表没食子儿茶素没食子酸酯对乳牙早期釉质龋的再矿化作用

目的 通过体外实验研究,观察天然药物表没食子儿茶素没食子酸酯对乳牙早期釉质龋的再矿化作用.方法 将门诊因乳牙滞留拔除的上颌乳中切牙30颗按照随机数字表分为3组,实验组(表没食子儿茶素没食子酸酯组)、阳性对照组(NaF组)和空白对照组(人工唾液组),每组10颗,进行体外实验.采用显微硬度计测定标本脱矿前后和pH循环后的硬度值,扫描电镜观察乳牙釉质块再矿化后表面形态结构的改变.结果 pH循环后3组乳牙釉质块表面显微硬度组间两两比较差异均具有统计学意义(F=1199.975,P<0.05),阳性对照组和实验组较空白对照组乳牙釉质龋的表面显微硬度高(q=41.986,P<0.05vs实验组;q=68.174,P<0.05vs阳性对照组),但表没食子儿茶素没食子酸酯再矿化效果较NaF低(q=26.188,P<0.05).扫描电镜的结果显示,实验组和阳性对照组在乳牙釉质表面均有大量沉积物存在,空白对照组的乳牙釉质表面呈蜂窝状,凹凸不平,沉积物较少.结论 表没食子儿茶素没食子酸酯在体外实验的研究中,具有促进乳牙早期人工釉质龋再矿化的作用.     

Microstructural Analysis of Severe Bone Lesions in Seven Thalassemic Patients Treated with Deferoxamine

Osteochondrodystrophic lesions, mainly affecting long bone metaphyses, can be radiologically evident in homozygotic thalassemic patients treated with deferoxamine, and their incidence rate varies among authors. The clinical and radiological appearance of these lesions is described in the literature, but microstructural data are still lacking. The aim of our research was to evaluate the microstructure of five tibial biopsy specimens from thalassemic patients with bone lesions (5 cases out of 180 patients followed for the last 10 years, i.e., 2.8%) and two bone biopsy specimens from thalassemic patients with no radiological alteration of the long bones. As control, bone tissue taken from autoptic tibiae of two subjects with no skeletal pathology was used. Using microradiography and X-ray diffraction (XRD), we found a reduced and irregular mineralization of the bone (compared with controls) in thalassemic subjects. Bone tissue microhardness was also significantly reduced. Nevertheless, bone apatite lattice was unaltered and no `foreign' crystallographic phase was recorded by XRD. In conclusion, all the patients shared a similar picture of abnormal bone, even with no radiological evidence of lesion. Received: 28 June 1999 / Accepted: 8 March 2000     

HN-97金属烤瓷外源性着色剂的显微硬度研究

目的 确定HN-97金属烤瓷外源性着色剂的显微硬度并与Shofu stain比较。方法 用HDX-1000型显微硬度计进行测试。结果 该着色剂的显微硬度（Hv）为478.4,与Shofu　stain的显微硬度（Hv）458.2相似,无显著性差异。结论HN-97金属烤瓷外源性着色剂可用于金属烤瓷修复体的外源性着色。     

Influence of dentin pretreatment with 2.5% titanium tetrafluoride on inhibiting caries at the tooth-restoration interface in situ

ObjectiveInvestigate the effects of dentin pretreatment with 2.5% titanium tetrafluoride (TiF₄) aqueous solution followed by two-step self-etching (CLE/Clearfil SE Bond) and one-step self-etching adhesive systems (SBU/Single Bond Universal) on carious lesion inhibition at the tooth-restoration interface using an in situ model.DesignSixty-four cavities at the enamel-dentin junction of dental fragments were randomly distributed according to groups (n = 16): 1) TiF₄ + CLE; 2) TiF₄ + SBU; 3) CLE; 4) SBU. Cavities were restored using resin composite, and placed in intraoral palatal devices used by 16 volunteers for 21 days, to induce caries formation in situ. The fragments were then ground-flat to perform Knoop microhardness tests. Nine indentations were performed on each enamel and dentin substrate, subjacent to the restoration. Analysis of variance and Tukey’s test were applied.ResultsEnamel: groups receiving TiF₄ dentin pretreatment (regardless of adhesive system and tooth-restoration interface distance) presented higher hardness means at a depth of 25 μm from the outer tooth surface (p < 0.0001). Dentin: groups receiving CLE presented higher means when applying TiF₄ pretreatment, whereas groups restored with SBU presented higher means without pretreatment (p = 0.0003).ConclusionsDentin pretreatment with TiF₄ inhibited demineralization of the enamel interface in situ, regardless of the adhesive, and TiF₄ pretreatment followed by CLE application showed higher potential for inhibiting dentin demineralization at the interface.     

Remineralizing efficacy of different calcium-phosphate and fluoride based delivery vehicles on artificial caries like enamel lesions

Objectives

To assess enamel remineralization of different calcium-phosphate and fluoride delivery systems.

Methods

Artificial caries lesions were created on 115 extracted human molars. Specimens were assigned according to remineralizing agent into five groups: G1: Control (artificial saliva), G2: Clinpro™ white varnish, G3: Relief, G4: Tooth Mousse Plus, G5: Vanish™XT. Surface micro-hardness (SMH), surface roughness (R_a) and surface topography by scanning electron microscope (SEM) were evaluated at baseline, after demineralization, after 2 and 4 weeks remineralization and after acid challenge.

Results

Demineralized enamel showed the lowest SMH. By 2 weeks remineralization, SMH were ranked as follows: G2 (282.14 ± 6.82) > G3 (269.37 ± 7.25) > G5 (263.00 ± 6.49) = G4 (251.83 ± 8.26) > G1 (226.5 ± 9.34). However, 4 weeks remineralization showed the following: G2 (304.09 ± 6.65) > G3 (293.1 ± 5.24) = G4 (285 ± 7.29) > G5 (272.43 ± 4.89) > G1 (233.33 ± 9.12). By exposure to acid challenge, groups presented order of: G2 (279.71 ± 5.99) = G3 (275.51 ± 5.59) > G4 (262.29 ± 6.65) > G5 (245.43 ± 6.43) > G1 (190.27 ± 8). Surface roughness showed the following mattress after 2 weeks remineralization: G1 (0.2488 ± 0.0016) = G2 (0.2487 ± 0.0007) = G3 (0.2476 ± 0.0006) > G4 (0.2442 ± 0.0004) > G5 (0.2396 ± 0.0009). After 4 weeks remineralization: G1 (0.2469 ± 0.0017) > G4 (0.244 ± 0.0004) > G5 (0.2413 ± 0.0008) = G3 (0.2405 ± 0.0007) = G2 (0.2399 ± 0.0006). After acid challenge; G1 (0.2582 ± 0.0027) > G5 (0.2556 ± 0.0007) > G4 (0.2484 ± 0.0009) > G3 (0.2463 ± 0.0007) > G2 (0.2443 ± 0.0004). SEM revealed mineralized coating on the surfaces which resists dissolution by acid challenge at variable degrees according to remineralization regimen applied.

Conclusions

Remineralizing agents containing different calcium-phosphate formulas and fluoride have increased remineralization potential compared to artificial saliva. Clinpro™ varnish presented the highest remineralization tendency with greatest resistance for acid challenge.

Clinical significance

This in vitro study imitated the application of different calcium phosphorous and fluoride based delivery vehicles to enamel tooth surfaces in the mouth. The new therapeutic techniques based on different calcium phosphate formulas containing fluoride provide a new avenue for remineralization of non-cavitated and early carious lesions.     

Radiation therapy alters microhardness and microstructure of enamel and dentin of permanent human teeth

Objectives

To evaluate, in vitro, the effects of ionizing radiation on the mechanical and micro-morphological properties of enamel and dentin of permanent teeth.

Methods

Enamel and dentin microhardness (n = 12 hemi-sections) was evaluated at three depths (superficial, middle and deep) prior to (control) and after every 10 Gy radiation dose up to a cumulative dose of 60 Gy by means of longitudinal microhardness. Data were analyzed using two-way analysis of variance and Tukey's test at a significance level of 5%. Enamel and dentin morphology was assessed by scanning electron microscopy (SEM) for semi-quantitative analysis (n = 8 hemi-sections). Data were analyzed using Kruskal–Wallis and Dunn's or Fisher exact tests at a significance level of 5%.

Results

The application of ionizing radiation did not change the overall enamel microhardness, although an increase in superficial enamel microhardness was observed. The micro-morphological analysis of enamel revealed that irradiation did not influence rod structure but interprismatic structure became more evident. Dentin microhardness decreased after 10, 20, 30, 50 and 60 Gy cumulative doses (p < 0.05) compared with non-irradiated dentin, mainly in the middle portion of the tissue. The micro-morphological analysis revealed fissures in the dentin structure, obliterated dentinal tubules and fragmentation of collagen fibers after 30 and 60 Gy cumulative doses.

Conclusions

Although ionizing radiation did not affect the enamel microhardness of permanent teeth as a whole, an increase in superficial enamel microhardness was observed. Dentin microhardness decreased after almost all radiation doses compared with the control, with the greatest reduction of microhardness in the middle depth region. The morphological alterations on enamel and dentin structures increased with the increase of the radiation dose, with a more evident interprismatic portion, presence of fissures and obliterated dentinal tubules, and progressive fragmentation of the collagen fibers.

Clinical significance

This study shows that irradiation affects microhardness and micro-morphology of enamel and dentin of permanent teeth. The effects of gamma irradiation on dental substrate might contribute to increased risk of radiation tooth decay associated with salivary changes, microbiota shift and high soft and carbohydrate-rich food intake.     

三种氟化物增强乳牙釉质抵抗饮料酸蚀和再矿化作用的研究

目的观察三种氟化物处理后的乳牙釉质表面抵抗软饮料酸蚀及促进受损牙釉质再矿化的能力。方法应用显微硬度仪和扫描电镜,观测分别用NaF溶液、氟保护剂、双氟脱敏剂处理后再经饮料浸泡的乳牙釉质表面的显微硬度值(surfacemicrohardness,SMH)及形态的变化。结果饮料浸泡后,各组乳牙釉质的SMH均有明显降低;氟化物处理组的釉质SMH降低的程度明显低于对照组(P<0.001);氟保护剂和双氟脱敏剂组釉质SMH的降低无显著性差异,而低于单纯的NaF溶液组;扫描电镜可见釉质表面有不同程度的溶解。饮料侵蚀后又经氟化物再矿化的乳牙,釉质SMH明显增加,其中双氟脱敏剂组的釉质SMH增加最明显。结论釉质表面应用氟化物,能明显增强乳牙釉质抵抗软饮料酸蚀,并能促进受损牙釉质的再矿化修复能力,其中双氟脱敏剂的作用最明显。     

Ion release and enamel remineralizing potential of miswak,propolis and chitosan nano-particles based dental varnishes

Purpose

Natural products can have an important role in caries control through their inherent biological abilities.

THE EFFECT OF DIFFERENT LIGHT-CURING UNITS ON TENSILE STRENGTH AND MICROHARDNESS OF A COMPOSITE RESIN

The aim of this study was to evaluate the influence of different light-curing units on the tensile bond strength and microhardness of a composite resin (Filtek Z250 – 3M/ESPE). Conventional halogen (Curing Light 2500 – 3M/ESPE; CL) and two blue light emitting diode curing units (Ultraled – Dabi/Atlante; UL; Ultrablue IS – DMC; UB3 and UB6) were selected for this study. Different light intensities (670, 130, 300, and 600 mW/cm², respectively) and different curing times (20s, 40s and 60s) were evaluated. Knoop microhardness test was performed in the area corresponding to the fractured region of the specimen. A total of 12 groups (n=10) were established and the specimens were prepared using a stainless steel mold composed by two similar parts that contained a cone-shaped hole with two diameters (8.0 mm and 5.0 mm) and thickness of 1.0 mm. Next, the specimens were loaded in tensile strength until fracture in a universal testing machine at a crosshead speed of 0.5 mm/min and a 50 kg load cell. For the microhardness test, the same matrix was used to fabricate the specimens (12 groups; n=5). Microhardness was determined on the surfaces that were not exposed to the light source, using a Shimadzu HMV-2 Microhardness Tester at a static load of 50 g for 30 seconds. Data were analyzed statistically by two-way ANOVA and Tukey''s test (p<0.05). Regarding the individual performance of the light-curing units, there was similarity in tensile strength with 20-s and 40-s exposure times and higher tensile strength when a 60-s light-activation time was used. Regarding microhardness, the halogen lamp had higher results when compared to the LED units. For all light-curing units, the variation of light-exposure time did not affect composite microhardness. However, lower irradiances needed longer light-activation times to produce similar effect as that obtained with high-irradiance light-curing sources.     

Impact of thermocycling on surface roughness,microhardness and optical properties of three different lithium disilicate ceramics

ObjectivesThis investigation was carried out to examine the influence of thermocycling aging on the surface roughness (R_a, µm), color parameters (L*, a*, b*), lightness change (ΔL*), chroma change (ΔC*_ab), color change (ΔE), and microhardness (VH) of three lithium disilicate ceramics.Materials and methodsForty-five specimens were prepared from three lithium disilicate materials (n = 15)—e.max CAD (EC), e.max Press (EP), and GC Initial LiSi Press (LP) ceramics—with dimensions of 6.0 × 1.2 × 16.0 ± 0.2 mm following the manufacturers’ instructions. All specimens were exposed to 5000 thermal cycles with bath temperatures ranging between 5 °C and 55 °C. Data of surface roughness, color parameters, and microhardness were obtained using an optical profiler, a spectrophotometer, and a Vickers hardness tester, respectively. One-way ANOVA, a post-hoc Tukey’s test, and a paired sample t-test were implemented for statistical analysis (p ≤ 0.05).ResultsFor surface roughness, insignificant differences were reported between the materials either before or after thermocycling (p > 0.05) while each material displayed a significant increase after being subjected to thermocycling (p < 0.05). For color parameters, LP showed significantly lower L* and b* after thermocycling while EC presented a significant reduction in a* in comparison with other materials (p < 0.05). EP showed a significant decrease in ΔL*, ΔC*_ab and ΔE compared with other materials (p < 0.05). Regarding microhardness, LP showed significantly increase value in comparison with other materials (p < 0.05).ConclusionsThermocycling had a major impact on the surface roughness, microhardness and optical characteristics of the tested materials. E.max Press displayed less changes in (ΔL*), (ΔC*_ab) and (ΔE), while GC LiSi Press had better behavior in terms of microhardness.