HYDROLYTIC DEGRADATION AND LOSS OF MECHANICAL STRENGTH OF POLYDIOXANONE THREADS: IMPLICATIONS OF EXPOSURE TO HYALURONIC ACID IN AESTHETIC PROCEDURESHYDROLYTIC DEGRADATION AND LOSS OF MECHANICAL STRENGTH OF POLYDIOXANONE THREADS: IMPLICATIONS OF EXPOSURE TO HYALURONIC ACID IN AESTHETIC PROCEDURES

*Dra. Kelly Christiane Ricca Martins, Dr. Carlos Ruiz da. Silva, Dr. Joy Martins

ABSTRACT

Introduction: Polydioxanone (PDO) threads are synthetic, biodegradable, and absorbable biomaterials widely used in minimally invasive procedures for rejuvenation and tissue support. Their ability to provide mechanical support depends on the temporary maintenance of the polymer's structural integrity, which undergoes progressive degradation primarily through hydrolysis. The increasing combined use of PDO threads and injectable biomaterials containing hyaluronic acid raises questions regarding potential interactions that could alter the degradation and mechanical properties of these threads. Objective: To experimentally evaluate the tensile strength of PDO threads after prolonged exposure to physiological saline or a formulation containing non-cross-linked hyaluronic acid, and to discuss the potential biomechanical and clinical implications of these findings for combined aesthetic procedures. Methods: Thirty barbed PDO threads were distributed into three experimental groups (n=10): control, kept in the original packaging at room temperature; physiological saline, with threads immersed in 15 mL of 0.9% saline solution; and NCTF135HA, with threads immersed in 15 mL of a formulation containing non-cross-linked hyaluronic acid at 5 mg/mL. The groups subjected to immersion were kept at 37.5°C for 30 days. Subsequently, all threads underwent tensile strength testing. Statistical analysis employed the Kruskal-Wallis test, followed by Dunn's post hoc test with Benjamini-Hochberg correction and a significance level of p<0.05 Results: Tensile strength was 2.39 ± 0.41 kgf in the control group, 0.84 ± 0.44 kgf in the physiological saline group, and 1.044 ± 0.47 kgf in the NCTF135HA group. Both groups subjected to immersion showed significantly lower strength than the control group (p<0.05), with no statistically significant difference between the physiological saline and NCTF135HA groups. Conclusion: Prolonged exposure of PDO threads to aqueous media, under the experimental conditions evaluated, resulted in a significant reduction in tensile strength. Although previous studies suggest a possible role of hyaluronic acid in accelerating PDO degradation, the results of this experiment did not demonstrate a significant difference between the formulation containing hyaluronic acid and physiological saline. The findings indicate that hydrolysis resulting from exposure to the aqueous medium represents a relevant mechanism for the progressive loss of PDO mechanical Properties.

Keywords: Polydioxanone; suspension threads; hyaluronic acid; hydrolysis; tensile strength; biomaterials; facial rejuvenation.