Impacted Teeth: Orthodontic And Surgical Considerations By Vincent G. Kokich and David P. Mathews Most permanent teeth erupt into occlusion. In some individuals, however, the permanent teeth may fail to erupt and become impacted within the alveolus. The timing of orthodontic treatment, type of surgical procedure to uncover the impacted tooth, orthodontic mechanics necessary, and potential problems with treatment vary, depending on which tooth has become impacted. Surgical Techniques Four techniques can be employed to uncover impacted teeth. Subtle variations of each technique also are available for use in uncovering complex impactions. The type of impacted tooth and its location within the alveolus will dictate selecting the appropriate technique to uncover an impacted tooth. Gingivectomy A simple excision of gingiva can be accomplished with a sharp blade. This technique is indicated when there is a wide zone of attached gingiva, bone removal is not needed, and one-half to two-thirds of the crown can be exposed, leaving at least a 3 mm gingival collar. The most common area where this technique may be employed is over the labially impacted maxillary canine and/or central incisor. Apically Positioned Flap A split thickness flap is reflected from the area adjacent to the impacted tooth. Appropriate bone removal is accomplished, and the flap is sutured apically, exposing about two-thirds of the crown. This technique most often is employed on “simple” labially impacted teeth. Flap/Closed Eruption Technique A crestal incision is made and buccal and/or lingual flaps are reflected. Appropriate bone removal is accomplished, and a bracket or chain is attached to the impacted tooth. The flaps are returned to their original location for complete closure. The chain passes under the flap, exits at the mid-crestal incision area, and is attached to the archwire. This technique is best used with high labially impacted teeth and teeth that are impacted in the mid-alveolar area. With appropriate orthodontic mechanics, the tooth can be erupted, mimicking its natural eruptive path through the mid-crestal area. Maxillary Central Incisors Etiology The most commonly impacted tooth is the maxillary canine, followed by the maxillary central incisor. The usual cause of impaction of the maxillary central incisor is the presence of a supernumerary tooth or mesiodens. If the supernumerary tooth is discovered early and extracted, the central incisor may erupt spontaneously. If the root of the impacted incisor forms completely and the mesiodens has not been removed, however, then the central incisor may not erupt spontaneously. Surgery Impacted central incisors can be classified either as “simple” where the tip of the impacted tooth is near the adjacent cemento-enamel junctions or “complex” where the impacted tooth is positioned high in the vestibule. Central incisors usually are impacted labially. If the incisal edge of the maxillary central incisor is positioned coronal (incisal) to the mucogingival junction, an apically positioned flap, flap/closed eruption technique, or a gingivectomy procedure can be used to uncover the impacted central incisor crown. If the patient has insufficient attached gingiva, an apically positioned flap is chosen. If sufficient gingiva is present, a gingivectomy uncovering may be appropriate. If the incisal edge is positioned apical to the CEJ, a flap/closed eruption technique should be employed. With the latter technique, the tooth may be erupted through the crest of the ridge, and sufficient gingiva will be present over the labial of the central incisor. Simple The simple labially impacted tooth can be uncovered with either the apically positioned flap or the flap/closed eruption technique. Complex If the tooth is impacted high in the vestibule on the labial aspect, then the closed eruption technique is the treatment of choice. Postoperative Orthodontics During the postoperative orthodontic treatment phase, the key to success is the eruption of the maxillary central incisor into the center of the alveolar ridge. In order to accomplish this maneuver, the orthodontic force must originate from the center of the edentulous alveolar ridge. In order to erupt the tooth into the center of the ridge, a Ballista loop is helpful. This loop can be activated, and its force is directed from the center of the ridge in a vertical direction. The use of this type of loop will help pull the tooth into its normal path of eruption and not toward the labial. Maxillary Canine-Labial Impaction Etiology Labial impaction of the maxillary canine over the maxillary lateral incisor occurs occasionally. This type of impaction is due to one of two causes. Either the canine moves ectopically over the labial surface of the maxillary lateral incisor root and fails to erupt, or the maxillary dental midline may shift toward the canine, causing it to be impacted labially. Preoperative Orthodontics When the maxillary canine is labial to the maxillary lateral incisor, the root of the lateral incisor is oriented toward the palate. Surgery If the labially impacted tooth is located lateral to the edentulous area, i.e., an ectopic labial impaction, an apically positioned flap is the appropriate technique. It is rare that there is enough attached gingiva to allow use of the gingivectomy technique and still obtain an adequate collar of attached tissue. Use of the closed eruption technique would not be appropriate, because it would not allow the orthodontist to use the appropriate mechanics to move the tooth over the lateral incisor and into the edentulous area. Post operative Orthodontics After the labially impacted maxillary canine has been uncovered, the tooth must be moved into the dental arch. Maxillary Canine- Intra-Alveolar Impaction Etiology Intra-alveolar impaction of the maxillary canine is more common that labial impaction; however, neither is more common than palatal impaction of the maxillary canine. Preoperative Orthodontics In this situation, the orthodontist should wait until all permanent teeth have erupted before beginning treatment. The dental arch should be aligned, and space must be created for the maxillary canine. After the proper amount of space has been apportioned, a rectangular archwire is placed in the maxillary arch, and the patient is referred to the surgeon to uncover the impacted tooth. Surgery When the tip of the labially impacted tooth is coronal to the adjacent CEJs, and there is a wide zone of attached gingiva, it may be possible to use the gingivectomy technique. If the tip of the labially impacted canine is near the adjacent CEJs, or slightly apical, then the apically positioned flap or closed eruption technique can be used. In this location, it would be impossible to perform an excessional gingivectomy and leave adequate attached gingiva. Before any surgery is initiated, it is important to determine the location of the impacted tooth. In the case of a labial impaction, locating the tooth often can be accomplished by palpation. If the tooth is positioned in the middle of the alveolus or palatally, however, it will be necessary to determine its location by taking two radiographs at different angles. Use of the Buccal Object Rule is helpful in determining the location of these impacted teeth. Postoperative Orthodontics If the crown of the canine has been uncovered completely by means of excising the gingiva or apically positioning a flap, an orthodontic attachment may be bonded to the labial surface of the tooth. If the crown of the tooth is apical to the mucogingival junction, and a closed eruption procedure has been performed, a wire or chain will be extending through the gingiva at the crest of the alveolar ridge. The wire or chain will be connected to an attachment that has been bonded to the tooth. In this situation, the orthodontic objective is to erupt the tooth through the crest of the alveolar ridge. Maxillary Canine- Simple Palatal Impaction Etiology The cause of the palatal impaction of the canine is unknown. For some reason during tooth development, the direction of eruption of the canine becomes diverted toward the palate. Once this redirection of eruption occurs, although the tooth may erupt, it usually will be positioned in crossbite. Palatal impactions can be divided into two categories depending on the severity of the impaction. A simple palatal impaction is defined as a tooth that is diverted toward the palate, not deeply imbedded within the alveolus, and with the canine cusp tip located near the cemento-enamel junctions of the adjacent teeth. A complex palatal impaction describes a canine that usually is oriented horizontally relative to the occlusal plane, with the canine cusp tip located near the middle to apical portions of the adjacent teeth. The strategy for erupting these teeth and treating them orthodontically is different. Preoperative Orthodontics The timing of uncovering palatally impacted canines depends on the position of the tooth. If the impacted canine is not located high in the palate, but rather is positioned near the alveolar ridge (simple), it may be advantageous to uncover the tooth prior to beginning orthodontic appliance placement. If the canine is impacted near the roof of the palate (complex), early uncovering of the tooth may not be advisable. In this instance, the soft tissue probably will migrate over the crown, requiring a second surgical procedure. During the preoperative orthodontic phase of treatment, sufficient space must be created for the permanent canine. After sufficient interproximal space has been established, the patient is ready for surgical uncovering of the impacted canine. Surgery Two different techniques can be employed to uncover the palatally impacted tooth. Preorthodontic Uncovering Technique Simple palatal impactions can be treated by an early uncovering technique before placement of orthodontic appliances. When these teeth are uncovered early and left uncovered, they will erupt to a more favorable location that will facilitate orthodontic movement. Maxillary Canine – Complex Palatal Impaction In this type of patient, a different technique is used. A full-thickness palatal flap is reflected from the molar through the midline. Bone is removed from the crown of the impacted tooth, being very careful not to damage the roots of the central lateral incisor, especially around the apices of these teeth. The area is isolated to achieve a dry field for bracketing. In one to two weeks, the orthodontist can initiate tooth movement. Postoperative Orthodontics In the instance of a simple palatal impaction, the canine will have erupted partially into the plate after pre-orthodontic uncovering. If the canine is impacted near the roof of the mouth, it is difficult to move the tooth directly into the arch. In these situations, it is advantageous first to erupt the tooth into the oral cavity and then to attach it to the archwire. A transpalatal arch connected to the maxillary molars provides suitable anchorage for the eruption process. Mandibular Canine Etiology Impaction of the mandibular canine is uncommon. In some situations, the tooth bud of the mandibular canine will become rotated in the alveolus. As that happens, the canine root can develop in a horizontal direction. The canine then becomes impacted below the apices of the incisors. In these situations, it is very difficult to correct the impaction. In some of these patients, it is prudent to extract the canine to avoid damage to the roots of the incisors. Mandibular Second Premolar Etiology The second premolar impaction probably is due to idiopathic rotation of the tooth bud during development. If the tooth bud does not upright itself as the root develops, it eventually will become impacted horizontally. In this situation, surgical exposure of the tooth and orthodontic treatment will be necessary to properly position the tooth. Dr. Juri Kurol: Juri Kurol followed with a thorough review of the ectopic eruption of maxillary canines. “Early diagnosis of potential impactions is critical to finding the most ideal solution,” notes Professor Kurol. “Early extraction of the deciduous canines may result in spontaneous correction in about 80 percent of the cases,” he claims. Appropriate diagnostic procedures might include multiple radiographs as well as computerized tomography (CT). Answers to the following questions kept the audience engaged: How do we diagnose incisor root resorption? What is the prognosis for such resorption? Are large dental follicles dangerous? How can the damage be minimized?