Orthodontic Considerations for the Young Adolescent Requiring Single-Tooth Implants

Dentistry Today February 1, 20038 Mins read2.5k Views

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Dentists are faced with a challenging clinical situation when a young adolescent patient presents with one or several congenitally missing permanent teeth. The treatment plan that is developed for a young patient must be relevant for many years in the future. Today’s patients have different restorative needs than what was seen in the past because they have either a low caries rate or are caries-free. For this reason, there is very rarely a need for full-coverage, fixed prosthodontic restorations. Instead, the replacement of a missing tooth or teeth is with implants, followed by fabrication of a crown. Despite the increased expense, parents are choosing the implant option versus other restorative options that are available. Needless to say, successful treatment requires cooperation between the orthodontist, the implant surgeon, and the restorative dentist.

The primary considerations in these cases are knowing the best time to institute orthodontic treatment, how the space needed for the restoration should be maintained after the active phase of orthodontics has been completed, and when implant treatment is indicated considering the cessation of growth in the orofacial region. In other words, timing is the key.

Maxillary lateral incisors are the most common congenitally missing teeth, followed by third molars, second bicuspids, and mandibular incisors.¹ The missing maxillary lateral incisor is, without question, the most commonly encountered situation requiring tooth replacement. In the past, treatment options for such missing teeth were limited, and ranged from removable partial dentures to fixed partial dentures of various design, and orthodontic movement of adjacent teeth into the position of the congenitally missing dental unit.1 However, the closure of such spaces by orthodontic means posed aesthetic and functional problems. The maxillary cuspids are anatomically much larger than maxillary lateral incisors. The mesial movement of a cuspid would then require the removal of proximal enamel, as well as extensive reshaping of the facial, lingual, and incisal surfaces. In addition, the color of the cuspid is much darker than the lateral incisor (more orange and brown). Thus, the aesthetic result after “lateralization” leaves evidence of the congenital defect.² Furthermore, the anterior movement of the cuspid results in changes in the functional occlusion with the loss of canine guidance. This occlusal change has the potential for long-term adverse effects on the temporomandibular joints (TMJs). In sum, this approach is generally unacceptable.

Today, combining orthodontic and implant therapy can provide patients with an excellent aesthetic and functional result. Although more costly and time consuming, the results that can be obtained are also biologically conservative.2 As noted before, the timing of implant placement is crucial for success. It has been documented that if the implant is placed too early relative to the patient’s tooth eruption pattern, the implant will behave as an ankylosed tooth.3 The aesthetic result will be compromised because the gingival margin of the implant will not be in alignment with those of the adjacent teeth. Therefore, it is important to ask about special treatment considerations that are needed, and when the patient is ready for implant placement.

ORTHODONTIC MOVEMENT OF THE CUSPID TO ENHANCE RIDGE AUGMENTATION


Figure 1. The maxillary right cuspid in the position of the maxillary right lateral incisor, anterior view.	Figure 2. Patient in Figure 1, lateral view.

When a patient with early mixed dentition presents with a congenitally missing lateral incisor, careful consideration must be given to when the primary cuspid should be extracted without compromising the thickness of the alveolar ridge. If the permanent cuspid erupts immediately distal to the permanent maxillary central incisor (Figures 1 and 2), the primary lateral incisor and/or primary cuspid should be extracted just before moving the permanent cuspid distally.³ The distal movement of the cuspid, known as orthodontic implant site development, will help develop the alveolar ridge in the area of the lateral incisor. The distalization of the cuspid results in the development of a dense alveolar ridge along the fiber tracks of the periodontal membrane.4 With this movement there is significantly less alveolar bone loss than if the tooth is extracted.5 By appropriate orthodontic movement of the cuspid in this fashion, the need for a surgical ridge augmentation is generally eliminated. The resultant bone height and thickness should allow for ideal implant placement.

SPACE MAINTENANCE DURING ORTHODONTIC TREATMENT


Figure 3. Replacement of congenitally missing lateral incisors with prosthetic teeth during orthodontic treatment.	Figure 4. Patient in Figure 3, occlusal view.

Figure 5. The mandibular left second primary molar acting as a space maintainer until implant placement for the congenitally missing permanent second bicuspid.	Figure 6. Panoramic radiograph of the patient in Figure 5.

It can be difficult for children and adolescents to undergo orthodontic treatment, and even more so when the patient is missing a maxillary anterior tooth. Once the appropriate space for the replacement of the missing tooth is accomplished there is the need to retain that space. Routinely, an impression is made of the maxilla and mandible, and the models are sent to the orthodontic laboratory along with an appropriate tooth shade. The laboratory then fabricates a prosthetic tooth to fit the space, and an orthodontic bracket is added on the labial surface. The prosthetic tooth is attached to the maxillary archwire, and the necessary adjustments are made in order to avoid impinging on the ridge or proximal gingival tissues. By performing this minor addition, the aesthetics improves markedly, and generally the patient cooperates with treatment (Figures 3 and 4).

If the patient is missing a posterior tooth such as a second bicuspid, it is customary to retain the primary molar for as long as it is functioning. On occasion it may be advisable to reduce the mesio-distal dimension of the primary molar so this tooth will be as close as possible to the size of the missing second bicuspid. At times the primary second molars will remain in place for many years while at the same time preserving the alveolar bone for eventual implant placement (Figures 5 and 6).

AFTER ACTIVE ORTHODONTIC TREATMENT
Usually, orthodontic therapy will be completed before facial growth is completed. The question then is how to maintain the space until the patient is ready for implant placement. If there is a short period between the completion of active orthodontic treatment and implant placement, a removable Hawley retainer with a prosthetic tooth attached to it will be adequate. This appliance can be used after implant placement and during the healing phase.3 The removable appliance must rest passively on the ridge to avoid impinging and thus irritating the soft tissue.


Figure 7. A resin-bonded bridge replacing the maxillary right lateral incisor. Orthodontic treatment is completed. The restoration will remain until facial growth is completed and an implant is placed.	Figure 8. Panoramic radiograph of the patient in Figure 7. The ridge in the edentulous area (maxillary right lateral incisor) is well developed after orthodontic therapy.

If there is a long period of time between the removal of the orthodontic appliances and the placement of the implant, a more permanent retainer is required. Individuals in this age group cannot be depended upon to wear a removable appliance for an extended period of time. In addition, the removable appliance will deteriorate over time and will not be as aesthetically pleasing as a fixed bonded retainer. Therefore, in most cases, the patient is referred back to the restorative dentist for the fabrication of a resin-bonded bridge to hold the tooth position and maintain the space until facial growth is completed and the time for implant placement is reached (Figures 7 and 8).

Regarding the replacement of missing posterior teeth, as noted, the remaining primary molar can act as a permanent retainer. If the tooth is scheduled for removal, it is best to delay the extraction for as long as possible to enhance preservation of the ridge. It has been documented that extraction of the primary tooth three years prior to implant placement leads to a reduction in ridge thickness of approximately 25%.³ Most of this loss occurs on the buccal surface of the ridge, and if the resorption is extensive, the implant placement may be compromised.⁴

There is a situation when the primary second molars are extracted earlier than what has been discussed. This is when the tooth appears to be ankylosed, and the patient’s facial height is still growing. If the ankylosed teeth are not extracted, it will affect the height of the alveolar ridge. In these cases, the alveolar ridge does not increase in height as normally occurs with the erupting dentition. This may create a vertical defect on the proximal surface with the adjacent first premolar and/or first molar that could complicate implant placement at a later date.⁴ Special care should be taken when extracting ankylosed teeth. The integrity of the buccal plate must not be compromised to preserve as much of the residual ridge as possible.

If the primary molar is no longer present, a fixed posterior retainer can be fabricated by using the Unitek Bonded Lingual Retainer kit in conjunction with Transbond light-cured adhesive. The wire used is a spiral wire, 0.032 inch in diameter, which will not unravel when cut. The retainer is formed on a study model, considering the position of the adjacent teeth. The appliance is then bonded to the adjacent teeth. There must be adequate adhesive around the wire in order to assure maximum strength. The appliance should not interfere with the occlusion and should not impinge on the surrounding soft tissue.

DETERMINING THE COMPLETION OF FACIAL GROWTH

Figure 9. Patient in Figures 5 and 6. Superimposed cephalometric tracings demonstrating no change in vertical growth from 7/9/99 (black) to 6/6/00 (red). An implant can now be sucessfully placed.

Since the most ideal time to place the implant is when growth of the maxilla and mandible is completed, it is important to determine when this has occurred. In the past, the hand wrist film was used to make this determination. Nevertheless, this measure varies from patient to patient.³ Most boys will not complete facial growth until their late teens, but for girls facial growth is generally complete by the age of 15. An alternate measure is required. Consequently, the most accurate method of evaluating the completion of an individual’s facial growth is by superimposing consecutive cephalogramic radiographs taken at 6-month intervals. The most recent cephalogram is superimposed over the prior one. The cephalograms are superimposed using Sella—Nasion as the reference, since this is stable early in development. The anterior cranial base is fused at approximately 4 to 5 years of age, making it an excellent reference plane. If facial growth is complete, when the sequential radiographs are superimposed, the vertical relationship (Nasion-Menton) will not have changed. If there is a change in the vertical facial height another cephalogram should be exposed in 6 months and a similar analysis performed.
With the completion of facial growth, the implant can be safely placed without concern for any additional eruption of the adjacent teeth. This will allow an excellent aesthetic result (Figure 9).

CONCLUSION
The development of osseointegrated implants has given the dental profession the opportunity to provide young patients with the most conservative aesthetic result when replacing congenitally missing teeth. This treatment requires the collaboration of the restorative dentist, implant surgeon, and orthodontist. The ultimate determining factor for success in these cases relies upon an understanding of facial growth.

References

Rupp R, Dillehay J, Squire C. Orthodontics, prosthodontics, and periodontics: a multidisciplinary approach. Gen Dent. 1997;45:286-289.
Balshi TJ. Osseointegration and orthodontics: modern treatment for congenitally missing teeth. Int J Periodontics Restorative Dent.1993;13:494-505.
Spear F, Mathews D, Kokich,V. Interdisciplinary management of single-tooth implants. Seminars in Orthodontics. 1997;3:45-72.
Fowler PV. Long-term treatment planning for single tooth implants: an orthodontic perspective. Ann R Australas Coll Dent Surg. 2000;15:120-121.
Richardson G, Russell KA. Congenitally missing maxillary lateral incisors and orthodontic treatment considerations for the single-tooth implant. J Can Dent Asso. 2001;67:25-28.

Dr. Baurmash is a diplomate of the American Board of Orthodontics, and a clinical assistant in the Department of Orthodontics at the University of Pennsylvania School of Dental Medicine. She can be reached at (980) 781-7037 or orthomab@aol.com.

Dr. Gostovich received her dental degree from the University of Medicine & Dentistry of New Jersey in 2001. She is currently a second year orthodontic resident at the University of Pennsylvania. She will complete her postgraduate orthodontic training in 2003.

Ms. Johnston is currently a third year dental student at the University of Pennsylvania.