Scanning electron microscopy of the substructure of smear layers in human dentine

Smear-layer debris was sonicated from dentine surfaces and trapped on microfilters for microscopy, which showed that the layers are composed, in part, of aggregates of globular subunits approx. 0.05-0.1 micron in diameter. Such globules were also seen in smear layers in situ and on fractured dentine surfaces. The composition of smear layers may reflect the substructure of dentine matrix.     

Scanning electron microscopy evaluation of aligner fit on teeth

Objectives:The fitting of aligners on anchorage teeth is a crucial factor in clear aligner orthodontics. The purpose of this experimental study was to evaluate the fitting of two aligner systems, Invisalign and CA-Clear Aligner, using scanning electron microscopy (SEM).Materials and Methods:Passive aligners (Invisalign and CA-Clear Aligner) were adapted on resin casts obtained by stereolithography (STL) files of a patient, and then sectioned buccolingually. Upper and lower central incisors, upper and lower first premolars, and upper and lower first molars were the regions analyzed. Representative microphotographs of sections were taken with a scanning electron microscope (SEM); a total of 160 micrometric measurements were obtained and analyzed with ANOVA tests.Results:Invisalign provided an overall better fit on lower incisors (F = 11.48, P = .0095) and on lower molars (F = 19.93, P = .0012). Considering the different regions, Invisalign provided better fit at the gingival edge of the buccal aspect on lower incisors (F = 11.33, P = 0.0056) and at the gingival edge of the lingual aspect on upper premolars (F =5.34, P = 0.0047). On the upper molars, Invisalign provided better fit at the gingival edge of the buccal aspect, while CA-Clear Aligner provided better fit at the buccal maximum convexity, on the buccal cusp, on the occlusal groove and at the palatal cusp. On lower molars, Invisalign showed a more accurate fit at the buccal aspect points.Conclusions:Invisalign and CA-Clear Aligner exhibited comparable fit on anchorage teeth. Invisalign provided better fit at the gingival edges of aligners, while the CA-Clear Aligner provided better fit on complex occlusal surfaces.     

Scanning electron microscopy of developing human deciduous incisor teeth

The mineralized parts of the teeth of 17 human fetal dentitions, aged 15-38 weeks, were measured mesio-distally and occluso-cervically. The growth pattern of the incisors, with particular emphasis on the changes at the developing incisal edge was studied. Contralateral teeth in the same arch developed at approximately the same rate and with mirror-image morphology. Mineralization started in the upper and lower central incisors, followed by the corresponding lateral incisors. It then progressed at approximately the same rate for both incisors. At first, mesio-distal enamel growth was more significant, but was surpassed by occluso-cervical development later. Five development stages were identified as the incisors developed from a central lobe to the mature form. The main component of growth for the mesial lobe was in the incisal direction, and for the distal lobe in a distal direction, resulting in the characteristic approximal asymmetry of these teeth.     

Scanning electron microscopy of the walls of tubules in human coronal dentine

Twenty-one fully-formed healthy human premolars were fixed, resin-impregnated and freeze-fractured. Specimens were critical-point dried. The wall of the dentinal tubules was lined with a two-layered structure which extended from the pulp-predentine border to the dentine-enamel junction; there was a fibrous outer layer and an amorphous, membrane-like inner layer. The lining sheath was separated from the odontoblast process by a space which widened toward the outer surface of the dentine, although occasionally in the mid and outer dentine the lumen was constricted by transverse septa of the sheath which were in close proximity with the odontoblast process. Some tubules were divided into a system of chambers by transverse extensions of the membrane-like inner layer of the sheath.     

Scanning electron microscopy of human dentine specimens fractured in bend and torsion tests

Dentine specimens fractured by bend and torsion tests were examined by scanning electron microscopy. Fractures occurred in planes both perpendicular and parallel to both the long axes of the specimens and the general direction of the tubules, i.e. independently of tubule direction. Dentine may be regarded as isotropic in this respect. The overall appearance of the fracture plane was dependent upon the mode of deformation.     

Scanning electron microscopy of enamel tuft development in human deciduous teeth

The presence of hypomineralized tuft-like structures in the innermost layer of enamel has been well accepted. However, the development of these structures and their preference for the location adjacent to the dentine-enamel junction is not well understood. Enamel of the developing deciduous dentition of an 8.5 month fetus was examined with the scanning electron microscope in various stages of development. The morphology of the junctional mantle dentine, the nascent junctional enamel as well as subsequent enamel layers was studied. Comparisons were made between the corrugated developing enamel surface area and the clefts that were seen in longitudinally and transversely fractured sections of further-mineralized enamel. This study suggests that tuft formation is based on morphological features of junctional enamel and underlying dentine. The abrupt change in the direction of bundles of enamel prisms and the different ratio of interprismatic and prismatic enamel yield less mineralized, weakened enamel planes. Furthermore, because of the unique fitting of dentine ridges in the junctional enamel, fibrous incorporations are frequently encountered in these areas, thus providing additional organic content in the tuft planes.     

Scanning electron microscopy of attrited dentinal surfaces and subjacent dentin in human teeth

abstract – Attrited dentinal surfaces and subjacent dentin were examined in the scanning electron microscope. In a central area of the exposed surfaces the dentinal tubules were occluded, whereas peripherally most tubules were open. Deposits, apparently dental plaque, were observed on the exposed dentin as uneven, but often continuous, layers covering whole areas of the surfaces. Loss of dentin within delimited areas of the surfaces was observed. The resulting defects could hardly be related to attrition, and it seemed that they were caused by erosive or caries-like processes. The dentin subjacent to the attrited surfaces was characterized by mineralized inclusions in the dentinal tubules. The inclusions consisted of irregularly rod-shaped crystals forming a meshwork on the tubule walls. Other crystals were formed as prisms, seemingly rhombohedrons. Crystals which were hexagonal in cross-section were also seen. The exposure of the dentin also seemed to have influence on the organic content of the tubules. Thus, it appeared that ground substance was removed from the intratubular fibers permitting the observation of cross-banding typical of collagen at their surfaces. In some tubules the fibers seemed to be covered by mineral.     

Three-dimensional replicas of pits and fissures in human teeth: Scanning electron microscopy study

For providing a three dimensional display of pits and fissures, a study was carried out on human permanent unerupted molar and premolar teeth. The technique of vinyl resin replication was used. The specimens were examined with optical and scanning electron microscopy. The results suggest caution in the interpretation of pit and fissure morphology by serial sectioning. The study showed that the morphology of pits and fissures is extremely complex. Furthermore, the morphology varies from tooth to tooth. The implication of this for current and past operative procedures as well as conservative procedures involving these sites is discussed.     

Scanning electron microscopy (SEM) investigation of selected desensitizing agents in the dentine disc model

Abstract— Dentine sensitivity is a painful clinical condition that can affect up to 35% of the population at any one time. Both professionally available (in-office) or commercially available (over-the-counter) products have been used to treat dentine sensitivity. The aim of the present study was to investigate whether selected in-office desensitizing agents occluded dentine tubules in the dentine disc model. Both surface effects and tubule penetration of the five selected test products were examined by scanning electron microscopy. The results of the present study appeared to demonstrate that all of the applied desensitizing agents produced some occlusion of the tubules although the level of coverage and occlusion vaned between the products. Of all the agents tested, ferric oxalate, the active ingredient of Sensodyne Sealant, produced crystal-like structures which occluded a higher proportion of the tubules across the dentine disc surface. ALL-BOND 2 and One-Step (both light-cured primer systems) produced similar crystal-like structures and, although coverage was not uniform across the disc surface, there was some reduction in tubule diameter. These three products, however, appeared to be more effective than either Butler Protect (potassium oxalate) or Oxa-gel (potassium oxalate in a gel) where there was a marked decrease in both the level of coverage and tubule occlusion. Both quantitative and functional studies are required in order to determine the effects of these agents on dentine permeability (fluid flow) as well as clinical studies to determine their effectiveness over time in reducing pain arising from dentine sensitivity.     

Scanning electron microscopy (SEM) investigation of selected desensitizing agents in the dentine disc model

Dentine sensitivity is a painful clinical conditions that can affect up to 35% of the population at any one time. Both professionally available (in-office) or commercially available (over-the-counter) products have been used to treat dentine sensitivity. The aim of the present study was to investigate whether selected in-office desensitizing agents occluded dentine tubules in the dentine disc model. Both surface effects and tubule penetration of the five selected test products were examined by scanning electron microscopy. The results of the present study appeared to demonstrate that all of the applied desensitizing agents produced some occlusion of the tubules although the level of coverage and occlusion varied between the products. Of all the agents tested, ferric oxalate, the active ingredient of Sensodyne Sealant, produced crystal-like structures which occluded a higher proportion of the tubules across the dentine disc surface. ALL-BOND 2 and One-Step (both light-cured primer systems) produced similar crystal-like structures and, although coverage was not uniform across the disc surface, there was some reduction in tubule diameter. These three products, however, appeared to be more effective than either Butler Protect (potassium oxalate) or Oxa-gel (potassium oxalate in a gel) where there was a marked decrease in both the level of coverage and tubule occlusion. Both quantitative and functional studies are required in order to determine the effects of these agents on dentine permeability (fluid flow) as well as clinical studies to determine their effectiveness over time in reducing pain arising from dentine sensitivity.     

Scanning electron microscopy of organic structures on the root surface of human teeth

abstract – The surface morphology of fibers, vessels, nerves and cells located on the surface of 29 human teeth was studied in the scanning electron microscope. The length of the torn principal fibers was about 250 μm. They tapered with the widest diameter near the cementum. The principal fiber bundles were composed of smaller elements with a diameter of 4–5 μm which were composed of fibrils with a diameter up to about 5,000 Å. Adjacent to the cementum the principal fiber bundles interlaced with thin fibrous elements, and thus a fibrous coating covered the root surface. The size of the interlacing fibrils varied, and those with a diameter of 500 Å exhibited a cross-striation with a periodicity of 600 Å. The surface of the vessels had a dense appearance. Nerve fibers and nerve endings were observed. In one case there was a peculiar branching of structural elements that could be identified as nerve tissue. Cell cultures of chicken fibroblasts were studied for comparison with cells from the root surface with regard to shape and size. Both had a rough surface, a central nuclear region and long, fairly straight celltails.     

乳牙恒牙龋化学机械法去腐的扫描电镜观察

目的:观察Carisolv化学机械去腐技术和慢速球钻去腐后及酸蚀后的窝洞表面形态。方法:新鲜拔除且有冠部中、深龋的24颗恒牙和12颗乳牙,其中12颗恒牙和6颗乳牙用Carisolv化学机械法,其余牙用慢速球钻法去腐,扫描电镜(SEM)观察去腐后窝洞表面形态以及恒牙酸蚀后的形态。结果:恒牙和乳牙用慢速球钻去腐后牙本质表面几乎全部为玷污层覆盖,很少见到牙本质小管开口;Carisolv去腐后的表面玷污层很少,牙本质小管开口开放,很少见到管栓。慢速球钻或化学机械去腐后用磷酸酸蚀均可以去除窝洞表面的玷污层。结论:Carisolv化学机械去腐效果优于球钻,磷酸酸蚀可增强去污效果。