Implant placement consideration for the adolescent patient
By Nipul Tanna, DMD, MS
A common question asked by many clinicians is ‘when is the optimal time (in terms of age) for placement of implants in the younger patient?
Reports in the literature have demonstrated a high implant survival rate and it has been shown that dental implants placed in the younger patients have integrated well. A recent report resulted in a rating of 100% implant survival. However, at the prosthetic follow up, the survival rate for the final prosthesis dropped to 70%. The 30% change was attributed to loss of proximal contacts and infraocclusion.
Several factors must be considered when answering this question and there are many variations in addition to the chronological age that must be evaluated. Two major components to consider include skeletal development and dentoalveolar development. Significant disparities can exist between the skeletal age, dental age, and chronological age, as well as the gender.
To add further complexity to this question, clinicians must also take into consideration the planned location for implant placement because growth and development of the cranio-maxillary-mandibular complex varies greatly in terms of the process, the direction as well as the rate based on the region. Much of the current understanding as it relates to craniofacial growth is based on the anatomic studies by Enlow and Hans as well as the metallic implant studies by Bjork and Skieller. Additionally, soft tissue changes, which may have a significant impact in the esthetic zone continue well into adulthood and reflect the changes that occur in the aging face.
In the maxilla, for example, postnatal development occurs via intramembranous ossification. The maxilla translates downward and forward during growth and development. An area of bone apposition occurs along the sutures, however, bone remodeling at the surface level occurs in the anterior region. IN fact, the entire anterior portion of the maxilla resorbs as the maxilla develops downward and forward except for a small region in proximity to the anterior nasal spine.
In the mandible, development occurs via two processes. Endochondral ossification at the condylar level leads to an increase in the ramus height, as well as periosteal apposition at the posterior aspect of the mandible, which leads to an increase in length of the mandibular body.
IN addition to the skeletal changes, the dentoalveolar changes occur in both the primary and secondary dentitions. During normal vertical growth, in health, active dentoalveolar eruption is proportional to the amount of skeletal growth that occurs vertically in the maxilla as well as the mandible, allowing the dentition to remain in occlusion and to maintain facial height throughout the developmental process.
During this active eruption process, the entire attachment apparatus and the tissues that comprise it migrate coronally resulting in a net increase in the height of the crestal bone, as well as the gingival complex. Any aberration in this process, such as an ankylosed tooth, will manifest clinically in the form of a vertical deficiency due to a lack of normal eruption and therefore an insufficient coronal migration of the dentoalveolar and dentogingival complex.
In terms of growth and development, well osseointegrated implants behave in a manner similar to an ankylosed tooth. As the craniofacial complex and the dentoalveolar complex within it continue to grow, any portion that is ankylosed will remain “behind.”
The clinic manifestation of this scenario, over time, will be a height discrepancy in both hard and soft tissues as well as an occlusal disparity resulting in an infraocclusion of the implant prosthesis. Brugnolo and co-workers reported similar findings of infraocclusion in patients aged 13-20-14.5 years. Animal studies by Thilander as well as by Sennerby have shown similar findings. In theory, if placed too early and there is substantial growth post implant placement, it is possible for an implant to become buried, resulting in further complications.
Under certain conditions such as severe ectodermal dysplasia, osseointegrated dental implants have been quite beneficial for the young patient. Most cases have required a prosthesis remake to accommodate changes in the occlusion related to growth. For these patients, implant placement in the anterior mandible has shown a more favorable outcome compared to other areas.
The end goal of the developmental process results in a functional equilibrium that is within a dynamic environment and will continue to display changes within that environment. The goal of the clinician aims to provide a treatment modality that can safely adapt within that functional equilibrium without resulting in an undesired sequela.
Pressures from parents, patients and significant others, along with the psychological pressures, add more complexity to the decision-making process. Circling back to the original question, with all factors considered, the most favorable time for implant placement would be at the end of the growth curve or nearing its completion. The determination of this timing can be based on the evaluation of each patient’s growth chart, measurement of the patient’s stature, hand/wrist radiographs and superimposition of serial cephalometric radiographs. When these indicators suggest completion of growth, the likelihood of an undesired outcome is less.