Introduction• Over the past decade, nickel titanium rotary

instrumentation, more reliable apex locators, ultrasonics,microscopic endodontics, digital radiography, newerobturation systems, and biocompatible sealing materialshave helped practitioners perform endodontic proceduresmore effectively and efficiently than ever before.

• All of these advances increase the incidence of single-visitendodontics in the dental clinics and the rational for thistreatment regime are less stressful and only one anesthesiais needed, which makes it very well accepted by thepatient, less time-consuming, reduces the risk ofinter-appointment contaminations, less expensive andmore productive for the clinician.

• Numbers of questions have been raisedregarding the one visit endodontics:

Is the same outcome achieved when we usedsingle visit regime rather than multiple visit forthe most of the cases?

Is the healing rate is the same in single andmultiple-visit endodontic treatment for infectedroot canals?

Are there any differences between single andmultiple-visit endodontic treatment inpost-obturation pain?

Advantages of single visit endodontics

• Minimizes the fear and anxiety.

• Reduces incomplete treatment.

• Lesser errors in working length.

• Restorative consideration.

• Convenience.

• Efficiency.

• Patient comfort.

• Reduced intra-appointment pain.

• Economics.

Disadvantages of single visitendodontics

• It is tiring for patients to keep their mouth open forlong duration.

• Mid-treatment flare-up may happens.

• Clinician may lack the proficiency to properly treat acase in single visit.

• Some cases cannot be treated by single visit.

Criteria of case selection

• Positive patient acceptance.

• Absence of anatomical interferences.

• Accessibility.

• Availability of sufficient time to complete the case.

• Pulp status.

Indications of single visit endodontics• Vital teeth.

• Fractured anterior where esthetics is the concern.

• Patients who require sedation every time.

• Non-surgical retreatment cases.

• Medically compromised patients who requireantibiotics prophylaxis.

• Physically compromised patients who cannotcome to dental clinics frequently.

Contraindications of single visitendodontics

• Teeth with anatomic anomalies such ascalcified and curved canals.

• Asymptomatic non-vital teeth with periapicalpathology and a sinus tract.

• Acute alveolar abscess cases with frank pusdischarge.

• Patients with acute apical periodontitis.

• Non-vital teeth and sinus tract.

• Patients with allergies or previous flare-ups.

• Teeth with limited access.

• Patients who are unable to keep mouth openfor long durations such as patients with TMJdisorders.

• A major goal of non-surgical root canal treatment(NSRCT) is the prevention or treatment of apicalperiodontitis, leading to the preservation ofnatural teeth.

• The presence of bacteria inside the root canalsystem results in the development of periapicallesions.

Treatment protocol differences between single and multiple-visit

endodontic treatment

• Traditionally, root canal treatment wasperformed in multiple visits, with theuse of extra disinfecting agents(intracanal dressing) besides theirrigants that is used during thecleaning and shaping procedure whichmainly aims to reduce or eliminatemicroorganisms and their by-productsfrom the root canal system beforeobturation.

• The most intracanal dressingresearched and widely used is thecalcium hydroxide Ca(OH)2 paste.Calcium hydroxide a strong alkalinesubstance, which has a pH ofapproximately 12.5.

• In an aqueous solution, Ca(OH)2dissociates into calcium and hydroxideions.

• The hydroxyl ion (OH-) is even smaller and canpenetrate through dentin to the cementum.Calcium hydroxide works by a hydrolysis reactionin which the (OH-) ion cuts protein chains andbacterial endotoxin into pieces as it breakschemical bonds. It breaking C-C bonds by theprocess of hydrolysis which represents thebackbone of proteins and endotoxin.

• However Ca(OH)2 was not capable of eliminatingall the bacteria, it helped to reduce the bacteriaremaining in the canal after the irrigation.

• The concept of single visit root canal treatment isbased on the entombing theory, which the largenumber of microorganisms removed duringcleaning and shaping and the remaining bacteriaentombed by the root canal obturation,therefore it will miss the essential elements to besurvive nutrition and space.

• In addition, the antimicrobial activity of thesealer or the zinc (Zn) ions of gutta-percha cankill the residual bacteria.

• Carefully conducted electron microscopic studies haveindicated that (it is from within the confines of the rootcanal system) bacteria initiate and maintain periapicalpathosis.

• Study: An advanced anaerobic bacteriological techniquehas been conducted by (JÖGREN et al. in 1997) toinvestigate the role of infection in the prognosis ofendodontic therapy by following-up teeth that had theirinfected canals were cleaned and obturated during asingle appointment.

Microbiological basis for endodontic treatment

• The teeth were followed for 5 years. They detected anumber of bacteria in 22 of 55 root canals.

• Complete periapical healing occurred in 94% of casesthat yielded a negative culture.

• Conclusion of this study:

The importance of completely eliminating bacteria from theroot canal system before obturation.

The completely eliminating bacteria cannot be reliablyachieved in a one-visit treatment because it is not possible toeradicate all infection from the root canal without the supportof an inter-appointment antimicrobial dressing.

• Another study: Tronstad et al. in 1987, examined eightasymptomatic periapical inflammatory lesions which wererefractory to conventional endodontic therapy in thepresence of bacteria. Access to the periapical lesions wasgained using an aseptic surgical technique. Microbiologicalsamples were taken from the soft tissue lesions and thesurface of the root tips. The samples were processed using acontinuous anaerobic technique.

• Bacterial growth was evident in all samples. Two lesionsexclusively yielded anaerobic bacteria and 5 lesions wereheavily dominated by anaerobes.

• Conclusion: Their findings clearly showed that anaerobicbacteria are able to survive and maintain an infectious diseaseprocess in periapical tissues.

• In an infected vital pulp due to a caries exposure, theinfection is normally found only at the wound surface,where it has resulted in a localized inflammatoryresponse.

• This means that more apically, and in particular in themost apical portion of the tissue, bacterial organismsare usually not present.

Status of the pulp

• The aim of root canal treatment in this case is tomaintain sterile apical conditions in order to optimizethe healing potential.

• On the other hand an infected necrotic pulp producesan apical inflammatory lesion and the aim of root canaltreatment in is to eliminate the microorganisms fromthe canal to promote healing of apical periodontitis.

• Debridement of the root canal by instrumentation andirrigation is considered the most important single factorin the prevention and treatment of endodontic diseasesand there is a general agreement that the successfulelimination of the causative agents in the root canalsystem is the key to health.

• Study: (Byström and Sundqvist in 1983) Sodiumhypochlorite (NaOCl) irrigation (0.5%) plus mechanicalinstrumentation rendered 33% of the canalsbacteria-free after the first appointment.

Bacterial elimination

• Even with the most modern instrumentation techniques(using of a rotary instrumentation technique) attainment ofcomplete bacterial elimination would be farfetched.

• Although irrigation with NaOCl provides a number offeatures attractive to root canal therapy, it appears that it isnot possible to attain complete bacterial elimination by thisadjunctive measure.

• Therefore intracanal medication, specially calciumhydroxide, has been widely used in attempts to kill anybacteria remaining after instrumentation and irrigation.

• Although the use of intracanal medication will lower thebacterial count in infected root canals, it fails to obtain thetotal elimination of bacterial organisms on a consistentbasis.

• The objective of root canal treatment on necrotic teethshould be not only the elimination of living bacteria butalso the inactivation of the toxic effects of bacterialendotoxins.

• The lipopolysaccharide (LPS), is a powerful endotoxincapable of having a strong toxic action over theperiapical tissues.

Bacterial endotoxins elimination

• LPS is released during disintegration, multiplication, orbacterial death and is capable of penetrating into theperiradicular tissues, acting as endotoxin in the hostorganism and leading to periradicular inflammation andbone destruction.

• The lipid A is the bioactive component of LPSresponsible for the majority of the immunoresponse.

• The accumulation of bacteria components in an infectedarea, particularly endotoxins can stimulate the releaseof proinflammatory cytokines.

• The inflammatory tissue present in periradicular lesionsis populated predominantly by a macrophage, which isthe major source of interleukin-1b (IL-1b), and almostthe exclusive producer of tumor necrosis factor a(TNF-a) in the presence of bacteria or LPS

• The irrigation solutions were ineffective against LPS,while the intracanal medication dressing with Ca(OH)2appeared to inactivate the cytotoxic effects of theendotoxin.

• Study: Khan et al. in 2008, tested the hypothesis thatCa(OH)2 denatures IL-1 alpha, TNF-alpha, and CGRP.

• Human IL-1 alpha (0.125 ng/mL), TNF-alpha (0.2 ng/mL), andCalcitonin Gene-Related Peptide (CGRP) (0.25 ng/mL) wereincubated with Ca(OH)2 (0.035 mg/mL) for 1-7 days.

• At the end of the incubation period, the pH of the sampleswas neutralized, and the concentrations of the mediatorswere measured by immunoassays.

• The analyzed data indicated that Ca(OH)2 denatures IL-1 alpha,TNF-alpha, and CGRP by 50-100% during the testing periods

• Conclusion: They concluded that denaturation of these pro-inflammatory mediators is a potential mechanism by whichCa(OH)2 contributes to the resolution peri-radicular periodontitis.

• Postoperative or intraoperative flare-up and pain areoften the measure of the success or failure of single visittreatment, although pain during treatment has beenproved to have no effect on long-term outcomes.

• Postoperative pain at the mild level is common in rootcanal treatment which may be the result ofover-instrumentation, over-filling, passage of medicineor infected debris into the periapical tissues, damage ofthe vital neural or pulp tissues or central sensitization.

Postoperative pain

• The preponderance of the researches to date whichhave shown no significant difference in postoperativepain has been found when one-visit RCT was compared

with two-visit treatment, especially in teeth with vitalpulps.

• The simplest way to compare both treatment options is toanalyze them using a healed or not healed outcome.

• The short- or long-term follow-up of the bone radiographicimage and size of the lesion is the most commonly usedtechnique to evaluate the healing, usually based on the PAIscore developed by Orstavik et al. in 1986: Grade 1: Normal periapical structures.

Grade 2: Small changes in periapical bone structure.

Grade 3: Changes in periapical bone structure with some mineral losscharacteristic of apical periodontitis.

Grade 4: Periodontitis with well-defined radiolucent area.

Grade 5: Sever periodontitis with exacerbating features and boneexpansion.

Healing rate of single-versus multiple-visit endodontic treatment for infected canals

• Numerous studies evaluating the effectiveness ofsingle-versus multiple-appointment root canal treatment

have been published, which reported no significantdifferences in effectiveness (healing rates) between thesetwo treatment regimens.

• Unfortunately, endodontic treatment success is often poorlydefined. As mentioned earlier, postoperative orintraoperative flare-up and pain were the only measure ofthe success or failure used to evaluate single visit treatment.

• The aim of the endodontic therapy to achieve theresolution of the disease means elimination of theetiology, which means elimination of bacteria. Thereforeevery time we can get free microorganisms canals wecan perform single visit root canal treatment.

• The canals with vital pulps can (in principle) be regardedas free of bacteria at the initiation of treatment.

• Thus, provided a strict aseptic technique is utilized andenough time is available for all treatment steps to beperformed optimally, the permanent filling of the canalmay take place on the first visit.

Conclusions

• In teeth with necrotic pulp and apical periodontitis and withthe complex anatomy of teeth and root canals creates anenvironment that is a challenge to the complete cleansing insingle visit, therefore the multiple appointment proceduremaybe is more effectiveness to achieve more bacterianegative canals.

• In addition to killing bacteria, intracanal medicaments mayhave other beneficial functions. Calcium hydroxideneutralizes the biological activity of bacteriallipopolysaccharide and makes necrotic tissue moresusceptible to the solubilizing action of NaOCl at the nextappointment.

• Regardless of the number of sessions, an effectivebacteriological control is mandatory.

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