Rheologic and Physicochemical Properties Used to Differentiate Injectable Hyaluronic Acid Filler Products

A novel empirical and rheometric assessment of viscoelastic hydrogel implant cohesiveness

Therapeutic implantable hydrogels are increasingly utilized in medicine due to their versatile viscoelastic properties. Nonetheless, the clinical efficacy and longevity of these products is predicated on their ability to retain structural integrity post-implantation. Gel cohesion, defined as the capacity to resist fragmentation, has lacked empirical standardization, especially in high shear environments, with present methods often conflating this mechanical parameter with gel ductility or qualitative perceptions of tackiness. In this study, we introduce a novel quantitative method of cohesion analysis termed the Modulus of Cohesion (MOC). The MOC is derived from rheometric strain sweep testing by calculating the difference between the elastic and viscous moduli from 0% strain to the crossover point. This novel parameter provides a direct measure of mechanical energy storage and dissipation balance, accounting for linear and nonlinear deformation in shear strain. Eleven commercially available hyaluronic acid gels are evaluated using this method, alongside uniaxial tension and drop weight methods to establish correlations between MOC and existing cohesion metrics. Additionally, haptic sensory analysis and aqueous dispersion methods from previous reports are correlated with rheometric and mechanical tests. Our results demonstrate that MOC provides a reliable, reproducible measure of gel cohesiveness, correlating strongly with other quantitative methods with augmented precision.

Identifying Minimum Single Dose of Recombinant Human Hyaluronidase for In Vitro Dissolution of Twenty-Two Hyaluronic Acid Fillers

PURPOSE

As the use of hyaluronic acid fillers continues to increase for clinical and aesthetic purposes, associated complications continue to rise as well. Excess hyaluronidase is often used to dissolve filler, which has its own set of adverse effects. This study analyzes 22 commercially available fillers to delineate the lowest single dose of recombinant human hyaluronidase (RHH) required to fully dissolve each filler within 6 hours across 3 trials.

METHODS

0.2 ml aliquots of each of 22 hyaluronic acid fillers were placed in wells. A single dose of RHH, titrated to a minimum volume of 0.45 cc, was administered to the center of the aliquot, to a maximum of 140 units. RHH amounts were as follows: 0, 2.5, 5, 10, 20, 40, 60, 80, 100, 120, or 140 units RHH. Bird's eye and lateral photographs were taken to monitor dissolution progress at several time points over the 6-hour period to monitor aliquot height and appearance changes. Filler aliquots were left undisturbed for 6 hours, after which dissolution was confirmed by stirring the aliquot on video recording. This process was repeated 3 times per filler to determine the minimum dose of RHH required to consistently dissolve each aliquot.

RESULTS

For each of the 22 fillers, the minimum dose of RHH required for dissolution was identified with consistent results across 3 trials, demonstrating reliability. Juvéderm Volbella, Juvéderm Vollure, Juvéderm Skinvive, Restylane-L, Restylane Lyft, and Restylane Silk were identified as the least resistant fillers, requiring ≤20 units to dissolve. Resilient hyaluronic acid (RHA) 2, RHA 3, RHA 4, Belotero Volume, Juvéderm Ultra XC, Juvéderm Volux, Restylane Kysse, and Revanesse Versa were classified as most resistant, requiring ≥120 units to dissolve.

CONCLUSIONS

This study identifies the minimum single dose of RHH from 2.5 units/0.2 ml to 140 units/0.2 ml for dissolution of 22 different hyaluronic acid fillers over 6 hours. These results paired with previous studies help elucidate the dissolution profiles of each filler in the context of their rheological properties, further informing physicians on how to optimally dissolve different hyaluronic acid fillers in a clinical setting.

A lubcan cross-linked polyethylene glycol dimethyl ether hydrogel for hyaluronic acid replacement as soft tissue engineering fillers

The structure of soft tissues is often destroyed by injury and aging. Injectable fillers eliminate the need for surgery and enhance repair. Hyaluronic acid-based hydrogels are commonly employed for their effectiveness and biocompatibility. However, hyaluronidase breaks them down quickly. Lubcan, a naturally sourced microbial extracellular polysaccharide, has demonstrated significant water absorption and retention capabilities, as well as lubricating properties comparable to those of hyaluronic acid. In this study, a novel injectable and implantable hydrogel was created from lubcan by adding polyethylene glycol diglycidyl ether as a cross-linking agent. Lubcan hydrogels exhibit exceptional thermal stability, favorable swelling behavior, in vitro degradation, compressive strength, injectability, and rheological properties, all while preserving the integrity of their three-dimensional porous structure. In vitro tests indicated that the lubcan hydrogel was non-cytotoxic, did not adhere to blood cells, and exhibited good hemocompatibility. Compared to the subcutaneous injection of commercially available hyaluronic acid hydrogels, lubcan hydrogels demonstrated superior integrity, persistence, and a softer texture in Balb/c mice after 16 weeks. At the same time, lubcan hydrogel is non-toxic to organs, does not affect blood biochemical test values, and is non-immunogenic in mice. These findings suggest that lubcan hydrogel may be a promising new superficial soft tissue filler.

A Prospective Clinical Trial Evaluating the Efficacy and Safety of Non-Animal Stabilized Hyaluronic Acid Injections for Non-Surgical Rhinoplasty

Background: Non-surgical rhinoplasty with hyaluronic acid (HA) filler is a three-dimensional reshaping technique that achieves tissue enhancement by placing HA deep to nasal skin. Due to its unique rheology, Restylane® Lyft (HA-L, Galderma, Uppsala, Sweden) may be particularly well-suited for injection rhinoplasty, as it has high gel firmness (G') for strong structural support with minimal integration propensity. Methods: A prospective clinical trial was conducted to evaluate HA-L use for non-surgical rhinoplasty. Thirty-three females were observed over eight months, using the following schedule: Visit 1 = Baseline/Treatment 1; Visit 2 = Optional touch up (Week 2); Visits 3-6 = Follow-ups (Months 1,3,6,8). The primary endpoint was subject improvement at Month 1 assessed by a blinded evaluator using the Global Aesthetic Improvement Scale (GAIS). Subject satisfaction and adverse events (AEs) were also evaluated. Results: A deep, periosteal injection using a bolus technique and 0.34 cc of HA-L was most often used. Seven cases of positive aspiration occurred in 167 injection points (4.19%), among 6/33 (18.18%) subjects. Based on the GAIS, 100% of subjects met the primary endpoint. Subject satisfaction was maximal at Month 1 (100%) and largely maintained at Month 8 (78.57%). Besides expected injection-related AEs (eg, ecchymosis, erythema), immediate AEs during/following treatment were limited to presyncopal symptoms [5/33 subjects (15.15%)]. Importantly, no cases of ischemia were observed. Subject-reported AEs (eg, swelling, erythema, pain) dissipated within 2 to 7 days. Conclusion: Given the technical nature of this technique, HA-L may be well-suited for injection rhinoplasty, due to its strong safety and efficacy profile. Level of Evidence: Level III: Evidence obtained from well-designed cohort study.

Hyaluronic High Definition Fill Technique

INTRODUCTION

Achieving a defined abdomen through traditional surgical methods like liposuction and abdominoplasty involves risks and significant downtime. Hyaluronic acid (HA) body filling has emerged as a minimally invasive alternative, offering immediate results with reduced recovery periods.

PATIENTS AND METHODS

The high-definition abdomen through HA technique (HHD) was implemented on young men with BMI < 24.9, excluding those with obesity or excessive skin laxity. HA gel with large particle sizes (800-1800 μm) and high G prime was chosen based on subcutaneous thickness. Injections were guided by ultrasound into the lamellar fat layer between Camper's fascia and Scarpa's fascia, targeting abdominal metameres for enhancement. Participants completed the Global Aesthetic Improvement Scale.

RESULTS

The technique produced satisfactory outcomes, enhancing abdominal metamere definition. Mild post-procedural hematomas and transient discomfort were noted. At 10 months, 71.4% of patients reported "much improved," and 28.6% reported "improved," per the GAIS questionnaire.

DISCUSSION

Customizing HA characteristics and employing ultrasound guidance ensured safe and precise injections, minimizing vascular risks. Limitations such as HA's temporary nature and exclusions for surgical candidates were acknowledged.

CONCLUSION

HHD using large particle HA proved effective in achieving aesthetic abdominal enhancements with minimal risks and downtime. This technique not only provided immediate results but also contributed to enhanced patient satisfaction and self-esteem. Further research is needed to explore broader applications and refine outcomes across diverse patient groups.

Safety and Performance of RHA4 in the Midface Using the Multilayering Technique: Preclinical and Clinical Evidence

Background

Resilient hyaluronic acid (RHA) fillers are used to treat dynamic wrinkles or provide tissue lifting in facial aesthetics. This study explored the biological, biomechanical, and clinical safety and performance of RHA4, a volumizing hyaluronic acid filler tailored for tissue support in dynamic facial areas, upon interaction with human subcutaneous adipose tissue (AT).

Methods

RHA4 underwent cytocompatibility testing with human fibroblasts and adipose stem cells. A 1-year rat in vivo implantation study tracked tissue integration, local effects, and filler degradation. Biomechanical tests assessed RHA4's impact on subcutaneous AT mechanics. Clinical outcomes, safety, injection volumes, and techniques were evaluated in 35 patients, treated in midface deep and superficial fat compartments via a multilayering methodology. Dynamic outcomes and 2-year follow-up of RHA4 in the midface using multilayer treatments were described.

Results

RHA4 demonstrated excellent biocompatibility and tissue integration both in vitro and in vivo, exhibiting minimal local inflammation and rapid collagen bundle formation within the filler. It integrated gradually over time and was well tolerated, allowing for increased extracellular matrix presence, neovascularization, denser collagen deposition, and AT growth. Ex vivo, RHA4 did not impede fat motion biomechanics but visibly lifted the tissue. Clinically, RHA4 proved safe and effective for lifting both deep and superficial fat compartments in the midface without affecting facial expressiveness.

Conclusions

Preclinical and clinical evidence confirmed that RHA4 is a versatile filler capable of lifting tissue efficiently, whether deep or superficial, particularly through the multilayering treatment approach. Importantly, RHA4 preserves AT biomechanics, adapts to the dynamism of the face, and ensures natural-looking outcomes.

Split-Face Comparison of Two Hyaluronic Acid Fillers: Intersection of Rheology and Tissue Behavior in Midface Rejuvenation

Background

Hyaluronic acid (HA) fillers are one of the most popular aesthetic treatments for midface volumization, achieving optimal aesthetic improvements. Given the variety of HA filler products available, it is important for injectors to understand how their rheological properties can influence behavior in tissues.

Objectives

To evaluate and compare (1) product integration and dynamic support and (2) lifting capacity of 2 rheologically different HA fillers (HA Contour [HACON] and HA Voluma [HAJVOL]) through ultrasound and clinical photography.

Methods

Randomized, split-face study (n = 11) comparing 2 midface HA fillers over a 12-month period with initial injection along the zygomatic arch at Day 0 and optional touch-up at Month 1. Eligible patients were aged 22 to 65 years with midface volume loss and contour deficiency. Assessments included ultrasound (neutral and smiling), clinical photography with 3D volume change (lifting capacity) analyses, and adverse event reporting. Volume change was assessed at 2 regions: midface and infraorbital hollow (IOH).

Results

With similar average total injection volumes, both fillers had comparable lifting capacity in the midface (HACON: ≥2.07 mL and HAJVOL: ≥2.08 mL; P > .05) and IOH (HACON: ≥0.45 mL and HAJVOL: ≥0.57 mL; P > .05) areas for up to 12 months. Ultrasound showed that HACON integrated into the tissue, stretching and elongating during a smiling expression, whereas HAJVOL did not integrate as much, with aggregates consistent in size and shape during both neutral and smiling expressions through 12 months. No adverse events were reported during the study.

Conclusions

HACON demonstrated a similar duration of lifting capacity (volumization) as HAJVOL but had more distributed product integration and flexibility to support dynamic expressions through 12 months.

Level of Evidence 3 Therapeutic

Analysis of Morphologic and Rheological Properties of Hyaluronic Acid Gel Fillers to Body Contouring and Its Clinical Correlation

The demand for minimally invasive body contouring procedures, particularly for gluteal augmentation, has grown significantly. This study evaluates the morphologic and rheological properties of four commercially available hyaluronic acid (HA) fillers used for body contouring and explores their clinical implications. Critical parameters such as storage modulus (G'), loss modulus (G″), complex modulus (G*), and damping factor (tan δ) were measured using oscillatory rheological tests to assess each filler's elasticity, viscosity, and viscoelastic profile. Scanning Electron Microscopy (SEM) was performed to analyze the microstructure of the fillers, providing insights into their microscopic architecture. The results showed differences in mechanical properties and viscoelastic behavior among the fillers. These variations suggest that the choice of filler may need to be tailored to specific body contouring requirements. Understanding these differences is crucial for achieving the best clinical results and patient satisfaction, helping professionals select the most suitable filler for each case.

Application of Hyaluronic Acid Linear Stereoscopic Stack Volume Enhancement Injection Technique in Nasal Reshaping

Hyaluronic acid (HA) injection, traditionally used for non-surgical rhinoplasty, is often associated with adverse effects such as increased nasal dorsum width. This study introduces the linear stereoscopic stack volume enhancement (LSSVE) injection technique as a solution for patients with low-profile noses, aiming to improve the nasal dorsum dimension, prevent long-term nasal widening, and address related concerns. A retrospective analysis was conducted on the clinical registry data of patients treated at Shanghai Phiskin Clinic from December 2020 to June 2024, who received HA injections using the LSSVE technique. Each rhinoplasty patient received a personalized injection, with doses ranging from 0.59 to 1.03 mL, adjusted based on specific characteristics of their nose and forehead. The procedure utilized a 25G blunt cannula to administer HA between the nasal bone periosteum and fascial layer using the LSSVE technique. The primary endpoint was patient improvement assessed 6 months post-injection using the Global Aesthetic Improvement Scale (GAIS), evaluated by a blinded assessor. In addition, patient satisfaction and complications were assessed. A total of 189 patients (181 females and 28 males) were included in the study, all of whom received a single HA LSSVE injection. Six months post-injection, the GAIS improvement rate was 82.83%, with a patient satisfaction rate of 84.83%. The injection effect was maintained for 6 months without any nasal dorsum widening, and a significant increase in the nasofrontal angle was observed (P<0.001). No long-term complications were reported post-injection. The LSSVE injection technique demonstrated effectiveness in overcoming the limitations of traditional HA rhinoplasty and preventing long-term nasal dorsum widening.

Comparative Trial Evaluating a High- Versus Low-Integration Hyaluronic Acid Filler for Contouring the Jawline

BACKGROUND

Contour deficits of the jawline are an area of concern for many aesthetic patients. While the use of hyaluronic acid (HA) for jawline enhancement has been described previously, comparative investigations of HA fillers manufactured with different technologies are limited. Therefore, the aim of the current investigation was to evaluate the safety and efficacy of Restylane Lyft (HA-L) and Restylane Defyne (HA-D) for contouring of the jawline.

METHODS

This prospective clinical trial enrolled forty (40) participants. Twenty (20) participants with thin skin were treated with HA-D, and twenty (20) participants with thick skin were treated with HA-L. Visits occurred at Screening/Baseline (treatment), Week 2 (touch-up), and Months 1, 3, and 6. At each visit, a blinded evaluator rated 3-dimensional participant imagery according to the Jawline Volume Loss Scale and participants completed the Jawline Subject Satisfaction Scale. Frequency of treatment-emergent adverse events was collected via participant diaries, and product integration characteristics were evaluated via ultrasound.

RESULTS

Chi-square tests of independence revealed statistically significant improvements in severities of jawline volume loss, which were maximal at Month 1 (100%) and maintained until Month 6 (82.05%). At Month 1, 92.10% of participants reported being satisfied with overall treatment effects. Adverse events were expected per the product monographs and did not vary per group. On ultrasound, HA-L displayed targeted product integration and HA-D displayed diffuse product integration.

CONCLUSIONS

Results support the use of HA-L and HA-D for the contouring of the jawline with each product capable of providing distinct advantages depending on patient attributes (e.g., skin thickness, underlying bone structure, desired outcomes).

LEVEL III

Evidence obtained from well-designed cohort or case-control analytic studies.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Jawline Sharp Contouring With Hybrid Filler

BACKGROUND

Having a well-defined jawline is a sign of youth and attractiveness among both men and women. Soft tissue fillers, such as calcium hydroxylapatite (CaHA) and hyaluronic acid (HA) fillers, offer nonsurgical alternatives for rejuvenating the lower face and enhancing the jawline. The aim of this study was to investigate the use of a premixed combination of HA with cohesive polydensified matrix technology (CPM, Belotero Intense, CPM-I) and CaHA to create a sharply defined jawline.

METHODS

A total of 126 patients were enrolled in the study and treated with a premixed combination of CPM-I and CaHA using a retrograde fanning injection technique with cannulas. The injection volumes and product ratios were customized according to the patients' needs.

RESULTS

The cohort consisted of 75 females and 51 males. The average injected volume of premixed CaHA:CPM-I was 5.83 mL. In the majority of patients, a 1:1 syringe ratio of CaHA:CPM-I was applied (n = 81, 64.2%). No adverse events were reported during the 6-month follow-up period.

CONCLUSION

The hybrid filler approach investigated in this study shows promise for achieving well-defined, long-lasting jawline contours.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266 .

Comparative in-vitro degradation of hyaluronic acids exposed to different hyaluronidase enzymes

Objectives

This study aimed to compare the in-vitro behavior of four Hyaluronic acid (HA) gels when exposed to two different hyaluronidase (HSE) formulations.

Methods

Four commercially available HA were used: Lyft (Lt; Restylane, Galderma, Sweden), Voluma (Vol; Allergan, AbbVie, USA), UltraDeep (UDe; Rennova, Innovapharma, Brazil), and Subskin (Skn; Perfectha, Sinclair, France). The gels were divided into two groups, with seven aliquots (0.1 mL per aliquot) for each group deposited on a glass plate. A millimeter ruler was positioned behind the plate to measure the gel height. Each aliquot received 100 UTR of one of two HSE formulations. After 2 min, each aliquot was mixed using a 22G needle and left to sit for additional 2 min.

Results

Partial and final degradation of the products were obtained through photographic analysis. The final percentage of degradation exhibited significant differences among HA gels (P < 0.001). The results revealed higher degradation in Lt, moderate degradation in UDe, and lower degradation in Vol and Skn. Comparisons of HSE formulations showed no significant differences among them (P = 0.881). Moreover, there was a noticeable degradation after mixing (P < 0.001).

Conclusions

Within the limits of this study, it can be suggested that Lt exhibits the higher degradation among the experimented gels. Furthermore, differences among HSE formulations do not appear to significantly impact HA degradation, while the mixing movement of HSE and HA seems to influence the degradation rate. These findings may help guide clinical decisions regarding the use of hyaluronidase in managing HA filler complications or adjustments.

Good scientific practice of using worldwide post-marketing surveillance data to ensure safety with HAALI BDDE cross-linked hyaluronic acid fillers

Background

Aliaxin fillers (HAALI), produced by IBSA Farmaceutici Italia SrL (Italy), are biodegradable, non-pyrogenic, 1,4-butanediol diglycidyl ether cross-linked hyaluronic acid (HA) hydrogels. The formulations are tailored for different clinical indications, ensuring precise and natural outcomes. Their cohesivity and tissue integration capabilities are associated with relatively few adverse events (AEs), supporting their widespread use in aesthetic treatments. This article examines the real-world safety profile of HAALI fillers derived from worldwide post-marketing surveillance data.

Methods

Post-marketing surveillance was registered by the manufacturer from January 2018 to September 2023. During this period, product complaints were globally gathered from healthcare practitioners and consumers, relating to technical issues or safety and product-related adverse events.

Results

No discernible trend or substantial escalation in AEs across the entire product range were observed during the surveillance period (p>0.05). No statistically significant increases (p>0.05) in the frequency or severity of safety incidents and AEs were observed. The most frequently observed AEs were oedema (26%) and swelling (19%).

Conclusion

The analysed data further support and confirm the high safety profile of the HAALI fillers for different approaches in aesthetic medicine. This evaluation also highlights the importance of post-marketing analysis by continuing to foster a robust understanding of products currently used in daily clinical practice.

Jowl Improvement With Injectable Fillers: Jawline Injections Alone Versus Jawline and Cheek Injections

BACKGROUND

Jowling is a common aesthetic complaint in aging individuals.

OBJECTIVE

Injectable filler placed at the lateral jawline will improve the appearance of jowls, as defined by the Merz Aesthetic Jawline Grading Scale (MAJGS). This improvement will be independent of concomitant injection of filler into the lateral cheek.

METHODS

Fifteen female subjects with grade 2 to 3 jowls on a scale of 0 to 4 were enrolled to receive either VYC-20L in the mandibular angle/ramus (Group 1) or the mandibular angle/ramus and lateral cheek (Group 2). The subjects were evaluated by a blinded cosmetic dermatologist and themselves at 4 weeks after the last injection.

RESULTS

A statistically significant improvement was noted in Group 1 by all blinded reviewers and subjects. Group 2 did not reach statistical significance as evaluated by the blinded dermatologist although did by the subject's rating. The average amount of filler injected per subject was 3.36 mL for group 1 and 8.38 mL for group 2. A novel adverse event was tenderness when chewing lasting for 2 to 3 days.

CONCLUSION

Injection of VYC-20L showed statistical improvement in a validated jowl scale when injected at the angle of the mandible and the mandibular ramus, independent of concomitant lateral cheek injections.

Comparative analysis of in vivo bio-integration of three hyaluronic acid-based fillers for 26 weeks: a histological study

Stabilized hyaluronic acid (HA), produced through diverse cross-linking technology and formulated as an injectable gel, has found widespread utilization in aesthetic industry. Cross-linked HA essentially constitutes a gel particle composition formed by numerous viscoelastic particulates. Various product formulations yield HA gels with distinct properties, including particle size, viscoelasticity, and interaction forces between particles. While previous studies have primarily concentrated on the biological safety and macroscopic expression of fillers, limited research exists on the internal mechanisms governing their macro-performance. This study selected three common dermal fillers for analysis, establishing an animal model to assess their in vivo interaction with surrounding tissues and explore their internal mechanisms. The findings revealed that particle size plays a crucial role in tissue integration.

Methods for determining the structure and physicochemical properties of hyaluronic acid and its derivatives: A review

Hyaluronic acid (HA) is a linear high molecular weight polymer ubiquitously distributed in humans and animals. The D-glucuronic acid and N-acetyl-D-glucosamine repeating disaccharide backbone along with variable secondary and tertiary structures endows HA with unique rheological characteristics as well as diverse biological functions such as maintaining tissue homeostasis and mediating cell functions. Due to its excellent biocompatibility, biodegradability, viscoelasticity and moisturizing properties, natural HA and its chemically modified derivatives are widely used in medical, pharmaceutical, food and cosmetic industries. For broad application purposes, abundant HA-based biochemical products have been developed, including the methodologies for characterization of these products. This review provides an overview focusing on the methods used for determining HA structure as well as the strategies for constructing its derivatives. Apart from the analytical approaches for defining the physicochemical properties of HA (e.g., molecular weight, rheology and swelling capacity), quantitative methods for assessing the purity of HA-based materials are discussed. In addition, the biological functions and potential applications of HA and its derivatives are briefly embarked and perspectives in methodological development are discussed.

Preparation and Rheological Evaluation of Thiol-Maleimide/Thiol-Thiol Double Self-Crosslinking Hyaluronic Acid-Based Hydrogels as Dermal Fillers for Aesthetic Medicine

This study presents the development of thiol-maleimide/thiol-thiol double self-crosslinking hyaluronic acid-based (dscHA) hydrogels for use as dermal fillers. Hyaluronic acid with varying degrees of maleimide substitution (10%, 20%, and 30%) was synthesized and characterized, and dscHA hydrogels were fabricated using two molecular weights of four-arm polyethylene glycol (PEG10K/20K)-thiol as crosslinkers. The six resulting dscHA hydrogels demonstrated solid-like behavior with distinct physical and rheological properties. SEM analysis revealed a decrease in porosity with higher crosslinker MW and maleimide substitution. The swelling ratios of the six hydrogels reached equilibrium at approximately 1 h and ranged from 20% to 35%, indicating relatively low swelling. Degradation rates decreased with increasing maleimide substitution, while crosslinker MW had little effect. Higher maleimide substitution also required greater injection force. Elastic modulus (G') in the linear viscoelastic region increased with maleimide substitution and crosslinker MW, indicating enhanced firmness. All hydrogels displayed similar creep-recovery behavior, showing instantaneous deformation under constant stress. Alternate-step strain tests indicated that all six dscHA hydrogels could maintain elasticity, allowing them to integrate with the surrounding tissue via viscous deformation caused by the stress exerted by changes in facial expression. Ultimately, the connection between the clinical performance of the obtained dscHA hydrogels used as dermal filler and their physicochemical and rheological properties was discussed to aid clinicians in the selection of the most appropriate hydrogel for facial rejuvenation. While these findings are promising, further studies are required to assess irritation, toxicity, and in vivo degradation before clinical use. Overall, it was concluded that all six dscHA hydrogels show promise as dermal fillers for various facial regions.

Does cannula's size alter rheological properties of hyaluronic acid filler?

This study evaluated the rheological properties of various hyaluronic acid (HA) gels after passing through different-sized cannulas (22-G and 25-G). Five commercial brands of highly crosslinked HA fillers were analyzed: (A) Rennova® Ultra Deep, (B) Restylane® Lyft, (C) Hialurox® - Ultra Lift, (D) Belotero® Volume, and (E) E.P.T.Q S500. Rheological characterization was conducted using an automated controlled stress rheometer. The rheological properties of the fillers were assessed both before and after passing through the cannulas. Each filler brand and cannula size was tested three times by a researcher who was blinded to the commercial brands. For data analysis, frequencies of 0.1, 0.5, and 2 Hz were employed. The rheological properties (storage modulus [G'] and loss modulus [G"]) of the high-crosslink HA fillers did not change after being passed through cannulas of different sizes (22-G and 25-G) (p > 0.109) compared to baseline measurements (no cannula). Furthermore, all fillers displayed desirable solid-like, volumizing behavior at low frequencies and strain amplitudes (<10 %). Under physiologically relevant conditions for skin and facial applications, the cannula size did not alter the rheological properties of high crosslink HA fillers.

A Prospective, Randomized, Double-Blind, Split-Face, Comparative Study to Evaluate the Efficacy and Safety of DKL23 and Juvéderm Volift for Correcting Moderate-to-Severe Nasolabial Folds

BACKGROUND

Hyaluronic acid dermal fillers are used for multiple indications, including wrinkle correction and restoration of volume/fullness.

OBJECTIVES

The aim of this study was to compare the efficacy and safety of 2 hyaluronic acid products for correcting moderate to severe nasolabial folds (NLFs).

METHODS

A prospective, randomized, double-blind, split-face study was undertaken. The subjects' left and right NLFs were randomly allocated for treatment with DKL23 or Juvéderm Volift. Follow-up was conducted at 1, 3, 6, and 9 months. The changes from baseline on the Wrinkle Severity Rating Scale and the Global Aesthetics Improvement Scale were evaluated. Posttreatment adverse events (AEs) were recorded.

RESULTS

Forty-eight women (median age, 57.0 years) with Type I to VI skin were enrolled. Both treatments showed statistically significant improvement (P < .0001) in NLFs according to the Wrinkle Severity Rating Scale score from baseline to each of the time points assessed. The improvement in NLFs was maintained until the end of the study (9 months). Furthermore, the change from baseline to each of the time points assessed was similar between DKL23 and Juvéderm Volift. Investigator- and subject-rated Global Aesthetics Improvement Scale scores showed similar rates of improvement (indicated by the sum of responses of improved, much improved, or very much improved) between the 2 products. The AEs reported in the study were in line with previous and expected experience after injection of hyaluronic acid dermal fillers. The types of AEs, their rates, intensity, and duration were comparable between the 2 products.

CONCLUSIONS

DKL23 improved NLF severity from baseline and for up to 9 months, and the results were comparable to the improvement shown by Juvéderm Volift. Treatment was safe and well tolerated.

LEVEL OF EVIDENCE: 2

Post-Treatment Displacement of Facial Soft Tissue Fillers-A Retrospective Ultrasound-based Investigation of 382 Zygomatic Regions

BACKGROUND

Clinical and ultrasound experience has revealed that after soft tissue injections of the lateral cheek, the filler may displace from the zygoma to the caudal temporal area.

OBJECTIVE

To obtain more data to provide insight into product distribution when soft tissue fillers are injected in the zygomatic region.

METHODS

Two hundred patients were examined with facial ultrasound imaging of the zygomatic and temporal region. Inclusion criteria were simply a positive response on the screening questionnaire as to whether or not they had filler injections placed in their lateral cheek. Control injections were also performed to the zygomatic regions of a body donor and in 10 patients ultrasound-guided.

RESULTS

A correlation was found between the layers in which filler was detected on the zygoma and where it was ultimately found in the temples. Four different redistribution patterns were observed: (1) migration of filler within the superficial muscular aponeurotic system (SMAS) on the zygoma into the superficial temporal fascia. Migration of filler from the lateral suborbicularis oculi fat to (2) the deep interfacial plane of the temple or (3) to the superficial temporal fat pad; (4) migration from the supraperiosteal layer of the zygoma to the superficial temporal fat pad. Body donor and patients: filler deposits injected on the zygoma were witnessed to shift during injection into the caudal part of the temple.

CONCLUSION

Soft tissue filler aliquots may be redistributed into the temples after injections of the lateral side of the zygomatic arch. The displacement follows a distinct pattern depending on the initial layer of injection.

Analysis of the Morphology, Rheology, and Clinical Applicability of a Hybrid Injectable with Hyaluronic Acid and Hydroxyapatite

BACKGROUND

Treating signs of aging requires skeletal restructuring, facial contour redefinition, and sagging skin treatment. Hence, HarmonyCa® was recently introduced in the market, combining hyaluronic acid and hydroxyapatite. However, there are no studies evaluating the physicochemical properties of this material.

PURPOSE

To analyze the morphology, rheology, and clinical applicability of HarmonyCa® over a 180-day follow-up.

METHODS

A morphological analysis with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) and rheology measurement with a rheometer. The clinical applicability analysis included a tissue ptosis patient who received the product and was reassessed 30 and 180 days after applying HarmonyCa®.

RESULTS

SEM and EDS analyses showed two distinct morphologies related to hydroxyapatite and hyaluronic acid. The rheological measurements of HarmonyCa® showed G' and G″ of 51.56 and 44.01 Pa, respectively. The tan δ value was 0.8503, and G* was 108.1 Pa. The clinical outcomes were satisfactory.

CONCLUSION

HarmonyCa® presents a good synergy between hyaluronic acid and hydroxyapatite. Also, the rheological analysis showed moderate viscosity for the product, with a clinical indication for subcutaneous application.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Comparative Rheology of Hyaluronic Acid Fillers, Poly-l-lactic Acid, and Varying Dilutions of Calcium Hydroxylapatite

Background

This study examines the rheological properties of various dermal fillers, including hyaluronic acid (HA) fillers, poly-L-lactic acid (PLLA), and calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) gels, with a particular focus on the impact of aqueous dilution on CaHA-CMC's rheology and potential clinical implications.

Methods

Using standardized rheological analysis, we measured and compared the elastic modulus (G'), viscous modulus (G″), and the tan δ values of different dilutions of CaHA-CMC against published values of HA and PLLA fillers. The study aimed to determine the potential clinical use of application-specific CaHA-CMC hydrogel dilutions along a range of gel strength and cohesion for hydrogel fillers in current use.

Results

The findings demonstrate that CaHA-CMC's rheological properties can be tailored across a broad spectrum of viscoelastic parameters through titrated dilution, ranging from high elasticity to low cohesion. Varying the aqueous volume allows for the rheomodulation of CaHA-CMC, potentially matching the entire rheological spectrum of HA fillers and suggesting an expanded range of clinical applications.

Conclusions

The versatility of CaHA-CMC through dilution may offer a customizable approach for clinical applications, providing practitioners with the ability to fine-tune the properties of fillers to meet specific patient needs and treatment goals. This study lays the groundwork for the potential future use of filler dilutional rheomodulation in clinical practice, tailored to patient- and application-specific needs.

Long-term 23-year Global Post-marketing Safety Surveillance Review of Delayed Complications with a Supportive Hyaluronic Acid Filler for Infraorbital Hollow Rejuvenation

HARES is a supportive (high G') HA filler with a low degree of water affinity (gel swelling) and modification (<1% BDDE) that has a well-established safety and efficacy profile in the literature, especially for infraorbital hollow (IOH) rejuvenation. To further support the safety of this product, a long-term review of delayed-onset adverse events of interest (DAEIs) related to HARES was conducted using reports from a global post-marketing safety surveillance database over the past 23 years. This review demonstrated low reporting frequencies of delayed-onset nodules and inflammatory events, establishing a long-term safety profile for HARES that supports its continued use in clinical practice, especially for IOH rejuvenation.

In Vitro Cytocompatibility Analysis and Comparison of Different Hyaluronic Acid Fillers for Minimally Invasive Esthetics

BACKGROUND/AIM

To overcome the natural visual consequences of the physiological aging process, the use of biodegradable fillers made of hyaluronic acid or sodium carboxymethyl cellulose is increasingly popular in modern esthetic medicine. Clinicians can choose from a wide range of fillers with variable compositions and rheological properties, and therefore with different application areas and injection depths. The aim of this study was to analyze and compare the most commonly used fillers for facial augmentation regarding their in vitro biocompatibility and to find potential correlations to their rheological properties.

MATERIALS AND METHODS

In the present study, direct and indirect in vitro cytotoxicity analysis according to DIN EN ISO 10993-5 were performed on 39 different filler materials for facial augmentation.

RESULTS

All fillers analyzed in this study overall showed satisfactory results in the direct and indirect cytocompatibility tests. While no material was outside the threshold values in the 2,3-bis-(2-methoxy-4-nitro-5-sulphenyl)-(2H)-tetrazolium-5-carboxanilide (XTT) cell viability and bromodeoxyuridine (BrdU) cell proliferation assays or in the live-dead staining, only 7 out of the 39 fillers reached the required values in the lactate dehydrogenase assay.

CONCLUSION

All biodegradable fillers examined in this study were found to be sufficiently cytocompatible. Although the qualitative analysis of the test results showed differences between the fillers, no concrete correlation between test performance and composition or manufacturer of the fillers was found. Future efforts are required to provide clinicians with even better support in choosing the right filler for optimal outcome and patient satisfaction.

Low Molecular Weight Hyaluronic Acid Added to Six Specific Amino Acids in the Treatment of Striae Alba (SA): An Observational Study

Striae distensae or stretch marks are a common complaint among women and can be distressing. The present study aimed to assess the efficacy of a mixture of low molecular weight hyaluronic acid and six amino acids when applied with a specific intradermal injection technique known as intra-mural fluid technique. A clinical study was carried out in 32 patients (with a dropout rate by 9.4%) with striae distensae alba (SA) in one or more of the following anatomical areas: breast, abdomen, inner thigh, trochanteric area, gluteal area, posterior supra-iliac area, and lumbar area. Product efficacy was assessed by the investigator using the Global Aesthetic Improvement Scale, while a Likert scale was used to evaluate to score the treatment tolerability and a QoL stretch marks questionnaire was used to investigate the patients' self-body image. The treatment was effective in improving the appearance of SA fifteen days after the second treatment and 6 months after the first treatment (and after a total of 4 treatments). The product efficacy and tolerability were also perceived by the patients during each treatment session. Our results suggest that the test treatment is a valid treatment option to decrease the appearance of SA. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/00266.

Intracorporeal evaluation of hyaluronic acid fillers with varied rheological properties and correlations with aesthetic outcomes

BACKGROUND

Understanding the differences in soft tissue filler rheology and how these properties can impact clinical results is a fundamental concepts for any injector. This study aimed to assess the tissue integration characteristics of hyaluronic acid (HA) fillers manufactured with different technologies (Non-Animal Stabilized HA [HA-N] or Optimal Balance Technology [HA-O]) using ultra-high-frequency ultrasound.

METHODS

Twelve female participants with mild-to-moderate midface volume loss and temporal hollowing were enrolled and treated with HA-N and/or HA-O. Participants were seen at five visits (screening/baseline [treatment], and Weeks 1 [optional touch-up], 4, 6, and 8 [follow-up visits]). Ultrasound was used to evaluate the degree of product integration.

RESULTS

On ultrasound, HA-N presented with distinct borders, minimal tissue integration, and a capacity to displace tissues. Conversely, HA-O tended to spread horizontally within the same tissue plane and integrated within tissues. The volumizing capacity of the HA-O fillers was dependent on particle size.

CONCLUSION

HA-N is suited for deep injections in areas such as the upper lateral cheek and under the muscle of the temporal region when a lifting effect is desired; HA-O is best suited for subcutaneous injections, in areas of dynamic movement or for patients with thin skin; and can be injected subcutaneously or supraperiosteally when a volumizing effect is desired.

Dilutional rheology of Radiesse: Implications for regeneration and vascular safety

BACKGROUND

Calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) injectables have emerged as dual-purpose fillers with bioregenerative and direct filling capabilities.

AIMS

This study investigates the rheological properties of CaHA-CMC and its CMC carrier gel at various dilutions.

METHODS

The storage modulus (G'), loss modulus (G″), complex viscosity (η*), loss factor (tan δ), cohesivity, and extrusion force were evaluated for a range of CaHA-CMC aqueous dilutions with an oscillatory rheometer, drop weight testing, and force analysis, respectively.

RESULTS

Results revealed a significant decrease in G', η*, and increase in tan(δ) with increasing dilution, indicating a decline in the product's direct filling capabilities. Cohesivity decreased dramatically with dilution, potentially enhancing tissue biointegration and the product's biostimulatory effects. The CMC gel carrier displayed inelastic and non-resilient properties, with rheological changes differing from CaHA-CMC. Dilutional rheology was also correlated with previously published dilution-dependent biostimulatory data where hyperdiluted CaHA-CMC (>1:2) demonstrated a regenerative profile and diluted or hypodiluted mixtures retained meaningful filling properties and increased regeneration.

CONCLUSIONS

These findings offer a continuum for tailoring the product's rheological profile to match specific tissue requirements. Customizable rheology allows CaHA-CMC to be tuned for either filling and contouring or optimal regenerative effects. Importantly, safety implications related to vascular occlusion suggest that dilutional rheomodulation decreases the risk of vascular events. In conclusion, this study highlights the significant impact of aqueous dilution on the rheological properties of CaHA-CMC and its carrier gel. The findings support the clinical application of tailored dilutions to achieve desired outcomes, providing versatility and safety for aesthetic applications.

The rheology of injectable hyaluronic acid hydrogels used as facial fillers: A review

Injectable hyaluronic acid (HA) hydrogels have been popularized in facial aesthetics as they provide a long-lasting effect, low risk of complications, allergenicity tests are not required before application and can be easily removed by the action of hyaluronidases. On the other hand, the development of these systems requires in-depth studies of chemical mechanisms involved in hydrogel formation. Ideal dermal fillers should temporarily fluidize during extrusion through the needle and quickly recover their original shape after application. Hydrogels with more elastic properties, for example, are difficult to inject while viscous materials are too liquid. A balance between both properties should be achieved. Each region of the face requires products with distinct rheological properties. High G' dermal fillers are preferable for deeper wrinkles whereas the counterpart with lower values of G' is more indicated in superficial wrinkles or lip augmentation. Factors such as molecular weight and concentration of HA, pH, type and concentration of the crosslinking agent, particle size, crosslinking reaction time and crosslinking agent/polysaccharide ratio should be modulated to achieve specific rheological properties. In this review, the effect of each variable is discussed in detail to guide the rational development of new dermal fillers.

Nonsurgical Gluteal Volume Correction with Hyaluronic Acid: A Retrospective Study to Assess Long-term Safety and Efficacy

Background

Augmentation and reshaping of body volume, particularly in the gluteal area, presents a significant challenge in aesthetic surgery. Hyaluronic acid (HA) fillers have emerged as an effective and safe tool for such indications, but literature examining nonsurgical gluteal reshaping with HA remains limited. This study aims to evaluate the long-term safety of using recommended volumes of HA body fillers for nonsurgical gluteal augmentation.

Methods

A retrospective, observational study was carried out across multiple centers in Italy and the United Arab Emirates. The study involved participants between 22 and 53 years of age who underwent gluteal augmentation using HA body filler (HYAcorp MLF1/2) between 2017 and 2021, with up to 4 years and 7 months of follow-up. Participants and investigators independently evaluated the procedure's effectiveness by comparing pre- and posttreatment photographs. The Global Aesthetic Improvement Scale was used to assess posttreatment satisfaction by both participants and investigators. All adverse effects (AEs) were recorded.

Results

The study included a diverse group of 91 participants. No serious adverse events were reported, with the majority of AE occurring shortly after treatment and resolving in 1 week. AEs were more frequently observed in participants with previous treatments using different substances in the treatment area.

Conclusions

The real-world application of HA body filler (HYAcorp MLF1/2) for gluteal augmentation in the participants of this study showed the treatment's effectiveness, with no severe adverse events reported among the participants. High levels of satisfaction were reported among both participants and investigators.

Comprehensive Evaluation of Injectability Attributes in OxiFree™ Dermal Fillers: MaiLi® Product Variants and Clinical Case Reports

Dermal filler injectability is a critical factor for commercial product adoption by medical aesthetic professionals and for successful clinical administration. We have previously reported (in vitro and ex vivo) cross-linked hyaluronic acid (HA)-based dermal filler benchmarking in terms of manual and automated injectability requirements. To further enhance the function-oriented product characterization workflows and the clinical relevance of dermal filler injectability assessments, the aim of this study was to perform in vivo evaluations. Therefore, several variants of the MaiLi® product range (OxiFree™ technology) were characterized in vitro and in vivo in terms of injectability attributes, with a focus on hydrogel system homogeneity and ease of injection. Firstly, standardized in vitro assays were performed in SimSkin® cutaneous equivalents, with variations of the clinical injector, injection site, and injection technique. Then, automated injections in SimSkin® cutaneous equivalents were comparatively performed in a texture analysis setup to obtain fine-granulometry injection force profile results. Finally, five female participants were recruited for the in vivo arm of the study (case reports), with variations of the clinical injector, injection site, and injection technique. Generally, the obtained quantitative force values and injection force profiles were critically appraised from a translational viewpoint, based on discussions around the OxiFree™ manufacturing technology and on in-use specialized clinician feedback. Overall, the present study outlined a notable level of homogeneity across the MaiLi® product range in terms of injectability attributes, as well as consistently high ease of administration by medical aesthetic clinicians.

An injectable gel based on photo-cross-linkable hyaluronic acid and mesoporous bioactive glass nanoparticles for periodontitis treatment

Guided bone regeneration (GBR) is an effective strategy to promote periodontal tissue repair. The current study aimed to develop an injectable gel for GBR, composed of photo-cross-linkable hyaluronic acid and mesoporous bioactive glass nanoparticles (MBGNs) loaded with antibacterial minocycline hydrochloride (MNCl). Hyaluronic acid modified with methacrylic anhydride (MHA) that could be cross-linked under UV irradiation was first synthesized. Dynamic rheological evaluation of MHA under UV was carried out to determine its in-situ gelling feasibility and stability. Morphological and mechanical characterization was performed to determine the optimal concentration of MHA gels. Sol-gel derived MBGNs loaded with MNCl were further incorporated into MHA gels to obtain the injectable drug-loaded MBGN-MNCl/MHA gels. In vitro antibacterial, anti-inflammatory and osteogenic effects of this gel were evaluated. It was shown that the MHA gel obtained from 3 % MHA under UV treatment of 30s exhibited a suitable porous structure with a compressive strength of 100 kPa. MBGNs with particle size of ∼120 nm and mesopores were confirmed by TEM and SEM. MBGNs had a loading capacity of ∼120 mg/g for MNCl, exhibiting a sustained release behavior. The MBGN-MNCl/MHA gel was shown to effectively inhibit the proliferation of Streptococcus mutans and the expression of pro-inflammatory factors IL-6 and TNF-α by macrophages. It could on the other hand significantly promote the expression of osteogenic-related genes ALP, Runx2, OPN, and osterix of MC3T3-E1 cells. In conclusion, the current design using photo-crosslinkable MHA gel embedded with MNCl loaded MBGNs can serve as a promising injectable formulation for GBR treatment of irregular periodontal defects.

The Efficacy and Safety of Hyaluronic Acid Injection in Tear Trough Deformity: A Systematic Review and Meta-analysis

BACKGROUND

Hyaluronic acid (HA) injection is an effective method to correct tear trough deformity. Nevertheless, the quantitative data of cosmetic results and complications of HA injection in tear troughs remained unemployed. The purpose of this meta-analysis was to synthesize the current quantitative data on the aesthetic outcomes and adverse effects of tear trough deformity correction with HA injection.

METHODS

This meta-analysis consulted PubMed, Embase, Web of Science, Scopus and Cochrane databases based on the search terms published before September 2022. Data extracted was analyzed to evaluate the satisfaction rates and complications of HA injection. Meta-analysis was performed using the random-effect model for overall and subgroup analysis.

RESULTS

This meta-analysis comprised 31 reports involving 2556 participants. The pooled overall satisfaction rate was 91.0% (95% CI 84.9-95.7%). The pooled rates of swelling/edema and bruising/ecchymosis were 19.2% (95% CI 10.4-29.9%) and 18.4% (95% CI 10.1-28.4%), respectively. The pooled rates of redness/erythema, contour irregularity/lump and blue discoloration/Tyndall effect were 7.1% (95% CI 1.5-15.6%), 5.3% (95% CI 1.8-10.2%) and 0.9% (95% CI 0.0-2.5%), respectively.

CONCLUSIONS

The present meta-analysis manifested a low risk of complication rate and a high satisfaction rate in tear trough rejuvenation with HA injection.

LEVEL OF EVIDENCE I

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Clinical Perspectives on the Injectability of Cross-Linked Hyaluronic Acid Dermal Fillers: A Standardized Methodology for Commercial Product Benchmarking with Inter-Injector Assessments

The injectability of cross-linked hyaluronic acid (HA) dermal fillers is influenced by polymer concentration, polymer cross-linking type and degree, the presence of lidocaine or other functional excipients, types of syringes, and injection techniques. Finished product injectability constitutes a critical quality attribute for clinical injectors, as it strongly influences product applicability and ease of use in aesthetic medicine. While injectable product extrusion force specifications are provided by the respective device manufacturers, the qualitative informative value of such datasets is low for injectors wishing to compare product brands and technologies from an injectability standpoint. Therefore, the present study comparatively assessed 28 cross-linked HA dermal fillers (JUVÉDERM®, Restylane®, BELOTERO®, TEOSYAL RHA®, and STYLAGE® brands) using various injectability benchmarking setups for enhanced clinical-oriented relevance. Manual product injections were performed by three specialized and experienced clinicians, whereas automatic product extrusion was performed using a Texture Analyzer instrument. The various hydrogel products were injected into ex vivo human skin and into SimSkin® cutaneous equivalents to appropriately account for injection-related counterpressure. The injectability results revealed important variability between and within product brands, with a strong influence of the local anesthetic lidocaine, HA contents, and needle gauge size. Critical appraisals of the investigated products were performed, notably from manufacturing process-based and clinical ease of application-based standpoints, centered on respective experimental injectability quality levels. Generally, it was confirmed that each HA-based dermal filler product requires specific expertise for optimal injection, mainly due to differing viscoelastic characteristics and injectability attributes. Overall, the present study set forth evidence-based and clinical-oriented rationale elements confirming the importance for injectors to work with injectable products with which they are experienced and comfortable to optimize clinical results.

Comparison of 2 Fillers for Lip Injection-A Randomized-Controlled Clinical Trial Assessed by 3D Imaging

Background

Lip aging is a concern for many, and hyaluronic acid (HA) injections are a popular solution.

Objectives

This study compared 2 different HA gel technologies (OBT and NASHA) for lip augmentation in 20 volunteers.

Methods

Both groups received treatment from the same injector using the same method. Lip volume was measured with a 3D stereophotogrammetry device before, immediately after, and 30 days posttreatment. Patient satisfaction and adverse events were assessed through FACE-Q scales analysis.

Results

The NASHA group showed an immediate volume increase (P = .01), which decreased after 30 days. The OBT group did not show a significant immediate growth (P = .535) but did exhibit a significant increase after 30 days (P = .014). After 30 days, there were no significant volume differences between the groups (P = .802 and P = .999). FACE-Q analysis revealed no significant differences among groups after 30 days.

Conclusions

This study highlights that less cohesive gels may modify faster in dynamic lip areas, emphasizing the importance of selecting products based on their physicochemical and rheological properties. In the context of lip augmentation with HA, it is important not to consider immediate aesthetic changes as definitive results, as volume changes may persist and develop over time after the treatment.

Level of Evidence 2

Evaluation of the Hydrophilic, Cohesive, and Physical Properties of Eight Hyaluronic Acid Fillers: Clinical Implications of Gel Differentiation

Background

Hyaluronic acid (HA) fillers are used to treat an array of aesthetic indications. Proper filler selection is paramount for successful patient outcomes. However, many important physiochemical and physical properties that impact HA gel behavior remain undefined.

Purpose

To evaluate the hydrophilicity, cohesivity and particle size of eight commercial HA fillers manufactured by either Non-Animal Stabilized Hyaluronic Acid (NASHA) or Optimal Balance Technology (OBT) techniques.

Methods and Materials

Three individual in vitro experiments were performed to assess HA swelling capacity, cohesion, and particle size. Image analyses, blinded evaluation using the Gavard-Sundaram Cohesivity Scale, and laser diffraction technology were utilized, respectively.

Results

Compared to fillers manufactured with NASHA technology, OBT products demonstrated greater swelling capacity, cohesion, and wider particle size distributions. Strong positive correlations between swelling factor, degree of cohesivity, and increasing widths of the particle size distributions were observed.

Conclusions

The hydrophilicity, cohesivity and particle size distributions vary among HA fillers manufactured with different techniques. The creation of new labels identifying products based on their unique combination of physiochemical and physical characteristics may help guide appropriate selection of HA fillers to optimize patient outcomes.

Comparative In Vivo Study of Solid-Type Pure Hyaluronic Acid in Thread Form: Safety and Efficacy Compared to Hyaluronic Acid Filler and Polydioxanone Threads

INTRODUCTION

Although various products are commonly used for skin rejuvenation, solid-type hyaluronic acid (HA) as an injectable form has not been researched or utilized. This study aimed to demonstrate the safety and efficacy of solid-type HA in thread form, which differs from the conventional gel-type HA commonly used.

METHOD

Solid-type HA threads, conventional HA fillers, and polydioxanone (PDO) threads were inserted into the dorsal subcutaneous layer of mice. Photographs were taken on days 0, 1, 3, and 7, and on day 7, the samples were harvested for histological analysis. Inflammatory reactions and detection of collagen were confirmed through tissue staining, and real-time PCR was conducted to quantify collagen synthesis.

RESULTS

In the histological analysis, the PDO threads exhibited a greater inflammatory response compared to the HA threads. Masson's trichrome staining revealed a higher degree of collagen synthesis in the HA thread group compared to the HA filler group. While collagen type 1 expression was significantly higher in the PDO thread group than in the HA thread group, the HA thread group showed higher expression levels of collagen type 3. Furthermore, the PDO thread group demonstrated a statistically significant increase in TGF-β1 compared to the HA group.

CONCLUSION

This in vivo study demonstrated the stable application of solid-type pure HA threads and their potential for inducing collagen production, while also yielding a low inflammatory response. The findings highlight the promising applications of solid-type HA in the field of cosmetic dermatology.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

"Cohesiveness of Hyaluronic Acid Fillers": Evaluation Using Multiple Cohesion Tests

Background  Hyaluronic acid fillers can be manufactured using various processes. They have multiple properties, including their concentration, degree of modification, and rheological data. Cohesion is one such property to evaluate gel integrity; however, there is no standardized method for calculating this parameter. This study aimed to evaluate different tests for calculating hyaluronic acid cohesion and discuss the importance of hyaluronic acid cohesion as a consideration when selecting fillers. Methods  The cohesion levels of five different hyaluronic acid fillers with different rheological properties were evaluated and compared using the drop weight, compression, tack, and dispersion time tests. Results  The cohesion tests yielded different results in the samples. Samples 2 and 4 showed approximately two times the number of droplets when compared with Sample 5 in drop weight test. Samples 1, 2, 3, and 4 were superior to Sample 5 in tack test. Samples 1, 2, and 3 showed cohesive appearances at 95 seconds in most cases in dispersion test. Rheological test results did not reflect the measures of cohesion. Conclusion  Although there are no definite standardized tests to evaluate the cohesion of hyaluronic acid fillers, our proposed tests showed similar results for different hyaluronic acid filler products. Further studies are needed to evaluate the cohesion of hyaluronic acid fillers and determine the clinical use of this distinguishing characteristic for clinicians selecting the product of choice. Level of evidence statement: These data are Level IV evidence.

Response of 21 Hyaluronic Acid Fillers to Recombinant Human Hyaluronidase

Background

One benefit of hyaluronic acid fillers is the ability to dissolve them using hyaluronidase. With the increasing number of fillers entering the market, it is crucial to understand each of these fillers' responsiveness to hyaluronidase.

Methods

Twenty-one hyaluronic acid fillers of 0.2 mL aliquots each were placed on slides. Twenty units of recombinant human hyaluronidase were injected into the aliquots every 30 minutes for a total of 120 units recombinant human hyaluronidase injected over 3 hours. With each injection, videos and photographs were taken from bird's eye and lateral views to measure aliquot height. Stirring videos were graded by three oculoplastic surgeons, and these grades were used to categorize each filler's responsiveness.

Results

Restylane Lyft, Restylane-L/Eyelight, and Resilient Hyaluronic Acid (RHA) 1/Redensity were the least resistant. The moderately resistant group comprised of Restylane Silk, Juvéderm Volbella, Revanesse Versa/Lips, and Belotero Balance on the less resistant side to Juvéderm Vollure, RHA 2, Restylane Contour, Juvéderm Ultra, Restylane Refyne, Belotero Intense, Restylane Kysse, RHA 3, Juvéderm Ultra Plus, and Restylane Defyne on the more resistant side. The most resistant were RHA 4, Juvéderm Voluma, Belotero Volume, and Juvéderm Volux. The most resistant fillers required 120 units of hyaluronidase per 0.2 mL filler to dissolve.

Conclusions

With the increasing popularity of fillers comes the increasing need to dissolve them for both ischemic and nonischemic complications. The majority of hyaluronic acid fillers available on the market are very resistant to hyaluronidase, which must be considered when determining the amount of hyaluronidase to dissolve a particular filler.

One-Year Data on the Longevity and Safety of Hyaluronic Acid Filler for Static Horizontal Neck Rhytids

BACKGROUND

The long-term efficacy and safety of hyaluronic acid fillers injected into the neck have yet to be analyzed in a prospective trial in the United States.

OBJECTIVE

Analyze the long-term efficacy and safety of a hyaluronic acid filler for static horizontal neck rhytids.

MATERIALS AND METHODS

Twenty-six subjects were enrolled in the study. Six subjects were randomized to receive saline and 20 subjects were randomized to receive HA RR. All subjects were randomized to use a cannula on 1 side and needle on the other with optional retreatment on day 30 and optional crossover treatment with different assignment on day 60. The subjects were graded using the Transverse Neck Line Scale, Canfield photography, and the Global Aesthetic Improvement Scale on day 360.

RESULTS

A significant improvement from baseline on day 360 was achieved on the Transverse Neck Line Scale according to the blind evaluator, subjects, and investigator without any delayed-onset or prolonged side effects. There was no significant difference in the average improvement from the short-term analysis on day 60 to the long-term analysis on day 360.

CONCLUSION

HA RR achieved significant long-term improvement in static horizontal neck rhytids without any long-term side effects.

Strengthening the Key Features of Volumizing Fillers: Projection Capacity and Long-Term Persistence

Volumizing fillers aim to create or restore facial volume in fat layers. To provide strong tissue lifting and long-term persistence, gels are generally designed with stiff properties, characterized by a high storage modulus (G'). However, clinical evidence shows a discrepancy between high G' and good lifting capacities, especially after skin tension has been exerted on the gel. To better explore the in vivo behavior of a gel, we first evaluated the elastic moduli of five commercial volumizers (RHA4, JUVVOL, RESVOL, RESLYFT, and BELVOL) in dynamic compression mode, E'. We further developed a Projection Index score based on the rheological assessment of creep in compression to mimic skin tension-induced stress relaxation (flattening). Finally, the ability of a gel to resist enzymatic degradation was analyzed with a multidose approach. Despite similar clinical indications, volumizers exhibited distinct behaviors. RHA4 and BELVOL showed the highest E' values (resistance to strain), RHA4, JUVVOL, and RESVOL exhibited the greatest projection capacities, while JUVVOL and RHA4 offered the largest persistence to enzymatic degradation. In this article, we introduce the use of the Projection Index to efficiently assess the ability of a gel to lift tissues, thus increasing preclinical models' efficiency and reducing the need for animal studies.

Decades of beauty: Achieving aesthetic goals throughout the lifespan

BACKGROUND

Several elements, including age, influence judgments of beauty and attractiveness. Aging is affected by intrinsic factors (e.g., genetics, race/ethnicity, anatomical variations) and extrinsic factors (e.g., lifestyle, environment).

AIMS

To provide a general overview of minimally invasive injectable procedures for facial beautification and rejuvenation to meet the aesthetic goals of patients across their lifespan, organized by decade.

METHODS

This case study review describes aesthetic considerations of females in their third to sixth decade of life (i.e., 20-60 years of age or beyond). Each case study reports the treatments, specifically botulinum toxin type A and soft tissue fillers, used to address aesthetic concerns.

RESULTS

Signs of aging, as well as aesthetic goals and motivations, vary by age groups, cultures, and races/ethnicities. However, there are overarching themes that are associated with each decade of life, such as changes in overall facial shape and specific facial regions, which can be used as a starting point for aesthetic treatment planning. Appropriate patient selection, thorough aesthetic evaluation, product knowledge, and injection technique, as well as good physician-patient communication, are essential for optimal treatment outcomes.

CONCLUSIONS

Nonsurgical facial injectable treatments can successfully enhance and rejuvenate facial features across different age ranges. A comprehensive understanding of facial aging and the aesthetic considerations of patients by the decade contributes to optimal treatment planning and maintenance.

Connections between cohesion and properties that related to safety and effectiveness of the hyaluronic acid dermal fillers: A comparative study of the cohesive and non-cohesive gels

BACKGROUND

Although the importance of the cohesion of a hyaluronic acid (HA) filler has been recognized, the relationship between the cohesion and the other performance that related to safety and effectiveness, as well as the underlying mechanism is barely studied. Much efforts need to be made on this subject to provide guidance for clinical practice.

MATERIALS AND METHODS

Two types of the HA fillers (cohesive and particulate gels) were selected for the comparison of the cohesion and the other key physicochemical properties.

RESULTS

Hyalumatrix, with significantly higher cohesion, was homogeneously smooth and showed a linearly oriented morphology, whereas Matrifill and Restylane were particulate and showed obvious boundaries between particles. The high cohesion of Hyalumatrix is beneficial to the properties that related to safety and effectiveness, including recovery under shear stress, injectability, tissue integration and in vitro resistance to enzymolysis. The underlying reason was that the strong internal interactions of the cohesive gel protect the network structure from collapse and keep the gel as an intact whole when the gel was subjected to the stress. The homogeneously smooth morphology further improved the tissue compliance and injectability. The G' of Hyalumatrix is in the middle level of the commercially available HA fillers.

CONCLUSION

Hyalumatrix is a rare HA filler product to possess good cohesion and intermediate G' simultaneously. More clinical practice is needed to verify the connection between the cohesion of Hyalumatrix and the clinical performance.

Hyaluronic acid-based fillers in patients with autoimmune inflammatory diseases

The use of hyaluronic acid (HA)-based aesthetic therapies is growing steadily, and according to the International Society of Aesthetic Plastic Surgery, more than 4.3 million aesthetic procedures using HA were performed in 2019, an increase of 15.7% than 2018. More people are offering these types of services, often without proper training or qualifications. Therefore, there is an increasing number of reports in the literature relating to possible adverse events, with subsequent therapeutic problems and more or less serious consequences for patients. The aim of this research is to carry out a review of the literature in order to evaluate the impact of hyaluronic acid-based fillers in patients with autoimmune inflammatory diseases, in particular scleroderma and Systemic Lupus Erythematosus (SLE). Although HA plays a central role in the inflammatory process, the use of HA-based fillers in patients with autoimmune inflammatory diseases is still controversial. HA, in fact, in inflamed tissues helps to propagate the inflammatory response and, injected in the form of a dermal filler, could potentially promote reactivation of the underlying disease. For this reason, many specialists do not perform HA-based aesthetic treatments in patients with scleroderma or SLE. However, recent scientific evidence suggests that the use of HA-based fillers in patients with scleroderma can lead to improvement of skin lesions, with satisfactory results. In the literature, there are no clinical studies that contraindicate the administration of HA-based dermal fillers in patients with inflammatory disease.

Facial fillers: Relevant anatomy, injection techniques, and complications

Objective

The aim of this review article is to discuss the currently available facial fillers, their differences and indications, relevant anatomy, injection techniques, and avoidance and management of complications.

Data Sources

Clinical experience and scientific papers.

Conclusions

Reversal of facial aging via filler injection has been around since the late 1800s with the initial use of detrimental products. Today, many safe and effective products exist and can be tailored to the individual patient's desired effect. With the evolution of both products and injection techniques, the rate of complications with facial filler use is low. Nonetheless, providers offering facial filler injections should have detailed knowledge of facial anatomy, including facial planes and soft tissue compartments. Multiple injection techniques exist. Different techniques should be used, depending on the anatomic target. Providers should also know how to avoid and manage complications.

Injectable fillers: current status, physicochemical properties, function mechanism, and perspectives

With the increasing understanding of the aging process and growing desire for minimally invasive treatments, injectable fillers have great potential for correcting and rejuvenating facial wrinkles/folds and contouring the face. However, considering the increasing availability of multiple soft tissue fillers, it is important to understand their inherent biophysical features and specific mechanism. Thus, in this review, we aim to provide an update on the current injectable filler products and analyze and compare their critical physicochemical properties and function mechanisms for volume-filling. Additionally, future trends and development processes for injectable fillers are also proposed.

TFOS Lifestyle: Impact of cosmetics on the ocular surface

In this report the use of eye cosmetic products and procedures and how this represents a lifestyle challenge that may exacerbate or promote the development of ocular surface and adnexal disease is discussed. Multiple aspects of eye cosmetics are addressed, including their history and market value, psychological and social impacts, possible problems associated with cosmetic ingredients, products, and procedures, and regulations for eye cosmetic use. In addition, a systematic review that critically appraises randomized controlled trial evidence concerning the ocular effects of eyelash growth products is included. The findings of this systematic review highlight the evidence gaps and indicate future directions for research to focus on ocular surface outcomes associated with eyelash growth products.

Precision of Soft-Tissue Filler Injections: An Ultrasound-Based Verification Study

BACKGROUND

Uncontrolled product spread is an important issue to consider in facial filler injections. Lack of precision can result in reduced effectiveness and surface projection, as well as irregularities and product visibility.

OBJECTIVES

The authors sought to assess the precision of soft-tissue filler injections in the face by employing a cannula.

METHODS

This single-center observational study investigated soft-tissue filler distribution utilizing real-time non-invasive ultrasound imaging. Outcome parameters included (1) the tissue plane of product distribution, (2) the extent of horizontal as well as vertical product spread at the injection site, and (3) the product surface area taking into account the multifactorial influence of several independent variables. Participants were followed up to 30 days post-injection.

RESULTS

A total 100 facial injections were performed in 8 patients (2 males, 6 females) with a mean age of 37.20 (±6.34) years and a mean BMI of 22.21 (±1.39) kg/m.2. The plane of product distribution remained constant in approximately 90% of cases at day 0 (d0), d14, and d30. Mean horizontal product spread was higher compared with vertical spread, and both significantly decreased over all time points (P < .001). Mean product surface area was 22.51 ± 16.34 mm2 at d0, 15.97 ± 11.28 mm2 at d14, and 12.9 ± 9.15 mm2 at d30. Analysis employing generalized linear models revealed that injection volume and injection depth significantly influenced product surface area.

CONCLUSIONS

Injection of soft-tissue filler employing a cannula allows precise application of the product within the intended tissue plane. Precision can be improved by injecting less product into deeper tissue layers.

LEVEL OF EVIDENCE: 5

Widening Aging Eyes and Ending Outdoor Tearing with Retrobulbar Injections of Dermal Fillers

As people age, the intraorbital fat may diminish and palpebral fissures may narrow, causing the eyes to increasingly tear outside in cold weather. As the bulbus recedes from the conjunctiva, a "wind trap" is formed in the lateral corner of the eye. This wind trap appears to irritate the adjacent lacrimal gland. In this article, an 84-year-old patient experienced annoying outdoor tearing despite having undergone three tarsal strip canthopexies during the past 20 years.

Methods

Retrobulbar injections of 3.5-mL high-viscous dermal fillers (Bellafill or Radiesse) pushed the eyeballs forward, aligned the bulbus with the conjunctiva, and closed the wind trap behind the lateral canthus. Magnetic resonance imaging confirmed the filler material in the posterior lateral corner of the orbit.

Results

The effect was immediate: the patient's constant outdoor tearing had resolved after the first treatment of his senile enophthalmos. In addition, the narrow palpebral fissure had widened by 2 mm and rejuvenated his aging eyes.

Conclusions

An eyeball that has receded with age can be pushed forward with a retrobulbar injection of a long lasting dermal filler to reattach to the eyelids.