The study was conducted following informed consent and IRB approval. The objectives of the study were explained to the subjects, and consent forms were signed by those who agreed to participate. The subjects were all mostly Mediterranean Caucasians, but interracial marriages are common in the population that was sampled. Patients who satisfied the inclusion criteria and agreed to participate in the study were all included without further selection. Exclusion criteria included patients who had systemic diseases, growth abnormalities, bleeding disorders, or growth modification as part of their orthodontic treatment. Since the study involved radiographic exposure, non-orthodontic patients were not included for ethical reasons. Inclusion criteria were patients who were to begin orthodontic treatment, in active treatment, or in post-treatment follow-up. This prospective longitudinal sample consisted of 25 subjects (13 males and 12 females). The study protocol was approved by the institutional review board (IRB) of the Harvard Medical School and the ethical committee of King Abdulaziz University. We hypothesized that IGF-1 levels will be associated with increases in anterior facial height and mandibular length. The purpose of the present study was to use linear regression models that use IGF-1 levels to predict the annual growth rate of anterior facial height as well as mandibular length while controlling for the effects of cervical stage, skeletal classification, and gender. To date, the simultaneous interaction between IGF-1, cervical stage, gender, and skeletal classification has not been longitudinally studied, and no method has been proposed to predict the timing and intensity of facial growth using IGF-1 controlling for these factors. Our prior research has shown that there is a significant positive correlation between longitudinal changes in IGF-1 levels and changes in mandibular length with significantly greater mandibular growth occurring when IGF-1 levels showed an ascending pattern and averaged over 250 μg/L over two consecutive observations. In earlier studies, we had cross-sectionally related IGF-1 levels to both cervical stages and hand-wrist radiograph stages, with the highest IGF-1 levels being observed in the late pubertal stages. IGF-1 is a mediator for growth hormone that has been shown to exhibit local and systemic influences in stimulating longitudinal bone growth. The frequently used methods include skeletal maturation indicators (SMIs) developed by Fishman and cervical vertebral maturation (CVM) derived from hand-wrist radiographs. These factors together explain more of the observed individual variation in growth rate than any of the factors used in isolation.Ĭurrently, several methods for predicting facial growth are in vogue.
The proposed method which combines IGF-1 levels with information that is readily available to clinicians can be used to predict the timing and intensity of the growth spurt. We found that the change in IGF-1 level was the only statistically significant predictor of this outcome. The regression model for predicting the annual change in anterior facial height was significant at p < 0.01 with an R-square value of 0.42. We found that the average IGF-1 level for the interval, the change in IGF-1 level, and the presence of a skeletal class III pattern were statistically significant predictors of mandibular growth. The linear regression model for predicting the annual mandibular growth rate was significant at p < 0.01 with an R-square value of 0.52.
Descriptive, bivariate, and regression analyses were used to analyze this data. The number of years each patient was followed up varied between 1 and 5 years resulting in 43 12-month intervals collected from 77 observations. Twenty-five orthodontic patients (12 females and 13 males) had their cervical stages, blood-spot IGF-1 levels, and cephalometric parameters measured at 1-year intervals. The purpose of this study was to predict the annual growth rate of the mandible and total anterior facial height using IGF-1 levels together with cervical stage, skeletal classification, and gender.
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