Is there an optimal initial amount of activation for midpalatal suture expansion? : A histomorphometric and immunohistochemical study in a rabbit model

Effect of platelet rich plasma injection on bone formation in the expanded mid-palatal suture in rabbits: a randomized controlled animal study

BACKGROUND

Mid-Palatal suture expansion needs long retention period due to delayed bone formation in the expanded suture. Platelet-rich plasma (PRP) is a concentrated source of growth factors which increase bone formation. The aim of this study was to evaluate the effect of PRP injection on bone formation in expanded mid palatal suture in rabbits.

METHODS

In this prospective randomized controlled animal study, Twenty male rabbits (8-weeks-old) were subjected to mid-palatal expansion for 5 days. Animals were afterwards randomly divided into control group A & study group B. PRP was prepared and injected in the mid-palatal suture in animals belonging to group B only. After 6 weeks of retention, all animals were euthanized, and premaxillae were prepared for histological, histomorphometric and immunohistochemical analysis. Student t-test and paired t-test were used to compare the means of the two groups and within the same group respectively. Significance level set at p ≤ 0.05.

RESULTS

Histomorphometric analysis revealed a significant increase (p < 0.001) in the mean percentage of new bone in the study group (14.4%) compared to the control (1.4%). Suture width in study group was significantly wider than the control group (278.8 ± 9μms and 120.4 ± 3.4μms, p < 0.001). There was a significant increase in vascular density in study group than control group (309 ± 65.34 and 243.86 ± 48.1, p = 0.021). Osteopontin immuno-expression revealed a significant increase in optical density in study group than control group (0.21 ± 0.02 & 0.12 ± 0.01, p < 0.001).

CONCLUSIONS

In rabbit model, PRP injection can accelerate new bone formation in the expanded mid-palatal suture when compared to the control. This could hopefully result in a more stable midpalatal expansion and a reduced retention period.

Bone formation after surgically assisted rapid maxillary expansion: comparison of 2 distraction osteogenesis protocols

OBJECTIVE

The aim of this study was to compare bone formation between 2 distraction osteogenesis protocols by analyzing cone beam computed tomography (CBCT) scan data.

STUDY DESIGN

In this retrospective study, the efficacy of 2 different surgically assisted rapid maxillary expansion protocols (group 1 [G1], 3 × 0.25 mm/d; group 2 [G2], 1 mm start followed by 2 × 0.25 mm/d) was analyzed using CBCT scans obtained at 3 time points: preoperatively (T0), immediately after surgery (T1), and 6 months after surgery (T2). Bone formation at T0, T1, and T2 was analyzed using the Dolphin Imaging 11 program.

RESULTS

At T1, both groups had significantly higher bone volume than at T0 (G1, 135.6 vs 124.65 mm³, respectively; G2, 153.49 vs 118.9 mm³, respectively), with no significant difference between groups (P = .6). Moreover, bone density measured in the region of interest was similar between groups at all 3 time points; however, in both groups, bone density was significantly lower at T1 and T2 than at T0 (P < .01), with no difference between T1 and T2.

CONCLUSIONS

Bone density between the incisors decreased with progressive distraction (i.e., increasing volume), regardless of the distraction protocol used; thus, both protocols can be used safely in clinical practice. Nevertheless, our results indicate that stress should not be applied to the incisors within 6 months of surgery, regardless of the protocol used. Surgeons and orthodontists should therefore consider immature bone formation and avoid using excessive force to close a diastema.