The Science Behind Filler Selection and Use: A YoungMD Connect Discussion With Dr. Jason Bloom

Dr. Jason Bloom gave YoungMD Connect members an informative talk titled “The Science Behind Filler Selection and Use.” Dr. Bloom is a board-certified facial plastic and reconstructive surgeon known for his expertise in both cosmetic and functional procedures.

Dr. Bloom began by giving a brief overview of the basics of hyaluronic acid (HA) fillers. The main points were that they are naturally occurring polysaccharide polymers that retain water, are reversable, and are safe for use in Fitzpatrick skin types IV, V, and VI. Compared to other fillers that cause fibroplasia and/or a low-grade inflammatory reaction, HA fillers cause a stretching of fibroblasts, which stimulates collagen synthesis.

He then went on to talk about HA filler attributes that affect their performance, from concentration and cross linking to elastic modulus (G’) and viscosity. Natural occurring HA has a short half-life and must be cross-linked before use as a soft-tissue filler. Dr. Bloom explained that the more cross linking there is, the more chemical modifications, hence the more the body looks at it as foreign.

Dr. Bloom delved deeper into the science by talking about chemical structures. Natural HA in the skin is composed of long chains with intrinsic non-covalent bonds. Modification and crosslinking with BDDE, the most common cross-linking agent used in commercial HA fillers, leads to shorter and more fragmented HA chains. The higher the degree of cross-linking, the more unnatural the HA would appear, and thus the higher the chance of a foreign body reaction occurring. Furthermore, he showed a representative drawing and talked about how it would be easier to dissolve a product with less cross-linking, as hyaluronidase dissolved the HA, not the cross-links.

Dr. Bloom then went on to discuss filler choice. He gave a brief overview of elasticity and viscosity and how these attributes play into the concept of rheologic tailoring. A product with a high G’ and viscosity is firmer and provides more tissue support, and would therefore be efficacious for volumizing. These would be injected deeply, in the subcutaneous to periosteal plane, and would have less spread leading to contour stability and more sculpting. On the flip side, a low G’ and viscosity would mean a softer, more flowing product efficacious for superficial lines and crepey skin. As one would surmise, these would be injected superficially in the intradermal or superficial subdermal plane and would have better tissue integration with less palpability. Dr. Bloom used a powerful analogy, first showing a picture of the Eiffel Tower to illustrate how a high G’ creates a pronounced, lifted projection, and then presenting an image of a large, dome-shaped building to demonstrate how a moderate G’ produces a smooth, contoured shape. He also presented ultrasound images to visually reinforce the concept.

Finally, Dr. Bloom discussed the importance of anatomy and filler technique. He began by emphasizing that we should always ask why, what, and where and that these questions would help distinguish us. He went on to discuss a landmark study on the fat compartments of the face and the importance of understanding the various deep and superficial compartments. How would one determine if their needle is superficial or deep? If you can lift it off the face, it has to be superficial. Deep needles are stuck down to bone and loculated.

We then learned about different techniques, including the “lift and tack” technique with a high G’ filler, the “layered lifting technique” with a strong volumizing filler, and the importance of volumizing into the deep fat to give a more natural effect.