ORIGINAL RESEARCH

Effectiveness of different intracanal irrigation techniques inremoving intracanal paste medicamentsKenny Chou, BOralH, GDipDent1; Roy George, MDS, PhD1; and Laurence J. Walsh, DDS, PhD2

1 School of Dentistry and Oral Health, Griffith University, Southport, Queensland, Australia

2 School of Dentistry, The University of Queensland, Brisbane, Queensland, Australia

Keywordscalcium hydroxide, irrigation, medicament, root

staining, tetracycline.

CorrespondenceDr Roy George, School of Dentistry and Oral

Health, Griffith University, Gold Coast Campus,

Southport, Qld 4215, Australia. Email:

drroygeorge@gmail.com

doi:10.1111/aej.12055

Abstract

This study aimed to compare the effectiveness of different intracanal irriga-tion techniques in removing intracanal medicaments prior to obturation. Atotal of 168 single roots were prepared with ProTaper® rotary files andmedicament pastes applied (Ledermix®, Odontopaste®, Doxypaste andPulpdent®), left in for 2 weeks, then removed using filing followed by oneof four methods: irrigation with an open-ended notched irrigation needle(Appli-Vac) either at the working length or 5 mm from the canal orifice, orthe Max-I-probe or EndoActivator® at the working length. Following theremoval of medicaments, the roots were split into two and the internal sur-faces photographed, for digital image analysis of the overall percentage ofresidual medicament. With the exception of canals irrigated 5 mm apical tothe root canal orifice, all four irrigation techniques achieved an average of95% for removal of Ledermix®, Odontopaste® and Doxypaste. Calciumhydroxide paste was the most difficult medicament to remove, with no dif-ference between irrigation techniques. Up to 27% of the Pulpdent® materialremained after irrigation. No irrigation technique could completely removeall traces of medicaments. The position of the irrigational needle and the typeof medicament used are key factors, which influence the effectiveness ofirrigation in removing medicaments.

Introduction

In multivisit endodontics, medicaments are placedbetween visits to help reduce levels of bacteria. Themost common medicaments used in the Australasianregion for inter-visit dressings are pastes based on calciumhydroxide (e.g. Pulpdent® paste, Watertown, MA, USA)or steroid pastes containing antibiotic pastes (1).Examples of the latter include pastes containingclindamycin (Odontopaste®, Australian Dental Manufac-turing, Brisbane, Queensland, Australia), demeclocyclinehydrochloride (Ledermix®, Lederle Pharmaceuticals,Wolfratshausen, Germany) or doxycycline (DoxyPaste,Ozdent, Castle Hill, New South Wales, Australia). In paststudies, we have shown the influence of such pastesremaining in the root canal on the subsequentdiscolouration of root dentine, and their differentialresponse to intense light (2).

When medicaments are used between visits, a naturalconcern that arises is the extent to which all traces of themedicament can be removed from the canal, so as not tointerfere with the placement, setting or polymerization ofthe materials used for the final root canal filling. Typically,medicament pastes are removed by physical removal ofthe bulk of the paste using an endodontic file, followed byseveral cycles of irrigation with sodium hypochlorite orethylenediaminetetraacetic acid (EDTA). It could beexpected that better irrigation technologies, such as side-vented needles, and more apical placement of irrigatingneedle tips would enhance the removal of remnants ofpastes (3). Based on past work examining removal ofdebris created by files, mathematical modelling has pre-dicted that optimal placement of open-ended irrigationneedles should be 1 mm from the working length (4).Lower efficiency has been shown for removing bacteriawhen tip placement is 5 mm from the canal orifice (5).

Aust Endod J 2014; 40: 21–25

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21© 2013 Australian Society of Endodontology

The success of an irrigation technique can also be influ-enced by the pattern of fluid movement that creates shearforces along the canal walls, which is determined by theflow rate of the irrigant, and the relationship betweeninternal diameter of the root canal and the diameter ofthe irrigating needle. Bronnec et al. reported that shapingroot canals improved both the penetration and exchangeof irrigants inside the root canal system (6). Severalimprovements in design of irrigation needles have beenintroduced to improve the efficiency and safety of rootcanal irrigation. Examples include the Max-I-Probe(Dentsply Rinn, Elgin, IL, USA) and the EndoActivator®(Dentsply Maillefer, Ballaigues, Switzerland). The latter isa sonic agitator that uses non-cutting polymer tips toincrease fluid flow within the root canal. Current litera-ture into the efficacy of the EndoActivator® is inconsis-tent, with some studies reporting no additional benefitover conventional irrigation techniques (7–11).

No past studies have examined the challenge of remov-ing medicament pastes from root canals. The conse-quences of leaving large amounts of medicament pastesin the canals can be significant, in terms of darkening oftooth structure, in the case of Ledermix® (2). Calciumhydroxide materials are typically formulated using awater base with a cellulose-type thickener, making themdifficult to remove, whereas steroid antibiotic pastes typi-cally use a vehicle containing polyethylene glycol withlittle or no water. The purpose of this study was toexamine the efficiency of different irrigation techniquesfor removing medicaments from the internal root canalwalls, as would be required prior to obturation, by mea-suring the extent of remaining material on the canal wallsusing digital image analysis.

Materials and methods

Sample preparation

A total of 168 single-rooted permanent extracted teethwith fully formed apices, and free of root resorptionand previous root fillings were collected followingethics committee approval. The teeth were stored in tapwater containing 0.1% thymol to prevent bacterialgrowth, and then sectioned using a diamond disc at thecementoenamel junction to create a root length of11–13 mm. The working length was established by insert-ing an International Organization for Standardization(ISO) size 8 K-file (Dentsply Maillefer) until it was visibleat the apical foramen and then withdrawing by 1 mm.Canals were prepared to a length 1 mm short of theapex using F3 size nickel-titanium rotary ProTaper® files(Dentsply Maillefer), under constant irrigation with alter-nating 1% NaOCl and 15% EDTA plus Cetavlon (EDTAC)solutions. A final rinse sequence involving EDTAC for

2 min was performed to ensure complete removal ofsmear layer. The canals were dried with paper points, andthe roots divided randomly into one control group (with8 roots, which did not receive any paste), and 16 treat-ment groups of 10 roots each, as shown in Table 1.

Placement of medicaments

All canals except those in the control group werefilled completely with the respective medicaments(Ledermix®, DoxyPaste, Odontopaste®, Pulpdent®)using a 5 mL syringe with a small tip placed apically as faras possible. This procedure was undertaken undersubdued lighting conditions due to the light sensitivenature of the Ledermix® (12). Injection of the medica-ment pastes was continued until excess paste was seen toextrude from the apical foramen, and the bulk of the rootcanal then backfilled to the level of the cut surface. Excesspaste present on the cut root surface or at the apicalforamen was removed immediately using an ethanolwipe. The apical foramen was then sealed with two layersof dental utility wax to prevent subsequent apical extru-sion of fluid (6). The prepared roots containing medica-ments were then kept in complete darkness at 37°C and100% humidity for 4 weeks.

The content of the pastes was as follows. Pulpdent®paste contains 35% calcium hydroxide with bariumsulphate in methyl cellulose and water. Ledermix® pasteis composed of a mixture of polyethylene glycol, water,various excipients and fillers (zinc oxide, calcium chlo-ride, triethanolamine and sodium sulphite), and the twoactive agents demeclocycline hydrochloride 3% andtriamcinolone 1%. There is a similar polyethylene glycolbase in Doxypaste (which contains doxycycline hyclate)and Odontopaste® (which contains clindamycin) as thatused in Ledermix®.

Removal of medicaments

To replicate clinical practice, the bulk of the medicamentpaste was first removed using a handheld ProTaper®F3 file introduced in the canal briefly, and rotated one-half turn. The canals were then rinsed using EDTA andthen NaOCl, each for 1 min in sequence. These irrigantswere delivered using either a conventional 27 gaugeMonoject™ open-ended notched needle tip (KendallHealthcare, Mansfield, Queensland, Australia) or a side-venting Maxi-I-Probe (Fig. 1). The conventional needletip was placed either 1 mm short of the working lengthor 5 mm from the canal orifice, and the needle tipmoved manually in an up–down action over 2 mm toobtain gentle manual agitation. The Max-I-Probe andEndoActivator® were both used at the working length,

Intracanal Irrigation and Medicament Removal K. Chou et al.

22 © 2013 Australian Society of Endodontology

with 1 min each for NaOCl and then EDTAC. TheEndoActivator® was fitted with an ISO 25 size disposableplastic tip.

Root division

After the removal of medicaments, each root canal wasleft to dry for 1 day at room temperature, and thenthe roots were exposed to artificial light from a recharge-able 35W Xenon HID spotlight (Electus Distribution,Rydalmere, New South Wales, Australia) for 10 min oneach side. This step assisted in making a clear distinctionof remnants of medicaments. Each root was sectionedvertically into two halves by carefully grooving theroots vertically into dentine using a thin diamond disc(Superflex D915DF/22.0, Stoddard, Hertfordshire, UK),stopping short of the root canal. The roots were then splitusing a small chisel inserted into the groove.

Digital image analysis

The length of each split root was photographed with aNikon Coolpix digital camera (Nikon, Tokyo, Japan)attached to an Olympus stereomicroscope (Tokyo,Japan), with the image showing the entire length of theroot. Images were analysed using Adobe Photoshop®software (Adobe Systems Software, Ireland) to quantifythe proportion of pixels for residual medicament com-pared with the total area of the root canal wall, using themagnetic lasso tool. Data were then expressed as a per-centage of the pixel count, with 100% representing medi-cament paste still present across the entire root canalarea. Datasets were subjected to one-way analysis of vari-ance to explore the independent effects of medicamenttype and irrigation method. All datasets passed normalitytests, allowing parametric analyses to be performed.

Results

Overall, none of the techniques used was able to removemedicaments completely; thus, no samples have aresidual percentage score of zero (Table 1). When anTa

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Figure 1 Irrigating needles used in the study. (a) MonojectTM needle tip

showing an open tip. (b) Maxi-I-Probe needle tip showing side vents and a

closed tip.

K. Chou et al. Intracanal Irrigation and Medicament Removal

23© 2013 Australian Society of Endodontology

open-ended irrigating syringe was used at workinglength, the calcium hydroxide paste Pulpdent® wassignificantly (P < 0.05) more difficult to remove thanother materials. On average, more than three times morematerial remained in the root canal for calcium hydrox-ide paste than for the steroid antibiotic pastes (Fig. 2).

There was a significant effect seen for needle positionwith the open-ended needle, since when this was placed5 mm from the orifice and thus 4 mm from the workinglength, Ledermix® then became more difficult to removethan Doxypaste or Odontopaste® (P < 0.05), and wasremoved as poorly as Pulpdent®.

Calcium hydroxide paste was significantly more diffi-cult to remove than other medicaments from the rootcanal when using irrigation delivered with the Max-I-Probe at working length (P < 0.001). The average per-

centage of medicament left with Pulpdent® was almost10 times higher than other medicaments.

When the Max-I-Probe was used, all three steroid anti-biotic pastes were removed better than calcium hydrox-ide paste (P < 0.001), with nine times less residueremaining. Likewise, with the EndoActivator®, calciumhydroxide paste was the most difficult material to remove(P < 0.001), with a difference in the amount remaining ofsome 25 times. Doxypaste was the easiest material toremove with the EndoActivator®.

Comparing the different irrigation methods, forcalcium hydroxide paste no method was superior. For thesteroid antibiotic pastes, the EndoActivator® was signifi-cantly better than the Max-I-Probe, and the conventionalopen-ended needle used at 1 mm from the workinglength, which gave similar outcomes.

Discussion

Overall, the results of this study show that none of theirrigation techniques could guarantee 100% removalof all medicaments, although irrigation with theEndoActivator® comes closest to the ideal performancein terms of removing the steroid antibiotic pastes. Thecalcium hydroxide paste material Pulpdent® was themost difficult medicament paste to remove, with anaverage of 27% of the root canal surface still covered afterfiling followed by irrigation. This finding expands onearlier work that showed manual filing of canals was notvery effective at removing calcium hydroxide pastes (13).This likely reflects characteristics such as the thick viscos-ity of the paste and its cellulose filler, and the possibility ofpartial conversion of some of the calcium hydroxide tocalcium carbonate over time because of reaction withambient carbon dioxide.

Two practical suggestions flow from these consider-ations. On the one hand, if the vehicle in the calciumhydroxide paste was changed from water with carboxy-methyl cellulose to an alternative material, it maybecome easier to remove by irrigation. This notion shouldbe explored in further studies. Alternatively, one coulduse more aggressive methods of irrigation or fluid agita-tion such those created by ultrasonic instruments orpulsed lasers, which could create more intense shearforces within the fluids in the root canal (14–16).

The results of the present study emphasize the impor-tance of placing the irrigation device correctly. Irrigationperformed at a distance of 5 mm from the orifice was themost ineffective technique for removing medicaments.This is consistent with the view that the effects of irriga-tion with plain needles is limited to 1–2 mm from the tipof the irrigation needle (17), and that the apical third

Figure 2 Images showing canals medicated with Odontopaste® and

Pulpdent® following irrigation with conventional irrigating needle (a and

b) and EndoActivator® (c and d) to working length.

Intracanal Irrigation and Medicament Removal K. Chou et al.

24 © 2013 Australian Society of Endodontology

region of the root canal is the most difficult area to irrigatethoroughly (18).

Conclusions

None of the irrigation techniques tested in this studycould remove all medicaments without any residuesremaining. The presences of residual materials on thecanal walls could affect the quality of the seal createdduring obturation of the canal and could also contributeto discolouration of roots. Because Pulpdent® paste is adifficult medicament to remove, efforts should be made tocorrectly place irrigation devices and to use agitation toenhance the removal of medicaments.

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