Influence of Investment, Disinfection, and Storage on the Microhardness of Ocular Resins

Purpose: The longevity of an ocular prosthesis is directly related to the resistance to erosion of its material. The purpose of this study was to evaluate the effects of chemical disinfection and the method of investment on the microhardness of ocular prosthesis acrylic resin.
Materials and Methods: Thirty-two test specimen investments were obtained in two silicones. A segment was cut in each test specimen, and each specimen was fixed in an acrylic disk. The specimens were then polished and submitted to the first microhardness test before immersion in distilled water and incubation for 2 months. During this 2-month period, the specimens were immersed in a water bath at 37°C and were disinfected daily; half were disinfected with neutral soap and the other half were disinfected with 4% chlorhexidine gluconate. After the storage phase and disinfection, a second microhardness test was performed. The surface microhardness values for the acrylic resins were submitted to ANOVA, followed by the Tukey test.
Results: The disinfection and the period of storage did not statistically influence the surface microhardness of the acrylic resin, independent of the method of investment of the specimens (Zetalabor or Vipi Sil). The investment of specimens with Zetalabor silicone presented a greater surface hardness, independent of the type of disinfection and the period of storage.
Conclusions: Based on these results, we suggest that the microhardness of the resin evaluated was not influenced by the method of disinfection or the time of storage used and was affected only by the investment material.     

The effect of interface adhesion, water immersion and anatomical notches on the mechanical properties of denture base resins reinforced with continuous high performance polyethylene fibres

Previous work has presented a study of the mechanical properties of denture base resins reinforced with a new type of high performance fibre. It is now shown that the substantial improvements demonstrated in those composites remain largely unaffected by a watery environment, anatomical notches, moulding pressure and other factors of denture construction. The understanding of the reinforced resins is here complemented with a detailed study of the interface strength, taking into account the various couplings occurring within the system.     

Effect of post-polymerization heat-treatments on degree of conversion, leaching residual MMA and in vitro cytotoxicity of autopolymerizing acrylic repair resin

Objectives

This study evaluated the effect of post-polymerization heat-treatments on degree of conversion (DC), residual methyl methacrylate concentration (MMA_r) and in vitro cytotoxicity of autopolymerizing acrylic repair resin.

Methods

A total of 336 specimens were prepared by bench- and hydroflask-curing and subjected to post-polymerization heat-treatments: a) water immersion at 60 °C for 30 min, b) microwaving at 500 W for 3 min, c) combined use of water immersion and microwaving d) no treatment (as control). Specimens were eluted in cell culture medium for 1, 2, 5 and 7 days. DC and MMA_r in eluates were measured by FTIR spectrometry and HPLC, respectively. In vitro cytotoxicity of eluates on L-929 fibroblasts was determined by XTT assay. Data were statistically analyzed with Dunn's multiple comparison and Pearson correlation tests (p ≤ 0.05).

Results

DC was highest (99.9%) in bench- and hydroflask-cured groups which were subjected to water immersion. At all elution periods, MMA_r was detected in eluates of all treatment groups and were higher in bench-cured groups than hydro-flask cured groups. Cell proliferation values indicated slightly cytotoxic effect throughout 7 days; regardless of the curing method or post-polymerization treatment. The correlation between MMA_r and cell proliferation was negative after elution of 1, 2, 5 days and was only statistically significant (p < 0.05) at 5 days. At elution of 7 days, the correlation was positive with no significance.

Significance

Post-polymerization heat-treatment of autopolymerizing acrylic repair resin by immersion in water at 60 °C for 30 min is clinically recommended to improve the DC while reducing the leaching residual MMA.     

ZA-1偶联剂对赝复硅橡胶与丙烯酸树脂材料粘接强度的影响

目的：研究ZA-1偶联剂在两种加成型硅橡胶及两种丙烯酸树脂之间交叉使用时粘接强度的影响。方法：选择ZY—1硅橡胶与A-2186硅橡胶分别与临床中常用的热凝丙烯酸树脂和自凝型树脂制成硅橡胶一偶联剂一丙烯酸树脂粘接试件,分别测试试件粘接强度。选择ZY-1组进行热氧老化试验。结果：四组硅橡胶偶联剂粘接系统中,ZY-1硅橡胶与丙烯酸树脂的粘接强度显著高于A-2186组（P〈0．05）。热凝和自凝丙烯酸树脂对粘接系统的粘接强度无显著影响。所有实验组的破坏方式均为内聚破坏。热氧老化处理后ZY-1丙烯酸树脂粘接试件的粘接强度与未老化组相比有显著性提高。结论：丙烯酸树脂材料的种类对粘接强度的影响不大。两种不同的加成型硅橡胶与ZA-1偶联剂交叉使用时粘接强度略有下降,但粘接效果不影响临床使用。热氧加速老化实验使ZY-1加成型硅橡胶与丙烯酸树脂的粘接强度有所提高。     

The Effect of Glass and Polyethylene Fiber Reinforcement on Flexural Strength of Provisional Restorative Resins: An In Vitro Study

The aim is to evaluate and compare the flexural strength of different provisional restorative materials reinforced with glass and polyethylene fibers. A total of 90 samples were prepared and divided into three groups based on the type of fiber reinforcement, unidirectional S-glass (Splint-It) and ultra-molecular weight polyethylene (Ribbond). Unreinforced samples served as control group. Again each group was subdivided into three subgroups based on type of provisional restorative resins, heats cure polymethyl methacrylate, self-cure poly methyl methacrylate and self-cure bis-acryl composite. Samples were loaded in a universal testing machine until fracture occurs. The mean flexural strengths (MPa) were subjected to the one-way ANOVA, followed by the Tukey-HSD test at a significance level of 0.001. The result shows all the fiber reinforced samples possessed greater strength than the control samples. In control samples, the heat cure poly methyl methacrylate resin (72.74 ± 2.28 MPa) had the greatest flexural strength, followed by self-cure bis-acryl composite (67.05 ± 2.35 MPa) and self-cure poly methyl methacrylate resin (52.88 ± 1.90 MPa). In both heat and self-cure poly methyl methacrylate resin, the polyethylene fiber reinforcement (96.00 ± 2.63 MPa, 86.17 ± 1.92 MPa) provides the greatest strength than glass fiber reinforcement (92.68 ± 1.58 MPa, 76.40 ± 2.11 MPa). In self-cure bis-acryl composite, the glass fiber (105.95 ± 3.07 MPa) shows better reinforcement than polyethylene fiber (99.41 ± 1.74 MPa).The fibers reinforcement increases the flexural strength of provisional restorative resins.     

Effect of relining, water storage and cyclic loading on the flexural strength of a denture base acrylic resin

OBJECTIVES: This study investigated the effect of relining, water storage and cyclic loading on the ultimate flexural strength (FS(U)) and on the flexural strength at the proportional limit (FS(Pl)) of a denture base acrylic resin (Lucitone 550-L). METHODS: Rectangular bars of L were made (64 mm x 10 mm x 2 mm) and relined (1.3mm) with four relining resins (Kooliner-K, Ufi Gel Hard-UGH, Tokuso Rebase Fast-TR and New Truliner-NT). In addition, specimens relined with L and intact L specimens were made (64 mm x 10 mm x 3.3 mm). A three-point flexural test was applied on the specimens (n=10) after (1) polymerization; (2) water storage (30 days); (3) cyclic loading (10,000 cycles at 5 Hz) and (4) water storage (30 days)+cyclic loading. Data (MPa) were analyzed with three-way ANOVA and Tukey's HSD tests (alpha=0.05). To test for a possible correlation between FS(U) and FS(Pl), a linear regression coefficient "r" was calculated. RESULTS: After water storage, L-UGH and L-TR demonstrated an increased FS(U) (41.49-50.64 MPa and 49.95-57.36 MPa, respectively) (P<0.05). Only L-TR demonstrated an increased FS(Pl) (20.58-24.21 MPa) after water storage (P<0.05). L-L had the highest FS(U) (between 78.57 and 85.09 MPa) and FS(Pl) (between 31.30 and 34.17 MPa) (P<0.05). The cyclic loading decreased the FS(U) and FS(Pl) of all materials (P<0.05). Regression analysis showed a strong linear correlation between the two variables (r=0.941). CONCLUSIONS: Water storage improved the FS(U) of L-UGH and L-TR and the FS(Pl) of L-TR. L-L produced the highest FS(U) and FS(Pl). The FS(U) and FS(Pl) of all materials were detrimentally influenced by cyclic loading.     

The Art of Dentistry-Odontology.: A Brief Historical Review and an Attempt at Clearing up the two Conceptions

Earlier published measurements of the polymerization shrinkage and water-absorption expansion of plastic filling materials are often difficult to relate to the clinical application of the materials. In the present work an attempt has been made to rectify this situation. The following materials were investigated: Adaptic, Addent XV, Blendànt, Concise, D.F.R., Palakav, capsulated Palakav, TD 71, Palavit 55, Sevriton Simplified and Swedon. The filling materials were placed in cavities cut in extracted teeth. Dimensional changes of the fillings were measured in a microscope. The complete investigation was conducted in a thermostat room maintained at 37°C. The fillings were examined either shortly after initial set or after varying periods of immersion in water. Immediately after initial set a marginal gap at both the enamel and dentin levels of the walls was observed. Polishing the fillings at this time resulted in a zone of fractured enamel 20—40 microns wide. If the fillings were stored in water, the width of the marginal gaps was reduced; for some brands the gaps were completely closed in less than 32 days. Polishing of fillings with closed shrinkage gaps resulted in a minimum of fractures of the enamel margins.     

口腔扁平苔藓与肝病关系的病例对照研究

目的：探讨口腔扁平苔藓与慢性肝病的关系。方法：回顾性分析４７６例口腔扁平苔藓的肝病、肝功能异常发生情况，并与年龄、性别配对的４７６例其它口腔粘膜病及１７１１名健康人比较。结果：口腔扁平苔藓患者慢性肝病发生率６５％，１项肝功能异常发生率为２３．９％，二项或二项以上为５．３％。上述指标均较疾病对照组和正常对照组为高（Ｐ＜０．０１），其中尤以反映间质反应的指标如血清蛋白、ＴＴＴ、ＺｎＴＴ的异常改变较为明显。结论：口腔扁平苔藓与肝病有一定的关系，其所伴发的肝病以慢性肝病疾患为主。     

Effects of Ethanol on the Surface and Bulk Properties of a Microwave-Processed PMMA Denture Base Resin

Purpose: This study evaluated the effect of different concentrations of ethanol on hardness, roughness, flexural strength, and color stability of a denture base material using a microwave‐processed acrylic resin as a model system. Materials and Methods: Sixty circular (14 × 4 mm) and 60 rectangular microwave‐polymerized acrylic resin specimens (65 × 10 × 3 mm³) were employed in this study. The sample was divided into six groups according to the ethanol concentrations used in the immersion solution, as follows: 0% (water), 4.5%, 10%, 19%, 42%, and 100%. The specimens remained immersed for 30 days at 37°C. The hardness test was performed by a hardness tester equipped with a Vickers diamond penetrator, and a surface roughness tester was used to measure the surface roughness of the specimens. Flexural strength testing was carried out on a universal testing machine. Color alterations (ΔE) were measured by a portable spectrophotometer after 12 and 30 days. Variables were analyzed by ANOVA/Tukey's test (α= 0.05). Results: For the range of ethanol‐water solutions for immersion (water only, 4.5%, 10%, 19.5%, 42%, and 100%), the following results were obtained for hardness (13.9 ± 2.0, 12.1 ± 0.7, 12.9 ± 0.9, 11.2 ± 1.5, 5.7 ± 0.3, 2.7 ± 0.5 VHN), roughness (0.13 ± 0.01, 0.15 ± 0.07, 0.13 ± 0.05, 0.13 ± 0.02, 0.23 ± 0.05, 0.41 ± 0.19 μm), flexural strength (90 ± 12, 103 ± 18, 107 ± 16, 90 ± 25, 86 ± 22, 8 ± 2 MPa), and color (0.8 ± 0.6, 0.8 ± 0.3, 0.7 ± 0.4, 0.9 ± 0.3, 1.3 ± 0.3, 3.9 ± 1.5 ΔE) after 30 days. Conclusions: The findings of this study showed that the ethanol concentrations of tested drinks affect the physical properties of the investigated acrylic resin. An obvious plasticizing effect was found, which could lead to a lower in vivo durability associated with alcohol consumption.     

短牙弓对口腔功能的影响

在短牙弓概念被正式提出之后的20余年里，国内外大量研究证实短牙弓能够满足患者口腔咀嚼、美观和舒适等各种口腔功能的需求，同时不影响咬合稳定性和颞下颌关节的稳定性，不损伤牙周支持组织。总之，包括前牙区和前磨牙区的短牙弓被证实能够满足功能性牙列的需求，为后部牙列缺失提供了一种新的修复治疗选择，因此受到各国口腔医师的重视。本文就短牙弓对口腔各功能和牙周支持组织的影响作一综述，以期为临床治疗提供理论依据。