Photo of the dental implant in place (I) and molding the cement around it (II) to stabilize it. The cement set around the dental implant is shown (III) and how mechanical properties are measured (IV).Dental implants inserted immediately after extractions cut treatment time, minimize surgical interventions, help positioning and healing. But if there is a gap between the implant and the surrounding bone, a biomaterial is needed. Bone cements made of calcium phosphate can be used to give the implant stability. Sometimes, however, these cements are too brittle for the job. Researchers from Radboud University Medical Center in the Netherlands have developed a cement reinforced with polymer fibers that is stronger and tougher [Schickert et al., Acta Biomaterialia 110 (2020) 280-288, https://doi.org/10.1016/j.actbio.2020.03.026 ].
“Injectable bioceramic bone cements can stabilize dental implants much more efficiently when these cements are reinforced with polymeric fibers,” says Sander Leeuwenburgh, who led the work. “Such stabilization is clinically required to provide sufficient initial stability to dental implants.”
The new cement is made from a self-hardening calcium phosphate mixture reinforced with poly(vinyl alcohol) fibers, which are routinely used in civil engineering to reinforce concrete. Once implanted in a bone or dental defect, the fiber-reinforced cement hardens in a few minutes.
“The fiber-reinforced cement is much less brittle than conventional bioceramic cements, which enables us to improve the initial stabilization of dental implants in bone defects,” explains Leeuwenburgh. “Moreover, the cement is enriched with biodegradable porogens made of polyester particles.”
While fibers provide short-term stabilization of the implant, the biodegradable polyester particles break down gradually over time making space for newly grown bone to fill in.
“Bioceramic cements have never been reinforced by a combination of poly(vinyl alcohol) fibers and polyester porogens,” points out Leeuwenburgh. “This dual functionality has never been reported before.”
The results are promising both in vitro and in vivo, say the researchers. In vitro, fiber-reinforced calcium phosphate cement in synthetic bone analogue defects show better implant stability over 12 weeks compared with fiber-free cement. Tests in rabbits likewise show better mechanical performance and implant stability with the fiber-reinforced cement. Moreover, the fiber-reinforced cement is compatible with bone regrowth over the longer term.
“Although our results indicate that the biocompatibility of the bioceramic cement is not compromised by the incorporation of poly(vinyl alcohol) fibers? after several months of implantation, more extensive in vivo studies are required to confirm that the poly(vinyl alcohol fibers) do not cause adverse biological responses even after longer implantation times of several years,” cautions Leeuwenburgh.
The researchers are now developing a computational model of the fiber-reinforced cement with specialist collaborators to predict mechanical failure behavior depending on the fiber dimension, dispersion, and affinity with the matrix.