The association between complete absence of post-treatment periapical lesion and quality of root canal filling.

AIM: The technical quality of a root canal treatment is clinically judged by the apical extension and homogeneity of the filling material imaged by periapical radiographs (PA). The aim of this experiment was to evaluate the association between the technical quality of the root canal filling and treatment outcome. MATERIALS AND METHODS: In 234 teeth (268 roots) that underwent root-canal treatment, the quality of the root canal filling as well as the outcome of the treatment were assessed with both PA and cone-beam computed tomography (CBCT) 2 years after treatment. Satisfactory root filling on PA was defined as 0-2 mm within the radiographic apex without voids; on CBCT scans, the apical end of the canal replaced the radiographic apex. The outcome predictors were analyzed using multivariate logistic regression. RESULTS: At recall, periapical radiolucent areas were absent in 198 (74%) roots on PA and 164 (61%) roots on CBCT scans. The presence of preoperative periapical radiolucency and the quality of root filling and coronal restoration were identified by both PA and CBCT as outcome predictors (p < 0.01). Complete absence of post-treatment periapical radiolucency was observed in CBCT scans in 81% and 49% of satisfactory and unsatisfactory root fillings, respectively, as compared to 87% and 61% revealed by PA. CONCLUSION: Satisfactory root fillings were associated with a favorable outcome, confirmed by both PA and CBCT. CLINICAL RELEVANCE: The outcome of root canal treatment is improved once the filling is 0-2 mm from the apex, and no voids could be detected. Technical skills and performance of root canal filling procedures should be emphasized, and suitable methods should be developed in order to achieve more compacted filling materials without voids and at the correct length.

Effect of different dye solutions on the evaluation of the sealing ability of Mineral Trioxide Aggregate.

Alkaline materials have shown incompatibility with methylene blue dye in leakage experiments. The goal of the present study was to analyze the effect of different dyes on the evaluation of the apical sealing ability of Mineral Trioxide Aggregate root-end fillings. Fifty-six extracted human canines were submitted to root canal instrumentation and obturation. After apical resection, retrograde cavities were prepared and teeth were randomly divided into four experimental (n = 13) and two control groups (n = 2). The following root-end filling materials were used: groups 1 and 2--Pro Root MTA (Dentsply), groups 3 and 4--zinc oxide-eugenol cement (ZOE). Teeth in groups 1 and 3 were immersed in 2% methylene blue solution, while teeth in groups 2 and 4 were immersed in 0.2% rhodamine B in a reduced pressure environment for 48 hours. Teeth were then longitudinally sectioned and leakage was evaluated. Results were submitted to statistical analysis (ANOVA and Tukey's test). Group 1 presented the least leakage (p < 0.05). It was concluded that the evaluation of the sealing ability of MTA is influenced by the dye used, since this material presented better sealing ability when evaluated with Methylene Blue, but was similar to ZOE when evaluated with rhodamine B.

Effect of different dye solutions on the evaluation of the sealing ability of mineral trioxide aggregate

Tem sido demonstrada a incompatibilidade de materiais alcalinos com a solucão corante de azul de metileno utilizada em testes de infiltracão marginal. O objetivo do presente estudo foi analisar a influência de diferentes solucões corantes na avaliacão do selamento apical proporcionado pelo agregado de trióxido mineral. Cinqüenta e seis caninos humanos extraídos tiveram seus canais radiculares instrumentados e obturados. Após a seccão da porcão apical, cavidades retrógradas foram preparadas e os dentes divididos aleatoriamente em quatro grupos experimentais (n = 13) e dois controles (n = 2). Foram utilizados os seguintes materiais retrobturadores: grupos 1 e 2 - Pro Root MTA (Dentsply); grupos 3 e 4 - cimento de óxido de zinco e eugenol (OZE). Em seguida, os dentes dos grupos 1 e 3 foram imersos em solucão de Azul de Metileno a 2% e dos grupos 2 e 4 em solucão de Rodamina B a 0,2% por 48 horas em ambiente com vácuo. Decorrido este período, os dentes foram seccionados longitudinalmente, e a infiltracão marginal foi analisada. Os dados obtidos foram submetidos à análise estatística (Análise de variância e teste de Tukey). Os resultados demonstraram que o Grupo 1 apresentou menor infiltracão apical que os demais (p < 0,05). Conclui-se que a avaliacão da capacidade seladora do MTA é influenciada pela solucão corante, uma vez que o mesmo apresentou melhores resultados com o Azul de Metileno e infiltracão marginal semelhante à do OZE quando avaliado em solucão de Rodamina B.

[Compressive strength and deformation of dental cements]. / Kompresjonsstyrke og deformering hos dentale sementer.

Several dental cements have been tested for compressive strength, modulus of elasticity and plastic strain at fracture. Sylindrical specimens (4 x 6 mm) were compressed to fracture with two different crosshead speeds (2 mm/min, 0.1 mm/min) at two temperatures (23 +/- 1 degrees C and 37 +/- 1 degrees C). The results showed that the zinc phosphate cement had relatively high strength and a very small elastic and plastic strain during compression. The luting type of glass-ionomer cements showed properties near to that of the zinc phosphate cement. The other cements had either lower strength or higher elastic and plastic deformation than the zinc phosphate cement. Several cements showed a marked reduction of the mechanical properties when tested at a low crosshead speed or at 37 degrees C.

Stress/strain behavior of some dental luting cements.

The compressive strength, modulus of elasticity and the plastic strain at fracture have been studied for several dental luting cements. Stress/strain diagrams of cylindrical specimens using two different crosshead speeds (2 mm/min and 0.1 mm/min) at 23 degrees and 37 degrees C showed that large differences existed between various luting cements. A zinc phosphate cement exihibited high strength, high modulus of elasticity and a small plastic strain at fracture. A resin cement also had high strength, but elastic and plastic strains were high. A polycarboxylate and an EBA-cement both showed low values of strength and modulus of elasticity combined with a high degree of plastic deformation at fracture. Testing with low strain rate at 37 degrees C accentuated the differences between these two materials and the zinc phosphate cement.

The extent of slits at the interfaces between luting cements and enamel, dentin and alloy.

Four different cements were used to assess the presence of slits at the cement/tooth or the cement/alloy interfaces using a tooth-crown model. The model consisted of ground sections of teeth and plane plates of silver/palladium alloy. The plates were fixed with bolts between two brass plates and with three different dimensions of the cement film between tooth and alloy, i.e. 50 micrometer, 100 micrometer and 200 micrometer. The tooth-alloy specimens were sectioned and the adaption of cements was studied with an indirect technique (replica) in a scanning electron microscope. The extent of slits was expressed as the length of all slits relative to the total length of the interface in each specimen. The results showed that the zinc phosphate cement and polycarboxylate cement exhibited a slight to moderate tendency to formation of slits at the interfaces. The EBA cement had a small extent of slits adjacent to thin cement films, but more slits were observed with increasing film thickness. The composite resin cement had a marked tendency to slit formation independent of the cement film thickness.

Adhesive bonding of dental luting cements; influence of surface treatment.

Tensile bond strength of four different luting cements to smooth dentin surfaces was measured. A chisel edged, stainless steel ring was cemented to the butt end of a dentin cylinder. The dentin was polished to a plane and smooth surface before cementation. The cements were also applied to dentin surfaces that were treated with a pumice slurry, etched with different acid solutions, or covered with different liners. The results showed that the polycarboxylate cement had a tensile bond strength to smooth, untreated dentin of approximately 4 MN/m2. The zinc phosphate and EBA cements had a bond strength of 0,6 MN/m2 and the composite resin cement had no measurable bond to untreated dentin. All dentin treatments showed in general a decreasing effect on the bond strength of zinc phosphate, polycarboxylate and EBA cements, whereas that of composite resin cement showed a slight increase.

[Biological testing of pulp-preserving agents on the pulp of rat molars]. / Biologische Prüfung von Pulpaschutzmitteln an der Molarenpulpa der Ratte.

The effects of calxyl, ZOE, zinc oxide without eugenol, and zinc oxide with an antibacterial substance (glutaraldehyde) were tested on perforated molar pulps of rats. All of the substances tested were found to lead to the same initial reactions (acute inflammation and partial necrosis). Calxyl and ZOE yielded unfavorable results. There was a negligible tendency of the pulp toward hard tissue demarcation. Zinc oxide without eugenol improved the formation by the pulp of secondary tin. - The use of glutaraldehyde resulted in a less pronounced spread of inflammation as well as in the formation of new hard tissue in one half of the cases. Molars of rats are particularly suitable for biologically examining the local toxicity of pulpal protectives and the regeneration of the pulp. The results presented in this paper are discussed from the point of view of pulp-preserving therapy and of avoiding invasion by germs.

Specification test for the solubility and disintegration of dental cements: a critical evaluation of its meaning.

The specification test for solubility and disintegration is an essential screening test for the quality control of certain cement types. No cement fails it can be considered for use; however, the test has only a limited clinical significance because it does not give an indication of the stability of the fully hardened cement matrix either in oral fluids or water. Instead, it gives a measure of the content of the soluble reaction intermediate present in cements that are still hardening and where the matrix has not fully formed. The test relates, therefore, to early vulnerability to aqueous attack and hardening rate. The period of test is, in fact, an atypical one and the true extent of the erosion of the cement matrix is obscured by the presence of soluble reaction intermediates. Long-term extrapolations cannot be made and so test results for broadly satisfactory cements within a category cannot be used for valid comparisons of clinical excellence, and they can be used even less to compare different cement types with different setting reactions. For example, in general, the dental silicate cement has a higher solubility and distinegration figure than the zinc phosphate cement because it contains soluble sodium salt and hardens more slowly. However, it is more stable under oral conditiont an indication of the vulnerability of the forming matrix to attack. The test is not valid when applied to zinc oxide-eugenol cements because the products of decomposition are either virtually water-insoluble or volatile and therefore not measured under the conditions of the test. A method is suggested for overcoming this deficiency. The test needs to be supplemented by other tests done on fully hardened cements for longer periods of time and in mediums that can represent oral conditions. One example would be to stimulate acid conditions developed in stagnation areas. A total estimation of decomposition products, both soluble and insoluble, is called for rather than the determination of soluble materials only.

[The use of energy in casting and the viscosity of zinc oxide-eugenol pastes]. / Uber die Kraft bei der Abformung und über das Fliessverhalten von Zinkoxid-Eugenol-Pasten

The recorded diagrams give information on the viscosity (consistency) at any given time. The force data indicate the difference in the viscosity (consistency). The line in the graph reflects the setting behavior. A flow test should be included in the specification of impression materials. The consistency test provided for in the ADA specification does not have any clinical significance, neither have changes in the load.

Cements for permanent luting: a summarizing review.

Three cement systems are favored for permanent luting of cast restorations. These include zinc phosphate, reinforced zinc oxide-eugenol, and polycarboxylate cements. Although others have been used in the past and new luting media are anticipated for the future, the status of currently used cement for luting is based mainly on the results of laboratory research and on clinical experience. Zinc phosphate cement, with an impressive 100-year history, currently holds the advantage. Future comprehensive clinical studies, correlated with results of physical and biological testing, may eventually direct the clinican's preference to another, newer material. It is hoped that properties and strength values that are clinically significant also will be identified, so that laboratory tests can be more predictive of clinical success.