Over the past four decades, calcium phosphate cements (CPCs) have emerged as promising materials for bone repair due to their biocompatibility, osteoconductivity, and in situ hardening properties. Developed from a combination of calcium phosphate (CaP)-based powder and a liquid phase, CPCs undergo a chemical reaction when mixed, forming a crystalline solid structure at body temperature. This hardening process is characterized by its mildly exothermic reaction, offering significant advantages compared with cements like polymethylmethacrylate, commonly used in orthopedic surgeries. Over more than four decades of research, various modifications have been introduced to the physical, mechanical, and biological properties of CPCs, making them adaptable to a wide range of clinical applications, from craniofacial surgery to bone tissue engineering and drug delivery systems. Despite all the advancements, the widespread clinical use of CPCs still faces significant challenges, such as limitations in mechanical strength, degradation rate, and osteoinductive properties. This article provides a comprehensive historical and technical overview of CPC development from their initial discovery in 1980s to current innovations in formulation, physicochemical, mechanical, and biological properties. It highlights crucial milestones in each decade, covering the evolution of these cements and presenting the challenges that remain until today.

Tissue Engineering Part AVol. 30, No. 1-2 Letter from the Editors30 Years of Tissue EngineeringJohn P. Fisher, Antonios G. Mikos, Katja Schenke-Layland, Heungsoo Shin, John A. Jansen, and Xiumei WangJohn P. FisherFischell Department of Bioengineering, University of Maryland, College Park, Maryland, USA.Search for more papers by this author, Antonios G. MikosDepartment of Bioengineering, Rice University, Houston, Texas, USA.Search for more papers by this author, Katja Schenke-LaylandInstitute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University, Tübingen, Tübingen, Germany.NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany.Search for more papers by this author, Heungsoo ShinDepartment of Bioengineering, Hanyang University, Seoul, South Korea.Search for more papers by this author, John A. JansenDepartment of Regenerative Biomaterials, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.Search for more papers by this author, and Xiumei WangSchool of Materials Science and Engineering, Institute for Regenerative Medicine and Biomimetic Materials, Tsinghua University, Beijing, China.Search for more papers by this authorPublished Online:17 Jan 2024https://doi.org/10.1089/ten.tea.2023.29053.johAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookXLinked InRedditEmail View article"30 Years of Tissue Engineering." Tissue Engineering Part A, 30(1-2), pp. 3–4FiguresReferencesRelatedDetails Volume 30Issue 1-2Jan 2024 InformationCopyright 2024, Mary Ann Liebert, Inc., publishersTo cite this article:John P. Fisher, Antonios G. Mikos, Katja Schenke-Layland, Heungsoo Shin, John A. Jansen, and Xiumei Wang.30 Years of Tissue Engineering.Tissue Engineering Part A.Jan 2024.3-4.http://doi.org/10.1089/ten.tea.2023.29053.johPublished in Volume: 30 Issue 1-2: January 17, 2024PDF download

Calcium phosphate cement (CPC) has evolved as an appealing bone substitute material, especially since CPCs were combined with poly(lactic-co-glycolic acid) (PLGA) porogens to render the resulting CPC/PLGA composite degradable. In view of the multiple variables of CPC and PLGA used previously, the effect of CPC composition and PLGA porogen morphology (i.e., microspheres versus microparticles) on the biological performance of CPC/PLGA has not yet been investigated. Consequently, we here aimed to evaluate comparatively various CPC/PLGA formulations varying in CPC composition and PLGA porogen morphology on their performance in a rabbit femoral condyle bone defect model. CPCs with a composition of 85 wt% α-TCP, 15 wt% dicalcium phosphate anhydrate (DCPA) and 5 wt% precipitated hydroxyapatite (pHA), or 100 wt% α-TCP were combined with spherical or irregularly shaped PLGA porogens (CPC/PLGA ratio of 60:40 wt% for all formulations). All CPC/PLGA formulations were applied via injection in bone defects, as created in the femoral condyle of rabbits, and retrieved for histological evaluation after 6 and 12 weeks of implantation. Descriptive histology and quantitative histomorphometry (i.e., material degradation and new bone formation) were used for analyses. Descriptively, all CPC/PLGA formulations showed material degradation at the periphery of the cement within 6 weeks of implantation. After 12 weeks, bone formation was observed extending into the defect core, replacing the degraded CPC/PLGA material. Quantitatively, similar material degradation (up to 87%) and new bone formation (up to 28%) values were observed, irrespective of compositional variations of CPC/PLGA formulations. These data prove that neither the CPC compositions nor the PLGA porogen morphologies as used in this work affect the biological performance of CPC/PLGA formulations in a rabbit femoral condyle bone defect model.

Peri-implant gingival tissue integration (GTI) is pivotal in determining the long-term success and functionality of dental implants. To enhance GTI, researchers have increasingly focused during the past decade on unraveling the response of gingival tissues to implant surfaces. This increased focus on soft instead of hard tissue integration has led to the development of various models, including in vitro cell culture systems and in vivo animal models, designed to predict and assess GTI around dental implants. However, inconsistent study outcomes between the different models have created confusion, highlighting the need for a comprehensive review. Therefore, the main objective of this review is to present a comprehensive overview of existing in vitro models, ranging from 2D to 3D, specifically designed to investigate cellular behavior relevant to peri-implant GTI. To facilitate a better comprehension of the utility of these models, the review initiates an elucidation of the histological characteristics of gingival tissues surrounding natural dentition, offering insights into the healing dynamics and histological adaptation processes occurring in gingival tissues adjacent to dental implants. In addition, through a critical evaluation of the strengths and limitations inherent in each model, our aim is to contribute to a more profound understanding of their applicability and effectiveness in GTI research.

The aim of this study was to test the suitability of calcium phosphate cement mixed with poly(lactic-co-glycolic acid) (CPC-PLGA) microparticles into a ring-shaped polymeric space-maintaining device as bone graft material for lateral bone augmentation. Therefore, the bone chambers were installed on the lateral portion of the anterior region of the mandibular body of mini-pigs. Chambers were filled with either CPC-PLGA or BioOss((R)) particles for comparison and left for 4 and 12 weeks. Histology and histomorphometry were used to obtain temporal insight in material degradation and bone formation. Results indicated that between 4 and 12 weeks of implantation, a significant degradation of the CPC-PLGA (from 75.1% to 23.1%), as well as BioOss material, occurred (from 40.6% to 14.4%). Degradation of both materials was associated with the presence of macrophage-like and osteoclast-like cells. Furthermore, a significant increase in bone formation occurred between 4 and 12 weeks for the CPC-PLGA (from 0.1% to 7.2%), as well as BioOss material (from 8.3% to 23.3%). Statistical analysis showed that bone formation had progressed significantly better using BioOss compared to CPC-PLGA (p < 0.05). In conclusion, this mini-pig study showed that CPC-PLGA does not stimulate lateral bone augmentation using a bone chamber device. Both treatments failed to achieve "clinically" meaningful alveolar ridge augmentation.

Biocompatibility testing for a new implant material is necessary before clinical use. The materials for bone scaffolding must also go through biocompatibility tests both in vitro and in vivo. The purpose of this study was to compare different staining methods in histological preparations to assess the biocompatibility of the material to tissues. Twenty Wistar rats (n= 20), aged 4 months, males, weighing about 250-350 g were divided into 2 research groups, namely sub-cutaneous and bone implantation for 3, 14, and 30 days. The sample was a biodegradable material with gypsum and calcium carbonate as the basic ingredients. Histological stains were prepared in several ways using Hematoxylin Eosin (HE), Mallory, Toluidine Blue, Tartrate-resistant acid phosphatase polyclonal antibody (TRAP), and Chromogen 3,3 diaminobenzidine (DAB) after pre-performing a decalcification process with ethylenedinitril-o-tetra-acetic acid (EDTA). The observation was done using magnification ranging from 10X10 to 100X10 with a light microscope (Nikon eclipse E600) and OptiLab viewer. The results were displayed in the form of descriptions of images generated from different staining methods. Staining by the HE method is most often chosen because it is cheap and easy but the other staining methods such as Toluidine Blue, Mallory, and TRAP show better contrast. Tissue staining techniques with immunohistochemistry (DAB, VEGF) are used to evaluate cell and tissue responses by identifying specific proteins present.

OBJECTIVE:Considering the elevated number of osteoporotic patients in need of bone graft procedures, we here evaluated the effect of alendronate (ALN) treatment on the regeneration of bone defects in osteoporotic rats. Bone formation was histologically and histomorphometrically assessed in rat femoral condyle bone defects filled with bone graft (Bio-Oss®) or left empty.METHODS:Male Wistar rats were induced osteoporotic through orchidectomy (ORX) and SHAM-operated. The animals were divided into three groups: osteoporotic (ORX), osteoporotic treated with ALN (ORX + ALN) and healthy (SHAM). Six weeks after ORX or SHAM surgeries, bone defects were created bilaterally in femoral condyles; one defect was filled with Bio-Oss® and the other one left empty. Bone regeneration within the defects was analyzed by histology and histomorphometry after 4 and 12 weeks.RESULTS:Histological samples showed new bone surrounding Bio-Oss® particles from week 4 onward in all three groups. At week 12, the data further showed that ALN treatment of osteoporotic animals enhanced bone formation to a 10-fold increase compared to non-treated osteoporotic control. Bio-Oss® filling of the defects promoted bone formation at both implantation periods compared to empty controls.CONCLUSION:Our histological and histomorphometric results demonstrate that the enteral administration of alendronate under osteoporotic bone conditions leverages bone defect regeneration to a level comparable to that in healthy bone. Additionally, Bio-Oss® is an effective bone substitute, increasing bone formation, and acting as an osteoconductive scaffold guiding bone growth in both healthy and osteoporotic bone conditions.SIGNIFICANCE:Based on the results of this study, enteral use of ALN mitigates adverse effects of an osteoporotic condition on bone defect regeneration.

Cinnamaldehyde is an organic component in cinnamon and has anti-inflammatory, antibacterial, and osteogenic properties. Loading cinnamaldehyde with a concentration of 4% into an artificial scaffold from gypsum calcium carbonate hydrogel could reduce inflammation, accelerate healing, and promote new bone regeneration at bone implantation surgery. The aim of this study was to investigate the impact of cinnamaldehyde loaded on gypsum-hydrogel calcium carbonate on the process of wound healing and bone regeneration in rats. Implantation of bone scaffolding from gypsum hydrogel calcium carbonate with an addition of cinnamaldehyde was performed on 20 5-month-old Sprague-Dawley rats weighing 300-350 g in an artificial defect of condyle femoris bone dexter and sinister. Group A was a control with gypsum only, while groups B, C, and D were given gypsum and CaCO3 with a combination of cinnamaldehyde or dehydrothermal treatment (DHT). Euthanasia was performed after implantation at 1, 4 and 8 weeks for 4 groups (n = 3). Femoris condyle bone was cut, made into histological preparations by hematoxylin eosin (HE) staining, and analyzed descriptively. The results showed that the loading of cinnamaldehyde on the scaffold was effective in weeks 1 and 4, but after 8 weeks of implantation, cinnamaldehyde was observed to inhibit defect closure. The cinnamaldehyde group combined with dehydrothermal (DHT) treatment was found to be better than those without DHT.

Polyisocyanopeptide (PIC) hydrogels are proposed as promising wound dressings. These gels are thermo-sensitive, allow application as a cold liquid, and rely on gelation through body heat. It is supposed that the gel can be easily removed by reversing the gelation and washing it away with a cold irrigation solution. The impact on wound healing of the regular application and removal of PIC dressings is compared to a single application of PIC and the clinically used Tegaderm™ in murine splinted full-thickness wounds for up to 14 days. SPECT/CT analysis of 111In-labelled PIC gels showed that, on average, 58% of the PIC gel could be washed out of the wounds with the employed method, which is, however, heavily influenced by personal technique. Evaluation with photography and (immuno-)histology showed that wounds in which PIC dressings were regularly removed and replaced were smaller at 14 days post-injury but performed on par with the control treatment. Moreover, the encapsulation of PIC in wound tissue was less severe and occurred less often when PIC was regularly refreshed. In addition, no morphological damage related to the removal procedure was observed. Thus, PIC gels are atraumatic and perform similarly to currently employed wound dressing materials, offering possible future benefits for both clinicians and patients.

Craniofacial defects require a treatment approach that provides both robust tissues to withstand the forces of mastication and high geometric fidelity that allows restoration of facial architecture. When the surrounding soft tissue is compromised either through lack of quantity (insufficient soft tissue to enclose a graft) or quality (insufficient vascularity or inducible cells), a vascularized construct is needed for reconstruction. Tissue engineering using customized 3D printed bioreactors enables the generation of mechanically robust, vascularized bony tissues of the desired geometry. While this approach has been shown to be effective when utilized for reconstruction of non-load bearing ovine angular defects and partial segmental defects, the two-stage approach to mandibular reconstruction requires testing in a large, load-bearing defect. In this study, 5 sheep underwent bioreactor implantation and the creation of a load-bearing mandibular defect. Two bioreactor geometries were tested: a larger complex bioreactor with a central groove, and a smaller rectangular bioreactor that were filled with a mix of xenograft and autograft (initial bone volume/total volume BV/TV of 31.8 ± 1.6%). At transfer, the tissues generated within large and small bioreactors were composed of a mix of lamellar and woven bone and had BV/TV of 55.3 ± 2.6% and 59.2 ± 6.3%, respectively. After transfer of the large bioreactors to the mandibular defect, the bioreactor tissues continued to remodel, reaching a final BV/TV of 64.5 ± 6.2%. Despite recalcitrant infections, viable osteoblasts were seen within the transferred tissues to the mandibular site at the end of the study, suggesting that a vascularized customized bony flap is a potentially effective reconstructive strategy when combined with an optimal stabilization strategy and local antibiotic delivery prior to development of a deep-seated infection.

Implant-supported dental prosthetics are widely used in dental practice. Sufficient peri-implant bone tissue is a crucial prerequisite for the long-term success of this treatment, as insufficient peri-implant bone volume hampers dental implant installation and negatively influences dental implant stability. However, due to tooth extraction, bone metabolism diseases, and trauma, bone defects in the jaw are common in patients, particularly in the elderly and those suffering from underlying conditions. If this is the case, the alveolar ridge has to be augmented for reliable implant placement. Various biomaterials, growth factors (GFs) or GF-based products, and trace elements have been tested and used for alveolar ridge augmentation. Among those biomaterials, calcium phosphates (CaPs) are the most popular due to their promising biocompatibility, great osteoconductivity, and distinguishing osteogenesis. Combining CaPs with GFs or trace elements can further favor bone defect repair. This review mainly focuses on applying artificial CaP biomaterials and their combination with bioactive agents to repair bone defects in implant dentistry. Impact statementInsufficient bone volume is still a challenge in implant dentistry, and various bone substitutes have been reported to be used for bone augmentation. In implant dentistry, calcium phosphate (CaP) ceramics are the most well-used. Meanwhile, the advantages and disadvantages of these ceramics have also been reported. On the contrary, to improve their performance in dental clinical practice, growth factors (GFs) are engaged and combined with CaP bone substitutes for bone regeneration. This review recapitulates these CaP biomaterials and GFs, which may guide their clinical application in implant dentistry.

Background Osteomyelitis is a bacterial infection, which leads to bone loss. Local treatment focuses on elimi-nation of bacteria, which is preferable for simultaneous management of the bone defect after sequestrectomy and bone reconstruction in one-stage treatment of osteomyelitis. Calcium phosphate cements (CPCs) have attracted increased attention as bone substitute material because of their injectability and in situ self-setting properties, which allow for minimally invasive surgical procedures and local drug delivery. Methods We herein established a system to achieve different release profiles of the antibiotic drug doxycycline from CPC by finetuning their formulation. These CPC formulations were generated via facile addition of hy-drolytically degrading PLGA particles, varying doses of doxycycline, and addition of the lubricant CMC. Results The CPC formulations exhibited appropriate handling properties in terms of injectability and setting time. Furthermore, doxycycline release profiles showed an adequate burst release followed by a cumulative release of up to 100% over a period of 8 weeks. Importantly, the released doxycycline retained its antibacterial activity against Staphylococcus aureus, the major pathogen causing osteomyelitis. Using an in vivo implantation model, antibacterial efficacy was demonstrated by a rapid decrease of inoculated S. aureus at the CPC surface and within surrounding tissues. Conclusions Our data show the versatility of the CPC system toward local antibacterial therapy, extending its application beyond bone substitution.

Tissue Engineering Part C: MethodsVol. 28, No. 7 Guest EditorialEditorial for Special Issue on “New Strategies in Biomaterials Design for Tissue Regeneration”Mani Diba and John JansenMani DibaAddress correspondence to: Mani Diba, PhD, Department of Regenerative Biomaterials, Radboud University Medical Center, PO Box 9101, Nijmegen 6500 HB, The Netherlands E-mail Address: mani.diba@radboudumc.nlDepartment of Regenerative Biomaterials, Radboud University Medical Center, Nijmegen, The Netherlands.Search for more papers by this author and John JansenJohn Jansen, DDS, PhD, Department of Regenerative Biomaterials, Radboud University Medical Center, PO Box 9101, Nijmegen 6500 HB, The Netherlands E-mail Address: john.jansen@radboudumc.nlDepartment of Regenerative Biomaterials, Radboud University Medical Center, Nijmegen, The Netherlands.Search for more papers by this authorPublished Online:14 Jul 2022https://doi.org/10.1089/ten.tec.2022.29033.editorialAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"Editorial for Special Issue on “New Strategies in Biomaterials Design for Tissue Regeneration”." Tissue Engineering Part C: Methods, 28(7), pp. 287–288FiguresReferencesRelatedDetails Volume 28Issue 7Jul 2022 InformationCopyright 2022, Mary Ann Liebert, Inc., publishersTo cite this article:Mani Diba and John Jansen.Editorial for Special Issue on “New Strategies in Biomaterials Design for Tissue Regeneration”.Tissue Engineering Part C: Methods.Jul 2022.287-288.http://doi.org/10.1089/ten.tec.2022.29033.editorialPublished in Volume: 28 Issue 7: July 14, 2022PDF download

The aim of this preclinical study was to test the applicability of calcium phosphate cement (CPC)-poly(lactic-co-glycolic acid) (PLGA)-carboxymethylcellulose (CMC) as a bone substitute material for guided bone regeneration (GBR) procedures in a clinically relevant mandibular defect model in minipigs. In the study, a predicate device (i.e., BioOss((R))) was included for comparison. Critical-sized circular mandibular bone defects were created and filled with either CPC-PLGA-CMC without coverage with a GBR membrane or BioOss covered with a GBR membrane and left to heal for 4 and 12 weeks to obtain temporal insight in material degradation and bone formation. Bone formation increased significantly for both CPC-PLGA-CMC and BioOss with increasing implantation time. Further, no significant differences were found for bone formation at either 4 or 12 weeks between CPC-PLGA-CMC and BioOss. Finally, bone substitute material degradation increased significantly for both CPC-PLGA-CMC and BioOss from 4 to 12 weeks of implantation, showing the highest degradation for CPC-PLGA-CMC (similar to 85%) compared to BioOss (similar to 12%). In conclusion, this minipig study showed that CPC-PLGA-CMC can be used as a bone-grafting material and stimulates bone regeneration to a comparable extent as with BioOss particles. Importantly, CPC-PLGA-CMC degrades faster compared to BioOss, is easier to apply into a bone defect, and does not need the use of an additional GBR membrane. Consequently, the data support the further investigation of CPC-PLGA-CMC in human clinical trials. Impact Statement Guided bone regeneration (GBR) is a frequently used dental surgical technique to regenerate the alveolar ridge to allow stable implant installation. However, stabilization of the GBR membrane and avoidance of bone graft movement remain a challenge. Consequently, there is need for the development of alternative materials to be used in GBR procedures that are easier to apply and induce predictable bone regeneration. In this minipig study, we focused on the applicability of calcium phosphate cement-poly(lactic-co-glycolic acid)-carboxymethylcellulose as an alternative bone substitute material for GBR procedures without the need of an additional GBR membrane.

Craniomaxillofacial bone defects represent a clinical challenge in the fields of maxillofacial surgery and (implant) dentistry. Regeneration of these bone defects requires the application of bone graft materials that facilitate new bone formation in a safe, reliable, and predictive manner. In addition to autologous bone graft, several types of (synthetic) bone substitute materials have become clinically available, and still major efforts are focused on improving such bone substitute materials by optimizing their properties. Given the regulatory necessity to evaluate the performance of new bone substitute materials for craniomaxillofacial bone regeneration in a large animal model with similarity to human bone before clinical application, we here describe a mini-pig mandibular bone defect model that allows for the creation of multiple (critical-size) bone defects within the mandibular body of a single animal. As examples of bone substitute materials, we utilize both the clinically used BioOss granules and an experimental calcium phosphate cement for filling the created defects. Regarding the latter, its advantages are the injectable application within the defect site, in which the material rapidly sets, and the tailorable degradation properties via the inclusion of hydrolytically degrading polymeric particles. For both bone substitute materials, we show the suitability of the bone defect model to assess bone regeneration via histology and micro-computed tomography. Impact statement Given the regulatory necessity to evaluate the performance of new bone substitute materials for craniomaxillofacial bone regeneration in a large animal model with similarity to the human bone before clinical application, we here describe a mini-pig mandibular bone defect model that allows for the creation of multiple (critical-size) bone defects within the mandibular body of a single animal that can be used for the evaluation of the bone regenerative capacity of new bone grafting materials as well as tissue-engineered products for alveolar bone regeneration.