Post-cure depth of cure of bulk fill dental resin-composites

Objectives

To determine the post-cure depth of cure of bulk fill resin composites through using Vickers hardness profiles (VHN).

Methods

Five bulk fill composite materials were examined: Tetric EvoCeram^® Bulk Fill, X-tra base, Venus^® Bulk Fill, Filtek™ Bulk Fill, SonicFill™. Three specimens of each material type were prepared in stainless steel molds which contained a slot of dimensions (15 mm × 4 mm × 2 mm), and a top plate. The molds were irradiated from one end. All specimens were stored at 37 °C for 24 h, before measurement. The Vickers hardness was measured as a function of depth of material, at 0.3 mm intervals. Data were analysed by one-way ANOVA using Tukey post hoc tests (α = 0.05).

Results

The maximum VHN ranged from 37.8 to 77.4, whilst the VHN at 80% of max.VHN ranged from 30.4 to 61.9. The depth corresponding to 80% of max.VHN, ranged from 4.14 to 5.03 mm. One-way ANOVA showed statistically significant differences between materials for all parameters tested. SonicFill exhibited the highest VHN (p < 0.001) while Venus Bulk Fill the lowest (p ≤ 0.001). SonicFill and Tetric EvoCeram Bulk Fill had the greatest depth of cure (5.03 and 4.47 mm, respectively) and was significant's different from X-tra base, Venus Bulk Fill and Filtek Bulk Fill (p ≤ 0.016). Linear regression confirmed a positive regression between max.VHN and filler loading (r² = 0.94).

Significance

Bulk fill resin composites can be cured to an acceptable post-cure depth, according to the manufacturers’ claims. SonicFill and Tetric EvoCeram Bulk Fill had the greatest depth of cure among the composites examined.     

Enamel white spot lesions can remineralise using bio-active glass and polyacrylic acid-modified bio-active glass powders

Objective

To evaluate the potential of bio-active glass (BAG) powder and BAG containing polyacrylic acid (PAA-BAG) to remineralise enamel white spot lesions (WSL).

Methods

32 human enamel samples with artificial WSLs were assigned to 4 experimental groups (n = 8); (a) BAG slurry, (b) PAA-BAG slurry, (c) “standardised” remineralisation solution (positive control) and (d) de-ionised water (negative control). Mechanical properties of enamel were assessed using surface and cross-section Knoop microhardness. Micro-Raman spectroscopy in StreamLine™ scan mode was used to scan lesion cross-sections. The intensity of the Raman phosphate peak at 959 cm⁻¹ was fitted and measured producing depth profiles analysed using a double-step fitting function. A further 20 samples (n = 5) were used to obtain 3D images of surfaces using non-contact white light profilometry permitting measurement of lesion step height in relation to the sound enamel reference level, and to scan the lesion surface using scanning electron microscopy (SEM). Data were analysed statistically using one-way ANOVA with Tukey's HSD post-hoc tests.

Results

BAG, PAA-BAG and the remineralisation solution exhibited statistically significantly higher surface and cross-section Knoop microhardness compared to the negative control. Micro-Raman spectroscopy detected significantly higher phosphate content within the treated groups compared to the negative control group. Lesions’ depth was not significantly reduced. SEM images revealed mineral depositions, with different sizes and shapes, within BAG, PAA-BAG and the positive control groups.

Conclusion

BAG and PAA-BAG surface treatments enhance enamel WSL remineralisation, assessed by the resultant improved mechanical properties, higher phosphate content and morphological changes within the artificial lesions.     

护牙素与多乐氟对放射线照射后牙骨质显微硬度的影响

目的 探讨护牙素与多乐氟对放射线照射后牙骨质显微硬度值的影响.方法 收集因正畸减数拔除的前磨牙40颗,随机分为4组,其中3组在20℃下对牙根表面开窗区进行放射线照射：直接照射组直接采用放射线照射开窗区;护牙素组每次照射前先在开窗区涂上护牙素,再进行放射线照射,照射结束后去离子水冲洗表面;多乐氟组首次照射前在开窗区按照操作步骤涂多乐氟,再次照射前无需再涂;另设空白对照组,只在相同环境中保存,开窗区表面不做任何处理.照射前后分别测量各组的牙骨质表面显微硬度值.结果 照射前直接照射组、护牙素组、多乐氟组、空白对照组的显微硬度值分别为86.8±6.88、90.9±9.34、84.5±7.87、91.2±9.81,各组牙骨质表面显微硬度值差异无统计学意义（P＞0.05）.照射后,直接照射组显微硬度值（30.7±5.62）明显低于护牙素组（113.4±10.15）、多乐氟组（135.9±8.52）、空白对照组（91.2±9.81） （P ＜0.05）,护牙素组显微硬度值明显高于空白对照组（P＜0.05）,而多乐氟组显微硬度值明显高于空白对照组与护牙素组（P＜0.05）.结论 应用护牙素或多乐氟能够有效预防放射线所致的牙骨质脱矿,并能促进其再矿化,但多乐氟的防龋效果优于护牙素.     

Measurement of hydroxyapatite density and Knoop hardness in sound human enamel and a correlational analysis between them

Objective

The aim of this study was to measure the hydroxyapatite (HAP) density and Knoop hardness (KHN) of enamel slabs and to analyse the relationship between them.

Design

Twenty enamel slabs (10 lingual sides and 10 buccal sides) were prepared and scanned with micro-CT. Tomographic images of each slab from dental cusp to dentinoenamel junction (DEJ) were reconstructed. On these three-dimensional (3D) images, regions of interest (ROIs) were defined at an interval of 50 μm, and the HAP density for each ROI was calculated. Then the polished surfaces were indented from cusp to DEJ at intervals of 50 μm with a Knoop indenter. Finally, the data were analysed with one-way ANOVA, Student's t-test, and linear regression analysis.

Results

The HAP density and KHN decreased from the dental cusp to DEJ. Both HAP density and KHN in the outer-layer enamel were significantly higher than those in the middle- or inner-layer enamel (P < 0.05). The HAP density showed no significant difference between the buccal and lingual sides for enamel in the outer, middle and inner layers, respectively (P > 0.05). The KHN in the outer-layer enamel of the lingual sides was significantly lower than that of the buccal sides (P < 0.05); there was no significant difference between the lingual and buccal sides in the middle or inner layer. Linear regression analysis revealed a linear relationship between the mean KHN and the mean HAP density (r = 0.87).

Conclusion

Both HAP density and KHN decrease simultaneously from dental cusp to DEJ, and the two properties are highly correlated.     

不同温度及不同光固化灯对光固化复合树脂硬度的影响

目的:探讨不同温度处理后的光固化复合树脂用卤素光固化灯和第2代LED光固化灯照射后复合树脂硬度的差别.方法:设5℃(冷藏)、23℃(常温)、40℃(加热)3种不同温度处理光固化复合树脂Clearfil AP-X.再分别用卤素光固化灯Translux CL和LED灯Elipar FreeLight2照射,采用显微维氏硬度计测量树脂试件表面和底部的硬度.结果采用SPSS 17.0软件包进行方差分析.结果:40℃加热处理后的树脂试件表面和底部的硬度值均较其他2种温度处理后的树脂硬度值增高(P＜0.01).3种温度处理后.LED灯照射树脂试件表面和底部硬度值比卤素灯照射后的硬度值高(P＜0.01).结论:树脂试件使用前预加热处理,可以增强树脂的硬度;第2代LED灯的固化效率优于卤素灯.     

液体抛光剂和护牙素预防托槽周围釉质脱矿效果的体外研究

目的 对比研究BISCOVER LV液体抛光剂和Tooth Mousse护牙素对托槽周围牙釉质脱矿后促进其再矿化的效果.方法 将60颗离体牙粘接托槽后随机分为3组,分别涂上液体抛光剂、护牙素以及蒸馏水,将离体牙轮流放置于人工唾液和人工致龋液中浸泡,模拟患者进食的状态,90 d后使用显微硬度仪以及扫描电镜检测托槽周围牙釉质表面硬度以及形态的变化.结果 3组牙釉质脱矿后的显微硬度值差异具有统计学意义(F=507.50,P<0.05),两两比较结果显示:实验组和阳性对照组牙釉质显微硬度值之间差异无统计学意义(P>0.05);而实验组牙釉质显微硬度值高于阴性对照组,以及阳性对照组牙釉质显微硬度值高于阴性对照组,且差异均有统计学意义(P<0.05).扫描电镜显示实验组牙釉质超微结构表面反应物沉积增多,空隙变小,牙釉质再矿化现象明显.结论 在正畸治疗中使用BISCOVER LV液体抛光剂和Tooth Mousse护牙素均可有效防止托槽周围牙釉质脱矿,两者在临床上的使用可视患者的配合程度而定.     

Post-curing in dental resin-based composites

Objective

To determine the post-curing in six commercial contemporary resin-based composites (RBCs) using axial shrinkage, the degree of conversion, and Vickers hardness.

Increased bone microhardness in fluoride treated rats

Microhardness was measured in sampling sites in the tibial diaphysis of control rats that received less than 1 ppm fluoride in the drinking water, and experimental rats that received 30, 90 and 120 ppm fluoride in the drinking water for 17 days. The latter dose was toxic, as evidenced by a decreased final body weight in this group. By means of tetracycline labelling, it was possible to measure bone hardness in four zones of increasing bone age: I) 3 days, II) 8 days, III) 13 days and IV) 22 days. Zones I through III represented bone formed during fluoride treatment, and Zone IV bone formed before fluoride treatment. In the control group, microhardness increased from Zone I to II, probably because mineral concentration was relatively low in Zone I, and remained constant thereafter. In the 90 and 120 ppm fluoride-treated groups, maximum microhardness was not achieved until Zone III. This delay was probably due to the fact that fluoride in large doses inhibits the rate of mineralization. In the 30 ppm fluoride-treated group, there was no delay in achievement of maximum microhardness; microhardness values in Zones I and III were greater than those in control animals, and microhardness in Zone III was higher than that in Zone IV. These results show that: 1) bone microhardness is increased in bone formed during fluoride treatment in rats given 30 ppm fluoride in the drinking water, 2) toxic doses of fluoride delay, but do not prevent achievement of normal maximum microhardness, and 3) changes in microhardness are seen only in bone formed during fluoride treatment.     

慢性牙周炎患者前磨牙牙骨质的显微硬度分析

目的分析牙齿在慢性牙周炎症过程中牙骨质的物理性状变化情况。方法收集重度慢性牙周炎患者的10颗前磨牙作为牙周炎组,非牙周炎患者拔除的10颗前磨牙作为对照组。应用显微硬度分析技术比较两组牙颊侧牙骨质表面根尖、根中和根颈1/3显微硬度。结果牙周炎组牙骨质根颈1/3区段、根中1/3区段和根尖1/3区段的表面平均显微硬度分别为（0.342±0.019）GPa（、0.322±0.013）GPa和（0.311±0.016）GPa,对照组对应区域的平均显微硬度分别为（0.393±0.014）GPa（、0.338±0.015）GPa和（0.327±0.011）GPa。牙周炎组对应区段的牙骨质表面平均显微硬度均低于对照组,差异均有统计学意义（P〈0.05）。两组由冠至根向牙骨质表面显微硬度均呈现下降趋势。结论慢性牙周炎症可能会影响受累牙齿牙骨质的表面硬度。     

四种化学预备液对根管壁显微硬度的影响

目的:评价乙二胺四乙酸盐(ethylenediamine tetraacetic acid,EDTA)、氯亚明(Chloramine)、丁克除(Des-occlusol)和酚克除(Resosolv)4种化学预备液根管内封药时对根管壁显微硬度的影响。方法:选择因正畸拔除的健康前磨牙65颗,实验组60颗和对照组5颗。实验组随机分为A、B、C、D 4组,每组15颗,各组又随机分为10 d组、20 d组和30 d组,每组5颗。常规开髓、拔髓、干燥根管后丙烯酸树脂封闭根尖孔。根管内封药,磷酸锌暂封,4℃储存,对照组不做任何处理,相同条件下储存。丙烯酸树脂包埋,硬组织切片机切片,显微硬度仪进行硬度测试,数据进行方差分析。结果:在本实验周期内,与正常对照组相比较,EDTA封药10 d和20 d组,根管壁的显微硬度下降无统计学意义;封药30 d组,根管壁的显微硬度下降有统计学意义(P<0.05)。氯亚明,丁克除和酚克除封药3个时间组,根管壁的显微硬度下降均无统计学意义。结论:在本实验周期内,EDTA封药10 d和20 d组,对根管壁的显微硬度无明显影响,而封药30 d组,对根管壁的显微硬度有显著影响。氯亚明、丁克除和酚克除3个封药时间组对根管壁的显微硬度均无明显影响。