Aim To examine the in vitro biokinetics of hyaluronic acid (HA) from a collagen membrane (CM) and to evaluate the in vivo effect of immersion of the CM in HA solution on its degradation in streptozotocin (STZ)‐induced diabetes conditions in a rat calvaria subcutaneous model. Background CM degradation is accelerated in uncontrolled diabetic rats. Immersion of CM in HA has been suggested to decrease their resorption rate without interfering with their tissue integration and structural degradation. However, it is unknown to what extent CM degradation may be influenced by its immersion in HA solution under a condition mimicking a medically compromised situation with an increased inflammatory level such as diabetes. Materials and Methods CMs were soaked in cross‐linked HA. Protein adsorption and the HA release were quantified by ELISA. Diabetes was induced in sixteen rats, while 16 healthy rats served as control. CM was prepared and labeled prior to implantation with Biotin. Seventeen CM were immersed in HA and 17 CM in PBS. In each animal, one test or one control disk was implanted. In order to compare the collagen content, two similar non‐implanted CM were used as baseline. Fourteen days after surgery, thirty‐two animals were sacrificed. The entire calvaria including the skin above, was chemically fixed, decalcified, and embedded in paraffin. Five‐μm‐thick sections were analyzed histologically and histomorphometrically using H&E and avidin‐peroxidase staining. Results The in vitro results demonstrated that the CM adsorbed roughly 80% of the total HA content. After 10 days, 36.3% of the initial HA remained on the CM. The in vivo results demonstrated that diabetes significantly reduced the thickness of the CM, while HA had a significant effect on keeping the membrane thickness. HA increased the residual collagen content in the diabetic group (P < 0.0001) but no such effect was observed in the healthy group. Conclusion Immersion of CM in HA prior to the implantation delays membrane degradation in uncontrolled diabetic compared with normoglycemic rats.

Background: Membrane durability is critical for regenerative procedures. We reported previously that type 1-like diabetes in rats accelerates the degradation of collagen membranes and we tested here whether this is associated with increased local production of inflammatory molecules as part of a diabetes-induced chronic inflammation around and within the membranes. Methods: Collagen membrane discs were implanted under the scalp in diabetic (streptozotocin-induced) and control rats, which were sacrificed after 2 or 3 weeks. Total RNA and proteins were isolated from the membrane and its surrounding tissues and the expression and production of six inflammatory molecules (interleukin-6 [IL-6], tumor necrosis factor alpha [TNF ], matrix metalloproteinase [MMP]-9, macrophage migration inhibitory factor [MIF], MIP-1 , and MIP-2) was measured using real-time PCR and western blotting, respectively. Minimal histological analysis of the membranes was conducted to conform to previous studies. Results: Hyperglycemia resulted in reduced membrane thickness (by 10% to 25%) and increased mononuclear infiltrate inside the membrane. mRNA and protein levels of IL-6, TNF , and MMP-9 were elevated in diabetic rats both 2 and 3 weeks postsurgery. The levels (both mRNA and protein) of MIF were increased at 2 weeks postsurgery and those of MIP-1 and MIP-2 at 3 weeks. There was a very good match in the temporal changes of all examined genes between the mRNA and protein levels. Conclusions: Elevated local production of inflammatory cytokines and MMPs, together with apparent mononuclear infiltrate and increased collagenolysis confirm that hyperglycemia leads to a chronic inflammation in and around the implanted collagen membranes, which reduces membrane longevity.

This in vitro preliminary study investigated the attachment of Fusobacterium nucleatum and Porphyromonas gingivalis on titanium alloy healing abutments, which differed in their surface macro-morphology: one was groove-marked while the other was completely smooth. Altogether, twenty implant-healing abutments, ten of each macro-morphology, were evaluated with a single type of bacterial strain. Accordingly, four groups of five abutments each were created. The sterilized healing abutments with the cultured bacteria were placed under anaerobic conditions for 48 h at 37 °C. Afterwards, the abutments were examined with a scanning electron microscope, at a 2500x magnification. Attached bacteria were quantified in the four vertical quarters within the grooved abutments and in the two most coronal millimeters of the smooth abutments. The results were analyzed by applying two-way ANOVA, with square root transformation for a normal distribution. The bacterial attachment of both strains was statistically significantly larger in the grooved abutment areas than on the smooth surfaces (p ≤ 0.0001), twenty times so for Porphyromonas gingivalis and a hundred times so for Fusobacterium nucleatum.