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PubMed1994

Chemically conditioned dentin: a comparison of conventional and environmental scanning electron microscopy findings.

OBJECTIVES: The purpose of this study was to compare the structure of acid-conditioned dentin in its wet and dry state. METHODS: Using conventional and environmental scanning electron microscopy, conditioned dentin was examined in a wet, air-dried and critical point-dried state. Six different treatments were used including citric, maleic, nitric, oxalic and phosphoric acids in their commercial formulations and applied in accordance with manufacturer's instructions. RESULTS: Loss of moisture from acid-conditioned dentin through simple air drying and drying under controlled conditions of environmental scanning microscopy resulted in morphological alteration of the fibrous, collagenous structure. Critical point drying preserved the fibrous integrity of the outer mineral-depleted zone. This observation was true for all the acids used. SIGNIFICANCE: While the ultrastructure of dentinal collagen may be chemically stabilized or relatively unaltered by acid conditioning, it is nonetheless subject to morphological degradation and collapse during water loss. Only critical point drying can control the interfacial stress accompanying water transport and loss at the fiber boundary. Confirming previous observations, this study supports the concept of maintaining the moist state of dentin and the morphological integrity of the collagen so as to facilitate optimal resin infiltration in the bonding procedure.

Acid Etching, Dental↗
PubMed1989

In vitro cytotoxicity of three dentine bonding agents.

While several studies have been reported on the physical testing of dentine bonding agents, very few studies have been involved with their biological evaluation. This report describes a new in vitro method for assessing the cytotoxicity of these materials through dentine simulating their clinical use. An experimental bonding agent, now marketed as Tripton by ICI Dental, Scotchbond 2 and GLUMA were exposed to BHK-fibroblasts through 100 and 500 microns slices. All materials were significantly cytotoxic compared with controls through both thicknesses of slice. The ICI Dental experimental material was the least toxic through 100 microns slices (68.8 per cent of controls) followed by Scotchbond 2 (54.2 per cent) with GLUMA the most cytotoxic (26.9 per cent). However, with 500 microns slices values for the ICI Dental experimental material and GLUMA were similar (70.8 and 66.6 per cent respectively), with Scotchbond 2 exhibiting greatest toxicity (52.6 per cent). The results indicate that these materials are considerably more cytotoxic than most restorative materials which have been tested using a similar system. It is anticipated that all materials, in particular Scotchbond 2, could cause severe reactions in deep cavities in vivo in the absence of an adequate lining.

Aldehydes↗
PubMed1994

Report on the Annual Conference of the British Association of Teachers of Conservative Dentistry.

The Annual Conference of the British Association of Teachers of Conservative Dentistry (BATCD) was held in Sheffield on 16 and 17 September 1993. The main programme addressed educational issues in three areas: the undergraduate/vocational-trainee interface, the teaching of implants in the undergraduate curriculum, and the changing role of dental instructors in restorative dentistry. The programme also included a number of research papers and poster demonstrations, which were submitted for the Association's new QED/Maillefer prizes in Restorative Dentistry. This paper presents reports of the four principal lectures, and abstracts of the research papers and poster demonstrations, with details of the prize winners.

Curriculum↗
PubMed2005

Outward fluid flow reduces inward diffusion of bacterial lipopolysaccharide across intact and demineralised dentine.

OBJECTIVE: To examine the ability of outward fluid flow (OF) on resisting the inward diffusion of bacterial lipopolysaccharide (LPS) across the demineralised dentine (DD) in comparison with that across the intact dentine (ID). DESIGN: Twenty ID discs were prepared from freshly extracted human third molars. After etching both dentine surfaces, hydraulic conductance (L(p)) of the dentine was measured. Ten dentine discs were then completely demineralised using 10% EDTA, and L(p) was re-measured. The diffusion of LPS through ID and DD was measured against the OF and compared to the non-outward flow (NF) (n = 5 for each group) at 0, 1, 4 and 8h. Longitudinal sections of ID and DD surfaces were observed under a scanning electron microscope (SEM). RESULTS: The L(p) of DD was significantly higher than that of ID (independent t-test, p < 0.001). The application of OF and demineralisation significantly affected LPS diffusion (two-way ANOVA, p < 0.05). In addition, the effect of OF depended on dentine demineralisation. SEM images of ID showed intact dentinal tubules, whereas those of DD showed expanded collagen fibres and enlarged dentinal tubules. CONCLUSIONS: The inward diffusion of LPS across DD differed from that of ID and the OF affected the inward diffusion of LPS. In the presence of the OF, the inward diffusion of LPS was reduced to near zero in both ID and DD. Nevertheless, when compared to that in the ID group, the OF produced the slightly greater effect to resist the inward LPS diffusion in the DD group.

Adolescent↗
PubMed2006

Piezoelectric properties of human dentin and some influencing factors.

OBJECTIVES: The present study focused on the piezoelectricity of human dentin. The effects of moisture content and orientation of tubules were investigated. METHODS: Fresh human dentin was cut with two surfaces generally parallel to the occlusal surface. The potentials generated by specimens were detected, as the compression loads were respectively parallel and vertical to the tubules. Moreover, specimens were dried and rehydrated; piezoelectric coefficients d(33) of dentin with different moisture content were measured horizontally to, and vertically to, the tubules. RESULTS: The results showed that piezoelectricity of dentin increased with increasing moisture content. Furthermore, greater piezoelectricity was detected parallel to the tubules than vertical to the tubules. SIGNIFICANCES: This study indicated that the piezoelectric properties of dentin were significantly affected by both humidity and orientation of the tubules. Both structural and free water in dentin is attributed to its piezoelectric properties.

Analysis of Variance↗
PubMed2006

Ultrastructure of smear layer-covered intraradicular dentin after irrigation with BioPure MTAD.

The structure of mechanically instrumented intraradicular dentin after irrigation with NaOCl as the initial rinse and BioPure MTAD as the final rinse were examined from the coronal, middle, and apical parts of root canal walls using transmission electron microscopy. Sterile distilled water and EDTA as final rinses were employed as the respective positive and negative controls under the same experimental conditions. There were 2 to 5 mum thick smear layers produced on mechanically instrumented root canal walls that were completely removed by EDTA and BioPure MTAD under agitation. Both irrigants created a zone of demineralized collagen matrices in eroded dentin and around the dentinal tubules, with the mildly acidic BioPure MTAD being more aggressive than EDTA. These demineralized dentin zones create the opportunity for dentin hybridization by infiltration of hydrophilic adhesives/sealers. However, the potential consequences of compaction of hydrophobic sealers against air-dried, collapsed collagen matrices, and hydrolytic degradation of incompletely infiltrated matrices remain unresolved.

Bicuspid↗
PubMed2006

Ultrastructure of intraradicular dentin after irrigation with BioPure MTAD. II. The consequence of obturation with an epoxy resin-based sealer.

In addition to an initial report on the creation of thick demineralized collagen matrices in root dentin that were irrigated with BioPure MTAD or EDTA as final rinses for 5 minutes, this study examined the effect of a 2-minute irrigation time of these final irrigants on the extent of demineralization of intact intraradicular dentin and on interfacial nanoleakage after obturation with AH Plus and gutta-percha using warm vertical compaction. Transmission electron microscopy confirmed that the reduction in irrigation time did not compromise the smear layer removing capacity of these two irrigants when 1.3% NaOCl was employed as the initial rinse. BioPure MTAD created 5 to 6 microm thick demineralized dentin matrices, while 17% EDTA produced 1 to 2 microm thick matrices that were suboptimally infiltrated by the epoxy resin-based sealer, as manifested by the occurrence of silver tracer deposits within the hybrid layers.

Chelating Agents↗
PubMed2004

Lactic acid root canal irrigation for dowel and core treatment: a pilot study.

STATEMENT OF PROBLEM: Various solutions used to irrigate root canals and remove the smear layer prior to obturation of a root canal affect surface topography and may influence the sealing ability of endodontic therapy, retention of endodontic dowels, and restoration survival. PURPOSE: This study microscopically evaluated the effects of varying dilutions of lactic acid on the removal of the smear layer created by hand instrumentation in the coronal, middle, and apical thirds of root canals. Lactic acid solution was compared with other solutions deemed to be suitable root canal irrigants. MATERIAL AND METHODS: Thirty-five extracted human single-rooted teeth were manually shaped with files (K-flex) using the step-back technique. ISO size 50 files were used as master apical files. The teeth were equally divided into 7 test groups according to the canal irrigant used. While the teeth were cleaned and shaped, the root canals were irrigated with 3 mL of 1 of the following irrigants between each file size and as a final flush: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and 5% sodium hypochlorite, 15% ethylenediaminotetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. Specimens were critical-point dried and freeze-fractured for scanning electron microscope analysis at 3 sites (cervical, middle, and apical). RESULTS: Scanning electron micrographs showed no differences between the cervical, middle, and apical levels of the specimens tested with any of the irrigants used. Also, no difference was found within individual groups. The surface of the control specimens had a smear layer that contained smear plug material. Hydrogen peroxide and sodium hypochlorite used separately and in combination consistently produced surfaces with a smear layer. Lactic acid solutions and EDTA, however, removed the dentinal smear layer but left remnants of smear plugs in the dentinal tubules. CONCLUSIONS: Within the limitations of this study, differences related to the type of irrigant used were found in the characteristics of the pulpal dentin surface. Although lactic acid effectively cleaned and smoothed the dentin walls of root canals of endodontically prepared teeth, further study is needed before this procedure can be recommended for routine clinical use.

Chelating Agents↗
PubMed2005

Investigation of pH at different dentinal sites after placement of calcium hydroxide dressing by two methods.

OBJECTIVE: The dentin pH at different sites following placement of calcium hydroxide paste using 2 different methods was evaluated. STUDY DESIGN: One hundred twenty Extracted teeth were instrumented and randomly divided into 6 different groups. Then they were dressed with calcium hydroxide by 2 different methods using paper points or Lentulo spiral, according to their respective groups, and stored. After the experimental period of time, half of the samples were cut transversally into slices and the other half split longitudinally and rinsed with distilled water. The dentin pH of cervical, middle, and apical thirds was measured from the root canal wall surface and 1 mm away from the root canal lumen in the inner dentin. The results were compared and statistically analyzed. RESULTS: The highest pH values were obtained on the root canal walls when the calcium hydroxide was placed with Lentulo spiral filler (P > .05). There was a significant reduction in pH values in the inner dentin. When the cross sections of teeth were compared at 7 days, the Lentulo group was statistically different only in the apical third. CONCLUSIONS: Placement of the calcium hydroxide paste with a Lentulo spiral with subsequent compaction with the blunt end of a sterile paper point obtained a higher pH value on the canal walls and in the inner dentin than paper points only.

Analysis of Variance↗
PubMedDate not supplied

Effect of mechanical removal of the pulp upon the retention of odontoblasts around the pulp chamber of human third molars.

The pulp chambers of 11 freshly extracted human third molars were exposed by cutting off the roots apical to the cervical margin and the pulps were either removed with forceps and discarded or left in situ. The teeth were fixed, demineralized, divided longitudinally, embedded in resin and 2-micron sections stained with toluidine blue were examined by light microscopy. In pulp-removed specimens the percentage retention of the odontoblast layer with the predentine varied near the longitudinal division but when sectioned deeper all six specimens displayed 100% retention. The intactness of the retained odontoblast layer was mostly good as judged by the mutual close apposition of the distal ends of the cell bodies and their relation to the predentine. The retention of the odontoblast layer with the predentine may be due to the distribution of fibronectin, which others have shown is present between odontoblasts, and between odontoblasts and predentine, but lacking beneath the odontoblast layer.

Cell Adhesion↗
PubMed1998

A scanning electron microscopic study of tooth surface changes induced by tannic acid.

STATEMENT OF PROBLEM: Exposing the tooth structure to chemicals used in displacing the gingival tissue is inevitable. PURPOSE: This study was undertaken to microscopically examine the effect of tannic acid on the prepared dentin surface. MATERIAL AND METHODS: Forty recently extracted intact human teeth were mounted for buccal surface preparation. Teeth were equally divided into 10 groups. One group was kept as a control and the other teeth received a topical application of 15%, 20%, and 25% aqueous tannic acid solutions each for 5, 10, and 15 minutes at room temperature. All samples were washed, air-dried, then prepared for scanning electron microscopic examination. Two different areas in the cervical region were randomly selected and examined under magnifications of x1000 and x2000, then photographed. The assessment of the changes was performed qualitatively. RESULTS: The results showed an incomplete removal of the smear layer in all experimental samples. The astringent action of the tannic acid solution on both the smear layer and the surface peritubular dentin around the orifices of dentinal tubules had contributed to their constriction. The degree of constriction of the orifices of dentinal tubules increased as higher concentrations of tannic acid solutions were used and as the application time was further increased at each concentration. CONCLUSION: The tannic acid had an incomplete action on the removal of the smear layer. It also seemed to have an astringent action on both the smear layer and the peritubular dentin.

Astringents↗
PubMed1994

Growth kinetics of fibroblasts on bovine dentin.

In vitro dentin barrier tests published so far show several shortcomings. Therefore, we designed a new test method using bovine dentin disks on which cells were grown on one side. In this study, we evaluated the growth kinetics of L-929 mouse fibroblasts on dentin disks of 0.75-mm thickness and 4-mm diameter derived from lower incisors of freshly slaughtered bovines. The application of 50% citric acid for 30 s was optimal for the gentle removal of the smear layer from the cut dentin slices. Growth kinetics of mouse fibroblasts depended on the initially plated cell density: optimal cell growth on the disks was observed with approximately 200 cells/mm2, which was the same as the growth rate on the bottom of a cell culture vessel. Consequently, bovine dentin disks are a suitable substrate for normal cell growth, and this set-up can be used in a dentin barrier test.

Acid Etching, Dental↗
PubMed1994

Characterization of an in vitro dentin barrier test using a standard toxicant.

To characterize a new artificial pulp chamber using bovine dentin, the influence of different phenol concentrations on the cell reaction was evaluated. Bovine dentin slices of 100, 200, 300, 500, and 700 microns were cleaned, sterilized, and mounted between two 5-mm-thick glass plates with a borehole of 5 mm in diameter. L-929 mouse fibroblasts were seeded into the "pulpal" part of the device and incubated for 24 h. Different concentrations of a phenol solution as a standard toxicant were applied to a sterile cotton pellet in the "cavity" side of the device. After incubation for 24 h, the cytotoxic reaction was evaluated by cell counting after vital staining with fluorescein diacetate and related to the negative control. A dependency of the cytotoxic reaction on the concentration of the standard toxicant and on the thickness of the dentin slice was demonstrated. The simple dentin barrier test using bovine dentin may be a suitable alternative to other more complicated procedures using human dentin.

Animals↗
PubMed1996

A commercially available cell culture device modified for dentin barrier tests.

The suitability of a dentin barrier test based on a commercially available cell culture chamber was evaluated by testing the cytotoxicity of dental cements. The two chambers of the culture device as produced are separated by a membrane. This was replaced by a bovine dentin disk (500 micrometers thick). Mouse fibroblasts were grown on the "pulpal" side of the dentin for 24 h; test materials were then placed into the "cavity" side of the upper chamber. The number of viable cells was determined after 24 h. After exposure to zinc phosphate cement at a powder/liquid ratio of 2:1, approximately 100% of cells survived. A ratio of 1:1 yielded 81% survival. Only 24% and 28% of the cells survived after exposure to Ketac Fil and Ketac Silver, respectively. The light-curing glass ionomer cement (vitrebond) and zinc oxide-eugenol killed all cells. These results agree with those obtained from a previous study, wherein the dentin barrier test device was constructed in our laboratory.

Animals↗
PubMed1994

Depth of penetration and appearance of Grossman sealer in the dentinal tubules: an in vivo study.

Five teeth extracted after chemomechanical preparation (group A) and 11 extracted 1 to 7 yr after endodontic treatment (group B) were selected for this study. A 1% NaOCl was used for irrigations and a lateral condensation technique with a Grossman-type sealer was used for obturation. The teeth were fractured and prepared for and viewed by a scanning electron microscope equipped with an electron dispersive spectrometer. All root canal walls of group A were covered with a thick smear layer. Sealer, either rod-like or granular in appearance and barium free, was present in the majority of the dentinal tubules of group B usually at a distance up to 200 microns from the root canal walls; in two cases up to 900 microns. Sealer was found deepest in the middle third of the root. The smear layer did not stop sealer from entering the dentinal tubules. The differences in the depth of penetration or in the appearance of the sealer cannot be attributed to the different time periods the teeth remained in the arch after endodontic treatment.

Adult↗
PubMed1993

Migration of a Streptococcus sanguis strain through the root dentinal tubules.

The persistent presence of bacteria in the root canal system often leads to the failure of treatment. The aim of this study was to study the in vitro penetration of root dentinal tubules by bacteria. Bovine dentin was inoculated with a strain of Streptococcus sanguis, NCTC 7863; samples were taken at 10, 20, and 28 days, and bacterial penetration of the tubules was demonstrated using two techniques, scanning electron microscopy and light microscopy after Brown and Brenn staining. The results showed that S. sanguis can penetrate deep inside the tubules (792 microns). The maturity of the dentin blocks seems to be a major factor in tubule penetration.

Animals↗
PubMed1993

pH changes in root dentin over a 4-week period following root canal dressing with calcium hydroxide.

Root canals in extracted human teeth were cleaned and shaped and subsequently dressed with a calcium hydroxide root canal dressing. pH Changes in the root dentin were measured over a 4-wk period with microelectrodes in small cavities at apical and cervical levels in inner and outer dentin. The pH increased within hours in the inner dentin, peaking at pH 10.8 cervically and 9.7 apically. However, 1 to 7 days elapsed before the pH began to rise in the outer root dentin, reaching peak levels of pH 9.3 cervically and 9.0 apically after 2 to 3 wk. The results show that hydroxyl ions derived from a calcium hydroxide dressing do diffuse through root dentin. They diffuse faster and reach higher levels cervically than apically. Surface pH measurements showed that hydroxyl ions do not diffuse in more than a minor way through the intact root surface.

Adult↗