Removable prosthesis which includes removable partial dentures, complete dentures and overdentures are often the treatment of choice to replace missing teeth and/or restore vertical dimension of occlusion prior to definitive treatment. The advantages of overdentures in cases of hypodontia are well documented. Removable pros-theses are easily modified or remade during the growth period offering an easy, affordable, and reversible method of dental rehabilitation. Fixed Prosthodontic treatment is seldom used even as an interim prosthesis in the treatment of hypodontia. Fixed partial dentures with rigid connectors should be avoided in young, actively growing patients as it may interfere with jaw growth.
The successful use of implants in adults has arosed the interest of the clinicians to try them in younger patients. There is no doubt that the children who have congenital anomalies can benefit remarkably from an implant supported oral rehabilitation carried out in childhood.1 However, dental and skeletal growth is a major compounding variable related to the use of dental implants in adolescent patients.2 Clinicians should have an understanding of the potential risks involved in placing implants in jaws that are still growing and developing and consider the effect that implants have on craniofacial growth3.
For a stable implant position, it is generally recommended to wait for the completion of dental and skeletal growth. In a growing child, the growth and development of maxilla and mandible are different as are those in the specific areas of each arch4-7. Transversal skeletal or alveolar dental changes are less dramatic in mandible than maxilla8. However if implants are to be placed in children or adolescents, the two primary concerns are the effect of growth on the long term relative position of the implant and the effect of implant supported prosthesis on future dental and skeletal growth2.
Normally the early growth in maxilla is due to growth of the cranial base and the later growth is extremely variable and can be vertical, transverse and antero posterior. Transverse growth occurs at the midpalatal suture and implant prosthesis crossing the suture will restrict growth. In the mandible, the growth in the posterior region occurs predominantly in late childhood with large amounts of anteroposterior, transverse and vertical growth apart from rotational growth [Downward and forward, mediated by oppositional condylar growth]. Where as in anterior mandible, there is minimal alveolar growth when teeth are missing due to early stabilization of the mandibular symphysis. Major transverse growth is complete in early childhood. It is the most suitable site for implant placement. Placing implants in this region also will diminish the residual alveolar resorption.
In the absence of maxillary teeth, the alveolar ridges will not develop, and the maxilla will be underdeveloped both sagittally and vertically. In contrast, Mandibular growth is not dependent on the presence of teeth. Therefore, in the presence of hypodontia or anodontia, the relationship between the two jaws will tend to be disproportionate with class III development as growth continues throughout the normal growth period9.
DISCUSSION
Anodontia is a genetic disorder defined as the absence of all teeth and is extremely rarely encountered in a pure form without being part of a syndrome. Rare but more common than anodontia are hypodontia and oligodontia. Hypodontia is genetic in origin and usually involves the absence of 1 to 6 teeth. Oligodontia is genetic as well and is the term most commonly used to describe conditions in which more than six teeth are missing. These conditions may involve the primary or permanent sets of teeth, but most cases involve the permanent teeth.
One of the commonest causes of congenitally missing teeth in children reported in the literature is due to ectodermal dysplacia (ED). Young children with ED and anodontia in the mandible, present special challenges while placing implants.10 Implant survival rates vary between 88.5% and 97.6% in patients with ED and between 90% and 100% in patients with tooth agenesis. Implants placed in adolescent ED patients do not have a significant effect on craniofacial growth, while implants placed in ED patients younger than 18 years have a higher risk of failure11. The main risk factors could be the small jaw size, the pre-operative condition, lack of patient monitoring following surgery and orofacial motor dysfunction, rather than the ED itself.10,11 Some of the authors have argued that endoosseous implants can be successfully placed and can provide support for prosthetic restoration in patients with ectodermal dysplasia12.Studies have shown that these patients benefit remarkably from an implant supported oral rehabilitation13 particularly because children do not use removable partial dentures. The loaded implants help to ensure maintenance of ridge height, prevent supra eruption, and maintain stable occlusion.
Although the development of techniques for osseointegrated implants offer new possibilities for the prosthdontic rehabilitation of such children, it was concluded that implant surgery in small children must not be considered routine treatment14. It is recommended to wait for the completion of dental and skeletal growth except for severe cases of ectodermal dysplacia15. It is accepted by most of the authors that
the safest time to place implant in such children seems to be during the decline of adolescent growth curve determined by cephalometric radiographs, serial measure of stature or hand-wrist radiograph8.
PROBLEMS AND PRECAUTIONS
Implants in the maxilla can behave like ankylosed tooth16, cannot participate in growth resulting in growth disturbances, unpredictable implant dislocations in vertical and antero posterior direction and even implant losses due to resorptive aspects of growth at the nasal floor and anterior surface of maxilla. It is concluded that insertion of implant in growing maxilla should be avoided until early adulthood8.
In the posterior mandible, implants may become submerged resulting in both functional and esthetic disadvantages later like infra occlusion and multidimensional dislocation when compared with the developing teeth. As a result there are no reported implant insertions in the posterior mandible8.
Overall, implants in any region can interfere with the position and eruption of adjacent tooth germs.
There may be morphological changes due to trauma to tooth germs and disorders of eruption.
Osseointegration may be lost as the growth takes place.
In order to avoid these problems, some clinicians have tried placing implants buccally with success. Implants placed after 15 years in girls and 18 years in boys or when two annual cephalograms show no change in the position of the adjacent teeth and alveolus are said to have the most predictable prognosis6,9.
If a decision is made of implant placement, it is advisable to restore larger edentulous areas with implants than to place a single implant supported crown1,16,17. Considering the anatomical and morphological features in pediatric patients mini and micro implants are being introduced8. A combination of well executed Implant-supported/tooth-supported, overdenture (hybrid) prosthesis would be an excellent choice in rehabilitation of congenital subtotal anodontia later in life in contemporary dental practice18.
However, the decision for implant placement is based not only on growth, but also the number and location of the missing teeth. In patients who present with com-plete anodontia, implants can be planned in the maxilla and anterior mandible as early as age 7.
These may be classified under provisional implants.
It has to be kept in mind that surgery [segmental osteotomy or distraction osteogenesis] may be necessary once growth is com-plete to reposition of
the implant segment to a more favorable position there by to correct the jaw size discrepancy. Implants may have to be replaced7 or the implant prosthesis may have to be modified or remade over time by utilizing pinc porcelain or acrylic resins for fixed or removable implant supported prosthesis9.
Some studies have shown excellent long term results achieved after appropriate case selection, careful handling of the soft and hard tissues and good occlusal harmony. But usually a common problem faced in case of missing teeth is lack of sufficient bone for implant placement and this may be due to local to general decrease of growth stimuli of the jaw due to absence of large numbers of teeth.
CONCLUSION
Ideally the implants are placed once the skeletal growth is completed, but in cases of partial or complete anodontia the use of implants is becoming popular.
Placing implants in a child patient should be a team effort consisting of surgeon, pedodontist, prosthodontist, orthodontist and periodontist. There is no doubt that implants would greatly assist in prosthesis support. The clinician should understand the disadvantages of early placement and weigh those factors against esthetic and functional advantages afforded by implants.
Patients with implant assisted restorations should be evaluated frequently to ensure the health of the implant and its surrounding tissue as well as to assess the effect of the prosthesis on the overall growth and development of the jaws. An extremely vigilant recare programme is necessary.
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