NEWSLETTERS
3rd Edition published April 2012
  • Fully revised and updated classic
  • Coverage expanded to include protocols for routine and for complex cases
  • Includes new chapter on extreme tooth displacement and complicating factors
  • Provides unparalleled coverage of the evidence base
  • Highly illustrated in full colour
  • Every imaginable tooth impaction

Price $170
Apply to www.wiley.com

Just out ! The Spanish translation of the 3rd edition
for details contact the publishers at www.amolca.com.ve




Designed by: www.drorzunz.net

The \"high-above-the-vestibulum\" canine

Published: September 2015

Bulletin #47 September 2015

The “high-above-the-vestibulum” canine

Compared with the palatally impacted maxillary canine, buccally impacted maxillary canines are less frequently seen, but they nevertheless occur in significant numbers in our patient intake for us to highlight their management in columns such as this. The higher up the canine, the more difficult it is to define it in strict bucco-lingual terms.

The reason why a buccally impacted canine has not erupted may simply be obstruction. In this category, there are those that are located in the line of the arch, with a mesial inclination. The cusp tip contacts the distal side of the lateral incisor and the canine is jammed between the root of the erupted premolar and lateral incisor. Anomalies, such as an odontoma which rarely occurs in this area, and pathologic entities such as an enlarged dental follicle/follicular or dentigerous cyst and invasive cervical root resorption will also prevent eruption.1

Assuming accurate diagnosis and elimination of the causal factor, these teeth may be moved as with any other tooth, provided an appropriate force level and direction may be brought to bear on them.

A number of these canines are diagnosed as being located at or above the height of the vestibulum. They are to be found in the narrowed apical area of basal bone and, in addition to their vertical traction, many are in need of a labial component of force. The surgical approach to these cases is from the labial side, even if a degree of palatal displacement is recognized. In this bulletin, we shall discuss the practical problems involved and ways of overcoming the serious technical difficulties connected with high buccal canines.

The unobscured high canine with a direct line to its place

In terms of surgical exposure, the window approach is probably the most commonly used and least advised method of accessing the tooth. It has the advantages of simplicity, insofar that a surgical flap does not have to be raised and suturing is not needed. It has further been encouraged by the appearance of advertisements in the journals for do-it-yourself laser surgical units extolling their efficacy in this specific context. However, the fact that the canine is at or above the vestibular mucosal reflection means that the opening will close down the moment the chairside assistant releases the retracted lip. The cut edges will then come together and, within days, heal over to render the tooth once again inaccessible. Even assuming eventual biomechanical success at bringing the tooth to its place, the initial location of the canine was high above the band of attached gingiva which covers the alveolar crest of the ridge or surrounds a persistent deciduous canine. Exposing it by the window technique means that, following its successful traction into its place in the arch, the canine will be invested on its labial side with oral non-gustatory mucosa, which is thin, delicate and highly mobile. Even simple tooth brushing is likely to injure it by tearing the epithelium and provoke frequent bleeding and, eventually, recession. In orthodontic terms it was a success, but by periodontal standards, it will become a progressively-deteriorating failure.

The alternative open exposure method is the apically-repositioned attached gingival flap.2 In this method, a partial thickness attached gingival flap is raised from the crest of the ridge and sutured higher up on the crown to the newly exposed canine. However, the presence of a high-above-the-vestibulum canine makes this approach impractical because of the extreme distance that the flap has to be transferred and because of the difficulty of attaching it there. Additionally it will leave a very broad area of periosteum that is concomitantly exposed to the oral environment.

FFF_fig_1a_c

Fig. 1a-c. Case #1. Two 3D views and a cross-sectional slice from the cone beam imaging of a patient with a very high horizontally oriented maxillary left canine (arrow). The scale rule on the right side of Fig. 1a shows that the tooth is approximately 30mms from its target location. Reprinted from Seminars in Orthodontics, Vol 16, Adrian Becker, Extreme Tooth Impaction and Its Resolution, Pages 222-233, Copyright (2010), with permission from Elsevier .

FFF Fig. 1d_1

Fig. 1d. A soft tissue surgical flap of attached gingiva from the crest of the ridge was reflected and an attachment bonded to the exposed tooth. The flap was re-sutured to its former place and the canine drawn down under the flap to its place. The deciduous canine was extracted when the canine was well advanced in its descent.

FFF_Fig._1e__f

Fig. 1e, f. the anterior and left side views of the dentition at the completion of treatment.

For this canine, the preferred surgical approach is the closed exposure technique, in which the surgeon raises the same surgical flap as with the apically repositioned attached gingival flap.3, 4 A small eyelet attachment is bonded to the tooth at the time of operation and the surgical flap re-sutured to its original place, with a gold chain or twisted steel ligature being drawn down and exiting the tissues at the sutured edge of the replaced flap. The tooth is biomechanically drawn down by elastic traction from the chain/twisted steel connector to the main arch, under the flap, until it emerges through attached gingiva at the crest of the ridge (Fig. 1).

FFF_Fig._2a_d

Fig. 2a. Case #2. Crescini’s procedure. The deciduous canine has been extracted and the permanent canine exposed with a full attached gingival flap derived from the gingiva surrounding the vacant socket.

Fig. 2b. An attachment has been bonded to the canine and the twisted steel ligature drawn down through the vacant deciduous tooth socket.

Fig. 2c. An occlusal view to show the ligature exiting the socket.

Fig. 2d. The full flap is sutured back to its former place and immediate traction is applied by direct engagement of the ligature to a “swinging gate” type of active archwire.

A refinement of this technique was described by Crescini5 in which the connector is passed through the socket of the deciduous canine, following the simultaneous extraction of that tooth. Drawing the permanent canine down though the organizing socket tissue offers the advantage of retaining the buccal plate of alveolar bone and assuring enhanced labial bone support of the finally erupted canine (Fig. 2).

The high canine obscured by roots of adjacent tooth

Video movie clip of case #3 click here http://youtu.be/WX8e6YuhDfE

Fig. 3. A video movie clip showing adequate space between the crowns of the erupted premolar and lateral incisor for the maxillary left impacted canine, but inadequate space apically due to tipping of the two teeth and to the unusual mesial curvature of the palatal root of the premolar. Courtesy of Dr. Shmuel Einy.

In many cases, we see adequate space in the erupted dental arch to accommodate the impacted canine, which makes it appear that the canine has a clear unobstructed path to its place. However, a tipped premolar and/or lateral incisor may be present to constrict the potential eruption path of the canine enough to obstruct it. Just occasionally one may come across an upright and unrotated premolar which has a strong mesial curve of one of its two roots, which is difficult to see on routine plane film radiographs and requires cone beam CT (Fig. 3) for proper diagnosis and treatment planning (see Bulletin #6, December 2013 and Bulletin #33, May 2014 on this website).

Once space has been provided – all the way up to the apices of the teeth in the same manner that we are required to prepare for the placement of an implant - the tooth then becomes an unobscured high-above-the-vestibulum canine and its surgical and orthodontic treatment planning is detailed above.

The high labial canine and inadequate space in the dental arch – ab initio or iatrogenic

For the majority of cases, the patient is in the permanent dentition stage, with insufficient space for the canine to be accommodated in the dental arch. Typically, the deciduous canine is over-retained and in proximal contact with the lateral incisor and first premolar. Space must first be made in order to accommodate the canine. Once space has been opened, the surgical options remain the same as with the unobstructed canine.

A word of caution: In order to create space, the orthodontist will typically use an open coil spring compressed between the brackets of the two adjacent teeth. The movement always carries with it a degree of tipping, which means that while space at crown level of the premolar and incisor is enlarged, the root apices of these teeth may be tipped towards each other, narrowing the eruptive path of the canine. Secondly, the space opening force is applied to a bracket on the labial/buccal surface of the adjacent teeth. The point of application is several millimeters from the center of rotation of the tooth. This will generate a rotational component acting on the two teeth and is particularly important in relation to the premolar. The buccal root will rotate disto-lingually, but the palatal root will rotate mesio-buccally and its apex may come to impinge on the unerupted canine. (see Bulletin #3, September 2011 and Bulletin #7, January 2012 on this website).

The high labial canine for which space cannot be prepared in advance

The canines in this category present with a degree of transposition with either the premolar or the lateral incisor. The orientation of the long axes of one or other of the teeth is abnormal due to a misplacement of its root apex. Because the root apices may be reversed or otherwise dislocated in the mesio-distal and/or bucco-lingual planes, attempts at initial root movement would likely create a clash between the two. Theoretically, the 3-D inter-relations between the two involved teeth allow for multiple positional options but, for the most part, the canines are to be found on the buccal/labial side of both the first premolar and the lateral incisor.

For the canine/premolar transposition, the deciduous canine may have a long unresorbed root with a fair-to-good prognosis. The extraction choices would then be as follows:-

1. Extract the deciduous canine and realign canine and premolar in their appropriate locations

2. Extract the deciduous canine and realign canine and premolar in their reversed locations

3. Extract the permanent canine and leave the deciduous canine in place

4. Extract the premolar and realign the canine in place.

Video movie clip of case #4a click here http://youtu.be/3DnNeov3DLM

Fig. 4a. Case #4. A video movie clip of the location and orientation of the right maxillary canine vis-a-vis the roots of the premolars.

This impaction can only be successfully resolved if the canine is first moved buccally to clear the roots of the premolars.

FFF_Fig._4b_d

Fig. 4b-d. Pre-surgical set-up with heavy round 0.020” base arch and auxiliary labial archwire carrying a horizontal loop opposite the canine area, in its passive state, seen from 3 different aspects. Note the absence of a bracket on the lateral incisor, due to the proximity of the canine to early resorption of the incisor apex.

In the illustrated case (Fig. 4), the root apex of the canine is located more distally than is normal and the body of the canine is above the apices of the premolars (Fig. 4a). There is no possibility of direct vertical traction to a labial archwire. The tooth must first be drawn buccally from a point above the height of the vestibulum, to clear its path over the premolars, before it can be drawn downward.

This cannot be done using a gold chain nor with a twisted steel ligature, because both swing freely in the eyelet attachment. A twisted steel ligature may only be used if it is prepared in heavier 0.014” soft steel, welded to the eyelet base, to convert it into a rigid arm and to eliminate the swing. Its buccal movement may then be controlled at a distance along its using a shorter loop in an auxiliary archwire.6 However, its exit from the tissues is initially through the middle of the replaced flap, in oral mucosa.

FFF Fig. 4e-i_1

Fig. 4e. A full labial flap is raised from the attached gingiva surrounding the socket of the extracted deciduous canine.

Fig. 4f. An eyelet is bonded and the twisted steel ligature is of 0.014” soft wire, welded to the steel pad base to create rigidity and prevent swing in the eyelet.

Fig 4g. The horizontal loop in the auxiliary archwire is raised to engage the twisted ligature close to the tissues.

Fig. 4h, i. Following re-suturing of the flap, the activated loop does not irritate the lip, due to rigidity of the ligature wire and the elimination of the free swing of the ligature in the eyelet resulting from welding the ligature to the bonding pad. Note that the loop itself reaches only about half way up towards the height of the tooth and will therefore not ulcerate the mobile mucosa in the height of the vestibulum.

As the tooth responds, the loop of the auxiliary archwire becomes more and more prominent and the patient is likely to complain of the loop interfering with lip function and movement and ulcerating the inner aspect of the lip. The loop may then be pushed towards the ridge under light finger pressure and the ligature curled around it to re- approximate it to the oral mucosa and, thus, re-activating the labial traction. Two or three such re-activations should bring the canine sufficiently buccal to be palpable high in the vestibulum and even extra-orally in the overlying skin of the face.

A second word of caution: It is important to check the position of the canine very closely by palpation and not to permit the patient to miss appointments. Because the range of activation of the loop of the auxiliary arch is very broad, leaving it unchecked for more than a few weeks will see the tooth entering the soft tissue of the lip, without its ever erupting into the mouth!

Once the canine is palpable having exited the alveolar bone, the direction of traction is altered by an elastic tie from the twisted steel ligature direct to the archwire, with the tooth still under the oral mucosa and aimed towards the attached gingiva. As it moves further down and before it threatens to break though the oral mucosa, a second surgical flap may be needed with the aim of apically repositioning attached gingiva on the crown of the tooth, as outlined above.

Basically the same choices are valid for the canine/lateral incisor transposition, except that in this case, the factor of the patient’s appearance takes on a much more dominant role. Thus:-

1. Extract the deciduous canine and realign canine and lateral incisor in their appropriate locations

2. Extract the deciduous canine and realign canine and lateral incisor in their reversed locations

3. Extract the permanent canine and leave the deciduous canine in place

4. Extract the lateral incisor and realign the canine in its place.

Options #2, 3 and 4 represent compromise solutions which may be the optimal outcome in some cases. Their surgical and orthodontic resolution is then straightforward. Bringing the permanent canine to its normal place is in theory ideal, but the operative choice should be entirely dependent on the individual merits of each case.

Because of the anatomy of the immediate area, a labial canine is usually quite high up relative to the labially proclined incisors and it is usually held there by the incisor roots themselves. For the canine to be drawn to its place, it must proceed distally, labially and vertically downward, as it skirts around the incisor roots. However, the more the tooth is drawn down, the greater the amount of labial movement needed to outflank them, because of the labial axial orientation and proclination of the incisor crowns, relative to their roots. This brings the tooth in conflict with the confines of the labial periosteum of the alveolar bone and it should come as no surprise that there is usually a poorer prognosis for the periodontal outcome of a successfully aligned labial canine.

FFF_Fig._5a_d

Fig. 5a, b.Case #5. Initial panoramic and lateral cephalometric views to show the identical bilateral canine impaction. The lateral cephalogram shows the long axes of the vertically-oriented and precisely superimposed central incisors (white dotted line) and the same precise superimposition of the lateral incisors, with their steep almost horizontal orientation (blue dotted line). The bilaterally identically-oriented canines (yellow dotted line) can be seen to be palatal to the central and labial to the lateral incisors.

Fig. 5c. A composite representation of cross sectional cuts to show the labial relationship of the right and left canines (#13 & #23) to the right and left lateral incisors (#12 & #22) and their lingual relationship to the right and left central incisors (#11 & #21).

Fig. 5d. An anterior CBCT screen shot to show the inter-relation between unerupted canines and the incisors.

FFF_Fig._5e

Fig. 5e. The clinical intra-oral occlusal view set up immediately pre-surgery shows the passive mode of the auxiliary labial archwire. Note the wide angular difference in long axis orientation of the lateral and central incisors - a clinical clue of the location of the permanent canines.

An example of the ideal approach can be found in Bulletin #16, November 2012 on this website. In the case illustrated here (Fig. 5), the pattern of the bilateral canine impaction shows a remarkable similarity between left and right sides. Seen on the cephalogram (Fig. 5b), there is an identical right-left superimposition of the 6 anterior teeth. Both maxillary canines are labial to the lateral incisors but, despite the fact that they cross to the lingual side of the central incisors, their exposure and traction must be on the labial side.

FFF_Fig._5f_i

Fig. 5f. A distolabial approach is made to expose the left high canine. An eyelet attachment is bonded and the twisted steel ligature will be passed through the oral mucosal part of the flap.

Fig. 5g. The loops of the auxiliary arch are engaged in the steel ligature, which holds the loops close to the oral mucosa. In this way, labially-directed traction is applied to the buried teeth.

Fig. 5h, i. Four months later, the right canine has suddenly erupted through the oral mucosa (sic) and the patient complains of pain and ulceration of the inner surface of the lip, due to the abnormal prominence of the auxiliary loop.

These "bucco-lingual," cross-the-ridge, canines are exceptionally difficult cases to treat.

References

1. Becker A, Abramovitz I, Chaushu S. Failure of treatment of impacted canines associated with invasive cervical root resorption. Angle Orthodontist, 2013, 83:870-876.

2. Vanarsdall RL, Corn H. Soft-tissue management of labially positioned unerupted teeth. American Journal of Orthodontics, 1977; 72: 53–64.

3. McBride LJ. Traction – a surgical/orthodontic procedure. Am J Orthod 1979; 76: 287–299.

4. Becker A, Chaushu S. Palatally impacted canines: The case for closed surgical exposure and immediate orthodontic traction. American Journal of Orthodontics and Dentofacial Orthopedics 2013;143:451-459.

5. Crescini A, Clauser C, Giorgetti R, Cortellini P, Pini Prato GP.Tunnel traction of intraosseous impacted maxillary canines: a threeyear periodontal follow-up. American Journal of Orthodontics and Dentofacial Orthopedics 1994; 105:61-72

6. Kornhauser S, Abed Y, Harari D, Becker A: The resolution of palatally-impacted canines using palatal-occlusal force from a buccal auxiliary. American Journal of Orthodontics and Dentofacial Orthopedics 110:528-534, 1996.