Improvement of erosion resistance of a silicate cement by infrared radiation

Abstract – Silicate cement specimens have been exposed to infrared radiation for the purpose of improving the erosion resistance. Exposure for periods of 3–10 min, corresponding to a surface temperature of about 60–70°C, resulted in a reduced phosphate release of about 3–5 times that of a non-exposed group. the temperature distributions on the surface, as well as in a position 5mm beneath the surface, were measured with thermocouples during irradiation. A difference in temprature of about 20°C was registered between the surface and interior positions. the technique may be clinically exploited by exposing the restoration after insertion to a small infrared radiation source, available on the commercial market.     

Inhibition of bacterial growth by tetracycline-impregnated enamel and dentin

Tetracyclines can react with enamel and dentin to form relatively insoluble fluorescent compounds. The purpose of this study was to evaluate the possible antimicrobial effect of these reaction products on various microorganisms associated with human dental plaque and periodontal disease. Slabs of native dentin and enamel as well as demineralized dentin were immersed in aqueous solutions of tetracycline HC1, oxytetracycline HC1 and doxycycline HC1 for periods of 1 h or 24 h. Unimpregnated enamel and dentin slabs sterilized by gamma irradiation and specimens impregnated with phenoxymethylpenicillin calcium were used as controls. Test and control specimens were placed on agar plates seeded with B. cereus, C. ochraceus, S. sanguis, F. nucleatum, B. melaninogenicus or A. viscosus and were subsequently incubated aerobically or anaerobically at 37°C. With the exception of enamel impregnated for 1 h in a 0.01 mg/ml tetracycline solution, all test specimens caused growth inhibition zones, varying in size according to concentration of the drug, immersion period and bacterial species. The results indicate that tetracyclines react with enamel and dentin to form slightly soluble compounds with a pronounced antibacterial effect. In comparison, the antimicrobial effect of dentin treated with penicillin was small.     

酸蚀处理对新型自粘结树脂水门汀粘结强度的影响

目的:评价酸蚀处理对新型自粘结树脂水门汀Unicem与牙本质和牙釉质之间粘结强度的影响。方法:选取新鲜拔除的无龋坏人第三磨牙36个,制备颊侧牙本质粘结面和近、远中牙釉质粘结面,随机分为3组,每组12个牙,分别选用Unicem、磷酸酸蚀配合Unicem和Panavia F(对照组)进行粘结处理,分别测试牙本质、牙釉质粘结强度,并通过扫描电镜观察粘结界面。结果:在牙本质粘结强度上,Unicem组(12.84±2.29 MPa)与Panavia F组(14.93±3.73 MPa)之间无显著性差异(P>0.05),但均显著高于磷酸酸蚀配合Unicem组(9.12±1.54 MPa)(P<0.05);牙釉质粘结强度上,磷酸酸蚀配合Unicem组(17.24±7.62 MPa)和Panavia F组(17.99±3.66 MPa)无显著性差异(P>0.05),但均显著高于Unicem组(6.47±1.54MPa)(P<0.05)。结论:酸蚀处理可以显著提高自粘结树脂水门汀Unicem牙釉质粘结强度,却降低了牙本质粘结效果。     

Thermogravimetric studies on sound and carious human enamel and dentin as well as hydroxyapatite

The present study was conducted to investigate the thermal behavior of human sound and carious enamel and dentin. The results were compared to those obtained for pure hydroxyapatite. The volatile decomposition products were identified by mass spectrometry. Solid decomposition products were analyzed by infrared (IR) spectrometry. For both normal and carious enamel, the differential thermogravimetry (DTG) curves revealed three peaks at about 90–100, 330, and 900°C. Both normal and carious dentin revealed two common peaks in their DTG curves, at about 90–100 C and 330°C. An additional peak at 500–600°C was observed in the DTG curve of carious dentin in air atmosphere. This peak completely disappeared in nitrogen (N₂) atmosphere. About 11–12% of sound and carious enamel was volatilized in air. The values for sound dentin were 34% and for carious dentin 54% per weight, respectively. Enamel and dentin (apatite protein complex) decomposed at higher temperatures than pure hydroxyapatite in air. In N₂ atmosphere, both enamel and dentin are more resistant to thermal decomposition than in air, because organic materials decompose easier in an oxidizing atmosphere than in an inert atmosphere.     

酸蚀处理对新型自粘接树脂水门汀Clearfil SA Luting粘接性能影响的研究

目的：评价酸蚀处理对自粘结树脂水门汀Clearfil SA Luting与牙釉质和牙本质粘结强度的影响。方法：选取新鲜拔除的无龋坏人第三磨牙36个,制备近、远中牙釉质粘结面和颊侧牙本质粘结面,随机分为3组（n=12）,分别选用Clearfil SA Luting（SAC）、磷酸酸蚀配合Clearfil SA Luting进行粘结,测试两种处理方式对SAC与牙釉质、牙本质粘结强度的影响,同时与对照组Panavia F（PF）的粘接结果进行对照,并通过扫描电镜观察粘结界面。结果：牙釉质粘结强度测试结果显示,磷酸酸蚀配合SAC组（39.64±6.24）MPa显著高于未酸蚀组SAC（27.25±7.03）MPa组与对照组PF（22.92±7.13）MPa（P〈0.05）,但SAC未酸蚀组（27.25±7.03）MPa与对照组PF（22.92±7.13）MPa间无统计学差异（P〉0.05）。牙本质粘结强度测试结果显示,SAC未酸蚀组（10.09±3.26）MPa与PF对照组（14.23±6.39）MPa之间无显著性差异（P〉0.05）,但均显著高于SAC配合磷酸酸蚀组（1.13±1.12）MPa（P〈0.05）。结论：酸蚀处理可以显著提高自粘结树脂水门汀SAC与牙釉质粘结强度,但却降低了其与牙本质粘结效果。     

Experimental tricalcium silicate cement induces reparative dentinogenesis

Objectives

To overcome shortcomings of hydraulic calcium-silicate cements (hCSCs), an experimental tricalcium silicate (TCS) cement, named ‘TCS 50’, was developed. In vitro research showed that TCS 50 played no negative effect on the viability and proliferation of human dental pulp cells, and it induced cell odontogenic differentiation. The objective was to evaluate the pulpal repair potential of TCS 50 applied onto exposed minipig pulps.

Effect of long-term administration of fluoride on plasma fluoride and calcium in relation to forming enamel and dentin in rats

Abstract— Three groups of 1-month-old rats were kept on water containing 0.2, 56.5 and 113 parts/10 6 F-, respectively, for a period of 2 months. These groups were set up in order to study the relationship between long-term administration of high doses of waterborne fluoride, plasma values of fluoride and calcium and changes in forming dentin and enamel of the rat incisor. The microradiographic study revealed that increased levels of fluoride caused a delay in mineralization of the enamel. In the 113 parts/10 6 group the radiolucent areas in the enamel exhibited a distinct periodicity along the tooth, a phenomenon which cannot at present be explained. In the dentin the fluoride interfered with the process of mineralization giving rise to radiolucent and radiopaque banding in the experimental groups. With increasing levels of fluoride in the water supply a significant increase in plasma fluoride was recorded. In contrast the serum calcium values in both experimental groups were reduced to the same extent, which differed significantly from that of the control group. It is concluded that the fluoride doses which are needed to create fluorotic changes in rats may interfere with calcium metabolism and basic mineralization processes.     

MTAD根管冲洗液对牙本质、牙釉质微硬度影响的研究

目的:评价MTAD根管冲洗液对牙本质、牙釉质微硬度的影响。方法:收集新鲜完整的前磨牙48个,截取牙冠并沿牙体长轴剖开,分别用30mL/L过氧化氢液、50g/L次氯酸钠液、MTAD液、13g/L次氯酸钠液处理牙本质、牙釉质5、15min,采用微硬度测定仪测定处理前、后两个时间点上牙本质、牙釉质的微硬度。结果:与30mL/L过氧化氢液和50g/L次氯酸钠液相比,使用MTAD液和13g/L次氯酸钠液处理后的牙本质、牙釉质微硬度的降低幅度不明显。结论:通过与30mL/L过氧化氢液、50g/L次氯酸钠液的对比研究发现,MTAD冲洗液对牙本质、牙釉质微硬度的影响明显小于前两者, 13g/L次氯酸钠冲洗液的影响与MTAD的相似,MTAD液联合13g/L次氯酸钠液的根管冲洗方法值得推荐。     

Fluoride release from and tensile bond strength of Ketac-fil and ketac-silver to enamel and dentin

Silver-reinforced glass ionomer cements have recently become commercially available. The purpose of this study was to determine the fluoride (F) release from, and the tensile bond strength (TBS) of Ketac-Fil, a conventional, and Ketac-Silver, a silver-reinforced glass ionomer cement, to enamel and dentin, respectively. To determine F release, 6 discs, 20 mm in diameter and 1.5 mm thick, were prepared from each material, and suspended in 50 ml glass distilled water for 24 h. The discs were washed with 50 ml TISAB and the fluoride concentrations determined electrometrically. These procedures were repeated for 14 consecutive days. The TBS of Ketac-Fil to enamel (A) and dentin (B) and of Ketac-Silver to enamel (C) and dentin (D), respectively, were determined. Fifteen test specimens were prepared with each procedure. The test specimens were stored in water at 37°C for 24 h. The test specimens were then mounted in an Instron machine and subjected to a tensile load at a cross-head speed of 0.02 inch. min⁻¹. The bond strengths were calculated and expressed in MN.m⁻². The data were analyzed by ANOVA and Duncan's multiple range test at the 5% level of significance. Ketac-Fil only released significantly more F (μg F. mm−2 during the first 7 days than Ketac-Silver. The following tensile bond strengths (MN.m⁻²) were obtained: A: 2.3±1.6; B: 2.0 ±2.3; C: 1.2±1.7; D: 0.5±1.3. The bond strengths of D were significantly lower than those of A and B but not significantly different from C. The addition of silver to a glass ionomer cement reduced the fluoride release and the bond strength to dentin.     

Mineral composition of enamel and dentin of primary and permanent teeth in Finland

abstract – The concentrations of 12 different elements were measured in dentin and enamel of primary and permanent teeth collected in six different localities in Finland. Na, Cl, Al, Mn, Ca, and P were determined by neutron activation analysis, K, Mg, Zn, Cu, and Fe by the atomic absorption method, and F with the fluoride-specific electrode. Most elements were present in higher concentrations in the enamel than in the dentin: Mg, however, was higher in the dentin. Compared with the permanent teeth, the primary teeth contained more K and Mn in enamel and K and Mg in dentin, but less Na and Zn in enamel. Differences between the six localities were significant for F, Cl, K, Zn, Na, and Mn. Fe, Cu, and Mn contents of teeth were much lower in Finland than elsewhere; in the typical Finnish diet the contents of Fe and Cu are relatively low and iron deficiency anemia is unusually common in Finland.     

Measurement of translucency of tooth enamel and dentin

Objective. To determine the translucency of human and bovine enamel and dentin using reflection spectrophotometers. Material and Methods. The color of intact human and bovine enamel and dentin specimens was measured over a white and a black plasticine backing using two spectrophotometers with different aperture sizes; translucency parameter (TP) and contrast ratio (CR) were calculated. Plasticine was used as backing because the specimens were not uniform. The TP values of five composite resins measured over the backings of plasticine and reflectance standards were also determined. Results. There were no significant differences between the TP values of the composite resins measured over the backings of plasticine and reflectance standards (p>0.05). Mean TP values of 1 mm thick bovine enamel, bovine dentin, human enamel and human dentin were 14.7, 15.2, 18.7, and 16.4, respectively, based on the 3 mm round aperture. There were significant correlations between the TP values measured by the two apertures; the bigger the aperture size, the higher the TP value (r=0.87–0.91, p<0.01). The translucency of enamel and dentin increased in direct proportion to wavelength and in inverse proportion to thickness (r=0.87–0.91). Mean CR values were negatively correlated with the TP values (r = ?0.93 to ?0.78). Conclusions. These data could be used as references in the development of esthetic restorative materials and clinical shade-matching.     

不同表面预处理对自黏结树脂水门汀釉质黏结性能影响的研究

目的:研究、测评不同表面预处理对自黏结树脂水门汀ClearfilTM SA Cement釉质黏结强度以及黏结界面微观形态的影响。方法:选取新鲜拔除的无龋损人磨牙24个,每个牙齿切取近中、远中釉质试件各1片,共获得48个釉质试件,分别用自凝树脂包埋并经水砂纸打磨后随机分为3个表面预处理组和1个对照组(自黏结组),分别进行不同表面预处理后制作自黏结树脂水门汀黏结试件,用万能材料试验机测试各组试件的剪切强度,并在SEM下观察其黏结界面。结果:磷酸预处理组黏结强度最高(39.64±6.24)MPa,与其他各组相比,差异均有统计学意义(P<0.05),随后依次为自酸蚀黏结剂预处理组(33.36±5.86)MPa、全酸蚀黏结剂预处理组(31.42±4.82)MPa和不作表面预处理的自黏结组(27.25±7.03)MPa。SEM观察各组黏结界面均结合紧密,磷酸和全酸蚀黏结剂预处理组可见树脂突形成。结论:不同表面预处理对自黏结树脂水门汀ClearfilTM SA Cement釉质黏结强度提高程度不同,本实验条件下以磷酸预处理最好。     

Resin bonding to enamel and dentin with one–component UDMA/HEMA adhesives

The aim of this study was to investigate the potential of UDMA/HEMA mixtures as priming and sealing components of dental adhesives. The monomers were mixed in weight ratios 100/0, 80/20, 60740, 50/50, 40/60, 20/80, 10/90, and 0/100, light activated, and dissolved in acetone at equal parts. The 60/40 UDMA/HEMA mixture served as a reference which was modified with 5, 10, 20, and 30 parts 4-MET relative to the mass of the basic monomer mixture. Shear bond strengths (24 h) of resin composite cylinders, bonded with the adhesive monomers on human enamel and dentin, were determined following a total etch technique with phosphoric acid and application of the adhesives in 2 coats on moist tooth surfaces. Average bond strength to enamel was 32 MPa with no difference between the adhesives. On dentin, significantly different bond strengths were found between UDMA (12.9 MPA) and HEMA (19.4 MPa), whereas all binary mixtures bond strengths were not significantly different (mean 16.2 MPa). Addition of 5 to 20 wt% 4-MET resulted in a significantly increased mean shear bond strength of 22.3 MPa on dentin. At 10%, a maximum mean strength of 25.4 MPa was recorded. It is concluded that mixtures of commonly used polymerizable monomers, characterized by hydrophilic moieties and dissolved in acetone, are promising candidates for effective resin bonding to enamel and dentin, provided application by the moist bonding technique.     

Tetracycline-impregnated enamel and dentin: duration of antimicrobial capacity

Abstract – The present study was done in order to examine the durability of the tetracycline-induced antimicrobial capacity, and also to assess the reproducibility of the bacterial growth-inhibitory assay used. Standardized enamel and dentin specimens were impregnated in aqueous solutions of tetracycline HCl, oxytetracycline HCl or doxycyclinc HCl, rinsed in water, and stored dry for 200 days. Another series of specimens was impregnated in solutions of doxycychne HCl and then rinsed in tap water for varying periods up to 35 days. In addition, drug-impregnated specimens were used for reproducibility tests without storage or prolonged rinsing. Impregnated specimens were tested for antimicrobial capacity on agar plates seeded with S. sanguis. After 24 h aerobic incubation in 10% CO₂ atmosphere, the plates were inspected and the diameter of the bacterial growth inhibition zones measured. The drug-impregnated enamel and dentin specimens consistently demonstrated growth-inhibitory capacity. The results of the reproducibility tests showed moderate intrasample and day-to-day variation. Two hundred days of dry storage or 35 days soaking in water reduced, but did not eliminate, the bacterial growth-inhibitory capacity of the impregnated dental specimens. The results show that a short-term exposure of dental hard tissues to tetracyclines may result in a long-lasting antibacterial capacity.     

根管冲洗液对牙本质、牙釉质微硬度的影响

目的 评价根管冲洗液对牙本质、牙釉质微硬度的影响。方法 收集团正畸拨除的新鲜前磨牙44颗,将牙冠沿牙长轴剖开,用3％双氧水,5％次氯酸钠,17％EDTA及氯仿分别处理5、15min,采用微硬度测定仪测定不同处理时间前后的牙本质、牙翻质微硬度。结果 处理后的牙本质、牙翻质微硬度均显著降低,且与处理时间相关。结论 不同化学冲洗液对牙本质、牙釉质微硬度均产生一定的影响。     

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目的    探讨应用黏结型玻璃离子黏结正畸托槽以降低牙釉质脱矿。方法    选择2007年2月至2009年10月怀化市第一人民医院口腔科就诊的黏结标准方丝弓矫正器患者197例（共有3266颗牙黏结托槽）,将患者上、下颌黏结托槽的左、右牙齿随机分为试验组和对照组,各1633颗牙。试验组：上下颌一侧中切牙至同侧第二前磨牙应用黏结型玻璃离子黏结托槽;对照组：上、下颌另一侧中切牙至同侧第二前磨牙应用牙釉质黏结树脂黏结托槽。矫治结束后,对全口黏结托槽的牙唇（颊）面进行检查,评价脱矿程度。结果    试验组黏结托槽的牙唇（颊）面发生牙釉质脱矿的总牙数为75颗,并且程度较轻,均为1度,脱矿率4.59%,明显低于对照组（12.06%）,且差异有统计学意义（P < 0.01）。结论    应用黏结型玻璃离子黏结托槽可降低釉质脱矿率。     

Nd：YAG激光照射釉质,牙本质和牙骨质的形态变化

应用不同能量的脉冲Ｎｄ：ＹＡＧ激光照射釉质、牙本质和牙骨质表面，用ＳＥＭ观察其形态变化。结果表明：这些组织的表面产生许多密集、形态和边缘不规则的凹窝结构，深度１５～４０μｍ不等，但３种组织表面形态的改变和程度各不相同。分析讨论了粗糙的表面对复合树脂粘结的潜在意义，并提出合适的激光能量参数     

A structural analysis of approximal enamel caries lesions and subjacent dentin reactions

The present study examines the correlation between caries lesions in enamel and the corresponding dentin reactions in proximal tooth surfaces with lesions ranging from enamel lesions to cavitations without dentin exposure. Using quantitative imbibition technique, the highest degree of tissue porosity, irrespective of lesion activity, was always noted along a Central-Traverse (CT), which followed the direction of the rods from the deepest point of penetration to the surface. The conical shape of approximal enamel lesions can thus be seen as the result of systematic variations in porosity along the rods determined by the specific interproximal environment. The initial dentin reaction, related to the enamel lesion approaching the enamel–dentin junction (EDJ), was seen as a local dentin translucency where the CT crossed the EDJ. Results from histomorpho-metric analyses revealed that, when the enamel lesions reached the EDJ, brownish discoloration in the dentin never exceeded the histologic contact area between the enamel lesion and the EDJ. In relation to the less advanced parts of the individual enamel lesion, the dentin responded with formation of translucent dentin. These reactions did not occur beyond an area determined by lines in the direction of the rods from the peripheral part of the enamel lesion towards the EDJ. The results did not support the view that dentin caries spreads along the enamel-dentin junction. The peripheral dentin translucency is therefore generated by stimuli transmitted along the rods of the less advanced parts of the enamel lesions.     

pH-cycling of enamel and dentin lesions in the presence of low concentrations of fluoride

F-dentifrice usage causes slightly elevated fluoride levels in saliva. Therefore, the effects of permanent low fluoride concentrations versus daily dentifrice treatments were studied on enamel and dentin lesions in a pH-cycling model of alternating demineralization and remineralization. Groups received 1) no fluoride treatment. 2) 3 μM (0.06 ppm) F continuously present during re- and demineralization or 3) daily 5–min F-dentifrice treatments. Solutions were analyzed for changes in calcium and fluoride. Cumulative results (10 d) showed that for the non-fluoride group the dentin lesions increased, while for enamel lesions mineral uptake and loss were balanced. Addition of 3 μM F caused small, non-significant, enhancement of remineralization (1–7%). while demineralization was significantly inhibited for both tissues (9–23%). The daily dentifrice treatments resulted in a balance between mineral uptake and loss of dentin, due to inhibited demineralization (-33%) and enhanced remineralization (+ 79%). For enamel, the F-dentifrice treatments resulted in 43% reduction of demineralization, with no significant effect on remineralization. Fluoride loss from the 3 μM F cycling solutions was significant (up to 50%) and constant during the experimental period. Microradiographic analysis showed remineralization at the lesion front in enamel. In dentin, the lesion depth was increased in all groups, with concomitant mineral deposition in the surface region of the dentifrice group. Results indicate that slightly elevated fluoride levels may be considerably less effective in inhibiting lesion progression in dentin than in enamel, and suggest mineral uptake and loss to occur at similar depths for enamel lesions, while demineralization and remineralization occur at different depths in dentin.