Laura Ceballos

Bonding to Er-YAG-laser-treated dentin

Er-YAG laser irradiation has been claimed to improve the adhesive properties of dentin. We tested the hypothesis that dentin adhesion is affected by Er-YAG laser conditioning. Superficial or deep dentin from human molars was: (a) acid-etched with 35% H3PO4; (b) irradiated with an Er-YAG laser (KaVo) at 2 Hz and 180 mJ, with water-cooling; and (c) laser- and acid-etched. Single Bond (3M ESPE) and Z100 composite (3M ESPE) were bonded to the prepared surfaces. After storage, specimens were tested in shear to failure. Bonded interfaces were demineralized in EDTA and processed for transmission electron microscopy. Two-way ANOVA revealed that conditioning treatment and interaction between treatment and dentin depth significantly influenced shear bond strength results. Acid-etching alone yielded shear bond strength values that were significantly higher than those achieved with laser ablation alone, or in combination with acid-etching. The Er-YAG laser created a laser-modified layer that adversely affects adhesion to dentin, so it does not constitute an alternative bonding strategy to conventional acid etching.

Microleakage of composite restorations after acid or Er-YAG laser cavity treatments

OBJECTIVES The purpose of this study was to compare microleakage of Class V restorations following acid, laser or laser and acid treatment of cavity walls. METHODS Standardized lingual and buccal Class V preparations were made in 18 human extracted third molars. The preparations were randomly assigned to three equal groups (n=12). Group 1: cavities were treated with 35% phosphoric acid. Group 2: cavities were irradiated with an Er-YAG laser at 2Hz and 250mJ on dentin and 300mJ on enamel, with water cooling. Group 3: cavities were irradiated with the laser before acid etching. Scotchbond 1 Adhesive System and Z100 resin composite were used for restorations. The specimens were stored in water for 24h at 37 degrees C and thermally cycled (500x) between 6-60 degrees C. After 24h immersion in 0.5% basic fuchsin, dye penetration was recorded according to an ordinal scale. Data were analysed using non-parametric statistical tests (Kruskal-Wallis and Mann-Whitney). RESULTS On the occlusal walls, microleakage in acid etched cavities was significantly lower than that achieved after laser treatment (P<0.001) or after both treatments (P<0.05). On the gingival walls, no statistical differences were found. SIGNIFICANCE Laser irradiation of enamel is not a valid alternative to acid-etching pretreatment for resin composite materials adhesion. Acid etching alone gave the lowest microleakage at the occlusal margin. No differences were found for microleakage on gingival wall, although lased dentin surfaces presented several characteristics that appear to be advantageous for bonding.

Microhardness of different resin cement shades inside the root canal

Objectives: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material. Study Design: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X•Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core•X flow. All materials were applied according to manufacturers’ instructions and were all photopolymerized (Bluephase LED unit, Ivoclar Vivadent, 40s). After 24 hours, roots were transversally cut into 9 slices 1 mm thick from the coronal to apical extremes, three corresponding to each root third. Then, VHNs were recorded (100 gf, 30 s) on the resin luting materials along the adhesive interface in all sections. Data were analyzed by two-way ANOVA and SNK tests (α=0.05). Results: A significant influence on microhardness of resin luting material in their respective shades (p<0.001), root third (p<0.001) and interactions between them was detected (p<0.001). RelyX Unicem cement showed the highest microhardness values and Calibra the lowest, regardless of the shade selected. All resin luting materials tested exhibited a significantly higher microhardness in the cervical third. Conclusions: Microhardness of resin luting agents tested inside the canal is dependent on material brand and resin cement shade seems to be a less relevant factor. Microhardness decreased along the root canal, regardless of the shade selected. Key words:Cement shade, degree of conversion, dual-cured resin cements, fiber posts, microhardness, root thirds.

Propiedades mecánicas de resinas compuestas modificadas o no con poliácidos

espanolObjetivo: Determinar la resistencia a la flexion y el modulo de elasticidad de cinco resinas compuestas: Tetric Ceram, Ecusit, Spectrum TPH, Filtek Z-250, Degufill mineral; y dos resinas modificadas con poliacidos: Luxat e lonosit. Material y metodo: Se prepararon cinco muestras de cada material en un molde metalico rectangular (22x2x2 mm). Las muestras fueron polimerizadas, primero en el centro y luego en ambos extremos con una lampara de luz halogena y despues se conservaron en agua a 37° C durante 48 horas. Las muestras se pulieron para eliminar la capa de resina superficial y se sometieron al ensayo de flexion en 3 puntos con una maquina de traccion universal Instron con una velocidad de travesano de 1mm/min. Los resultados (MPa) fueron analizados mediante los tests de ANOVA y Student-Newman-Keuls (p EnglishThe aim of this study was to determine the flexural strength and modulus of elasticity of five resin composites: Tetric Ceram, Ecusit, Spectrum TPH, Filtek Z-250, Degufill mineral; and two polyacid-modified resin composites: Luxat e lonosit. Five rectangular specimens of each material were prepared (22x2x2 mm). They were light-cured, first in the middle and after in both extremes, by means of a visible-light curing unit. The specimens were stored in water at 37° C for 48 hours and ground to eliminate the resin layer inhibited by oxygen. Three-point bending test was performed in an universal testing machine (Instron) at a cross-head speed of 1mm/min. Results were expressed in MPa and analysed by ANOVA and Student-Newman-Keuls tests (p

Effect of adhesive application on the shear bond strength of flowable composite resins and APC plus to orthodontic molar tubes

Objectives: To evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic tubes to acid-etched human enamel when using different flowable composite resins and the APC Plus system (APC). Study design: One hundred metal tubes were bonded to human third molars, which were randomly divided into five groups: Tetric EvoFlow (TF); Wave mv Flow (W); Transbond Supreme LV (S); Transbond XT (XT); and APC. For each experimental group, half of the specimens were bonded in combination with Transbond XT adhesive. After 72 h, an SBS test was performed using a universal testing machine. Two-way analysis of variance (ANOVA) was run for multiple comparison tests and for comparing the mean SBS among the 10 subgroups to evaluate the effect of both the composite and the adhesive factors. Then, a Student-Newman-Keuls test was used for pairwise comparisons using the highest mean SBS group as reference. Adhesive Remnant Index scores were determined for the teeth after failure and compared by χ 2-test. Two representative molar surfaces from the 10 subgroups were assessed under scanning electron microscope. Results: The application of adhesive did not have a significant effect, but there was a marked tendency toward the influence of the factor composite on SBS. The mean SBS of tubes bonded with XT with adhesive was significantly higher than that of those bonded with APC with adhesive, TF with and without adhesive, and S with adhesive. Conclusion: Flowable composites and the APC system without intermediate bonding resin could be conveniently applied for orthodontic tube bonding.

Sorción y solubilidad de materiales formulados con resina

espanolEl objetivo de este estudio fue determinar la sorcion y solubilidad de cuatro resinas compuestas: Tetric Ceram (Vivadent), Ecusit (DMG), Degufill (Degussa) y Z-250 (3M-Espe); y dos resinas modificadas con poliacido: Luxat (DMG) e lonosit (DMG). Cinco especimenes circulares (15 mm x 0.85 mm) de cada material fueron preparados y pulidos con discos de carburo de silicio. Los especimenes fueron desecados en una estufa a 37o C hasta que se registro un peso constante (mo) y, posteriormente, se introdujeron en agua destilada a 37o C (m1). Una vez estabilizado su peso fueron desecados nuevamente, colocados en una campana al vacio (60oC, 24 h) y pesados por ultima vez (m2). El calculo de la sorcion (A) y solubilidad (S) se realizo mediante expresiones matematicas interrelacionadas: A = m1-m2/V; S = mo - m2 / V. Los tests de ANOVA y Student Newman Keuls mostraron diferencias en la sorcion y solubilidad segun el material estudiado (p EnglishThe aim of this study was to determine the sorption and solubility of four resin composites: Tetric Ceram (Vivadent), Ecusit (DMG), Degufill (Degussa) and Z-250 (3M-Espe); and two polyacid-modified resins: Luxat (DMG) and lonosit (DMG). Five discs (15 mm x 0.85 mm) of each material were prepared and ground wet to remove poorly polymerized suface layers. Discs were conditioned in a desiccator (37o C) until a constant weight was achieved using an analytic balance (mo); immersed in distilled water 37o C (m1) and finally into a vacuum oven (60o C, 24 h) and reweighted (m2). Sorption (A) and solubility (S) were calculated: A = m1 - m2 / V; S = mo - m2 / V. ANOVA and SNK tests showed statistical differences among the studied materials. lonosit showed the highest sorption and Tetric Ceram and Ecusit the lowest. Luxat presented higher sorption than Degufill, but both materials showed similar sorption values compared with Z-250. The higher solubility was obtained by lonosit. No statistical differences were found among resin composites and Luxat

Discrepancy of complete-arch titanium frameworks manufactured using selective laser melting and electron beam melting additive manufacturing technologies

Statement of problem. Titanium frameworks for implant‐supported prostheses can be additively manufactured using different powder‐based fusion technologies, including selective laser melting (SLM) and electron beam melting (EBM). Some manufacturers have developed a technique that combines the printing of the framework with the subsequent machining of the implant interface. Whether these technologies produce frameworks with acceptable accuracies is unclear. Purpose. The purpose of this in vitro study was to evaluate the discrepancy obtained from the digitizing procedures of the definitive cast, the implant‐prosthesis discrepancy, and the distortion of the manufacturing processes in the fabrication of titanium frameworks for implant‐supported complete‐arch prostheses manufactured using SLM and EBM additive manufacturing technologies. Material and methods. A completely edentulous mandibular definitive cast with 4 implant analogs and a replica of a screw‐retained interim restoration was obtained. A standard tessellation language (STL) file of the framework design was prepared using dental software (Exocad). Six frameworks were manufactured using either SLM (3D Systems) or EBM (Arcam) technologies. Discrepancy (&mgr;m) was measured at the x‐ (mesiodistal), y‐ (buccolingual), and z‐ (occlusogingival) axes by using the formula Symbol three times by best‐fit superimposure of the definitive cast STL file, the definitive cast titanium framework, and the framework STL file by using a coordinate measuring machine (CMM) controlled by software (Geomagic). The Kruskal‐Wallis and Mann–Whitney U statistical tests were used (&agr;=.05). Symbol. No caption available. Results. The digitizing procedures of the definitive cast showed a mean accuracy of 3 ±3 &mgr;m. Except for the z‐axis (P<.05), no significant differences were observed between the SLM and EBM technologies for implant prosthesis discrepancy for the x‐ or y‐axis (P>.05). The most favorable results were obtained in the z‐axis, representing the occlusogingival direction. Three‐dimensional discrepancy measurements in all comparisons ranged between (60 ±18 &mgr;m and 69 ±30 &mgr;m) and were not statistically significant (P>.05). The highest discrepancy was observed in the y‐axis (37 to 56 &mgr;m), followed by the x‐ (16 to 44 &mgr;m) and z‐ (6 to 11 &mgr;m) axes (P<.05). Conclusions. The titanium frameworks analyzed for a complete‐arch implant‐supported prosthesis fabricated using either the SLM or EBM additive technologies showed a clinically acceptable implant‐prosthesis discrepancy, where similar discrepancies on the x‐, y‐, and z‐axes were found between the additive manufacturing technologies. Both technologies showed comparable abilities to manufacture the STL file additively on the x‐, y‐, and z‐axes.

Antibacterial efficacy of several intracanal medicaments for endodontic therapy

The antibacterial efficacy of intracanal medicaments for 2 and 7 days, in open apex root canals contaminated with Enterococcus faecalis biofilms was compared. One hundred and thirty-eight standardized uniradicular human roots were inoculated with E. faecalis. Colony forming units (CFU) were recorded before and after medication. Samples were divided in two (2/7 days), and subdivided (n=8/group): triple antibiotic paste (TAP); double antibiotic paste (DAP); dental base paste (DBP), consisting of calcium hydroxide, propylene glycol and calcium carbonate; DBP+0.2% chlorhexidine (CHX); DBP+0.2% cetrimide (CTR); DBP+0.2% CHX+0.2% CTR; 2.5% sodium hypochlorite (NaOCl); and distilled water. At both periods TAP, DAP, DBP+0.2% CHX, DBP+0.2% CTR and DBP+0.2% CHX+0.2% CTR exhibited no growth (NG) of E. faecalis. Distilled water and 2.5% NaOCl obtained the lowest CFU reduction. No growth with DBP was reached only at 7 days. CHX and/or CTR pastes were as effective as DAP and TAP. A 2-day period provided an effective disinfection.

Effect of indirect composite treatment microtensile bond strength of self-adhesive resin cements

Background No specific indications about the pre-treatment of indirect composite restorations is provided by the manufacturers of most self-adhesive resin cements. The potential effect of silane treatment to the bond strength of the complete tooth/indirect restoration complex is not available.The aim of this study was to determine the contribution of different surface treatments on microtensile bond strength of composite overlays to dentin using several self-adhesive resin cements and a total-etch one. Material and Methods Composite overlays were fabricated and bonding surfaces were airborne-particle abraded and randomly assigned to two different surface treatments: no treatment or silane application (RelyX Ceramic Primer) followed by an adhesive (Adper Scotchbond 1 XT). Composite overlays were luted to flat dentin surfaces using the following self-adhesive resin cements: RelyX Unicem, G-Cem, Speedcem, Maxcem Elite or Smartcem2, and the total-etch resin cement RelyX ARC. After 24 h, bonded specimens were cut into sticks 1 mm thick and stressed in tension until failure. Two-way ANOVA and SNK tests were applied at α=0.05. Results Bond strength values were significantly influenced by the resin cement used (p<0.001). However, composite surface treatment and the interaction between the resin cement applied and surface treatment did not significantly affect dentin bond strength (p>0.05). All self-adhesive resin cements showed lower bond strength values than the total-etch RelyX ARC. Among self-adhesive resin cements, RelyX Unicem and G-Cem attained statistically higher bond strength values. Smartcem2 and Maxcem Elite exhibited 80-90% of pre-test failures. Conclusions The silane and adhesive application after indirect resin composite sandblasting did not improve the bond strength of dentin-composite overlay complex. Selection of the resin cement seems to be a more relevant factor when bonding indirect composites to dentin than its surface treatment. Key words:Bond strength, self-adhesive cement, silane, dentin, indirect composite.

Effect of low-concentration bleaching products on enamel bond strength at different elapsed times after bleaching treatment

This study evaluated the effects of several low-concentration bleaching products on microtensile bond strength (µTBS) to enamel at different elapsed times after the bleaching treatment. One hundred and fifty bovine incisors were divided into five groups: No treatment, 10% carbamide peroxide (Opalescence), 10% hydrogen peroxide (Opalescence Treswhite Supreme), 3% carbamide peroxide plus lactoperoxidase (WhiteKin), or 3% carbamide peroxide plus 2.7% carbamide peroxide (Clysiden Kit Express). All treatments lasted 4 weeks. After bleaching treatment or non-treatment, teeth were restored immediately, at 1, 3, 7, or 14 days after bleaching and submitted to µTBS test. Data were analyzed by ANOVA and Tukeys test (p<0.05). For WhiteKin and Clysiden, µTBS to enamel was significantly reduced immediately, at 1, 3 and 7 days after bleaching. At 14 days after bleaching, similar µTBS values were obtained regardless of bleaching product. Therefore, while over-the-counter (OTC) products might affect bond strength to enamel, this effect was no longer observed after 14 days.