Surgical Management of Problems Associated With Lateral Canals

The clinical incidence of problems associated with natural lateral canals does not rise to the statistical percentage of roots that actually have anatomically demonstrable lateral canals.^15,48 Additionally, the incidence of lateral canals in the middle and coronal thirds of roots is statistically rare. Most bony lesions that arise from necrotic debris in a nonvital tooth heal with routine nonsurgical treatment (Fig. 18-1). In the case of a previously treated tooth, most lateral lesions resolve with revision, as demonstrated in Chapter 14, Fig. 14-6. This is all the more amazing because although many clinicians take personal pride in being able to extrude sealer, gutta-percha, or both through these canal spaces (Fig. 18-2), there are no proven techniques to actually clean and disinfect these aberrant channels. Furthermore, the empirical concept that pushing filling materials through these canals will débride this small space of its irritants is faulty.³⁹

FIGURE 18-1 A, Preoperative radiograph of an endodontically treated mandibular premolar with a lateral canal lesion. B, One-year reevaluation radiograph showing resolution of the lateral lesion.

(Courtesy Dr. Ryan Wynne.)

FIGURE 18-2 Postoperative image showing extrusion of the filling materials and/or sealer through the lateral canal.

There are relatively few teeth with lateral lesions that fail to heal after root canal treatment. Even fewer are those which develop lateral lesions after root canal treatment.⁴⁸ Unfilled or poorly obturated canal spaces can be a predisposing factor to the development of a lateral lesion, especially spaces between a gutta-percha filling and an intraradicular post (Fig. 18-3; see Chapter 20). Nonsurgical revision is usually the treatment of choice but not always feasible. Lesions that fail to heal, as well as those associated with teeth that cannot be revised, generally require surgical intervention.

FIGURE 18-3 Amalgam repair of a lateral canal communicating with an unfilled canal space between the root canal filling material and the post. Case was treated in 1976.

In the preoperative evaluation, determining the location of the lateral canal is a diagnostic challenge. Lateral canals can occur on any surface of the root and are rarely visible radiographically.⁴⁸ Perhaps the easiest to locate are those that have clinical signs of a draining tract but no radiographic changes. These canals will usually be found on the labial aspect of the root (Fig. 18-4).

FIGURE 18-4 A, Clinical view of a sinus tract found on the labial aspect of the maxillary left lateral incisor. B, No radiolucency is visible in this area. C, Surgical exploration reveals a midroot lateral canal on the labial surface.

The presence of most lateral canals is inferred by the presence of a lateral radiolucency, which is only a two-dimensional representation of a dynamic three-dimensional process (Fig. 18-5). Since lesions tend to develop symmetrically from the source of infection, the approximate location of the lateral canal, if present, can be identified vertically—that is, the midpoint between the coronal and apical limits of the lesion. The greatest difficulty is determining the location in a horizontal orientation. Lesions often extend circumferentially from their sources. What is observed radiographically as a lesion on the mesial or distal surface of the root may in reality originate from a lateral canal on either the palatal or labial aspect of the root. Palatally or lingually located lateral canals will generally not be accessible to surgical repair.

FIGURE 18-5 Messal bony lesion associated with a lateral canal presumably due to coronal leakage from recurrent caries.

A second anatomic problem is the surgical accessibility of the canal in interproximal or interradicular spaces. Lateral canals occurring in fluting of molar roots can be impossible to see at surgery, although some may be large enough to locate tactilely with an explorer. Even if they can be located, space limitations can prevent successful completion of the repair. The only avenue for possible resolution of these dilemmas is surgical exploration. Preoperatively, the patient should be informed that if the lateral canal is not accessible, the root may have to be removed in its entirety or the tooth may have to be extracted (Fig. 18-6).

FIGURE 18-6 A, Lateral canal lesion located on the distal aspect of the mesial root of the mandibular right first molar. B, Extracted mesial root. Surgical repair was attempted, but it was not possible to visualize the lateral canal, owing to deep fluting of root surface. Note lateral canal (arrow). C, A radiograph of the root. Note the distance of the lateral canal (yellow dot) from the treated canals. Revision would have had no effect on this problem.

The essential elements of the surgical procedure are the same as for periapical surgery, which is described in detail in Chapter 16. The lateral communication is located, cleaned, enlarged, and filled exactly as one would surgically fill the prepared apical foramen on the resected root surface.⁴⁴ A small ultrasonic tip or No. 15 or 20 K-file in the ultrasonic handpiece will usually follow the course of a lateral canal and enlarge it to the point at which a larger file or a diamond tip could follow the initial pathway. As with apical preparations, the size of the preparation must be sufficient for the placement of the filling (preferably mineral trioxide aggregate [MTA]).

CLINICAL PROBLEM

Problem

A 47-year-old male presented with a draining sinus tract on the midline of the labial papilla adjacent to the maxillary right central incisor. The lesion was difficult to discern radiographically (Fig. 18-7, A). A periodontal probe indicated normal sulcular probings but probed through the draining tract to the side of the root.

FIGURE 18-7 A, Preoperative radiograph of maxillary right central. Lesion associated with lateral canal extends from midroot level to alveolar crest in the midline. B, Reevaluation at 9 years, 3 months, demonstrating excellent healing.

Solution

Because of the presence of a post in the root and the absence of any periapical pathosis, the midroot area was exposed surgically, and the presence of a lateral canal was confirmed and repaired. A 9-year, 3-month reevaluation radiograph indicated excellent healing with restoration of the periodontal ligament space and lamina dura in the surgical site (see Fig. 18-7, B).

As described for apical surgery in Chapter 16, some diamond-coated or metal ultrasonic instruments may be too large to begin the preparation, so a smaller-tipped instrument or a small endodontic file must be selected. Low to medium power is indicated to prevent aggressive and indiscriminate cutting of root structure.⁴⁴ Instruments with ideally angled tips for access to these aberrant canals should be considered (see Figs. 16-33 and 16-34).

Surgical Repair of Root Perforations Below the Attachment

Most perforations during access opening occur in the marginal periodontium (see Chapters 8 and 16). The only common exception to this observation is the case where the access perforation occurs in the furcation. If the attachment tissues are not disturbed, small furcation perforations have a good chance of long-term stability with an internal repair using MTA⁴⁷ (Fig. 18-8).

FIGURE 18-8 A, Furcal bone loss associated with an access perforation through the floor of the furcation. B, Calcium hydroxide used as a temporary seal during completion of the endodontic treatment. C, Reevaluation after 1 year. The perforation was permanently sealed with mineral trioxide aggregate. Note the restoration of normal bone architecture in the furcation.

Larger perforations in the furcation can be problematic. If significant portions of the floor of the pulp chamber have been removed, the chance of successful repair is poor (Fig. 18-9).⁴⁷ Similarly, cases that have been repaired with materials other than MTA may have poor long-term outcomes, especially if the material is forced through the defect into the periodontal tissues.⁴⁵ It is almost impossible to remove the excess nonsurgically, and attempts are likely to make the perforation larger. In this regard, even surgical repairs with MTA of larger perforations of the roots in the furcation can have mixed results. Fig. 18-10 illustrates a case in which a perforation was initially repaired internally with MTA. After years, a furcation radiolucency lesion had developed, and a surgical repair was attempted. One year later, the bone had not healed completely. Although the patient was symptom free and the tooth functional, the prognosis was guarded.

FIGURE 18-9 Extrusion of cement repair material through a furcation perforation. Chronic drainage through the gingival sulcus was apparent at the time of examination. Extraction was recommended.

FIGURE 18-10 A, Referral radiograph of mandibular left first molar. The furcation was perforated in the access procedure and was temporarily repaired with calcium hydroxide (arrows). B, Root canal treatment completed and perforation filled with mineral trioxide aggregate. It was a challenge to pack the material and not have extrusion. C, Reevaluation radiograph after years. Probings were normal but tooth was symptomatic, and the tooth had a sinus tract on the buccal mucosa. D, Surgical repair in progress. Note the intact crestal bone over the furcation. E, Fifteen-month reevaluation. Patient was asymptomatic, sinus tract had not reappeared, but prognosis was guarded.

Lateral strip perforations can occur during root canal cleaning and shaping, generally with hand instruments or excessive use of large nickel-titanium instruments (see Chapter 10). Often the anatomy of the root plays a role (Fig. 18-11); deep flutes or invaginations of the proximal root surfaces cannot be discerned radiographically. Although anticurvature filing (see Chapter 10), skewed positions of the access cavity, and other techniques are effective in reducing this problem, it cannot be avoided completely.

FIGURE 18-11 Routine access and orifice-widening procedures on extracted tooth with a deeply fluted mesial root. A strip perforation quickly occurred that appeared to be unavoidable in a clinical case.

As with lesions adjacent to lateral canals, accessibility to the defect can be a major problem for repair, but these defects are usually larger and much easier to locate. If the defect is visible, the repair can be made in the same manner as with the repair of defects from lateral canals. Often the preparation must be longer vertically because of the thin dentin above and below the perforation itself (Fig. 18-12).

FIGURE 18-12 A, Lateral lesion associated with a strip perforation. Probings are normal. B, Radiograph of repair with mineral trioxide aggregate. C, One-year reevaluation film showing restoration of normal periodontium on the buccal. Probings were normal. D, One-year reevaluation radiograph indicating bone healing in the furcation.

Strip perforations can also occur from excessive enlargement of the canal during post space preparation.³⁶ This is seen most often in roots with thin mesial-distal widths and roots with fluted anatomy on the proximal surfaces. If accessible, the techniques for placing an MTA filling are effective (Fig. 18-13). Many strip perforations resulting from post preparations are particularly difficult to repair because very thin dentin remains around the perforation defect. The greater the post diameter, the thinner the tooth structure will be. Cutting into the metal of the post requires a high-speed handpiece and good access. Some creative, specialized approaches may be considered to repair these defects, but they are beyond the scope of this text. It is usually better to remove the post if possible (Fig. 18-14).

FIGURE 18-13 A, Lateral lesion associated with a stripping perforation due to overenlargement of the canal for post preparation. B, Five-month reevaluation indicating healing of the lesion.

FIGURE 18-14 A, Intraradicular post protruding through a perforation. B, Removal of the post is preferred, rather than attempting to cut the post back into the root prior to repairing the perforation.

Perforations with endodontic instruments can occur deep in the root from failure to negotiate curves, attempting to bypass blockages, or failing to consider the normal anatomy of the tooth during cleaning and shaping procedures. If discovered early, internal repairs may effectively resolve the perforation problem; if not possible, then surgery will probably be necessary.

CLINICAL PROBLEM

Problem

A 38-year-old female presented with what was considered to be a failing root canal procedure on a maxillary right central incisor (Fig. 18-15, A). The tooth had been root treated approximately 6 years previously. At the time of examination, the symptoms were palpation tenderness, dull aching, and percussion tenderness. The periapical film indicated a well-filled root canal, but a large periapical radiolucency was present, and nonsurgical revision of the previous treatment was recommended.

FIGURE 18-15 A, Root-treated maxillary right central incisor with a large apical lesion. B, Instrument in perforation. The perforation was repaired with mineral trioxide aggregate. C, One-year reevaluation. Note that the post space was not used in placement of crown. This presents a long-term liability for continued success of the repair.

Solution

The tooth was reopened, and while the existing filling material was being removed, the patient felt pain at a level well short of the estimated tooth length. An instrument was placed, and a radiograph was made. A labial perforation was revealed that proved to be the etiology of all the current pathosis (Fig. 18-15, B). Reparative surgery was performed, and the perforation was repaired with MTA. A 1-year reexamination indicated excellent healing of the original lesion without revision of the root canal treatment in the apical half of the canal. A porcelain veneer crown had been placed by another dentist in the interim, but unfortunately, the post space that had been prepared for the final restoration was not properly used.

Surgical Repair of Problems Associated With Some Root Fractures

The etiology of partial root fractures on the lateral root surface of some teeth is unknown. Clinical findings are typical of lesions associated with lateral canals or strip perforations along with normal periodontal probings. Often the signs of acute or chronic inflammation/infection (midroot swelling, sinus tracts, etc.) are present.

Radiographic findings are similarly nonspecific. The radiolucency is characterized by an apical and a coronal border. In these cases, the apex is usually not involved (see Fig. 18-16, A). Consequently, it is not possible to make the specific preoperative diagnosis of partial vertical root fracture. In all cases, they are discovered at surgery. The clinical appearance is a vertical fracture line located in the midroot area on the palatal surface (see Fig. 18-16, B).

FIGURE 18-16 A, Preoperative radiograph of a large radiolucent lesion assumed to be associated with a lateral canal on the treated second premolar. B, Fracture line (arrows) located on palatal surface. Tooth was extracted due to inaccessibility.

If the fracture line is in a position where repair is possible, the techniques for lateral repairs will be effective. The most significant and difficult modification is the preparation that must follow the crack line to its full extent. The result is a narrow slot preparation similar to the preparation of an isthmus between two canal orifices in periapical surgery.

If straight-line access is possible, a quarter-round (0.5 mm) bur is ideal. For maximum control, the straight, low-speed handpiece, held in the pencil grip, works well. If straight-line access is not possible, the ultrasonic instrument can be used with either a small, angled apical surgery tip or an endodontic file that has been shortened to increase stiffness and placed in a special ultrasonic adaptor.

CLINICAL PROBLEM

Problem

A 40-year-old patient presented with a swelling in the midroot area of the mandibular left second premolar. The tooth had a previous root canal procedure and was restored with a post and crown. Radiographically, a large midroot radiolucency was present, and a large uncleaned lateral canal was suspected (Fig. 18-17, A).

FIGURE 18-17 A, Preoperative radiograph of a lateral radiolucency assumed to be associated with a lateral canal on the treated first premolar. B, Surgical exposure reveals a vertical midroot fracture line (arrows). C, Repair of the fracture line with MTA. D, Four-year reevaluation radiograph indicating excellent healing.

Solution

Nonsurgical revision was not considered and the defect was exposed surgically. Following curettage, a midroot fracture line was observed on the distal buccal aspect (see Fig. 18-17, B arrows). Because of accessibility, the fracture line was prepared with a quarter-round (0.5 mm) bur and an ultrasonic tip. The preparation was filled with gray MTA (see Fig. 18-17, C). A reevaluation radiograph made 4 years later demonstrates excellent healing with restoration of a normal periodontal ligament space and lamina dura (see Fig. 18-17, D).

Surgical Techniques for Resection of Roots and Teeth

General Considerations

Root resection, or root amputation, involves removing the root and either leaving the crown intact (Fig. 18-18) or additionally removing the portion of the crown that overlies the removed root.^26,27,49 In the treatment of maxillary molars, this procedure is also known as trisection.^20,24 This concept also applies to the removal of a single-rooted tooth from a multiabutment fixed bridge or splint.²⁵

FIGURE 18-18 A, Maxillary first molar with a vertical fracture in the mesial-buccal root. B, Following root amputation of the fractured root.

Tooth resection, or hemisection, is a technique in which a tooth is “cut in half.”²⁷ As with root resection, multiple techniques can be used: cutting the tooth in half and retaining both segments, known as bicuspidization¹⁹ (Fig. 18-19), or cutting the tooth in half with the intent of retaining only one of the segments.^1,5,35 (see Fig. 18-21). This type of resection is seldom indicated due to the difficulty of restoring and maintaining the former furcation area. This procedure may also result in unfavorable soft and hard tissue relationships. Two areas of the mouth in which the resection procedure is reasonably successful are on on mandibular molars with separated roots and in some maxillary molars, with the removal of the palatal root.

FIGURE 18-19 Hemisected mandibular first molar restored with splinted crowns (bicuspidization).

FIGURE 18-21 A, Mandibular first molar with a vertical fracture in the distal root. B, Post root resection. This is one of the most common endodontic indications for tooth resection.

Performing root/tooth resections to allow retention of compromised teeth has been all but abandoned owing to the success of contemporary implants.^7,26,27 However, resective procedures are viable treatment considerations in preserving natural tooth structure and can provide the patient with a reasonable alternative in many critical clinical situations. When done properly and the patient practices good oral hygiene, success rates can be quite high and comparable to other treatment choices.¹²

Multiple published studies in the periodontal literature have supported root resection as a successful long-term treatment.* Success with this treatment modality is generally defined as tooth retention with probing depths of less than 4 mm, no bleeding on probing, no exudation, and no evidence of root caries or fracture. The success rates overall for resected molars in these studies can be judged comparable to the success rates of implants in the same locations.