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PubMed1997

Automated image analysis applied to the odontoblast-predentine region in undemineralized sections of human permanent third molars.

A computerized histomorphometric analysis was made by Karnovsky-fixed, hydroxethylmethacrylate embedded and toluidine blue/pyronin-stained sections to determine: (1) the two-dimensional size of the coronal odontoblasts given by their cytoplasm:nucleus ratio; (2) the ratio between the number of coronal odontoblasts and dentinal tubules; and (3) the relation between odontoblast size and adjacent predentine. All conditions were measured in relation to three well-defined sectioning profiles of the dentinal tubules. The sections were randomly taken from 10 unerupted and erupted third-molar crowns. Sixty-three photomicrographs (x100), equally distributed among the three sectioning profiles, were scanned in a high-resolution scanner to produce images for the analysis. After initial user interaction for the description of training classes on one image, an automatic segmentation of the images with respect to odontoblast cell nuclei, cytoplasm and background was computed by statistical discriminant analysis. In longitudinal profiles of the dentinal tubules the cytoplasm:nucleus ratio in erupted teeth was 3.1 +/- 0.54, and the mean of the odontoblast cell:dentinal tubule ration was 1.19 +/- 0.20. Analysis of cytoplasm:nucleus ratio and the adjacent predentine in relation to the chosen sectioning profiles disclosed that there was less variation in the predentine measurements in the longitudinal sections. Thus, in future two-dimensional studies of the odontoblast-predentine region only longitudinal sectioning profiles should be analysed. The use of advanced image processing on undemineralized tooth sections provides a rational foundation for further work on the reactions of the odontoblasts to external injuries including dental caries.

Analysis of Variance↗
PubMed2000

Human odontoblast cell numbers after dental injury.

OBJECTIVES: The purpose of this study was to measure the changes in odontoblast cell numbers in response to cavity restoration variables and patient factors, and the effect these factors have on dental repair by tertiary dentinogenesis. The number of vital odontoblasts is a critical factor for pulpal repair following restorative surgery, and yet little information is available on these cell numbers. METHODS: Class V non-exposed cavities were prepared in the buccal surface of intact first or second premolar teeth of 27 patients, between 9 and 17 years of age. Following tooth extraction (28-163 days) the area of reactionary dentine and the area of the odontoblasts were measured histomorphometrically. RESULTS: Patient factors, as well as cavity preparation and restoration variables, had little effect on the numbers of odontoblasts per pulpal unit area. However, the age of the patient did appear to have an effect on the reactionary dentine secretory capacity of odontoblasts per unit area, and on the relative number of odontoblasts beneath cut dentinal tubules. CONCLUSIONS: Odontoblast cell numbers were maintained following the preparation of cavities cut into dentine with a 0.5mm residual dentine thickness. The repair capacity of the pulp-dentine complex would appear to be age dependent, this may explain differences in the success of various restorative treatments between patients.

Adolescent↗
PubMed2001

Differentiation of embryonic mesenchymal cells to odontoblast-like cells by overexpression of dentin matrix protein 1.

Cells of the craniofacial skeleton are derived from a common mesenchymal progenitor. The regulatory factors that control their differentiation into various cell lineages are unknown. To investigate the biological function of dentin matrix protein 1 (DMP1), an extracellular matrix gene involved in calcified tissue formation, stable transgenic cell lines and adenovirally infected cells overexpressing DMP1 were generated. The findings in this paper demonstrate that overexpression of DMP1 in pluripotent and mesenchyme-derived cells such as C3H10T1/2, MC3T3-E1, and RPC-C2A can induce these cells to differentiate and form functional odontoblast-like cells. Functional differentiation of odontoblasts requires unique sets of genes being turned on and off in a growth- and differentiation-specific manner. The genes studied include transcription factors like core binding factor 1 (Cbfa1), bone morphogenetic protein 2 (BMP2), and BMP4; early markers for extracellular matrix deposition like alkaline phosphatase (ALP), osteopontin, osteonectin, and osteocalcin; and late markers like DMP2 and dentin sialoprotein (DSP) that are expressed by terminally differentiated odontoblasts and are responsible for the formation of tissue-specific dentin matrix. However, this differentiation pathway was limited to mesenchyme-derived cells only. Other cell lines tested by the adenoviral expression system failed to express odontoblast-phenotypic specific genes. An in vitro mineralized nodule formation assay demonstrated that overexpressed cells could differentiate and form a mineralized matrix. Furthermore, we also demonstrate that phosphorylation of Cbfa1 (osteoblast-specific transcription factor) was not required for the expression of odontoblast-specific genes, indicating the involvement of other unidentified odontoblast-specific transcription factors or coactivators. Cell lines that differentiate into odontoblast-like cells are useful tools for studying the mechanism involved in the terminal differentiation process of these postmitotic cells.

3T3 Cells↗
PubMed1992

The carboxy-terminal extension of the collagen binding domain of fibronectin mediates interaction with a 165 kDa membrane protein involved in odontoblast differentiation.

Terminal differentiation of the odontoblast is characterized by an elongation and a polarization of the cell. The change in the cell shape and the reorganization of the cytoplasm involve the microfilament system. An immunological approach has previously implicated a transmembrane interaction between fibronectin and vinculin in the control of odontoblast differentiation. A 165 kDa protein localized on the cell-surface of odontoblasts mediated this interaction. In order to define the nature of the interaction of the 165 kDa protein with fibronectin, peptides were prepared by proteolytic cleavage of fibronectin with alpha-chymotrypsin. The results indicate that the 165 kDa protein interacted with a 62 kDa peptide located towards the amino-terminal extremity of fibronectin, but not with a 47 kDa related fragment. Both these 62 kDa and 47 kDa peptides included the collagen-binding domain and were retarded on a heparin-Ultrogel column. Microsequences demonstrated that the 62 kDa and 47 kDa fragments had the same amino-terminal extremity and that the larger fragment was extended in the carboxy-terminal direction. This carboxy-terminal extension of the collagen binding domain of fibronectin is implicated in the interaction of this molecule with the 165 kDa protein. On the other hand, odontoblasts differentiated normally when tooth germs were cultured in the presence of GRGDS synthetic peptide, suggesting that RGD-dependent integrins were not involved in odontoblast differentiation. Staining of dental mesenchymal cells in primary culture and of differentiated odontoblasts in situ with antibodies directed against the beta 1-subunit of integrins confirmed previous observations and showed that although beta 1 integrins are involved in the attachment of cultured dental cells, they are not implicated in the process of odontoblast differentiation.

Actin Cytoskeleton↗
PubMed1991

[Micromorphologic studies of the odontoblasts of sheep in different development and maturation stages].

The fine tissue structure of ovine odontoblasts was studied in various developmental and maturational stages. Odontoblasts differentiate from the peripherally-located mesenchymal cells of the dental papilla. On the basis of cytological parameters, it was possible to divide the odontoblasts into the following groups: pre-odontoblasts, juvenile (light) odontoblasts and mature (dark) odontoblasts. The three maturational stages of odontoblasts exhibit substantial differences with respect to their form and to the number and arrangement of their cytoplasmatic organelles. Structural differences in the three cell types appear to be closely correlated to the level of cellular activity.

Animals↗
PubMed1998

Immunocytochemical detection of apoptosis in human odontoblasts.

Pulpal chamber size decreases on ageing due to primary and secondary dentin deposition. This work was designed to find out the consequences of this pulp chamber reduction on odontoblast number and distribution. Twenty-one healthy human premolars were equally divided into three groups from 11-, 12.5- and 14-yr-old adolescents, respectively). The external and the internal perimeters of dentin were recorded on vestibulo-lingual sections, from buccal to lingual cemento-enamel junction using an image analysis system. Nuclei of the odontoblasts were recorded on 12 automatically selected fields. On nine erupted premolars (3 teeth from each 11-, 12.5- and 14-yr-old patients), apoptosis was detected by confocal microscopy using a modification of the original TUNEL method. Apoptotic cells were labeled in central pulp fibroblasts, perivascular endothelial cells, and in odontoblasts. When the pulp volume decreases due to primary dentin production, the decrease of the surface available for odontoblasts is compensated for by a multilayer distribution of cells. Secondary dentin deposition, associated with odontoblasts reorganization in a single layer, results in a hyperbolic decrease of the odontoblasts number. This decrease seems to result from a programmed cell death, which eliminates half of the odontoblasts over a 4-yr period.

Adolescent↗
PubMed1998

A quantitative light microscopic study of the odontoblast and subodontoblastic reactions to active and arrested enamel caries without cavitation.

This study describes cellular and microradiographic findings in thin undemineralized enamel-dentine sections from 36 enamel caries lesions from freshly extracted third molars. Lesions activity was determined by clinical examination and the estimated age of the lesion at extraction time. The cellular reactions to the enamel/dentine lesion complex were measured using computerized histomorphometry under the following conditions: (a) the cytoplasm:nucleus ratio of the odontoblast cell; (b) the odontoblast cell:dentinal tubule ratio, and (c) the adjacent predentine area (microm2). The first cellular reactions were observed beneath superficial enamel lesions before visible alterations in dentine mineralization. The cytoplasm:nucleus ratio of the odontoblast cells was markedly reduced, and only active lesions showed evidence of cellular proliferation into the cell-free zone. In more advanced active lesions the affected odontoblast cells had a significantly lower cytoplasm:nucleus ratio compared with the controls. Similar changes were not seen in arrested or slow-progressing lesions. Before onset of tertiary dentine formation there was a positive correlation between odontoblast cell size and predentine formation. Primary odontoblast cells were involved in early tertiary or reactionary dentine formation without odontoblast cell replacement. Reactionary dentine was only seen in active lesions, suggesting that reactions in the dentine/pulp complex are closely associated with the external environment.

Adult↗
PubMed2000

The expression of MMP-8 in human odontoblasts and dental pulp cells is down-regulated by TGF-beta1.

Recent findings show that matrix metalloproteinase-8 (MMP-8) is expressed, in addition to neutrophils, by human chondrocytes, cultured fibroblasts, and endothelial cells. We investigated the expression of MMP-8 in other human mesenchyme-derived cells, odontoblasts, and pulp tissue. Odontoblasts and pulp tissue were collected from extracted human teeth for MMP-8 mRNA analysis with reverse-transcription/polymerase chain-reaction (RT-PCR) and Southern blot. The expression, localization, and secretion of MMP-8 protein were studied with Western blot, immunohistochemistry, and immunofluorometric assay. The effect of TGF-beta1 (10 ng/mL) on the expression, secretion, and concentration of secreted MMP-8 was studied by odontoblast and pulp tissue culture methods (Tjäderhane et al., 1998a). RT-PCR demonstrated MMP-8 mRNA expression in native and cultured odontoblasts and pulp tissue and cultured pulp fibroblasts, with a 522-bp transcript comparable with that of bone marrow cells. The specificity of PCR was confirmed with Southern blot. Western blot with MMP-8-specific antibody detected 65- and 50-kDa proteins in native samples, representing latent and active forms of mesenchymal-type MMP-8, and in the conditioned odontoblast culture media, 50-kDa protein was observed. TGF-beta down-regulated the MMP-8 mRNA and concentration of secreted protein in both cultures. Immunohistochemical staining detected MMP-8 in odontoblasts. These findings indicate that mesenchyme-derived cells of the dentin-pulp complex express, synthesize, and activate MMP-8, which may, in concert with odontoblast-derived gelatinases, participate in organization of dentin organic matrix prior to mineralization.

Blotting, Southern↗
PubMed1996

An ultrastructural study of the relationship between sensory trigeminal nerves and odontoblasts in rat dentin/pulp as demonstrated by the anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP).

Because the ultrastructure of the trigeminal sensory nerves in dentin, especially in relation to odontoblasts, remains to be clarified, we investigated the relationship between the trigeminal sensory nerves and the odontoblast processes using the anterograde axonal transport technique by injecting wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into the rat trigeminal ganglion. Light microscopically, the nerves labeled with WGA-HRP were mainly concentrated at the pulpal horn, forming a nerve plexus at the subodontoblastic region and penetrating the predentin/dentin about 50 to 70 microns. Ultrastructurally, HRP reaction products were observed intra-axonally in the myelinated (A delta) and unmyelinated (C) axons in the subodontoblastic region. Most nerves lost the Schwann sheath and were naked in the predentin/dentin. The labeled varicosities were close to the odontoblast processes in the dentinal tubules. No synaptic structures could be detected between the varicosities and the odontoblasts, but a gap about 20 nm wide was found between them. One type of varicosity was a rich mitochondria-containing varicosity, while the other was a rich vesicle-containing (large dense core vesicles and small clear vesicles) one. The reaction products were also found in the extracellular spaces surrounding the axons. Sometimes the reaction products were seen in the coated pits or the endocytotic vesicles of the odontoblast processes. The present study demonstrated that nerve endings (varicosities) derived from the trigeminal ganglion were present in the dentinal tubules, and that WGA-HRP extracellularly extruded from the sensory nerves in the odontoblastic layer or predentin/dentin. These findings thus suggest that sensory nerves may have some (e.g., trophic) effect on either odontoblasts or the environment around the sensory nerves in the dentin/pulp.

Afferent Pathways↗
PubMed1997

The activin-binding protein follistatin is expressed in developing murine molar and induces odontoblast-like cell differentiation in vitro.

It has recently been shown that mice deficient in activin-beta A subunits and follistatin exhibit major defects in dentition. To increase understanding of the roles played by these molecules during tooth development, we determined the temporospatial expression of activin-beta A subunit and follistatin messenger RNA and their corresponding proteins in developing murine molars (between day E 14 and 2 days after birth). The effects of recombinant human activin A and its binding protein follistatin on odontoblast differentiation were also studied in cultures of dental papillae (DP) isolated from the mandibular first molars of E-17-day mice. In situ hybridization indicated that transcripts for activin-beta A subunit were abundant in pre-odontoblasts at the tips of forming cusps prior to odontoblast terminal differentiation, and transcripts for follistatin in overlying inner enamel epithelial cells (pre-ameloblasts). Pre-odontoblasts were also weakly immunoreactive in relation to activin-beta A subunit, pre-ameloblasts in relation to follistatin. When follistatin was added at different concentrations to a DP culture model (2-14 nmol/DP) together with heparin at constant concentration, differentiation of odontoblast-like cells was induced, as evidenced by polarization and deposition of extracellular matrix in vitro, to extents depending on the follistatin concentration. In contrast, the addition of activin A (2 nmol/DP) had no effect on the differentiation parameters studied. These findings suggest that the activin-follistatin system regulates odontoblast differentiation during tooth development. In particular, we suggest that binding of endogenous activin A by follistatin may allow odontoblast terminal differentiation to occur.

Activins↗
PubMed2003

Relative levels of mRNA encoding enamel proteins in enamel organ epithelia and odontoblasts.

Amelogenin, enamelin, sheathlin (ameloblastin/ amelin), enamelysin (MMP-20), and KLK4 (EMSP-1) are the major structural proteins and proteinases in developing tooth enamel. Recently, odontoblasts were reported to express amelogenin, the most abundant enamel protein. In this study, we hypothesized that odontoblasts express all enamel proteins and proteases, and we measured their relative mRNA levels in enamel organ epithelia and odontoblasts associated with porcine secretory- and maturation-stage enamel by RT-PCR, using a LightCycler instrument. The results showed that amelogenin mRNA in secretory-stage EOE is 320-fold higher than in odontoblasts beneath secretory-stage enamel, and over 20,000-fold higher than in odontoblasts under maturation-stage enamel. Similar results were obtained for enamelin and sheathlin. Enamelysin mRNA levels were equivalent in these two tissues, while KLK4 mRNA was higher in odontoblasts than in secretory-stage EOE. These results support the conclusion that odontoblasts are involved in the formation of the enamel layer adjacent to enamel-dentin junction.

Ameloblasts↗
PubMed1998

Distribution of ABH blood group epitopes on inner surface of dental hard tissue: serological, immunohistochemical and ultrastructural study on odontoblasts.

This study was designed to investigate localization of ABH antigens on the inner surface of human tooth hard tissues. The tooth samples, extracted therapeutically, were cut and dried at room temperature for a few weeks. Scanning electron microscopic observation disclosed that the inner surface was exclusively covered with the odontoblastic zone and virtually no blood vessels remained in the samples. Blood group activities of the tooth fragments, which were detected with absorption-elution test, were markedly decreased when the odontoblastic zone was scraped off. To visualize the activity, the avidin-biotin-peroxidase complex immunostaining was performed on the odontoblasts of fresh teeth followed by embedding. Decalcification process was omitted to preserve the antigenicity. Group specific colorization was successfully developed on the cell surface of the odontoblasts. Immunoreactivity of the cell membrane of the odontoblast including the odontoblastic process was also confirmed by immunotransmission microscopic observation. On the other hand, localization of epitopes on intrinsic dentine without cell components could not be visualized. The results of these experiments indicate that the odontoblasts are one of potent sources of blood group antigenicity for blood grouping of the human teeth.

ABO Blood-Group System↗
PubMed2002

Ca-binding domains in the odontoblast layer of rat molars and incisors under normal and pathological conditions.

We recently reported the presence of high concentrations of a Ca-binding matrix in the circumpulpal dentin of rat incisors which had been prevented from mineralization by a systemic administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP), a type of bisphosphonates, thus suggesting the role of the putative Ca-binding matrix in the appositional mineralization of circumpulpal dentin (TAKANO et al., 1998, 2000; OHMA et al., 2000). In this study, we examined the distribution of Ca-binding domains in the pulp tissue of normal rat teeth and its changes under the influence of HEBP, in order to identify and clarify the role of the Ca-binding matrix in the physiological process of dentin mineralization. Observation of the normal rat tooth pulp showed occasional, tiny extracellular deposits of Ca-enriched material in the odontoblast layer, associated primarily with pericapillary regions. Such deposits were immunopositive for dentin sialoprotein (DSP), displayed high levels of X-ray peaks for calcium and phosphorus, and showed a drastic increase in amount by daily injections of HEBP. A brief vascular perfusion of high Ca-containing solution in normal animals caused the extensive deposition of Ca-P complexes along the basolateral membranes of odontoblasts but not in the other regions of the pulp tissue. These data suggest the existence of DSP-enriched extracellular Ca-binding domains in the odontoblast layer and also indicate a novel Ca-binding property of the basolateral membranes of odontoblasts. Since DSP is primarily synthesized as dentin sialophosphoprotein (DSPP) and later cleaved into dentin phosphophoryn (DPP) and DSP in odontoblasts, and since DSP has no notable affinity for Ca, the sites of DSP-immunopositive Ca-P deposits in the odontoblast layer may also contain DPP, a highly phosphorylated acidic protein having a strong binding property for calcium. Characteristic Ca-binding properties seen in the odontoblast layer appear to be related to the regulation of the appositional mineralization of circumpulpal dentin.

Animals↗
PubMed2005

The odontoblast as a sensory receptor cell? The expression of TRPV1 (VR-1) channels.

Previous reports have shown the expression of several mechanosensitive ionic channels on the plasma membrane in odontoblasts, which are the cells responsible for dentin formation. The membrane characteristics of odontoblasts imply that they could play critical roles in the mechano-transduction of fluid displacement within dentinal tubules into the electrical cell signals, to carry dentin sensation to the central nervous system. However, the direct ionic mechanism underlying such a dentin nociceptive function remains unclear. In the present study, we investigated the expression of the transient receptor potential vanilloid subfamily member 1 (TRPV1) channel--which essentially contributes to the detection of pain sensation--in rat odontoblasts by immunohistochemical and nystatin perforated patch-clamp techniques. Immunohistochemical observation showed the localization of TRPV1-immunoreactions on the distal regions of odontoblast membranes. In the patch-clamp experiments, we observed capsaicin-induced inward currents that were inhibited by capsazepine, a TRPV1 channel antagonist. Our results indicate a significant expression of TRPV1 channels in odontoblasts, suggesting that odontoblasts may directly respond to noxious stimuli such as a thermal-heat stimulus, and point to the necessity for a reconsideration of the cellular mechanisms of dentin sensation based on the transmembrane ionic signals in odontoblasts.

Animals↗
PubMed1995

Collagen fibrils in the odontoblast layer in the teeth of the rat and the house shrew, Suncus murinus, by scanning electron microscopy using a maceration method.

It is not well known whether there are gaps in the tight junctions between odontoblasts and whether the fluid flows from the pulp to the predentin through these gaps. The collagen fibrils in the odontoblast layer were investigated using a maceration method in order to show the existence of the gaps between tight junctions of the odontoblasts. The mandibles containing teeth of the rat and the house shrew were digested by NaOH maceration and revealed the architecture of the collagen fibrils under scanning electron microscopy. The collagen fibrils went from the pulp, through the odontoblast layer, and were woven into the collagen network of the predentin in all teeth used in this study. Thick bundles of collagen were seen in the odontoblast layer at the pulp horn of the rat molars. Because there are many collagen fibrils in the odontoblast layer, it is considered that the tight junction of the odontoblast is of the discontinuous type.

Alveolar Process↗
PubMed2006

Lipoteichoic acid increases TLR and functional chemokine expression while reducing dentin formation in in vitro differentiated human odontoblasts.

Gram-positive bacteria entering the dentinal tissue during the carious process are suspected to influence the immune response in human dental pulp. Odontoblasts situated at the pulp/dentin interface are the first cells encountered by these bacteria and therefore could play a crucial role in this response. In the present study, we found that in vitro-differentiated odontoblasts constitutively expressed the pattern recognition receptor TLR1-6 and 9 genes but not TLR7, 8, and 10. Furthermore, lipoteichoic acid (LTA), a wall component of Gram-positive bacteria, triggered the activation of the odontoblasts. LTA up-regulated the expression of its own receptor TLR2, as well as the production of several chemokines. In particular, an increased amount of CCL2 and CXCL10 was detected in supernatants from LTA-stimulated odontoblasts, and those supernatants augmented the migration of immature dendritic cells in vitro compared with controls. Clinical relevance of these observations came from immunohistochemical analysis showing that CCL2 was expressed in vivo by odontoblasts and blood vessels present under active carious lesions but not in healthy dental pulps. In contrast with this inflammatory response, gene expression of major dentin matrix components (type I collagen, dentin sialophosphoprotein) and TGF-beta1 was sharply down-regulated in odontoblasts by LTA. Taken together, these data suggest that odontoblasts activated through TLR2 by Gram-positive bacteria LTA are able to initiate an innate immune response by secreting chemokines that recruit immature dendritic cells while down-regulating their specialized functions of dentin matrix synthesis and mineralization.

Cell Differentiation↗
PubMed1992

Changes in expression of alpha 1 type 1 collagen and osteocalcin mRNA in osteoblasts and odontoblasts at different stages of maturity as shown by in situ hybridization.

We investigated whether the expressed phenotype of osteoblasts and odontoblasts is changing with increasing maturity of the cells. Thus we determined, using in situ hybridization techniques, whether the expression of mRNA's for osteocalcin and the alpha 1 type 1 collagen chain was different in newly developed and more mature cuboidal osteoblasts of the primary and secondary spongiosa of radii of 8 day old rats, in mature cuboidal and older flat osteoblasts in the metatarsals of pig embryos, and in apical and coronal odontoblasts of the developing unerupted molars of pig embryos. The results indicate that newly differentiated osteoblasts in the primary spongiosa of the 8 day rat radius contained approximately the same amount of type 1 collagen message as more mature osteoblasts in the secondary spongiosa. Osteocalcin mRNA, on the other hand, was undetectable in the newly differentiated osteoblasts but clearly detectable in the mature osteoblasts of the secondary spongiosa. When we compared expression of osteocalcin and collagen type 1 mRNA in mature cuboidal and older flat osteoblasts, we found that the amount of osteocalcin mRNA relative to collagen type 1 mRNA was higher in flat osteoblasts than in cuboidal osteoblasts. In odontoblasts, however, the steady state level of collagen type 1 mRNA was higher in the older coronal odontoblasts, and the level of osteocalcin message lower, when compared to the younger apical odontoblasts. The results indicate that relative levels of osteocalcin and collagen mRNA in osteoblasts and odontoblasts vary depending on the stage in their secretory lifetime. This heterogeneity of the osteoblast and odontoblast population suggests that the composition of the matrix produced by these cells also differs.

Animals↗
PubMed2006

Early odontoblastic layer response to cavity preparation and acid etching in rats.

The aim of this study was to establish the early odontoblastic layer response and quantitatively to estimate the number of odontoblasts after cavity preparation with and without acid etching. Half of 56 cavities prepared on rats' first upper molars were acid etched. Qualitative and morphometric analyses were made on histological and ultrathin sections 5 min, 6 h, 24 h and 72 h post-operatively. Under the etched cavity, a greater disarrangement of odontoblasts was found, modifications in nuclear shape and condensed chromatin 5 min. post-operatively. An additional reduction of odontoblast number was detected and an increase of aspirated cell number 5 min, 6 h and 24 h post-operatively, pronounced hyperaemia 6, 24 and 72 hours post-operatively and increased odontoblast number 72 hours post-operatively, compared to unetched cavities. In conclusion, injury to the odontoblastic layer was greater, but numerical renewal of the odontoblastic layer began earlier in etched cavities compared to unetched cavities.

Acids↗