Enamel roughness and depth profile after phosphoric acid etching of healthy and fluorotic enamel

Background: Dental fluorosis requires aesthetic treatment to improve appearance and etching of enamel surfaces with phosphoric acid is a key step for adhesive restorations. The aim of this study was to evaluate surface roughness and a depth profile in healthy and fluorotic enamel before and after phosphoric acid etching at 15, 30 and 60 seconds. Methods: One hundred and sixty enamel samples from third molars with no fluorosis to severe fluorosis were evaluated by atomic force microscopy. Results: Healthy enamel showed a statistically significant difference (p < 0.05) between mean surface roughness at 15 seconds (180.3 nm), 30 seconds (260.9 nm) and 60 seconds (346.5 nm); depth profiles revealed a significant difference for the 60 second treatment (4240.2 nm). For mild fluorosis, there was a statistically significant difference (p < 0.05) between mean surface roughness for 30 second (307.8 nm) and 60 second (346.6 nm) treatments; differences in depth profiles were statistically significant at 15 seconds (2546.7 nm), 30 seconds (3884.2 nm) and 60 seconds (3612.1 nm). For moderate fluorosis, a statistically significant difference (p < 0.05) was observed for surface roughness for 30 second (324.5 nm) and 60 second (396.6 nm) treatments. Conclusions: Surface roughness and depth profile analyses revealed that the best etching results were obtained at 15 seconds for the no fluorosis and mild fluorosis groups, and at 30 seconds for the moderate fluorosis group. Increasing the etching time for severe fluorosis decreased surface roughness and the depth profile, which suggests less micromechanical enamel retention for adhesive bonding applications.     

Oral characteristics of a patient with Ekman-Westborg-Julin trait: a case history

This article presents the case of a Japanese woman who had Ekman-Westborg-Julin trait. She had general macrodontia with multituberculism, evagination of the premolar, single conical roots, shovel-shaped incisors, enamel hypoplasia, impacted tooth, dental crowding, and an open bite. The oral and general characteristics of this patient are described and include the histological and radiographic findings of the mandibular third molars. We suggest that the distinctive oral features with macrodontia of the permanent teeth, multituberculism, evagination, single conical roots, and impaction of the tooth could be defined as the Ekman-Westborg-Julin trait.     

Disruption of enamel crystal formation quantified by synchrotron microdiffraction

Objectives

To understand the pathology of the ultrastructure of enamel affected by systemic disorders which disrupt enamel tissue formation in order to give insight into the precise mechanisms of matrix-mediated biomineralization in dental enamel in health and disease.

Methods

Two-dimensional synchrotron X-ray diffraction has been utilized as a sophisticated and useful technique to spatially quantify preferred orientation in mineralized healthy deciduous dental enamel, and the disrupted crystallite organization in enamel affected by a systemic disease affecting bone and dental mineralization (mucopolysaccharidosis Type IVA and Type II are used as examples). The lattice spacing of the hydroxyapatite phase, the crystallite size and aspect ratio, and the quantified preferred orientation of crystallites across whole intact tooth sections, have been determined using synchrotron microdiffraction.

Results

Significant differences in mineral crystallite orientation distribution of affected enamel have been observed compared to healthy mineralized tissue. The gradation of enamel crystal orientation seen in healthy tissue is absent in the affected enamel, indicating a continual disruption in the crystallite alignment during mineral formation.

Conclusions

This state of the art technique has the potential to provide a unique insight into the mechanisms leading to deranged enamel formation in a wide range of disease states.

Clinical relevance

Characterising crystal orientation patterns and geometry in health and following disruption can be a powerful tool in advancing our overall understanding of mechanisms leading to the tissue phenotypes seen clinically. Findings can be used to inform the appropriate dental management of these tissues and/or to investigate the influence of therapeutic interventions or external stressors which may impact on amelogenesis.     

Modification of tooth development by heat shock protein 60

Although several heat shock proteins have been investigated in relation to tooth development, no available information is available about the spatial and temporal expression pattern of heat shock protein 60 (Hsp 60). To characterize Hsp 60 expression in the structures of the developing tooth germ, we used Western blotting, immunohistochemistry and in situ hybridization. Hsp 60 was present in high amounts in the inner and outer enamel epithelia, enamel knot (EK) and stratum intermedium (SI). Hsp 60 also appeared in odontoblasts beginning in the bell stage. To obtain data on the possible effect of Hsp 60 on isolated lower incisors from mice, we performed in vitro culturing. To investigate the effect of exogenous Hsp 60 on the cell cycle during culturing, we used the 5-bromo-2- deoxyuridine (BrdU) incorporation test on dental cells. Exogenously administered Hsp 60 caused bluntness at the apical part of the 16.5-day-old tooth germs, but it did not influence the proliferation rate of dental cells. We identified the expression of Hsp 60 in the developing tooth germ, which was present in high concentrations in the inner and outer enamel epithelia, EK, SI and odontoblasts. High concentration of exogenous Hsp 60 can cause abnormal morphology of the tooth germ, but it did not influence the proliferation rate of the dental cells. Our results suggest that increased levels of Hsp 60 may cause abnormalities in the morphological development of the tooth germ and support the data on the significance of Hsp during the developmental processes.     

In vitro assessment of motility and proliferation of human osteogenic cells on different isolated extracellular matrix components compared with enamel matrix derivative by continuous single-cell observation

OBJECTIVES: The composition of the extracellular matrix (ECM) plays a substantial role in bone remodelling, fracture healing and osseointegration of dental implants by regulating proliferation, migration and finally differentiation of osteogenic cell populations. Emdogain, a composition of an enamel matrix derivative (EMD), has been introduced as a potential candidate to promote tissue regeneration. We investigated whether EMD could serve as a potential promoter of cell proliferation and motility as a dynamic cell response and compared the results with the ubiquitous single ECM components type I collagen and laminin. MATERIAL AND METHODS: In the investigation presented, we used a continuous observation method for the analysis of migratory and proliferative patterns of individual cells. We analyzed the response of four osteoblastic cell lines to specific extracellular ligands (type I collagen, laminin and EMD) over a period of 24 h compared with untreated glass surface and bovine serum albumin (BSA) as control groups. RESULTS: Type I collagen and laminin promoted cell motility significantly compared with the control groups and, in part, compared with EMD as well. The analysis of all 451 investigated cells revealed the following mean values for cell motiliy: untreated glass (n=99): 5.46+/-2.74 microm/h, BSA (n=89): 6.35+/-2.43 microm/h, type I collagen (n=108): 8.77+/-3.42 microm/h, laminin (n=74): 9.89+/-5.10 microm/h and EMD (n=81): 7.92+/-3.35 microm/h. Proliferation rates on the different surfaces were heterogenous for all investigated cell lines and varied from 0% to 50% within 24 h without a correlation to cell motility. CONCLUSION: In our study, EMD promotes cell motility better than the control groups. The two investigated single ECM components type I collagen and laminin promoted cell motility superior to EMD. This supports the hypothesis that EMD promotes a less mobile but more differentiated osteogenic phenotype.     

Surface Testing of Dental Biomaterials—Determination of Contact Angle and Surface Free Energy

The key goal of this study was to characterize surface properties of chosen dental materials on the base on the contact angle measurements and surface free energy calculations. Tested materials were incubated in the simulated oral environment and drinks to estimate an influence of conditions similar to those in the oral cavity on wetting and energetic state of the surface. Types of materials were as follows: denture acrylic resins, composite and PET-G dental retainer to compare basic materials used in a prosthetics, restorative dentistry and orthodontics. The sessile drop method was used to measure the contact angle with the use of several liquids. Values of the surface free energies were estimated based on the Owens–Wendt, van Oss–Chaudhury–Good and Zisman’s methods. The research showed that surface wetting depends on the material composition and storage conditions. The most significance changes of CA were observed for acrylic resins (84.7° ± 3.8° to 65.5° ± 3.5°) and composites (58.8° ± 4.1° to 49.1° ± 5.7°) stored in orange juice, and for retainers (81.9° ± 1.8° to 99.6° ± 4.5°) incubated in the saline solution. An analysis of the critical surface energy showed that acrylic materials are in the zone of good adhesion (values above 40 mJ/m²), while BIS-GMA composites are in the zone of poor adhesion (values below 30 mJ/m²). Study of the surface energy of different dental materials may contribute to the development of the thermodynamic model of bacterial adhesion, based on the surface free energies, and accelerate the investigation of biomaterial interaction in the biological environment.     

改性玻璃离子水门汀应力松弛蠕变实验

文题释义：黏弹性力学：连续介质力学的重要分支,又称黏弹性理论,研究黏弹性物质的力学行为、本构关系及其破坏规律,以及黏弹性体在外力和其他因素作用下的变形和应力分布。聚合物、混凝土、金属、岩石、土壤、石油、肌肉、血液和骨骼等,在一定条件下既具有弹性性质又具有黏性性质,这种兼具弹性和黏性性质的材料称为黏弹性材料,含黏弹性固体与黏弹性流体,又可分为线性黏弹性体和非线性黏弹性体。线性黏弹性体的两种极端情况即为胡克体(遵循胡克定律)和牛顿流体(遵循牛顿粘性定律)。 生物力学：是应用力学原理和方法对生物体中的力学问题定量研究的生物物理学分支,其研究范围从生物整体到系统、器官(包括血液、体液、脏器、骨骼等),从鸟飞、鱼游、鞭毛和纤毛运动到植物体液的输运等。 物力学的基础是能量守恒、动量定律、质量守恒三定律并加上描写物性的本构方程。生物力学研究的重点是与生理学、医学有关的力学问题,依研究对象的不同可分为生物流体力学、生物固体力学和运动生物力学等。 背景：以往对改性玻璃离子水门汀的力学性能研究多以压缩、弯曲实验居多,关于玻璃离子水门汀加入锶羟基磷灰石后的应力松弛、蠕变实验研究鲜有报道。 目的：对比分析传统玻璃离子水门汀、复合树脂釉质粘接剂、改性玻璃离子水门汀的应力松弛、蠕变特性。 方法：按质量比15%向玻璃离子水门汀中加入掺锶羟基磷灰石,制备改性玻璃离子水门汀。制作改性玻璃离子水门汀、复合树脂釉质粘接剂与传统玻璃离子水门汀试样,3组各取10个试样进行应力松弛实验,另取10个试样进行蠕变实验。 结果与结论：①应力松弛实验7 200 s时,传统玻璃离子水门汀组应力下降了1.18 MPa,复合树脂釉质粘接剂组应力下降了1.39 MPa,掺锶羟基磷灰石复合玻璃离子水门汀组应力下降了1.38 MPa;传统玻璃离子水门汀组应力下降量小于掺锶羟基磷灰石复合玻璃离子水门汀组、复合树脂釉质粘接剂组(P < 0.05),掺锶羟基磷灰石复合玻璃离子水门汀组和复合树脂釉质粘接剂组应力下降量无差异(P > 0.05)。②蠕变实验7 200 s时,传统玻璃离子水门汀组应变上升了0.24%,复合树脂釉质粘接剂组应变上升了0.33%,掺锶羟基磷灰石复合玻璃离子水门汀组应变上升了0.32%;传统玻璃离子水门汀组应变上升量小于掺锶羟基磷灰石复合玻璃离子水门汀组、复合树脂釉质粘接剂组(P < 0.05),掺锶羟基磷灰石复合玻璃离子水门汀组试和复合树脂釉质粘接剂组应变上升量无差异(P > 0.05)。③结果表明,15%掺锶羟基磷灰石提高和改善了玻璃离子水门汀的黏弹特性,有利于其与黏结物体的黏结,有利于提高黏结强度。 ORCID: 0000-0003-1024-5733(丁洁) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程