Positional variations of the maxillary cuspid are frequently encountered in dental practice. In such cases, because of its devious path to reach its position in the arch, it often gets impacted and becomes difficult to bring into occlusion. Both the orthodontist and surgeon should aim at early diagnose, schedule a plan, surgically expose the cuspid and use all acceptable orthodontic mechanics to bring it into occlusion. Sixty-six cases of uncrupted maxillary canines were treated by two different surgical exposures and methods (window and open-closed flap techniques) and were orthodontically moved into occlusion. The etiology, diagnosis and evaluation of the impaction, as well as the possible orthomechanics used to arrange the canine's position, need a clear understanding to plan a final treatment. The findings of this study showed that buccally-impacted canines are more common and to reach occlusion more quickly than palatally-impaeted canines. The axial inclination of the palatally impacted canines with the Frankfort horizontal plane has a direct effect upon the rapidity of treatment. The window surgical technique was found to be more convenient to the surgeon, orthodontist and patient.
 

The positional variations that the maxillary cuspid adopts are frequently encountered in orthodontic practice. While bringing the unerupted maxillary canine into the dental arch could be difficult, the therapist's diagnostic and treatment plan should be in the best interest of the patient.

Incidence of impaction of the maxillary canine rank second to that of third molar impaction.¹'² In any orthodontic practice the anticipation of problems related to maxillary canine impaction should be kept in consideration by early diagnosis. Early referral to the proper specialist is mandatory where certain interceptive measures could be instituted so as to diminish further complications such as incisal root resorption⁴'⁵ or cystic degeneration⁶.

In reviewing the etiological factors that lead to maxillary canine impaction, it is generally accepted that the devious path it follows during its eruption and the long period of its development play a great role in its impaction.²'⁷ Although crowding has been implicated,³ this factor has been neglected by several authors. Among other causes of canine impaction is heredity where several members of the same family are affected. Cystic degeneration around unerupted canines might cause their impaction.¹⁰

Bishara⁵ and Isiekwe et al¹⁴ listed the most common cause that participate in maxillary canine impaction such as tooth-size, arch length discrepancy, prolonged retention or early loss of deciduous canines, ankylosis of the developping canine, presence of alveolar clefts, root dilaceration of the develoipng canine, cystic degeneration of the enamel organ of the canine during its eruption, iatrogenic etiology and idiopathic maxillary canine impaction.

This study was to review the causes of maxillary canine impaction and to present 66 cases treated surgically by two different surgical approaches and orthodontically moved into their respective positions in the arch.
 

This study comprises 66 patients who sought dental treatment in King Fahd General Hospital Dental Department, Jeddah, Kingdom of Saudi Arabia. Not all the patients came for orthodontic treatment but have been referred for other dental problems. Their ages ranged from 13 to 19 years. All impacted maxillary canines were accidentally discovered through the routine clinical and radiographic investigations. Hence, such cases were referred to the Orthodontic Unit for further investigations and treatment.

Patients were clinically, radiographically and cephalometrically evaluated and findings were documented.
Clinical photographs were taken and study models were made on each patient.

The position of the impacted canine was determined by either palpation or location on lateral cephalometric as well as intraoral occlusal radiogprahs [Figs. 1,2]. Another method used, which some authors consider superior to cephalostats in locating the impacted canine, is the parallax technique. Two or more periapical radiographs were taken in the same area, shifting the tube horizontally between exposures. In this investigation, the cross-sectional occlusal radiographs as well as cephalostat technique yielded the best localization of impacted canine.

The lateral cephalometric radiographs were traced and the skeletal and dental cephalometric angles were measured to decide whether a case would require extraction mechanics or not. Moreover, the palatally impacted canines were traced and the angle formed by its long axis and Frankfort horizontal plane was measured in an attempt to find a relation between the axial inclination of the impacted canine and the period it would take to descend to occlusion [Figs. 3].

To complete orthodontic records, upper and lower alginate impressions were taken and poured in stone to serve as primary and study models for each use. Once the line of etreatment was reached, the patients were divided orthodontically into two groups. The first group was the extraction cases for which the maxillary first premolars were to be extracted and the second group were the non-extraction cases for which repositioning of the impacted canines was the only procedure performed after its surgical exposure.

Patients space establishment were referred to have restorations, scaling and oral hygiene instructions and extractions of premolars for the first group.

The patients were scheduled for bracketing and bonding to start the active orthodontic tooth movement. The brackets were standard stainless steel Edgewise brackets with 0.022" slot. The bands used were double tubed bands, the cervical round tube for extra-oral force application if required and the other rectangular tube for the arch wire.

Treatment for both groups was started by aligning and levelling the teeth by nickle titanium arch wires starting by round 0.014" followed by 0.016" then by 0.18". At times the teeth were so irregular that to commence treatment, 0.012" round nickle titanium wire was used. A round 0.018" stainless steel wire was then placed with first order bend to complete alignment.

In the first group (extraction cases), the patients were scheduled for surgical exposure of the canines by either procedure mentioned below. In the second group (non-extraction), spaces were created for the impacted canines. In those instances where there was retained deciduous canines and some spaces between teeth, an elastic chain over a rectangular 0.018"x0.022" stainless steel wire and/or push coil between lateral incisor and first premolar was used until a suitable space was created.

In cases of Class I subdivision malocclusion where there was a unilateral mesial shift of posterior teeth, Class II elastics (1/4" medium pull) were used on that side over the maxillary first premolar and mandibular first molar with a lower lingual arch for maximum anchorage. In the case with bilateral canine impaction, there was absolutely no space for ethem and the molars were in Class II malocclusion. A cervical face bow was used over the first molar until enough space was created bilaterally [Fig. 4a,b,c,]. Finally, the patients were ready for surgical interference.

Surgical Procedure

Surgical exposure of the impacted canine was done in either of two ways without any criteria of selection. The first method was the open-closed flap technique and the second was the Window technique.

First Group : In 33 cases, a flap was raised and the crown of the unerupted canine was exposed and surgical osteotomy was performed around the greatest circumference of the tooth taking in consideration not to expose the amelo-cemental junction. Bonding the orthodontic brackets was done during surgery after drying the exposed tooth surface from blood as best as possible.

The bracket was then bonded according to the accessibility obtained. Before bonding the bracket, a ligature wire was tied to it and twisted to form a long pig tail tie with an eyelet at its free end [Fig. 5]. This extension was to dangle down into the oral cavity through the flap that is replaced to cover the tooth with its bracket bonded to its crown [Fig. 6]. By emeans of this wire, the tooth was pulled to its destined position in the arch.

Second Group : This group comprised 33 patients. A graduated periodontal probe was used to perforate the anaesthetized oral mucosa to give a general idea as to the position of the unerupted canine for determing the line of incision. A semilunar incision was performed along the tip of the located cusp and extended for 0.5 cm on both sides of the tooth [Figs. 7a,b,c]. This was to allow viewing the position of the embedded crown. The created flap was raised by blunt dissection to expose the tooth around its great circumference and to expose as much of the clinical crown as possible just short of the amelo-cemental junction. Osseous surgery was done with Ochschenbein chisels so as to avoid any heat production from rotating instruments.

Osseous surgery was done in a way that did not leave any bulbous or bony projections that could hinder the path of canine eruption. It should be noted that, approximately, 2 mm of bone was left coronal to the amelo-cemental junction. This would allow a proper co-aptation of the dentogingival interface and secure a knife-like pattern of marginal gingiva. The edges of the flap have been bluntly undermined and then sutured all around the window with any soft tissue immediately surrounding the crown. Periodontal pack was applied to burrow itself under and around the window and left for one week [Figs. 7e,f,g]. At the time of bonding brackets after one week, it was ascertained that the crown surface was totally dry of any fluid.

To commence active orthodontic movement, a 0.018"x 0.022" rectangular stainless steel arch wire with a hellicle between the lateral incisor and the tooth distal to the created space, was ligated to the brackets. Teeth on either side of the canine space were ligated together by stainless steel ligature wire to secure anchorage and to prevent any loss of the created space. By means of the elastic threads that were tied to the hellicle in the arch wire and to the stainless steel extension in the first method or the brackets in the second method, gradual pulling forces were achieved until the canine reached a convenient position. Once the crown was fully exposed into the oral cavity, adjusting the position of the brackets was done by rebonding. The time required to have the impacted canine come actually into the oral cavity was recorded for each case taking the time of commencement of force applicatioon as a zero hour. Finally, the canine was positioned in the dental arch by using 0.014", 0.016", 0.018" and 0.018"x0.022" nickle titanium wires as deemed necessary.
 

Of the 66 cases treated in this study, none came seeking treatment for the impacted canine as all patients were not aware of the presence of any abnormality. Accidental discovery of the impaction was through routine screening in the Dental Department.

Thirty-six (54.5%) cases had the canines bucally situated while thirty (45.5%) were palatally impacted. Intraoral examination revealed that 65 cases were unilaterally impacted while bilateral impaction was present in only one case. Forty cases (60.6%) showed retained deciduous canines. As a prominent clinical finding, there was a bulge of the mucosa either labial or palatal that determined the position of the impaction. Although this was not a common finding, it was, more often than not, accurately determined radiographically. In those cases which could not be detected by palpation or by the presence of a bulge, lateral cephalometrics helped in locating the impacted canine [Fig. 1]. Intraoral occlusal films were merely confirmatory to the cephalometrics.

Out of the 33 cases treated by the open-closed flap, 10 cases showed loosening of the bonded brackets under the flap once, while one case showed loosening of the bracket twice. Re-entry surgeries were performed in those 11 cases to rebond the brackets. A significant difference in the treatment time was noticed in the bucally impacted canines compared to those presenting palatally in both surgical procedures. The bucally impacted canines reached occlusion at a faster rate than the palatally presenting as indicated in Tables 1, 2, 3 and 4 treated by either the Window or the Open-closed method.

Tables 1- and 2 show that 18 cases of bucally impacted maxillary canines reached occlusion during a period ranging from 3-6 months with a mean time distribution of 4.4 months +1.1. Fifteen palatally impacted cuspids reached occlusion during a period of 8-11 months with a mean time distribution of mean time of 9.1 months = 0.99. Both types of impactions were surgically exposed by the open-closed flap techniques.

Tables 3 and 4 indicate that 18 cases of bucally impacted cuspids erupted and reached occlusion during a period of 3-5 months with a distribution mean time of 3.9 months with a SD = +0.8 while 15 palatally impacted canines reached occlusion within a period of 8-10 months with a SD = +0.63. Both types of impactions were surgically exposed by the Window technique.

Table 5 illustrates the effect of angulation of the long axis of palatally impacted canines with Frankfort horizontal plane on the time taken by the impacted canine to arrive to occlusion. It was shown that the more acute the angle was, the faster the impacted canine reached occlusion and the more obtuse the angle was, the longer the period taken by the impacted canine to reach occlusion. Thus, as depicted from this table, for 12 cases with an angle ranging from 95 to 110, the time of treatment was 8 months. In 11 cases with angles ranging between 110 and 120, the teeth reached occlusion in nine months of treatment.

Seven cases with angles ranging from 120 to 135 reached occlusion after 10 months irrespective of the surgical technique used to expose them. It was also found that four of the cases treated by the Window technique showed active tooth eruption without any ortho-mechanics applied.

Impaction of the maxillary canine is a problem frequently encountered in orthodontic practice. The complexity of diagnosis and treatment plan using taxes the orthodntist's and surgeon's intelligence. Indeed, there are several modalities in treating impacted maxillary canines dictated by several parameters.

The results obtained from this study showed that labial maxillary canine impaction is more common than palatal impaction. This does not coincides with the findings of Fergusson³ who concluded that displacement from normal path of eruption most commonly occurs in a palatal direction. Also, Orton et al⁸ asserted that most ectopic canines are palatally impacted. On the other hand, Richardson and McKay⁴ questioned the validity of this concept as applied to many maxillary displaced canines. Although heredity has been implicated as a cause in maxillary canine impaction⁴ yet, in the present study, no familial background has been detected. Fearne et al⁹ correlated impaction of maxillary canine and cystic formation around the unerupted canine.

In the cases presented in this report, only one patient exhibited a cystic formation around an impacted canine. Anterior segment crowding has been considered as a cause in maxillary canine impaction³ yet some cases presented in this report showed the presence of enough spaces to accommodate normal eruption of the impacted tooth to its destined position. The available spaces resulted from the presence of peg-shaped laterals, congenitally missing laterals and retained deciduous canines. In this respect, crowding could not be a major factor in maxillary canine impaction. This is in agreement with the findings of Moss², Brin et al¹⁰ and Jacoby"

Surgical management of impacted canine for orthodontic mechanics has been a subject of controversy. The Window technique, performed by several authors,³'⁶ did not gain acceptance. Opponents to this technique advocated that removal of a tissue from an impacted canine might result in a "pathological" dento-gingival junction of the finally erupted tooth.²'¹²
Proponents of the open-closed technique concluded that the risk of attachment loss is reduced if a flap is raised and then replaced over the exposed crown of the impacted canine after attaching a suitable means with which traction of the impacted canine is applied.¹²¹³ In this study, the Window technique gave better clinical results when compared to the open-closed technique for several reasons. It was found indeed that such a procedure is more convenient to the surgeon, the orthodontist as well as to the patient himself. Bonding of the impacted exposed canine could be easily performed in "open air" after controlling the fluid contamination of the tooth surface if it is bonded during surgery. Another advantage of the Window technique is that it enables the orthodontist to observe all professional tooth movements during the treatment period, rather than moving the hidden canine under a flap which is indeed unpredictable. A second and, at times, a third surgical re-entry procedure should be performed to re-bond a loose bracket, which in itself is traumatic both to the patient and the gingival tissues. It should be added in this respect that the Window technique allowed the impacted canine to reach its destined position at a faster rate than impacted canines exposed by the open-closed technique. The suturing procedure adopted in the Window technique allowed the soft tissues to heal in a knife-like edge with the tooth surface resulting in proper co-aptation of the marginal gingiva of the finally erupted tooth. The extrusion of a peg-tail extention from under the raised flap in the open-closed technique method was reported by several patients in this study to be very irritating.

Finally, the angle existing between the long axis of the impacted canine and Frankfort horizontal plane could affect the period taken by the impacted maxillary canine to reach occlusion irrespective of the technique performed to expose it. In this report, it was found that the most favorable angle is from 95 to 100 degrees.

Based on the results of this study, the following conclusions are drawn :