Implants in adolescents

Abstract

Implants have gained tremendous popularity as a treatment modality for replacement of missing teeth in adults. There is extensive research present on the use of implants in adults, but there is a dearth of data available on the same in adolescents. The treatment planning and execution of implant placement in adolescents is still in its infancy. This review article is an attempt to bring together available literature.

INTRODUCTION

Long-term success of oral implants in partially edentulous cases has been the basis for other clinicians to broaden the use of implants to younger patients in whom teeth are missing due to agenesis and/or trauma. Anodontia either primary or acquired occasionally creates the opportunity for the use of dental implants.

Removable prosthesis has always been a choice in children with partially edentulous mouths. Not only are they unaccepted by younger patients, they may lead to increased caries rate, increased residual alveolar resorption and other periodontal complications. Since removable dentures and acid etch bridges are uncomfortable and cumbersome, young patients and their parents often insist to reduce the waiting time and insert implants as soon as possible.

Furthermore, the risk of ongoing alveolar bone resorption after tooth extraction encourages the clinician to go ahead with the oral implants immediately. In the absence of maxillary teeth, the alveolar ridges will not develop and the maxilla will remain underdeveloped both sagittally and vertically. In contrast, the mandiblular growth is not dependent on the presence of teeth. Therefore, in the presence of hypodontia or anodontia, the relationship between two jaws will tend to be disproportionate with class III development as growth continues throughout the normal growth period. Furthermore, physiological and psychological factors increase the pressure to start early treatment. Moreover pediatric implants have also proven to stimulate alveolar bone development.[1]

According to World Health Organization – adolescents are young people between the age of 10 years and 19 years.[2] However, the use of implants in adolescents differs significantly from adult implants. Special importance has to be given to the growth of the child, because a variety of changes occur in the dentition and jaws of the adolescent.

The benefits of implant use in adolescents are as important as the concerns for their premature use, but, they can be beneficial to the growing adult if meticulous diagnosis and treatment plan are followed.

IMPLANTS IN GROWING BONE

There has always been a controversy regarding placement of implants in children and adolescents with few researchers and clinicians advocating their use in this group of patients and a few others strictly contraindicating their usage.

One of the pioneering studies concerning growth patterns of the dental arches and replicating the implant insertion was carried out by Bjork[3] wherein he implanted 0.5 mm × 1.5 mm. tantalum pins in the jaws of growing children as stable landmarks for longitudinal cephalometric studies. Although most pins were stable, pins affected by growth were not. Orthodontic tooth movement also displaced the pins. Nearly all the pins placed in the resorptive areas such as the anterior mandibular ramus, were lost and had to be replaced. In addition, pins placed in areas of appositional bone growth gradually became embedded.[3]

Oesterle et al.,[4] and Brahim[5] compared dental implants to ankylosed primary teeth. An osseointegrated implant would behave much like an ankylosed primary tooth, with the same lack of alveolar growth and dental eruption. These authors proposed that implants placed in the posterior maxilla in children may become buried to the point that the apical portion may become exposed as the nasal and antral floor remodel.[4] Odman et al.,[6] recommended that implants should not be placed posterior to the canines during active growth.

In children with strong rotational pattern, posterior teeth undergo continued eruption, along with continued alveolar bone growth to maintain the occlusal plane, possibly causing implants to become deeply buried within the mandibular alveolar process.[7]

Implants located on opposite sides of the midpalatal suture of a pre-pubertal child would be carried apart a significant distance by transverse growth and this would create esthetic and functional problems. In contrast, if these implants were joined by a fixed prosthesis, transverse maxillary growth might be inhibited.[2] However, Cronin et al.,[8] suggested that successful implants in the mandible are favored by the lack of a complicating suture. Therefore, mandibular midline implants have a better prognosis in a young patient than those placed in other areas of the mandible or maxilla.

Indications for use of implants in adolescents

• Pediatric patients with ectodermal dysplasia (1988 National Institute of Health Consensus Development Conference on Dental Implants at Bethesda)[9]

• Implants combined with bone grafting in patients with cleft of the alveolus and palate[10]

• Children and adolescents having anodontia, partial anodontia, congenitally missing teeth, teeth lost as a result of trauma[5]

• Uncooperative children who find it difficult to adjust to removable appliances.

Contra-indications for the use of dental implants

• Pre-pubertal age group[8]

• Individuals with pubertal growth spurt[8]

• Inadequate mesiodistal space.[11]

Indicators of completion of growth

Chronological age is not sufficient to estimate growth cessation. Superimposing tracings of serial cephalometric radiographs taken at least 6 months apart (waiting until no growth change is seen over a period of 1 year) is probably the most reliable method, though it requires a lot of time and irradiation and may unnecessarily delay implant insertion.[12]

Skeletal growth status can be appraised fairly accurately by comparing a conventional radiograph of the hand and wrist against a standardized atlas of hand and the wrist bone development. Hand wrist radiograph indicators can be used to place a patient in the general area of the growth curve. Capping of the middle phalanges of the third finger (MP₃cap) usually occurs after maximum growth velocity is completed and indicates a deceleration in the pubertal growth spurt. Once pubertal growth is completed, consideration of implant placement can begin. However, some risks still exist. When epiphysis of the radius fuses and forms a bony union with the diaphysis, adult level of skeletal growth has been attained and no further increase in statural height can be expected. This is the best and safest time to place a solitary implant.[12]

Choosing a proper implant insertion age

In cases of severe anodontia or oligodontia in the mandible, the possibility or necessity exists to place implants even before the pubertal growth spurt, since in this patient group few growth changes occur in the anterior region after the age of 5-6 years, especially because of the absence of teeth. For the maxilla, it is suggested to wait until after the growth spurt.[13]

During the consensus meeting in 1995 it was decided that implant placement especially in partially edentulous cases preferably should be postponed until the end of the craniofacial/skeletal growth.[13]

Oesterle et al., observed that implants placed before the cessation of growth especially in the maxilla are unpredictable in their behavior and hence should be used with a great deal of caution. He suggested that implants placed during the pubertal period have a greater likelihood of success but still less than the post-pubertal or post-growth implant.[4]

Cronin et al., observed that if implants are placed during active growth, they may be displaced or malpositioned by continued growth and may require removal and replacement. Implants placed after age 15 for girls and age 18 for boys have the most predictable prognosis. Implants placed before these ages may not be permanent and may have to be re-implanted.[8]

Recommendations by area for placing an implant

Anterior maxilla

It is the most risky site for early implantation due to the unpredictability of growth in the area, especially in the presence of natural teeth. Premature implant placement can necessitate a repeated lengthening of the transgingival or transmucosal part of the implant, resulting in a poor implant - prosthesis ratio and adverse load magnification. It is advised to delay implant insertion until after skeletal growth is completed.[12]

Posterior maxilla

An early inserted implant can become submerged occlusally and exposed apically because of resorption of bone in the maxillary sinus/floor of the nose. It is recommended to delay an implant placement until after cessation of growth.[12]

Anterior mandible

This site seems to hold the greatest potential for early use of an implant supported prosthesis. However use of early implants in combination with teeth is not advisable due to the significant compensatory change in the dentition in this area during growth.[12]

Posterior mandible

It is recommended to delay implant placement until skeletal growth is completed as progressive infraocclusion of the implant and harm to adjacent teeth preclude the early placement of implant in this site.[12]

Recommendations for implant placement according to the length of the edentulous span

Sharma and Vargervik[14] stated that the use of implants for the growing child is not routinely recommended due to concerns regarding jaw growth. However not all children with missing teeth need to wait for growth to be completed prior to placement of the implant. This decision should be based not only on growth, but also on the number and location of the missing teeth.[14]

Though from all the studies it is evident that implant placement should be delayed till the completion of growth, there are certain cases where we can consider the placement of implants. Sharma and Vargervik[14] have classified these patients into three distinct groups that follow specific anatomic criteria:

• Group I: Children who are congenitally missing a single tooth and have adjacent permanent teeth

• Group II: Children who are missing more than a few teeth, but have permanent teeth present adjacent to edentulous sites

• Group III: Children who are completely edentulous in one arch or have one or two teeth in poor positions in the arch.

In Group I patients if the implant is placed before completion of growth, the implant will become submerged relative to adjacent teeth. This would lead to an esthetic complication and may result in poor implant to crown ratio if the restoration was remade to its appropriate length to camouflage the submergence. In Group II patients removable prostheses are used so as to orthodontically optimize teeth positions and consolidate edentulous spaces. However, in some patients implants may be placed before growth is completed, for psychological benefits of having a more functional, stable and esthetic solution. However, when the growth is completed, there will be a need for surgically repositioning of the implant segment with segmental osteotomy or distraction osteogenesis to a more favorable position. Another alternative would be a replacement of prosthesis with pink porcelain to improve esthetic symmetry of tooth proportion and gingival position. Group III patients usually have the diagnosis of ectodermal dysplasia. As the teeth are absent, the dentoalveolar growth and subsequent submergence of the implant is not a concern. Here, the downward and forward growth of the mandible and subsequent jaw size discrepancy is a problem. However, owing to poor oral hygiene, placement of implants in patients younger than the age of 7 is not indicated. In a study by Kearns, Perrott and Sharma, in patients with ectodermal dysplasia, implants have been successfully placed in the maxillary arch and in the mandible anterior to the mental foramen.[15] However, surgery may be necessary when growth is complete to correct the jaw size discrepancy. The prosthesis may have to be remade.[14]

CONCLUSION

In today's dental practice, the treatment plan for edentulous spaces always includes the option of implants. Not only do they assist in providing a better life-style, but also rehabilitate the patient to a more normal masticatory function. The dental surgeon shoulders the responsibility of responding to the growing demands of an “aware patient.”

Although the use of implants in adolescents is uncommon because the dental surgeon is concerned about “growth spurts” related to the maxilla and mandible. If he follows the indications and timing of placement of implants correctly, the predictability of their success will not be a problem for him. If the protocol for implant placements in adolescents is followed, their success rate can be guaranteed and they can be used more routinely.