4.  Dental implants for Growing Patients
Considerable research supports the efficiency of rehabilitation of a completely or partially edentulous mandible and maxilla using prosthesis supported by implants [282,283]. However, almost all scientific investigations regarding implants have been performed in adults, when the dynamics of growth and development (statural, skeletal, facial, dentoalveolar) are not an issue. Currently, it is seen that severe hypodontia or even anodontia in children or adolescents, most often associated with congenital syndromes such as ectodermal dysplasia (ED), are treated with implant-supported prostheses for optimum functional and psychosocial development of the pediatric patient. The insertion of dental implants in children or adolescents before the completion of craniofacial growth, however, could cause problems since the maxilla and the mandible are dynamically changing during childhood [284–287]. Therefore, several relevant aspects should be considered before inserting an implant in growing patients.

4.1.  Special Considerations for Implant Therapy in Children
Implant timing and implant positioning are the important issues to be assessed carefully before the implant therapy in young patients with dynamic growth. The finding of the ideal time for the implant treatment in children has been reported as quite difficult since many different aspects have to be considered while finding the best individual treatment strategy [288]. Additionally, lack of relevant long term clinical implant studies in children and its effects on the development of the maxillofacial structures also could create problems on implant timing in young patients. From the orthodontic view, it is known that the safest time to place implants is the time during the lower portion of the declining adolescent growth curve at or near adulthood [289]. A majority of studies have advocated delaying implant placement until skeletal and dental growth has been completed [290–292] especially when natural teeth are present [292,293]. However, in some cases, especially in children with completely edentulous mandible and maxilla, insertion of an endosseous implant could be necessary before the craniofacial growth is completed. Furthermore, in assessing young patients with implants caution must be exercised in generalizing the results since there are difficulties in prediction of the growth process which varies from individual to individual.
The potential problems associated with placing endosseous implants in growing patients have been addressed by many authors [292,294–299]. The fact that the implants does not follow the normal growth of the maxilla or mandible in the three planes of space and may interfere with the normal growth of the alveolar process are important issues in implant dentistry of growing patients [296,300,301]; and additionally, the end result of an osseointegrated implant placed during growth could be difficult to predict.
There is no capacity for compensatory eruption or physiological movement of the implant fixture in individuals where growth is incomplete since osseointegrated implants lack the compensatory mechanisms of a periodontal ligament and are in direct apposition to bone [298,299]. An osseointegrated implant behaves like an ankylosed tooth and become submerged because of growth associated with the continued eruption of neighboring natural teeth [298]. In the nearly anadontic child, however, these problems can be neglected. Placement of implants in the growing maxilla and/or mandible with only a few missing permanent teeth has been studied, and it has been demonstrated both clinically [292,302] and experimentally [298,299] that osseointegrated endosseous implants adjacent to the natural teeth do not move in vertical, transverse, or sagittal direction and become submerged because of lack of associated growth of the alveolar growth and continued eruption of neighboring natural teeth [297–299,303]. The authors [298,299] stated, however, that it is difficult to directly extrapolate the results from animals to growing children. Additionally, it was also emphasized that the fact that implants placed adjacent to natural teeth in a growing child will become submerged should not necessarily be considered a contraindication to the use of endosseous implants [288]. Kawanami et al. [304] states that infraposition occurs even in patients more than 20 years old. The studies have also reported that the changes in adults occur over decades and also result in teeth misalignment. Additionally, it is known that the majority of skeletal growth in females is completed by 15 years, but males grow up to 25 years [292,296].
The bony apposition and resorption patterns could alter the position of implants placed in maxilla and mandible. Maxillary growth occurs as a result of both passive displacement and enlargement. Passive displacement occurs as the maxilla is carried downward and forward by growth and flexion of the cranial base nada complicated system of sutures in the midface [305]. Because of the resorptive aspects of maxillary growth at the nasal floor and the anterior surface of the maxilla, unpredictable dislocations in vertical and anteroposteror direction can occur and even implant losses may be expected. Cronin et al. [302] have stated delaying implant placement in the growing maxilla until early adulthood. It is likely that in the absence of teeth, the alveolar bone apposition in a vertical dimension is inhibited and that implant position is affected only by sutural growth in the maxilla. In mandibula, it was noted [306] that mandibular growth pattern is generally characterized by upward and forward curving growth in the condyles, with anteroposterior growth occuring mainly at the posterior mandible [286]. It was stated that the rotational growth resulting particularly in vertical alterations [286,287]. It was also demonstrated that the position of implants placed in the posterior mandible in growing pigs could be altered as a result of bony apposition and resorption patterns, leading to a multidimensional dislocation of the implants [299]. To our knowledge, there exist in the literature no reports on implant insertions in the posterior mandible in pediatric patients. Additionally, one other potential problem of implants in growing tissues is the fact that the implants could jeopardize the germs of the adjacent permanent teeth or alter the path of eruption [299,303].
The fixed implant constructions crossing the midpalatal suture will result in a transversal growth restriction of the maxilla since the transversal growth of the maxilla occurs mostly at the midpalatal suture. In the mandible, the majority of transversal growth at the mandibular symphyseal suture occurs quite early in childhood, usually ceases in the first six months, therefore, the transversal skeletal growth or alveola-dental changes are less dramatic than the maxilla [306]. Kearns et al. [307] has reported that no interference with transverse mandibular growth is to be expected when implants are installed in the anterior mandible. Because maxillary transverse growth at the midpalatal suture has been suggested to be adversely affected by rigid prosthetic devices [297], all maxillary prosthetic bar attachments that cross the maxillary midline can be separated in the midline to maintain uninterrupted growth at the midpalatal suture [292,307].
Implants placed in edentulous jaws of growing patients provided the most predictable outcomes in the edentulous anterior mandible, fixtures moved in harmony with sagittal mandibular growth and during the follow-up period no alteration in abutment or prosthesis was required. Several case reports of implant insertions in the anterior mandible of children have been published [7,308–310]. However, the use of implants to replace single teeth in the anterior mandible is not advisable due to the compensatory anteroposterior and the vertical growth in this area. Consequently, implants would remain in an infraocclusal position and would probably be displaced in the anteroposterior direction [306].
A multidisciplinary approach to implant treatment is recommended for children [311,312]. A pediatric dentist, an orthodontist, a prosthodontist, and an oral and maxillofacial surgeon are necessary for the the best individual implant treatment strategy. All specialities have an impact on the process by contributing their specific views and knowledge on rehabilitation [290]. The status of skelatal growth, the individual status of the existing dentition (the degree of hypodontia, the functional status of mastication and phonetics) should be evaluated, esthetic aspects and dental compliance of both the pediatric patient and parent to implant treatment and implant hygiene should be taken into account in determining the optimal individual time period of implant insertion [307].
A risk/benefit assessment must be made for each individual to optimize dental rehabilitation [313]. It should be remembered also that there are significant shortcomings of removable prostheses. Poor retention and instability of prostheses [314], dental hygiene problems, speech difficulties, and dietary limitations, moreover, progressive resorption of basal bone when the edentulous ridge is loaded by prosthesis at an early age should be weighed against the need to change abutments and the possibility that implants will need to be removed at a later date. Furthermore, in young patients’ social development, emotional/psychological well-being [315], extension of related psychosocial stress is important issues. Congenitally missing teeth can create dental and facial disfigurement, which can lead to social withdrawal, especially in the adolescent years [316]. Bergendal et al. [308] have stated that functional, esthetic, and psychological rehabilitation should start early in the patient’s life. Högberg et al. [317] reported that children with disabilities realize at the age of 9 years their specific conditions when they compare themselves with other children. Nussbaum et al. [318] has focused the cases probably resulting in a state of depression. Therefore, the dental team also has to support the child in coping with issues of attractiveness during the formative years of childhood [317] and could apply dental implants while they are still growing [316]; benefits of placing implants in young patients should not be discouraged. Guckes [319] has stated that if implant –supported prostheses were shown to have positive effects on craniofacial growth, social development, self image, and food choice, their use in the anterior mandible might be routinely recommended in younger patients. Dhanrajani and Jiffry [314] have reported that the patient’s skeletal and dental maturity, not chronological age should be the determining factor for the time of implant placement, and the parents should be informed about the possible complications.

4.2.  Clinical Studies on Use of Endosseous Implants
The literature contains several anecdotal reports of the use of dental implants in growing patients, many with anodontia or oligodontia, often associated with ED, or from trauma [295,296,308,320–324]. The lack of relevant long-term clinical studies has not prevented clinicians from using implant-assisted prostheses in children; dental implants in children were described in dental literature as a successfull adjunt to oral rehabilitation [308,314,320,325,326]; and implant success rates were reported as 87% in preadolescents (ages 7–11), 90% in adolescents (ages 12–17), and 97% in adults (older than 17) [318]. The studies have demonstrated that implants may have high success rates in the edentulous child [307], and implants placed in girls after 15 and in boys after 18 years of age have a better prognosis than in younger children [297,302]. Stable implant conditions were reported after an observation period of 4 to 5.5 years in children with ED [308,320,325,327].
Alcan et al. [328] reported on 6-year follow-up of a child with ectodermal dysplasia who was treated with implants surgery very early. In edentulous patients, the 10-year survival rates of such implants were 82% and 94% for the maxilla and mandible, respectively [307]. The mandibular endosseous implant was placed in a 4-year-old patient with hypohidrotic ectodermal dysplasia and oligodontia. It was reported that (i) the congenital anomaly does not appear to retard healing and the osseointegration remains after six years and three months of loading, (ii) mandibular and maxillary skeletal growth and development was normal, (iii), however, because of lack of alveolar growth, in time, patient’s vertical growth pattern changed to low angle. This could be corrected by changing the vertical heights of the abutment and prosthesis. As a result, in ectodermal dysplasias cases with anadontia, early implant placement and fixed prosthesis could be a good multidisciplinary treatment option for poor cooperative child. Balshi et al. [329] claimed the advantages of implants (Ti Brånemark implants, and zygomatic implants as well) due to biomechanical and esthetic uniqueness associated with implant-related prosthodontic orofacial rehabilitation for ED patients. A similar clinical opinion can be found from Becktor et al. [330], who used the endosseous implants in the oral rehabilitation of adolescent patients with HED and reported it should be considered a viable treatment option. The clinical report of a 18-year-old patient with hypohidrotic ED treated with a maxillary implant overdenture and a mandibular hybrid prosthesis supported by osseointegrated implants have presented significant improvements in oral function and psychosocial activities at the one-year follow-up [331]. Patients with oligodontia may benefit from the use of dental implants in the mandibualr anterior region, with restoration of function and improvement in psychosocial development, without waiting for the completion of growth to initiate treatment [7]. In older ED patients, for whom growth has stabilized, osseointegrated implants can be used as an alternative treatment to support, stabilize, and retain the prosthesis [308,314].
Failures in dental implant treatment can be classified as early or late depending on certain complications. Late failures are usually attributed to peri-implantitis and/or occlusal overload. However, the hypothesis that occlusal overload causes peri-implant bone loss is still being debated [332–335], and scientific evidence for such a relationship has not been fully established [336]. In several studies [337–339], marginal bone defects similar to periodontal lesions found around teeth were created around the peri-implant tissues experimentally, through plaque accumulation promoted by various methods [7]. Although an increasing number of reports have presented the successful regenerative treatment of peri-implantitis defects [7,340–342], histologic evidence of re-osseointegration in humans is lacking. Persson et al. [343] demonstrated only a dense connective tissue capsule formation in the peri-implantitis defects next to commercially pure titanium surfacesin a dog study. However, the same authors recently demonstrated substantial re-osseointegration next to a sandblasted/acid-etched surface in another dos study [343,344]. Also, rapid biologic host recovery of the sandblasted/acid-etched surface was shown, with early radiographic signs of loss of osseointegration [316].
Becktor et al. [330] pointed out that opinions vary as to whether it is advisable to place endosseous implants in growing patients, since there is a lack of scientific knowledge concerning the fate of these implants and associated prosthetic rehabilitation. Bone volume in young patients may not be sufficient for placing the implants in ideal positions to support the prosthesis. Also unknown is what happens psychologically to these patients when no treatment or various temporary solutions are provided. It was postulated that implants in the alveolus of a young, growing maxilla may become significantly buried in bone and their apical portions exposed as the nasal floor and maxillary sinuses remodel. The effect of remodeling in the presented subject can be seen on the maxillary superimposition. Björk et al. [284] showed an average nasal floor remodeling of 4.6 mm in boys aged four to 20 years. The inferior repositioning related to surface remodeling in the present patient was 3.8 mm. Because the continuous lengthening of the maxilla occurred posterior to the implants, the implants moved in harmony with the sagittal displacement and growth of the maxilla. No transverse enlargement could be registered in the tuberosity region of models from age nine to 20 years. By not rigidly connecting the right and left implants, interference at the midline growth suture could possibly be avoided [307].
Bergendal et al. [345] reported that dental implant placement has been a rarely used treatment modality in Swedish children less than 16 years old in the last 20 years. The failure rate in children treated because of tooth agenesis was only slightly higher than that reported for adult individuals, where in young children with ED and anadontia in the mandible, implants seemed to present special challenges, and the failure rate was very high. The small jaw size and preoperative conditions were thought to be the main risk factors.
The fact that the imp does not follow the normal growth of the maxilla or mandible in the three planes of space and behaves like an ankylosed tooth has been demonstrated in some clinical studies [296,300,301]. Additionally, Rossi and Andreasen [346], analyzed the unfavorable clinical and radiographic findings of a single-tooth replacement in a 10 year child and reported 9 mm discrepancy between the implant collar and the CEJ of the adjacent teeth in 25 years of age; additionally they have stated that there was no significant bone loss at the implant site during a 10 year observation.

4.3.  Alternative Treatments
In childhood, a removable partial denture (RPD) or complete overdenture is often the treatment of choice because of the need to easily modify the intraoral prosthesis during rapid growth periods. These treatment options afford the patient and his or her family an easy, affordable, and reversible method of oral rehabilitation. Cooperation of the patient, as well as the support of the family, are necessary of removable prostheses are to be successful in young patients. The functional, esthetic, and psychologic benefits of successful prosthetic restoration for these children should be weighed against the need to change abutments and the possibility that implants will need to be removed at a later date. Rockman et al. [347] reported a technique using magnets to enhance the retention of maxillary and mandibular prostheses in a 9-year-old boy, and suggested that the case report introduces an alternative prosthetic design for children.
It was demonstrated that anadontia has many adverse effects on the psychological and physiological conditions of patients during childhood. Therefore, complete dentures must be applied. As a rule, the younger the child, the easier will be the adaptation to the denture. However, treatment is completely dependent on patient-parent cooperation [348]. Based on oral examination showing total anadontia in both maxillary and mandibular arches, a 5 year old male patient who had ED with anadontia was treated with upper and lower complete dentures. It was reported that retention and stabilization of the dentures were clinically acceptable. Prosthodontic treatment in patients with ectodermal dysplasia is difficult to manage because of the oral deficiencies typical in this disorder and because afflicted individuals are quite young when they are evaluated for treatment. Furthermore, pediatric patients, with oligodontia or anadontia, using prostheses to restore form and function can be a challenge.
In conclusion, the use of endosseous implants is a viable option for dental rehabilitation of children with anadontia or oligodontia. However, the published reports about implant application in young patients are as yet very limited. Well controlled, randomized, prospective longitudinal trials that include a sufficient number of patients are needed; and for a successful outcome, a multidisciplinary approach for oral and maxillofacial rehabilitation of these patients is strongly recommended.