Mastering G’ Prime, Cohesivity, and Viscosity for Exceptional Results with Products like STYLAGE®, RESTYLANE®, and RADIESSE®.
In the field of aesthetic medicine, the pursuit of predictable, safe, and natural outcomes is paramount. While injection technique is fundamental, the success of a dermal filler treatment relies heavily on an informed product choice. Moving beyond the brand name to understand the physical behavior of the gel beneath the skin is what distinguishes a good practitioner from a true expert. This behavior is defined by a science: rheology.
Rheology is not just an academic concept; it is the most powerful tool at our disposal to predict how a filler will perform post-injection—whether it will provide projection, integrate smoothly into the tissue, or withstand the forces of muscular compression.
In this definitive guide, we will break down the key rheological principles and translate them into practical clinical applications. You will learn to interpret the properties of leading products like STYLAGE®, RESTYLANE®, and RADIESSE® to move from intuition to scientific certainty in every one of your treatments.
1. The Pillars of Rheology: The Science Behind the Perfect Filler
Rheology is the study of how materials flow and deform. In hyaluronic acid (HA) fillers, three main properties dictate their clinical performance: elasticity (G’), viscosity, and cohesivity. Mastering these concepts is essential for selecting the right product for the right indication.
Elasticity (Elastic Modulus or G’): The Lifting and Projection Effect
Elasticity, or G’ Prime (G’), is perhaps the most cited rheological property. It measures the gel’s ability to resist deformation when a force is applied (such as pressure from muscles or gravity) and then return to its original shape. Think of it as the gel’s “memory” or “rebound.”
- Clinically, a high G’ translates to:
- High lifting and projection capacity: Ideal for treatments that require restoring volume and creating structure.
- Resistance to compression: It maintains its shape in areas subjected to pressure.
- When is it crucial? It is fundamental for areas that need structural support, such as restoring malar volume (cheeks), defining the mandibular angle, or projecting the chin.
- Practical Example: For a jawline contouring treatment or to restore structure to cheeks that have lost bone support, we need a product with a high G’. Products like RADIESSE®, with its calcium hydroxylapatite microsphere matrix, offer an exceptionally high G’. Among hyaluronic acids, the more robust formulations in the STYLAGE® range (XL and XXL) are specifically designed to provide this level of projection and support.
Viscosity (Viscous Modulus or G”): Integration and Ease of Injection
Viscosity measures a fluid’s resistance to flow. In simple terms, it is the “thickness” of the gel. High viscosity means the gel is denser and flows more slowly, while low viscosity indicates a more fluid gel.
- Clinically, viscosity affects:
- Extrusion force: Very viscous gels require more force to be injected.
- Tissue integration: A less viscous gel can flow more easily into superficial dermal layers, whereas a more viscous one tends to remain as a more defined bolus.
- Resistance to migration: High viscosity helps the product stay where it is injected.
Cohesivity: The Integrity and Smoothness of the Gel
Cohesivity is the internal adhesive force that holds the gel particles together. It is the product’s ability to remain intact and not fragment, even when molded or subjected to tension. A highly cohesive gel adheres to itself, allowing for smooth and uniform integration into the tissue.
- Clinically, high cohesivity provides:
- Smooth and natural results: It prevents the formation of lumps or irregularities, especially in dynamic areas.
- Resistance to migration: A cohesive gel does not “spread” and maintains its defined shape.
- Adaptability to movement: It is crucial for areas of high facial expression, such as the lips or the perioral region.
- Practical Example: The lips are a perfect example of the need for high cohesivity. They need volume (thanks to G’) but, above all, they must move naturally when speaking and smiling. A gel with low cohesivity could fragment and create a lumpy sensation. The STYLAGE® Special Lips and RESTYLANE® Kysse lines are examples of products designed with high cohesivity to offer an elastic, durable, and natural result in the lips.
Scientific Source: A study published in the Aesthetic Surgery Journal highlights that “there is no single ‘perfect’ filler, but rather an ‘ideal’ filler for a specific indication. Selection should be based on a thorough knowledge of rheological properties to match product characteristics with the anatomical and aesthetic goals of the patient.” (Sundaram, H., & Fagien, S. (2015). Cohesive and Elastic Properties of Hyaluronic Acid Fillers: Focus on G’ and Cohesivity. Aesthetic Surgery Journal.)
2. Selection Matrix by Facial Area: From Theory to Your Clinic
Now, let’s apply these concepts to daily clinical practice. This matrix will serve as a quick reference guide for selecting the most appropriate rheological profile according to the treatment area and the products available at Glow Health.
| Treatment Area | Ideal Rheological Profile | Clinical Objective | Recommended Products on Glow Health |
| Cheeks, Chin, and Jawline | High G’ (Elasticity) High Viscosity High Cohesivity | Projection, structural support, lifting effect. | RADIESSE® STYLAGE® XL / XXL RESTYLANE® Lyft |
| Nasolabial Folds and Marionette Lines | Moderate G’ Moderate Viscosity High Cohesivity | Filling of deep folds with a natural result that adapts to movement. | STYLAGE® M / L RESTYLANE® Defyne JALUPRO® Super Hydro (for bio-remodeling) |
| Lips (Volume and Contouring) | Moderate G’ Low-Moderate Viscosity Very High Cohesivity | Flexible volume enhancement, defined contouring, and a natural result during expression. | STYLAGE® Special Lips / Lips Plus RESTYLANE® Kysse |
| Tear Trough | Low G’ Low Viscosity Moderate-High Cohesivity | Subtle correction without creating excessive volume or the Tyndall effect. Delicate integration. | SUNEKOS® 1200 (as a bio-regenerator) Specific, very low-density HA fillers are recommended for this area.. |
| Fine Lines (Perioral, “barcode lines”) | Very Low G’ Very Low Viscosity Moderate Cohesivity | Superficial filling of fine lines without creating visible volume. | STYLAGE® S RESTYLANE® Fynesse |
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3. Beyond Filling: The Power of Biostimulation
Modern aesthetic medicine seeks not only to fill but also to regenerate. Products like RADIESSE®, JALUPRO®, and SUNEKOS® introduce a different paradigm.
- RADIESSE® (Calcium Hydroxylapatite): It offers immediate correction thanks to its carrier gel, but its true value lies in the CaHA microspheres that act as a scaffold for neocollagenesis. In the long term, it stimulates the body to produce its own collagen, achieving lasting results and a significant improvement in skin quality.
- JALUPRO® and SUNEKOS® (HA and Amino Acid Combination): These products are at the forefront of bio-regeneration. They are not designed primarily for volume but to “awaken” fibroblasts. The patented formula of specific amino acids (Glycine, L-proline, L-lysine, etc.) provides dermal cells with the exact nutrients they need to synthesize new collagen and elastin. They are ideal for treating laxity, dehydration, and loss of elasticity in the face, neck, and body.
Official Source: According to a review article in the Journal of Cutaneous and Aesthetic Surgery, “biostimulators represent a paradigm shift from simple volume augmentation to the restoration of skin quality and structure, offering a more holistic and regenerative approach to facial rejuvenation.” (De Boulle, K., & Heydenrych, I. (2015). Patient factors influencing dermal filler complications: prevention, assessment, and treatment. Journal of Cutaneous and Aesthetic Surgery.)
Conclusion: A Commitment to Aesthetic Excellence
An informed choice, based on the science of rheology, is the true hallmark of a top-tier aesthetic medicine professional. Understanding how G’ prime, viscosity, and cohesivity interact and translate into clinical results will allow you to not only meet but exceed your patients’ expectations.
Taking your results to the next level begins with this commitment: a product selection process that is firmly rooted in science.