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PubMed2005

Apical diffusion of calcium hydroxide in an in vitro model.

An in vitro agar model was developed to study the effect of intracanal medicaments on periapical tissues and was used to study the diffusion of three calcium hydroxide (Ca(OH)2) medicaments of varying viscosity through simulated root canals with various sizes of apical foramina. Experimental medicaments were added to pipette tips used to represent tooth roots, which were fixed in syringes containing brain heart infusion agar and calcium-reactive dye. OH and Ca concentrations were measured in the agar at 30 minutes and 24 hours. Ca concentration and pH increased with larger aperture sizes, and higher pH and Ca diffusion was produced by a 10% Ca(OH)2 solution than was produced by Pulpdent or a Ca(OH)2 paste. The results suggest that the properties of the Ca(OH)2-containing vehicle could affect the action of the medicament in the periapical tissues.

Analysis of Variance↗
PubMed2005

Sealer penetration and apical microleakage in smear-free dentin after a final rinse with either 70% isopropyl alcohol or Peridex.

Tensioactive agents may alter dentinal wettability allowing increased sealer penetration into dentinal tubules. This may improve the apical seal and better entomb remaining bacteria. The purpose of this study was to determine if a final rinse with either 70% isopropyl alcohol or Peridex in instrumented, smear-free canals would affect apical microleakage or Roth's 801 sealer penetration into dentinal tubules. Sixty root segments were instrumented followed by smear layer removal. The segments were randomly divided into three groups receiving a final rinse with 6% sodium hypochlorite (NaOCl), 70% isopropyl alcohol or Peridex. Obturation was completed using lateral compaction and Roth's 801 sealer pigmented with carbon black. Microleakage was measured by fluid filtration. Sealer penetration was measured using light microscopy. No significant differences were found between groups for microleakage or sealer penetration. Although a final rinse with either 70% isopropyl alcohol or Peridex did not increase sealer penetration, neither significantly affected apical microleakage compared to NaOCl.

2-Propanol↗
PubMed1990

Penetration of dentine by three oral bacteria in vitro and their associated cytotoxicity.

Three common oral bacteria, namely Streptococcus sanguis, Actinomyces viscosus and Corynebacterium spp. were studied with regard to their ability to penetrate etched and unetched dentine and for their effect on underlying cell cultures. The test organisms were grown in cylinders above dentine slices 100 and 500 microns thick for 72 hours. The slices were in contact with tissue culture medium covering a layer of fibroblasts. Penetration of 100 microns slices was most rapid with S. sanguis, followed by A. viscosus and Corynebacterium. The pattern was similar but slightly delayed when 500 microns slices were used, but in most cases penetration had occurred by 72 hours. The presence of a smear layer had no effect on the results obtained. Following penetration, cell destruction was most extensive with S. sanguis, the most cytotoxic organism, followed by Corynebacterium and A. viscosus. In the limited number of dishes where no penetration occurred there was little effect on cell numbers.

Acid Etching, Dental↗
PubMed1992

Scanning electron microscopic study of the apical dentine surfaces lased with ND:YAG laser following apicectomy and retrofill.

The purpose of this investigation was to study the effects of a Nd:YAG laser on the cut surface of teeth using scanning electron microscopy (SEM). Eighteen single-rooted teeth were cleaned, shaped, and obturated with gutta-percha and root canal sealer. The apical 3 mm of each tooth were resected with a diamond fissure bur, and the teeth were randomly divided into two groups of nine teeth each. The resected surface of each root in one group was lased twice. The duration of lasing and the number of pulses were recorded for each tooth. The teeth were air dried, mounted on stubs, sputter-coated with gold-palladium and examined under SEM. Application of the Nd:YAG laser caused melting of apical dentine surfaces. The melted material resembled the appearance of glazed interconnected droplets. Resolidification and recrystalization of the melted areas appeared to be incomplete and discontinuous. Some areas between the glazed regions appeared similar to those of non-lased apical dentine resected root surfaces.

Apicoectomy↗
PubMed1993

The penetration of root canal sealers into dentinal tubules. A scanning electron microscopic study.

The purpose of this study was to evaluate the effect of smear layer on penetration of four root sealers into dentinal tubules. Sixty-four, recently extracted, human maxillary and mandibular incisors were used. Following removal of the crowns, the pulps were extirpated and the root canals instrumented. The teeth were then divided into two groups. The teeth in the control group were irrigated with saline solution and the experimental group treated with EDTA and NaOCl. Each main group was then divided into four sub-groups and the root canals filled with Diaket, N2 Universal, SPAD and Forfenan as recommended by the manufacturers. The teeth were split longitudinally and examined using scanning electron microscopy. A quantitative assessment was made of sealer penetration into the dentinal tubules in the coronal, middle and apical parts of each root canal. It was observed that the smear layer obstructed the penetration of the tubules by the sealers. However, in the experimental group, the penetration into dentinal tubules was better with Diaket, N2 and SPAD, than with Forfenan (P < 0.01). It was concluded that this penetration could be affected by physical and chemical properties of root canal filling materials.

Analysis of Variance↗
PubMed1994

Radicular penetration of hydrogen peroxide during intra-coronal bleaching with various forms of sodium perborate.

The development of external cervical root resorption following internal bleaching of discoloured pulpless teeth is associated with the use of hydrogen peroxide. The aim of the study was to determine radicular penetration of hydrogen peroxide following intracoronal bleaching with various forms of sodium perborate. 63 extracted human incisors were root filled and stained artificially. Standardized cementum defects were created on the mesial and distal aspects of the root directly below the cemento-enamel junction (CEJ). Using the walking bleach technique all teeth were bleached for a 6-day period, with replacement of the bleaching paste after days 1 and 3. Sodium perborate monohydrate (MH), trihydrate (TRH) or tetrahydrate (TH) was mixed with H2O2 or H2O and subsequently placed intracoronally 1 mm below the labial CEJ. The teeth were divided into six groups: I. MH + H2O2(30%) (n = 12); II. TRH + H2O2(30%) (n = 12); III. TH + H2O2(30%) (n = 12); IV. TH + H2O (n = 12); V. TH + H2O, gel (n = 12); VI. no bleaching paste (n = 3). At baseline and at days 1, 3 and 6 the amount of H2O2 taken up from the surrounding medium of each root was indirectly recorded and calculated as p.p.m. Almost all teeth of the experimental groups showed leakage of hydrogen peroxide compared to those of the control group. The radicular penetration of hydrogen peroxide was significantly higher in teeth of groups I and III than in those of groups IV and V (P < or = 0.001). In conclusion, the amount of hydrogen peroxide leakage depends, among other factors, on the form of sodium perborate used.(ABSTRACT TRUNCATED AT 250 WORDS)

Borates↗
PubMed1995

The smear layer: a phenomenon in root canal therapy.

When the root canals are instrumented during endodontic therapy, a layer of material composed of dentine, remnants of pulp tissue and odontoblastic processes, and sometimes bacteria, is always formed on the canal walls. This layer has been called the smear layer. It has an amorphous, irregular and granular appearance under the scanning electron microscope. The advantages and disadvantages of the presence of smear layer, and whether it should be removed or not from the instrumented root canals, are still controversial. It has been shown that this layer is not a complete barrier to bacteria and it delays but does not abolish the action of endodontic disinfectants. Endodontic smear layer also acts as a physical barrier interfering with adhesion and penetration of sealers into dentinal tubules. In turn, it may affect the sealing efficiency of root canal obturation. When it is not removed, the durability of the apical and coronal seal should be evaluated over a long period. If smear layer is to be removed, EDTA and NaOCl solutions have been shown to be effective, among various irrigation solutions and techniques, including ultrasonics, that have been tested. Once this layer is removed, it should be borne in mind that there is a risk of reinfecting dentinal tubules if the seal fails. Further studies are needed to establish the clinical importance of the absence or presence of smear layer.

Chelating Agents↗
PubMed1996

Penetration of smeared or nonsmeared dentine by Streptococcus gordonii.

The purpose of this study was to investigate the penetration of smeared and nonsmeared dentine by Streptococcus gordonii. Prepared human roots, grouped as either nonsmeared or smeared, were immersed in a suspension of S. gordonii cells for 3 weeks. The roots were then prepared for scanning electron microscopy and histological analysis. Dentine discs prepared from coronal dentine were grouped similarly. Using a fluid filtration apparatus, the hydraulic conductance (Lp) of each disc was determined before and after incubation with bacterial suspension. Scanning electron microscopy evaluation of the roots following infection with bacteria showed no change in the smear layer (P < 0.0001). Histological sections revealed that bacterial penetration of all the nonsmeared samples had occurred, while nine out of 10 smeared samples showed no bacterial penetration (P < 0.0001). The Lp of the nonsmeared discs was significantly reduced by 42% (P < 0.0001) after bacterial penetration. However, the smeared samples revealed a 1% reduction in Lp which was not significant (P > 0.05). The results suggest that dentinal smear layers are an effective barrier to dentinal tubule invasion by S. gordonii.

Dental Pulp Cavity↗
PubMed1996

The effect of tubular penetration of root canal sealers on dye microleakage.

An in vitro study of a possible correlation between penetration of dentinal tubules by four root canal sealers and microleakage of external fluids into the canal was done using a dye leakage method and scanning electron microscopy. The root canals of 45 teeth were instrumented and the smear layer removed prior to obturation of root canals with gutta-percha and one of four sealers: Diaket, Endomethasone, CRCS or Ketac-Endo. The extent of leakage was scored after immersion in India ink for 72 h. The same specimens were also used for scanning electron microscopic evaluation. There was a statistical difference in leakage patterns between the groups (P < 0.05). Diaket had lower microleakage scores than the other sealers (P < 0.05). When the scores for penetration of sealers into the tubules were analysed, Ketac-Endo demonstrated the least penetration (P < 0.01). There appeared to be a converse relation between tubular penetration and dye leakage, but the correlation was not statistically significant (P > 0.05).

Administration, Topical↗
PubMed1996

Calcium ion diffusion from calcium hydroxide-containing materials in endodontically-treated teeth: an in vitro study.

The aim of this in vitro study was to determine the amount and duration of diffusion of calcium ions from both a calcium hydroxide-containing root canal sealer and an intracanal medicament, through the apical foramen and the dentinal tubules of endodontically-treated teeth. The root canals of 88 freshly extracted single-rooted teeth were prepared using the modified double flared, balanced force technique with patency filing. The teeth were divided into four test groups of 20 teeth each and a control group of eight teeth. One group was dressed with a non-setting calcium hydroxide while the other was obturated using cold lateral condensation of gutta-percha with a calcium hydroxide-containing sealer. An artificial root defect was created in the apical third of the root of the teeth in the other two groups and the root canals were either dressed or obturated in the same way as the first two groups. All groups were incubated at 37 degrees C and were sampled for calcium diffusion after 1, 2 and 3 days and 1, 2, 3, 4 and 8 weeks. There was statistically significantly more calcium diffusion with the non-setting groups compared with the sealer groups (P < 0.05). There was more calcium ion diffusion from teeth with a patent apical foramen than those with an artificial resorptive root defect (P < 0.05).

Analysis of Variance↗
PubMed2004

Extraradicular diffusion of hydrogen peroxide and pH changes associated with intracoronal bleaching of discoloured teeth using different bleaching agents.

AIM: To evaluate the extraradicular pH and hydrogen peroxide (HP) diffusion when either 35% carbamide peroxide (CP), 35% HP or sodium perborate (SP) is used for intracoronal bleaching of artificially discoloured teeth. METHODOLOGY: Single rooted extracted human premolars were stained with whole blood cells. After shaping and cleaning, they were root filled and a base cement placed 1 mm below the buccal cementoenamel junction (CEJ). Four cemental defects were prepared just below the CEJ on each root surface. The teeth were randomly divided into four groups of 11 specimens, and intracoronally bleached using CP, HP, SP or distilled water (CL). Each tooth was suspended in a vial of distilled water and bleached for 7 days. The pH of the extraradicular distilled water was tested at 0, 1, 2 and 7 days and the HP that diffused through the root quantified using the Ferrous Oxidation-Xylenol Orange 2 Assay. The results were analysed using the one-way anova and Scheffe tests. RESULTS: Carbamide peroxide produced the greatest increase and HP the least pH change (P < 0.05 except day 1), SP was intermediate. From day 1 onwards, radicular diffusion of HP was greatest with HP and least with CP (P < 0.01), again SP was intermediate. There was no significant difference between CP and SP. CONCLUSIONS: Carbamide peroxide had very low levels of extraradicular diffusion of HP, in the presence of cemental defects. It could be an alternative to the other intracoronal bleaching agents.

Adolescent↗
PubMed2004

Effect of obturation technique on sealer cement thickness and dentinal tubule penetration.

AIM: To compare the average sealer cement film thickness and the extent and pattern of sealer penetration into dentinal tubules in association with four obturation techniques in curved root canals. METHODOLOGY: Mesial canals of 44 extracted mandibular molars were randomly divided among the SimpliFill, continuous wave, Thermafil and 0.04 matched taper (master cones) lateral compaction obturation groups (22 canals per group). AH26 sealer cement was coloured blue-black using Sudan Black B dye. Roots were sectioned 1, 3 and 5 mm from the working length. Specimens were photographed under 25x magnification, mounted as 35 mm slides and projected. Average sealer cement thickness (measured at 10 points around the canal wall), depth of dentinal tubule penetration and frequency of voids were determined at the 1, 3 and 5 mm levels. Data were analysed statistically for effect of obturation technique and level of section on sealer thickness and on the depth and distribution of tubule penetration. RESULTS: Thermafil demonstrated superior GP adaptation at all levels with a mean overall sealer cement thickness of 2.2 microm, followed by lateral compaction (11.1 microm), continuous wave (12.2 microm) and SimpliFill (47.6 microm). SimpliFill also demonstrated the highest frequency of voids (P < 0.05). Sealer cement penetrated dentinal tubules as far as the outer one-third of dentine, with greater penetration observed buccally or lingually (P < 0.001). Penetration was not significantly affected by obturation technique, but on average was deeper and more frequent at the 3 and 5 mm levels than at the 1 mm level (P < 0.001). CONCLUSIONS: Sealer thickness was strongly dependent on obturation technique. Assuming that minimal sealer thickness and fewer voids are good measures of long-term sealing ability, Thermafil resulted in the best outcome. Consistent, extensive sealer penetration into dentinal tubules was seen and was unrelated to the obturation technique.

Bismuth↗
PubMed2006

Real-time atomic force microscopy of root dentine during demineralization when subjected to chelating agents.

AIM: To explore the potential of atomic force microscopy (AFM) for the examination of changes to dentine surfaces during demineralization and evaluate qualitatively the effect of EDTA, EDTAC and citric acid. METHODOLOGY: Nine canine teeth were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, each root was embedded in an epoxy cylinder and discs approximately 5 mm thick were cut. A standard metallographic procedure was then used to prepare the surfaces for observation. From the central portion of these samples, two specimens were symmetrically prepared per tooth so that a total number of 18 samples was produced. To allow the use of a liquid cell during AFM, the samples were embedded in silicone rubber and were then randomly divided into three groups, as follows: group 1: 17% EDTA (pH 7.7), group 2: 17% EDTAC (pH 7.7) and group 3: 10% citric acid (pH 1.4). Topographical images were acquired during the demineralization process, allowing real-time observation of the dentine surface. Two operators assigned scores to the AFM images using a double-blind method. anova analysis with random effects (P < 0.05) was used to compare the results. RESULTS: The average scores were 6.13 +/- 0.35 for EDTAC, 7.36 +/- 0.23 for EDTA and 14.55 +/- 1.21 for citric acid. Citric acid was statistically different from EDTA and EDTAC while EDTA and EDTAC were not statistically different. CONCLUSIONS: The most effective demineralizing substance was citric acid. The methodology developed for real-time observation of dentine surfaces is a valuable method to evaluate demineralization.

Chelating Agents↗