Evaluation of Collagen Membranes Coated with Testosterone and Alendronate to Improve Guided Bone Regeneration in Mandibular Bone Defects in Minipigs

Testosterone suppression impacts craniofacial growth structures during puberty : An animal study

AIM

Hormones play a crucial role in growth development; however, the impact of testosterone suppression (TS) on craniofacial growth during puberty remains inconclusive. This study aimed to evaluate the impact of TS during puberty on cephalometric measurements and histological characteristics of facial growth centers.

MATERIALS AND METHODS

Thirty-six heterogenic Wistar male rats were randomly allocated into experimental orchiectomy (ORX) and control (sham) groups. At an age of 23 days (prepubertal stage), orchiectomy and placebo surgery were performed. Cephalometric measurements were performed via lateral cephalograms during and after puberty. The animals were euthanized at an age of 45 days (pubertal stage) and 73 days (postpubertal stage). Histological slices of the growth centers (condyle, premaxilla, and median palatine suture) were stained with hematoxylin and eosin, and sirius red. Student's t or Mann-Whitney U tests were used to compare linear and angular cephalometric measurements across groups (α error = 5%).

RESULTS

Linear and angular measurements were statistically different in ORX animals (cranial bones, maxilla, and mandible) at 45 days and 73 days. Condylar histology showed a decrease in prechondroblast differentiation and a delay of mineralization in ORX animals. Vascularization of the medium palatine suture was lower in the ORX group at 45 days. Type I and III collagen fiber synthesis was lower in the ORX groups. In the premaxillary suture, collagen fibers were better organized in the sham groups.

CONCLUSIONS

Our results suggest that testosterone suppression affects craniofacial growth during puberty.

Various Coated Barrier Membranes for Better Guided Bone Regeneration: A Review

A good barrier membrane is one of the important factors for effective guided bone/tissue regeneration (GBR/GTR) in the case of periodontal bone defects. Several methods are being discussed to overcome and improve the shortcomings of commercially available membranes. One of the methods is to coat the membrane with bioactive materials. In this study, 41 studies related to coated membranes for GBR/GTR published in the last 5 years were reviewed. These studies reported coating the membrane with various bioactive materials through different techniques to improve osteogenesis, antimicrobial properties, and physical/mechanical properties. The reported studies have been classified and discussed based on the purpose of coating. The goal of the most actively studied research on coating or surface modification of membranes is to improve new bone formation. For this purpose, calcium phosphate, bioactive glass, polydopamine, osteoinduced drugs, chitosan, platelet-rich fibrin, enamel matrix derivatives, amelotin, hyaluronic acid, tantalum, and copper were used as membrane coating materials. The paradigm of barrier membranes is changing from only inert (or biocompatible) physical barriers to bioactive osteo-immunomodulatory for effective guided bone and tissue regeneration. However, there is a limitation that there exists only a few clinical studies on humans to date. Efforts are needed to implement the use of coated membranes from the laboratory bench to the dental chair unit. Further clinical studies are needed in the patients’ group for long-term follow-up to confirm the effect of various coating materials.

Sustained release of ancillary amounts of testosterone and alendronate from PLGA coated pericard membranes and implants to improve bone healing

Testosterone and alendronate have been identified as two bone healing compounds which, when combined, synergistically stimulate bone regeneration. This study describes the development of a novel ultrasonic spray coating for sustained release of ancillary amounts of testosterone and alendronate encapsulated in PLGA 5004A as a carrier. Due to the low amounts of testosterone and alendronate used, sensitive in vitro assays were developed to determine in vitro release. The ultrasonic spray coating technology was optimized for coating titanium screws and pericardial collagen membranes, with the aim to improve osseo-integration and (guided) bone regeneration, respectively, without interfering with their primary mode of action. In vitro release analysis of collagen membranes and screws showed up to 21 days sustained release of the compounds without a burst release. Subsequent preclinical studies in rat and rabbit models indicated that testosterone and alendronate coated membranes and screws significantly improved bone regeneration in vivo. Coated membranes significantly improved the formation of new bone in a critical size calvarial defect model in rats (by 160% compared to controls). Coated screws implanted in rabbit femoral condyles significantly improved bone implant contact (69% vs 54% in controls), bone mineral density (121%) and bone volume (119%) up to 1.3 mm from the implant. Based on the results obtained, we suggest that implants or membranes enabled with local sustained delivery of ancillary amounts of testosterone and alendronate can be a promising system to stimulate local bone regeneration resulting in improved osseo-integration of implants and improved healing of bone defects and fractures.