Imagine this — to achieve your ideal facial featureshyaluronic acidinjections, but when you look in the mirror the next day, an unnaturally bumpy face stares back at you...? In reality, if you choose the wrong filler type or firmness, such a tragedy can actually happen. But don't worry —
Why do results differ so dramatically depending on which formulation you choose, even though it's the same hyaluronic acid?
- Scientific evidence:The critical difference between "firmness (elastic modulus G')" and "type (monophasic or biphasic)" of hyaluronic acid formulations
- Complete site-by-site strategy:How to choose the optimal filler formulation for each area — nose, forehead, nasolabial folds, etc. — and the golden ratio of injection volume
- Knowledge that protects life:Safe injection techniques that avoid 99.23% of serious risks such as blindness and skin necrosis
"If this were just a little higher, it would be perfect..." "If only this wrinkle would disappear, I could feel confident..." — I understand all too well that feeling you have every time you look in the mirror. That's exactly why I want you to know what you're putting into your precious face and to achieve the best possible results. That's my heartfelt wish.
In fact, there's a truth that many people don't know —
Basic science of hyaluronic acid (HA) fillers and their cellular effects
Shocking fact:Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan abundant in the dermal matrix of the human body, with a molecular weight of 920–1080 kDa — a truly massive molecule. However —
HA is not merely a "wrinkle-filling material." In fact, the latest research has revealed that it produces remarkable rejuvenating effects at the cellular level.
So what happens deep within your skin?
When hyaluronic acid is injected into the dermis or subcutaneous tissue, the extracellular matrix (ECM) is physically stretched, and mechanical tension is applied to fibroblasts. Here's where it gets interesting — receptors called integrins on the fibroblast surface bind to collagen molecules within the ECM and bridge to the cell's internal cytoskeleton.
What's the result?
The stabilization and mechanical stretching of the ECM by injected HA activates and elongates fibroblasts, suppresses collagen-degrading enzymes, and increases the production of type I and type III procollagen for at least 12 weeks. In other words, your own skin begins to rejuvenate.
There's even more 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 beta (TGF-β) levels was confirmed in the area around the injection site.
However, caution is necessary here —
HA fillers carry risks. HA fillers contain hyaluronic acid-associated proteins and the cross-linker BDDE (1,4-butanediol diglycidyl ether), which carry an inherent risk of hypersensitivity reactions. Additionally, finely fragmented HA particles can trigger inflammation and cause side effects such as erythema, mild edema, hematoma, pruritus, and pain.
But there's good news —
In recent years, composite fillers combining polynucleotides (PN) — which promote cellular regeneration — with HA have also been developed. PNs extracted from reproductive cells of salmon and other species promote fibroblast proliferation via adenosine A2A receptors. Experiments have shown that combining 1% PN with HA increases proliferation in human dermal fibroblasts (HDF) and mouse fibroblasts (L929) by approximately 20%.
Latest rheology data: G' (elastic modulus) and G" (viscous modulus) determine the final result
Here's the secret that 95% of people don't know —
Why do results differ so dramatically from one extreme to the other, even with the same hyaluronic acid? The answer lies in "rheology (fluid mechanics) data."
Based on the latest rheology data, understanding the physical properties of fillers is the shortest route to choosing fillers without failure. However —
The reality is that many clinics ignore these important numbers.
The hardness and spreadability of fillers are expressed by two important indicators: G' (storage modulus) and G" (loss modulus). Here is a noteworthy fact——
G' (storage modulus) indicates the "firmness" and "elasticity" of the gel. A higher value means greater resistance to deformation from external pressure and stronger ability to maintain the injected shape. On the other hand, G" (loss modulus) indicates the "viscosity" and "flowability" of the gel.
So, how exactly do they differ in practical terms?
The rheological characteristics differ clearly by product. For example, even within the same Juvéderm series, Juvéderm VOLUMA has a G' of 340.97 Pa, whereas the softer Juvéderm VOLBELLA has a lower G' of 196.10 Pa.
And do you know what difference these numerical values make in the body?
This difference in physical properties directly correlates with volume retention capacity (durability) in the body. In an experiment with injections in the dorsal region of mice, VOLUMA showed a volume of 250 mm³ at 4 weeks post-injection, whereas VOLBELLA was 158 mm³.
And that's not all——
Furthermore, after 24 weeks, VOLUMA decreased to 120 mm³ and VOLBELLA to 98 mm³, scientifically proving that fillers with higher G' (firmer) excel at long-term volume retention.
Filler structure: The difference between monophasic and biphasic
Here is a striking fact——
Actually, the way a formulation spreads within the skin varies entirely depending on its structure. Is the treatment you are considering truly formulated for your intended purpose?
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" 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-like matrix, forming large clumps (pools) of HA within the tissue that compress collagen fibers. This characteristic results in a lower risk of overcorrection 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 of lidocaine hydrochloride.
So, what about monophasic fillers?
On the other hand, monophasic (monophasic) fillers have a uniform and smooth gel structure. In particular, the type called "Monophasic Monodensified" penetrates in a way that spreads collagen fibers within the tissue, delivering a high volumizing effect.
Here is a product worth noting——
Juvéderm VOLUMA (J-V), a representative product, is manufactured using Vycross technology (a technology that cross-links 10% high molecular weight HA and 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 a lower elastic modulus and higher viscosity than biphasic fillers, so it spreads well within tissues and is said to have a low risk of forming nodules (bumps).
And this is the important point——
Additionally, the swelling rate of filler (the proportion that swells as it absorbs water) 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 and expansion after injection.
Complete Site-Specific Filler Guide: Optimal Types and Injection Volumes
Now comes the truly important part——
Each facial region has different anatomical characteristics and aesthetic goals that are required. Undergoing treatment without understanding this difference is exactly like gambling. However——
With the right knowledge, you can definitely achieve your ideal results.
Nose (Non-surgical rhinoplasty)
A surprising fact:Non-surgical rhinoplasty in Asian patientsRhinoplasty(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 shape while resisting pressure from surrounding tissues. For example, products 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 worth noting——
Additionally, the average injection volume for nose procedures is approximately 0.54 mL to 0.64 mL per patient, and it is characteristic that highly effective results can be achieved with very small amounts. In one prospective study using Juvéderm VOLUMA for nose sculpting, the maximum initial injection volume was strictly set at 2.0 mL, and the maximum injection volume at the touch-up four weeks later was strictly set at 1.0 mL to ensure safety.
Now, let's examine the characteristics of Asian noses by the numbers——
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, nasofrontal angle of 146.11 degrees, nasolabial angle of 102.90 degrees, nasomental angle of 134.91 degrees, nasal-facial angle of 29.43 degrees, 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 (broad 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 nasal profile over 48 weeks; however, the biphasic C-C demonstrated superior immediate post-injection lifting effect at the nasal root, while the monophasic J-V demonstrated superior long-term (48 weeks post-injection) nasal root height maintenance.
And here is the most critical safety technique——
For injection techniques into the nose, it is an absolute requirement to inject into the "deep" layer on the periosteum or perichondrium to prevent vascular embolism. Injections are performed systematically from the nasal root in a caudal (downward) direction. For the nasal root approach, insert the needle at a 30–45 degree angle while maintaining the midline, and perform slow microdeposits of a maximum of 0.1 mL per site.
There are particularly dangerous areas——
The nasal tip (nose tip) has extremely abundant blood vessels, so excessive injection should be avoided, and only an extremely small amount of 0.02 mL should be used near the tip. The nasal septumLiftWhen lifting and projecting the nasal tip (height), 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 lateral profile.
Forehead, nasolabial folds, cheeks, perioral area
There is an important technique you should know about here——
For deep horizontal forehead wrinkles, there are reports of long-term wrinkle improvement by using Juvéderm Ultra diluted to 1% concentration with a solution containing lidocaine and epinephrine, with HA concentration adjusted to 16 mg/mL, and injected into the deep dermis using serial threading technique (continuous linear injection method).
For volume loss in the forehead and cheeks, not only HA fillers but also microfat autologous transfer (MAFT) is an option. In numerical comparison—for fat grafting, 10.0–25.0 mL is injected into the forehead and 8.0–18.5 mL into the cheeks, whereas HA fillers use smaller amounts for precise lifting.
What is the actual injection volume?
When using HA fillers for cheek volume enhancement, the average injection volume on first treatment is typically around 1.36 mL.
Also, when targeting long-term collagen neogenesis—
Poly-L-lactic acid (PLLA) fillers are sometimes used for collagen neogenesis in nasolabial folds and cheeks. For PLLA formulations, schedules such as 4 cc injected three times per cheek or 6 cc injected twice per cheek (total 12 cc) have been compared in research, and objective 3D camera evaluation (Vectra) has confirmed significant volume increase in both approaches.
Regarding the perioral region, there is an interesting combination treatment—
For perioral wrinkles (such as vertical lines around the lips), combining onabotulinum toxin A (Botox) at 9 U to suppress muscle movement, along with HA fillers such as Juvederm Ultra or Ultra Plus, provides synergistic improvement compared to HA fillers alone.
Skin booster (skin quality improvement, fine lines, elasticity enhancement)
Now, we turn to revolutionary skin beautification treatment—
In recent years, there has been growing attention to the concept of "skin booster"—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 are the actual treatment method and results?
In skin booster treatments, it is effective to use an automated intradermal injector (mesogun, such as Dermashine Balance) equipped with a stamp-type ultrafine multineedle. In a clinical trial with 60 Korean women, using Elravie Balance with HA concentration of 20.0 mg/mL, 75 points across the entire face were injected at 0.02 mL per point, totaling 1.5 mL, evenly distributed in 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-term moisturizing effects.
What is the mechanism?
By injecting HA in a planar pattern (as field treatment) into the dermis, 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 and firmness.
Serious complication risks and safe injection techniques
This is the most critical section——it can be life-threatening.
Do not be reassured by the phrase "hyaluronic acid is safe." Here is why——
While hyaluronic acid filler is a highly safe treatment, insufficient anatomical knowledge can create the risk of causing irreversible serious complications such as vascular occlusion, skin necrosis, and even blindness.
However, there is reassuring data available——
In a large-scale review analyzing data from 1,600 patients undergoing non-surgical rhinoplasty, HA was used in 1,174 patients, representing 73.38% of the total. In this study, the complication rate for HA was only 0.77%, which was proven to be statistically significantly safer compared to calcium hydroxyapatite (CaHA) at 7.04%.
On the other hand, there is alarming data as well——
In separate past reports, inappropriate filler injection resulted in allergic reactions in 25%, necrosis or embolism in 25%, and foreign body granulomas in 37.5% of cases.
However, HA filler has a major safety trump card——
The greatest reason HA filler is considered safer than other materials is the existence of "hyaluronidase," a reliable dissolving agent (antidote). In the event that filler becomes lodged within a blood vessel and causes blood flow obstruction, subcutaneous injection of hyaluronidase within 4 hours (DeVictor 2021) can prevent skin necrosis.
What are the specific techniques for enhancing safety?
Regarding injection techniques to enhance safety, the gauge and shape of the needle used are also important. For nasal injection, 27-gauge or 30-gauge needles, or 22–30 gauge needles or cannulas are recommended. Particularly when using sharp needles, finer needles reduce tissue trauma (damage) and internal bleeding, enabling precise injection pressure control with ultra-small amounts of less than 0.05 mL.
However, there is a pitfall in a method many physicians rely on——
It is commonly said that the basic safety check is to "aspirate by pulling back the syringe before injection to confirm blood backflow (aspiration test)," but in animal model studies, aspiration correctly identified intravascular puncture only about 53% of the time, and relying solely on this is extremely dangerous.
Then, what is the true safety measure?
Therefore, always maintaining awareness that the needle tip is at a "safe deep layer" on the periosteum or perichondrium, injecting at an extremely slow speed and low pressure becomes the most reliable strategy for preventing complications.
Summary of this article
- Cellular-level rejuvenation effect:Hyaluronic acid (HA) has a biological rejuvenation effect by stimulating fibroblasts and increasing collagen production through stretching the extracellular matrix of the dermis.
- G' value is
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About the author of this article
Hiromitsu NakamuraPhysician, Ginza Clinic
Zetith Beauty Clinic Ginza, Osaka Shinsaibashi, and Fukuoka locations
He has a track record of research presentations at domestic and international academic conferences and is involved in technical guidance and education across Zetith Beauty Clinic. He specializes in precision aesthetic medicine based on anatomical evidence and pursues natural results tailored to each individual's skeletal and tissue structure.