Polymer-assisted regeneration therapy with Atrisorb barriers in human periodontal intrabony defects

AIM: This study compared clinical results of 40 periodontal osseous defects treated by two types of absorbable barrier materials. MATERIAL AND METHODS: Thirty patients (23 males and seven females) suffering from moderate to advanced periodontitis (with comparable osseous defects) were randomly assigned to receive either Atrisorb barrier (n = 22; group A) or Resolut XT barrier (n = 18; group B) therapy. Periodontal phase I treatment and oral hygiene instruction were performed before periodontal surgery. Papillary preservation, partial thickness flap, citric acid root conditioning, and decortication procedures were applied during the operation. Bone defects were filled with demineralized freeze-dried bone allograft and minocycline mixture (4:1 ratio). Postoperative care included 0.10% chlorhexidine rinse daily and antibiotic medication for 2 weeks. Clinical assessments including probing depth (PD), clinical attachment level (CAL), gingival recession (GR), plaque index (PII), gingival index (GI), and radiographic examinations were taken at the baseline, preoperatively and at 3 and 6 months after regenerative surgery. RESULTS: Six months following therapy, both Atrisorb and Resolut XT groups had achieved comparable clinical improvement in pocket reduction (3.9 versus 4.4 mm), attachment tissue gain (clinical attachment gain; 3.5 versus 3.6 mm), and reduction in the GI and in the PII. Within-group comparisons showed significant attachment gain and pocket reduction between baseline data and those at both 3 and 6 months postoperatively (p < 0.01). There were no statistically significant differences in any measured data between groups A and B. CONCLUSIONS: The results of this study indicate that a comparable and favorable regeneration of periodontal defects can be achieved with both Atrisorb and Resolut XT barriers. Further long-term study and histologic observations of tissue healing are needed to evaluate whether Atrisorb is promising for clinical use.     

Thermal Properties and Degradation Behavior of Linear and Branched Poly(L‐lactide)s and Poly(L‐lactide‐co‐glycolide)s

Poly(lactide)s and poly(lactide‐co‐glycolide)s with different number of arms are synthesized from L ‐lactide and glycolide monomers using stannous(II) 2‐ethylhexanoate and alcohols containing 1, 2, 25, and 51 hydroxyl groups. 1‐dodecanol is used to produce the 1‐arm polymer, poly(ethylene glycol) for the 2‐arm polymer, and polyglycidols of appropriate molecular weight are used to initiate the 25‐ and 51‐arm branched polyesters. The polymers are characterized by ¹H NMR and GPC. The thermal properties of the polymers are studied using DSC. Their degradation behavior is indestigated using a combination of thermogravimetry, FTIR spectroscopy, and isoconversional kinetic analysis.     

Polylactides Bearing Vanillin at Chain End Provided Dual Dynamic Interactions: Stereocomplex Formation and Nanostructure Control

The chemical modification of the polymer chain end group of polylactide is important for the development of nanostructural materials. Herein, the first example of dual dynamic functionality in polylactides bearing vanillin at the chain end is first demonstrated. The first function, stereocomplex formation of both enantiomeric polymers, results in an enhancement in thermal resistance, while the second creates reversibility through amine–imine transformation. This transformation self‐assembles into interesting morphologies, including raindrop‐like nanoparticles observed on imine formation, and spider‐web‐like fibrous ones observed on aldehyde formation from hydrophobic–hydrophilic stimuli by acid. These properties indicate that the present polymer shows dual dynamic building block moiety properties, composed of the natural products.

     

聚乳酸-聚乙二醇单甲醚共混体系的调制DSC分析

采用调制差示扫描量热法(MDSC)研究了聚乳酸(PLA)与聚乙二醇单甲醚(MPEG)共混体系的热性能。研究结果表明,MDSC可有效分辨PLA重结晶和熔融的重叠效应,在测试条件下,PLA的α'-α晶型转变与α晶体的熔融几乎同时进行。随着升温速率的加快和调制周期的延长,当增塑剂的质量分数为15%时,PLA-MPEG共混物分割在不可逆曲线的重结晶焓逐渐升高(最高约28 J/g),熔融焓逐渐降低(最低约为3.3 J/g);分割在可逆曲线的熔融峰逐渐由多重峰变为单峰,且焓变值逐渐升高(最高约66.1 J/g),相应的可逆曲线熔融分割比例达到了95.2%。通过提高升温速率和延长调制周期,可使大部分熔融分割在可逆曲线上,但过快的升温速率和过长的调制周期会导致PLA相转变时的周期数过少,DSC调制功能的分辨率下降,设置测试条件时需综合考虑。     

Alveolar ridge augmentation with a prototype trilayer membrane and various bone grafts: a histomorphometric study in baboons

Barrier membranes have become a standard treatment option in alveolar ridge augmentation prior to implant placement. However, non-resorbable membranes require secondary surgery and resorbable membranes show an unfavorable degradation profile. The purpose of this study was to evaluate the potential of a slowly biodegradable/bioresorbable prototype trilayer membrane (PTLM) for supporting bone regeneration in alveolar ridge augmentation. Clinically relevant cavities were made 3 months after the extraction of the first and second molars in each jaw of six baboons. Each animal was treated with four different regimens: (1) autogenous bone block (ABB) alone, (2) ABB+PTLM, (3) deproteinized bovine bone mineral (DBBM)+PTLM and (4) no treatment. After 9 months, the baboons were sacrificed and block sections of the augmented area were subjected to histologic and histomorphometric analyses. Newly formed bone areas were determined at a distance of 1, 3, 7 and 10 mm from crestal. The data showed a well-preserved ridge profile at the membrane-protected sites, whereas non-protected bone blocks and control sites underwent severe resorption resulting in knife-edge ridge profiles. Significant differences were found between ABB+PTLM and ABB (P=0.0137-0.0232). DBBM+PTLM also produced a larger bone area compared with ABB alone (P=0.0396-0.0439). No significant difference in bone area was detectable between ABB+PTLM and DBBM+PTLM (P>0.05). The present study supports the use of the slowly biodegradable/bioresorbable PTLM with autografts and DBBM for lateral ridge augmentation in this type of bone defects.     

A simple and high production rate manufacturing method for submicron polymer fibres

The manufacturing technique for cotton-candy floss, heat-aided rotary jet-spinning, was used to produce submicron-scale fibrous meshes by using bioabsorbable thermoplastic polymers. The method was feasible for 100 wt% polymer concentrations functioning completely without solvents. It was possible to produce submicron diameter fibres using a simple device, which indicates that this manufacturing method is a very promising technique for obtaining high-throughput rates for submicron, and possibly nano-scale, fibrous meshes.     

Crystallization of Poly(L‐/D‐Lactide) in the Presence of Electric Fields

We report, for the first time, an enhancement in melt crystallization kinetics of poly(L ‐/D ‐lactide) (a type‐A1 polymer) in the presence of static electric fields as observed through measurement of the complex viscosity. Static electric fields of varying intensity (0–2.4 × 10⁵ V m^?1) are applied directly to the crystallizing polylactide melt at five different temperatures. The crystallization rate enhancement increases both with crystallization temperature and applied electric field intensity. An XRD analysis and optical microscopy studies allows us to attribute this to increased nucleation in the presence of an electric field. A technique allowing for the estimation of the rate of homogeneous nucleation induced by the electric field is developed.     

Biocompatibility and in vivo degradation of chitosan based hydrogels as potential drug carrier

Carboxymethyl chitosan-graft-polylactide (CMCS-PLA) and carboxymethyl chitosan (CMCS) hydrogels were prepared by using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) as crosslinking agent and catalyst at room temperature. The biocompatibility of the hydrogels was evaluated with the aim of assessing their potential as drug carrier. Various aspects of biocompatibility were considered, including MTT assay, agar diffusion test, release of lactate dehydrogenase (LDH), hemolytic test, plasma recalcification time (PRT), and dynamic clotting time. MTT assay showed that the cytotoxicity level of both hydrogels to L-929 cells was 0 or 1. The LDH release of CMCS and CMCS-PLA was 26 and 29%, respectively, which is slightly higher than that of the negative control (21%) and much lower than that of the negative control (87%). The hemolysis ratio of CMCS and CMCS-PLA was 1.4 and 1.7%, respectively, suggesting outstanding anti-hemolysis properties of both materials. The PRT value of CMCS and CMCS-PLA was higher by 77 and 99% than the value of the positive control. All the results revealed that the hydrogels present good cytocompatibility and hemocompatibility in vitro. In vivo degradation and tissue compatibility were evaluated by subcutaneous injection in the dorsal area of rats. CMCS and CMCS-PLA hydrogels were completely degraded and the inflammatory response also completely disappeared around hydrogels after 19 days in vivo. It is thus concluded that hydrogels formed of CMCS and CMCS-PLA with outstanding biocompatibility are promising as potential drug carrier.