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.