healthy PDL and an absence of signs of resorption and other pathology, both of the canine itself and of the roots of the adjacent teeth, which would determine whether or not the tooth would respond to orthodontic forces.
Fig. 5.6 Cone beam computed tomography (CBCT) imaging slices of a palatally impacted canine that has crossed the midline, as seen on (a) a panoramic curved slice (b) a cross‐sectional slice and (c) an axial slice. The long axis of the canine is oriented approximately 10° to the horizontal. (d) A wide flap has been reflected, the deciduous canine extracted and the canine exposed. (e) An eyelet has been bonded to the most accessible location on the crown of the canine, with the twisted wire connector hanging loosely. (f) The surgical flap was re‐sutured back to its former place, the loop of the auxiliary archwire in its passive (vertical) mode, after ligation over the main archwire. (g) The twisted ligature connector from the eyelet has been drawn through a small piercing in the flap, located immediately opposite the eyelet above it. (h) The vertical loop of the auxiliary archwire is turned inwards and latched by the shortened connector, in contact with the palatal mucosa.
The crown of the impacted canine was exposed using a wide flap, but with minimal removal of bone. The deciduous canine was extracted. The unexposed crown lay between the root apices of the central incisors. Due to the obstruction caused by the roots of both the central and lateral incisors of the right side, it had traversed the anatomical midline, from where it had no available direct route to its appropriate place in the dental arch.
An attachment was bonded by the orthodontist, while haemostasis was maintained by the surgeon. The location for the bonding, chosen by the orthodontist, was the anatomically distal aspect of the rotated crown of the canine. This was also the most superficial and accessible site. A twisted steel ligature pigtail had been tied into the eyelet prior to its placement and was intended as the means of transferring extrusive force to the tooth.
The flap was pierced at the point where the flap covered the eyelet, to accommodate the ligature pigtail in its desired position, close to the midline. The pigtail was pushed through the pierced hole, before the flap was fully replaced and re‐sutured.
An auxiliary labial archwire, with a vertical loop, was ligated at this point in piggyback fashion over the heavier base arch and its loop turned inwards and upwards. It was securely latched, in light horizontal contact, to the palatal mucosa, by the shortened and bent‐over twisted ligature. Active vertical extrusive force would now erupt the tooth vertically downward, towards the tongue. From that point, a direct approach to the archwire could then be made, without interference by the incisor root.
In a situation where a palatal canine is located very high up in the maxilla, at the level of and close to the midline and to the incisor apices, an open exposure is contraindicated. There is every likelihood that the exposure will close over in the immediate post‐surgical period, together with the possibility of loss of vitality of one or more of the incisors. The canine seen in Figure 5.6 was located across the midline and between the central incisor apices. The tooth was subsequently drawn posteriorly and vertically downwards, exiting in the mid‐palate and thereby avoiding damaging the incisor apices and permitting lateral movement to its place in the arch. The initial activation was performed at the surgeon’s chairside, immediately following completion of the exposure procedure.
Speed of eruption
When traction is applied to a palatally impacted canine in the closed eruption technique, the tooth may move rapidly, sometimes from a considerable distance, deep in the bone. As it exits the bone, it causes the very palpable bulge beneath the thick mucosa of the palate to increase in size. The thick mucosa will, in turn, create difficulty for the tooth to erupt through it. In such a circumstance, it is recommended that a small circular incision be made around the crown tip of the impacted tooth and the tissue removed to an extent that will re‐expose the tooth with an aperture not exceeding the circumference of its crown. Further traction will then erupt the tooth very rapidly. Delay in performing this simple procedure will over‐tax the anchorage unit and simply cause the anchor teeth to intrude and the overall archform to become disrupted.
The final treatment outcome
Several research groups, from various countries, have conducted studies on the effect of the open exposure technique on the post‐treatment pulpal and periodontal status of maxillary canines, following the orthodontic resolution of impacted teeth. A Norwegian group [31] identified an increased depth of periodontal pockets on the distal side of the impacted teeth as well as bone loss on the mesial side. The group from the University of Washington [32] examined patients with impacted canines that had been treated by undefined ‘conservative’ surgical procedures. They identified attachment loss, reduced alveolar bone height and frequent instances of pulp obliteration, discoloration and misalignment. They also found that the previously impacted canines were quite discernible and conspicuous in 75% of the treated cases, which was presumably associated with marred external appearance.
In our own study, our Jerusalem group of researchers examined the results of the treatment, by the closed eruption technique, of palatal canines and found an excellent appearance, with slightly deeper pockets and a 4% loss of alveolar bone support [8]. In addition, in relation to buccally ectopic maxillary canines, we found a minor reduction in the width of the attached gingiva, but otherwise a good general periodontal result [9].
Studies carried out by others have further corroborated the good clinical periodontal results of the use of the closed eruption technique, in both buccal and palatal canine cases [33].
Using a mixed sample of cases of impacted incisors and canines in their study [32], the Washington group carried out a comparison of the open (specifically the apically repositioned flap exposure) and closed procedures. With regard to those treated with the open surgical approach, they found poorer results in both periodontic measurement and aesthetic assessment and, with regard to buccal canines, they identified an increase in clinical crown length and a deterioration and unevenness in the gingival margins (Figure 5.7). They also noted loss of attachment and alveolar bone, frequently accompanied by vertical positional relapse of the erupted tooth, after the completion of treatment. They reasoned that during the tissue healing that occurs after the surgical repositioning, the horizontal mucosal lines undergo stretching and distortion during the incisal movement of the tooth. Once orthodontic control is released, vertical relapse occurs due to a contraction of these extended mucosal lines. By contrast, in the closed eruption cases, they found that clinical crown length and gingival appearance in the closed eruption group were similar to those of the unaffected (control) side, with a completely normal periodontal attachment and no evidence of post‐treatment relapse in incisor position.
Fig. 5.7 Treatment for the right buccally impacted maxillary canine was performed using an open exposure, apically repositioned flap technique. (a) The post‐treatment outcome shows a thick band of attached gingiva, but a long clinical crown with an unaesthetic lumpy appearance of the gingival margin. (b) The normally erupted canine of the left side is shown for comparison.
Impacted incisors are seen less frequently in the orthodontic office than are impacted canines. This accounts for the relative absence
