正常唾液及氟化物对脱矿年轻恒牙牙釉质的再矿化作用

目的:用显微硬度测量法研究正常人体唾液及氟化物对碳酸饮料酸蚀的年轻恒牙牙釉质的再矿化作用。方法:收集口腔正畸门诊减数拔牙所拔除的新鲜、健康年轻恒牙23颗,制成牙釉质样本90块,随机分为对照A组、实验B组及实验C组;每组又分为三个亚组(A1、A2、A3、B1、B2、B3、C1、C2、C3),其中A1、B1、C1浸泡在雪碧中1周、A2、B2、C2浸泡在芬达中1周、A3、B3、C3浸在百事可乐中1周,每组10个牙块。A组牙浸泡完后直接用显微硬度仪做表面硬度测试;B组牙用蒸馏水冲洗干净后分别浸泡于装有正常人体唾液的容器中,将容器置于37℃恒温箱中,定期摇动容器,1月后取出用显微硬度仪做表面硬度测试;C组牙则用蒸馏水冲洗干净后,每日早中晚3次用含氟牙膏涂布牙齿开窗处表面10 min,再分别放入装有正常人体唾液的容器中,将容器置于37℃恒温箱中,定期摇动容器,1月后取出用显微硬度仪做表面硬度测试。结果:正常人体唾液及氟化物均能使脱矿后年轻恒牙牙釉质表面硬度明显升高(P<0.05),且两者之间有统计学差异(P<0.05)。结论:正常人体唾液及氟化物对脱矿年轻恒牙的再矿化作用明显。     

Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ

Objectives

The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge.

Methods

In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR – Z250) or resin-modified glass ionomer (RMGI – Vitremer). Two phases of 14 days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100 μg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL).

Results

All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation = 8.9 and with biofilm accumulation = 25.6, CR without biofilm accumulation = 14.7 and with biofilm accumulation = 17.0.

Conclusion

Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin.

Clinical significance

The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin.     

五倍子水提取物对根管显微硬度的影响

根管冲洗是根管治疗的重要步骤.本实验通过观察五倍子水提取物与常用根管冲洗液处理前后牙本质显微硬度的变化,研究各冲洗液对根管壁硬度的影响.结果表明:各组溶液处理后牙本质显微硬度均有下降;五倍子水提取物处理后,牙本质显微硬度变化较小.     

桡骨显微骨硬度分布特征的实验研究

目的研究人体桡骨显微骨硬度分布特征,并探讨其与解剖结构、骨折流行病学等相关关系。 方法将3个新鲜桡骨标本分为桡骨头、桡骨颈、桡骨粗隆、桡骨干1~9、桡骨远端、桡骨茎突14个部位,并垂直其长轴切取骨组织切片。于骨组织切片的前、后、内、外4个区域各选取5个测量位点,通过显微维氏硬度仪测量每个部位的显微骨硬度。 结果桡骨硬度最硬部位位于桡骨干8,硬度值为（43.82±5.20）HV,硬度最小的部位位于桡骨头,硬度值为（33.30±3.60）HV。桡骨近端的硬度值为（34.15±6.48）HV,桡骨干的硬度为（42.54±5.59）HV,桡骨远端的硬度为（35.24±5.17）HV。 结论桡骨最硬处位于桡骨干下段,桡骨近、远端硬度相近,都低于桡骨干。桡骨干的硬度值高于桡骨近端及桡骨远端,差异有统计学意义,桡骨近端与桡骨远端硬度值差异无统计学意义。桡骨前、后、内、外侧差异无统计学意义。桡骨远端骨折高发除与解剖外形和损伤机制有关外,此处硬度骤降也应视为因素之一。     

Influence of curing modes on the degree of conversion and mechanical parameters of dual-cured luting agents

PurposeTo investigate the effects of different curing modes, including tack cure, on the degree of conversion (DC) and mechanical parameters of dual-cured luting agents for all-ceramic restorations.MethodsImmediate light curing, intermittent light curing (2-s tack cure and a 1-min interval before the main cure), delayed light cuing (2-min delay) and chemical or no light curing were used to cure two dual-cured luting agents, RelyX Unicem and PermaCem 2.0, through a 1.5-mm thick lithium disilicate ceramic slide. DC (n = 3), micro-hardness (n = 5), shrinkage strain (n = 4) and shrinkage stress (n = 3) were measured under the aforementioned curing modes. The data were analyzed using two-way ANOVA and post-hoc Tukey HSD test, with the level of significance set at α = 0.05.ResultsFor both luting agents, all the light-curing modes produced similar final DC, but using chemical cure only could significantly reduce the DC. The mechanical parameters followed a similar pattern. There were positive but nonlinear correlations between DC and the other mechanical parameters, with the increase in these parameters with DC being slower initially.ConclusionsProvided adequate light curing is applied to a dual-cured luting agent, delaying the light curing or using a tack cure first to facilitate seating of a restoration may not have a significant impact on the luting agent’s final degree of conversion. However, using chemical cure only may result in inadequate cure of the luting agent and is recommended only for highly opaque restorations.     

渗透树脂用于正畸后白垩斑治疗的研究进展

釉质脱矿在正畸固定矫治器的正畸期间发病率较高,形成白垩斑,影响牙齿美观。渗透树脂以其微创、无痛的特点使患者易于接受。它可阻断病变继续发展,并且可改善白垩斑外观。本文就渗透树脂颜色稳定性、显微硬度等特点进行阐述。     

Micro-hardness evaluation of a micro-hybrid composite resin light cured with halogen light, light-emitting diode and argon ion laser

This in vitro study aimed to determine whether the micro-hardness of a composite resin is modified by the light units or by the thickness of the increment. Composite resin disks were divided into 15 groups (n = 5), according to the factors under study: composite resin thickness (0 mm, 1 mm, 2 mm , 3 mm and 4 mm) and light units. The light activation was performed with halogen light (HL) (40 s, 500 mW/cm²), argon ion laser (AL) (30 s, 600 mW/cm²) or light-emitting diode (LED) (30 s, 400 mW/cm²). Vickers micro-hardness tests were performed after 1 week and were carried out on the top surface (0 mm—control) and at different depths of the samples. Analysis of variance (ANOVA) and Tukey tests (P ≤ 0.05) revealed no statistically significant difference among the light units for the groups of 0 mm and 1 mm thickness. At 2 mm depth, the AL was not statistically different from the HL, but the latter showed higher micro-hardness values than the LED. In groups with 3 mm and 4 mm thickness, the HL also showed higher micro-hardness values than the groups activated by the AL and the LED. Only the HL presented satisfactory polymerization with 3 mm of thickness. With a 4 mm increment no light unit was able to promote satisfactory polymerization.     

Effect of different manipulations on the physical,chemical and microstructural characteristics of Biodentine

ObjectiveThe water to powder ratio and method of mixing is important for the properties of hydraulic cements. For this purpose a number of clinicians prefer premixed materials. Dental manufacturing companies provide predosed materials, however the manufacturer instructions are not always adhered to. The aim of this research is to investigate physical and chemical alterations of the tricalcium silicate‐based cement Biodentine when manipulated according to the manufacturer’s instructions (control) or changing the doses and mixing of the material components.Methods6 groups were constituted according to different mixing and dosing of powder and liquid. The hydrated cements were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Calcium ion concentration of the leachate was also investigated. Assessment of the physical characteristics included setting time and microhardness.ResultsMicrostructural differences were visible only in the Biodentine mixed manually with water, in which early hydration rate was also affected, with lower calcium ion release. Increase of Biodentine liquid increased the calcium ion release, but also increased the setting time. Manual manipulation required more liquid (both water and Biodentine liquid) added to the mixture to guarantee a similar consistency to the control. A decrease in setting time was also noted. All groups showed higher values of microhardness at 24 h compared to the freshly set materials. In the freshly set materials, there was an overall decrease in microhardness in all groups when compared to group control, particularly significant when increasing the dosage of Biodentine liquid.SignificanceWhen mixing Biodentine, altering the mixing procedure in terms of type and amount of liquid added to the powder and mixing device chosen has an effect on the physical, chemical and mechanical characteristics and surface topography of the material, when compared to Biodentine mixed according to the manufacturer’s recommendations. Hence, the manufacturer’s instructions should be strictly followed.     

The impact of different low-pressure plasma types on the physical,chemical and biological surface properties of PEEK

ObjectivePlasma treatment can be used as surface treatment of PEEK (poly-ether-ether-ketone) to increase the bonding strength between veneering composite and dental prosthetic frameworks of PEEK or enhance biocompatibility of PEEK implants. These improvements are probably based on chemical changes of the PEEK surface. However, the aim of the study was to evaluate the impact of different low-pressure plasma treatments on surface properties of PEEK, such as roughness, hydrophilicity, micro-hardness, crystallinity and biological activity of PEEK.MethodsDue to different plasma treatments, 143 disc-shaped specimens of pure implantable PEEK were divided into 4 groups: PEEK (no plasma treatment, n = 29), H-PEEK (hydrogen plasma treatment, n = 38), O-PEEK (oxygen plasma treatment, n = 38), H/O-PEEK (hydrogen/oxygen plasma treatment with a gas mix ratio of 2:1, n = 38). Subsequently, surface roughness, surface contact angle, surface crystallinity, surface micro-hardness and human osteoblast cell coverage area of each group were examined.ResultsThe hydrophilicity, crystallinity and micro-hardness of the plasma-treated groups increased significantly compared to the untreated group, whereas significant differences in the results of the micro-hardness tests could be shown between all groups up to a test force of 0.02N. Cell density was significantly higher on treated vs. untreated PEEK surfaces. Oxygen and H/O plasma treatments revealed to be most effective, whereas H/O plasma worked ten times faster to achieve the same effects.SignificanceThe hydrogen-oxygen, 2/1-mixed plasma treatment combines the effect of hydrogen and oxygen plasma which strongly improve the surface properties of PEEK implant material, such as hydrophilicity, crystallinity, surface micro-hardness and HOB cell adhesion.     

Micro-hardness and mineral loss of enamel lesions after infiltration with various resins: Influence of infiltrant composition and application frequency in vitro

Objectives

The aim of this in vitro study was to evaluate the influence of infiltrant composition and application frequency on micro-hardness and lesion progression after resin infiltration of artificial enamel lesions.

Methods

In each of 100 bovine enamel samples, three artificial caries lesions were created (pH = 4.95, 50 days). After etching two of the lesions (37% phosphoric acid) specimens were randomly allocated to five infiltrants (four experimental infiltrants with different monomer and solvent compositions and penetration coefficients, and one commercial infiltrant [Icon, DMG]). Lesions were then infiltrated and light-cured, and infiltration repeated afterwards for one of the lesions. Infiltrated samples were cut into halves, with one half being demineralised for further 50 days. Micro-hardness (VHN) and integrated mineral loss (ΔZ) were evaluated at baseline and after second demineralisation. Repeated measures ANOVA and paired t-tests were used to analyse influence of material composition and application frequency on micro-hardness and lesion progression (integrated mineral loss difference ΔΔZ).

Results

Resin infiltration significantly increased micro-hardness and reduced lesion progression compared to untreated artificial lesions (p < 0.05, t-test). Neither micro-hardness nor lesion progression were significantly influenced by material composition (p > 0.05, ANOVA). In contrast, twice application resulted in significantly increased micro-hardness and demineralisation resistance of infiltrated lesions (p < 0.05, ANOVA).

Conclusion

Resin infiltration significantly improves micro-hardness and demineralisation resistance of enamel lesions; these effects are significantly enhanced if resins are applied twice. Experimental resins did not outperform the commercial infiltrant.

Clinical significance

This in vitro study demonstrated that resin infiltration significantly increases both micro-hardness and demineralisation resistance of enamel caries lesions. Twice application of the infiltrant seems to increase these effects. In contrast, the composition of the infiltrant had no significant influence on investigated parameters.