Orthodontic force induces local bone resorption in mild-type hypophosphatasia mouse model

Area of Science:

• Biomedical Science
• Genetics
• Orthodontics

Background:

• Hypophosphatasia (HPP) is a genetic disorder affecting bone mineralization, often presenting with mild symptoms and premature tooth loss.
• Mild-type HPP is challenging to diagnose due to subtle clinical manifestations.
• The impact of orthodontic forces on HPP patients' oral structures remains largely unexplored.

Purpose of the Study:

• To investigate the effects of orthodontic mechanical stress on teeth and jawbones in a mild-type HPP mouse model.
• To assess alveolar bone response and tooth movement under orthodontic force in Akp2^+/- mice.

Main Methods:

• Mild-type HPP was modeled using Akp2^+/- mice.
• A nickel-titanium closed-coil spring applied orthodontic force to maxillary incisors and first molars.
• Tooth movement, serum alkaline phosphatase (ALP), and CTX-1 levels were measured.

Main Results:

• No significant differences in tooth movement, serum ALP, or CTX-1 levels were observed between HPP mice and controls.
• Increased alveolar bone resorption and reduced cancellous bone quality were noted on the compressed side in HPP mice.
• A higher number of osteoclasts and fibrous infiltration were found at resorption sites in HPP mice.

Conclusions:

• Orthodontic force application did not alter tooth movement or key serum markers in mild HPP mice.
• Compression significantly increased alveolar bone resorption and osteoclast activity in HPP mice.
• Differential diagnosis of mild HPP is crucial before initiating orthodontic treatment to prevent adverse bone reactions.