical blockage is indeterminant. While NiTi rotary instru- mentation has minimized this procedural(43), reduced periapical inflam- and an improvement in the bacte- problem to a significant degree, none-mation (44) and enhanced frac- rial seal. This applies to carrier theless, a slurry of dentin mud is alwaysture resistance of endodontically based obturation techniques, a risk factor to be monitored.treated teeth when compared Continuous Wave Compactionwith gutta-percha (45) [Fig 13]. Technique and Obtura III obtura-Other studies have reported un- tion without cone placement.desirable properties associatedwith Resilon including low push- Instrumentationout bond strength (46) and low The steps required for debride-cohesive strength plus stiffness ment and disinfection of the root(47). In addition, Resilon could canal space are sequential andnot achieve a complete hermetic interdependent. Aberration of anyapical seal (48). These results in- node in the process impacts upondicate that a more appropriate the others leading to iatrogenic FIGURE 15—Rheology is a science thatmaterial for root canal obtura- damage and potentially, treat- addresses the deformation and flow oftion still needs to be developed. ment outcome failure. The most matter. The biochemistry of filling mate- rial, its viscosity gradient, the lubricatingThere is still no obturation common distortion of native anat- effect of sealer and optimal thermalmethod or material that produces omy is ledging; canal curvature application are only as effective as thea leakproof seal. A material that exceeding 20o was shown to pro- flow characteristics of the shape createdis bio-inductive and promotes re- duce ledging of mandibular mo- and its degree of cleanliness.generation, a “smart” nano-mate- lars in a cohort of undergraduaterial that can adapt to the ever- students 56% of the time (49).changing microenvironment of Dentin chips pushed apically by nus without widening it is mostthe canal system is essential, but instrumentation incorporated effective; it will refresh the NaOCltodate, remains elusive. with fragments of pulp tissue will at the terminus as the action of compact into the apical third and the file going to the point of pa- All polymers demonstrate melt the foramenal area causing block- tiency produces a fluid dynamic.temperature and flow rate. Both age, altering the working length Regrettably, loss of workinggutta-percha and Resilon demon- due to the loss of patency [Figs length remains a common ad-strate demonstrate a viscoelastic 14a, 14b]. verse event during endodonticgradient that manifests as a dy- therapy, especially among less ex-namic rheological birefringence in Apical patency is a technique perienced clinicians. Its majorthe molded state. Dependent upon in which the minor apical diame- cause is the formation of an apicalthe molecular weight of the source ter of the canal is maintained free dentin plug. Therefore, establish-material (without the opacifiers, of debris by recapitulation with a ing apical patency is recom-waxes and modifiers), gravimetric small file through the apical fora- mended even during treatment ofmeasurements the time-tempera- men (50). The most predictable canals with vital pulps (51).ture-transformation diagram of method is to regularly use a des-any molding compound can be con- ignated patency file throughout Historically, numerous tech-structed. In the thermoplastic the cleaning and shaping proce- niques have been advocated forworld of today, this has engen- dure in conjunction with copious canal preparation (balanced force,dered an increase in the weight of irrigation. A #.08 K-file passively anti-curvature, double-f lare,the mass of obturating material moved through the apical termi- modified double-flare); however,58 oralhealth November 2009 www.oralhealthjournal.com
    • e n d o d o n t i c sFIGURE 16a—The ProTaper Universal System comprises two FIGURE 16b—Modification of taper in last mm of the apicalshaping files that address the planes of geometry of the coro- terminus, exaggerates the “constriction” or minor apical di-nal and middle thirds of the root canal space. There are five ameter. Thermo-labile vertical condensation has been shownfinishing files that include tips sizes, 20, 25, 30, 40 and 50. to enhance successful endodontic outcomes. The matrix effectTapers range from .06 to .09 through the series. A thorough of the apical control zone enhances the gravitometric densityunderstanding of the metrics is essential for the preparation of of the required hermetic apical seal as well as enabling morethe myriad variations in internal micro-morphology of the root material to flow into the region to occlude fins, cul-de-sacs,canal space and the assurance of minimal iatrogenic impact. deltas and lateral arborizations.step-back (52) and crown-down strumentation technique produced topography of the accessible canal(53) are the most universally ac- a cleaner apical portion of the ca- space and its degree of curvature.cepted. Experience has shown nal than other techniques [Fig 15]that a crown-down preparation (56, 57). As will be discussed A second “wave” with the NiTiwill cause fewer procedural errors shortly, this author remains com- rotaries is then used to effect(apical transportation, elbow for- mitted to hand filing in order to deep shape approximating themation, ledging, strip perforation, refine apical third shaping and working length and dependinginstrument fracture). The prelim- creating an enhanced apical con- upon the configuration of the api-inary removal of coronal dentin trol zone taper. cal third, to enlarge the terminus(pre-enlargement — treating the to the gauged apical size and ini-apex last) minimizes blockage Two distinct phases are re- tiate the taper of the apical con-and enables an increasing volume quired for the preparation of ca- trol zone (58). This is a basic con-of irrigant penetration thereby nals with nickel titanium (NiTi) cept. It is inherent in all templatedsustaining working length rotary files. It is essential, that no protocols that each tooth is differ-throughout the procedure (54). matter the protocol used, a reser- ent and modifications to the pro- voir of NaOCl must be maintained cess are always necessary as a The balanced force shaping phi- and replenished repeatedly in the function of the tooth morphologylosophy is integral to the crown- strategically extended access and type being treated.down approach. Its premise is that preparation. The coronal portion ofinstruments are guided by the ca- the canal space is explored with The apical control zone is de-nal structure when rotational/ small sized K-files to establish a fined as a matrix like region cre-anti-rotational motion (watch- glide path for the rotaries to follow. ated at the terminus of the apicalwinding) is used. Changing the The taper of NiTi files, regardless third of the root canal space. Thedirection of rotation controls the of manufacturer induces a crown- zone demonstrates an exagger-probability that instruments will down effect in the straight portion ated taper from the spatial posi-become overstressed and thus en- of the canal. After the coronal and tion determined by an electronicsures that the cutting of structure middle third segments are opened foramenal locator to be the minoroccurs most efficiently (55). and repeatedly irrigated with apical diameter. Whether this isEndodontists have long appreci- NaOCl, a sequence of small K-files linear or a point determination isated what the science reported, can progress apically, ultimately a function of histopathology. Thethat the balanced-force hand in- defining patency, confirming the enhanced taper at the terminuswww.oralhealthjournal.com  November 2009 oralhealth 61
    • e n d o d o n t i c screates a resistance form against in conjunction with hand filing, destruction. In addition, the clini-the condensation pressures of ob- the apical control zone created cian must consider questionableturation and acts to prevent ex- will enhance the apical seal as teeth in need of endodontic treat-cessive extrusion of filling mate- the rheologic vectors of compac- ment, teeth requiring root ampu-rial during thermo-labile vertical tion and condensation have a tations, hemi-sections or ad-compaction. greater lateral volume of displace- vanced periodontal procedures ment at the terminus. with a questionable prognosis and All NiTi systems are modeled pulpless teeth fractured at theupon a single or multiple taper ra- gingival margin with rootstio per millimeter of file length. shorter than 13 mm. These teethFig 16a demonstrates the metrics will require endodontic treat-of the F1, F2, F3 finishing files of ment, crown lengthening, post/the ProTaper Universal system “Does science cores and crowns; however, their(author’s preference). These files longevity is very much in doubtdemonstrate a common taper in drive the market, with these parameters (60).the last 4 mm of the file which in or does the marketthe vast majority of situations cor- Practitioners are ethically obli-responds to the length of the apical drive science?” gated to inform patients of allthird of the root canal space. As reasonable treatment options. Itshown, the .07 taper of the F1 (.20 is the patient’s attitude, valuestip), the .08 taper of the F2 (.25 tip) and expectations that are inte-and the .09 taper of the F3 (.30 tip) gral to the risk assessment algo-produce the corresponding diame- Fashioning a Risk rithm. Poor motivation to retain atral dimension indicated each mil- Assessment Algorithm tooth mandates extraction, notlimeter back from the apical ter- If the biologic parameters that clinical intervention whereasminus if the crown down protocol mandate endodontic success are high motivation advocates non-built into this multiple taper file adhered to, in almost all cases, surgical intervention or surgery.system is adhered to. If the shape treatment outcomes will be suc- The process of planning, presen-of the internal micro-morphology cessful. The endodontic implant al- tation and acceptance of dentalof the root complex were epidemio- gorithm processes the array of con- treatment plans is always domi-logically similar, then “imprint- tributing factors leading to nated by the duality of emotioning” of the canal preparation would endodontic failure, in order to de- and pragmatism associated withbe logical. Unfortunately, such is termine whether to implement a cost. Where it becomes specious isnot the case (59). re-engineered endodontic approach the side by side dollar comparison or to extract and replace the natu- of restoring a natural tooth or Fig 16b shows how the use of ral tooth with an osseo-integrated placement of a fixed bridge et alhand files in the apical third can implant. It finds the greatest com- in contrast to orthobiologic re-alter the preliminary shape cre- mon divisor among the degree of placement of a debilitated tooth.ated by the NiTi files. Hand files coronal breakdown of the involvedhave a .02 taper (along the shaft or adjacent teeth, the quality and Far too often the comparison ofof the file, the diameter increases quantity of the bone support and purported treatment outcome per-by .02 mm per mm of length — tissue condition, the engineering centages are based upon corporate.20 file with 16 mm of flutes demands to be born by the tooth or affiliation and/or fiduciary bias, orwould be measure .52 mm at the teeth in question and assesses the are simply too narrow a parametercoronal end of the flutes). In the occlusal scheme and the patient’s to suggest comparable alterna-example shown, a #20 file is posi- aesthetic and functional expecta- tives. With the treatment optionstioned at the minor apical diame- tions of treatment. available to an experienced endo-ter. Careful positioning of a series dontist, only a very few structur-of file within the last mm can pro- The reasons for tooth extrac- ally sound teeth need be removed.duce a .2 mm or 20% taper with tion may include, but are not lim-no undue disruption of the native ited to, crown to root ratio, re- Benjamin Disraeli said:anatomy. Schilder’s precept for maining root length, periodontal “Expediency is a law of nature.shaping was to keep the apical attachment levels, furcation sta- The camel is a wonderful animal,foramen as small as practically tus, periodontal health of teeth but the desert made the camel.”possible. Whatever file approxi- adjacent to the proposed fixture The endodontic implant algorithmmates the minor apical diameter, site and non-restorable carious See Evidence page 7462 oralhealth November 2009 www.oralhealthjournal.com
    • e n d o d o n t i c s digms, and perspectives. OS, OM, OP, OR & Endo Sept leakproof root fillings. J Endo Sept 2008;(34)9:1093-5Evidence continued from page 62 2002;94(3):281-293 32. Barthel CR, Moshonov J, Shuping G, Orstavik D. 10. Siqueira JF Jr, Guimar„es-Pinto T, RÙÁas IN. Effects Bacterial leakage versus dye leakage in obturated root of chemomechanical preparation with 2.5% sodium canals. Int Endod J 1999;32:370 -5begs the question, “Does science hypochlorite and intracanal medication with calcium 33. Kersten HW, Moorer WR. Particles and molecules indrive the market, or does the mar- hydroxide on cultivable bacteria in infected root canals. J endodontic leakage. Int Endod J 1989;22:118-24 Endod. 2007 Jul;33(7):800-5 34. Oliver CM, Abbott PV. Correlation between clini-ket drive science”. “All truths are 11. Baumgartner JC, Hutter JW, Siqueira JF. Endodontic cal success and apical dye penetration. Int Endod Jeasy to understand once they are Microbiology and Treatment of Infections. In: Cohen S, 2001;34:637-44 Hargreaves KM, editors. Pathways of the Pulp. Ninth ed. 35. PaquÈ F, Sirtes G. Apical sealing ability of Resilon/discovered; the point is to dis- St. Louis: Mosby; 2006 Epiphany versus gutta-percha/AHPlus: immediate andcover them.” — Galileo. Time and 12. Baumgartner JC, Xia T. Antibiotic susceptibility of 16-months leakage. Int Endod J. 2007 Sep;40(9):722-9 bacteria associated with endodontic abscesses. J Endod 36. Cruse WP, Bellizzi R. A historic review of endodonticsforbearance will bear witness to 2003;29(1):44-47 1689-1963, Part I. J Endod,1980; 6:495-499 13. Khemaleelakul S, Baumgartner JC, Pruksakorn S. 37. Blaney JR. The biologic aspect of root canal therapy.the discovery of the salient and Identification of bacteria in acute endodontic infections Dental Items of Interest 1927;49:681-708relevant truths that guide the and their antimicrobial susceptibility. 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EndoJournal 2007;40:818-30 filled Root Canals by Using a Fluid Filtration Approach J 19. Estrela C. Accuracy of Cone Beam Computed Endod;(33)8:944-47 Tomography and Panoramic and Periapical Radiography 45. Teixeira FB, et al. Fracture resistance of roots end- Oral Health welcomes this for Detection of Apical Periodontitis. J Endo odontically treated with a new resin filling material. JADAoriginal article. 2008;34(3):273-279 2004;(135)5:646-652 20. Simon JHS, Enciso R, Malfaz JM, Rogers R, Bailey- 46. Sly MM, Moore BK, Platt JA, Brown CE. Push-out Perry M, Patel A. Differential diagnosis of large periapical bond strength of a new endodontic obturation system Part II: Untying the Gordian lesions using cone-beam computed tomography mea- (Resilon/Epiphany). J Endod. 2007 Feb;33(2):160-2 surements and biopsy. J Endod 2006;32:833-7 47. Williams C, Loushine R et al. A Comparison ofKnot: Back to the Egg will address 21. 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Dye extraction results on bacterial @ARTICLECATEGORY:594;74 oralhealth November 2009 www.oralhealthjournal.com