Calcium phosphate/poly(D,L-lactic-co-glycolic acid) composite bone substitute materials: evaluation of temporal degradation and bone ingrowth in a rat critical-sized cranial defect

Objectives: The present study aimed to provide temporal information on material degradation and bone formation using composite (C) bone defect filler materials consisting of calcium phosphate cement (CaP) and poly(d ,l ‐lactic‐co‐glycolic acid) (PLGA) microparticles (20 or 30 wt%) in rat critical‐sized cranial defects. Materials and methods: Critical‐sized bicortical cranial defects were created in 48 rats and CaP/PLGA cement composites were implanted for 4, 8 and 12 weeks (n=8). Results: Histological analysis of the retrieved specimens revealed that implant degradation was significantly faster for C30% (remaining implant up to 89.4 ± 4.4% at 12 weeks) compared with C20% (remaining implant upto 94.8 ± 2.1% at 12 weeks), albeit that overall degradation was limited. Although bone formation was limited in both experimental groups (upto 685765.9 μm² for C20% vs. 917603.3 μm² for C30%), C30% showed a significant temporal increase of total bone formation. The percentage of defect bridging was comparable for C20% and C30% at all implantation periods (range 40 ± 25.5% at week 4 to 65 ± 20% at week 12 for C20%; range 51.8 ± 7.8% at week 4 to 70.5 ± 16.2% at week 12 for C30%). Conclusion: The amount of PLGA‐microparticles in the CaP/PLGA cement composites demonstrated acceleration of material degradation, while bone formation was found not to be influenced. Further optimization of the composite material is necessary to increase control over degradation and tissue ingrowth. To cite this article :
van de Watering FCJ, van den Beucken JJJP, Walboomers XF, Jansen JA. Calcium phosphate/poly(d ,l ‐lactic‐co‐glycolic acid) composite bone substitute materials: evaluation of temporal degradation and bone ingrowth in a rat critical‐sized cranial defect.
Clin. Oral Impl. Res. 23 , 2012; 151–159.
doi: 10.1111/j.1600‐0501.2011.02218.x     

玻璃离子水门汀垫高术在正畸治疗中的应用

对45例安氏错患者在正畸治疗前期(2～5月)应用玻璃离子垫高术,短期内不引起垂直向高度指标的变化、没有明显垂直向改变。这种方法在正畸治疗中短期应用具有可行性。     

前磨牙楔状缺损修复后的抗折裂强度研究

目的研究楔状缺损深及牙齿颊舌径的1/4或1/2的前磨牙采用不同材料充填后牙体的抗折裂强度及牙齿折裂模式。方法收集正畸拔除的新鲜前磨牙60颗,颊侧颈部设计颊舌径1/2和1/4楔状缺损,对1/2深度根管治疗后分别选择复合树脂、复合体或玻璃离子水门汀三种材料充填,运用万能材料试验机对前磨牙颊尖垂直向载力直至牙体断裂。记录牙断裂时的受力数值,并观察断裂模式。结果不同深度的楔状缺损其抗折裂强度不同,但各组间差异无统计学意义(P>0.05)。充填后前磨牙抗折裂强度显著增加(P<0.01),而不同充填材料对牙齿抗折裂强度无显著差异(P>0.05)。结论楔状缺损深及前磨牙颊舌径的1/4以上时容易导致前磨牙折裂。材料充填后可以提高前磨牙的抗折裂能力且与充填材料的种类无关。     

组织工程骨修复兔下颌骨缺损的实验研究

目的:探讨以兔骨髓基质细胞(BMSCs)为种子细胞、纳米羟基磷灰石/胶原(nHAC)为支架材料、兔自体富血小板血浆(PRP)为生长因子,构建组织工程骨修复兔下颌骨缺损能力。方法:兔下颌骨体部15mm×15mm全层骨缺损分别采取:A组,组织工程骨;B组,自体髂骨;C组,单纯nHAC材料;D组,对照组修复。术后1、3、6个月行放射性核素骨检测、骨密度测定及组织学观察。结果:放射性核素骨检测:术后1、3个月,A、B组成骨代谢能力明显优于C、D组,术后6个月时,各组之间骨代谢能力无明显差异;骨密度测定:A、B、C组骨缺损区域骨密度逐渐增加明显高于D组,术后3个月A组、B组骨密度较C组明显提高;组织学检查:A组术后1个月可见小片状类骨质出现,nHAC开始降解,术后3个月时新生骨成大片状结构,术后6个月nHAC几乎全部降解,缺损由骨组织修复,其成骨量与B组无明显差异却明显大于C组,D组仅为纤维组织修复。结论:本实验构建的组织工程骨修复颌骨缺损能力与自体髂骨相似而强于单独使用nHAC,且nHAC材料于体内可完全降解,因此BMSCs与nHAC及自体PRP复合所构建的组织工程骨是一种良好的骨缺损替代材料。     

冷热循环对不同金属与树脂粘接剂粘接强度的影响

目的：冷热循环对不同金属与树脂粘接剂粘接强度的影响。方法：铸造直径分别为4mm和5mm的镍铬合金和纯钛,切割成长度为3mm的标本。2种规格的同种金属标本配对,金属表面经50μmAlzO3喷砂,涂布Al—loy Primer,使用Super—BondC＆B和PanaviaF2种粘接剂粘接。固化后经37℃恒温水浴24h以及10000次冷热循环,测试剪切粘接强度。用spssl7．0统计软件进行统计分析。结果：10000次冷热循环后,镍铬合金与Super—BondC＆B、纯钛与PanaviaF粘接强度显著提高（P〈O．01）,其余各组没有统计学差异。结论：粘接剂的种类对冷热循环前后的粘接强度没有明显影响,金属的种类对冷热循环前后的粘接强度没有明显影响,但是不同金属和不同粘接剂的配伍组合在冷热循环前后的粘接强度变化有统计学意义。     

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纤维桩因其弹性模量与牙本质相当,且具有美观、操作简便等优点,在临床上得到广泛的应用。目前,国内外对纤维桩粘接技术的研究主要集中在纤维桩的表面处理及粘接树脂等方面。本文将对这些方面的研究进展做一综述。     

Push-out bond strength and SEM evaluation of a new bonding approach into the root canal

Objective

This study evaluated the performance of different adhesive systems in fiber post placement aiming to clarify the influence of different hydrophobic experimental blend adhesives, and of one commercially available adhesive on the frictional retention during a luting procedure.

Material and Methods

One luting agent (70 Wt% BisGMA, 28.5% TEGDMA; 1.5% p-tolyldiethanolamine) to cement fiber posts into root canals was applied with 4 different adhesive combinations: Group 1: The etched roots were rinsed with water for 30 s to remove the phosphoric acid, then rinsed with 99.6% ethanol for 30 s, and blotdried. A trial adhesive (base to catalyst on a 1:1 ratio) was used with an experimental luting agent (35% Bis-GMA, 14.37% TeGDMA, 0.5% eDMAB, 0.13% CQ); Group 2: A trial adhesive (base to catalyst on a 1:2 ratio) was luted as in Group 1; Group 3: One-Step Plus (OSP, Bisco Inc.) following the ethanol bonding technique in combination with the luting agent as in Group 1; Group 4: OSP strictly following the manufacturer''s instructions using the luting agent as in Group 1. The groups were challenged with push-out tests. Posted root slices were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under scanning electron microscopy.

Results

Push-out strength was not significantly influenced by the luting agent (p>0.05). No statistically significant differences among the tested groups were found as Group 1 (exp 1 - ethanol-wet bonding technique)=Group 2 (exp 2 - ethanol-wet bonding technique)=Group 3 (OSP - ethanol-wet bonding technique)=Group 4 (control, OSP - water-wet bonding technique) (p>0.05). The dominating failure modes in all the groups were cohesive/adhesive failures, which were predominantly observed on the post/luting agent interface.

Conclusions

The results of this study support the hypothesis that the proposal to replace water with ethanol to bond fiber posts to the root canal using highly hydrophobic resin is plausible, but this seems to be more the proof of a concept than a clinically applicable procedure.     

Micro-shear bond strength of resin cement to dentin after application of desensitizing toothpastes

Abstract

Objectives. The aim of the study was to evaluate the effect of three desensitizing toothpastes on bonding of resin cements to dentin. Materials and methods. The occlusal surfaces of 72 maxillary third molars were ground to obtain flat dentin surfaces and then divided into three groups according to three desensitizing toothpastes used: Sensodyne Rapid Relief (GlaxoSmithKline, SmithKline Beecham Ltd., Slough, UK), Signal Sensitive Expert (Unilever Sanayi ve Ticaret Türk A.?., Ümraniye, ?stanbul, Turkey) and Colgate Sensitive Pro-Relief (Colgate Palmolive, New York, NY). Following bonding of the resin cement (Clearfil? SA Cement, Kuraray Co, Osaka, Japan) to dentin, the specimens were light cured for 40 s with a LED (Elipar S10, 3M Espe, St. Paul, MN). The strength measurements were accomplished with a micro-shear testing machine (Bisco, Schaumburg, IL) at a cross-head speed of 0.5 mm/min until the failure occurs. Failure modes were examined using a stereomicroscope and scanning electron microscope. The data were analyzed with one-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). Results and conclusion. ANOVA revealed that the application of desensitizing toothpastes had significant effects on bond strength of the resin cement tested to dentin (p < 0.05). Mixed failures were observed in all of the groups. Clinical significance. The use of a desensitizing toothpaste before cementation might alter the bond strength of adhesively luted restorations.