Bonding properties of universal adhesives to root canals prepared with different rotary instruments.

STATEMENT OF PROBLEM: Preparation of coronal dentin by using a diamond rotary instrument usually results in higher bond strength values than preparation with tungsten carbide burs, but information is lacking about the influence of rotary instruments on root canals before the bonding of fiber posts. PURPOSE: The purpose of this in vitro study was to evaluate the influence of the rotary instrument used to prepare the root canal and bonding strategies on the adhesion of fiber posts to root dentin with universal adhesive systems. MATERIAL AND METHODS: Human premolars were used and divided into 8 groups according to the combination of the following factors: rotary instrument (tungsten carbide bur versus diamond rotary instrument), cementation system (single-bond versus prime and bond), and bonding method (etch-and-rinse versus self-etch). Eight teeth per group were evaluated by push-out bond strength, 4 teeth were evaluated for nanoleakage by using scanning electron microscopy (SEM), and 2 teeth were evaluated for shape by SEM. Data for bond strength and nanoleakage for each cementation system were subjected to 2-way ANOVA and Tukey honest significant differences tests (α=.05). RESULTS: The highest bond strength values were observed for preparation using a diamond rotary instrument for both cementation systems. For prime and bond, the highest bond strength values were observed with the self-etch adhesion strategy, and the self-etch strategy was better for the single-bond; and the self-etch strategy was better than etch-and-rinse just after the use of a diamond instrument. In relation to nanoleakage for the cementation system, the prime and bond had the lowest values for groups using a diamond instrument and self-etch strategy. For the single bond, the adhesion strategy did not influence nanoleakage, but the rotary instrument did, with diamond rotary instruments resulting in lower values. SEM analyses showed a greater number of unobliterated tubules in the self-etch mode and a more regular surface when prepared with a diamond rotary. CONCLUSIONS: To improve the adhesion of fiber posts to root canal, a diamond rotary instrument should be used, and generally, universal adhesive systems must be used in self-etch mode.

New Single-bottle Ceramic Primer: 6-month Case Report and Laboratory Performance.

INTRODUCTION: This article presents a 6-month case report and an in vitro evaluation of the performance of the new self-etching glass-ceramic monobond etch and prime (MEP) when applied in a lithium disilicate (LD). The MEP contains in the same bottle, along with acid conditioner and silanes. This simplifies the bonding procedures by reducing not only the number of steps, but also the working time. A 42-year-old female patient sought for esthetic treatment, and the main complaint was the darkened appearance of the upper lateral incisor. The esthetic treatment includes dental bleaching and gingivectomy, all-ceramic zirco-nia crowns, and all-ceramic crown and laminate veneer LD. After 6 months of esthetic treatment, marginal staining, gap, or chip fracturing damaging margins after sharp explorer in the margins was not observed. Furthermore, the inferior etching pattern of MEP was compared with traditional hydrofluoric acid (HF) conditioning. The microshear bond strength to the intaglio surface of LD was statistically similar when HF was compared with MEP. This new self-etching glass-ceramic showed good in vitro and 6 months clinical results in this case report. Future long-term clinical studies with more clinical case need to be done to confirm the performance of the use of this new conditioner. CLINICAL SIGNIFICANCE: The use of a new self-etching glass-ceramic showed a good in vitro and 6 months clinical results. This new product can be an easy, simple, and alternative approach for esthetics bonding procedure.

In vitro analysis of bond strength of self-etching adhesives applied on superficial and deep dentin.

The purpose of this study was to evaluate the bond strength of three adhesive systems to superficial and deep dentine using the microtensile bond strength test (microTBS). The occlusal enamel of thirty human third molars was removed to expose a flat surface of superficial or deep dentin. For each type of surface, the test specimens were randomly divided into three groups which underwent the application of a conventional two-step adhesive system [Single Bond (SB)] as the control group (n=10), a two-bottle self-etching system [One Coat SE Bond (OCSE)] (n=10) and a one bottle one-step system [Clearfil S3 Bond (CFS3)] (n=10). Adhesives were applied, a 5-mm high "crown" as built-up with resin composite Z250 (3M) and the specimens with a cross-sectional area of 0.7 +/- 0.1 mm2 were tested in tension (0.5 mm/min). Four fractured sticks from each tooth were randomly selected and the dentin side was gently abraded with a 1200-grit SiC paper etched with 35% phosphoric acid for 15 s and air dried. SEM micrographs at 70X and 2400X magnification were taken using scanning electron microscopy (SEM) to calculate the area of tubular dentin (ATD) and tubular density (TD) with Image Pro Plus 5. Two-way ANOVA (dentin depth-adhesive) showed higher bond strength values for SB. However the values did not depend on dentin depth. Linear regression showed a significant relationship between bond strength and area of intertubular dentin for SB (p = 0.004), and a significant inverse relationship between tubular density and bond strength for CFS3 (p = 0.009). OCSE exhibited a tendency that was similar to SB and opposite to CFS3, but was not statistically significant. The conventional two-step adhesive had higher bond strength values. The use of digital image analysis facilitates the manipulation of data and contributes to the interpretation of the behavior of new adhesive systems.

Effect of exposure time on curing efficiency of polymerizing units equipped with light-emitting diodes.

A study was conducted to evaluate the top and bottom hardness of two composites cured using polymerizing units equipped with light-emitting diodes [LED] (LEDemetron; Elipar FreeLight, Coltolux LED) and one quartz-tungsten halogen device [QTH] (Optilux 501) under different exposure times (20, 40 and 60 sec). A matrix mold 5 mm in diameter and 2 mm in depth was made to obtain five disc-shaped specimens for each experimental group. The specimens were cured by one of the light-curing units (LCUs) for 20, 40 or 60 sec, and the hardness was measured with a Vickers hardness-measuring instrument (50 g/30 sec). Data were subjected to three-way ANOVA and Tukey's test (alpha = 0.05). LED LCUs were as effective as the QTH device for curing both composites. A significant increase in the microhardness values were observed for all light LCUs when the exposure time was changed from 20 sec to 40 sec. The Z250 composite showed hardness values that were usually higher than those of the Charisma composite under similar experimental conditions. LED LCUs are as efficient for curing composites as the QTH device as long as an exposure time of 40 sec or higher is employed. An exposure time of 40 sec is required to provide composites with a uniform and high Knoop hardness when LED light-curing units are employed.