Bacterial Leakage with Mineral Trioxide Aggregate or a Resin-Modified Glass Ionomer Used as a Coronal Barrier

The effect of condensation pressure on selected physical properties of mineral trioxide aggregate

AIM

To examine the effect of condensation pressure on surface hardness, microstructure and compressive strength of mineral trioxide aggregate (MTA).

METHODOLOGY

White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Six groups each of 10 specimens were subjected to pressures of 0.06, 0.44, 1.68, 3.22, 4.46 and 8.88 MPa respectively. The surface hardness of each specimen was measured using Vickers microhardness. Cylindrical specimens of 4 mm in diameter and 6 mm in height were prepared in polycarbonate cylindrical moulds for testing the compressive strength. Five groups of 10 specimens were prepared using pressures of 0.06, 0.44, 1.68, 3.22 or 4.46 MPa. Data were subjected to one-way anova. The microstructure was analysed using a scanning electron microscope (SEM) after sectioning specimens with a scalpel.

RESULT

A trend was observed for higher condensation pressures to produce lower surface hardness values. A condensation pressure of 8.88 MPa produced specimens with significantly lower values in terms of surface hardness than other groups (P<0.001). A condensation pressure of 1.68 MPa conferred the maximum compressive strength; however, it was not statistically different. Higher condensation pressures resulted in fewer voids and microchannels when analysed with SEM. In specimens prepared with lower condensation pressures distinctive crystalline structures were observed. They tended to appear around microchannels.

CONCLUSION

Condensation pressure may affect the strength and hardness of MTA. Use of controlled condensation pressure in sample preparation for future studies is suggested.

A comparison of three gutta-percha obturation techniques to replicate canal irregularities

A split-tooth model with artificially created intracanal wall defects was used to compare three gutta-percha (GP) obturation techniques, cold lateral, warm lateral, and warm vertical. The techniques were evaluated and compared based on defect replication quality as a function of defect location and size. The obturations were evaluated on an ordinal scale, 0 to 4, based on how much each defect was replicated. There was a statistically significantly better result with both warm techniques compared to cold lateral obturation, while there was no significant difference between the warm obturation techniques.

Long-term assessment of the seal provided by root-end filling materials in large cavities through capillary flow porometry

AIM

To evaluate the long-term sealing ability of a variety of materials when used as root-end fillings.

METHODOLOGY

A total of 140 standardized horizontal bovine root sections (external diameter: 7 mm, height: 3 mm; internal diameter: 2.5 mm) were divided into seven groups, filled with either gutta-percha with AH26, Ketac Fil, Fuji IX, Tooth-Colored MTA, IRM, Ketac Fil with conditioner or Fuji IX with conditioner and submitted to capillary flow porometry at 1 and 6 months to assess minimum, mean flow and maximum pore diameters. Results of the different materials and results by material were analysed statistically using non-parametric tests; the level of significance was set at 0.05.

RESULTS

There were no significant differences between the minimum pore diameters associated with the materials at each time. At 1 month the mean flow pore diameters of Ketac Fil were significantly larger than those of gutta-percha, Ketac Fil with conditioner, Fuji IX with conditioner and IRM. There were significant differences between the maximum pore diameters at 1 month (all>IRM; Fuji IX>gutta-percha, Ketac Fil with conditioner, Fuji IX with conditioner) and 6 months (Fuji IX>gutta-percha, IRM; Ketac Fil>gutta-percha, IRM). There were significant differences in the minimum pore diameters between the different points in time for each material except IRM, in the mean flow pore diameters for each material and in the maximum pore diameters for each material except MTA.

CONCLUSIONS

All materials were associated with capillary flow. IRM root-end fillings had through pores that were smaller than those associated with other materials. Conventionally setting glass-ionomer cements had the largest pores, although dentine conditioning improved their performance. The seal of all materials improved after 6 months.

A Quantitative Comparison of the Fill Density of MTA Produced by Two Placement Techniques

This study compared the fill density of mineral trioxide aggregate (MTA) produced by hand condensation with that produced by hand condensation with indirect ultrasonic (US) activation. Sixty acrylic blocks with straight or curved canals were instrumented to an apical size 45, and weighed with a digital electronic balance. In 30 randomly chosen specimens, the canal was filled with MTA by hand condensation and weighed. The MTA was removed; the canal was rinsed and dried, and refilled using hand condensation with indirect US activation. In the other 30 specimens, the procedure was carried out identically but in reverse order. The blocks were then reweighed. The weight of the MTA fill produced by the two placement methods in the two canal configurations was analyzed by a two-way ANOVA. Hand condensation with indirect US activation resulted in an MTA fill that was statistically significantly heavier, and thus denser, than that accomplished by hand condensation alone in both curved and straight canals (p < 0.0001).

Capillary Flow Porometry to Assess the Seal Provided by Root-End Filling Materials in a Standardized and Reproducible Way

This in vitro study evaluated the root-end sealing ability of gutta-percha + AH26 (GP), Ketac-Fil, Fuji IX (FIX), tooth-colored MTA (MTA), IRM, Ketac-Fil + conditioner (Ketac-FilC), and Fuji IX + conditioner (FIXC). A total of 140 standardized bovine root sections were divided into seven groups, filled with the mentioned root-end filling materials, and, at 48 h, submitted to capillary flow porometry to assess minimum, mean flow and maximum pore diameters. Results were statistically analyzed using nonparametric Kruskal-Wallis and Dunn tests. Level of significance was set at 0.05. Using the Kruskal-Wallis tests we found that there was no significant difference between the minimum pore diameters of the different materials, but significant differences between the mean flow (p < 0.001) and maximum (p < 0.001) pore diameters could be demonstrated. For the mean flow pore diameters, there was a significant difference between FIX and all other materials, between Ketac-Fil and IRM and between Ketac-FilC and IRM. Concerning maximum pore diameters, there was a significant difference between FIX and all other materials, between Ketac-Fil and MTA, GP and IRM, FIXC and IRM, and Ketac-FilC and IRM. The data showed that each sample had leaked. Glass ionomer cements leaked more than other materials, although dentin conditioning diminished the maximum through pore diameters. This maximum pore diameter, which corresponds to the largest leak in the sample, together with the size of bacteria and their metabolites, will be indicative of the eventual leakage along the root-end filling materials.

Internal Resorption Treated with Mineral Trioxide Aggregate in a Primary Molar Tooth: 18-Month Follow-Up

Mineral trioxide aggregate (MTA) repair of a mandibular second-primary molar tooth with an inflammatory resorptive defect in the coronal third of the root canal is reported in this case. After the root canals were obturated with zinc oxide eugenol sealer, MTA was applied to the resorption cavity. The coronal cavity was then restored with a stainless steel crown. At an 18-month follow-up, the tooth was asymptomatic clinically and radiographically. According to this result, it can be concluded that MTA may be a suitable material for use in the treatment of internal resorption in the coronal third of the root canal in primary teeth.