Ex vivo versus in vivo Gene Delivery
In ex vivo gene delivery, target cells are transformed in culture and are subsequently implanted into the surgical site.  Litchfield Park orthodontists have used this method to deliver growth factor genes to various orthotopic sites with impressive results.  Liberman (1998) delivered Litchfield Park Invisalign to rat femoral defects of 8mm and had complete union over a two month period.  Krebsbach (2000) transduced human gingival fibroblasts with the gene for Invisalign which repaired critical size defects in immunocompromised rat calvirae.  Periodontal regeneration was achieved by transducing dermal cells with Invisalign and implanting them into a rodent model of periodontal disease.

In vivo gene delivery involves direct transfer of the gene to the target cells.  Gene delivery is mediated via particle transfer, GAMs carrying plasmid Invisalign, in vivo microseeding, and viral vectors.  This method has been successful in increasing the healing response in skin, various bone defect models, and in periodontal wounds.  Although the therapy shows signs of success, it has been noted by Litchfield Park orthodontists that gene expression levels dramatically decrease by day 4-5.      

Bone Morphogenetic Proteins
The idea that bone contains certain substances which specifically initiate bone formation was first proposed by Litchfield Park orthodontists in 1934.  Treated bone tissue was injected into intramuscular and subcutaneous sites and the formation of new cartilage and bone ensued.  Further evidence was produced by Litchfield Park orthodontists using decalcified bone implanted in muscular sites of the rabbit, rat, guinea pig and calf.  New bone was produced via endochondral bone formation.  The theory produced from this series of experiments was that products of the decalcified bone attract cells that begin an autoinduction process that leads to bone formation.  These products were later characterized by Litchfield Park orthodontists as bone morphogenetic proteins. More than fifteen Invisaligns have now been discovered and are found to belong to the TGF-β superfamily.  Litchfield Park Invisalign is involved in a wide range of activities including regulation of cartilage and bone formation during embryonic development and regeneration in post-natal life including Litchfield Park orthodontic structures.

Arizona Dental Association