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PubMed1988

A longitudinal study of dentine lead levels, intelligence, school performance and behaviour. Part II. Dentine lead and cognitive ability.

The relationship between dentine lead levels and measures of cognitive ability was examined for a birth cohort of New Zealand children studied until the age of 9. There were small, consistent and stable correlations between dentine lead measures and all measures of cognitive ability including intelligence, word recognition and teacher ratings of school performance. After adjustment for the effects of confounding covariates, sample selection factors and possible reverse causal effects, the correlations between intelligence and dentine lead levels became non-significant. However, small but statistically significant correlations persisted between dentine lead values and all measures of school performance after adjustment for sources of confounding. It is concluded that the weight of the evidence from this analysis favours the hypothesis that low level lead exposure may have deleterious effects on levels of achievement in children.

Achievement↗
PubMed1980

Immunohistochemical localization of Type III collagen in the dentin of patients with osteogenesis imperfecta and hereditary opalescent dentin.

The immunohistochemical localization of Type III collagen was studied in the dentin from nine patients with dominantly inherited osteogenesis imperfecta (O.I.) and six patients with hereditary opalescent dentin (H.O.D.). The most consistent localization of Type III collagen was found in patients with O.I. Among these patients an indirect relationship existed between the severity of dentinal involvement and the presence of Type III antibody localization. Although a similar but less intense staining could be observed in some cases of H.O.D., the severity of dentinal alterations in H.O.D. was not correlative to the quantitative presence of material reacting with antibodies to Type III collagen. These observations further indicate that O.I. is not only clinically, but biochemically, a heterogeneous condition.

Adolescent↗
PubMed1983

The detection and prevalence of reactive and physiologic sclerotic dentin, reparative dentin and dead tracts beneath various types of dental lesions according to tooth surface and age.

The pulpo-dentinal complex responds to external injuries with dentin sclerosis (DS), dead tracts (DT), or reparative dentin (RD). This investigation correlates the prevalence of these responses with age, sex, type and surface location of tooth lesions (caries, restorations, attrition, abrasion and erosion) utilizing ground sections, microradiographs and decalcified paraffin-embedded tooth sections treated with the Pollak trichrome stains (270 teeth from 113 patients). The main response to caries, restorations and erosion was DS, followed by RD and DT. DS, RD and DT occurred equally in any tooth, on any tooth surface and even beneath the same lesion. DS did not necessarily prevent RD. Root and furcation DS and RD in the floor of the pulp chamber and root canals were unrelated to particular lesions but did relate to increasing age. Root DS extended from apical to cervical area with increasing age. Beneath caries and restorations DS and RD were more prevalent in males, but DT was more prevalent in females. Pollak staining of decalcified paraffin sections for DS was approximately 80% as accurate as ground sections and microradiography. In pulp studies, where the result is contrary to previous experience, the Pollak stains reveal whether DS has decreased dentin permeability.

Adolescent↗
PubMed1989

A search for the osteogenic factor in dentin. Rat incisor dentin contains a factor stimulating rat muscle cells in vitro to incorporate sulfate into an altered proteoglycan.

Demineralized dentin matrix has the capacity to induce bone formation via a chondrogenic pathway when implanted into muscle, in a fashion entirely analogous to bone matrix implants. In this work we have attempted to isolate, from rat incisor dentin, the matrix factor responsible for initiating osteogenesis. Rat incisor dentin was demineralized with EDTA plus 4.0 M guanidine. HCl. The proteins in the extracts were collected and, after a CaCl2 precipitation step, fractionated on Sephacryl S-200 in 6.0 M guanidine. HCl. The primary assay for activity was the incorporation of 35S-sulfate into proteoglycan in cultures of the fibroblast-like outgrowth cells from explants of neonatal rat muscle. Two Sephacryl S-200 fractions showed enhanced sulfate incorporating activity, but only one showed enhanced incorporation without a concomitant increase in cell number. In the presence of this fraction, the cell cultures produced a larger amount of a new small proteoglycan, as compared to controls, and a significant amount of a much larger proteoglycan. The active fraction had proteins in the Mr range from 8,000 to 15,000 as the major components. These data suggest that the fraction identified may contain the factors responsible for initiating the osteogenic response to dentin matrix upon its implantation in muscle in vivo.

Animals↗
PubMed1999

[The isolation and characterization of dentin phosphoprotein from human dentine].

OBJECTIVE: To establish the method of isolation and characterization of dentin phosphoprotein (DPP) from human dentine. METHODS: Dentin powder was placed in dialysis tube after demineralized to completion with 0.6 mol/L HCl, then isolated DPP through DEAE-Sepharose CL6B anion exchange chromatography. Its protein composition, organic phosphorus content, molecular weight and amino acid were analyzed. RESULTS: DPP contained high organic phosphorus, 23.8% of aspartic residue and 19.1% serine residue; their molecular weight were 141, 000, 124, 000, 108, 000 respectively. CONCLUSION: DPP can be extracted from human dentine with 0.6 mol/L HCl demineralization. and DEAE-Sepharose CL6B anion exchange chromatography. It is a group of proteins which have a high content of organic phosphorus and is found to be rich in serine and aspartic acid residues.

Amino Acids↗
PubMed2003

Dentin sialoprotein in bone and dentin sialophosphoprotein gene expressed by osteoblasts.

Dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) are expressed as a single mRNA transcript. This transcript codes for a large precursor protein termed dentin sialophosphoprotein (DSPP). DSP, DPP, and DSPP have been considered to be tooth-specific. Recently, we found out that the dspp gene was expressed in osteoblasts and bone. With Western immunoblots, we detected DSP in the Gdm/EDTA extracts of rat long bone, at a level of about 1/400 of that in dentin. Using reverse transcription polymerase chain reaction (RT-PCR) techniques with primers specific to the 5'DSP portion (termed DSP, 1432 bp), 3'DPP sequence (DPP, 2135 bp), and the region covering portions of both the DSP and DPP (DSPP, 3471 bp), we detected DSPP mRNA in MC3T3-E1 cells, ROS 17/2.8 osteoblast-like cells, and mouse calvaria. The results from PCR show that this gene is expressed at a much lower level in osteoblasts than in odontoblasts. The data indicate that DSPP is not a tooth-specific protein and that dramatically different regulatory mechanisms governing DSPP expression are involved in tooth and bone.

Animals↗
PubMedDate not supplied

The effect of dentin adhesive and cure mode on film thickness and microtensile bond strength to dentin in indirect restorations.

This study evaluated the influence of dentin adhesive application technique (pre-curing vs non precuring) on microtensile bond strength (microTBS) to dentin and adhesive layer thickness in indirect resin restorations. Seven proprietary dentin adhesives were tested, including one-step and multistep products. Experimental groups included adhesive pre-cure (PC) with a halogen light source and no pre-cure (NPC) prior to resin cement insertion. Thirty caries-free molars received an MO inlay preparation. Inlays made with Tetric Ceram resin composite were cemented using a dual-cured resin luting agent. Prior to inlay cementation, each tooth was treated with one dentin bonding agent, using pre-cure (PC) or no pre-cure (NPC). After storage in distilled water at 37 degrees C for 24 hours, the teeth were sectioned along their long axis to produce serial sticks for microtensile bond strength testing at 0.5 mm/minute. The results were subjected to statistical analysis by one-way and two-way analysis of variance (ANOVA) and Tukey's multiple comparison test (p < or = 0.05). For the film thickness evaluation, 10 additional teeth were restored and sectioned mesiodistally. The thickness of the adhesive layer was evaluated by SEM at 1000x magnification at the pre-selected locations. The microTBS varied from 11.7 +/- 4.5 MPa to 43.4 +/- 9.8 MPa. The effect of pre-curing the adhesive was material specific. No adhesive layer was visualized for the adhesives used without the pre-curing step. The thickness of the adhesive layer for the pre-cured groups varied according to the different areas analyzed.

Analysis of Variance↗
PubMed1986

[Pulp-dentin reactions after CO2 laser treatment of the dentin].

The use of a CO2 laser in the treatment of dentinal caries in vital teeth seemed to be an important therapeutical progress compared to traditional means of carious tissue removal with rotary mechanical instruments. Forty sound premolars from patients with a mean age of twelve years were prepared according to a standard method for biological controls and submitted to the action of a CO2 laser of 3 Watts, equipped with a convergent lens of a 38 mm focal distance. The pulpal reactions were observed on day 15, 30, 50 and 80. No clinical post-operative symptomatology was observed in all treated teeth. The pulpal reactions related to the thickness of residual dentine consisted in the presence of reversible inflammatory changes, in the absence of degenerative processes and in an important production of tertiary dentine. The structural modifications occurring on the dentinal walls in these experimental conditions seemed not to induce a barrier totally tight to bacterial penetration.

Bicuspid↗
PubMed1980

Noncollagenous proteins of dentin. A re-examination of proteins from rat incisor dentin utilizing techniques to avoid artifacts.

Noncollagenous proteins (NCPs) were obtained rrom rat dentin using several precautionary measures to prevent artifactual degradation and losses of the proteins. Prior to demineralization, rat incisor dentin was extracted with 4 M guanidine hydrochloride (GdmCl) containing enzyme inhibitors. The only major component extracted with GdmCl was a proteoglycan fraction. Most of the NCPs were extracted when the incisors were decalcified with an EDTA solution containing protease inhibitors. The EDTA extract contained four types of macromolecules: acidic glycoproteins, gamma-carboxyglutamic acid (Gla)-containing proteins, phosphoproteins, and proteoglycans. With two exceptions, the apparent molecular weights of these NCPs were greater than 50,000. Our observations contrast sharply with the results obtained by others for human dentin NCPs and suggest that artifactual degradation and losses of some NCPs occurred in these previous studies. The organic phosphate-containing fraction was biphasic when the EDTA extract was chromatographed on DEAE-cellulose. Rechromatography of this fraction by two different procedures separated the material into a complex glycoprotein-containing fraction and, a single rat incisor phosphoprotein peak (RIP). Thus, the earlier interpretation by others that the biphasic nature of the RIP-containing fraction represents two widely differing phosphoprotein species was premature. Highly purified RIP, prepared by passage through a sulfonated polystyrene column, contained no cysteine, valine, methionine, leucine, phenylalanine, or arginine, and the level of phosphoseryl residues was higher than for any previous report. When this preparation of phosphoprotein was dephosphorylated (dP-RIP) and rechromatographed on DEAE-cellulose, a partial separation into two fractions was observed. Automated Edman degradation of fraction dP-RIP suggested the presence of two NH2-terminal sequences: Asp-Asp-Asp-Asn and Asp-Asp-Pro-Asn. However, this material displayed a single protein band when applied to 7.5% sodium dodecyl sulfate polyacrylamide gel electrophoresis and stained with Coomassie brilliant blue. The apparent molecular weight of dP-RIP, compared to standard globular proteins, was about 72,000. The data suggest that rat dentin contains at least two major molecular species of RIP that are closely related in size and-structure. In addition, preliminary evidence suggested that other minor forms of related phosphoproteins may exist.

Amino Acid Sequence↗
PubMed1998

The rôle of a dentine-bonding agent in reducing cervical dentine sensitivity.

This double-blind split-mouth trial with 16 adult patients investigated the ability of a dentine bonding agent (DBA) to reduce cervical dentine sensitivity. Following stimulation of pairs of teeth by conventional tactile and air blast stimuli, together with controlled evaporative and cold fluid stimuli, sensitivity was recorded using tactile threshold, visual-analogue scale (VAS) and short-form McGill pain questionnaire (SFMPQ), prior to and 1 week following treatment with DBA. Prior to assessment, subjects recorded their perceived overall sensitivity using VAS and SFMPQ. Application of each stimulus was separated by 10 min. Sensitivity was recorded by a clinician blinded to the treatment status of each tooth. The control tooth was treated by applying DBA to coronal enamel. Dietary information was collected after the post-treatment assessment. There was a significant (p<0.05) improvement in tactile threshold and air flow and air blast VAS scores, together with reductions in sensitivity to evaporative stimuli when assessed by SFMPQ. Treatment response was not influenced by the subjects' age, gender, diet, use of fluoride-containing or silica-based toothpastes or fluoride mouthwashes, or a history of previous sensitivity treatment. It is concluded that topical application of DBA is an effective way to reduce cervical dentine sensitivity.

Adult↗
PubMed2006

Contraction stress in dentin adhesives bonded to dentin.

Adhesives cured under constrained conditions develop contraction stresses. We hypothesized that, with dentin as a bonding substrate, the stress would reach a maximum, followed by a continuous decline. Stress development was determined with a tensilometer for two total-etch systems and two systems with self-etching primers. The adhesives were placed in a thin layer between a glass plate and a flat dentin surface pretreated with phosphoric acid or self-etching primer. After an initial maximum shortly after light-curing, the stress decreased dramatically for the total-etch systems (70%) and, to a lesser extent, for the adhesives with self-etching primers (30%). The greater stress decrease for the total-etch systems was ascribed to water and/or solvents released into the adhesives from the fully opened dentinal tubules by the pulling/sucking action of the contraction stress. This happened less with the adhesives with self-etching primers, where the tubules remained mainly closed.

Analysis of Variance↗
PubMed1992

Dentin phosphoprotein in dentin development: implications in dentinogenesis imperfecta.

Dentin phosphoprotein (DPP, phosphophoryn) is the major non-collagenous protein component of the dentin extracellular matrix. This highly acidic phosphorylated protein is solely expressed by ectomesenchymal-derived odontoblast cells of the tooth organ. Previous biochemical studies have suggested the absence of this protein associated with the human genetic disease dentinogenesis imperfecta (DGI) Types I and II. However, due to the normal degradation of human DPP during dentin maturation, it has not been possible to establish if these reported differences were due to changes in DPP expression or secondary degradation rates in DGI affected versus normal teeth. Recently, we have taken both a molecular and biochemical approach to address this problem. Molecular studies have utilized genetic linkage studies performed on several multi-generation informative DGI kindreds. These studies have determined linkage between DGI Types II and III and two markers localized to the long arm of human chromosome 4 in the region 4q11-4q21. The strategy used in our study was to map the DPP gene locus to the long arm of human chromosome 4, in the same region as DGI, using a DPP oligonucleotide probe and somatic hybrid cell lines. The results indicate DPP is not localized to any region of human chromosome 4. Our data indicates that a mutation within the DPP gene locus is not associated with DGI Types II or III. This data is supported by the identification of human DPP (95 kDa) within the dentin extracellular matrix of molars isolated from an affected DGI type II patient using a mouse anti-DPP antibody. However, this does not exclude the possibility that enzymes associated with DPP post-translational modifications (ie. phosphorylation or degradation) might be responsible for this genetic disease.

Animals↗
PubMed1996

A pilot study of lactic acid as an enamel and dentin conditioner for dentin-bonding agent development.

The purpose of this pilot study was to determine how lactic acid solution at various concentrations and etching times affected prepared human enamel and dentin surfaces and to assess whether it could be used in place of phosphoric or maleic acid as an etchant. The occlusal surfaces of extracted molar teeth were ground wet with 600-grit silicon carbide paper and treated with various aqueous solutions of lactic acid. Random samples were prepared for observation by scanning electron microscopy. The rest were used to determine shear bond strength of bonded dental composite cylinders. The micrographs revealed that lactic acid dissolved the smear layer with various degrees of etching and demineralization. The degree of smear layer and matrix removal was proportional to the concentration of the acid and the length of application time. A 20% lactic acid concentration applied for 10 seconds produced a clearly etched surface with minimal demineralization. A 30% concentration not only removed the smear layer and enlarged the dentin tubule orifices but also appeared to affect the collagen matrix. The shear bond strength to enamel treated with 50% lactic acid (17.5 +/- 1.5 MPa) and All-Bond 2 etchant (18.9 +/- 1.3 MPa) were not significantly different (p > 0.05). However, mean dentin bond strengths for all groups of lactic acid etchant and All-Etch etchant (10% phosphoric acid) were statistically similar.

Acid Etching, Dental↗
PubMed1996

Dentin bond durability after three years using a dentin bonding agent with and without priming.

OBJECTIVES: This three-year study was conducted to evaluate the tensile bond strengths of a dual-cured bonding resin, with and without priming, to bovine dentin. METHODS: Superficial bovine dentin was conditioned with 37% phosphoric acid and left unprimed (control) or was primed with 5-NMSA. Clearfil Photobond (Kuraray Co., Japan) was placed and light-cured, a layer of Protect Liner (Kuraray Co.) was applied, cured, then covered with Photo Clearfil Bright (Kurary Co.) resin composite and cured. Bonds were stressed in tension to failure at 1 d, 1 mon, 3 mon, 6 mon, 1 y and 3 y after preparation. Ten specimens were made for each group. Results were analyzed using one-way ANOVA and Duncan's multiple range test. Visual and SEM observations determined mode of failure and were analyzed using the Mann-Whitney U-test. Separate 1 d and 3 y specimens were fractured across the bonded interface and observed using a Field Emission SEM. After observation, the photomicrographs were compared for visual qualitative changes between the two time periods. RESULTS: The control (non-primed) group showed only a small decrease in bond strengths over 3 y, but in the primed group, a significant decrease was observed (p < 0.05). The bond strength of the non-primed group (5.2 MPa) was less than the primed group (10.6 MPa) at 1 d (p < 0.01), but by 3 y, the bonds of both groups were similar, 4.3 MPa and 5.5 MPa, respectively. Fractography indicated that only adhesive failure occurred in the control group. Failure in the primed group was cohesive in dentin initially, but shifted to the base or top of the hybrid layer after 1 y. Field Emission SEM observations showed hybrid layer formation in the primed group, but minimal resin infiltration in the control group. SIGNIFICANCE: Initially greater bond strengths were obtained for the primed group compared to the unprimed group (p < 0.01). However, by 3 y, the bond strength had decreased markedly in the primed group (p < 0.01), being almost the same for both groups. It was concluded that priming may only be useful to achieve strong bonding in the short term. These results may have significant implications related to clinical longevity of restorations.

Analysis of Variance↗
PubMed1999

The ultrastructure of a compomer adhesive interface in enamel and dentin, and its marginal adaptation under dentinal fluid as compared to that of a composite.

OBJECTIVES: To visualise the ultrastructure of the interface of SCA compomer adhesive and of Optibond composite adhesive in enamel and dentin, and to relate the findings to the marginal adaptation of these two products in mixed class V restorations. METHODS: The ultrastructure was investigated using a scanning electron microscope (SEM) with and without prior argon ion etching, an environmental SEM, a field emission SEM, a confocal laser scanning microscope, and a transmission electron microscope. The marginal adaptation was quantified in mixed class V restorations by using the replica technique and a SEM under simulated dentinal fluid before and after simultaneous mechanical and thermal loading. RESULTS: The ultrastructure of the compomer adhesive interface differed from those of the composite. However, no significant difference was discerned as regards the percentage of "continuous margin" in the enamel marginal area before loading, and in the dentin area before and after loading (p < 0.05; unpaired t-test). Only after loading, the percentage of "continuous margin" in enamel was significantly (p < 0.05; unpaired t-test) better than that of the compomer. SIGNIFICANCE: The results indicated that the ultrastructure of the adhesive interface allowed no clear conclusions to be drawn as to the quality of marginal adaptation.

Compomers↗
PubMed2001

A novel rat dentin mRNA coding only for dentin sialoprotein.

Dentin sialoprotein (DSP) is a major glycoprotein present in the mineralized dentin matrix that is expressed mainly by young and mature odontoblasts. Mutations in the DSP coding regions are linked to Dentinogenesis imperfecta I and II. indicating the importance of DSP in tooth formation. Previous studies have identified multiple mRNA transcripts in dentin that code for both DSP and phosphophoryns (PPs). Using reverse transcriptase-polymerase chain reaction (RT-PCR) to characterize these mRNA transcripts, we have identified a cDNA that codes for DSP, but not PP. This cDNA codes for a protein with 324 amino acids, 303 amino acids being identical to the published rat DSP sequence. However, the subsequent 21 amino acids are unique to this cDNA. Based on the coding sequence, the core protein is predicted to have a pI=4.24, a net charge of -34, and to contain four potential N-glycosylation sites and six potential sites for phosphorylation by casein kinase. That the corresponding mRNA was present in day 5 molar tooth germs was confirmed using RNA protection assays. These data, therefore, identify a novel transcript in rat tooth germs that codes only for DSP (designated as DSPII).

Age Factors↗
PubMed2003

Characterization of porcine dentin sialoprotein (DSP) and dentin sialophosphoprotein (DSPP) cDNA clones.

Dentin sialophosphoprotein (DSPP) is a chimeric glycoprotein with dentin sialoprotein (DSP) on its N-terminus and dentin phosphoprotein (DPP) on its C-terminus. We have constructed and screened a unidirectional cDNA library derived from the pulp organ of developing pig teeth, and isolated cDNA clones encoding DSP-only, as well as two DSPP clones with alternative sequences in their 3' coding regions. The DSP-only transcript has an open reading frame of 386 codons, and is generated through the use of a polyadenylation signal within intron 4, immediately following the DSP coding region. the use of this polyadenylation signal deletes the DPP coding region and places a TGA translation termination signal as the fourth codon following the exon 4-encoded segment. The DSPP cDNAs contain open reading frames of 593 and 600 codons. Northern blots hybridized to radiolabeled DSP probes showed bands at 1.4, 2.5, 4.4, and 4.8 kb. Cloning and characterization of reverse transcriptase polymerase chain reaction products confirmed the existence of mRNA encoding pDSP386, pDSPP593, and pDSPP600in vivo, but also suggested that DNA sequence redundancies in the DSPP coding region make it prone to cloning artifacts.

Amino Acid Sequence↗