Bioactive bone cement: effect of surface curing properties on bone-bonding strength

Current research on bone cements has focused on how surface properties affect bonding with bone. It is already known that bisphenol-A-glycidyl methacrylate (bis-GMA) resins are commonly used in composite cements. However, the impact of uncured surfaces on bioactivity remains unclear. Prior studies have examined the mechanical properties of cured cements, but few have explored the role of uncured surfaces in promoting bone bonding. This gap motivated the present investigation into the effect of uncuring one side of a cement plate. No prior work had resolved whether uncured surfaces might enhance bonding. The study aimed to address this uncertainty by comparing uncured and cured surfaces. Histological and mechanical evaluations were needed to confirm the hypothesis. Understanding this could improve the design of bioactive bone cements.

The purpose of the study was to assess how the presence of an uncured surface affects the bone-bonding strength of composite cements. Researchers aimed to test whether the uncured surface of a bis-GMA-based cement could promote stronger bonding with bone. The study compared two types of composite cements: one with apatite- and wollastonite-containing glass-ceramic (AW-GC) and another with hydroxyapatite (HA). Both cements had 70 wt % of their respective powders. The hypothesis was that the uncured surface would show greater bioactivity than the cured side. The goal was to measure the failure load of each surface in vivo. Histological analysis was also planned to observe bone-cement interactions. This approach was chosen to provide both mechanical and biological evidence.

The study used composite cement plates made of bis-GMA resin and either AW-GC or HA powder. Each plate had one uncured and one cured surface. The plates were implanted into the tibiae of male Japanese white rabbits. The surface orientation was preserved during implantation. After 8 weeks, a detaching test was performed to measure failure load. Histological examination of the bone-cement interface followed. The uncured and cured surfaces were compared within and between the two cement types. Statistical analysis was used to assess differences in failure load. The presence of a Ca-P-rich layer was evaluated in histological samples. This method allowed for both mechanical and structural evaluation of the surfaces.

The failure load for AWC-plates at the uncured surface was 2.05 ± 1.11 kgf, significantly higher than the cured surface at 0.28 ± 0.64 kgf. For HAC-plates, the uncured surface had a failure load of 1.40 ± 0.68 kgf, compared to 0.00 ± 0.00 kgf for the cured surface. AWC uncured surfaces showed higher failure loads than HAC uncured surfaces, though not significantly. AWC cured surfaces also had higher failure loads than HAC cured surfaces. Histological analysis revealed direct bone formation on both uncured surfaces. A Ca-P-rich layer was observed only on the AWC uncured surface. These findings suggest that uncured surfaces may enhance bioactivity. The presence of a Ca-P layer supports the role of uncured surfaces in promoting bonding.

The study found that uncured surfaces of AWC and HAC cements showed higher bone-bonding strength than their cured counterparts. The researchers propose that uncured surfaces may expose bioactive fillers, enhancing bonding. The presence of a Ca-P-rich layer on AWC uncured surfaces supports this idea. The findings suggest that uncured surfaces could be useful in composite cement design. The authors did not claim that this is the only method for improving bonding. The comparison between AWC and HAC showed no significant difference in uncured surface strength. The study did not extend to other filler types or surface treatments. The results highlight the potential of uncured surfaces in promoting bone bonding.