interirationo/Endodontic Journa) (1993) 233,273-283

Management ofthe resect^ root end: a clinical reviewJ. L. GUTMANN & T. R. PITT FORD*Department of Restorative Sciences, Baylor College of Dentistry, Dallas, Texas, USA; and 'Department of Conservative

Dental Surgery, United Medicd and Dental Schools, Guy's Hospitd, London, UK

Summary

Carefiil management of the resect^ root end duringendodontic surgery is critical to the overaU success ofthecase. After resection, the root structure presents withmultiple anatomical variations and ccmslderadons atboth a macrosc<q>ic and microscopic level, Itiese includeroot outline, canal anatomy, dentinal tubule configur-ation, presence erf' a smear layer and root canal fillingmaterial. Proper assessment of these variables will dic-tate the best methods for root-end management, alongwith the attainment of an anatomically compatible rootface for optimal healing ofthe periradicular tissues.

Keywords: dentine, endodontic surgery, resection, rootend, smear layer.

1985). Little support presently exists for these rationalesas the sole determinants for root-end resection.

Removal of anatomical variations

Commonly cited entities include severe canal curves,lateral and accessory canals, apical bifurcations ordeltas, and calcifications (Johns 1977. Oliet & Grossman1983, Bames 1984, NichoUs 1984), These indicationsexist only when the anatomical variations have beenimplicated in case failure or are strongly suspected aspotential contributors to failure. The validity of theirrationale occurs only after attempts at quality non-surgical root canal treatment have failed.

Introduction

Endodontic surgery encompasses multiple specific pro-cedures designed to manage the compromised root sys-tem and periradicular tissues. A commonly performedprocedure is root-end resection, often referred to asapicoectomy or apicectomy (Gutmann & Harrison1991), The term root-end resection refers specifically tothe removal ofthe apical portion ofthe root. The purposeof, and indications for, root-end resection are varied, andthe rationale for its use resides in each individual case.

From an historical perspective, the surgical literaturesince the late 1800s has supported the following ration-ales for this procedure, although many of those cited mayor may not be valid in contemporary endodontics.

Removal of pathological processes

This has included root resorption, fractured root tips,reactive or pathological tissues and potentially infectedcementum and dentine at the root apex (Weaver 1947,Buch & Waite 1962, Leubke et d. 1964, Cummings et al.

Correspondence: James L, Gutmann DDS, Professor and Chairman,Department of Restorative Sciences, Baylor College of Dentistry, 3302Gaston Avenue, Dallas, Texas 75246, USA,

Removal of operator errors in canal preparation

Despite the skill of the clinician, it is not uncommon forledges, blockages, zips, perforations and separated instru-ments to occur (Nicholls 1962, diLauro et d. 1980, VanWelsenes & Van der Kwast 1983, Panzoni 1985), Theseerrors will only serve as valid rationales for surgicalintervention if there is failure following attempts tonon-surgically rectify the pn)blem and patient signs orsymptoms persist.

To enhance removal ofthe soft tissue lesion

Often, root-end resection will facilitate access to deeplyplaced granulation or cystic tissues (Gerstein 1985,Gutmann & Harrison 1985),

Access to the canal system

Curettage alone will not allow apical entry into a canalsystem which requires thorough cleaning, shaping andobturation, when it has not been properly managedthrough the crown (Vasiliu 1977, Oliet & Grossman1983, Messing & Stock 1988). Therefore, a variable

273

2 74 /, L, Gutmann 6 T. R, Pitt Ford

amount ofthe root apex must be removed to achieve thispurpose, depending on root and canal anatomy.

Evaluation ofthe adaptation ofthe catud fillingmaterial

Removal of the root apex allows the clinician to assessthree dimei^onally the quality of the adaptation andnature ofthe root canal filling material (Leubke 1974.Harrison & Todd 1980) and to determine the need for aroot-end flUing.

To enhance the adaptation ofthe root canal filhngmaterial

This is probably the most commonly cited reason forroot-end resection, especially when the canal systemcannot be cleaned, shaped and obturated through thecrown of the tooth (Herd 1968, Leubke 1974, Johns1977),

Reduction of root apices which havefenestrated thebone

This occurs primarily in maxillary premolars and molars.With pulpal demise, the periosteum, which overlies rootswith fenestrated bone, becomes inflamed. Root-endresection contours the root tip to lie within its bonyhousing (Gerstein 1985, Ruiz de Termino Malo et al.1986),

against resection were suspect, periradicular curettagewas still advocated as a terminal, definitive procedure.In essence, the real c a u ^ of the periradicular problemwas invariably not being addressed, as the soft tissuesurrounding the root was only the result of continuedirritation coming from the root canal system. Even incases which appear radiographically acceptable, clean-ing and shaping ofthe canal system is often below accept-able levels. Therefore, contemporary views support theneed for root-end resection in most cases as being necess-ary to achieve the goals of the surgical procedure. Theextent to which the removal ofthe root end should occur,will be dictated by the following factors (Gutmann &Harrison 1991),

(1) Access and visibility to the surgical site,(2) Position and anatomy of the root within the

alveolar bone.(3) Anatomy of the cut root surface relative to the

number of canals and their configuration.(4) Need to place a root-end filling into sound root

structure,(5) Presence and location of procedural errors, e.g,

perforation.(6) Presence of an intra-alveolar root fracture.(7) Presence of any periodontal defects,(8) Anatomical considerations, such as root proximity

to adjacent teeth, or level of remaining crestalbone,

(9) The presence of significant accessory canals. Rootswith a likelihood of these anatomical aberranceswould be likely to receive more extensive resection.

Exploration for aberrant canal anatomy or rootfractures

The resection of the root end enables direct vision of anycanal aberrances or imsuspected root fractures (Taylor &Bump 1984, Gutmann & Harrison 1985, Kirschner1987).

Consequaices of root-end resection

Whilst substantial reasons exist for root-end resection,many controversies surround this procedure, especiallyas it relates to the amount of root removed. Historically,some authors have discouraged root-end resectionbecause it opened daitinal tubules which might housebacteria, tooth stability in the alveolus would be com-promised, and cemental healing might not occur on theexposed dentine. Whilst the validity of these arguments

Resection technique

The technique of root-end resection uses a lingual to labialbevel, angled to the coronal aspect of the tooth. This isdesigned for surgical access and visibility. Angles for rootbeveis have been suggested to range from30°to45°in theline of sight, although variables iii each case will deter-mine the exact degree of cut (Luks 1956, Rud &Andreasen 19 72, Cambruzzi & Marshall 1983, Gutmann& Harrison 1985). From the anterior to the posterior, theangle ofthe bevel will gradually go from a direct coronal-buccal cut to one that is accentuated coronally andmesio-buccally placed. These angles of resection andtheir use will also be determined by the root inclinationand curvature, number of roots, thickness of bone andposition ofthe root in the bone and arch.

The root end can be resected and beveUed in one of twoways. Once the root end has been exposed, the bur and

Management ofthe resected root end 275

handpiece are positioned at the desired angle and theroot is shaved away, beginning from the apex, cuttingcoronally. The bur is moved from mesial to distal at thedesired angle, shaving the root smooth and flat, andexposing the entire canal system and root outline. Thisapproach allows for continual observation of the rootend during the cut.

The second technique of resection is to predeterminethe amount of root end to be resected. This approachhowever may remove more root structure than isessential. If chosen, the bur and handpiece are positionedat the ideal angle and the apex is resected by cutHngthrough the root from mesial to distal. Once the segmentis removed, the root face is gently shaved with the bur tosmooth the surface and ensure complete resection andvisibility of the root face. This technique works wellwhen an apical biopsy is desired or to gain access tosignificant amounts of soft tissue located lingual to theroot.

Anatomy ofthe resected root surface—macroscopic considerations

The appearance of the root face following root-endresection will vary, depending upon the type of bur used,the external root anatomy, the anatomy of the canalsystem exposed at the particular angle of resectionchosen, and the nature and density of the root canalfilling materiaL

Bur type

Various types of bur have been recommended for root-end resection, such as round burs, straight fissure burs,diamond burs, and cross-cut fissure burs (Gutmann &Harrison 1991), Each will leave a characteristic anatom-ical imprint on the root face, from rough-grooved andgouged to regularly-grooved and smooth. To date, nostudy has clearly defined the advantages of one type of burover the other, with regard to surface morphology ortissue healing response. For years, however, clinical prac-tice has favoured a smooth flat root surface (Moorehead1927, Sommer 1946, Trice 1959, Gutmann 1986),

Exterrud root anatomy

The external root anatomy will determine the ultimateshape of the cut root end, as oval, round, dumb-bell

shaped, kidney-bean shaped, or tear-drop shaped. Out-lines will vary depending on the tooth, angle ofthe beveland position ofthe cut on the root. Once cut, however, theentire surface must be visible. If visibility or access isimpaired, or the root po^esses an imusual cross-sectionaloutline, 1 % methylene blue dye can be plared on the rootsurface to help identify Ihe periodontal ligament thatsurrounds the root (Cambruzzi & Marshall 19 8 3), A smallcotton pellet containing dye is wiped over the root face for5-10 s. Subsequently the area is flushed with sterilewater or saline. The dye will stain the periodontal liga-ment dark blue, highlighting tfie root oufline (Fig. 1).A potential drawback to this technique may be thedeposition of cotton fibres on the resected surface or inthe osseous wound. Residual remnants of cotton fibreshave been shown to induce a foreign-body reaction inthe healing tissues (Gutmann & Harrison 1991).

Anatomy ofthe canal system

The shape ofthe exposed canal system will vary depend-ing on the angle of the bevel and the canal anatomy atthe level ofthe cut. Canal systems will generally assumea more elongated and accentuated shape as the angle ofthe bevel is increased buccaily (Fig, 2). Often, canals willbe irregular and extend further than anticipated, thus,additional root structure may have to be removed toensure exposure ofthe entire system.

Root canal filling material

In addition to the variations with different materials,e,g, gutta-percha, silver cones, pastes, the nature of thefilling technique, e.g. lateral condensation, vertical con-densation, or thermoplastic fillings, will provide a differ-ent view ofthe canal contents and their adaptation to theroot canal walls (Fig. 3). Likewise, the different bursadvocated for resection will create discrepancies in thesurface of the filUng material and adaptation to the canalwalls. For example, coarse diamond burs will tend to ripand tear at the gutta-percha root canal filling, spreadingthe gutta-percha over the edge of the canal aperture andonto the resected root face (Fig, 4). Invariably this willcreate gaps between the originally adapted gutta-perchaand the root canal wall. Similar findings are noted withfissure burs and round burs (Gutmann & Harrison1991), In order to prevent this, surface finishing withan ultra-fine diamond is recommended (Ultrafine No,862-012 diamond bur; Brasseler, Savannah, GA, USA;Komet, Lemgo, Germany).

276 ].l. Gutmatm & T. R, Pitt Ford

mmyi?^

Fig. 1, Outline of resected root, in vitro, deiineated by staining of theperiodontal ligament with methylene blue.

Fig. 2. Elongated canal on resected root surface deiineated withmethylene blue. Note extension (arrows) beyond gutta-percha filling.

Clinical considerations

The complete root face must be identified and examinedsubsequent to resection. The examination is done with afine, sharp probe, e,g. DG 16/17 (Hu Friedy, Chicago, IL,USA), guided around the peripher)' of the root and theroot canal. The presence of additional foramina, anasto-moses between foramina, fracture lines, and the qualityof the apical adaptation of the root canal filling must bechecked (Fig, 5), If methylene blue has been used, it willalso hcLve a tendency to stain the periphery of the canalsystem and highlight fracture lines. Nitromersol, adental disinfectant which stains reddish-brown, can alsobe used when examining the root face or a ibre-opticlight can be aimed at or behind the root end to enhanceiTsibility (Arens et d. 1981). If these methods do notwork, it may be necessary to remoFe additional rootstructure to identify the canal system or, in the case of afracture line, to enhance its direction and extent. Oncethe surface extent ofthe canaJ system has been identified.

and it is determiBed that tbere is uncleaned or unlilledspace, a root-end preparation is made with a bur or withan ultrasonic tip to clean the apical extension of thecanal space and to create a caiity for obturation.

Anatomy ofthe resected root surface—microscopic considerations

Dentinal tubules

The consequence of exposing resected dentinal tubules tothe periradicular tissues has been a controversial issuefor many years. Claims were made that ideaJ healingcould not occur against the tubules in the form of layeredcementum and periodontal ligament (Barron etal. 1947,Pearson 1949, Curson 1966, Wakeley & Simon 1977).However, it iias been shown that cementum can reformover the resected tubules and that a periodontai encap-sulation with varying degree of fibre attachment can

Management of the resected root end 277

, • • . > • " • . • • , ;

- • : . - :

i '

Fig. 3. (a) Appearanceof laterally condensed gutta-percha cones after resection. Note lack of condensation and large amount of root canal sealer,(b) Resection of vertlcalh' condensed thermoplasticized gutta-percha.

occur (Coolidge 1930, Herbert 1941. Blum 1945, Smith1967, Rowe 1967, Andreasen 1973, Craig 1990).

A second controversy is that exposure of the dentinaltubtiles would expose the periradicular tissues to bac-teria entrapped in the tubules (Fawn 1927, Ross 1935,Castenfeldt 1939), However, no correlation could beshown by Andreasen &Rud{1972) between the presenceof micro-organisms in the dentinal tubules and the degreeof periradicular inflammation. Likewise, because thenumber of tubules in the apical third would be signifi-cantly reduced in both number and patency, with ageingand sclerosis (Fig. 6) (Carrigan et al 1984. Ichesco et al.1991), coupled with root-end resection, this would tendto reduce the number of bacteria in the region signifi-cantly, especially since the majority of bacteria in theapical third have been shown to be located immediatelyadjacent to the root canal system (Jolly & SuOivan 1956.Shovelton 1964) and good canal cleaning and shapingwould tend to eliminate them from this area. Although

bacteria retained in the root canal sj'stem has been impli-cated in endodontic failure (Lin et al. 1991) and may,therefore, have access to the periradicular tissues foUow-ing resection, Nicholls (1965) has taken an oppositevie^v stating that, 'the exposure of dentinal tubulesivhich may have been contaminated at their pulpal ends,although sometimes constituting a criticism of apicectomyin the past, is probably of little or no significance.*

A third area of concern foUoiving tubule exposure isthe possibility that these channels may seri'e as a directcourse of contamination from unclean root canalsinto the periradictilar tissues, especially if there iscoronai leakage Into the root canal system. Tidmarsh &Arrowsmith (1989) have sho%vn that root ends resectedfrom 45° to 60° have as many as 28 000 tubules mm^-at a point Immediately adjacent to the canal. At thecemental-dentine junction, an area which may com-municate with the root canal even in the presence of aroot-end filling, an average of 13 000 tubules mm^*

78 J. L. Gutmann & T. R. Pitt Ford

Fig. 4. (a) Root end resected with coarse diamond bur. Note smearing ofthe gutta-percba onto the resected surface, (b) SEM shows smearing ofgutta-percha tags and gaps between the root canal filling and wall(bar=0,1 mm).

were found. Likewise, owing to angular changes io thetubules at the apex, there could be patent communi-cation with the main canal if the depth of the root-endpreparation in the buccal aspect ofthe cavity was insuf-ficient to compensate for these anatomical variations(Vertticci & Beatty 1986, Beatty 1986). Recently,Ichesco et al. (1991) have shown that root-end resec-tions in older teeth evidenced less leakage than that seenin teeth from younger patients; this corroborates withthe findings of sclerosis and reduced patency in the apicaldentinal tubules (Carrigan et al. 1984). It was suggestedthat if the apical ramifications commonly found in youngteeth could be dismissed as a rationale for root-end re-section, the resection would be inadvisable owing to thepatency ofthe apical dentina! tubules.

Fourth, the presence of a contaminated smear layer,containing microorganisms and tisstie debris, over the

resected root end may serve as a source of irritation to theperiradicular tissues, primarily preventing the intimatelayering of cementum against the resected tubules. Whilethis concern is primarily clinical in nature and has notbeen demonstrated in human specimens, short term ani-mal studies io which vital, uncontaminated teeth weretreated endodontically followed by root-end resection andsmear layer removal have shown favourable cementalapposition (Craig 1990). At the same time, the smearlayer may actually block the tubules and serve as a sourceof obturation ofthe potential avenues of communication,especially with tubules contaminated with bacteria orthose exposed to oral fluids over long periods of time.Experiments designed to evaluate these parameters areessential, because there is no unequivocal data to supportthe proper management of the smear layer on theresected root surface.

Clinical considerations

Depth and type of root-end preparation

In order to seal the potential avenues of communi-cation from the resected root end to the canal systemadequately, a root-end preparation should be made intothe root to the coronal extent of the resected apicaltubules. This wiil vary from case to case, but generally adepth of 2 ^ mm would be sufficient (Taylor & Doku196]. Rud & Andreasen 1972. Barry et al 1975). Thiscan either be made with a rotary bur. such as invertedcone or round bur (ISO size 008) at high- or low-speed, orwith specially angulated tips adapted for use on an ultra-sonic unit (ENAC, Osada Electric Co., Los Angeles, CA,USA). This approach to root-end preparation assumesthat a standard type of filling material, such as amalgamwith varnish, will be placed. However, the approach toand the design of the preparation may vary if othercontemporary restorative materials are used. While thepurpose ofthe paper is not to address these materials, thepractitioner must take these potential variations intoaccount during root-end preparation.

Recent enhancements io apical root-end preparationhave resulted from the development of 'ultrasonic retro-tips' (Excellence in Endodontics, San Diego, CA, USA)(Carr 1990). These small, angled tips have been advo-cated for the ultrasonic development of apical prep-arations parallel to the long axis ofthe root after minimalroot-end resection. Their use in the debridement andenlargement of canal anastamoses and irregularitiescommonly found in molar roots has received particular

Managetnent of the resected root etid 2 79

f-

Fig. 5. Resected root ends showing anatomical variations, (a) Canals and anastomosis visible, (b) Poor gutta-perchacondensation and canal extension; fracture visible in tlie root (arrow), (c) Palatally extended canal space (arrows) of mesialbuccal root of a maxillary first molar, (d) Gutta-percha ailing of canal and small portion of anastomosis. Note necrotictissue debris in canal extension (arrows).

280 ]. L. Gutmann & T.R, Pitt Ford

' ;Fig. 7, Variations In appearance of smear layer on apicaily resecteddentine from smooth {S) to rough (R) with accumulations of dentina!debris.

\ •

Fig. 6. (a) Apical!}' resected dentine »'ith smear layer removed. Notesmall numbers of dentinal tubules and variations in their patency, (b)Apicaliy resected dentine with smear layer removed. Note amount oftubular sclerosis.

attention. While empirical experience favours theirusage, there were no studies or evaluations published toprovide the compiete parameters of their efficiency andeffectiveness, at the time of submission of this paper.

Methods of resecting the root surface—smear layer

The technique of resection from a macroscopic level hasbeen discussed. From a microscopic level, resectionwhich removes dentina) debris and irregularities isfavoured (Fig. 7). Eicket ai. {19 70) ha ve shown that debrisgenerated during the cutting of tooth structure, i.e. thesmear layer, is similar with diamond or tungsten carbideburs when prepared wel or dry. Gwinnet (J 984) reportedthat with tungsten carbide burs, gaps occurred in thesmear layer due to tearing and brittle fracture of thedentine by the cutting edges of the bur. Also, Gwinnet

(1984) noted that there was little difference in appear-ance of the smear layer when tungsten carbide burs wererun at high speed with or without water. However, whendiamond burs were used, the water appeared to signifi-cantly reduce the smear layer compared with dry cut-ting. In this regard, Pashley (1984) has also indicatedthat a thicker smear layer is usually created by cuttingwithout waterspray than with a heai'y air-waterspray.Brannstrom et al (1979) also noted that coarse diamondburs generally created a thicker smear layer than tung-sten carbide burs. Therefore, it is recommended thatroot-end resection be performed under constant Irri-gation, which assists the partial removal of the dentinalsmear layer from the surface. Also, if diamond burs areused to resect the root, a medium gritispreferred, followedby a line or ultrafine grit diamond. If there is a gutta-percha root canal filling resection without irrigation maypromote the lodging ofdentine chips in the gutta-percha,which could serx'e as a source of irritation if contami-nated. These chips may not be removable during theelimination of the smear layer with a dentinal cleanser(Fig. S).

Remova} of smear layer and dentine ckmineralization

In common with procedures in operative dentistry andperiodontics, removal of the smear layer and cxpo.sure ofthe apical collagen fibres is recommended after root-endresection, primarily to remove potentially contaminateddebris and to enhance the healing environment forcemental deposition. However, the nature of the dentine

Management of the resected root end 281

Fig. 8. (a) Apicai dentine resected without Vifater. Note dentine chips(dc) embedded in gutta-percha (gp): dentine (D). (b| Removal of smearlayer shows clean dentine chips with exposed patent tubules and noevidence of dentinal debris (dc) embeddeti in gutta-percha (gp); dentine(D).

cleanser to achieve this ideal is uncertain, as variousagents have been recommended, such as phosphoricacid (Passanezi et al 1979, Goldberg 1984), ethylenedi-amine tetra-acetic acid (Boyko et al 1980), hydrochloricacid (Register 1973, Ruse& Smith 1991), and citric acid(Register & Burdick 1975, Crigger et a!. 1983, Bostancietal 1990).Also, times of exposure and demineralizationhave been highlighted, as has the optimal pH for activity.Codeili et al (1991) indicated that the optimal exposureof collagen and demineralizatioo occurred with a bur-nishing application of citric acid (pH 1.0} for 3 min.Longer applications resulted in collagen denaturation.However, Sterrett et d. (1991)have shown that the peakactivity pH of citric acid was 1.42, beyond which effectivedentinal demineralization diminished. Craig (1990)showed that demineralization of resected root ends with

• a

•

• = : • • • = • • ^

Fig. 9. Removal of smear layer from resected root end mith WA citruacid and 3% ferric chloride. Dentine is clean and tubules are patent.

a 2-min burnishing of a 50% citric acid solution atpH 1.0 consistently resulted in a rapid and predictablelayering of a cementoid t>'pe of material on the resectedsurface of dogs' teeth after 43 days. No direct applicationto human teeth, under similar circumstances, has beenstudied.

What appears to be crucial to ultimate healing andcemental deposition is the stabilization of the exposedcollagen fibres along with minimal demineralization.Failure to do such may account for the discrepanciesseen In the periodontal literature regarding the use ofdifferent concentrations of citric acid at various times,likewise, the exact benefits of the citric acid are still con-sidered speculative and in need of further research (Neryet al. 1990). In essence, all that may be necessary toaccomplish the ideal healing at the resected root end maybe the removal of the smear layer and retention of thesmear plugs, as proposed by Brannstrom (1984), withthe use of Tubulicid (Tubulicid Blue Label, Tubulicid Redlabel; Dental Therapeutics AS, Nacka, Sweden) in coronalcavities. However, Pashley (1984) believes that this maybe difficult to achieve clinically.

Recent studies by Mizunuma (1986) and Wang &Nakabayashi (1991) have identified the use of the Fe'+ion, in the form of an aqueous solution of 10% citricacid and 3% ferric chloride (10:3), to stabilize dentinecollagen during the demineralization process (Fig. 9).However, applications were limited to less than 30 s,as longer exposure increased demineralization anddenaturation of the collagen. This approach hasenhanced the bonding that occurs with restorativematerials, and may also stimulate adhesion of theexposed, intact collagen with fibrin and flbronectin

282 /. L. Gutmann & T. R. Pitt Ford

(Poison & Proye 1983) and the splicioi of collagen withnewly fonned collagen fibrils (Ririe et aL 1980) duringthe wound healing {Ht)ce»!. Further work with diismateiial and other potential dentinat cleansa:s on theresected root eiut are warranted prior to thor wholesalerecommaudation.

There is substantial rationale for root-end resection inperiradicular surgery. Once resected, the root end poses am}nriad of concerns relative to the management of the rootcanal filling and the exposed dentinai tubules. Proceduiesdesigned to minimize local irritational factors and toenhance true periradicular healing are recommendedfrom both a clinical and biological standpoint. Areasrequiring further invest^ation have been highlighted inan attempt to stimulate research into th^e clinicallyrelevant issues.

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