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

Management ofthe resect^ root end: a clinical review

J. L. GUTMANN & T. R. PITT FORD* Department of Restorative Sciences, Baylor College of Dentistry, Dallas, Texas, USA; and 'Department of Conservative , United Medicd and Dental Schools, Guy's Hospitd, London, UK

Summary 1985). Little support presently exists for these rationales as the sole determinants for root-end resection. Carefiil management of the resect^ root end during endodontic surgery is critical to the overaU success ofthe case. After resection, the root structure presents with Removal of anatomical variations multiple anatomical variations and ccmslderadons at both a macroscic and microscopic level, Itiese include Commonly cited entities include severe canal curves, root outline, canal anatomy, dentinal tubule configur- lateral and accessory canals, apical bifurcations or ation, presence erf' a smear layer and filling deltas, and calcifications (Johns 1977. Oliet & Grossman material. Proper assessment of these variables will dic- 1983, Bames 1984, NichoUs 1984), These indications tate the best methods for root-end management, along exist only when the anatomical variations have been with the attainment of an anatomically compatible root implicated in case failure or are strongly suspected as face for optimal healing ofthe periradicular tissues. potential contributors to failure. The validity of their rationale occurs only after attempts at quality non- Keywords: dentine, endodontic surgery, resection, root surgical have failed. end, smear layer.

Introduction Removal of operator errors in canal preparation Endodontic surgery encompasses multiple specific pro- Despite the skill of the clinician, it is not uncommon for cedures designed to manage the compromised root sys- ledges, blockages, zips, perforations and separated instru- tem and periradicular tissues. A commonly performed ments to occur (Nicholls 1962, diLauro et d. 1980, Van procedure is root-end resection, often referred to as Welsenes & Van der Kwast 1983, Panzoni 1985), These or apicectomy (Gutmann & Harrison errors will only serve as valid rationales for surgical 1991), The term root-end resection refers specifically to intervention if there is failure following attempts to the removal ofthe apical portion ofthe root. The purpose non-surgically rectify the pn)blem and patient signs or of, and indications for, root-end resection are varied, and symptoms persist. the rationale for its use resides in each individual case. From an historical perspective, the surgical literature since the late 1800s has supported the following ration- To enhance removal ofthe soft tissue lesion ales for this procedure, although many of those cited may Often, root-end resection will facilitate access to deeply or may not be valid in contemporary . placed granulation or cystic tissues (Gerstein 1985, Gutmann & Harrison 1985), Removal of pathological processes

This has included root resorption, fractured root tips, Access to the canal system reactive or pathological tissues and potentially infected cementum and dentine at the root apex (Weaver 1947, Curettage alone will not allow apical entry into a canal Buch & Waite 1962, Leubke et d. 1964, Cummings et al. system which requires thorough cleaning, shaping and obturation, when it has not been properly managed Correspondence: James L, Gutmann DDS, Professor and Chairman, Department of Restorative Sciences, Baylor College of Dentistry, 3302 through the crown (Vasiliu 1977, Oliet & Grossman Gaston Avenue, Dallas, Texas 75246, USA, 1983, 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 this against resection were suspect, periradicular curettage purpose, depending on root and canal anatomy. was still advocated as a terminal, definitive procedure. In essence, the real cau^ of the periradicular problem was invariably not being addressed, as the soft tissue Evaluation ofthe adaptation ofthe catud filling surrounding the root was only the result of continued material irritation coming from the root canal system. Even in cases which appear radiographically acceptable, clean- Removal of the root apex allows the clinician to assess ing and shaping ofthe canal system is often below accept- three dimei^onally the quality of the adaptation and able levels. Therefore, contemporary views support the nature ofthe root canal filling material (Leubke 1974. need for root-end resection in most cases as being necess- Harrison & Todd 1980) and to determine the need for a ary to achieve the goals of the surgical procedure. The root-end flUing. extent to which the removal ofthe root end should occur, will be dictated by the following factors (Gutmann & To enhance the adaptation ofthe root canal filhng Harrison 1991), material (1) Access and visibility to the surgical site, (2) Position and anatomy of the root within the This is probably the most commonly cited reason for alveolar bone. root-end resection, especially when the canal system (3) Anatomy of the cut root surface relative to the cannot be cleaned, shaped and obturated through the number of canals and their configuration. crown of the tooth (Herd 1968, Leubke 1974, Johns (4) Need to place a root-end filling into sound root 1977), structure, (5) Presence and location of procedural errors, e.g, perforation. Reduction of root apices which havefenestrated the (6) Presence of an intra-alveolar root fracture. bone (7) Presence of any periodontal defects, This occurs primarily in maxillary premolars and molars. (8) Anatomical considerations, such as root proximity With pulpal demise, the periosteum, which overlies roots to adjacent teeth, or level of remaining crestal with fenestrated bone, becomes inflamed. Root-end bone, resection contours the root tip to lie within its bony (9) The presence of significant accessory canals. Roots housing (Gerstein 1985, Ruiz de Termino Malo et al. with a likelihood of these anatomical aberrances 1986), would be likely to receive more extensive resection.

Exploration for aberrant canal anatomy or root Resection technique fractures The technique of root-end resection uses a lingual to labial The resection of the root end enables direct vision of any bevel, angled to the coronal aspect of the tooth. This is canal aberrances or imsuspected root fractures (Taylor & designed for surgical access and visibility. Angles for root Bump 1984, Gutmann & Harrison 1985, Kirschner beveis have been suggested to range from30°to45°in the 1987). line 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 Consequaices of root-end resection & Harrison 1985). From the anterior to the posterior, the Whilst substantial reasons exist for root-end resection, angle ofthe bevel will gradually go from a direct coronal- many controversies surround this procedure, especially buccal cut to one that is accentuated coronally and as it relates to the amount of root removed. Historically, mesio-buccally placed. These angles of resection and some authors have discouraged root-end resection their use will also be determined by the root inclination because it opened daitinal tubules which might house and curvature, number of roots, thickness of bone and bacteria, tooth stability in the alveolus would be com- position ofthe root in the bone and arch. promised, and cemental healing might not occur on the The root end can be resected and beveUed in one of two exposed dentine. Whilst the validity of these arguments ways. Once the root end has been exposed, the bur and Management ofthe resected root end 275

handpiece are positioned at the desired angle and the shaped, kidney-bean shaped, or tear-drop shaped. Out- root is shaved away, beginning from the apex, cutting lines will vary depending on the tooth, angle ofthe bevel coronally. The bur is moved from mesial to distal at the and position ofthe cut on the root. Once cut, however, the desired angle, shaving the root smooth and flat, and entire surface must be visible. If visibility or access is exposing the entire canal system and root outline. This impaired, or the root po^esses an imusual cross-sectional approach allows for continual observation of the root outline, 1 % methylene blue dye can be plared on the root end during the cut. surface to help identify Ihe periodontal ligament that The second technique of resection is to predetermine surrounds the root (Cambruzzi & Marshall 19 8 3), A small the amount of root end to be resected. This approach cotton pellet containing dye is wiped over the root face for however may remove more root structure than is 5-10 s. Subsequently the area is flushed with sterile essential. If chosen, the bur and handpiece are positioned water or saline. The dye will stain the periodontal liga- at the ideal angle and the apex is resected by cutHng ment dark blue, highlighting tfie root oufline (Fig. 1). through the root from mesial to distal. Once the segment A potential drawback to this technique may be the is removed, the root face is gently shaved with the bur to deposition of cotton fibres on the resected surface or in smooth the surface and ensure complete resection and the osseous wound. Residual remnants of cotton fibres visibility of the root face. This technique works well have been shown to induce a foreign-body reaction in when an apical biopsy is desired or to gain access to the healing tissues (Gutmann & Harrison 1991). significant amounts of soft tissue located lingual to the root. Anatomy ofthe canal system

The shape ofthe exposed canal system will vary depend- Anatomy ofthe resected root surface— ing on the angle of the bevel and the canal anatomy at macroscopic considerations the level ofthe cut. Canal systems will generally assume a more elongated and accentuated shape as the angle of The appearance of the root face following root-end the bevel is increased buccaily (Fig, 2). Often, canals will resection will vary, depending upon the type of bur used, be irregular and extend further than anticipated, thus, the external root anatomy, the anatomy of the canal additional root structure may have to be removed to system exposed at the particular angle of resection ensure exposure ofthe entire system. chosen, and the nature and density of the root canal filling materiaL Root canal filling material

Bur type In addition to the variations with different materials, e,g, gutta-percha, silver cones, pastes, the nature of the Various types of bur have been recommended for root- filling technique, e.g. lateral condensation, vertical con- end resection, such as round burs, straight fissure burs, densation, or thermoplastic fillings, will provide a differ- diamond burs, and cross-cut fissure burs (Gutmann & ent view ofthe canal contents and their adaptation to the Harrison 1991), Each will leave a characteristic anatom- root canal walls (Fig. 3). Likewise, the different burs ical imprint on the root face, from rough-grooved and advocated for resection will create discrepancies in the gouged to regularly-grooved and smooth. To date, no surface of the filUngmateria l and adaptation to the canal study has clearly defined the advantages of one type of bur walls. For example, coarse diamond burs will tend to rip over the other, with regard to surface morphology or and tear at the gutta-percha root canal filling, spreading tissue healing response. For years, however, clinical prac- the gutta-percha over the edge of the canal aperture and tice has favoured a smooth flat root surface (Moorehead onto the resected root face (Fig, 4). Invariably this will 1927, Sommer 1946, Trice 1959, Gutmann 1986), create gaps between the originally adapted gutta-percha and the root canal wall. Similar findings are noted with fissure burs and round burs (Gutmann & Harrison Exterrud root anatomy 1991), In order to prevent this, surface finishing with an ultra-fine diamond is recommended (Ultrafine No, The external root anatomy will determine the ultimate 862-012 diamond bur; Brasseler, Savannah, GA, USA; shape of the cut root end, as oval, round, dumb-bell Komet, Lemgo, Germany). 276 ].l. Gutmatm & T. R, Pitt Ford

mmyi?^

Fig. 1, Outline of resected root, in vitro, deiineated by staining of the Fig. 2. Elongated canal on resected root surface deiineated with periodontal ligament with methylene blue. methylene blue. Note extension (arrows) beyond gutta-percha filling.

Clinical considerations and it is determiBed that tbere is uncleaned or unlilled space, a root-end preparation is made with a bur or with The complete root face must be identified and examined an ultrasonic tip to clean the apical extension of the subsequent to resection. The examination is done with a canal space and to create a caiity for obturation. fine, sharp probe, e,g. DG 16/17 (Hu Friedy, Chicago, IL, USA), guided around the peripher)' of the root and the root canal. The presence of additional foramina, anasto- Anatomy ofthe resected root surface— moses between foramina, fracture lines, and the quality microscopic considerations of the apical adaptation of the root canal filling must be checked (Fig, 5), If methylene blue has been used, it will Dentinal tubules also hcLve a tendency to stain the periphery of the canal system and highlight fracture lines. Nitromersol, a The consequence of exposing resected dentinal tubules to dental disinfectant which stains reddish-brown, can also the periradicular tissues has been a controversial issue be used when examining the root face or a ibre-optic for many years. Claims were made that ideaJ healing light can be aimed at or behind the root end to enhance could not occur against the tubules in the form of layered iTsibility (Arens et d. 1981). If these methods do not cementum and periodontal ligament (Barron etal. 1947, work, it may be necessary to remoFe additional root Pearson 1949, Curson 1966, Wakeley & Simon 1977). structure to identify the canal system or, in the case of a However, it iias been shown that cementum can reform fracture line, to enhance its direction and extent. Once over the resected tubules and that a periodontai encap- the surface extent ofthe canaJ system has been identified. 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, Smith bacteria retained in the root canal sj'stem has been impli- 1967, Rowe 1967, Andreasen 1973, Craig 1990). cated in endodontic failure (Lin et al. 1991) and may, A second controversy is that exposure of the dentinal therefore, have access to the periradicular tissues foUow- tubtiles would expose the periradicular tissues to bac- ing resection, Nicholls (1965) has taken an opposite teria entrapped in the tubules (Fawn 1927, Ross 1935, vie^v stating that, 'the exposure of dentinal tubules Castenfeldt 1939), However, no correlation could be ivhich may have been contaminated at their pulpal ends, shown by Andreasen &Rud{1972) between the presence although sometimes constituting a criticism of apicectomy of micro-organisms in the dentinal tubules and the degree in the past, is probably of little or no significance.* of periradicular inflammation. Likewise, because the A third area of concern foUoiving tubule exposure is number of tubules in the apical third would be signifi- the possibility that these channels may seri'e as a direct cantly reduced in both number and patency, with ageing course of contamination from unclean root canals and sclerosis (Fig. 6) (Carrigan et al 1984. Ichesco et al. into the periradictilar tissues, especially if there is 1991), coupled with root-end resection, this would tend coronai leakage Into the root canal system. Tidmarsh & to reduce the number of bacteria in the region signifi- Arrowsmith (1989) have sho%vn that root ends resected cantly, especially since the majority of bacteria in the from 45° to 60° have as many as 28 000 tubules mm^- apical third have been shown to be located immediately at a point Immediately adjacent to the canal. At the adjacent to the root canal system (Jolly & SuOivan 1956. cemental-dentine junction, an area which may com- Shovelton 1964) and good canal cleaning and shaping municate with the root canal even in the presence of a would tend to eliminate them from this area. Although root-end filling, an average of 13 000 tubules mm^* 78 J. L. Gutmann & T. R. Pitt Ford

resected root end may serve as a source of irritation to the periradicular tissues, primarily preventing the intimate layering of cementum against the resected tubules. While this concern is primarily clinical in nature and has not been demonstrated in human specimens, short term ani- mal studies io which vital, uncontaminated teeth were treated endodontically followed by root-end resection and smear layer removal have shown favourable cemental apposition (Craig 1990). At the same time, the smear layer may actually block the tubules and serve as a source of obturation ofthe potential avenues of communication, especially with tubules contaminated with bacteria or those exposed to oral fluids over long periods of time. Experiments designed to evaluate these parameters are essential, because there is no unequivocal data to support the proper management of the smear layer on the resected 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 system adequately, a root-end preparation should be made into the root to the coronal extent of the resected apical tubules. This wiil vary from case to case, but generally a depth of 2^ mm would be sufficient (Taylor & Doku Fig. 4. (a) Root end resected with coarse diamond bur. Note smearing of 196]. Rud & Andreasen 1972. Barry et al 1975). This the gutta-percba onto the resected surface, (b) SEM shows smearing of can either be made with a rotary bur. such as inverted gutta-percha tags and gaps between the root canal filling and wall (bar=0,1 mm). cone or round bur (ISO size 008) at high- or low-speed, or with specially angulated tips adapted for use on an ultra- sonic unit (ENAC, Osada Electric Co., Los Angeles, CA, were found. Likewise, owing to angular changes io the USA). This approach to root-end preparation assumes tubules at the apex, there could be patent communi- that a standard type of filling material, such as amalgam cation with the main canal if the depth of the root-end with varnish, will be placed. However, the approach to preparation in the buccal aspect ofthe cavity was insuf- and the design of the preparation may vary if other ficient to compensate for these anatomical variations contemporary restorative materials are used. While the (Vertticci & Beatty 1986, Beatty 1986). Recently, purpose ofthe paper is not to address these materials, the Ichesco et al. (1991) have shown that root-end resec- practitioner must take these potential variations into tions in older teeth evidenced less leakage than that seen account during root-end preparation. in teeth from younger patients; this corroborates with Recent enhancements io apical root-end preparation the findings of sclerosis and reduced patency in the apical have resulted from the development of 'ultrasonic retro- dentinal tubules (Carrigan et al. 1984). It was suggested tips' (Excellence in Endodontics, San Diego, CA, USA) that if the apical ramifications commonly found in young (Carr 1990). These small, angled tips have been advo- teeth could be dismissed as a rationale for root-end re- cated for the ultrasonic development of apical prep- section, the resection would be inadvisable owing to the arations parallel to the long axis ofthe root after minimal patency ofthe apical dentina! tubules. root-end resection. Their use in the debridement and Fourth, the presence of a contaminated smear layer, enlargement of canal anastamoses and irregularities containing microorganisms and tisstie debris, over the commonly 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-percha condensation and canal extension; fracture visible in tlie root (arrow), (c) Palatally extended canal space (arrows) of mesial buccal root of a maxillary first molar, (d) Gutta-percha ailing of canal and small portion of anastomosis. Note necrotic tissue debris in canal extension (arrows). 280 ]. L. Gutmann & T.R, Pitt Ford

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

(1984) noted that there was little difference in appear- ance of the smear layer when tungsten carbide burs were run at high speed with or without water. However, when diamond 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 indicated that a thicker smear layer is usually created by cutting without waterspray than with a heai'y air-waterspray. Brannstrom et al (1979) also noted that coarse diamond burs generally created a thicker smear layer than tung- Fig. 6. (a) Apical!}' resected dentine »'ith smear layer removed. Note sten carbide burs. Therefore, it is recommended that small numbers of dentinal tubules and variations in their patency, (b) Apicaliy resected dentine with smear layer removed. Note amount of root-end resection be performed under constant Irri- tubular sclerosis. gation, which assists the partial removal of the dentinal smear layer from the surface. Also, if diamond burs are used to resect the root, a medium gritispreferred, followed attention. While empirical experience favours their by a line or ultrafine grit diamond. If there is a gutta- usage, there were no studies or evaluations published to percha root canal filling resection without irrigation may provide the compiete parameters of their efficiency and promote the lodging ofdentine chips in the gutta-percha, effectiveness, at the time of submission of this paper. which could serx'e as a source of irritation if contami- nated. These chips may not be removable during the elimination of the smear layer with a dentinal cleanser Methods of resecting the root surface—smear layer (Fig. S). The technique of resection from a macroscopic level has been discussed. From a microscopic level, resection which removes dentina) debris and irregularities is Remova} of smear layer and dentine ckmineralization favoured (Fig. 7). Eicket ai. {19 70) ha ve shown that debris generated during the cutting of tooth structure, i.e. the In common with procedures in operative dentistry and smear layer, is similar with diamond or tungsten carbide periodontics, removal of the smear layer and cxpo.sure of burs when prepared wel or dry. Gwinnet (J 984) reported the apical collagen fibres is recommended after root-end that with tungsten carbide burs, gaps occurred in the resection, primarily to remove potentially contaminated smear layer due to tearing and brittle fracture of the debris and to enhance the healing environment for dentine by the cutting edges of the bur. Also, Gwinnet cemental deposition. However, the nature of the dentine Management of the resected root end 281

• a

•

•=:• ••=•• ^

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

a 2-min burnishing of a 50% citric acid solution at pH 1.0 consistently resulted in a rapid and predictable layering of a cementoid t>'pe of material on the resected surface of dogs' teeth after 43 days. No direct application to human teeth, under similar circumstances, has been studied. What appears to be crucial to ultimate healing and cemental deposition is the stabilization of the exposed collagen fibres along with minimal demineralization. Failure to do such may account for the discrepancies seen In the periodontal literature regarding the use of different concentrations of citric acid at various times, Fig. 8. (a) Apicai dentine resected without Vifater. Note dentine chips likewise, the exact benefits of the citric acid are still con- (dc) embedded in gutta-percha (gp): dentine (D). (b| Removal of smear layer shows clean dentine chips with exposed patent tubules and no sidered speculative and in need of further research (Nery evidence of dentinal debris (dc) embeddeti in gutta-percha (gp); dentine et al. 1990). In essence, all that may be necessary to (D). accomplish the ideal healing at the resected root end may be the removal of the smear layer and retention of the cleanser to achieve this ideal is uncertain, as various smear plugs, as proposed by Brannstrom (1984), with agents have been recommended, such as phosphoric the use of Tubulicid (Tubulicid Blue Label, Tubulicid Red acid (Passanezi et al 1979, Goldberg 1984), ethylenedi- label; Dental Therapeutics AS, Nacka, Sweden) in coronal amine tetra-acetic acid (Boyko et al 1980), hydrochloric cavities. However, Pashley (1984) believes that this may acid (Register 1973, Ruse& Smith 1991), and citric acid be difficult to achieve clinically. (Register & Burdick 1975, Crigger et a!. 1983, Bostanci Recent studies by Mizunuma (1986) and Wang & etal 1990).Also, times of exposure and demineralization Nakabayashi (1991) have identified the use of the Fe'+ have been highlighted, as has the optimal pH for activity. ion, in the form of an aqueous solution of 10% citric Codeili et al (1991) indicated that the optimal exposure acid and 3% ferric chloride (10:3), to stabilize dentine of collagen and demineralizatioo occurred with a bur- collagen during the demineralization process (Fig. 9). nishing application of citric acid (pH 1.0} for 3 min. However, applications were limited to less than 30 s, Longer applications resulted in collagen denaturation. as longer exposure increased demineralization and However, Sterrett et d. (1991)have shown that the peak denaturation of the collagen. This approach has activity pH of citric acid was 1.42, beyond which effective enhanced the bonding that occurs with restorative dentinal demineralization diminished. Craig (1990) materials, and may also stimulate adhesion of the showed that demineralization of resected root ends with exposed, intact collagen with fibrin and flbronectin 282 /. L. Gutmann & T. R. Pitt Ford

(Poison & Proye 1983) and the splicioi^ of collagen with CACTEJFEiar T (1939) Om rettograd rotfyllolng vid radlkaloperation newly fonned collagen fibrils (Ririe et aL 1980) during av kronisk apikal paradentit. Svensk Tai^Bakare-JMskrifi 32,227-60. CmsLU GR, FKY HR. DAVIS JW (1991) Burnished vemis non- the wound healing {Ht)ce»!. Further work with diis bumished apirilcaticni of critk; acid to human diseased root surfaces: mateiial and other potential dentinat cleansa:s on the the Infect d time and method of application. Quintessence Inter- resected root eiut are warranted prior to thor wholesale nationa/22,277-83. recommaudation. CoouDGE ED (1930) Rot* resection as a cure for chronic periapical Infection: a hi^ologic report rf a case showing complete repair. Journal tfthe American Denta! Association 17,239-49. CiiAicK(1990)Theeviduationof radicular andperiradicularwound}mi!ing foUowing citric acid demineralization o/opicaUtf resected root ends. 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