Wear profile of canal wall surfaces and bond strength of endodontic sealers after in situ acid challenge.

AIM: To evaluate the wear of root wall surfaces, the bond strength of sealers to dentine and the demineralization around root filling materials after canals were exposed to acid challenge in situ. METHODOLOGY: Eighty-seven roots of mandibular incisors were selected. Thirty-two were used in the laboratory bond strength study (n = 8), and 55 in the in situ study (n = 11). Root canals were prepared biomechanically and then filled with gutta-percha and AH Plus, MTA Fillapex, Sealapex or Endofill. For 14 days, 11 participants used intra-oral devices with five sterilized roots (four experimental and one control - only canal prepared). Drops of sucrose were dripped onto roots allowing the accumulation of biofilm on canal surfaces. Roots were removed, sectioned and analysed for the following: bond strength of filling material using a push-out test and also wear profile and dentine demineralization using confocal microscopy. Bond strength (MPa) was evaluated by two-way anova and Tukey test (α = 0.05), and wear profile was assessed by Kruskal-Wallis and t-tests (α = 0.05). RESULTS: AH Plus had the highest bond strength values. Intermediate results were found in roots with MTA Fillapex and Endofill, whilst Sealapex had inferior results (P < 0.05). No significant differences were found amongst root thirds (P > 0.05). For wear profile, samples were associated with degradation of the filling materials after exposure to the oral environment (P < 0.05). Roots had signs of demineralization around the filling material when Sealapex and Endofill were used. CONCLUSIONS: Sealers were not able to prevent degradation of the adhesive interface and dentine. AH Plus and MTA Fillapex had superior bond strength to dentine and less intense demineralization around the root filling.

Addition of ammonium-based methacrylates to an experimental dental adhesive for bonding metal brackets: Carious lesion development and bond strength after cariogenic challenge.

INTRODUCTION: In this study, we evaluated the caries inhibition and shear bond strength achieved with the addition of the antibacterial monomer [2-(Methacryloyloxy)ethyl] trimethylammonium chloride (MADQUAT) to an adhesive used to bond orthodontic brackets. METHODS: Experimental adhesives were formulated with addition of 0% (control), 5%, or 10% MADQUAT followed by measurement of the degree of conversion. These adhesives were used to lute brackets to the enamel of premolars (n = 30). Biofilm from a microcosm model was cultivated in half of the specimens under cariogenic challenge for 5 days. The brackets were subjected to a shear bond strength test followed by measurement of the internal hardness of the enamel around the brackets to calculate the integrated mineral loss. RESULTS: The addition of MADQUAT slightly increased the degree of conversion. Adhesive containing 10% MADQUAT significantly reduced the integrated mineral loss around the bracket but also resulted in the lowest values of bond strength. No effects on bond strength and integrated mineral loss were observed with the addition of 5% MADQUAT to the adhesive. The cariogenic challenge did not affect the bond strength and the failure mode. CONCLUSIONS: MADQUAT was effective to reduce the integrated mineral loss only when added to the adhesive at a concentration of 10% despite the reduction of bond strength.

Vertical root fracture in upper premolars with endodontic posts: finite element analysis.

Upper premolars restored with endodontic posts present a high incidence of vertical root fracture (VRF). Two hypotheses were tested: (1) the smaller mesiodistal diameter favors stress concentration in the root and (2) the lack of an effective bonding between root and post increases the risk of VRF. Using finite element analysis, maximum principal stress was analyzed in 3-dimensional intact upper second premolar models. From the intact models, new models were built including endodontic posts of different elastic modulus (E = 37 or E = 200 GPa) with circular or oval cross-section, either bonded or nonbonded to circular or oval cross-section root canals. The first hypothesis was partially confirmed because the conditions involving nonbonded, low-modulus posts showed lower tensile stress for oval canals compared to circular canals. Tensile stress peaks for the nonbonded models were approximately three times higher than for the bonded or intact models, therefore confirming the second hypothesis.

In vivo effect of a resin-modified glass ionomer cement on enamel demineralization around orthodontic brackets.

Because the risk of dental caries increases with the use of orthodontic appliances and its control cannot depend only on the patient's self-care, this study evaluated the effect of a glass ionomer cement on reducing enamel demineralization around orthodontic brackets. Fourteen orthodontic patients were randomly divided into 2 groups of 7; they received 23 brackets fitted to their premolars, bonded with either Concise (3M Dental Products, St Paul, Minn), a composite resin (control group), or Fuji Ortho LC (GC America, Chicago, Ill), a resin-modified glass ionomer cement (experimental group). The volunteers lived in a city that has fluoridated water, but they did not use fluoridated dentifrices during the study. After 30 days, the teeth were extracted and longitudinally sectioned; in the enamel around the brackets, demineralization was assessed by cross-sectional microhardness. The determinations were made at the bracket edge cementing limits, and at occlusal and cervical points 100 and 200 microm away from them. In all of these positions, indentations were made at depths from 10 to 90 microm from enamel surface. Analysis of variance showed statistically significant effects for position, material, depth, and their interactions (P<.05). The Tukey test showed that the glass ionomer cement was statistically more efficient than the control, reducing enamel demineralization in all analyses (P<.05). The use of glass ionomer cement for bonding can be encouraged because it decreases the development of caries around orthodontic brackets.

Capacidad de penetración de los agentes adhesivos con acondicionamiento total que utilizan diferentes solventes / Capability of penetration of the adhesive agents with full conditioning that use different solvents

Los agentes adhesivos constituyen un importante y necesario requisito en la odontología restauradora. Los adhesivos dentales con acondicionamiento total basan su eficacia en la formación de la capa híbrida y en la dentina. Se han evaluado distintos agentes adhesivos que utilizan diferentes solventes como vehículo de penetración: Etanol (Single Bond, 3M), Acetona (Solo Bond M, VOCO) y agua (One Coat Bond- COLTENE), para lo cual se seleccionaron 30 terceras molares humanas recientemente extraídas, almacenadas en agua destilada a 4 °C (recomendaciones de ISO TR 11405), las cuales se dividieron en tres grupos de 10 piezas cada uno, que se asignaron de acuerdo con su solvente Acetona, Grupo C: solvente agua, realizándose cavidades clase II, que fueron restauradas posteriormente con resina compuesta, (Tetric Ceram - Vivadent). De estas preparaciones se obtuvieron láminas (mesiodistal) que fueron tratadas con HCI, NAOCL para así exponer las prolongaciones de resina y luego ser observadas mediante el MEB. Los resultados nos muestran que sí existen diferencias significativas (ANOVA p menor que 0.05), concluyendo que los adhesivos destinarios con solventes orgánicos, especialmente los basados en etanol, mejoran la capacidad de penetración.

The adhesive agents constitute an important and necessary requirement in the restoring dentistry, the dental adhesives with total- etching base their effectiveness on the formation of the hybrid layer and in the penetration in the dentin, it was evaluated different adhesive agents that use different solvents, as penetration vehicle, Ethanol (Solo Bond, 3M); and water (One Coat Bond - COLTENE); for that which recently extracted human third 30 molars were selected, stored in water distilled 4 °C (recommendations of ISO TR 11405), which were divided in three groups of 10 pieces each one that you/they were assigned according to its solvent, group A: solvent ethanol, group B: acetone; group C: water, being carried out cavities class II that were restored later on with compound resin, (Tetric Ceram - vivadent). Of these preparations sheets were obtained, that were treated with HCL, NAOCL stops this way to expose the continuations of resin and then to be observed by that if significant differences exist (ANOVA p minor that 0.05), concluding that the dentin bonding with organic solvents, especially those based on ethanol improve the penetration capacity.