Abstract
Orthodontic anchor screws, which made from titanium are widely used as anchorage units in orthodontic treatment. However, there are some problems, including dropout during treatment and the invasive nature of screw removal. An orthodontic anchor screw, in which the main component is a bioabsorbable material is therefore sought. We investigated the biological evaluation of a prototype material composed of polyglycolic acid (PGA) and hydroxyapatite (HAp). Five types of PGA/HAp composites were examined. The HAp compound ratios by weight were 0, 5, 10, 30 and 50 %. We examined the effects of the PGA/HAp components on the gene and protein expression of collagen type 1 (COL-1), alkaline phosphatase (ALP) and osteocalcin (OCN) from mouse osteoblasts (MC3T3-E1) in vitro by real-time a PCR and an ELISA. Furthermore, we evaluated the osteoinductive potential in vivo, in a rat calvarial defect model after subjecting samples to a μ-CT image analysis. COL-1 and ALP production peaked on day 7, and increased dependent on the concentration of HAp. OCN production also increased in a dose- and time dependent manner up to day 10 in vitro. In the in vivo study, μ-CT image analyses showed that newly formed bone areas in defects for PGA/HAp disk were significantly higher at two and three months after surgery than in controls that underwent sham operations. The results suggest that the biological properties of the PGA-based trial prototype were increased with the addition of HAp. An orthodontic anchor screw constructed of PGA may be useful for orthodontists.
