Fibrocartilage‐ a new temporary structure related to healing of alveolar sockets: Prospective clinical, histologic, histomorphometric and imunohistochimic study

Background Healing of alveolar sockets follows a well-known chronological sequence. Fibrocartilage is a structure habitually found in compression zones like intervertebral discs, entheses and meniscus. Histologically, it is characterized by the presence of chondrocytes in chondroblasts among a tissue composed of sinuous and dense bundles of collagen I and collagen II fibres. No study has described yet fibrocartilage as an histological structure appearing during the process of dental socket healing. Aim/Hypothesis The aim of this study was to characterize fibrocartilage during the healing process of dental sockets, and be able to link its occurrence with the stage of healing of the socket. Materials and Methods A prospective interventional clinical study was performed. Fifteen 2 mm diameter bone biopsies were realized in 13 patients at the time of implant placement (between 2.5 and 9 months after extraction) - 13 biopsies in DFDBA and A-PRF grafted sockets, and 2 in native bone. Histologic stainings hematoxylin-eosin and Masson's trichrome were realized. Following histomorphometric analysis by two independent operators using FIJIImageJ program, samples were classified according to a score of increasing bone maturity quality ranging from score 1 to 3. A statistical analysis was performed with STATA14 program, as for interoperators concordance. Imunohistochimic techniques were applied in order to detect collagen I and Collagen II fibers. Hyaline cartilage and tibiofemoral meniscal fibrocartilage from a fresh cadaver served as respectively negative and positive controls for fibrocartilage, both histologically and immunohistochemically. Results Among 13 bone samples from grafted alveolar sockets, 6 showed histological structure compatible with fibrocartilage. Fibrocartilage was detected in samples ranging from 2.5 to 9 months of healing, for a mean score of bone maturity of 2. None native bone sample displayed fibrocartilage. Immunomarquage for collagen I was positive on one slide at the level of fibrocartilage, and for collagen II on 2 slides. The aspect of the collagen fibers detected (dense and sinuous bundles of collagen fibers) was typical of fibrocartilage. Conclusion and Clinical Implications This study describes for the first time that fibrocartilage could represent a histological structure occurring during healing of alveolar sockets at a stage of intermediate bone maturity. It is not excluded that the materials used to graft sockets (DFDBA and PRF) play a role in the occurrence of fibrocartilage during the process of healing of dental alveolar sockets.