Imagine this — you received hyaluronic acid injections to achieve your ideal facial features, buthyaluronic acidthe next day when you look in the mirror, you see an unnaturally bumpy face...? In reality, if you choose the wrong filler type or firmness, this tragedy can actually happen. But don't worry —
why do results differ so dramatically depending on the formulation you choose, even though it's the same hyaluronic acid?
- Scientific Evidence:The critical difference between hyaluronic acid formulations' "firmness (elastic modulus G')" and "type (monophasic or biphasic)"
- Complete strategy by treatment area:How to choose the optimal filler formulation for each area — nose, forehead, nasolabial folds, etc. — and the golden ratio for injection volume
- Knowledge that protects life:Safe injection techniques that can avoid 99.23% of serious risks such as blindness and skin necrosis
"If only this were a bit higher, it would be perfect..." "If only this wrinkle would disappear, I could feel confident..." — I understand that painful feeling every time you look in the mirror. That's exactly why I want you to know the true identity of what you're putting into your precious face and achieve the best possible results. That's my heartfelt wish.
In reality, there is a fact that many people don't know —
Basic science of hyaluronic acid (HA) fillers and their effect on cells
Shocking fact:Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan abundantly present in the dermal matrix of the human body, with a molecular weight of 920–1080 kDa — a giant molecule. However —
HA is not just a "wrinkle filler material." In fact, the latest research has revealed that it exerts remarkable anti-aging effects at the cellular level.
So what is happening deep within your skin?
When hyaluronic acid is injected into the dermis or subcutis, the extracellular matrix (ECM) is physically stretched, and mechanical tension is applied to fibroblasts. Here is where it becomes interesting — receptors called integrins on the surface of fibroblasts bind to collagen molecules within the ECM and bridge to the cytoskeleton within the cell.
What is the result?
The stabilization and mechanical extension of the ECM by the injected HA activates and elongates fibroblasts, suppresses collagen-degrading enzymes, and increases the production of procollagen types I and III for at least 12 weeks. In other words, your own skin begins to rejuvenate.
Furthermore, there is remarkable data — in a study where 0.7 mL of HA (Restylane) was injected into photoaged skin, a significant increase in type I collagen production and transforming growth factor-β (TGF-β) levels was confirmed in the area surrounding the injection site.
However, caution is necessary here —
HA fillers do carry risks. HA fillers contain hyaluronic acid-associated proteins and the cross-linking agent BDDE (1,4-butanediol diglycidyl ether), which have inherent risks of triggering hypersensitivity reactions. Additionally, finely fragmented HA particles can trigger inflammation and induce side effects such as erythema, mild edema, hematoma, pruritus, and pain.
But there is good news —
In recent years, composite fillers combining polynucleotides (PN) — which promote cellular regeneration — with HA have also been developed. PNs extracted from germ cells of salmon and other sources promote fibroblast proliferation via adenosine A2A receptors. Experiments have shown that combining 1% PN with HA increases proliferation of human dermal fibroblasts (HDF) and mouse fibroblasts (L929) by approximately 20%.
Latest rheology data: G' (elastic modulus) and G" (viscosity modulus) determine the final result
Here is the secret that 95% of people don't know —
Why does the same hyaluronic acid produce such vastly different results? The answer lies in "rheology (fluid mechanics) data."
Understanding the physical properties of fillers based on the latest rheology data is the shortest route to choosing fillers without failure. However —
The reality is that many clinics ignore this critical figure.
The hardness and spreadability of fillers are expressed by two important indices: G' (storage modulus) and G" (loss modulus). There is a critical fact to note here——
G' (storage modulus) indicates the "hardness" and "elasticity" of the gel. The higher this value, the greater the resistance to deformation from external pressure and the stronger the ability to maintain the injected shape. On the other hand, G" (loss modulus) indicates the "viscosity" and "fluidity" of the gel.
So, how different are they in concrete terms?
The differences in rheological properties by product are clear. For example, even within the same Juvéderm series, Juvéderm VOLUMA has a G' of 340.97 Pa, while the softer Juvéderm VOLBELLA is set lower at 196.10 Pa.
And do you know what kind of differences this numerical variation produces in the body?
This difference in physical properties directly correlates with the ability to maintain volume in the body (durability). In an experiment where filler was injected into the dorsal surface of mice, VOLUMA had a volume of 250 mm³ at 4 weeks post-injection, while VOLBELLA was 158 mm³.
That is not all——
Furthermore, after 24 weeks had passed, VOLUMA had decreased to 120 mm³ and VOLBELLA to 98 mm³, scientifically proving that fillers with higher G' (firmer) are superior at maintaining volume long-term.
Filler structure: The difference between monophasic and biphasic
Here, I will share a striking fact——
In fact, depending on the structure of the formulation, how it spreads within the skin is entirely different. Are the formulations you are considering for your treatment truly suited for your goals?
Undergoing treatment without this knowledge is like walking through an unfamiliar city without a map. And——
HA fillers are broadly classified into "biphasic" and "monophasic" types based on their manufacturing process and cross-linking structure.
First, let me reveal the secret of biphasic fillers——
Biphasic fillers have a structure where HA particles float within a gel, forming large masses (pools) of HA within the tissue that compress collagen fibers. This characteristic results in a lower risk of over-correction after injection. For example, Cleviel Contour (C-C), developed in Korea, is a biphasic HA filler with a very high HA concentration of 50 mg/mL and contains 3 mg/mL lidocaine hydrochloride.
So, what about monophasic fillers?
On the other hand, monophasic (monophasic) fillers have a uniform and smooth gel structure. In particular, a type called "Monophasic Monodensified" penetrates by spreading collagen fibers within the tissue, demonstrating high volumization effects.
Here is a notable product to pay attention to——
Juvéderm VOLUMA (J-V), a representative product, is manufactured using Vycross technology (a technology that cross-links 10% high molecular weight HA with 90% low molecular weight HA), with an HA concentration of 20 mg/mL and contains 0.3% lidocaine.
Furthermore, there is an interesting fact——
Elravie Balance, another monophasic filler (HA concentration 20.0 mg/mL, lidocaine 3.2 mg/mL), has lower elasticity and higher viscosity compared to biphasic fillers, so it spreads well in tissue and is said to have a low risk of forming lumps (nodules).
And this is the critical point——
Additionally, the swelling rate of fillers (the rate at which they absorb water and expand) is inversely proportional to HA concentration and cross-linking degree. In other words, formulations with higher HA concentration and stronger cross-linking have the advantage of being less prone to unexpected swelling or expansion after injection.
Complete Regional Filler Guide: Optimal Types and Injection Volumes
From here is the truly important part——
Each facial region has different anatomical characteristics and aesthetic goals required. Undergoing treatment without understanding these differences is exactly like gambling. However——
With the right knowledge, you can definitely achieve your ideal results.
Nose (Non-surgical rhinoplasty)
Surprising fact:Non-surgicalRhinoplasty in Asians(Filler-based nose sculpting) is an extremely popular treatment. However, there is an important numerical value that many people are unaware of——
Nose sculpting requires fillers with high elasticity (G') and cohesivity that can maintain their shape without being overcome by the pressure of surrounding tissues. For example, fillers with high viscosity and longevity such as Teosyal Ultradeep (25 mg/mL) and Perfectha Subskin (20 mg/mL) are recommended.
Here is a numerical value worthy of attention——
Additionally, the average injection volume per patient for nose treatment is approximately 0.54 mL to 0.64 mL, and it is characterized by achieving results with a very small amount. In one prospective study using Juvéderm VOLUMA for nose sculpting, the maximum injection volume at the initial treatment was strictly set at 2.0 mL, and the maximum injection volume at the touch-up 4 weeks later was strictly set at 1.0 mL, ensuring safety.
Now, let's look at the characteristics of Asian noses in terms of numerical values——
The anatomical average values for Asian noses are: nose height (from nasal root to subnasale) of 49.60 mm, nose length (from nasal root to nasal tip) of 41.15 mm, nasal-frontal angle of 146.11°, nasolabial angle of 102.90°, nasio-labio-mental angle of 134.91°, nasal-facial angle of 29.43°, and nasal volume of 72.70 mL.
This is where it becomes interesting——
Asians, who have intermediate characteristics (medium nose) between Caucasians (narrow nose) and Africans (wide nose), tend to have a low and flat nasal root, with a short nasal tip and columella. Therefore, in a study comparing monophasic J-V (20 mg/mL HA) and biphasic C-C (50 mg/mL HA), both safely and effectively improved the nasal profile over 48 weeks, but the biphasic C-C was superior in lifting the nasal root immediately after injection, while the monophasic J-V was superior in maintaining nasal root height long-term (at 48 weeks).
And here is the most critical safety technique——
As an injection technique for the nose, injecting at the "deep" plane on the periosteum or perichondrium is an absolute requirement to prevent vascular embolism. Injections are performed systematically from the nasal root in a caudal (downward) direction. For approaches to the nasal root, the needle is inserted at an oblique angle of 30–45 degrees, and while maintaining the midline, slow micro-deposits of a maximum of 0.1 mL per site are performed.
There is a particularly high-risk area——
The nasal tip (nose apex) has extremely abundant vasculature, so excessive injection should be avoided, and deposits near the apex should be limited to an ultra-minimal amount of 0.02 mL. The nasal septumLiftWhen lifting up to create projection (height) at the nasal tip, insert the needle vertically and inject 0.2–0.3 mL. Additionally, by injecting 0.1–0.2 mL into the anterior nasal spine (the base of the nose), it is possible to improve the nasolabial angle and create a more refined profile.
Forehead, nasolabial folds, cheeks, perioral area
There is an important technique you should know about here——
For deep horizontal wrinkles on the forehead, reports show that long-term wrinkle improvement can be achieved by diluting a solution containing lidocaine and epinephrine to a 1% concentration, adjusting the HA concentration to 16 mg/mL with Juvéderm Ultra, and injecting it into the deep dermis using the serial threading technique (a method of continuous linear injection).
For volume loss in the forehead and cheeks, not only HA fillers but also micro-autologous fat transfer (MAFT) are options. Comparing numerically—in fat transfer cases, 10.0–25.0 mL is injected into the forehead and 8.0–18.5 mL into the cheeks, whereas with HA fillers, a smaller volume is used to achieve precise lifting.
What is the actual injection volume?
When using HA filler for cheek volume enhancement, the average initial injection volume is often around 1.36 mL.
Furthermore, when aiming for long-term collagen neogenesis——
Poly-L-lactic acid (PLLA) filler is sometimes used for collagen neogenesis in nasolabial folds and cheeks. In comparative studies, PLLA preparations show schedules of 4 cc injected three times per cheek or 6 cc injected twice (12 cc total), and objective evaluation with a 3D camera (Vectra) has confirmed significant volume increase in both approaches.
Regarding the perioral area, there is an interesting combination treatment——
For perioral wrinkles (such as vertical lines around the lips), combining onabotulinum toxin A (Botox) at 9 U with HA fillers such as Juvederm Ultra or Ultra Plus—rather than HA filler alone—suppresses muscle movement and achieves synergistic improvement effects.
Skin Booster (Skin quality improvement, fine lines, elasticity enhancement)
From here, we discuss revolutionary skin rejuvenation treatment——
In recent years, the concept of "Skin Booster" has gained attention—not merely filling wrinkle grooves, but fundamentally improving overall skin quality (texture, hydration, elasticity). However, many people are unaware of its remarkable effects.
Crosslinked fine-particle HA (NASHA) is well-suited for this purpose, with representative products including Restylane Vital (HA concentration 20 mg/mL) and Restylane Vital Light (HA concentration 12 mg/mL) used for delicate areas such as the neck. These contain 3 mg/mL lidocaine to reduce pain.
So what about the actual treatment method and results?
For Skin Booster treatments, it is effective to use an automated intradermal injector with ultra-fine multi-needle stamp-type tips (mesogun, for example Dermashine Balance). In a clinical trial involving 60 Korean women, Elravie Balance with an HA concentration of 20.0 mg/mL was used, injecting a total of 1.5 mL at 75 points across the entire face, 0.02 mL per point, uniformly into the dermal layer.
And the results were remarkable——
As a result, the skin moisture content score measured by Corneometer showed dramatic improvement compared to the placebo group. The moisture increase values from baseline remained consistently high at 43.32 at 8 weeks post-injection, 45.21 at 12 weeks, and 44.68 at 16 weeks, scientifically demonstrating long-lasting moisturizing effects.
What is the mechanism?
By injecting HA in a planar manner (as field treatment) into the dermis in fine increments, the extracellular matrix of the dermis is stabilized, fibroblasts are activated, and their own collagen production is stimulated, resulting in skin that is reborn with moisture-rich firmness and elasticity.
Serious complication risks and safe injection techniques
This is the most critical part—it can be life-threatening.
Do not be reassured by the statement "hyaluronic acid is safe." Here's why—
Hyaluronic acid fillers are a treatment with very high safety, but insufficient anatomical knowledge can lead to serious and irreversible complications such as vascular occlusion, skin necrosis, and even blindness.
However, there is reassuring data—
In a large-scale review analyzing patient data from 1,600 patients undergoing non-surgical rhinoplasty, HA was used in 1,174 patients, accounting for 73.38% of the total. In this study, the complication rate for HA was only 0.77%, which was statistically significantly safer compared to calcium hydroxyapatite (CaHA) at 7.04%.
On the other hand, there is frightening data—
In a separate past report, cases of improper filler injection resulted in allergic reactions in 25%, necrosis or embolism in 25%, and foreign body granulomas in 37.5% of cases.
However, HA fillers have a major safety safeguard—
The biggest reason HA fillers are considered safer than other materials is the existence of "hyaluronidase," a reliable dissolving agent (antidote). In the event that filler clogs a blood vessel and causes circulatory impairment, injecting hyaluronidase subcutaneously within 4 hours (DeVictor 2021) can prevent skin necrosis.
What are the specific techniques to enhance safety?
In terms of injection techniques to enhance safety, the gauge and shape of the needle used are also important. For nasal injections, 27-gauge or 30-gauge needles, or 22–30 gauge needles or cannulas are recommended. Especially when using sharp needles, thinner needles reduce trauma and bruising to tissues, and allow precise injection pressure control with minimal amounts of less than 0.05 mL.
However, there is a pitfall in a method many physicians rely on—
It is often said that the basic safety check is to "aspirate by pulling the syringe to confirm blood backflow (aspiration test)," but in animal model studies, aspiration accurately identified intravascular puncture only about 53% of the time, making it extremely dangerous to rely solely on this method.
So, what is the true safety measure?
Therefore, always being conscious that the needle tip is at a "safe deep layer" on the periosteum or perichondrium, and injecting at an extremely slow speed with low pressure, becomes the most reliable complication prevention strategy.
Summary of this article
- Cellular-level rejuvenation effects:Hyaluronic acid (HA) has a biological rejuvenation effect by stretching the extracellular matrix of the dermis to stimulate fibroblasts and increase collagen production.
- G' value is appropriate
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About the author of this article
Hiromitsu NakamuraPhysician, Ginza Clinic
Zetith Beauty Clinic Ginza, Osaka Shinsaibashi, and Fukuoka locations
With a track record of research presentations at domestic and international academic conferences, he is also involved in technical instruction and education for Zetith Beauty Clinic as a whole. He specializes in precision aesthetic medicine based on anatomical evidence, pursuing natural results tailored to each individual's skeletal structure and tissues.