High-resolution micro-CT scanning as an innovative tool for evaluating dental hard tissue development.

Microcomputerized tomography (micro-CT) allows discriminating very smal lchanges in dental hard tissue volumes. The aim of the present study was to create a new method for obtaining high-resolution, three-dimensional images of dental hard tissue development using micro-CT, and to observe the changes in dental hard tissue development and composition in growing rat pups. Tooth germs from rats at the end of the 20-day embryonic period (E20) and during the neonatal period (D1-14) were subjected to micro-CT. Three-dimensional reconstructions were analyzed to compare dental hard tissue formation and mineralization during the different development periods. Scanning electron microscopy and energy dispersive spectroscopy were used to confirm mineral density (MD). Dental hard tissue began to form during the E20, but the process was slow and resulted in minimal deposition. Hard tissue volume increased by approximately 0.040 mm3/day from E20 to D3, and by 0.12-0.42 mm3/day after D3, peaking at 0.42 mm3/day at D12. This increase in hard tissue volume resulted in continuous increases in hard tissue thickness, from 90.0 ± 20.7 µm at E20 to 545.2 ± 14.1 µm by D14. MD was 298 ± 3.1 mg HA/cm at E20 and increased to 678.2 ± 6.1 mg HA/cm by D14. The degree of calcification also progressively increased during the first 14 days of development. Dental MD was strongly associated with calcification. This study indicates that micro-CT is a nondestructive, high-resolution, reliable, and innovative tool for the evaluation of volume and MD of dental hard tissues during development. Micro-CT minimizes artifacts caused by sample preparation.

Candidate-gene exclusion in a family with inherited non-syndromic dental disorders.

OBJECTIVES: Amelogenesis imperfecta, dentinogenesis imperfecta, and dentin dysplasia are the most common non-syndromic dental disorders. In this study, we analysed and localised the gene(s) responsible for inherited non-syndromic dental disorders in a Chinese family. METHODS: This study identified and researched non-syndromic dental disorders in a four-generation Chinese family, including four affected individuals whose clinical phenotype was atypical. Linkage analysis with seven polymorphic markers that localise to six different autochromosomes showed that the family was linked through chromosome 4q. All exons and exon-intron boundaries of dentin sialophosphoprotein (DSPP), enamelin (ENAM), and ameloblastin (AMBN), which are located on chromosome 4q, were sequenced in nine of the family members. RESULTS: Direct DNA sequence analysis revealed the existence of a G to A transversion in exon 4 (g.13081786G>A, c.727G>A, p.Asp243Asn, based on reference sequences NM_014208.3) of the DSPP gene, and this sequence variation correlated exactly with the presence of the disease. CONCLUSION: These results indicate that mutation p.Asp243Asn is a highly probable cause of non-syndromic dental disorder in this Chinese family. The presence of symptom heterogeneity is possible, as the clinical classification system is hampered by the lack of close correlation between the subtype and the molecular defect.

The morphology and mineralization of dental hard tissue in the offspring of passive smoking rats.

OBJECTIVE: To study the effects of maternal passive smoking on the morphology and mineralization of dental hard tissue in offspring rats. DESIGN: We have established a maternal passive smoking model. Offspring rats were sacrificed on the 20th day of gestation (E20) or the 3rd (D3) or 10th day (D10) after birth. We observed hard tissue morphology using Haematoxylin-Eosin (H&E) staining sections, used micro computer tomography (Micro-CT) to measure hard tissue thickness and volume on the mandibular first molars of the offspring rats, and used Micro-CT and energy dispersive X-ray spectroscopy with scanning electron microscopy (SEM/EDS) to determine the hard tissue mineral density and the ratio of calcium atom number/calcium atom+phosphorus atom number (Ca(2+)/P(3-)+Ca(2+)). RESULTS: Overall, the development of dental hard tissue was delayed in the offspring of passive smoking rats. The thickness and volume of hard tissue were lower in the offspring of the maternal passive smoking group than in the offspring of the control group. Mineral density of the hard tissue and the ratio of (Ca(2+)/P(3-)+Ca(2+)) were also reduced in the offspring of the maternal passive smoking group. CONCLUSION: Maternal passive smoking inhibits the morphological development and mineralization level of hard tissue on the mandibular first molars of offspring rats.

Angiotensin II induces interleukin-6 synthesis in osteoblasts through ERK1/2 pathway via AT1 receptor.

BACKGROUND: Interleukin-6 (IL-6) is a potent stimulator of osteoclastic bone resorption. Osteoblast secretion of IL-6 plays an important role in the regulation of bone metabolism. Angiotensin II (Ang II) has been shown to regulate the expression of potent inflammatory factors, including MCP-1 and IL-6, by stimulating endothelial cells, vascular smooth muscle cells (VSMC) and monocytes. However, of the mechanism by which Ang II regulates IL-6 expression in osteoblasts is unknown. AIMS: The present study was designed to investigate the effect of Ang II on IL-6 expression in osteoblasts isolated from mice. The receptor(s) required and the potential role of extracellular signal-regulated kinase 1/2 (ERK1/2) activation in Ang II-induced IL-6 synthesis was also examined in these cells. METHODS: The osteoblasts were isolated from the calvaria of mice and cultured in α-MEM medium. IL-6 mRNA expression and protein synthesis was determined by qPCR and ELISA analyses. ERK1/2 kinase activation was determined by western blot. RESULTS: The results indicate that Ang II induced IL-6 mRNA expression and protein synthesis in cultured osteoblasts. However, these effects were abolished by pre-treatment with Ang II type 1 (AT1) receptor antagonist, losartan, and the ERK1/2 inhibitor, U0126, inhibited Ang II-mediated IL-6 expression and the phosphorylation of ERK1/2. CONCLUSION: Ang II induces the synthesis of IL-6 in osteoblasts through activation of the ERK1/2 pathway via the AT1 receptor.

[Study on color matching of equal volume in dental ceramic prothesis materials].

OBJECTIVE: To study the color changes on brightness and hue in dental ceramic prothesis materials. METHODS: The different color mark of VINTAGE series was sintered on 15 pieces Ni-Cr alloy denture materials. The sample group and control group was given the sintering of color blending with equivalent volume. The order of color mark was of A1 and A2, A2 and A3, A3 and A4, B1 and B2, B2 and B3, B3 and B4 in sample group, and A1, A2, A3, A3.5, A4, B1, B2, B3 and B4 orderly in control group. The chromatic analysis on samples of VITA had been taken through applying PR 650 spectrum detector and adopted the statistic software of Photo Research and SPSS 12.0 for analysis. RESULTS: The statistical difference (P<0.05) of L*a*b* value was found in the different color mark of the same color serials. A non-linearity relation had been found in the chromatic parameters a*b*. It means the change of color was visible. CONCLUSION: Set A has a bigger grading change of brightness than Set B. The change of red-green is obviously in Set A, as well as yellow-blue in Set B.

[Clinical application and processing of separate movable partial denture].

OBJECTIVE: This report is to introduce the processing method of the separate movable partial denture and get an initial clinical evaluation. METHODS: The separate movable partial denture was developed as a kind of special design in utilizing double base plate to separately get support for bearing stress and get the stability of retention. RESULTS: The clinical application indicated that the separate movable partial denture has effective function of common movable partial denture as well as has a good function of natural human teeth protection, especially for those patients with I -II tooth loose. CONCLUSION: The separate movable partial denture is the ideal choice of treatment for those patients who are suffering I - II teeth loose. This type of movable partial denture was considered effectively protect natural human teeth and extend the lifetime of natural tooth long-term and further observation in clinical care on this type of denture is needed.

[Study on different thickness and chromatics of various opaques].

OBJECTIVE: To study the effect existed in the course of adopting different thickness and chromatics of various opaques so that a good methods can be provided for clinical care in prosthodontics. METHODS: A model of using the thin plastic paper to control the ceramic thickness was applied in this test. The data of chromaticity was measured by TC-PIIG auto color difference meter and its results was processed by computer. RESULTS: The value of brightness had an uptrend increase with augment of opaques thickness. Metal base color was opaqued and the basic hue was set. A lower and unstable value, besides a relative stable Y, was measured with the uncompleted opaquing. A stability of hue had been gradually concentrated within a certain range accompanying with the increase of opaquing ceramic thickness. A concentrated hue in the second thickness was found in CARAT ceramic which had high ability of opaque and had a stable hue of ceramic in comparison with other opaques. Among those changes, CARAT's brightness showed a minimal change; a gradual stability of chromatics was presented and was limited with-in a certain range though the augment of opaques. CONCLUSION: The metal color in base could be completely opaqued while opaques thickness reaches a certain range. CARAT is the materials of minimal thickness and has relatively strong capacity for opaques.

[Short-term follow-up study of Cercon all-ceramic crowns and bridges].

OBJECTIVE: Cercon all-ceramic system was applied clinically for the first time to make all-ceramic crowns and bridges for the patients. The objective of this study was to evaluate the short-term follow-up results of this new system from both technical and clinical aspects. METHODS: 15 units of Cercon all-ceramic crowns and bridges were fabricated and applied to 5 patients, all the cases were followed at 1, 3, 6 and 12 months' periods after cementation of the restorations. RESULTS: Cercon all-ceramic system demonstrate natural and esthetical appearance. No fracture, broken and color change were found. CONCLUSION: The reliability of all-ceramic crowns and bridges made from Cercon system was greatly improved due to the strengthening effects of the zirconia copings and substructures, and the indication of this system can be extended to long span posterior bridges. In addition, the better esthetics compared to PFM technique makes it a comparatively ideal all-ceramic system for crowns and bridges.

[The study on color space of the VINTAGE & UNIBOND standard color].

OBJECTIVE: To research the color space of the standard color board, guide the clinic work of color match, and establish an foundation for deeper researching. METHODS: Through taking analysis of reflecting spectrum and spectral tristimulus, each parameter of the color on standard board was found out. The color difference between border upon colors on board was worked out through matching the color parameters. The number of color space between each border upon color on standard color board, divided by deltaE = 1.5, was found. RESULTS: The number of color space between each border upon color was 3-6. The color space was bigger in group B, but smaller in group D. The color space was bigger in high lightness area, but smaller in low lightness area. CONCLUSION: Some color space has been found between standard color borders of VINTAGE and UNIBOND. Color of natural teeth is unable to be completely included into standard color border, especially in clinical care.