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PubMed1976

The growth of calcium phosphates on natural enamel.

The kinetics of growth of calcium phosphate on seed materials prepared from human tooth enamel has been studied at 25 degrees C and pH 7.40 in stable supersaturated solutions of calcium phosphate. The grown material was characterized chemically, by specific surface area (SSA) measurements and by subsequent dissolution experiments. The marked increase in SSA in the early stages of the precipitation reaction parallel the results obtained with synthetic hydroxyapatite seed crystals and the results of the dissolution experiments indicate a chemical composition close to that of octacalcium phosphate for this intermediate phase. At low supersaturation it is possible to avoid the formation of the precursor phase.

Calcium Phosphates↗
PubMed2006

Synthesis of a potentially bioactive, hydroxyapatite-nucleating molecule.

A human phosphophoryn (PP) cDNA was previously cloned from immature root apex total RNA in our laboratory. This cDNA comprises 2,364 bp, encoding 788 amino acids. More than 80% of the sequences are arranged as (DSS)(n) (n = 1-16), DS, and NSS motifs. We hypothesize that the capability of PP to bind Ca(2+) and nucleate hydroxyapatite may depend on these repeated sequences. Two polypeptides were synthesized based on the human PP cDNA sequence to test the hypothesis. One polypeptide has the amino acid sequence DDPNSSDESNGNDD (synthetic polypeptide 1, SP1), which is from the N-terminal end of PP; the other polypeptide, DSKSDSSKSESDSS (synthetic polypeptide 2, SP2), is the PP repeated sequence motif. Phosphorylation of the polypeptides was accomplished by reacting them with adenosine triphosphate and casein kinases I and II. The ability of these molecules to cause mineralization was tested in a steady-state agarose gel system. The results show that phosphorylated SP2 (P-SP2) precipitated approximately 60% of the total Ca + PO(4) precipitated by PP. P-SP1 precipitated about 23% of that precipitated by PP and was similar to the amount precipitated in the control gel, that is, without added peptides. Transmission electron microscopy and X-ray diffraction analysis showed that the precipitate formed in the P-SP2-containing gel was hydroxyapatite. The capability of P-SP2 to nucleate Ca + PO(4) and precipitate hydroxyapatite is a result of the repeated sequence motif, which contains a high percentage of phosphorylated serine. This molecule could be used in the repair and regeneration of dental tissue.

Adenosine Triphosphate↗
PubMed2001

Qualitative and quantitative assessment of intratubular dentin formation in human natural carious lesions.

It was the aim of this study to investigate the scanning electron microscopy (SEM) features and the element content of calcium (Ca) phosphorus (P), magnesium (Mg), oxygen (O), and carbon (C) of sound dentin, demineralized dentin, secondary dentin, intratubular and peritubular de novo dentin formation due to caries progression and to compare the element content with chemically pure hydroxyapatite. Eighteen extracted teeth with deep dentin carious lesions were embedded in Technovit 9100 (Kulzer), and serial sections of 80 microm thickness were made. These sections were then investigated with polarized light microscopy to identify the lesions. Two sections of each lesion were then coated with carbon and studied with a scanning electron microscope. Of the 18 teeth, 8 showed intratubular dentin formation. The element content was measured using energy dispersive X-ray analysis (EDX). About 75% of all involved dentin tubules showed intratubular de novo dentin formation. The Ca/P ratio in sound dentin, demineralized dentin, peritubular dentin, and secondary dentin was within the range of hydroxyapatite, whereas in intratubular dentin the Ca/P ratio was different than that of hydroxyapatite. The element content for Ca was statistically highly significantly different (P < 0.01) among sound dentin/intratubular dentin, sound dentin/peritubular dentin, and sound dentin/ secondary dentin, but not between sound dentin/ demineralized dentin and sound dentin/hydroxyapatite. For the other measured elements varying statistical differences were found. Our results indicate that intratubular dentin does not occlude the dentin tubules completely and mineralizes different than that of sound dentin and may therefore not be true hydroxyapatite.

Dental Caries↗
PubMed2004

Forensic age estimation in living subjects: the ethnic factor in wisdom tooth mineralization.

Radiological assessment of the mineralization stage of third molars is a major criterion for age estimation of living people involved in criminal proceedings. To date insufficient knowledge has been obtained about how the ethnic origin can influence tooth mineralization. A comparative study of wisdom tooth mineralization was carried out on three population samples: one German, one Japanese and one South African. To this end, 3,652 conventional orthopantomograms were evaluated on the basis of Demirjian's stages. The Japanese subjects were on average 1-2 years older than their German counterparts upon reaching stages D-F, whereas the South African subjects were on average 1-2 years younger than the Germans when displaying stages D-G. To enhance the accuracy of forensic age estimates based on wisdom tooth mineralization we recommend the use of population-specific standards.

Adolescent↗
PubMed2004

Validation of common classification systems for assessing the mineralization of third molars.

One major criterion for dental age estimation is the evaluation of third molar mineralization. There are various methods for evaluating tooth mineralization based on classification by stages. The aim of the present work is to assess the validity of the common classification systems. To this end, we analyzed 420 conventional orthopantomograms of German females aged 12-25 years old. The mineralization status of tooth 38 was determined using the stages defined by Gleiser and Hunt, Demirjian et al., Gustafson and Koch, Harris and Nortje and Kullman et al., respectively. Of the methods tested, the most accurate results were obtained with Demirjian et al.'s classification system, which performed best not only for observer agreement but also for the correlation between estimated and true age. It is argued that this is due to the fact that Demirjian et al.'s classification is based on a sufficient number of stages which are defined independently of speculative estimations of length. This leads to the conclusion that the method devised by Demirjian et al. should be used for evaluating the mineralization of third molars for purposes of forensic age determination.

Adolescent↗
PubMed2002

An immunohistochemical study on hard tissue formation in a subcutaneously transplanted rat molar.

While dental pulp undergoes calcification following tooth replantation or transplantation, we actually know little about these mechanisms. We therefore conducted histological and immunohistochemical evaluations of mineralized tissue that formed in the pulp of rat maxillary molar transplanted into abdominal subcutaneous tissue. One, 2, 3, and 4 weeks post-transplantation, the teeth were investigated immunohistochemically using antibodies to osteocalcin (OCN), osteopontin (OPN), bone sialoprotein (BSP), dentin sialoprotein (DSP), and tissue non-specific alkaline phosphatase (TNAP). In the 1st week after transplantation, cell-rich hard tissue was formed at the root apex. At 2 weeks, formations of hard tissue, with few cells in the root canals and bone-like tissue in the coronal pulp chamber, were noted. After 3 and 4 weeks, the amounts of these hard tissues were increased. The immunolocalization of OCN, OPN, and BSP was seen strongly in coronal and apical hard tissues, but weakly in the root hard tissue. Conversely, DSP localized in the root hard tissue, but not in other newly formed hard tissues. At 1 week, TNAP localized along the periphery of the apical hard tissue and the lower surfaces of root predentin. These results demonstrate that the newly formed hard tissues in the pulp cavity of subcutaneously transplanted molars could be classified into three types, suggesting that these might be formed by type-specific cells.

Animals↗
PubMed2006

Expression of HMGB1 during tooth development.

High mobility group box 1 (HMGB1) is a nuclear and cytosolic protein that can act as a transcription factor, a growth factor, or a cytokine. To elucidate a possible role for HMGB1 in tooth development, we have studied the expression of HMGB1 and its receptor RAGE (receptor for advanced glycation end-products) during the late fetal and early postnatal period of rat by using light- and electron-microscopic immunohistochemistry. Low HMGB1 protein expression was observed during fetal and newborn stages of tooth development. However, from postnatal day 5 (P5) onward, a marked increase occurred in the levels of the protein in most dental cell types. Expression was particularly high in ameloblasts and odontoblasts at regions of ongoing mineralization. Although most HMGB1 immunoreactivity was confined to cell nuclei, it was also present in odontoblast cytoplasm. At P5, ameloblasts and odontoblasts also showed RAGE immunoreactivity, and reverse transcription-polymerase chain reaction demonstrated both HMGB1 and RAGE mRNA in human dental pulp cells in vitro. Immunoblots performed on extracts from bovine dentin demonstrated a principal band at approximately 27 kDa, indicating that HMGB1 participates in tooth mineralization. The expression of both ligand and receptor suggests an autocrine/paracrine HMGB1 signalling axis in odontoblasts.

Adult↗
PubMed1997

Quantitative electron-spectroscopic diffraction (ESD) and electron-spectroscopic imaging (ESI) analyses of dentine mineralisation in rat incisors.

Primary crystal formations in all hard tissues are, according to our investigations, Ca-phosphate chains composed of nanometer sized particles (dots) which develop along the matrix macromolecules. In circumpulpal dentine the centre-to-centre distances between the dots inside the chains reflect the distances between the crystal nucleating sites ("active sites") along the collagen matrix macromolecule. The centre-to-centre distances at the surface of the mineralised collagen fibrils probably reflect the distances between nucleating sites of noncollagenous proteins attached to collagen. These needle-like chains of dots coalesce in lateral directions to form ribbon-like crystallites. The morphological results are supported by correlated small area diffraction studies in the same regions of dentine. We have found that the first appearing Bragg-reflection has a lattice spacing value of 0.388 nm, which corresponds to the (111) apatite value. For the earliest crystal formations the intensity of the (002) reflection is higher than that of the (300)-reflection. A maximum of the net-signal-intensity ratio of the (002) to (300) Bragg-reflection appears at the mineralisation front. This peak repeats with decreasing height 3 to 5 times with a distance range of about 8-16 microm through the whole dentine zone, which corresponds to the distances of the incremental lines, called "von Ebner lines".

Animals↗
PubMed1975

Orthodontic positioner used for home fluoride treatments.

It has been well documented that the more time the enamel surface is exposed to fluoride, the higher will be the caries protection. An extremely good method of greatly increasing caries resistance is by daily or weekly home fluoride treatments. This procedure is usually limited to special cases of rampant caries, patients with hemophilia, and handicapped patients in whom caries control is vital. It is not used more widely because of the added costs of impressions, tray fabrication, and professional. If the patient already has a vehicle for applying fluoride, such as a positioner or mouth guard, it is a simple matter to prescribe or dispense fluoride gel to be used when these appliances are being worn. This is expecially true for orthodontic postioners. When bands are removed, a slight space usually exists interproximally. This space greatly facilitates fluoride contact with the proximal surfaces. Fluoride will tend to recalcify decalcified areas of enamel in addition to providing added caries protection for the patient. If positioners are not used after band removal, home fluoride trays or rinses can also be effective. Since many orthodontic patients wear a positioner when bands are removed, the orthodontist can provide his patients with the benefits of topical fluoride by prescribing fluoride gel and explaining how to use it along with his positioner.

Dental Caries↗
PubMed1981

In vitro studies on susceptibility of enamel to caries attack after orthodontic bonding procedures.

Oral hygiene plays an important role in the prevention of caries. Therefore, when one is investigating the possible effects of acid etching on caries susceptibility, oral hygiene aspects and the supplementation of fluoride have to be considered. The objective of this investigation was to study the caries susceptibility of etched enamel surfaces in vitro. To simulate the in vivo situation, much attention was given to the influence of remineralization of saliva and fluorides. It was shown that etching and subsequently fluoridating and remineralization increases resistance of enamel against a caries attack.

Acid Etching, Dental↗
PubMed1981

Rapid maxillary expansion and external root resorption in man: a scanning electron microscope study.

The effects of rapid maxillary expansion on the external root structure of thirteen appliance-attached and five unattached maxillary first premolars from nine patients have been investigated with the scanning electron microscope (SEM). Topographic features of cementum and dentine resorption, as well as initial and subsequent remineralization changes, are described in detail. All anchor premolars exhibited root resorption, which was mostly confined to the buccal surface. Generally, the longer an anchor tooth remained in fixed retention, the more extensive the buccal root resorption. In contrast, the unattached maxillary first premolars and the opposing mandibular first premolars showed no evidence of resorption. Active resorption was the dominant process in anchor premolars extracted almost immediately after rapid expansion. Subsequently, repair became the predominant process, but continuing resorption was apparent even after 9 months of retention. Repair of root defects occurred by the deposition of cellular cementum which revealed little evidence of principal periodontal fiber reattachment within the advancing mineral front. The resorption pattern identified in the scanning electron microscope was not detected by in vivo radiographic examination. The significance of the findings is discussed.

Activator Appliances↗