bishara caninos impactados management

Clinical Management of Impacted Maxillary Canines Samir E. Bishara

Almost everything I know or f ind out th~)ugh experience and study has, I find, appeared in print in one place or anoth< and often many years ago. The saving grace is that what I am about to present may have been forgotten or overlooked.--Wilbur D. Johnston 1

Ectopic eruption and impaction of canines is a frequently encountered clinical problem. The incidence of impaction ranges between 1% and 3%. The cause of canine impaction can be the result of localized factor(s) or can be a polygenic multifactorial inheritance and associated with other dental anomalies. There are a number of possible sequelae to canine impactions, ranging from loss of space in the arch to resorption of the roots of the neighboring teeth. Although the management of the ectopically erupting teeth necessi- tates the combined expertise of a number of clinicians, the orthodontist should have the primary responsibility of coordinating these efforts to provide the patient with the optimal treatment options with the most stable and favorable outcome. (Semin Orthod 1998;4:87-98.) Copyright © 1998 by W.B. Saunders Company

T he ectopic e rupt ion and impact ion of maxillary p e r m a n e n t canines is a frequently encoun te red

clinical problem. The diagnosis and t rea tment of this p roblem usually requires the expertise and cooperation of the general practitioner, pediatric dentist, oral surgeon, and periodontis t as well as the orthodontist .

Incidence of Canine Impaction

Dachi and Howell ~ repor ted that the inc idence of maxillary canine impact ion is 0.92%, whereas Thilan- der and Myrberg a est imated the cumulative prevalence of canine impact ion in 7- to 13-year-old chi ldren to be 2.2%. Conversely, in a Saudi populat ion, the incidence was estimated to be 3%.4 Ericson and Kurol 5 est imated the incidence in the Swedish populat ion at 1.7%. Impactions are twice as c o m m o n in females (1.17%) than in males (0.51%). Of all individuals with

From the Department of Orthodontics, CoUege of Dentistry, University of Iowa, Iowa City, IA.

Address correspondence to Samir E. Bishara, BDS, DDS, DO*~ tho, MS, Department of Orthodontics, College of Dentistry, Univew sity of lowa, Iowa Cit); IA 52242.

Copy~gt~t © 1998 by W.B. Saunders Company 1073-8746/98/0402-000458.00/0

maxillary impacted canines, it is est imated that 8% have bilateral impactions. The inc idence of mandibular canine impact ion is 0.35%. 2 According to Yamaoka et al, 6 there was no difference in the prevalence of completely impacted canines in the edentulous as compared with the denta te maxillae.

Because maxillary canines are impacted more frequently, the emphasis of this presentat ion is on their management . However, the general principles of diagnosis and t rea tment can be applied to both the maxillary and mandibula r teeth.

Developmental Considerations

According to Dewel, 7 maxillary canines have the longest per iod of development , as well as the longest and most tortuous course to travel f rom their point of format ion, lateral to the pir i form fossa, until they reach their final destination in full occlusion.

Dur ing their course o f development , the crowns of the p e r m a n e n t canines are intimately related to the roots of the lateral incisors. Broadbent s caut ioned against the early correct ion of the flared and distally t ipped lateral incisors, for tear of ei ther impact ing the canines or resorbing the roots of the lateral incisors.

Seminars in Orthodontics, Vol 4, No 2 (June), 1998: pp 87-98 8 7

88 Samir E. Bishara

Causes of Maxillary Canine Impaction In general, the causes for retarded eruption of teeth may be either generalized or localized. 9,1° Generalized causes include endocrine deficiencies, febrile dis- eases, and irradiation, among others. The most com- mon causes for canine impactions are usually localized and are the result of any one or a combination of the following factors: (1) tooth size-arch length discrepan- cies, (2) prolonged retention or early loss of the deciduous canine, (3) abnormal position of the tooth bud, (4) the presence of an alveolar cleft, (5) ankylosis, (6) cystic or neoplastic formation, (7) dilaceration of the root, (8) iatrogenic, (9) trauma, u and, finally, (10) idiopathic, including primary failure of eruption. 12

More recently, the absence of the maxillary lateral incisoi, variation in its root size, and variation in the timing of its root formation have been implicated as important causative factors associated with canine impaction.13-15 It seems that the presence of the lateral incisor root with the right length, formed at the right time, are important variables needed to guide the mesially erupting canine in a more favorable distal and incisal direction. Becker et a115 reported a 2.4 times increase in the rate of palatally impacted canines adjacent to missing lateral incisors when compared with the general population. Stellzig et a116 found that in 35% of the cases there was a correlation between peg-shaped laterals and palatal impactions.

This multifactorial cause may explain why canine impactions occur when both the rest of the dentition and other dental relationships are apparently normal, with sufficient space available for the eruption of the impacted tooth, whereas in other cases it is associated with other genetic anomalies present in adjacent or distant teeth. As a result, canine impaction can be described as either an isolated localized phenomenon or of polygenic nmltifactorial inheritance37 The genetic origin in some of the impacted canine cases is supported by the presence of other dental anomalies, concomitant with impaction, as well as its bilateral occurrence, sexual dimorphism, familial occurrence, and population differences3 s

Sequelae of Impaction Shafer et alm suggested tbat the following sequelae might be associated with canine impaction: (1) labial or lingual malpositioning of the impacted tooth, (2) migration of the neighboring teeth and resultant loss of arch length, (3) internal resorption, (4) dentigerous cyst formation, (5) external root resorption of the impacted as well as the neighboring teeth, (6) infec- tions particularly associated with partial eruption, (7) referred pain, and (8) various combinations of these sequelae, m It is estimated that 0.71% of children in

the 10- to 13-year age-group have resorbed permanent incisor roots because of the ectopic eruption of maxillary canines. 2° Conversely, the presence of the impacted canine may cause no untoward effects during the lifetime of the individual.

These potential complications, as well as others that are detailed later, point to the need for closely observing the development and eruption of these teeth during the "routine" periodic dental examination of the growing child. In a clinical-pathological study, Fukuta et a121 evaluated 11 patients with various degrees of radiolucencies around the crowns of impacted teeth. Most of the cases were diagnosed clinically as being dentigerous cysts. However, when examined histopathologically, the features of the lesions were similar to those of normal dental follicular tissue around developing teeth.

Diagnosis of Impaction The diagnosis of canine impaction is based on clinical as well as radiographic examinations.

Clinical Evalua t ion

It has been suggested that the following clinical signs might be indicative of canine impaction: (1) delayed eruption of the permanent canine or prolonged retention of the deciduous canine beyond 14 to 15 years of age, (2) absence of a normal labial canine bulge; in other words, either inability to locate canine position through intraoral palpation of the alveolar process or the presence of an asymmetry in the canine bulge noted during alveolar palpation, (3) presence of a palatal bulge, and (4) delayed eruption, distal tipping, or migration (splaying) of the lateral incisor.

According to Ericson and Kurol, 2° the absence of the "canine bulge" at earlier ages should not be considered as indicative, that is, diagnostic, of canine impaction. 2° In their evaluation of 505 schoolchildren between 10 and 12 years of age, they found that at 10 years, 29% of the children had nonpalpable canines, but only 5% at 11 years of age, whereas at later ages only 3% had nonpalpable canines. Therefore, for an accurate diagnosis, the clinical examination should be supplemented with a radiographic evaluation.

Radiographic Localization of the Impacted Tooth

Although various radiographic exposures including occlusal fihns, panoramic views, and lateral cephalograms can help in evaluating the position of the canines, in most cases periapical films are uniquely reliable for that purpose.

Periapical films. A single periapical film provides the clinician with a two-dimensional representation of

Impacted Maxillary Canines 89

the denti t ion. In o ther words, it would relate the canine to the ne ighbor ing teeth both mesiodistally and superoinferiorly. To evaluate the position of the canine buccolingually, a second periapical film should be obtained using one of the following methods~2:(1 ) Tube-shift technique or Clark's rule, (9) buccal-object rule. These methods have been fully described else- where in this issue.

Ocelusalfilms. These also help de te rmine the buc- colingual position of the impacted canine in conjunc- tion with the periapical films, provided that the image of the impacted canine is not super imposed on the o ther teeth.

Extraoral films. Frontal and lateral cephalograms can sometimes be of aid in de te rmin ing the posit ion of the impacted canine, particularly its relat ionship to o ther facial structures, such as the maxillary sinus and the f loor of the nose. Panorex films are also used to localize impacted teeth in all three planes of space, much the same as using two perapical fihns in the tube-shift method, with the unders tanding that the source of radiation comes f rom beh ind the patient; thus, the movements are reversed for position. 23

The p roper localization of the impacted tooth plays a crucial role in de te rmin ing (1) the feasibility as well as the p roper access for the surgical approach, (2) the p roper direct ion for the application of o r thodon- tic forces, and (3) the extent of the root resorpt ion and damage to the adjacent teeth.

Root Resorption and Radiographic Evaluation

According to Ericson and Kurol, 24 with the use of periapical fihns, the clinician is able to evaluate the position of the canine with sufficient accuracy in 92% of the cases. However, in only 37% of the cases were they able to project the lateral incisor image completely away from that of the canine (Fig 1).

The ability to evaluate the condi t ion of the lateral incisor root is of great impor tance to the clinician because 80% of the teeth resorbed by the ectopically e rupt ing canines were found to be lateral incisors (Fig 2F, G). Ericson and Kuro124 est imated that 0.7% of the children in the 10- to 13-year age-group have resorbed p e r m a n e n t incisors caused by ectopic e rupt ion of the maxillary canines. Using a more elaborate radiographic technique, polytomography, Ericson and Kurol found that the n u m b e r of teeth that were diagnosed as resorbed almost doubled. Of conce rn is that in half of all the teeth showing resorption, the lesion ex tended into the pulp. Fur thermore , 50% of the cases had ei ther labial or lingual resorption, which would escape detect ion when using rout ine periapical radiographic evaluations. 25

As a result of these difficulties, a n u m b e r of authors suggested tile use of computed tomography (CT) in

Figure 1. The super imposed images of the lateral incisor and canine can be separated in only 37% of the cases.

cases with impacted canines. Elefteriadis and Athana- siou, 26 Kurol, 27 and Schmuth et al 2s suggested that CT provides more detai led informat ion than conven- tional radiographs, including the location and extent o f the resorbed roots as well as the posit ion of the impacted canines in relation to the incisors. The major concern with the use of CT is the need to reduce the radiation exposure to the patient. In ano ther study by Schuller and Freisfeld 29 on 35 teeth examined by high-resolution CT, only five patients did no t show evidence of damage to the remaining teeth. Conversely, in the remaining cases, the average extent of the resorpt ion of the incisor teeth was 4.5 ram. This resorpt ion has been observed ex tending to the pulp at as early as 10 years of age. 25

Dental Follicle, Dentigerous Cyst, and Root Resorption

No correlat ion was found between the width of the dental follicle and resorpt ion of the incisor roots.

Figure 2. (A-E) Intraoral photographs of the dentition of a patient with a Class II malocclusion with an impacted maxillary right canine and ectopic labially erupting left canine. (F-G) Panoramic and periapical views showing the position of the impacted canine and the partial resorption of the root of the lateral incisor. (H) Periapi- cal film showing new bone filling the bony defect created by the surgical removal of the impacted canine.


Figure 2. (cont 'd) . (I-M) Intraoral photographs o f the dent i t ion 1 year after complet ion of treatment. Notice that the left canine was replaced by the first premolar. The right canine was al igned and retracted after the extraction of the first premolar. The molar relat ionship is Class II.

Ericson and Kurol 2-~ observed that the canine dental follicle was 3 to 5 mm wide in 19% of the cases and less than 3.0 m m in 81%. Conversely, the canine dental follicle exceeded 3.0 mm in 23% of the subjects with root resorption and in 24% of the subjects with no lateral incisor root resorption. 25 Although, tradition- ally, increased width of the dental follicle was thought to be associated with cystic format ion, this assumption has not been substantiated, and a definitive diagnosis can only be made through a histopathological evaluation. 21

Accord ing to Ericson and Kurol, 24 the pressure of the follicle close to the root of the lateral incisor does

no t cause surface resorpt ion as such. Kuro127 suggested two basic mechanisms that could initiate root resorpt ion in the 12% of the subjects affected: (1) crown-root contact causing damage or necrosis to the ce raen tum and (2) proximity without actual contact between the crown and the root might be sufticient to initiate the osteoclastic act ivi tyS

Prevention of Maxillary Canine Impaction I f the clinician detects early signs of ectopic e rupt ion of the canines, an a t tempt should be made to prevent

92 Samir E. Bishara

their impact ion and its potential sequalae. Selective extraction of the deciduous canines as early as 8 or 9 years of age has been suggested by Williams 3° as an interceptive approach to canine impact ion in Class I uncrowded cases. Ericson and KuroP 1 suggested that the removal of the deciduous canine before 11 years of age will normalize the position of the ectopically e rupt ing p e r m a n e n t canines in 91% of the cases, if the canine crown is distal to the midl ine of the lateral incisor. Conversely, the success rate is only 64% if the canine crown is mesial to the midl ine of the lateral incisor, as seen in Figure 1.31 Another impor tan t factor that will affect the prognosis, in addit ion to the position of the impacted tooth, is the severity of its angulat ion; that is, the more incl ined the tooth is, the less is the probability that it will spontaneously erupt.

Treatment Alternatives

Every pat ient with an impacted canine must undergo a comprehensive clinical and radiographic evaluation of the malocclusion. The clinician should then consider the various t rea tment options available for the patient, including (1) no t rea tment if the pat ient does no t desire it. In such a case, the clinician should periodically evaluate the impacted tooth for any pathological changes. The long-term prognosis for retain- ing the deciduous canine is poor, regardless of its root length and how aesthetically acceptable its crown. This is because, in most cases, the root will eventually resorb, and the deciduous canine will have to be extracted (Fig 2F, G); (2) autotransplantat ion of the canine:~2,33; (3) extraction of the impacted canine and moving a first premolar in its position (Fig 2); (4) extraction of the canine and posterior segmental osteotomy to move the buccal segment mesially to close the residual space34; (5) prosthetic rep lacement of the canine; and finally (6) surgical exposure of the canine together with or thodont ic t rea tment to br ing the tooth into the l ine of occlusion. This is obviously the most desirable and r ecommended approach.

In a study by Sange and Thi lander 35 on transalveolar t ransplantat ion, of 56 maxillary impacted canines, only two were lost because of poor oral hygiene and tooth fracture after an average 4.7 years. In another study by Schatz a n d J o h o 36 on 20 t ransplanted maxillary canines, they found that in the 13- to 20-year age-group, pulp vitality remained in 80% of the patients, whereas in the 20- to 48-year age-group, all impacted canines required root canal therapy.

When to Extract an Impacted Canine

The extraction of the labially e rup t ing and crowded canine, as unsightly as it may look, is contraindicated (Fig 2). Thei r extractions might temporarily improve

the aesthetics bu t may complicate and compromise the or thodont ic t rea tment results, inc luding the abil- i t , / to provide the pat ient with a funct ional occlusion and an attractive smile. The extraction of the canine, a l though seldom considered, might be a viable opt ion in the following situations: (1) if it is ankylosed and cannot be transplanted; (2) if it is unde rgo ing external or in ternal root resorption; (3) if its root is severely dilacerated; (4) if the impact ion is severe, for ex- ample, if the canine is lodged between the roots of the central and lateral incisors, and or thodont ic move- men t will jeopardize these teeth (Fig 2E G); (5) if the occlusion is acceptable, with the first premolar in the position of the canine and with an otherwise functional occlusion with well-aligned teeth (Fig 2B); (6) if there are pathological changes, such as cystic formation, infection, etc., and the pat ient does no t desire or thodont ic treatment.

Palatal Versus Labial Impactions

It is estimated that the incidence of palatal impaction, exceeds that of labial impact ion by a ratio of at least 3:137 and up to 6:l.16jacoby ~a thought that it is difficult to establish an accurate rate for palatal versus labial impaction. This he at t r ibuted to the difficulty in de te rmin ing whether a labially impacted tooth might eventually e rupt on its own, often fur ther superiorly and labially to its normal position. Jacoby further observed that roughly 85% of palatally impacted canines had sufficient space for e rup t ion into the dental arch. Conversely, only 17% of the labially une rup t ed maxillary canines appeared to have sufficient space for erupt ion, that is, 83% showed an arch length deficiency. This suggests that for labially impacted canines, arch length deficiency is often a pr imary causative factor. 16,'~8

As stated earlier, ectopic labially posi t ioned canines may erupt on their own without either surgical exposure or or thodont ic treatment, frequently high in the sulcus or alveolar ridge (Fig 2C). Conversely, palatally impacted canines seldom erup t without interven- t i onY It is believed that this impeded e rupt ion is caused by the thickness of the palatal cortical bone as well as the dense, thick, and resistant palatal mucosa.

Palatally impacted canines are more often incl ined in a hor izonta l /ob l ique direction, whereas labial impactions usually offer a more favorable vertical angulation. Yet the latter are still considered difficult because of the needed delicacy in manag ing the associated hard and soft tissues.

Management of the Palatally Impacted Canine

Numerous surgical methods exist for exposing the impacted canine and br ing ing it to the line of occlu-


sion: two of the most commonly used methods are (1) surgical exposure and allowing for natural e rupt ion and (2) surgical exposure with the p lacement of an auxiliary at tachment. Or thodont ic forces are subse- quently applied to the a t tachment to move the impacted tooth.

Surgical Exposure to Allow for Natural Eruption to Occur

This m e t h o d is most useful when the canine has a correct axial inclination and does not need to be upr ighted dur ing its erupt ion. The progress of canine erupt ion should be mon i to red with roentgenograms, using reference points such as an adjacent tooth or the arch wire.

Clark 39 r e c o m m e n d e d placing a polycarbonate crown over the impacted tooth after its surgical exposure. The crown should be made long enough to extend through a window cut in the palatal tissue. The crown is then cemented with a surgical paste or regular cement. 39 Often, 6 months to a year may elapse before the impacted tooth has e rup ted sufficiently to pe rmi t removal of the polycarbonate crown and its rep lacement with an or thodont ic at tachment . If the tooth fails to erupt, Clark 39 r ecommends the removal of any cicatricial tissue sur rounding the crown.

The main disadvantages of this approach are the spontaneous but slow canine erupt ion, the increased t rea tment time, and the inability to inf luence the path of e rupt ion of the impacted canine.

Surgical Exposure With the Placement o f an A u x i l i a r y

After the surgical exposure of the impacted tooth, an auxiliary is a t tached to the crown of the tooth. Such an auxiliary can be ei ther a bracket, preferably incorporat- ing a hook, or an eyelet directly b o n d e d to the enamel surface.

Two approaches are generally r e c o m m e n d e d in regards to the t iming of placing the at tachment:

l . Lewis 4° prefer red a two-step approach. First the canine is surgically uncovered and the area packed with a surgical dressing to avoid filling-in of tissues a round the tooth. After wound healing, within 3 to 8 weeks, the pack is removed and an a t tachment is placed on the impacted tooth.

2. The second m e t h o d is a one-step approach, that is, the a t tachment is placed on the tooth at the t ime of surgical exposure (Fig 3). The tissues over the a t tachment should be excised and a per iodonta l pack or a glass i onomer cement placed. 4. The zinc o x i d e / e n g e n o l pack will minimize pat ient discom- fort and prevent the granulat ion tissues f rom cover-

Figure 3. Palatally impacted canine, after its surgical exposure, bonding, and a t tachment and force application. A light force f rom an alasdk chain is transmitted to the tooth and at tached to a relatively stiff arch wire (.018 × .029). The combina t ion of light force and stiff wire minimizes undesirable reactive movements of the anchor teeth.

ing the a t tachment before tile clinician is ready to apply traction forces on the impacted tooth. This approach is particularly r e c o m m e n d e d for palatally impacted teeth. One of the impor tan t advantages with such an approach is that when the force is appl ied to the impacted tooth, the clinician is able to visualize and bet ter control the direct ion of tooth movement . This avoids moving the impacted tooth into the roots of the ne ighbor ing teeth.

Earlier methods of uncover ing impacted canines advocated radical bone removal to expose the crown of the impacted tooth and to remove all bony ob- stacles and provide an easier path for tooth movement. McDonald and Yap 42 evaluated the relationship between the a m o u n t of bone removed dur ing surgical exposure and the subsequent bone loss a round the impacted tooth. They found that the more bone that was removed initially, the greater was the bone loss after o r thodont ic t reatment . Kohavi et a143 compared the per iodonta l health of canines exposed with a " radica l" exposure with canines exposed with a more conservative " l igh t" exposure. In the latter group, soft and hard tissues were only sufficiently removed to allow for the p lacement of a bond, but the exposed area was kept coronal to the cemen to -enamel junc t ion (CEJ). Comparisons between the two groups indicated the absence of significant differences in the plaque index, gingival index, pocket depth, or at tached gingiva after t reatment. Howevei; there were significant differences in bone support , that is, alveolar bone support in the "heavy exposure" group was reduced.

94 SamitE. Bishara

It was conc luded that exposure of the CEJ was a critical variable and should be avoided both as a surgical objective dur ing surgery or when placing a wire lasso with or without a gold chain. Kohavi et a143 fur ther suggested that " l ight movements , " such as tipping, cause significantly less bone loss than "heavy move- m e n t " such as torque dur ing the traction of tile impacted tooth.

It therefore can be conc luded that the combined effects of " l igh t" surgical exposure, " l ight" o r thodon- tic movements , and " l ight" o r thodont ic forces are beneficial to the future per iodonta l heal th of tile tooth. This is because they minimize the loss of alveolar bone support and potential injury to the tooth dur ing traction.

In exposing an impacted tooth, only enough bone should be removed to allow for the p lacement of a bonded bracket, and dur ing surgery, the CEJ should not be intentionally exposed.

Methods of Attachment Different methods of a t tachment to the impacted tooth have been suggested, including, crowns, wire ligatures, chain links, bands, and directly b o n d e d brackets.9, 44

The use of a circumferential , dead soft, l igature wire (lasso) as an a t tachment a round the cervical area of the tooth has been a fairly c o m m o n method. Such an approach should be discouraged because too m u c h bone needs to be removed to place the wire a round the tooth c i rcumference. This "heavy exposure ," as indicated earlier, increases the risk of injuring the ne ighbor ing teeth. Fur thermore , the incidence of external root resorpt ion has been found to increase by 8% to 14% when this technique was used. 45,46 All increased inc idence of ankylosis was also repor ted dur ing or thodont ic treatment. The ankylosis was associated with the external root resorption, and the teeth were found to be nonres torable and had to be extracted. 45

It is strongly r e c o m m e n d e d that the surgical exposure of the impacted tooth should be conservative to allow for the p lacement of a b o n d e d bracket, eyelet, or but ton (Fig 4). For deep intraosseous impacted canines, some advocate the use of a gold chain that passes th rough a long tunnel created between the impacted tooth and the empty socket of the extracted deciduous canine. 47 In general, the use of a wire lasso a round the impacted tooth should be avoided.

Management of Labially Impacted Canines As stated earlier, labial impact ion of the maxillary canine is less f r equen t than palatal impact ion and is

Figure 4. Labially impacted canine, after its surgical exposure. An apically reposi t ioned flap was used to provide a band of a t tached gingiva to the impacted tooth. The initial direct ion of the force should be to move the tooth away f rom the ne ighbor ing teeth to avoid their injury.

often caused by insufficient arch length. As a result, the canine is often posi t ioned high in the alveolar bone and erupts th rough the alveolar mucosa (Fig 4). Fourn ie r et aP 7 suggest that labially impacted teeth with a favorable vertical posit ion may be treated initially by surgically exposing them but without the application of a traction force. They consider that in younger patients, the tooth will e rupt on its own after surgical exposure, whereas in older patienks, traction is almost always indicated.

The absence of an adequate band of at tached gingiva a round the e rup t ing canine may cause inflam- mat ion of the per iodont ium. Vanarsdall and Corn 4s emphasized that it is hazardous to move teeth in the presence of inf lammation. Tissue resistance to the stresses of mastication and funct ion are less than optimal, and loss of per iodonta l suppor t is possible if precautions are not taken to alleviate such potential problems.

It is r e c o m m e n d e d that surgical procedures designed to expose impacted canines e rupt ing through alveolar mucosa should sinmltaneously provide a band of a t tached gingiva to the exposed tooth. Otherwise, improper soft tissue m a n a g e m e n t may lead to muco- gingival recession and loss of alveolar bone.

Before exposing a labially impacted canine, careful considerat ion should be given to creat ing sufficient space to allow for the canine to be properly posi t ioned in the dental arch. The created space will also provide an adequate zone of a t tached gingiva that can act as a donor site for a partial-thickness, apically or laterally reposi t ioned flap.

~anarsdall and Corn as suggested that the flap conta ining the keratinized tissue should be placed to cover the CEJ and 2 to 3 m m of the crown. They expla ined that the advantages for such an approach


include: (1) the new gingival attachment prevents marginal bone loss and gingival recession frequently encountered with surgically exposed labially impacted teeth; (2) this method avoids the need for a series of dressings or the placement of a polycarbonate crown to prevent the tooth from being covered by granula- tion tissue; (3) the procedure is indicated even in teeth located beyond the vestibular depth or muco- buccal fold (Fig 4); (4) the apical repositioning of the flap allows for greater movement of the marginal tissue. This approach will minimize tension on the gingival tissues, particularly in those cases in which the canine, with its newly attached gingival tissue, needs to be moved occlusally a long distance to reach its correct position.

The aesthetic and periodontal differences between two methods of surgically uncovering labially impacted maxillary teeth (incisors and canines) were compared in a recent study. 49 The two methods were the apically repositioned flap described earlier and the closed eruption technique. With the latter approach, the tooth is uncovered, the attachment placed, and the tooth covered again. The posttreatment statistical comparisons between the two approaches indicated that with closed eruption there was relatively lesser amounts of attached gingiva, increased probing bone level, less gingival scarring, and less gingival relapse. From a clinical perspective, both techniques were acceptable, but the greatest advantage of apically repositioned flaps is providing the uncovered impacted tooth with adequate amounts of attached gingiva and, as importantly, the ability to apply orthodontic forces directly to the exposed tooth. With closed eruption, the force is applied indirectly to a chain or ligature wire extending from the gingival tissues at a site distant from the crown of the tooth to be moved. Direct force application provides more controlled tooth movement and decreases the chances of injury to the roots of the adjacent teeth.

If during any surgical procedure bleeding makes bonding of an attachment difficult, Vanarsdall and Corn recommended placing a surgical dressing to protect the tissues for 7 to 10 days. After removal of the dressing, a direct bonded attachment can then be placed in a dry field, and tooth movement can then be initiated. 4s

Kohavi et al 5° studied the periodontal health of labially impacted maxillary canines after their orthodontic alignment. They observed significant differences in the amount of the attached gingiva present on the labial aspect of the previously impacted canines when compared with the contralateral teeth. On average, the contralateral teeth had approximately 1 mm more attached gingiva than the treated teeth. The treated teeth still had more than 3 mm attached gingiva, which is considered physiologically adequate.

Therefore, the creation and preservation of a

functional band of attached gingiva should be an important objective in the management of labially impacted teeth. The attached gingiva could be made available through an apically repositioned flap, laterally repositioned pedicle graft, or when necessary, a free gingival graft.

Orthodontic Considerations

The prognosis for moving a palatally impacted tooth orthodontically depends on a variety of factors such as the position of the impacted tooth relative to neighboring teeth, its angulation, the distance the tooth has to be moved, and the possible presence of ankylosis, root resorption, or dilaceration. In general, horizontally impacted or ankylosed canines are the most difficult to manage and have the poorest prognosis. 51 As stated earlier, some of these teeth may need to be extracted (Fig 2).

Removable Versus Fixed Appliances

The use of fixed appliances to move the exposed tooth is advocated in most cases. This is because there are certain disadvantages to the use of removable appliances, including the need for patient cooperation, limited control of tooth movement, and the inability to ueat complex malocclusions.

Fournier et a137 and McDonald and Yap 42 suggested the use of Hawley-type appliances designed to transfer anchorage demands to the palatal vault and the alveolar ridge. These appliances might be useful in patients with multiple missing teeth when the use of fixed appliances is not recommended.

One-Arch Versus Two-Arch Treatment

Most malocclusions, including impacted canines, re- quire placing the orthodontic appliance on both maxillary and mandibular arches. This appliance enables the orthodontist to achieve the desired biome- chanical control needed to obtain optimal results.

The mandibular arch is seldom used as a source of anchorage to move the impacted maxillary canine. This is because of the difficulty encountered in control- ling the magnitude and direction of the applied forces from the mobile mandibular arch. Therefore, inter- arch mechanics should be considered only when the desired forces cannot be applied from within the maxillary arch.

Methods of Applying Traction

Various methods have been used for moving the canine into proper alignment. These include the use of light wire springs soldered to a heavy labial or palatal base wire and mousetrap loops. With the

96 Samir E. Bishara

in t roduct ion of new or thodont ic materials such as elastic threads, e las tometr ic chains, and nickel- t i tanium springs, the or thodont is t has a wider choice of materials and also greater control of the force magni tude and direction.

Regardless of the material used, the direct ion of the appl ied force should initially move the impacted tooth away from the roots of the ne ighbor ing teeth (Fig 4). In addit ion, the following is r ecommended : (1) the use of light forces to move the impacted tooth, no more than 2 oz (60 g) of force; (2) sufficient space should e i ther be available in the arch or should be created for the impacted tooth; (3) to maintain the space, e i ther continuously tie the teeth mesially and

distally to the canine or place a close coiled spring on the arch wire; (4) the arch wire should provide sufficient stiffness, such as .018 × .022, to resist deformat ion by the forces appl ied to it, as the canine is be ing ex t ruded (Fig 3). The added stiffrmss of the arch wire will min imize the undesirable "roller- coaster" effect caused by intrusion of the adjacent anchor teeth as a react ion to the deflect ion of a l ighter and hence more flexible arch wire. Therefore , the magni tude of the force appl ied by an elastometric chain to the impacted tooth and a round an arch wire should not deflect the arch wire.

C a n i n e V e r s u s P r e m o l a r E x t r a c t i o n

The prognosis for successfully exposing and guiding the canine to its p roper posit ion in the dental arch is often guarded. This is because the canine may be ankylosed, unde rgo resorption, or may become nonvi- tal. This should be made clear to the pat ient or parents. The prognosis for a successful ou tcome depends on the posit ion of the impacted canine, that is, whether horizontal or vertical, the relat ionship of the impacted tooth to the roots of the adjacent teeth, and

the skill of the clinician exposing the tooth as well as that o f the clinician moving it.

If the overall o r thodont ic t rea tment plan involves the removal of premolars, it is advisable to postpone their extractions unti l the canine is surgically exposed and or thodont ic forces are applied. This is done to insure the feasibility of moving the impacted tooth before extract ing a viable replacement . 7 Unfortu- nately, in severely crowded cases, the p remola r has to be extracted before any a t tempt is made to move the canine (Fig 4). Again, the pat ient or parents should be made aware of the possible complications.

Most clinicians agree that p e r m a n e n t canines are impor tan t for an attractive smile and are also essential for a functional occlusion. Therefore , extract ion of the canines should be avoided, if at all possible. If it is necessary to surgically remove the impacted canine, the or thodont is t has to decide on whether to move the

premolar into the canine posit ion or restore the space of the missing canine with a prosthesis or an implant.

If it is decided to close the canine space or thodont i - cally, the poster ior segment needs to be protracted and the case finished in a Class II molar relationship on the affected side, assuming that the mandibular arch has nonext rac t ion t rea tment (Fig 2). Such a t rea tment alternative is possible only if the first premolar is no t extracted unti l the prognosis of moving the impacted canine is definitively de termined . In these cases, the clinician needs to consider such factors as tooth size discrepancy, l ingual cusp interferences, and the difficulties encoun te red when employing unilat- eral mechanics. These factors must be carefully as- sessed, for each case, before the extract ion decision is made.

Retention Considerations

Becker et a152 evaluated the pos t t rea tment a l ignment of the impacted canines in patients who had com- pleted their o r thodont ic treatment. They observed an increased incidence of rotations or spacings on the " impac ted" side in 17.4% of the cases, whereas on the control side the inc idence was only 8.7%. The control side had ideal a l ignment twice as often as did tile impacted side.

In evaluating the pos t t rea tment changes approximately 4 years after t reatment , Woloshyn et al 5a compared the differences in the per iodonta l and pulpal status, root length, and tooth a l ignment between the side of the ectopically e rup t ing canine and the contralateral side. They observed that the probing attach- m e n t level was lower on the mesial and distal aspect of the previously impacted canines and, in addition, the roots of the adjacent lateral incisors and premolars were shorter. Pulpal obl i terat ion was observed in 21% of the previously impacted canines. Noticeable post- t rea tment changes such as intrusion, l ingual displacement, rotation, and discolorat ion was observed in 40% of the previously impacted teeth. O n the contralateral side, 91% had a normal appearance.

To minimize or prevent rotat ional relapse, a fi- bero tomy or a b o n d e d fixed retainer may need to be considered by the clinician after the comple t ion of the desired movements and often before the appliances are removed. Clark 39 suggested that, after the align- m e n t of palatally impacted canines, l ingual drift can be prevented by removing a "halfmoon-shaped wedge" of tissue f rom the l ingual of the canine.

The functional occlusion of previously impacted canines was exant ined both clinically and on an art iculator by Barwart et al. 54 They found that there were funct ional contacts on the working side dur ing lateral movements tor all of the orthodontically aligned impacted canines. Ha l f of the al igned teeth were involved in canine guidance and half in group func-


tion. Ba lanc ing side in te r fe rences were de t ec t ed in 22% of the cases. T h e i r results also ind ica ted tha t near ly ident ical func t ion was p r e s en t on the contralateral side, tha t is, for the spon taneous ly e r u p t e d ca- n ine .

Conclusions The m a n a g e m e n t of the severely i m p a c t e d c a n i n e is of ten a complex u n d e r t a k i n g a n d needs the com- b i n e d expert ise of a n u m b e r of clinicians. It is impor- t an t tha t these clinicians c o m m u n i c a t e with each o t h e r to provide the pa t i en t with an op t imal t r e a t m e n t p lan based o n scientific ra t ionale . An overview of the inc idence a n d sequelae as well as the surgical, peri- odonta l , a n d o r t h o d o n t i c cons idera t ions in the man- a g e m e n t of impac t ed canines was presen ted . T h e cl inician mus t be famil iar with the di f ferences in the surgical m a n a g e m e n t of the labially a n d palatally impac t ed canines a n d the best m e t h o d of select ing and p lac ing an a t t a c h m e n t o n the can ine for appropr i - ate o r t h o d o n t i c force appl icat ion. T h e advantages of one-a rch versus two-arch t r ea tmen t , the impl ica t ions of can ine extract ion, a n d the various factors tha t in f luence all of these decisions were discussed.

Acknowledgment This article was adap t ed f rom Bishara SE: I m p a c t e d maxi l lary canines: A review. Am J Orthod Dentof Orthop 101:159-171, 1992. All f igures r e p r i n t e d with permis- sion.

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