Efficacy of bioresorbable plates in the osteosynthesis of linear mandibular fractures

Tailoring mechanical properties and degradation rate of maxillofacial implant based on sago starch/polylactid acid blend

A polymeric bone implants have a distinctive advantage compared to metal implants due to their degradability in the local bone host. The usage of degradable implant prevents the need for an implant removal surgery especially if they fixated in challenging position such as maxillofacial area. Additionally, this fixation system has been widely applied in fixing maxillofacial fracture in child patients. An ideal degradable implant has a considerable mass degradation rate that proved structural integrity to the healing bone. At this moment, poly(lactic acid) (PLA) or poly(lactic-co-glycolic acid) (PLGA) are the most common materials used as degradable implant. This composition of materials has a degradation rate of more than a year. A long degradation rate increases the long-term biohazard risk for the bone host. Therefore, a faster degradation rate with adequate strength of implant is the focal point of this research. This study tailored the tunable degradability of starch with strength properties of PLA. Blending system of starch and PLA has been reported widely, but none of them were aimed to be utilized as medical implant. Here, various concentrations of sago starch/PLA and Polyethylene glycol (PEG) were composed to meet the requirement of maxillofacial miniplate implant. The implant was realized using an injection molding process to have a six-hole-miniplate with 1.2 mm thick and 34 mm length. The specimens were physiochemically characterized through X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and Fourier Transform Infrared spectroscopy. It is found that the microstructure and chemical interactions of the starch/PLA/PEG polymers are correlated with the mechanical characteristics of the blends. Compared to a pure PLA miniplate, the sago starch/PLA/PEG blend shows a 60-80% lower tensile strength and stiffness. However, the flexural strength and elongation break are improved. A degradation study was conducted to observe the mass degradation rate of miniplate for 10 weeks duration. It is found that a maximum concentration of 20% sago starch and 10% of PEG in the PLA blending has promising properties as desired. The blends showed a 100-150% higher degradability rate compared to the pure PLA or a commercial miniplate. The numerical simulation was conducted and confirmed that the miniplate in the mandibular area were shown to be endurable with standard applied loading. The mechanical properties resulted from the experimental work was applied in the Finite Element Analysis to find that our miniplate were in acceptable level. Lastly, the in-vitro test showed that implants are safe to human cell with viability more than 80%. These findings shall support the use of this miniplate in rehabilitating mandibular fractures with faster degradation with acceptance level of mechanical characteristic specifically in case of 4-6 weeks bone union.