Polarized light study of giant tubules in human and red deer coronal dentin

Abstract – Previously described giant tubules in human and red deer coronal dentin have been subjected to a study by polarized light microscopy. Structure of the giant tubules was similar in both species. The lumen of each tubule was bordered by a 5–15-μm-thick collagenous mantle in which the fibers were orientated parallel to its long axis. In a circular dentin area encompassing the mantle, the course of the collagen fibers might be characterized as a winding of fibers around the cylindrical mantle. This structure of the giant tubules conforms with that described earlier in the rudimentary maxillary canine of a red deer. Thus, such tubules do not represent a rare anomaly, but occur regularly in both human and red deer coronal dentin.     

A light microscopical and microradiographic study of coronal dentin in red deer with special reference to the occurrence of giant tubules

Abstract – The coronal dentin of red deer (Cervus elaphus L.) was studied by light microscopy and microradiography. The material consisted of incisors from 10 animals, 2½–6½ years of age. Sections in the long axes of the crowns in the buccolingual and mesiodistal planes were prepared, as well as transverse sections. A few crowns were also examined in toto. A system of giant tubules of the same type as in human dentin is described. It was, however, characterized by more regularity in the number and the morphology of the tubules. As in human dentin, the giant tubules extended from the border of the pulpal cavity and could be followed, though not continuously, through secondary and primary dentin almost to the incisal dentinoenamel junction. Up to 60 giant tubules could be counted in the mesiodistal axis of the dentin. Contrary to the situation in man, areas of interglobular dentin were abundant in the crowns.     

乳牙牙本质钙元素的电子探针测定及其与龋病的关系

目的：探讨钙元素在乳牙牙本质内的分布及其与龋病易感性之间的关系方法：用电子探针显微分析仪测量38个离体的下颌乳中切牙各侧面(唇侧、舌侧、近中侧、远中侧)和不同深度的牙本质钙含量，分无龋组与有龋组，统计分析牙本质钙含量及其与龋病易感性之间的关系。结果：乳牙牙本质钙含量在不同轴面是不同的，唇侧最高，近中侧最低；牙本质从外层到内层钙含量逐渐升高；无龋组和有龋组之间牙本质钙含量无显著性差异；牙本质的钙含量与龋补牙数(dft)、龋补牙面数(dfs)和龋增指数(CSI)无相关性。结论：钙元素含量在乳牙牙本质不同侧面和不同深度具有差异，乳牙牙本质的钙元素含量与龋病易感性无关。     

Sealer distribution in coronal dentin

A major cause of tooth discoloration is sealer remnants in the pulp chamber after root canal treatment. The purpose of this study was to assess coronal distribution and color changes of four commonly used sealers placed in the pulp chamber after 2 yr. Fifty extracted premolars were cross-sectioned in the coronal third of the root. The chamber contents were removed, and instrumentation was via the canal; then freshly mixed sealer was placed in each chamber. Sealers evaluated were: AH 26, Kerr Pulp Canal Sealer, Roth 801, and Sealapex. The apical access was sealed with white sticky wax, and the tooth was maintained in a moist environment at 37 degrees C for 2 yr. Teeth were split longitudinally, and digital images of the exposed dentin were made, scrambled, and evaluated blindly by trained evaluators for color changes and for presence of sealer in dentin. There was no measurable penetration of sealer into dentin for all groups and no dentin discoloration occurred. The sealers displayed marked discoloration. At 2 yr, the sealers discolored and remained confined primarily to the pulp chamber.     

Scanning electron and incident light microscopy of giant tubules in red deer dentin

Abstract – Incisal and cuspal teeth from red deers 2½–6½ yr of age were used in this study. Incident light microscopy was used for screening of the specimens with respect to presence of orifices and exposures of giant tubules. Scanning electron microscopy (SEM) was used for study of structural details. For SEM the specimens were pretreated with a 1% solution of NaCIO for 2 or 20 h. One specimen was in addition exposed to a 35% solution of phosphoric acid for 30 s. Two teeth received no pretreatment. Many incisal/occlusal exposures of giant tubules were more or less blocked by a dense, probably mineralized, substance, whereas others were filled with spherical bodies, probably microorganisms. The walls of the pulpal chambers and root canals revealed an abundance of orifices of giant tubules. They were funnel-shaped with circular or oblong pulpal outlines, the diameters of which in untreated specimens ranged from 15 to 100 μm.     

Microradiographic and polarized light study of red deer root dentin with special reference to occurrence of giant tubules

Abstract – Radiolucent bands following the course of the dentinal tubules were observed in sections of undemineralized roots of permanent red deer incisors. Some of these bands, previously unreported in mammalian root dentin, contained giant tubules similar to those described earlier by the author in the coronal dentin of this animal. The root giant tubules initiated with funnelshaped orifices at the border of the pulpal cavity and, generally, terminated in the peripheral dentin, whereas a few penetrated into the cementum. Whether the giant tubules should be considered to be anomalous dentinal tubules or a different type of structure could not be determined. The distinction between root giant tubules and accessory canals being part of the apical ramification did not represent any problem.     

Ultrastructural observations on human coronal dentin

abstract – The incisal area of the coronal dentin of intact anterior teeth was studied by means of scanning and transmission electron microscopy. The great majority of the tubules were open regardless of age. A variety of fibrous structures with diameters between 50 nm and 0.7 μm were observed within dentinal tubules. The cross-banding typical of collagen was occasionally discernible in these fibers, but as a rule they had a smooth surface, probably due to masking of structural details by ground substance. Fibers with a tendency to arboresce were interpreted as nerve fibers. Disturbances in the mineralization were observed in a central area of the dentin between the pulp horn and the incisal edge. Especially the development of peritubular dentin was inconsistent. In adult teeth the tubules at this location were occluded by a fine-textured material. A varying amount of secondary dentin was present in the pulp horn of the teeth at an early age. The first formed tissue had an atubular appearance, whereas in an apical direction the structure became more regular with tubules and intertubular areas.     

Immunohistochemical localization of matrixmetalloproteinase-2 in human coronal dentin

While it is known that matrixmetalloproteinase-2 (MMP-2) is present in dentin, its distribution and role in human dentin formation and pathology are not well understood. OBJECTIVE: To characterize the distribution of MMP-2 in human coronal dentin. METHODS: Immunohistochemistry was used to investigate the distribution of MMP-2 in coronal dentin. Freshly extracted human premolars and third molars (age range 12-30) were fixed with formaldehyde, demineralized with 10% EDTA (pH 7.4) and embedded in paraffin. Serial sections were made and subjected to immunohistochemical analysis using a specific monoclonal anti-MMP-2 antibody. Immunoreactivity was visualized with 3,3'-diaminobenzidine substrate and observed under light microscopy. ImageJ software was used to calculate the relative amount/distribution of MMP-2. RESULTS: The analysis revealed immunoreactivity for MMP-2 throughout human coronal dentin. However, intense immunoreactivities were identified in a 90-200 microm zone adjacent to the pre-dentin as well as a 9-10 microm wide zone adjacent to the dentinoenamel junction (DEJ). CONCLUSION: MMP-2 has a specific distribution in human coronal dentin indicating it's involvement in extracellular matrix organization in predentin and the establishment of the DEJ.     

Vital staining of coronal dentin in monkey teeth.

Vital staining of monkey incisor teeth with the incisal dentin exposed to the oral environment by attrition was carried out, with the use of a number of dyes (pH and redox indicators). There was a distinct staining of the coronal dentin, regardless of which dye was introduced into the pulpal cavity. The exposed dentin was stained like the unaffected dentin, with the exception of a narrow centrally located zone that extended from the tip of the original pulp horn to the incisal edge of the tooth. The suggestion is that this zone is not unstained because of exposure of the dentin to the oral environment, but because it coincides with an area of the tissue where the pulpal ends of the dentinal tubules are blocked by atubular hard tissue normally laid down in the pulp horn of incisor teeth.     

Anisotropic fracture in bovine root and coronal dentin.

OBJECTIVES: This purpose of this study was to address the fundamental question of how the fracture properties of dentin are related to its composite structure. METHODS: Strain concentration tests and impression-induced damage tests were designed to compare bovine root dentin with coronal dentin, and to understand the role of individual structural elements in the fracture of dentin. RESULTS: Absent in peritubular dentin, root dentin is insensitive to cracks and exhibits higher fracture resistance than coronal dentin that has a typical brittle fracture behavior along the peritubular dentin. Fracture analysis and impression damage experiments found that root dentin is highly anisotropic in fracture behavior. Cracking is predominantly controlled by the organization of collagen fibrils, with the incremental lines being the weakest planes. In coronal dentin, highly mineralized peritubular dentin that intersects with the incremental lines creates additional weak orientations that compete with the incremental lines and thus greatly decrease the degree of fracture anisotropy. SIGNIFICANCE: This study demonstrated that dentin is by no means homogeneous in terms of fracture properties. Location and orientation (especially in terms of incremental lines) should be taken into account when examining tooth failure both in laboratory and in clinical studies.