Occlusive effects of lactic acid-glycolic acid copolymer membrane on gingival fibroblasts in vitro

The effect of collagen membrane and of bone substitute on lateral bone augmentation with titanium mesh: An experimental in vivo study

AIM

The aim of this study was to identify the additional effects of collagen membrane (CM) and of synthetic bone substitute (BS) on lateral bone augmentation of chronic peri-implant defect with titanium mesh (TM).

MATERIALS AND METHODS

Atrophic alveolar ridge was induced in 6 canine mandibles and 5 peri-implant defects were achieved in each hemi-mandible. Bone augmentation was attempted using the following randomly allocated modalities: 1) Control: no treatment, 2) TM only group: blood clot covered by TM, 3) TM+BS group: BS covered by TM, 4) TM+CM group: blood clot covered by TM and CM, and 5) TM+BS+CM group: BS covered by TM and CM. After 16 weeks of submerged healing, micro-CT and histomorphometric analyses were performed.

RESULTS

TM exposure occurred in one case in the TM only group, one case in the TM+CM group, and two cases in the TM+BS+CM group. Histologically, pseudo-periosteum was observed along the inner and outer surfaces of TM, and the directions of the collagen fiber within the pseudo-periosteum differed according to the additional use of CM. In general, the TM only group rendered higher values in vertical defect fill and dimension of the augmented hard tissue in comparison to the other treatment groups.

CONCLUSIONS

Due to the small sample size, this pilot study remains inconclusive. Within the limitations of the study, the use of CM and/or BS did not appear to have an additional benefit on lateral bone augmentation of peri-implant defect with TM.

Periodontal tissue regeneration by transplantation of rat adipose-derived stromal cells in combination with PLGA-based solid scaffolds

Regeneration of damaged periodontium is challenging due to its multi-tissue composition. Mesenchymalstem cell-based approaches using adipose-derived stromal cells (ASCs) may contribute to periodontal reconstruction, particularly when combined with the use of scaffolds to maintain a space for new tissue growth. The aim of this study was to assess the regenerative potential of ASCs derived from inbred or outbred rats in combination with novel solid scaffolds composed of PLGA (Poly D,L-lactic-co-glycolic acid) (PLGA-scaffolds). Cultured ASCs seeded onto PLGA scaffolds (ASCs/PLGA) or PLGA-scaffolds (PLGA) alone were transplanted into periodontal fenestration defects created in F344 or Sprague Dawley (SD) rats. Micro-CT analysis showed a significantly higher percentage of bone growth in the ASCs/PLGA groups compared with the PLGA-alone groups at five weeks after surgery. Similarly, histomorphometric analysis demonstrated thicker growth of periodontal ligament and cementum layers in the ASCs/PLGA-groups compared with the PLGA-alone groups. In addition, transplanted DiI-labeled ASCs were observed in the periodontal regenerative sites. The present investigation demonstrated the marked ability of ASCs in combination with PLGA scaffolds to repair periodontal defects.

Collagen-coated poly(L-lactide-co-ɛ-caprolactone) film: a promising scaffold for cultured periosteal sheets

BACKGROUND

We previously demonstrated that human periosteal sheets prepared on culture dishes function as an osteogenic "graft material" applicable to periodontal regenerative therapy. However, a lower level of initial adhesion of the excised periosteum tissue segments to culture dishes was a critical point that compromised the successful preparation of functional periosteal sheets. To improve on this weakness, we developed a transparent, biodegradable poly(L-lactide-co-ɛ-caprolactone) (LCL) film and tested its function as a scaffold and carrier of periosteal sheets.

METHODS

Human periosteum tissue segments excised from alveolar bone of healthy donors were cultured on type I atelocollagen-coated LCL films. Initial adhesion was examined by simple agitation. Cell outgrowth and in vitro mineralization were cytohistochemically examined. Osteogenic activity was histochemically examined in an animal implantation model using nude mice.

RESULTS

Surface collagen-coating modified the hydrophobic nature of LCL and substantially improved the initial adhesion. Compared to cultures in plastic dishes, the growth rate was delayed in non-coated films, but not in collagen-coated films. In the trimming process for animal implantation, periosteal sheets were frequently detached from non-coated films, but not from collagen-coated films. Regardless of collagen-coating, LCL films did not cause any significant infiltration of inflammatory cells, or negatively impact mineralized tissue formation.

CONCLUSIONS

Collagen-coating improved the initial adhesion of periosteum segments, which facilitated cell outgrowth and also handling efficiency on implantation. Therefore, we believe that once evaluated in human studies, our collagen-coated LCL film will contribute to improving the periodontal regenerative methodology with the application of cultured autologous periosteal sheets.

The effects of naproxen sodium on specific parameters of L-strain cells over guided bone regeneration barrier materials

There is strong evidence that nonsteroidal antiinflammatory drugs (NSAID) may exert a significant antiproliferative effect. This study evaluated the influence of NSAID on specific parameters of fibroblastic cells, in vitro, over two-guided bone regeneration (GBR) barrier materials. Fibroblast cells were cultured on bioabsorbable membrane made of collagen (Bio-Gide(R)- BG) and the most common nonresorbable membrane which is made of expanded polytetrafluoroethylene (ePTFE, Gore-Tex(R)- GT). Naproxen sodium (10 mM) was used as an analgesic drug. The fibroblast cells were cultured in vitro for 24 h and examined by scanning electron microscopy (SEM). Cells were cultured in the presence of (3)H-thymidine to study cell proliferation. And also cell numbers and viabilities were measured. The difference between the means for each group were analyzed for statistical significance by Kruskal-Wallis one-way ANOVA followed by post hoc comparisons using the Dunn statistical method. Of all the six groups, the control group stimulated DNA synthesis more than the others. With respect to cell numbers, there was statistically significant difference between the control group and naproxen planted BG membrane group. The interpretation of our SEM images is that these two barriers and naproxen seem to have had the least effect on cellular morphology. These data suggest naproxen have an inhibitory effect on stimulation of DNA synthesis, cell numbers and viabilities. And also lacking adherence of cells to the membranes may be due to the physical properties of the materials.

A composite polymer/tricalcium phosphate membrane for guided bone regeneration in maxillofacial surgery

The aim of the study was the development of a resorbable membrane for guided bone regeneration (GBR) with improved biocompatibility, which should be stiff enough to avoid membrane collapse during bone healing. Combining a bioactive ceramic with a resorbable polymer may improve the biocompatibility and osteoconductivity of resorbable devices. The present article describes the preparation, the mechanical properties, and the in vitro degradation characteristic of a composite membrane made of poly(L, DL-lactide) and alpha-tricalcium phosphate in comparison to a membrane made of pure poly(L, DL-lactide). The tensile strength and the elastic modulus as well as the molecular weight of the membranes were measured after in vitro degradation in buffer at 37 degrees C up to 28 weeks. The initial tensile strength of the composite and the polymer membrane was 37.3 +/- 2.4 MPa and 27.7 +/- 2.3 MPa and the elastic modulus 3106 +/- 108 MPa and 3101 +/- 104 MPa, respectively. The mechanical properties remained constant up to 8 weeks and then decreased slowly until week 28. The molecular weight of both membranes decreased steadily from 170,000 D to 30,000 D. It was concluded that the mechanical requirements for a membrane for GBR were fulfilled by the composite membrane.

Degradable poly(anhydride ester) implants: effects of localized salicylic acid release on bone

Degradable poly(anhydride ester) implants in which the polymer backbone breaks down into salicylic acid (SA) were investigated. In this preliminary work, local release of SA from the poly(anhydride esters), thus classified as 'active polymers', on healthy bone and tissue was evaluated in vivo using a mouse model. Degradable polyanhydrides that break down into inactive by-products were used as control membranes because of their chemical similarity to the active polymers. Small polymer squares were inserted over the exposed palatal bone adjacent to the maxillary first molars. Active polymer membranes were placed on one side of the mouth, control polymers placed on the contra lateral side. Intraoral clinical examination showed that active polymer sites were less swollen and inflamed than control polymer sites. Histopathological examination at day 1 showed essentially no difference between control and active polymers. After 4 days, active polymer sites showed epithelial proliferation to a greater extent than the polyanhydride controls. After 20 days, active polymer sites showed greater thickness of new palatal bone and no resorptive areas, while control polymer sites showed less bone thickness as well as resorption including lacunae involving cementum and dentine. From these preliminary studies, we conclude that active polymers, namely poly(anhydride esters), stimulated new bone formation.