Light-cured glass ionomer cement as a retrograde root seal

Evaluation of the effect of tracer pH on the sealing ability of glass ionomer cement and mineral trioxide aggregate

OBJECTIVES

The aim of this study was to evaluate the sealing ability and physical and chemical properties of glass ionomer cement (GIC) and mineral trioxide aggregate (MTA) using Rhodamine B at different pHs as tracer.

METHODS

Chemical analysis, pH and micro-hardness of GIC and MTA were performed. In addition dye leakage was assessed by tracer leakage using Tandem Scanning Confocal Microscope (TSM) after immersion of premolar teeth in a stock and a buffered fluorescent Rhodamine B for 24 h. Ultra-structural changes within the materials were evaluated by viewing under the field emission scanning electron microscope (FESEM).

RESULTS

GIC and MTA showed elemental peaks for silicon, aluminium and calcium while MTA also had bismuth. GIC was acidic (P = 0.001) and caused an increase in dye pH (P = 0). Immersion of MTA in any of the test solutions resulted in an increase in the pH of the solution (P < 0.05). Use of a dye solution of lower pH than the material under test increased the cement micro-hardness. GIC demonstrated marginal leakage on TSM and both increase in marginal leakage and material porosity on FESEM. MTA was not affected by the use of acidic dye but showed a tendency to take up dye within the material shown on TSM.

CONCLUSIONS

Evaluation of marginal adaptation of dental materials was shown to be dependent on the technique used for viewing the material to tooth interface, the properties of the material under study and the pH of the dye used.

Evaluation of biocompatibility of mineral trioxide aggregate with an improved rabbit ear chamber

In the present study, the biocompatibility of mineral trioxide aggregate (MTA) to the revascularization of the connective tissues was evaluated by using the improved rabbit ear chamber, in vivo. Twenty improved rabbit ear chamber was prepared from 12 male albino-rabbit by using a well through which a material could be introduced into the living vascular tissue. Ten chambers were provided for MTA, and the remaining 10 chambers were used for a calcium hydroxide-containing root canal sealer (Sealapex), as a comparator. A volume of about 1.5 mm(3) of the materials were inserted into the chamber and the interaction between the vascular tissue and materials was observed by using a biomicroscope immediately after application, at 1, 3, 5.5, 8, 24, 48, 72 h, and once a week up to 4 weeks. The results revealed that revascularization of connective tissue took place with complete recovery of microcirculation within 4 weeks in both MTA and Sealapex. However, the precipitate-barrier and brown zone around periphery of Sealapex was not observed in MTA treated samples. It can be concluded that MTA is biocompatible and does not produce any adverse site effect on microcirculation of the connective tissue.

Comparative radiopacity of tetracalcium phosphate and other root-end filling materials

AIM

This study compared the radiopacity of tetracalcium phosphate (TTCP) and 11 root-end filling materials relative to human dentine.

METHODOLOGY

Specimens of 2 mm thickness and a graduated aluminium stepwedge were placed on dental X-ray films and exposed to an X-ray beam. The optical densities of the specimens and aluminium steps were measured. The optical densities of the specimens were correlated to the equivalent thickness of aluminium with a regression analysis equation. The equation was used to calculate the equivalent aluminium thickness of each of the specimens.

RESULTS

Nine of the materials were found to be of acceptable radiopacity (at least 2 mm Al more radiopaque than dentine). TCCP and two of the glass-ionomer compounds were found to have insufficient radiopacity to be radiographically distinguishable from human dentine.

CONCLUSIONS

All the materials were found to be distinguishable radiographically from dentine, except for Vitrebond, TTCP and Ketac-Fil. Amalgam was the most radiopaque material and Ketac-Fil was the least radiopaque material tested.

Radiological assessment of the effects of potential root-end filling materials on healing after endodontic surgery

The effects of three root-end filling materials on healing following endodontic surgery were assessed radiologically and correlated with histological findings reported elsewhere. The materials compared were a light-cured glass ionomer cement (Vitrebond), a reinforced zinc oxide-eugenol cement (Kalzinol) and amalgam. The root canals of 27 two-rooted mandibular premolar teeth of six beagle dogs were inoculated with endodontic pathogenic bacteria to induce periradicular lesions. The roots were apicected and root-end cavities filled with the tested filling materials. The teeth and surrounding jaw were removed after 4 weeks (30 roots) or 8 weeks (24 roots). Radiographs were taken of each jaw section and subjected to image analysis. Healing was evaluated based on measurements of the size of the periradicular radiolucent areas. ANOVA disclosed no statistically significant differences in the size of the periradicular areas either between time periods or between materials. These results did not correlate with the tissue responses in the same material as assessed histologically and previously reported. The use of radiographs alone to assess healing after endodontic surgery in the dog mandible is unsatisfactory, and should not be regarded as a substitute for histological examination for the determination of healing.

Short-term tissue response to potential root-end filling materials in infected root canals

The short-term tissue responses to two potential root-end filling materials, a light-cured glass ionomer cement (Vitrebond) and a reinforced zinc oxide-eugenol cement (Kalzinol), were compared with that to amalgam using a previously devised experimental model. In 24 premolar teeth of beagle dogs (47 roots), a collection of endodontic pathogenic bacteria was first inoculated into the root canals to induce periradicular lesions. On each root, an apicoectomy was performed and root-end cavities prepared to receive fillings of each material. The teeth and surrounding jaw were removed after 2 weeks (23 roots) and 1 week (24 roots); they were then prepared for histological examination. The tissue response to amalgam fillings after 2 weeks and 1 week was marked by moderate or severe inflammation on all roots, and extended to < or = 0.5 mm or > 0.5 mm in 15 out of 16 roots. In contrast, after 2 weeks, the majority of roots filled with Kalzinol showed little or moderate inflammation, while the tissue response to Vitrebond was the best of the three materials, and was also the least extensive. After 1 week, the overall best tissue response was with Vitrebond, followed by Kalzinol. The differences between materials for both time periods with either none or few inflammatory cells when compared with that with either moderate or severe inflammation were not statistically significant (P < 0.02). However, the differences between materials for both time periods with no inflammation or inflammation extending < 0.2 mm when compared with that with inflammation extending > 0.2 mm (< or = 0.5 mm or > 0.5 mm) were statistically significant (P < 0.01). Apart from amalgam, in which healing was marked by the persistence of a localized focus of inflammation adjacent to the root-end filling, even though there were intersample variations, there was little overall difference in the temporal and qualitative healing response to Vitrebond and Kalzinol. Both Vitrebond and Kalzinol have potential as root-end filling materials, as the tissue response was considerably more favourable than that to amalgam even in the short-term.

Radiopacity of potential root-end filling materials

OBJECTIVES

In recent years various root-end filling materials have been suggested for clinical use. The purpose of this study was to assess the radiopacity of some potential materials according to ISO specification 6876.

STUDY DESIGN

Radiographs were taken of 1-mm thick specimens of eight materials (amalgam, Kalzinol, IRM, Super EBA, Vitrebond, Fuji II LC, Chemfil, gutta-percha); light transmission was assessed densitometrically and related to equivalent thickness of aluminum.

RESULTS

Commercial glass ionomer cements (Vitrebond, Fuji II LC, Chemfil) had radiopacities below the international standard for root canal sealers (< 3-mm aluminum); three zinc oxide-eugenol cements (Kalzinol, Super EBA, IRM) had radiopacities equivalent to 5 to 8 mm aluminum; and gutta-percha had a radiopacity equivalent to 6.1-mm aluminum.

CONCLUSIONS

We recommend that root-end filling materials should have a radiopacity greater than that for root canal sealers.

Sealing ability of potential retrograde root filling materials

The sealing ability of two potential retrograde root filling materials, a light-cured glass ionomer cement (Vitrebond) and a reinforced zinc oxide-eugenol cement (Kalzinol) was compared with that of amalgam using three methods of assessment: bacterial leakage, confocal microscopy and Indian ink leakage. the root canals of 80 extracted human single-rooted teeth were prepared. All the teeth were apicected, retrograde cavities were prepared and then divided into four equal groups of 20 teeth. The teeth were sterilised by autoclaving and the retrograde cavities filled with the test materials. In the control group, retrograde cavities in 10 teeth were left unfilled while cavities in another 10 teeth were sealed with cyanoacrylate cement. The teeth were first subjected to a bacterial leakage test using Enterococcus faecalis as a leakage marker. After which, the adaptation of the retrograde root fillings was assessed using a confocal optical microscope. Finally, the teeth were processed for the Indian ink leakage test. Bacterial leakage occurred in more teeth filled with amalgam compared with both Vitrebond and Kalzinol (P<0.001), between which there were no differences. With confocal microscopy, the size of the marginal gap was largest with amalgam and smallest with Vitrebond; all differences were statistically significant (<0.001). Finally, there was more Indian ink penetration with amalgam compared with both Vitrebond and Kalzinol (P<0.001) but there were no differences between Vitrebond and Kalzinol. Although there were individual differences within samples, overall, the three methods of assessment produced similar results. The sealing ability of Vitrebond and Kalzinol was similar and both materials were better than amalgam.

Ultrasonic preparation and obturation of root-end cavities

This study evaluated the preparation of root-end cavities using an ultrasonically activated file, and the obturation of such cavities. In the first part, the root canals of 40 extracted teeth were prepared to size 40 and irrigated with NaOCl and EDTA. The root ends were resected and the teeth inoculated with Enterococcus faecalis, incubated for 10 days and divided into four groups: control; saline; irrigation; hand instrumentation performed via a retrograde approach up to size 50 using saline irrigant; ultrasonic instrumentation with prebent size 40 K-flex file inserted into a Piezon Master using saline irrigant. The teeth were fixed, sectioned longitudinally and viewed under scanning electron microscopy. Bacterial and smear layer scores were obtained at 1, 3, and 5 mm from the resected end. The bacterial scores for control and saline groups were similar; the scores for each instrumentation group were significantly lower than the control group (P<0.001). In addition, there were significantly fewer bacteria in the ultrasonic group compared with the hand instrument group (P<0.001). The smear layer scores for control and saline groups were similar, and significantly lower than in either instrumentation group (P<0.001). In the second part, root-end cavities were ultrasonically prepared in 20 extracted teeth. Ten cavities were filled with amalgam, and 10 with thermoplasticized gutta-percha and Grossman's sealer. After 24-h storage, the root ends were immersed in dye for 48 h. Cross-sectional slices of the obturated part of the root were evaluated using both light and confocal microscopy for dye leakage along the interface of filling material and dentine. There were no statistical differences between the leakage of amalgam and gutta-percha root-end fillings, nor between the two methods of microscopy.

Cytotoxicity of potential retrograde root-filling materials

The cytotoxicity of potential retrograde root-filling materials was assessed using the Millipore filter method. A light-cured glass ionomer cement, Vitrebond (VB), and three reinforced zinc oxide-eugenol cements, Kalzinol, IRM and ethoxybenzoic acid (EBA) cement, were compared with amalgam. Twenty standardized pellets of each material, 10 fresh and 10 aged by storage in sterile distilled water for 72 h were produced. Ten filters were included as controls: five filters with a cell monolayer, but without test specimens, and another five without cells but with test specimens. Fresh IRM exhibited the most pronounced cytotoxic effect and the difference was statistically significant compared with all the other materials. There was no statistically significant difference between fresh VB, Kalzinol, EBA cement and amalgam. When aged, Kalzinol was the most cytotoxic and the difference was statistically significant compared with the other materials. Aged IRM was the second most cytotoxic material and this too was statistically different. The cytotoxicity of VB, EBA, and amalgam did not differ significantly from one another.

Antibacterial activity of potential retrograde root filling materials

The antibacterial activity of potential retrograde root filling materials was assessed using the agar diffusion inhibitory test. A light-cured glass ionomer cement (Vitrebond) and three reinforced zinc oxide-eugenol cements (Kalzinol, IRM & ethoxybenzoic acid [EBA] cement) were compared with amalgam, a commonly used retrograde root filling material. Forty standardized pellets of each material were produced. Fresh, and materials aged for 1 week in sterile distilled water, were placed on blood agar plates inoculated with Streptococcus anginosus (milleri) or Enterococcus faecalis. At intervals of 3, 7 and 10 days, the presence and diameter of zones of inhibition were recorded. The diameter of the zones of inhibition increased with time for all materials, both fresh and aged. Vitrebond had the most pronounced antibacterial activity against both bacteria, producing the largest zone of inhibition, followed by Kalzinol. Amalgam had no measurable inhibitory effect whether aged or fresh, regardless of the period of exposure. There was no statistically significant difference in the response of the two bacteria. However, there were statistically significant differences between materials, period of exposure, and between fresh and aged materials (P < 0.001). Kalzinol, IRM and EBA cement were more antibacterial when aged than fresh, whilst Vitrebond was more active when fresh. Vitrebond was the only material for which the diameter of the zones of inhibition was reduced after ageing but it had the most pronounced antibacterial activity compared with the other materials. The antibacterial activity of the materials was ranked in the following order: Vitrebond > Kalzinol > (IRM = EBA cement) > amalgam.