In dentistry, barrier membranes are used for guided tissue or bone regeneration (GTR/GBR). Particularly in guided bone regeneration, the immobilization of bone grafts through membrane fixation is crucial for success. This method limits graft movement, thereby ensuring a stable chamber for bone healing. Fixation is typically achieved using pins. Ideally, these pins are replaced by bone when no longer needed. Nonetheless, to this day dental practitioners have to use non-absorbable Titanium pins to fixate bioabsorbable membranes, which is a contradiction in concept. A new bioab-sorbable pin system based on Magnesium WE43 was developed and tested (pre-)clinically. Market approval was followed by first-in-patient cases, offering fully resorbable restorations of the oral cavity in different indications for the first time.Bioabsorbable dental pins were manufactured from WE43MEO (Meotec GmbH, Aachen) and tested ex-vivo against commercially available metal and polymer pins for pull-out, insertion force as well as shear strength. Further testing included pre-clinical testing in Aachen mini pigs over periods of 4, 8 and 16 weeks in groups of 4 animals against commercial Titanium pins (Ustomed GmbH & Co. KG, Tuttlingen), followed by µ-CT and histological evaluation. First clinical cases were conducted on male and female patients of different age in cases of ridge augmentation and vertical bone augmentation. Magnesium pins displayed mechanical stability and Biocompatibility in all pre-clinical testing. No wound healing disorders, toxic reactions, or allergic responses were noted. Despite visible gas accumulations, clinical findings showed successful pin fixation and membrane immobilization as well as stable and steady degradation without significant interference with bone healing. Thus, Magnesium pins offer an alternative to traditional Titanium pins, reducing risks like intraoral exposure and radiological artifacts in MRI. Magnesium pins provide adequate mechanical strength for membrane fixation and eliminate the need for pin removal in GTR/GBR procedures.

INTRODUCTION: Magnesium alloys are promising materials for biomedical applications, especially as biodegradable implants, due to their excellent mechanical properties and biocompatibility. However, their rapid corrosion and limited mechanical integrity in physiological environments pose significant challenges. Surface Mechanical Attrition Treatment (SMAT) addresses these issues by inducing severe plastic deformation and refining the coarse grain structure into a fine-grained structure. This study investigates the effects of SMAT on the biocompatibility of Mg5Zn0.2Ca magnesium alloy, exploring the relationship between grain refinement, corrosion resistance, cytotoxicity, and protein adsorption. METHODS: Mg5Zn0.2Ca alloy, consisting of 5 wt.% Zn, 0.2 wt.% Ca, and the remaining Mg, was selected for this study and was divided into three categories as shown in Table 1. Table 1. Specimen Nomenclature NomenclatureBall VelocitySMAT Duration Surface Coverage S110 m/s10 min.2000% S25 m/s23 min.2000% S3Non-SMATed TEM and EBSD were used to analyze grain refinement. Corrosion resistance was assessed using EIS, Tafel analysis, and immersion tests. followed by XRD to examine passivation behaviour. Eagle’s Minimum Essential Media (E-MEM) was used to perform corrosion and cytotoxicity experiments. Cytotoxicity extract tests (performed with L929 cell line) measured relative plating efficiency, while protein (Bovine serum albumin and fibronectin) adsorption tests quantified protein adherence. Optical microscopy and SEM were used to observe cell morphology and analyze corroded samples. RESULTS: TEM and EBSD analyses revealed significant grain refinement in SMATed samples, with sample S1 showing the finest grain structure (grain size of 40 ± 12 nm). EIS and Tafel analysis indicated that S1 had the highest corrosion resistance, followed by S2, with S3 exhibiting the least resistance. XRD analysis after immersion tests showed a thicker passive layer on SMATed samples, particularly on sample S1. Cytotoxicity tests demonstrated lower cytotoxicity (better relative plating efficiency) for S1, which also exhibited the increased protein adsorption. Optical microscopy and SEM confirmed better cell morphology and less corrosion damage in S1 and S2 compared to the S3. DISCUSSION & CONCLUSIONS: The observed grain refinement in SMATed samples, especially in S1, directly correlates with improved corrosion resistance and biocompatibility. Reduced corrosion current density, lower weight loss and smaller pitting depth depicts better corrosion performance for S1 and S2. This can also be attributed to the thicker passive layer identified in XRD analysis. Enhanced fibronectin protein adsorption on S1 (0.7456 μg/cm2) and S2 (0.9038 μg/cm2) further supports its improved biological performance. These findings demonstrate that higher SMAT intensity leads to better mechanical and biological behaviour of Mg5Zn0.2Ca magnesium alloy. The study highlights the potential of SMAT to optimize magnesium alloys for use in biodegradable implants, promoting their effectiveness and safety in medical environments. Future research should explore long-term performance and in vivo applications of SMATed magnesium alloys. REFERENCES: 1 Mojtaba Mollayousef et. al (2024) Effects of grain boundaries on the biocompatibility of the pure magnesium, J Mater Res Technol., vol. 28, pp 1121-1136. 2 Torkian A, Faraji G & Pedram M S (2021) Mechanical properties and in vivo biodegradability of Mg–Zr–Y–Nd–La magnesium alloy produced by a combined severe plastic deformation. Rare Met. Vol. 40, pp 651–662. 3 Paul S et al. (2020) New Mg-Ca-Zn amorphous alloys: biocompatibility, wettability and mechanical properties. Materialia, vol. 12, pp 100799. ACKNOWLEDGEMENTS: The authors would like to thank the Indian Institute of Technology, Indore, India, and National Institute for Materials Science, Japan for the support provided during the work.

A crucial aspect of treating pediatric fractures is ensuring that the active physis is not negatively affected by the implantation process and implants themselves. Any negative impact on the physis can result in deviations in longitudinal bone growth and deformations1. To mitigate this issue, bioresorbable magnesium (Mg)-based implants are used, thereby expanding the options for pediatric fracture treatment2. The aim of this study was to investigate the local and systemic responses to trans-epiphyseally implanted Mg-based ZX00 screws (Mg alloyed with <0.5 wt% Zn, <0.5 wt% Ca; l=40 mm; d=3.5 mm) on the active physis in a growing sheep model.

mm.X implants made from medical grade magnesium alloys have been used in numerous applications for more than 2 years in daily clinical routine in several European markets. Most commonly, the implants are becoming applied in orthopaedic care while surgical treatment traumatic fractures as well as elective. The overall clinical performance of and feedback on applied bioabsorbable magnesium implants under post-market surveillance exhibit very good clinical and functional results, irrespective of the anatomical region or injury pattern. Surgeons are highly satisfied with the results. Although with a clinically successful result (e.g. fracture consolidation and deformity correction), a very limited number cases revealed prominent radiolucent areas (most likely gas accumulations) in radiographic imaging. These findings did not show any patterns in regards to device related factors (device, material composition, batch, manufacturing time) or time after surgery (varying from 2 weeks to 7 months). Current research hypotheses is a patient related factor. The following factors (among others) and/or possible comorbidities are evaluated for potential influence on the bioabsorption pattern: •Treated indication, •Nicotin or Alcohol abusus, • Diabetes mellitus, •Age and •Osteoporosis. So far the number of these cases with prominent bioabsorption findings is very low and no statistical analysis can be performed. Based on results to this date, application of mm.X devices is safe and can be marketed consciously for a broad range of indications in orthopaedic care leading to highly satisfactory postoperative results. The education of surgeons, especially in regards to bioabsorption phenomena is crucial. Extension to further specialities of surgery is already ongoing. First indications in hand surgery (DIP fusion) have been successfully treated. Further devices will enlarge the portfolio in more disciplines in orthopaedic, trauma and sports medicine to broaden the data on mm.X implants and understand possible influences even better.