Photomechanical investigations on post endodontically rehabilitated teeth

An investigation of the stress distribution patterns in post-core restored teeth and the behavior of dentin material to fracture propagation was conducted using experimental techniques such as digital photoelasticity (on photoelastic models), mechanical testing and scanning electron microscopy (SEM) (on extracted teeth). Digital photoelastic experiments showed that endodontic post-core restoration resulted in regions of high tensile stress and of stress concentrations in the remaining dentin structure. It was observed from mechanical testing that the fracture resistance in post-core restored teeth is significantly lower (p<0.0001) than that in intact tooth. There was a significant correspondence between the plane of stress concentrations identified in the photoelastic models and in those of the plane of fracture exhibited by the rehabilitated tooth specimens. While the fracture of post-core rehabilitated teeth was consistent, that of control teeth was not as distinct. The SEM highlighted varying dentin response to fracture propagation at the inner core and the outer regions. The fractographs showed brittle and ductile response to fracture propagation in the outer and inner core dentin, respectively. These photomechanical studies highlighted that the stress concentrations, high tensile stress and loss of inner ductile dentin associated with post endodontic rehabilitation diminished their resistance to fracture.     

Three-dimensional topographic scanning electron microscope and Raman spectroscopic analyses of the irradiation effect on teeth by Nd:YAG, Er: YAG, and CO(2) lasers

A three-dimensional analyzer installed in a scanning electron microscope was used to evaluate the morphology and surface roughness using noncontact profilometry. Observations were carried out on the enamel and dentin surface irradiated by three different lasers: Nd:YAG (wavelength 1.06 microm), Er:YAG (2.94 microm), and CO(2) (10.6 microm). Spectroscopic analysis was done by Raman spectroscopy for nonirradiated and laser-irradiated surfaces. The lasers were applied perpendicularly to vertically sectioned and polished human extracted caries-free molars. The tooth was sectioned at each cavity for cross-section analysis after laser irradiation. Irradiation by Nd:YAG and CO(2) lasers of the enamel surface showed an opaque white color, different from dentin where the surface turned black. The Er:YAG laser induced no changes in color of the dentin. Numerous cracks associated with thermal stress were observed in the CO(2) laser-irradiated dentin. Noncontact surface profile analysis of Er:YAG laser-irradiated enamel and dentin showed the deepest cavities, and direct cross-sectional observations of them showed similar cavity outlines. The CO(2) laser-irradiated dentin had the least surface roughness. Raman spectroscopic analysis showed that fluorescence from the laser-irradiated tooth was generally greater than from nonirradiated teeth. Bands in dentin attributed to organic collagen matrix were lost after Nd:YAG and CO(2) laser irradiation, and a broad peak due to amorphous carbon appeared. The Er:YAG laser-irradiated dentin showed no sign of a carbon band and had more suitable results for dental ablation. Noncontact surface profile analysis was effective to evaluate the structural change in the tooth in the microarea of study after laser irradiation.     

Ca/P mol ratio of cries-affected dentin structures

BACKGROUND: A new approach called "minimum intervention" has been introduced for restoration of carious lesions to preserve tooth structure. This approach suggests that perhaps caries need not always be removed completely from deeper portions of the cavity. It is, therefore, important to characterize caries-affected dentin structures, because of the potential changes in bonding quality when using different dentinal substrates. MATERIALS AND METHOD: Ninety teeth (30 teeth each group) were studied. The first group (CF) consisted of 30 caries-free teeth. The second group (CC) consisted of 30 teeth, for which caries-free dentin teeth was chemically demineralized. The third group (ND) consisted of 30 extracted human molars with coronal carious lesions. After all tooth samples were water-polished with grit #600 SiC paper, they were tested by surface contact angle measurements and the electron-probe microanalyzer to measure Ca/P mol ratio. RESULTS: Contact angles were CF = 60.07 degrees ; CC = 30.8 degrees; ND = 26.11 degrees , p<0.05. Ca/P mol ratios were as follows; CF = 1.549 (+/-0.0435); CC = 1.324 (+/-0.2305); ND = 1.568 (+/-0.0523), p<0.05. Weibull analyses for Ca/P mol ratio indicated shape parameter (m) of CF was 13.3; it was 12.8 for ND and 11.8 for CC. Above the delta point (=1.65 in Ca/P ratio), for both groups m = 3.4. CONCLUSION: Caries-affected dentin surfaces (naturally-developed and chemically created) were statistically more chemically active than caries-free dentin surface. Ca/P mol ratio of chemically created caries was less than other two groups.     

Metal-catalyzed peroxidation of polyunsaturated fatty acids

In this study malondialdehyde (MDA) was measured as the thiobarbituric acid (TBA) adduct by high performance liquid chromatography with linolenic acid (LA), as well as with LA to which the following metal ions were added: Ag+1, Al+3, As+5, Ba+2, Cd+2, Co+2, Cu+1, Cu+2, Fe+2, Fe+3, Hg+2, Mn+2, Ni+2, Pb+2, and Zn+2. Our results showed that Fe+3 is a particularly potent catalyst of this oxidation reaction. Several other metals also significantly increased the production of MDA over LA alone, as shown by the Mann-Whitney test, including Al+3 and Fe+2 (p less than 0.001), Cu+2, Ba+2, Mn+2 (p less than 0.01), and As+5 (p less than 0.05). Pb+2 almost completely inhibited the production of MDA from LA (p less than 0.001). Addition of the free radical scavenger, butylated hydroxytoluene (BHT), significantly inhibited MDA formation in these latter reactions, indicating they are free-radical mediated. Pre-incubation of the reaction mixtures at 37 degrees C and physiologic pH with both Fe+2 and Fe+3 greatly increased MDA formation, suggesting that in acute metal toxicity the initiating free-radical process might be primarily due to direct metal catalysis of preformed lipid peroxides.     

Dentin phosphoprotein compound mutation in dentin sialophosphoprotein causes dentinogenesis imperfecta type III

A rare compound mutation involving a 36 bp deletion and 18 bp insertion within exon 5 of the dentin sialophosphoprotein (DSPP) gene has been identified in a family with dentinogenesis imperfecta type III (DGI-III). The DSPP gene encodes two major tooth matrix proteins dentin sialoprotein (DSP) and dentin phosphoprotein (DPP). DSPP mutations associated with DGI-III results in an in frame truncation of the serine aspartic acid triplet repeat found in DPP near the highly conserved carboxyl terminal region shortening the protein by six amino acids. Clinically this family presents with discolored amber opalescent teeth and severe attrition of the tooth structure. This study is the first report of a mutation within DPP associated with a genetic dentin disease. Our study indicates that DGI-III is allelic with some forms of DGI-II with and without progressive hearing loss and dentin dysplasia type II that have been shown to be caused by mutations within the DSP coding or signal peptide regions.     

Comparative Qualitative and Quantitative Assessment of Biomineralization of Tooth Development in Man and Zebrafish (Danio rerio)

It was the aim of this study to investigate the distribution of Ca, P, and C in predentin, mineralizing dentin, and mature dentin of human tooth buds and compare these results with those of zebrafish (Danio rerio) teeth using energy dispersive X‐ray analysis (EDX) element analysis. The mandible of a 16‐week‐old human fetus containing 6 mineralizing tooth buds and three complete heads of zebrafish were fixed in formaldehyde and embedded in Technovit 9100. Serial sections of 80‐μm thickness were cut in frontal‐dorsal direction, and from these sections, polarized light micrographs were taken. The sections with tooth buds were then investigated with scanning electron microscopy, and EDX element analysis was performed with a Philips XL 30 FEG scanning microscope and an EDAX energy‐dispersive X‐ray system using spot measurements, EDX line‐scans and element mapping. Quantitative measurements were made in predentin, mineralizing dentin adjacent to predentin, and mature dentin. The Ca and P content increased rapidly from outer predentin toward mineralizing dentin in human tooth buds and in zebrafish teeth. The Ca/P ratio was different for predentin and dentin areas, reflecting different calcium phosphate compositions in predentin and fully mineralized dentin. Because of the similarities between human tooth buds and zebrafish teeth, it can be concluded that the zebrafish tooth development may be an excellent model for studying biomineralization processes during odontogenesis. Anat Rec, 291:571–576, 2008. © 2008 Wiley‐Liss, Inc.     

Ti-Fe-Mo-Mn-Nb-Zr合金在不同pH值乳酸中的腐蚀性能研究

对应口腔环境中 p H值发生明显变化以及形成龋齿的自然现象 ,采用加速试验法研究了新型钛合金在不同 p H值乳酸中浸泡的耐腐蚀性能。研究表明当 p H=4即酸性略高于龋齿发病时酸性条件下 ,新型牙科钛合金能够完全耐乳酸腐蚀。在乳酸中腐蚀形式以点蚀为主 ,且随酸性增强有向晶间腐蚀转变的趋势。ICP分析表明合金在乳酸中的溶解析出物主要是 Fe,Fe的加入不利于合金的耐腐蚀性能。热力学计算表明设计的新型钛合金氧化膜含有 Mn2 O3、Nb2 O5、Zr O2 和 Ti O2 中的全部或部分 ,XPS分析表明氧化膜中的确含有 Mn2 O3、Nb2 O5和 Ti O2 ,主要是 Ti O2 。这三种氧化物致密且 Ti O2 和 Nb2 O5耐腐蚀 ,有利于合金的耐腐蚀性能。     

Preparation of a hydroxyapatite and hydrogen peroxide composite for tooth whitening

Hydroxyapatite (HA)/Hydrogen Peroxide (H(2)O(2)) solutions was prepared for a tooth whitening application. HA powder was immersed in the 100, 1000 and 10,000 ppm of the H(2)O(2) solutions. The HA/H(2)O(2), HA and H(2)O(2) solutions were applied to HA discs and extracted teeth for weight and whiteness change evaluation. After 24 hours, each HA disc was measured for the weight changes and each tooth was measured for the whitening changes (L(*)) using a Spectro Color Meter. The topology of the teeth surfaces were also observed using Scanning Electron Microscope (SEM). The weight of the HA disc applied with H(2)O(2) at all concentrations was lower than that applied with HA and HA/H(2)O(2) solutions. The whiteness of the teeth treated with HA/H(2)O(2) were higher than that treated with HA and H(2)O(2) only solutions. The whiteness change of the teeth treated with the HA/H(2)O(2) (10,000 ppm) showed the highest value in all solutions at L(*)=4.98+/-0.90 (p<0.05). In the SEM observation, the teeth surface treated with the H(2)O(2) showed rough and destructive holes on the enamel surface. However, the teeth surface treated with the HA/H(2)O(2) show smooth enamel surface due to covering of the destructive holes with HA powder.     

Protections by non-copper metal ions against copper-mediated inactivation of poliovirion RNA occurring at extraction of virions with phenol

Al3+, Ca2+, Co2+, Cu1+, Fe2+, Fe3+, Mg2+, Mn2+, Ni2+, Pb2+, Sn4+, and Zn2+ were incubated individually with redistilled reagent-grade phenol containing impurities known from previous work to interact with Cu2+ to produce a potent inactivator(s) of the transfectivity of naked poliovirion RNA. Only the mixture with Cu1+ inactivated the RNA. Tests of each of the 11 non-copper test metal ions mixed with Cu2+ before adding the phenol showed that Ca2+ and Mg2+ do not protect, Co2+, Mn2+, Ni2+, Pb2+, and Zn2+ provide moderate protection, and Al3+, Fe2+, Fe3+, and Sn4+ give strong protection against the Cu2+-mediated inactivation. Other points of addition of protective metal ion were tested using Fe3+. Strong protection was afforded even when Fe3+ was added after synthesis of the inactivator(s) from Cu2+ and the active impurities. The relation between Cu2+ and the Fe3+ was shown to be competitive. The hypothesis that ions compete for semi-quinone anion is proposed.     

Comparative antiviral (HIV) photoactivity of metalized meso- tetraphenylsulfonated porphyrins

We have carried out the study of the photochemical properties of a series of synthetic meso-tetraphenylsulfonated porphyrins (TPPMS4) bonded to several metal ions such as: Cu(II), Zn(II), Pd(II), Mn(II), Fe(III), Ni(II) and Co(II) for the optimization of their clinical applications as antiviral agents against the human immunodeficiency virus (HIV-1) as well as the study of the in vitro antiviral photoinactivation mechanisms with future application in blood sterilization. A selective inhibition has been determined in the viral growth (HIV-1) when this is irradiated in the presence of the complex TPPFeS4 and TPPMnS4 (photosensitizer-mediated Type I reaction) as well as in the 1O2-mediated (Type II reaction) in the presence of TPPPdS4 and TPPZnS4, remaining cellular viability unaltered in each case.     

Hardness, elasticity, and ultrastructure of bonded sound and caries-affected primary tooth dentin

Biomechanical properties of bonded dentin are important factors for resin restoration. We evaluated the hardness and elastic modulus of bonded sound and caries-affected primary tooth dentin using a one-step adhesive system, and observed the microstructure of the bonded interface. Six sound and six carious primary teeth were used. For sound teeth, flat occlusal dentin surfaces were prepared with a water-cooled high-speed diamond bur. For carious teeth, infected dentin was stained with a caries detector and removed with a water-cooled low-speed round steel bur and hand instruments. The prepared dentin was bonded with One-Up Bond F Plus (Tokuyama Dental Co., Tokyo, Japan). The resin-dentin interface and dentin beneath the interface were measured with a nano-indentation tester and observed with SEM and TEM. For both the carious and sound teeth, there was no significant difference between the hardness of the interfacial dentin and dentin 10-80 microm beneath the interface. However, the Young's modulus of the interfacial dentin was significantly lower than the dentin 40-80 microm (carious teeth) or 50-80 microm (sound teeth) beneath the interface. Both the hardness and Young's modulus of the interfacial dentin were not significantly different between the carious and sound teeth. Compared to the sound dentin, the hybrid layer on the caries-affected dentin was thicker and exhibited more complicated morphologic features. The thickness of the hybrid layers was generally less than 1 microm.     

Coordination polymers of 1,2,5,8-tetrahydroxyanthraquinone

From analytical studies, infrared and reflectance spectra, magnetic and thermogravimetric measurements of Cu(II), Ni(II), Co(II), Mn(II), Fe(II), and UO₂(VI) complexes of 1,2,5,8-tetrahydroxyanthraquinone, it was concluded that the complexes are polymeric coordination complexes with octahedral geometry. These were synthesized by refluxing an equimolar mixture of the ligand and hydrated metal acetates in N,N-dimethylformamide at 140°C. Elemental analyses indicated a ligand: metal ratio of 1 : 1 and the association of water molecules with the central metal. The decreasing order of thermal stability of the complexes is: Mn(360°C)>Fe(340°C) ≈? Co(340°C)>Ni(320°C)>Cu(300°C).     

The genetic basis of inherited anomalies of the teeth. Part 1: clinical and molecular aspects of non-syndromic dental disorders

The genetic control of dental development represents a complex series of events, which can very schematically be divided in two pathways: specification of type, size and position of each dental organ, and specific processes for the formation of enamel and dentin. Several genes linked with early tooth positioning and development, belong to signalling pathways and have morphogenesis regulatory functions in morphogenesis of other organs where they are associated with the signalling pathways. Their mutations often show ple?otropic effects beyond dental morphogenesis resulting in syndromic developmental disorders. Some genes affecting early tooth development (MSX1, AXIN2) are associated with tooth agenesis and systemic features (cleft palate, colorectal cancer). By contrast, genes involved in enamel (AMELX, ENAM, MMP20, and KLK4) and dentin (DSPP) structures are highly specific for tooth. Mutations in these genes have been identified as causes of amelogenesis imperfecta, dentinogenesis imperfecta, dentin dysplasias and anomalies of teeth number (hypo-, oligo and anodontia), which only partially overlap with the classical phenotypic classifications of dental disorders. This review of genetic basis of inherited anomalies describes, in this first paper, the molecular bases and clinical features of inherited non-syndromic teeth disorders. And in a second part, the review focus on genetic syndromes with dental involvement.     

Laser-induced fluorescence and X-ray spectral analysis of carious process in hard dental tissues

Morphological and spectral X-ray analysis of carious and noncarious extracted teeth showed the patterns of dentin ossification in caries of different degree. Parietal ectopic ossification of the canal and cavity lumens in stages III and IV dental caries is regarded as a specific structural marker of pathological regeneration. The X-ray spectral analysis showed that the progress of carious process is paralleled by loss of mineral components. Laser-induced fluorescent study of tissues in extracted teeth showed 4 spectral bands corresponding to mineral and protein components of the tooth. The progress of carious process was associated with reduction of the fluorescence intensities of the spectral bands characteristic of dental collagen and mineral components.     

A novel <Emphasis Type="Italic">DSPP</Emphasis>mutation is associated with type II dentinogenesis Imperfecta in a chinese family

Background  

Hereditary defects of tooth dentin are classified into two main groups: dentin dysplasia (DD) (types I and II) and dentinogenesis imperfecta (DGI) (types I, II, and III). Type II DGI is one of the most common tooth defects with an autosomal dominant mode of inheritance. One disease-causing gene, the dentin sialophosphoprotein (DSPP) gene, has been reported for type II DGI.     

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: compositional, structural, and phase changes of DP-bioglass paste after irradiation by CO2 laser

Nowadays, fractured teeth are difficult to treat effectively. Currently, root fractures are usually treated by root amputation, hemisection or tooth extraction. If the fusion of tooth fracture by laser were possible, it would offer a different therapy to repair fracture teeth. We tried to use a developed DP-bioactive glass paste to fuse or bridge the tooth crack line by a medium energy continuous-wave CO2 laser. The study is divided into three parts: (1) The compositional and structure changes in tooth enamel and dentin after laser treatment; (2) The phase transformation and recrystallization of DP-bioactive paste during exposure to the CO2 laser; (3) The thermal interactions and bridge mechanism between DP-bioactive glass paste and enamel/dentin when they are subjected to CO2 laser. The present report will focus on the second part that will examine the changes of laser-exposed DP-bioactive glass paste by means of X-ray diffractometer (XRD), Fourier transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). From the study, we could find that the temperature increase due to laser irradiation is greater than 900 degrees C and that the DP-bioactive glass paste could be melted in a short period of time after irradiation. In the study, we successfully developed a DP-bioactive glass paste which could form a melting glass within seconds after exposure to a medium energy density continuous-wave CO2 laser. The paste will be used in the near future to bridge the enamel or dentin surface crack by the continuous-wave CO2 laser.     

Acquisition of Mn(II) in addition to Fe(II) is required for full virulence of Salmonella enterica serovar Typhimurium

The roles of the genes feoB (ABC ferrous iron transporter), mntH (proton-dependent manganese transporter), and sitABCD (putative ABC iron and/or manganese transporter) in Salmonella pathogenicity were investigated by using mutant strains deficient in one, two, or three transporters. Our results indicated that sitABCD encodes an important transporter of Mn(II) and Fe(II) which is required for full virulence in susceptible animals (Nramp1(-/-)) and for replication inside Nramp1(-/-) macrophages in vitro. The mntH sitABCD double mutant (mutant MS) showed minimal Mn(II) uptake and increased sensitivity to H(2)O(2) and to the divalent metal chelator 2,2'-dipyridyl (DP) and was defective for replication in macrophages. In vivo MS appeared to be as virulent as the sitABCD mutant in Nramp1(-/-) animals. The ferrous iron transporter Feo was required for full virulence in 129/Sv Nramp1(-/-) mice, and infection with multiple mutants lacking FeoB was not fatal. The sitABCD feoB mutant (mutant SF) and the mntH sitABCD feoB mutant (mutant MSF) showed minimal Fe(II) uptake and were slightly impaired for replication in susceptible macrophages. MSF showed reduced growth in minimal medium deficient in divalent cations. The role of the mntH gene, which is homologous to mammalian Nramp genes, was also investigated after overexpression in the double mutant MS. MntH preferred Mn(II) over Fe(II) and could suppress MS sensitivity to H(2)O(2) and to DP, and it also improved the intracellular survival in Nramp1(-/-) macrophages. This study indicates that acquisition of Mn(II), in addition to Fe(II), is required for intracellular survival and replication of Salmonella enterica serovar Typhimurium in macrophages in vitro and for virulence in vivo.     

Quantitative analysis of the calcium and phosphorus content of developing and permanent human teeth.

It was the aim of this study to investigate the distribution of Ca, P and C in predentin, dentin and enamel in human tooth buds and permanent teeth by EDX element analysis. The mandible of a 16-week-old human fetus containing eight mineralizing tooth buds and three human permanent molars were fixed in formaldehyde and embedded in Technovit 9100. Serial sections of 80 microm thickness of the mandible were cut in the frontal-dorsal direction, and polarized light micrographs were taken of these sections. The permanent teeth were cut in mesio-distal direction. The sections were investigated with scanning electron microscopy and EDX element analysis with a Philips XL 30 FEG scanning microscope and an EDAX energy-dispersive X-ray system using spot measurements, EDX line-scans and element mapping. Quantitative measurements were made in predentin, mineralizing dentin adjacent to predentin, mature dentin, mineralizing enamel and young enamel of developing teeth and mature enamel of permanent teeth. In developing teeth the Ca and P content increased rapidly from outer predentin towards mineralizing dentin. In enamel prisms of developing teeth the Ca and P content increased linearly from the surface towards the enamel-dentin junction. In permanent teeth only a small layer of predentin was found. The Ca and P content in enamel and circumpulpal dentin of permanent teeth was higher than in developing teeth. The Ca/P ratio differed between predentin and dentin areas reflecting different calcium phosphate compositions, but it was the same in mineralizing and young enamel. The differences in the distribution of Ca and P reflect different mineralizing patterns of the enamel and dentin matrices.     

牙本质保护膜对牙本质小管的封闭作用**

背景：有临床研究报道牙本质保护膜在用于烤瓷全冠牙体预备后牙本质面的保护处理后,能有效降低基牙敏感度。 目的：体外实验观察牙本质保护膜封闭牙本质小管的效果。 方法：将20颗完好离体人前磨牙分为3组：空白对照组牙本质表面不作任何处理,对照组牙本质表面涂布格鲁玛脱敏剂,实验组牙本质表面涂布牙本质保护膜,在扫描电镜下观察牙本质小管口封闭情况。 结果与结论：扫描式电子显微镜观察显示,实验组牙本质小管口密度和直径均明显低于对照组与空白对照组(P < 0.05),牙本质小管口相对面积明显低于空白对照组(P < 0.01)。表明牙本质保护膜在减小牙本质小管的密度和直径方面的作用优于格鲁玛脱敏剂。     

Mutual wear evaluation of resin composites when opposing enamel and dentin

Mutual wear rates of resin composites and both superficial and deep layers of enamel and dentin were investigated by means of an in vitro wear test. Occlusal surfaces of extracted molars were ground flat to respective layers of enamel and dentin. Hemispherical-shaped styli (n = 8) made of microfilled and microhybrid composites were placed perpendicular to the finished tooth surface (600 grit) in the presence of tap water, and a two-body wear test (75 N load and 1.2 Hz) was performed for 100,000 cycles. The wear depths on both tooth and composite specimens were determined, and the data were statistically analyzed by two-way ANOVA and Boneferroni test (p < 0.05). The values of deep and superficial dentin specimens against Esthet-X (530.2 +/- 213.0 microm and 717.4 +/- 309.6 microm) were significantly greater than those against Epic-TMPT (34.1 +/- 17.6 microm and 29.3 +/- 10.8 microm). The values of Esthet-X against dentin were the smallest (2.4-2.6 microm), followed by those of the same material against enamel (5.5-6.1 microm), and those of Epic-TMPT against enamel (7.2-7.9 microm). It was concluded that the wear rates of dentin varied with the type of composite used while those of enamel showed the consistency.