Preparation of low shrinkage stress Bis-GMA free dental resin composites with a synthesized urethane dimethacrylate monomer

A new urethane dimethacrylate TMA was synthesized through a typical urethane reaction. TMA was used to replace 1,6-bis(methacryloxy-2-ethoxycarbonyl- amino)-2,4,4- trimethylhexane (UDMA) in UDMA based composite partially or totally to prepare TMA containing composites. Critical properties of TMA containing composites were investigated. 2,2-bis[4(2-hydroxy-3-methacryloy- propyloy)phenyl]propane (Bis-GMA) based and UDMA based composites were used as references. FT-IR and ¹H-NMR confirmed the structure of TMA. All of experimental dental resin composites had the similar double bond conversion (p?>?0.05). With a certain amount of TMA, TMA containing composites could have lower volumetric shrinkage (p?<?0.05) and shrinkage stress (p?<?0.05) than control groups. Water sorption, solubility, flexural strength and modulus of TMA containing composites were not worse than those of control groups. All of TMA containing composites and UDMA based composite had the same fracture toughness (p?>?0.05), which was higher than that of Bis-GMA based composite (p?<?0.05). TMA has potential as Bis-GMA substitute to prepare Bis-GMA free dental resin composites with low shrinkage stress.     

HAB/DBP 复合物修复骨缺损的实验研究

目的：研究羟基磷灰石人工骨（HAB）/异体脱矿骨粉（DBP）复合物修复骨缺损的效果，以期获得一种既具有传导性又具有骨诱导性的复合材料。方法：将HAB/DBP复合物、HAB、异体脱矿骨(DMB)植入兔桡骨中段骨缺损处，设置空白对照，在2、4、8、12周分别取材，观察新骨形成及骨缺损修复情况。结果：HAB/DBP组、DMB组2周时可见骨断端附近有大量软骨细胞聚集，并有少量基质形成。4周时，大量软骨细胞及少量骨小架。8周时，见大量骨小梁和层板状骨形成。12周见层板成熟骨组织和哈佛系统形成。其成骨能力及新骨生成量明显高于HAB组及空白组。结论：HAB/DBP复合物为一种既具有骨传导性又具有骨诱导性的骨缺损修复材料，具有与DMB同样的诱导骨生成的能力，可能成为一种具有临床应用前景的骨缺损及修复材料。     

Spatially resolved assessments of composite shrinkage in MOD restorations using a digital-image-correlation technique

Objectives

To analyze the influence of cavity geometry and lining materials in MOD composite restorations by characterizing the polymerization shrinkage and cusp deflection.

Methods

Eighty intact molars with similar sizes were collected and randomly divided into eight groups. MOD cavities with various widths and depths were prepared on these teeth: Group I, 2_(W) × 2_(D) mm; Group II, 4_(W) × 2_(D) mm; Groups III, IIIf, IIIg, 2_(W) × 4_(D) mm; and Groups IV, IVf, IVg, 4_(W) × 4_(D) mm. In Groups IIIf and IVf, flowable composite liner was placed prior to composite restoration, while glass-ionomer liner was used in Groups IIIg and IVg. Deformations of restorations resulted from composite shrinkage were recorded for 30 min following light irradiation using a digital-image-correlation (DIC) method to subpixel level. The displacements at the boundaries of the restorations were analyzed using one-way ANOVA and the post hoc test at a 5% significance level. The correlation between the geometric factors and the displacements was also analyzed.

Results

The inward displacements on free surfaces were greater than those on the bonded surfaces. Groups with flowable composite linings showed greater amount of displacements on free and bonded surfaces compared to the unlined and glass ionomer lining groups. The correlation analysis showed that the free surface shrinkage was related with the cavity width and C-factor, while cusp deflections were correlated with the cavity depth and the cusp compliance.

Significance

The DIC technique measures composite shrinkage on different boundaries of restorations to facilitate the investigation of polymerization kinetics. Using flowable composite lining and increased cusp depth may aggravate the cusp flexure.     

The efficacy of Xialine<Superscript>®</Superscript> in patients with Sjögren’s syndrome: a single-blind,cross-over study

Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease of unknown cause whose main characteristic is severe dryness of the eyes and the mouth. The decreased functional capacity of the lacrimal and salivary glands which is the result of the inflammatory process and lymphocytic infiltration observed in SS is accountable for this complication. Twenty-nine patients with SS whose ages were ranging between 24–77, who were under treatment in Ege University Faculty of Medicine Department of Rheumatology, participated in the study, and their informed consents were obtained upon enrollment. Each patient recorded their subjective complaints on a separate questionnaire. The baseline and subsequent evaluation of the subjective findings on predetermined times (1 h after application of the material, at the end of the 1st, 7th, and 14th days) were also recorded on separate questionnaire sheets. Throughout the 14-day treatment period, no statistically significant differences were noted between the Xialine® and placebo groups with regard to burning tongue, diminished taste, and waking up at night to sip water (p?=?0.925, 0.527, and 0.066, respectively). However, patients’ satisfaction with placebo decreased by 25.63% at the end of the test period, whereas it increased by 16.37% after Xialine® administration. Overall, the patients preferred Xialine® at the end of the study (p?=?0.011). The main motive to administer saliva substitute is to improve lubrication and hydration of oral tissues. The results of this study indicated that Xialine® is helpful in the management of xerostomia-related symptoms of SS patients. However, further investigations in larger scale group of patients are recommended to provide the effects of these agents on various complaints of xerostomia.     

大锥度牙胶尖热收缩性能的评价

目的观察4种不同品牌的0.06锥度的牙胶尖的热收缩性能。方法将4种牙胶尖末端固定在同一带刻度的平板上,尖端处于同一水平线,此水平线作为读数的零点,从30℃开始记录其长度变化;根据加热介质分为:A组,水浴加热;B组,甘油浴加热,采用Spss 13.0 for windows(English version)统计软件对结果进行相关分析。结果在50℃时4种不同品牌的牙胶尖都可以发生体积变化。牙胶尖的长度变化和温度具有明显的相关性。各牙胶尖之间的差别无统计学意义。不同的加热介质所出现不同的尺寸变化有统计学意义。结论4种不同品牌的牙胶尖分别在蒸馏水和甘油中加热,在50℃以上出现发生不同的热收缩,其在不同介质中发生变化不尽相同,提示在临床中不同根管封闭剂时可能发生不同的热收缩。     

脱细胞气管基质及PGA膜细胞生物相容性比较研究

目的:采用体外细胞培养的方法,对自制的家兔、SD大鼠脱细胞气管基质材料、PGA膜的细胞生物相容性进行比较研究,探讨脱细胞基质用作组织工程化人工涎腺样组织体外构建研究所需支架材料的可能性。方法:取新生SD大鼠颌下腺细胞,经体外培养扩增后,将传代的颌下腺腺细胞接种在上述3种材料上进行体外培养,对材料上的细胞进行形态学、细胞增殖情况、材料/细胞培养上清液中α-淀粉酶含量进行观察或检测。结果:涎腺细胞均能在气管基质材料及PGA膜上黏附、生长。以天然气管衍生材料更佳。结论:脱细胞气管基质材料是一种细胞生物相容性良好的支架材料,可用于组织工程化涎腺样组织体外构建的实验研究。     

Can hygroscopic expansion compensate polymerization shrinkage? Part I. Deformation of restored teeth

Objective

Restorative materials exhibit contraction and expansion due to polymerization and water absorption. Each process deforms and stresses a restored tooth structure in opposite direction. This study evaluated the tooth deformations during these competing processes.

Methods

Large MOD cavities were prepared in 10 extracted molars. Five were restored with a hydrophobic resin composite (Filtek Supreme, 3M ESPE) and the others with a hydrophilic resin-modified glass-ionomer (Ketac Nano, 3M ESPE). The restored molars and two unrestored controls were stored in water for 24 weeks. The molars were digitized with an optical scanner at baseline, after preparation, restoration, and at 1, 2, 4, 8, 16, and 24 weeks water immersion. The digitized buccal, lingual, and restoration surfaces were analyzed to determine their deformation patterns. The results were statistically analyzed using ANOVA followed by Student-Newman-Keuls post hoc tests (p = 0.05).

Results

The buccal and lingual tooth surfaces moved 13-14 μm inward after restoration. After water immersion, cuspal deformation in the resin composite group gradually decreased, reversing the shrinkage deformation within four weeks. The immersed resin-modified glass ionomer group reversed shrinkage deformation within one week, and continued to expand further to 28 μm after 24 weeks. Cuspal deformations after water immersion were significantly different with the two restoratives. Restoration surfaces also expanded after water immersion, while the control teeth showed no significant deformation.

Significance

Polymerization shrinkage deformation was compensated by hygroscopic expansion within 4 weeks in teeth restored with a hydrophobic resin composite, while a hydrophilic restorative over-compensated polymerization shrinkage within 1 week causing tooth expansion.     

不同包埋材料及方法对钴铬合金铸造收缩的影响

目的比较不同包埋材料和包埋方法对铸造钴铬合金全冠收缩的影响。方法制作相同的96个全冠蜡型。选用三种磷酸盐包埋材料分别进行有圈包埋和无圈包埋,用钴铬合金铸造。测量铸件边缘内径并用SPSS统计学软件对数据进行分析。结果不同包埋材料对铸件收缩具有显著性差异(P<0.01)。有圈包埋和无圈包埋对铸件收缩也具有显著性差异(P<0.01)。结论不同包埋材料对铸造收缩影响不同,无圈包埋时的铸造收缩小于有圈包埋。     

粉浆涂塑渗透陶瓷烧结线性收缩率的测定

制作４０个渗透陶瓷样本测定粉浆涂塑渗透陶瓷的氧化铝烧结及玻璃料渗透的两个烧结阶段的线性收缩率。结果表明，渗透陶瓷烧结完成后的线性收缩率为０．０８％＿０．３２％。收缩主要发生于氧化铝的烧结过程，此过程的收缩率为０．２０％，而玻璃料的渗透烧烤过程 不引起长度的明显变化。