Glycoproteins in the dentine of human deciduous teeth.

Dentine from permanent and deciduous human teeth was demineralized with EDTA. The EDTA extracts were fractionated by gradient elution from DEAE-cellulose which revealed a peak in the extract of deciduous dentine which was absent from that of permanent dentine. Subsequent fractionation by gel-filtration and ion-exchange chromatography resulted in the isolation of two, apparently homogeneous, glycoproteins. The major component differed considerably from known glycoproteins of mineralized tissues, while a minor component was closely akin to certain dentine phosphoproteins in amino acid composition.     

Chemical composition and structure of peritubular and intertubular human dentine revisited

ObjectiveCurrently there is still a debate about whether peritubular dentine (PTD) is non-collageneous or collageneous tissue. The chemical composition and structure of human PTD and intertubular dentine (ITD) was re-visited in this study.DesignThe dentine tubular region including ITD and PTD prepared from human third molars was in situ detected by means of micro-Raman spectroscopy (μRs) and atomic force microscopy (AFM).ResultsFrom the μRs study, it was found that the mineral/matrix ratios (phosphate vs. CH₂) in PTD were ～3 times of those in ITD. For the mineral, the differences between PTD and ITD were small, but still detectable. For the organic matrix, the intensity ratios of amide III to CH₂ in ITD were ～1.5 times of those in PTD, indicating the structural differences. In addition, there was a higher proline/hydroxyproline content in ITD than that in PTD. However, the overall Raman peak contour in the amide regions (I &; III) was similar, indicating collagen might still exist in both the ITD and PTD. An in situ AFM observation of the dentinal tubular region during EDTA etching confirmed that dentine collagen ran across from the ITD into the PTD.ConclusionA phenomenon similar to that observed in the dentine–enamel junction is proposed to explain the above results. It is demonstrated that the μRs–AFM approach can be used to provide an insight into the structure of small dental tissues at the micron or sub-micron scale.     

A histochemical study of the intertubular and peritubular matrices in normal human dentine

Serial ground sections of sound, recently erupted human teeth were stained with 0.0005 M methylene blue, 0.01–0.1% toluidine blue, 0.05–0.5% alcian blue at pH 2.6, 3.6 and 7.0, and with the periodic acid-Schiff method.

With methylene blue at pH 2.6 and 3.6, a zone of dentine about 20–25 μ wide, immediately adjacent to the predentine, was stained. The staining was in the intertubular matrix which also stained intensely with alcian blue and the PAS method and showed metachromasia at pH 3.6 with toluicline blue. This zone may represent the “intermediate dentine” of other workers, and appears to be rich in polysaccharide and especially in acid mucopolysaccharide. The rest of the intertubular matrix, external to the first zone, showed practically no staining with methylene blue or toluicline blue at pH 2.6 or 3.6, and a reduction in the depth of PAS staining. It is considered that calcification of the intertubular dentine is virtually completed in the first zone.

The peritubular matrix first appeared about 60–100 μ from the predentine-dentine junction and quickly reached its full width. The peritubular matrix stained intensely and metachromatically with methylene blue and toluicline blue at pH 2.6 and 3.6 and deeply with alcian blue at 2.6. Observations made suggest that the peritubular matrix rapidly attains a high level of calcification.

The formation and calcification of the intertubular and peritubular matrices appear to be entirely separate stages in dentine development.     

Difficulties in estimating age using root dentine translucency in human teeth of varying antiquity

Estimation of age at death is an essential part of reconstructing information from skeletal material. This becomes more difficult after development has ceased and following taphonomic alteration in archaeological material. Most biological markers of age do not record the chronological age (calendar age), but the biological or physiological age of the individual. Of the age-related changes in the mature dentition of modern samples, the extent of root dentine translucency (RDT) has been shown to correlate closely with chronological age. A protocol for measurement of RDT was established and applied to modern and archaeological teeth of known age (Spitalfields sample). Percentage length of RDT in sectioned teeth was found to correlate well with chronological age in the modern sample but not in the archaeological sample. The majority of the archaeological sample was affected by a morphological change creating a "chalky" appearance to the dentine. Removal of the obviously affected teeth did not improve the correlation coefficients to any useful degree. "Chalky" dentine appeared, under the light microscope, to be composed of large fenestrations, islands of mineralized tissue and masses of filiform structures that appeared to be following the path of the dentinal tubules in their invasion of the peripheral dentine. The filiform structures are consistent in their appearance with a previously reported tunnelling mycelium and impart such an effect on RDT that it cannot readily be used for age estimation in affected teeth.     

A scanning electron microscopic observation of etched human peritubular dentine

Thirty permanent human teeth were fractured immediately after extraction and fixed with 10 per cent neutral formalin or cold acetone. The fractured surfaces were etched with 1/20 N and 1/200 N formic acid for 5–20 and 30–200 sec, coated with gold and the fractured surfaces of the dentine were studied with a scanning electron microscope.

In the dentine, intertubular dentine, peritubular dentine and Tomes fibres were distinguishable with these techniques. While the entire peritubular dentine showed a mild resistance to acid treatment, a layer of greater insolubility was also found contiguous upon the dentinal tubules. This probably represents an inner hypomineralized layer.     

Amino acid composition of dentine in permanent human teeth.

Dentine of permanent mandibular incisors from nine individuals was hydrolysed and the amino acid composition determined by ion-exchange chromatography against a standard calibrant of 41 amino acids. Nineteen amino acids were detected, including small quantities of 1-methylhistidine and asparagine, two amino acids whose existence had apparently not been recorded before in human dentine. The total content of hydroxylysine plus lysine varied between 2.6 and 3.3 residues per 100 (SD, 0.74) in different teeth, which therefore did not support previous studies that had proposed a constant total value. This and other quantifiable differences between present and previous findings may be the result of the different methods and the influence of dietary and other regional factors on dentinogenesis.     

Regional distribution of interglobular dentine in human teeth

Interglobular dentine (IGD) is an area of poorly mineralized dentine matrix. It has been reported that there is an association between the retraction of odontoblast processes (OP) and the formation of IGD. A variation of the extent of OP has been described depending on the region of the tooth and age. This study aimed to find out the regional distribution of IGD in human teeth to observe any association between the extent of OP and the pattern of distribution of IGD.Ground sections were prepared from 52 extracted permanent teeth and the presence of IGD was observed in different regions of the crown and the root.The highest occurrence of IGD was found in the cervical and middle thirds followed by intercuspal, and coronal third in the crown. Statistical analysis of data depicted that the occurrence of IGD differed according to the region of the tooth. In roots, the highest occurrence of IGD was seen in the cervical third followed by the middle third.Previous reports have shown that OP extend up to the dentine–enamel junction in the coronal region and to the inner one-third of the cervical region. The varied pattern of distribution of IGD in the crown and root observed in our results corresponds to the above findings. Therefore, it is reasonable to surmise that there is an association between the distribution of IGD and the extent of OP. This allows us to confer that IGD tends to form in areas where OP do not extend to the dentine–enamel junction.     

Distribution of corrosion products in teeth restored with metal crowns retained by stainless steel posts.

The nature and distribution of corrosion products in teeth restored with metal crowns retained by stainless steel posts were examined by means of energy-dispersive X-ray microanalysis, microradiography, and electron microscopy. The corrosion products consisted of calcium, phosphorous, iron, chromium, nickel, zinc, stannum and other elements. A possible root fracturing mechanism is discussed.     

Fracture resistance of pulpless teeth restored with post-cores and crowns.

OBJECTIVES: The present study was designed to test the null hypothesis that there is no difference in the fracture resistance of pulpless teeth restored with different types of post-core systems and full coverage crowns. METHODS: Extracted human upper premolars were restored with a fiber post, prefabricated metallic post or cast metallic post-core. Teeth with full crown preparations without post-core restorations served as a control. All teeth were restored with full coverage crowns. A 90-degree vertical or 45-degree oblique load was applied to the restored teeth with a crosshead speed of 0.5 mm/min, and the fracture loads and mode of fracture were recorded. RESULTS: Under the condition of vertical loading, the fracture load of teeth restored with the cast metallic post-cores was greatest among the groups (two-factor factorial ANOVA and Scheffe's F test, P<0.05). All fractures in teeth restored with all types of post-core systems propagated in the middle portions of roots, including the apices of the posts. Under the condition of oblique loading, the fracture load of teeth restored with pre-fabricated metallic posts was significantly smaller than that in other groups. Two-thirds of fractures in the fiber post group propagated within the cervical area, while most fractures in other groups extended beyond the middle of the roots. SIGNIFICANCE: From the results of the present investigations, it was concluded that under the conditions of vertical and oblique loadings, the combination of a fiber post and composite resin core with a full cast crown is most protective of the remaining tooth structure.     

Age and gender influence on lead accumulation in root dentine of human permanent teeth.

143 permanent teeth of individuals aged 14-60 yr from a non-occupationally exposed population in northern Israel were analysed for lead accumulation in a atomic absorption spectrophotometer graphite-furnace. A significant correlation was established between lead level and age. No gender correlation was found. The results suggest that any study dealing with lead accumulation in different populations has to compare groups of the same age range, ignoring the sex of the individuals.     

The histology and microbiology of acute occlusal dentine lesions in human permanent molar teeth.

Acute occlusal caries of molar teeth was investigated and on microscopic examination a pattern was seen in the bacterial invasion of the tissue. A primary wave of bacterial attack, found by bacteriological isolation techniques to consist of homofermentative lactobacilli, was demonstrated at the advancing periphery of the lesion. A secondary wave of mixed superinfection followed the primary invasion. The two zones of infection could be clearly identified because there was a bacteria-free interval between them and because there were histological characteristics exclusive to each.