Salivary insulin-like growth factor-1 (IGF-1) and bone alkaline phosphatase (BALP) levels during mandibular advancement with Twin Block appliance: A longitudinal study

Abstract

Objective:

To assess salivary insulin-like growth factor-1 (IGF-1) and bone alkaline phosphatase (BALP) levels during mandibular advancement with Twin Block appliance.

Methods:

The study enrolled 49 participants with skeletal Class 2 malocclusion, a retrognathic mandible, positive visual treatment objective (VTO), horizontal to average growth pattern and cervical vertebrae maturation index stages 3–4 (CVMI). Participants were treated with Twin Block appliance (Twin Block group [TBG]; n = 39). Salivary samples were collected before treatment (T0), at 7–10 days (T1), 6–10 weeks (T2), 8–10 months (T3) and after treatment (T4). Non-compliant participants formed the non-compliant group (NCG; n = 10). Lateral cephalograms were obtained for cephalometric evaluation. Statistical analyses compared salivary IGF-1 and BALP levels and cephalometric parameters within and between groups.

Results:

The final sample included 39 participants in the TBG (17 boys, 22 girls; mean age =12.56 ± 1.09 years) and 10 participants in the NCG (5 boys, 5 girls; mean age =12.7 ± 1.16 years). A significant difference was observed in the salivary IGF-1 and BALP levels within the TBG across different time intervals. In the TBG, IGF-1 increased significantly at T1, and BALP significantly increased at T2 and T3. The NCG showed no significant changes in levels of IGF and BALP. A significant positive correlation between IGF-1 and BALP was noted at T1 in the TBG (P <0.05), whereas a significant negative correlation was observed at T2 and T3 (P <0.05). Mann–Whitney test showed a significant increase in mandibular length in TBG compared to NCG. Cephalometric analysis revealed significant improvements in mandibular length in TBG compared to NCG between T0 and T4.

Conclusions:

The study demonstrated a significant increase in salivary IGF-1 levels within 7–10 days, with BALP levels peaking at 6–10 weeks. These findings suggest a potential role of IGF-1 and BALP in the biochemical response to Twin Block appliance therapy.

Plain language summary

Changes in levels of growth markers in the saliva when wearing a Twin Block brace

Why was the study done? This study was done to find out if the levels of growth markers in the saliva changed when patients wore a Twin Block brace.

What did the researchers do? The researchers included 49 young people (average age = 12.5 years) with a small lower jaw. Saliva samples were collected at different time points during brace treatment to measure changes in the levels of growth markers in the saliva.

What did the researchers find? The researchers found that in the young individuals who wore the Twin Block brace well, one growth marker increased early in treatment and the other increased later in treatment. This suggests that the growth markers had a role at different stages of the brace treatment. Those young people who did not wear the brace had little change in the level of the growth markers. In addition, the growth of the jaw was greater in the adolescents who wore the Twin Block brace compared to those who did not.

What do the findings mean? The results suggest that the two markers of growth that were measured play key roles in the way the jaw adapts and grows during treatment with a Twin Block brace. They could act as a useful way to check treatment progress.