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Summary: Background: Tissue expansion has been widely used to provide additional soft tissue for clinical reconstruction. Rapid expansion requires a much shorter clinical period than conventional expansion; however, less natural skin growth occurs resulting in a larger stretch-back ratio and insufficient extra soft tissue for clinical use. In this study, hyperbaric oxygen therapy (HBOT) was used in the inflation phase of rapid expansion to increase natural skin growth. Methods: Twelve rabbits were divided into two groups. Each group received rapid expander inflation every day. One group received HBOT and the other did not. Blood flow in the expanded skin of each rabbit was assayed in the 10-day inflation phase. After the inflation phase, a rectangular expanded flap of each rabbit was harvested. The instant stretch-back ratio, tension, weight and histological characteristics of the flaps were evaluated. Results: (1) After the second inflation day, the mean blood flow of the HBOT group became significantly higher than that of the control with each day (P < 0.05). At the last day, the blood flow of the HBOT group increased to 131 ± 17 pu, while the control group decreased to 35 ± 5 pu. (2) The mean instant stretch-back ratio of the HBOT group under no-tension conditions was 29 ± 4%, which was significantly less than that of the control group, 46 ± 3% (P < 0.01). (3) The mean flap tension of the HBOT group was 15.3000 ± 1.47648 g and 12.9833 ± 0.73598 g in the transverse and longitudinal axis, respectively, both significantly smaller than that of the control group (33.9167 ± 4.78390 g and 26.5000 ± 2.45031 g, respectively) (P < 0.01). (4) Mean per unit flap weight of the HBOT group was 0.221 ± 0.005 g cm−2, significantly heavier (P < 0.01) than that of the control group (0.143 ± 0.010 g cm−2). (5) Histologically, the epidermal layer and thickness of the expanded skin of the HBOT group were much thicker than those of the control group, and more vessels were visible in the subcutaneous tissue. Conclusions: The use of HBOT in the inflation phase of rapid expansion can effectively promote blood flow in the expanded skin, increase its natural skin growth and reduce the instant stretch-back ratio and tension of expanded skin. [Copyright &y& Elsevier]

The purpose of this study was to investigate the effects of bisphosphonate (BP), an inhibitor of bone resorption, on the remodeling of the rat sagittal suture after rapid expansion. Wistar strain male rats were divided into 4 groups and subjected to rapid mechanical expansion with an initial force of 60 g for 3 days. Immediately after the sutural expansion, the appliance was removed in 2 of the groups. In the S group, half of the animals were injected with saline solution daily for 3 days and the other half were injected daily for 7 days prior to sacrifice. In the B group, half of the animals were injected with bisphosphonate daily for 3 days and the other half were injected daily for 7 days prior to sacrifice. The remaining 2 groups underwent 7 days of mechanical retention before the appliance was removed. In the SR group, half of the animals were injected with saline solution daily for 3 days and the other half were injected daily for 7 days prior to sacrifice. In the BR group, half of the animals were injected with bisphosphonate solution daily for 3 days and the other half were injected daily for 7 days prior to sacrifice. The calvariae were fixed in 4% neutral formalin, decalcified, and embedded in paraffin. The amount of relapse and the relevant bone remodeling were evaluated in terms of a relapse ratio and the number of osteoclasts. The relapse ratio was 54.11% in the S group and 32.53% in the B group 7 days after the injection. This ratio was 25.13% in the SR group and 9.60% in the BR group. The number of osteoclasts 3 days after injection was 15.47 in the S group, which was significantly greater than the 5.26 present in the B group. This number was 7.08 in the SR group, which was significantly greater than the 1.83 in the BR group. These results demonstrate that the injection of BP after rapid expansion, if combined with mechanical retention, may produce more secure retention by inhibiting bone resorption, indicating a possibility of employing a pharmaceutical aid to decrease the skeletal relapse after mechanotherapy in clinical orthodontics. [ABSTRACT FROM AUTHOR]