Authors of an article in the September issue comparing implants and canine substitution apparently ignored the evidence of long-term implant failure in the anterior maxilla regarding esthetic aspects (Schneider U, Moser L, Fornasetti M, Piattella M, Siciliani G. Esthetic evaluation of implants vs canine substitution in patients with congenitally missing maxillary lateral incisors: are there any new insights? Am J Orthod Dentofacial Orthop 2016;150:416-24).
Judging the success of implant therapy in the anterior maxilla by pictures taken 12 to 24 months after orthodontic treatment and any restorative work disregards knowledge on long-term stability in terms of infraocclusion and health of the periodontal tissues: peri-implantitis and peri-implant soft tissue discoloration associated with the decrease in thickness of the buccal alveolar bone plate previously available from retrospective studies or animal experiments, and knowledge based on years of clinical experience as well.
It is undisputed that occlusion should be regarded as a dynamic rather than a stable interrelationship between facial structures. This must be considered in orthodontic treatment planning as well as in assessment of stability after implant treatment. A continuous increase of palatal height up to adulthood seems to be an effect of a slow continuous eruption of the teeth. This finding is also of significance in explaining the infraposition of implant-supported crowns.
Therefore, in adults’ facial development, continuous tooth eruption and mesial drift have been identified as compromising factors for implant placement. Osseointegrated dental implants, like ankylosed teeth, alter position as growth-related changes occur in the jawbones. In the maxillary incisor region, infraocclusion may occur, especially for lateral incisors, due to a slight continuous eruption of adjacent teeth and postadolescent craniofacial changes. Mature adults who had received single implants may exhibit major vertical steps resulting from osseointegrated fixtures.
Various signs of infraposition of single-implant restorations were observed in long-term follow-up studies with a female predilection. Their rates varied with age. This phenomenon was much more conspicious during the second and third decades of life as compared with the fourth and fifth decades. Little information is available on the biologic mechanism behind this pattern.
In implant-supported prostheses, the most common reason for crown replacement was infraposition of the implant crown. Based on objective parameters, baseline esthetics was considered poor.
Furthermore, periodontal problems may arise, with marginal bone loss around the adjacent teeth and bone loss buccally to the implants. It could be shown that orthodontic space closure patients had better periodontal health compared with implant substitution patients.
An awareness of the risk of treatment failures and complications may be required since implant treatment outcomes are not as predictable as treatment outcomes of conventional therapies particularly when esthetic considerations are the overriding concern. In females, due to an eruptive movement of the teeth, vertical development of their investing tissues, posterior rotation of the mandible, and uprighting of the maxillary incisors throughout life, clinicians should refrain from placing implants in the anterior maxilla. Male patients are less prone to implant submersion, but those with narrow teeth and therefore a short distance between a planned implant and the adjacent teeth should be treated with care. To prevent failures and complications and to establish optimal treatment goals and results, the planning for implant placement in the anterior maxilla should be done with caution not only in adolescents but also in adults before the fourth decade of life. When canine substitution is not possible in patients with multiple agenesis of teeth, the use of temporary mini-implant supported crowns might offer a solution, but we need more research in basic and clinical follow-up studies of large samples on this subject to make evidence-based decisions.