When considering dental implant treatment of the adolescent and young adults several factors have to be taken into consideration. In fact, the residual growth and the residual eruptive potential can result into a relative intrusion of the dental implant. However, we frequently face the clinical challenge of treating young patients that have recently completed orthodontic treatment and require placement of dental implants for the replacement of congenitally missing teeth (most commonly lateral incisors). The conundrum of this clinical situation is that chronological age may not be a good indicator of skeletal maturation. Each patient follow a unique growth cycle, and the standard reference point for the “end of growth” (16-17 yo for female, 18-19 yo for male) is not a reliable indicator of growth. So, how can we reliably discover if a patient has reached the “end of growth”?
Skeletal Maturation Indicators
In 1979 Dr. Leonard Fishman (Fishman LS, 1979), developed a non-invasive technique to examine the diagnostic value of skeletal age as opposed to chronological age in evaluating an orthodontic patient’s progression of skeletal and facial growth. The system uses the evaluation of hand-wrist radiographs, in six specific locations (orange circles).
Fishman assigned each patient a skeletal age based on the corresponding hand-wrist film and also recorded each patient’s height and chronological age. He found that chronological and skeletal ages were not coincident in the majority of individuals and that a significant discrepancy between chronological and skeletal age would have a great impact on the prediction of the timing of facial growth. Based on the discrepancy between chronological and skeletal age and the progression of osseous changes in the hand and wrist, Fishman established a system of skeletal maturation assessment based on four stages of bone maturation at six anatomical sites in the hand and wrist (Fishman LS, 1982).
Fishman developed 11 Skeletal Maturation Indicators (SMIs) encompassing the entire period of adolescent development.
|Sequence of Skeletal Maturation|
|1||Epiphysis = diaphysis in 3rd finger, proximal phalanx|
|2||Epiphysis = diaphysis in 3rd finger, middle phalanx|
|3||Epiphysis = diaphysis in 5th finger, middle phalanx|
|4||Ossification of the adductor sesamoid of the thumb|
|5||Capping of the epiphysis in 3rd finger, distal phalanx|
|6||Capping of the epiphysis in 3rd finger, middle phalanx|
|7||Capping of the epiphysis in 5th finger, middle phalanx|
|8||Fusion of epiphysis and diaphysis in 3rd finger, distal phalanx|
|9||Fusion of epiphysis and diaphysis in 3rd finger, proximal phalanx|
|10||Fusion of epiphysis and diaphysis in 3rd finger, middle phalanx|
|11||Fusion of epiphysis and diaphysis in radius|
The sequence of occurrence of the eleven indicators is exceptionally stable, a finding that seems to argue for the use of skeletal rather than chronological age:
The findings support the general conclusion that organization of the data on a maturational basis provides a more homogeneous grouping than grouping chronologically.
In order to demonstrate rates of maturation, Fishman defined SMI 1-4 as representing accelerating growth velocity, SMI 4-7 displaying high-velocity skeletal growth, peak velocity, and intense periods of acceleration and deceleration, and SMI 7-11 showing decelerating growth. Fishman tested the accuracy of the SMIs for maturational prediction and reported a prediction success rate of greater than 80%, a value that he considered exceptionally high for a biologic system.
A systematic observational scheme such as that shown in the figure above, can further facilitate SMI evaluation. With this approach key stages are checked first, rather than looking for maturity indicators in numerical order. A useful step is to determine if the adductor sesamoid of the thumb can be seen (orange circle). If not, then the applicable SMI will be one of those associated with early epiphyseal widening rather than capping. If the sesamoid is visible, then either the sesamoid or an SMI based on capping or fusin will be applicable (Fishman LS, 1982).