氟化物涂膜对正畸固定矫治中牙釉质脱矿影响的SEM研究

目的：采用扫描电镜（SEM）观察氟化物涂膜对抑制离体牙牙釉质脱矿及促进再矿化的功效。方法：选择因正畸需要拔除的前磨牙15颗,经37％磷酸处理,制备人工釉质脱矿标本,并用氟化物涂膜进行表面处理。采用SEM对标本脱矿前（对照组）,脱矿后（脱矿组）以及氟化物涂膜治疗后（治疗组）的表面形貌进行观察分析。结果：对照组与脱矿组之间、脱矿组与治疗组之间形态学存在显著差异,而对照组与治疗组之间形态学差异相对较小。结论：氟化物涂膜可有效改善釉质脱矿后的牙齿脱矿形貌。     

牙釉质脱矿动力学研究

本实验用等组分方法研究牙釉质脱矿的动力学过程，重点比较了粉末釉质和完整釉质的脱矿属性。脱矿在乳酸或醋酸缓冲液中进行，溶液含磷酸钙盐但对磷灰石不饱和。通过添加预先配制的滴定液维持溶液成份恒定。根据所加滴定液体积与时间，实时描绘动力学曲线。对脱矿后的完整釉质组织进行了显微放射照相检查和硬度测定。结果表明，完整釉质的脱矿性质不同于粉末釉质，主要表现在前者除了溶解之外，还涉及不同矿物相的转变和再沉积。本研究有助于从晶体动力学方面理解牙釉质在龋齿脱矿过程中的理化本质，为以化学手段干扰脱矿过程提供理论基础。     

不同种类饮料对牙釉质脱矿作用的研究

目的 探讨饮料酸性程度与其引起牙釉质脱矿程度的关系,验证脱矿牙釉质在模拟唾液中自我矿化修复能力以及脱矿后马上刷牙对牙釉质影响.方法 ①在36.5℃条件下,将牛牙分别浸泡于可乐、橙汁和冰红茶中10 min、30 min和60 min,然后,置于模拟唾液中浸泡60 min;测量唾液浸泡前后的牙釉质表面硬度.另仅选可乐,在相同条件下进行人牙实验.②将牛牙置于可乐中浸泡60 min后即刻刷牙1 min、再置于模拟唾液中10 min和30 min后分别刷牙1 min,并另选人牙做验证实验,最后,对所有样本观察牙釉质表面形貌改变.结果 ①牛牙在饮料中浸泡不同时间后,硬度均有不同程度降低,其中可乐组牛牙硬度降低最显著.而在模拟唾液中浸泡60 min后,硬度值有一定程度的提高.②可乐浸泡的牙齿立即进行刷牙会在牙齿表面留下明显的排状划痕,如果再在模拟唾液中浸泡一定时间后刷牙,则未见留下划痕.人牙结果与牛牙类似.结论 酸性饮料会使牙釉质脱矿;模拟唾液可恢复已脱矿牙釉质的硬度,恢复程度与其脱矿程度以及在唾液中浸泡的时间相关;即刻刷牙会进一步损伤已被酸性饮料脱矿的牙釉质,而在模拟唾液中一段时间后使牙釉质硬度有所恢复.     

固定正畸治疗引起牙釉质脱矿的原因与防治

釉质脱矿是固定正畸治疗的常见并发症和主要风险因素.主要表现为托槽周围形成白垩斑和弹坑状缺损.本文就正畸治疗过程中釉质脱矿的影响因素及防治方法做一综述,以期为正畸所致釉质脱矿的深入研究提供参考.     

不同种类碳酸饮料导致牙釉质脱矿的比较研究

目的:比较几种碳酸类饮料对牙釉质的脱矿作用.方法:采用紫外-可见分光光度法检测5种碳酸类饮料中钙、磷含量,采用微量化学分析法检测5种碳酸类饮料处理牛牙釉质后饮料中钙、磷含量的变化.采用维氏显微硬度仪测定经饮料浸泡后牙釉质表面显微硬度的变化.结果:所选用的碳酸类饮料的钙浓度分别是雪碧为2.11 mmol/L,百事可乐为3.58 mmol/L,非常可乐为0.09 mmol/L,可口可乐为1.32 mmol/L,冰茶为0.05 mmol/L,饮料中磷的浓度分别是百事可乐为3.46 mmol/L,可口可乐为3.46 mmol/L,非常可乐为3.87 mmol/L,雪碧和冰茶中不含磷.5种饮料均能导致牙釉质钙磷溶出和表面显微硬度下降.不同种类碳酸饮料导致牙釉质钙磷溶出的量以及表面显微硬度下降的程度不同,差异具有显著性(P＜0.05).随时间延长,钙磷溶出减少,表面显微硬度降低的程度减弱.结论:碳酸类饮料都能导致牙釉质脱矿,所选饮料中,冰茶的脱矿作用最强.     

柠檬酸致牙釉质脱矿的研究

目的 观察10%柠檬酸酸蚀牙釉质不同时间的效果,以获得研究早期釉质龋的可靠体外实验模型,探索更高效的牙釉质脱矿实验方法.方法 选取离体人恒前磨牙切割制成牙釉质块,经10%柠檬酸及部分饱和酸缓冲脱矿系统脱矿,扫描电镜观察牙釉质表面经柠檬酸酸蚀不同时间(90 s、120 s、150 s)及部分饱和酸缓冲脱矿系统脱矿1周后的形态学特征,并用显微硬度计检测标本脱矿前后表面显微硬度.结果 牙釉质进行脱矿处理后,釉质表面呈现酸蚀状外观.酸蚀90 s时,仅见小部分釉柱晶格脱矿溶解,脱矿牙釉质的能力有限;酸蚀120 s时,与早期自然龋损近似,呈蜂窝状;酸蚀150 s时,牙釉质表面呈酸蚀样破坏形貌,属于过度酸蚀;而部分饱和酸缓冲脱矿系统脱矿效果相对较差.结论 柠檬酸具有较强的酸蚀作用,其脱矿牙釉质的能力随着时间的延长而增强,10%的柠檬酸酸蚀120 s可获得早期釉质龋模型.     

正畸治疗后牙釉质脱矿的临床观察

目的　了解采用固定矫正器治疗后 ,牙釉质脱矿的发生率及好发牙齿、好发部位。方法　对非治疗组 87个患者 2 0 72个牙齿及治疗组 1 0 0个患者 2 1 5 6个牙齿进行临床观察。结果　非治疗组脱矿发生率为 6 .1 7%、治疗组为 1 6 .2 3% (p <0 .0 1 ) ,好发牙齿是上前牙及下颌第一恒磨牙 ,好发部位是牙颈部及托槽周围。结论　固定矫正器引起的牙釉质脱矿是一个值得注意的问题 ,应采取必要的措施进行预防。     

饮料导致牙釉质脱矿作用的实验研究

目的:比较不同种类饮料对牙釉质的脱矿作用。方法:采用微量化学分析法测定饮料在处理牙釉质后1~7d 饮料中钙和磷浓度的变化。结果:实验饮料除矿泉水外对牙釉质都具有脱矿作用,导致牙釉质钙和磷的溶出。钙和磷的溶出因饮料的种类而异,差异具有显著性,P<01001。随时间的延长,钙和磷的溶出也具有显著性差异,P< 01001。钙和磷在7d内的总溶出量也因饮料的种类而异,差异具有显著性,P<01001。果汁类的钙和磷总溶出量最高,分别为11355Lmol/L?01250Lmol/L和11780Lmol/L?01270Lmol/L;钙奶最低,分别为01290Lmol/L?01092Lmol/L 和01239Lmol/L?01050Lmol/L。结论:饮料对牙釉质具有脱矿作用,脱矿作用的强弱与饮料的种类有关,果汁类最强,钙奶最弱。     

氟钼酸铵抑制牙釉质脱矿作用的研究

本研究观察了氟钼酸铵溶液对牙釉质抗酸溶解性及釉质结构的影响，探讨了氟钼酸铵溶液防龋、抑龋机理。     

不同碳酸饮料对青少年牙釉质脱矿作用的比较

目的:比较几种不同的碳酸饮料对青少年牙釉质的脱矿作用。方法:采用维氏显微硬度仪,测定经3种不同饮料(A组:雪碧;B组:芬达;C组:百事可乐),以蒸馏水为对照组(D组)浸泡的年轻恒牙牙釉质的表面显微硬度变化。扫描电镜(SEM),观察并比较经3种不同饮料浸泡的年轻恒牙牙釉质表面的形态变化。采用SPSS17.0软件对结果进行分析。结果:3种饮料均可导致年轻恒牙牙釉质表面显微硬度下降(P<0.05)。不同种类饮料对牙釉质的脱矿程度不同,A组与B组间硬度值P<0.05,有统计学意义;A组与C组间硬度值P<0.05,有统计学意义;B组与C组间硬度值P>0.05,无统计学意义。3种碳酸饮料浸泡一周后的牙齿,其釉质表面均有不同程度的脱矿现象,扫描电镜(SEM)可见牙釉质表面形态不规则,组织结构疏松,并可见松软悬浮物附着;釉柱不均匀断裂,形成无数微小间隙呈凹凸不平的粗糙面,局部可呈现深坑样外观。结论:碳酸饮料都能导致青少年牙釉质脱矿,其差异程度有统计学意义。     

A Comparative Micro-topographic Study of the Buccal Enamel of Different Tooth Types

Abstract

The aim of this study was to perform an in vitro examination of the etch pattern achieved on the orthodontic bonding area (OBA) of different tooth types, and to compare the extent and definition of etch achieved. Six examples of each permanent human tooth type were studied. These were collected from adolescents. A standardized etch regime was employed on the OBA and the etch pattern examined under the scanning electron microscope. The degree of definition of etch achieved on every third enamel prism was evaluated. Results showed that the extent of etch achieved decreased toward the distal end of each arch and was significantly less on the first molars (covering <2% OBA) than on the incisors (covering >90% OBA). It was also noted that the degree of definition became poorer towards the distal end of the arches and was worst on the mandibular molars.

It is suggested that the etched enamel morphology of different tooth types could affect composite resin bond strengths. Consequently, this feature could effect the clinical survival of orthodontic brackets and contribute to the higher failure rate of brackets on posterior teeth.     

不同邻面抛光方法对牙釉质表面粗糙度及表面形貌的影响

目的：评价4种邻面抛光方法对邻面釉质表面粗糙度及显微形貌的影响,为邻面抛光方法的选择提供依据。方法：选择21颗离体牙前磨牙,沿颊舌面中线纵剖后获得邻面釉质试件42枚,再用自凝塑料包埋,暴露邻面釉质,用浮石粉抛光,并超声清洗。将42个试样均分为6组,分别作如下处理：A组空白对照,不做处理;B组：阴性对照,采用标准金刚砂车针切磨触点及其周围釉质,切磨后不抛光;其余4组为实验组,经标准金刚砂车针切磨后分别采用以下方法抛光：C组：极细粒度金刚砂车针抛光;D组：裂钻抛光;E组：矽粒子抛光;F组：彩虹抛光条抛光。之后用粗糙度仪测定釉面粗糙度,并进行扫描电镜观察。结果：标准金刚砂车针切磨后粗糙度大幅度增加（P〈0.05）,釉质表面发生明显条形凹陷性缺损;经4种方法抛光后,釉质表面粗糙度均有显著下降（P〈0.05）,显微形貌均较阴性组光滑,其中矽粒子抛光组可达到较空白对照组更为光滑的表面。结论：实验涉及的4种不同邻面抛光方法均有助于降低釉质切磨区域的表面粗糙度,但抛光效果存在差异;采用矽粒子抛光可完全抵消牙体预备时旋转器械对邻牙邻面的切磨作用,获得最为光滑的釉质表面。     

不同食性哺乳动物牙釉柱与釉牙本质界夹角规律及有限元分析

目的：研究哺乳动物牙釉质微结构与其承载特性关系。方法：将搜集的西藏、新疆、江苏和吉林四省区14种哺乳动物的牙齿根据动物食性分为三类,设计了录像-截图-测量-标四步测量方法,依据测量得到的釉质结构数据设计了釉质的实体模型,用有限元分析方法对釉质模型做了力学模拟实验。结果：首次发现哺乳动物牙釉柱与釉牙本质界夹角的规律与动物食性有明显对应关系：食肉动物狗和人的釉柱角度最大,在90°左右;杂食动物野猪釉柱角度约为70;°食草动物釉柱角度在54°-68°之间。有限元分析表明釉柱晶体纤维排列方式和牙齿的承载特性的关系。结论：不同食性哺乳动物牙齿外在和内在结构都和其生物力学功能密切相关,其牙釉质的异型结构是有利于牙齿咀嚼受力的优化模式,推断食性作为主要因素在哺乳动物长期进化中决定了牙齿的形貌和结构。     

牙釉质与牙本质的透光率分析

目的：分析牙釉质及牙本质透光率与厚度和年龄的关系,为全瓷修复体更好模拟天然牙透光率提供实验基础。方法：利用爱色丽COlOri7分光光度仪分别对360例不同厚度（厚度为0．9mm、0．6mm、0．3ram）不同年龄（年龄范围13～71岁）的牙釉质、牙本质磨片进行透光率（T）的测量,采用SPSSl7．0软件对结果进行分析。结果：不同厚度的牙釉质及牙本质的透光率均存在显著差异,随厚度的减小而增大（P〈O．05）。牙釉质的透光率与年龄没有相关性,牙本质的透光率与年龄呈负相关（r=-0．401～-0．437）。相同厚度的牙釉质透光率均大于牙本质的透光率（P〈0．05）。结论：天然牙釉质与牙本质的透光率存在显著差异,并随厚度的变化而发生改变。牙本质的透光率随年龄增长而降低。因此,在全瓷修复时需选择不同透光率的底层瓷和饰瓷,并考虑其厚度比例以及不同年龄牙本质的透光率特性。     

不同浓度的含氟涂料对人牙釉质抗酸性的影响

目的：确定4种浓度的含氟涂料对人牙釉质抗酸性的影响。方法：采用22000ppm,10000ppm,5000ppm及2200ppm等4种不同浓度的含氟涂料处理离体人牙釉质后经脱矿实验，然后测量酸蚀液中钙的溶出量，并用激光荧光诊断仪对人工龋损进行定量诊断。结果：22000ppm组与10000ppm组的抗酸性无差别，而其余各组之间均有差别。结论：22000ppm及10000ppm的含氟涂料抑制牙釉质脱矿的效果比5000ppm及2200mmp的含氟涂料好，而将22000ppm的含氟涂料浓度降至10000ppm，并不影响它的防龋效果，因此，在临床应用时，可以考虑适应降低含氟涂氟浓度以提高安全性。     

Effect of sodium,amine and stannous fluoride at the same concentration and different pH on in vitro erosion

Objective

This study aimed to compare the effects 0.5% and 1% sodium, amine and stannous fluoride at different pH on enamel erosion in vitro.

Methods

Bovine enamel samples were submitted to a cyclic de- and remineralisation for 3 days. Each day, the samples were exposed for 120 min to pooled human saliva and subsequently treated with one of the fluoride solutions for 3 min: amine fluoride (AmF, 0.5% and 1% F⁻), sodium fluoride (NaF, 0.5% and 1% F⁻), each at pH 3.9 and 7.0, and stannous fluoride (SnF₂, 0.5% and 1% F⁻), at pH: 3.9. Additionally, two groups were treated with fluoride-free placebo solutions (pH: 3.9 and 7.0) and one group served as control (no fluoridation). Ten specimens each group were inserted in a so-called artificial mouth and eroded six times daily with hydrochloric acid (pH 2.6) for 90 s each intermitted by exposure to artificial saliva (1 h). After 3 days, enamel loss was analyzed profilometrically and evaluated statistically by ANOVA.

Results

Only the acidic 0.5% and 1% SnF₂ and 1% AmF solutions were able to reduce erosive enamel loss significantly, while all other solutions and placebos did not differ significantly from the control. Between the acidic SnF₂ and the 1% AmF solutions no significant differences could be detected.

Conclusion

At the same concentrations, acidic SnF₂ and AmF may be more effective than NaF to protect enamel against erosion.     

Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion

Objectives

Sn²⁺ has promising erosion-inhibiting properties in solutions, but little is known about respective effects in toothpastes. In addition, biopolymers might have protecting potential. Aim of this study was to investigate the effects of Sn²⁺ in toothpastes and of a biopolymer (chitosan) added to a Sn²⁺ formulation on erosion/abrasion.

Methods

Enamel samples were subjected to cyclic erosion procedures (10 days; 0.50% citric acid, pH 2.5; 6× 2 min/day), and brushing (2× 15 s/day, load 200 g) during immersion in slurries (2 min). The toothpastes were NaF formulations (NaF/1, NaF/2, NaF/3) and Sn²⁺ formulations (NaF/SnCl₂, AmF/SnF₂, AmF/NaF/SnCl₂) and AmF/NaF/SnCl₂ + 0.5% chitosan.Declared concentrations of active ingredients in toothpastes were 1400–1450 μg/g F⁻ and 3280–3500 μg/g Sn²⁺. Negative controls were erosion only and placebo, positive control was a SnF₂ gel. Tissue loss was quantified profilometrically, Sn on enamel surfaces was measured by energy dispersive X-ray spectroscopy.

Results

Loss values (μm) for erosion only and placebo were 14.4 ± 4.5 and 20.2 ± 3.8, respectively, and 4.6 ± 1.9 for the positive control (p ≤ 0.001 each compared to erosion only). The other loss values were: NaF/1 16.5 ± 3.0, NaF/2 14.0 ± 2.7, NaF/3 12.6 ± 3.9, NaF/SnCl₂ 14.7 ± 5.1, AmF/SnF₂ 13.5 ± 4.8, AmF/NaF/SnCl₂ 12.4 ± 4.2, AmF/NaF/SnCl₂ + chitosan 6.6 ± 3.5 (except NaF/1 all p ≤ 0.01 compared to placebo). AmF/NaF/SnCl₂/chitosan was more effective than all other toothpastes (p ≤ 0.01 each). Sn on the enamel surface ranged between 1.3 ± 0.3 and 2.8 ± 0.04 wt.% with no obvious relationship with efficacy.

Conclusions

The NaF and Sn²⁺ toothpastes without chitosan exhibited similar anti-erosion and abrasion-prevention effects. The experimental Sn²⁺ formulation with chitosan revealed promising results similar to those of the positive control.

Clinical significance

NaF toothpastes offer a degree of protection against erosion/abrasion, which is likely sufficient for most subjects with average acid exposures. For patients with initial erosive lesions, however, more effective toothpaste is desirable. The combination of Sn²⁺ and a biopolymer appears promising in this context.     

Enamel microstructure and microstrain in the fracture of human and pig molar cusps

The role of microstructure in enamel strain and breakage was investigated in human molar cusps and those of the pig, Sus scrofa. Rosette strain gauges were affixed to cusp surfaces (buccal human M3, n=15, and lingual pig M1, n=13), and a compressive load was applied to individual cusps using an MTS materials testing machine. Load and strain data were recorded simultaneously until cusp fracture, and these data were used to estimate enamel stresses, principal strains, and stiffness. Fractured and polished enamel fragments were examined in multiple planes using scanning electron microscopy (SEM). Human cusp enamel showed greater stiffness than pig enamel (P=0.02), and tensile stress at yield was higher (17.9 N/mm2 in humans versus 8.9 N/mm2 in pigs, P=0.06). SEM revealed enamel rod decussation in both human and pig enamel; however, only pig enamel showed a decussation plane between rod and inter-rod crystallites. Human inter-rod enamel was densely packed between rods, whereas in pig enamel, inter-rod enamel formed partitions between rows of enamel rods. Overall, human enamel structure enabled molar cusps to withstand horizontal tensile stress during both elastic and plastic phases of compressive loading. In contrast, pig cusp enamel was less resistant to horizontal tensile stresses, but appeared to fortify the enamel against crack propagation in multiple directions. These structural and biomechanical differences in cusp enamel are likely to reflect species-level differences in occlusal function.     

Bond strength and interfacial morphology of orthodontic brackets bonded to eroded enamel treated with calcium silicate–sodium phosphate salts or resin infiltration

Objective:To investigate the shear bond strength (SBS) of orthodontic brackets bonded to eroded enamel treated with preventive approaches and to examine the enamel/bracket interfaces.Materials and Methods:Ninety-one brackets were bonded to seven groups of enamel samples: sound; eroded; eroded+treated with calcium silicate–sodium phosphate salts (CSP); eroded+infiltrated by ICON^®; eroded+infiltrated by ICON^® and brackets bonded with 1-month delay; eroded+infiltrated by an experimental resin; and eroded+infiltrated by an experimental resin and brackets bonded with 1-month delay. For each group, 12 samples were tested in SBS and bond failure was assessed with the adhesive remnant index (ARI); one sample was examined using scanning electron microscopy (SEM).Results:Samples treated with CSP or infiltration showed no significant differences in SBS values with sound samples. Infiltrated samples followed by a delayed bonding showed lower SBS values. All of the values remained acceptable. The ARI scores were significantly higher for sound enamel, eroded, and treated with CSP groups than for all infiltrated samples. SEM examinations corroborated the findings.Conclusions:Using CSP or resin infiltration before orthodontic bonding does not jeopardize the bonding quality. The orthodontic bonding should be performed shortly after the resin infiltration.     

Enamel mineralization in the absence of maturation stage ameloblasts

The role of maturation stage ameloblasts is not clear yet. The aim of this study was to verify to which extent enamel mineralizes in the absence of these cells. Maturation stage ameloblasts and adjacent dental follicle cells from rat lower incisors were surgically removed and the limits of this removal were marked by notches made in the enamel. Histological analysis confirmed that the ameloblasts had been removed within the limits of the notches. The teeth erupted and when the notches appeared in the mouth, the enamel in the experimental teeth was hard but whitish compared to the yellowish colour of the contralateral incisors used as control. SEM images revealed similar enamel rod arrangement in both groups. Decreased mineral content was observed in some specimens by polarized light microscopy, and microhardness values were much lower in the experimental teeth. FTIR analysis showed that higher amounts of protein were found in most experimental teeth, compared with the control teeth. Enamel proteins could not be resolved on 15% SDS-PAGE gels, suggesting that most of them were below 5 kDa. These results suggest that the enamel matured in the absence of ameloblasts has increased protein content and a much lower mineral content, suggesting that maturation stage ameloblasts are essential for proper enamel mineralization.