Not all dermal filler is created equal

Prior to embarking on my degree in Pharmacy, I actually started studying Chemical and Pharmaceutical Science, which had a heavy focus on material properties and the chemistry behind it. When I met my lovely Teoxane rep, she starting talking about the chemical properties of the filler and it just immediately made sense. I thought it would be handy to write a blog post on the topic so my clients are aware of why I recommend specific dermal filler in specific areas.

Dermal filler is made of a naturally occurring product, hyaluronic acid which is present in varying concentrations. These chains sit side by side and can remain as 'free' chains or can be chemically bonded (known as cross linking) which will increase the viscosity of the product.

The degree of cross linking in dermal fillers plays a crucial role in determining their physical, chemical, and biological properties and here’s how:

1. Viscosity and Mechanical Strength

   • Higher Degree of Cross Linking:

     • Increased Stiffness and Elasticity: A higher degree of cross links typically results in a firmer product, meaning the filler can better resist deformation and maintain its shape under stress (hence use in areas such as cheeks).

     • Enhanced Lifting Capacity: The greater structural integrity can provide more robust support for tissues, making it suitable for applications that require volume restoration and contouring.

       
       

   • Lower Degree of Cross Linking:

     • Softer and More Flexible: With fewer cross links, the filler tends to be more pliable and less viscous. This can make it ideal for areas requiring subtle, natural movement, like the lips or perioral regions.

     • Natural Integration: The softer consistency may allow for a more even distribution and better integration with the surrounding tissues.

       
       

2. Longevity and Biostability

   • Higher Degree of Cross Linking:

     • Extended Duration: The tighter network of polymer chains is more resistant to enzymatic degradation (e.g., by hyaluronidase- this enzyme breaks down filler over time and hence the need for repeated treatments), which often translates to longer-lasting results.

     • Resistance to Mechanical Breakdown: The robust structure can better withstand the mechanical stresses of facial movements.

       
       

   • Lower Degree of Cross Linking:

     • Faster Degradation:  This means that the effects are not as long-lasting- see note above about hyaluronidase)

     • Reduced Mechanical Stability: These fillers might break down more quickly under repetitive motion or pressure.

       
       

3. Clinical Implications and Customisation

   • Tailored Treatments:

     • Deep Filler Applications: For areas that need significant volumisation and structural support (like the cheeks or jawline), a higher degree of cross linking is often preferred.

     • Superficial Filler Applications: For fine lines or delicate areas, a lower degree of cross linking may be more appropriate to avoid overcorrection or an overly firm appearance.

       
       

In summary, the degree of cross linking directly influences a dermal filler’s firmness, durability, and how it behaves in the face. A higher degree generally means a more robust, longer-lasting filler that provides significant support but might be less malleable, while a lower degree tends to offer a softer, more naturally integrating product that may require more frequent touch-ups.