Effects of dentin moisture on the push-out bond strength of a fiber post luted with different self-adhesive resin cements

Effect of dentin moisture on the adhesive properties of luting fiber posts using adhesive strategies

The purpose of this study was to evaluate the effect of dentin moisture (moist and dry) on the bonding of fiber posts to root dentin with different adhesive strategies (etch-and-rinse, self-etch, and self-adhesive). Seventy-two extracted single-rooted human teeth were endodontically treated and divided into six groups (n = 12) according to the moisture of dentin surface and adhesive systems as follows: a) etch-and-rinse/moist, b) etch-and-rinse/dry, c) self-etch/moist, d) self-etch/dry, e) self-adhesive/moist, and 6) self-adhesive/dry. The specimens were sectioned into six slices for push-out bond strength (BS), nanoleakage (NL) by SEM, and Vickers microhardness (VHN) of the resin cement. A universal testing machine (AG-I, Shimadzu Autograph) was used at a crosshead speed of 0.5 mm/min until post extrusion, with a load cell of 50 kg for evaluation of the push-out strength. Data on BS, NL, and VHN were evaluated by two-way ANOVA and Tukey's test (α = 0.05). Dentin moisture as the main factor was not significantly different for the push-out test. However, higher BS values can be observed for the etch-and-rinse group. A lower percentage of NL was found in the dry dentin groups. The moisture pattern was not significant in the hardness values for the pre-etching groups. Additional moisture did not increase the evaluated properties.

Influence of different intraradicular chemical pretreatments on the bond strength of adhesive interface between dentine and fiber post cements: A systematic review and network meta-analysis

Systematic review and network meta-analyses were performed to answer the question: Do intraradicular chemical pretreatments affect the bond strength of the adhesive interface between dentine and fiber post cements? A literature search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, and Cochrane Library in October 2018 (updated September 2021). In vitro studies that compared the bond strength assessed by push-out tests following at least two dentine chemical treatments prior to fiber post cementation were included. Risk of bias was evaluated. A random-effects Bayesian-mixed treatment comparison model was used to compare push-out bond strength of different chemical pretreatments. SUCRA (surface area under the cumulative ranking) analysis was performed to rank the pretreatments. After removing duplicates and screening titles and abstracts, 61 studies remained. SUCRA analysis showed that the best bond strength values for self-etch, etch-and-rinse, and self-adhesive cements were ethyl acetate (SUCRA: 99.8%), low concentration NaOCl (SUCRA: 83.4%), and grape seed extract (SUCRA: 97.6%), respectively. According to the SUCRA rankings, ethanol was in a good position for all adhesive strategies (SUCRA: 78.6%). The use of chemical pretreatments in intraradicular dentine of endodontically treated teeth depends on the adhesive and cementation strategy. The pretreatment generally associated with the highest bond strength was ethanol.

Postspace pretreatment with 17% ethylenediamine tetraacetic acid, 7% maleic acid, and 1% phytic acid on bond strength of fiber posts luted with a self-adhesive resin cement

Context:

Pretreatment of radicular dentin with chelating agents improves the bond strength of fiber-posts luted with a self-adhesive resin cement.

Aims:

The aim of this study was to assess the effects of the three chelating agents as final rinse of the postspace on bond strength of fiber posts luted with a self-adhesive resin cement.

Settings and Design:

This is an in vitro laboratory study.

Materials and Methods:

Forty-five mandibular premolars were prepared using MTwo rotary system and irrigation was done with 2.5% sodium hypochlorite. Three groups of teeth samples were considered for postspace preparation and irrigated with different solutions: Group 1: 17% ethylenediamine tetraacetic acid (EDTA); Group 2: 7% Maleic acid; Group 3: 1% Phytic acid. This was followed by the luting the posts with RelyX U200. After a week, from each sample, 2 mm thick slices were obtained from each third of the root and subjected to push-out bond strength testing.

Statistical Analysis Used:

One-way analysis of variance and Bonferroni's Post hoc analysis was used for assessing the results. The statistical significance level was set at P < 0.05.

Results:

Bond strength values were improved with maleic acid and phytic acid pretreatment with slight or no significant difference between these groups. A final rinse of postspace with EDTA significantly reduced the bond strength.

Conclusions:

Maleic acid (7%) pretreatment of postspace improved the adhesion of fiber posts luted with a self-adhesive resin cement.

Development and characterization of biological bovine dentin posts

This study aimed at evaluating the use of biological dentin post (BDP), achieved by milling bovine root, through the analyses of mechanical and optical properties. BDPs were compared to a glass fiber post (GFP) in the following tests (n = 10): a) elastic modulus (E) and flexural resistance (σ) by three point bending test; b) fracture resistance (FR) by compressive load at 45° and failure pattern; c) light transmitting (LT) ability and their influence on the resin cement's degree of conversion (DC%); d) bond strength (BS) by push-out test and failure pattern. Bovine teeth were decoronated and root length was standardized at 14 mm. The canals were prepared and irrigated with 2.5% NaOCl. GFP's surface was conditioned by 1 min immersion in 24% H₂O₂ solution before silanization. After root embedment, the root canal walls and the BDP's surface were hybridized (H₃PO₄ 37% + self-cured adhesive) for FR and DC% analyses. Posts were fixed into the root canals using a conventional dual resin cement. For BS test, both posts were luted using the conventional and the self-adhesive cementation. A universal testing machine (EMIC DL2000; 1 mm/min) was employed for the mechanical tests (E, σ, FR and BS). For the LT analysis, opaque polyethylene discs were transfixed by the posts, leaving 10 mm of the posts' apical section for measurements. Posts' cervical portion was irradiated (800 mW/cm²) and a spectrometer recorded the number of photons transmitted to previously chosen lateral post regions and at the apical tip. The resin cement DC% was evaluated in several sites of the cement film. After normal distribution were checked (Shapiro-Wilk test), data were submitted to ANOVA (5%) and Scheffe post-hoc test (5%). Results showed that: a) E: BDP > GFP; b) σ: BDP < GFP; c) RF: BDP < GFP; d) LT could not be observed for BDP. For GFPs, the greatest number of photons was observed at the post apical tip. An exponential decay was observed from the cervical to the apical post region; e) resin cement DC% was statistically similar at all points of measurements for both posts; and, f) BS: BDP = GFP, regardless the adhesive protocol used. It was concluded that: a) teeth restored with BDP exhibited lower fracture resistance than those restored with GFP; b) resin cement DC% was not influenced by the light transmitting ability of the post; c) the retention provided by the BDP was similar to the one provided by GFP, independently of the luting protocol.

Evaluation of the influence of time and concentration of sodium hypochlorite on the bond strength of glass fibre post

This study evaluated the effect of time and concentrations of sodium hypochlorite on the bond strength of a glass fibre post cemented in a root canal with resin cement. A total of 45 single-rooted extracted human teeth were prepared with Protaper^® universal files, randomly allocated into nine groups and then subjected to 1% or 4% NaOCl for a period of 1 min or 2 min. Fibre posts were then bonded into the root canal, sectioned and the bond strength tested using a push-out test. A longer irrigation time resulted in a significant reduction (P < 0.05) in bond strength, while a final additional irrigation with distilled water significantly reduced bond strength. The concentration of NaOCl did not significantly affect bond strength. Within the limitations of this study, it was observed that regardless of the concentration of NaOCl used, shorter irrigation times favoured better fibre post bonding.

Is the bonding of self-adhesive cement sensitive to root region and curing mode?

Objectives

To evaluate the influence of two curing techniques on the degree of conversion (DC) of resin cements and on bond strength (BS) of fiber posts in different regions of root dentin.

Material and Methods

Twenty single-rooted premolars were endodontically treated, and the post spaces were prepared. The roots were randomly divided into two groups (n=10), according to the activation mode of the resin cement RelyX™ U200 (3M ESPE Saint Paul, MN, USA): conventional (continuous activation mode) and soft-start activation mode (Ramp). The posts (WhitePost DC/FGM) were cemented according to the manufacturer’s recommendations and, after one week, the roots were cross-sectioned into six discs each of 1-mm thickness, and the cervical, medium, and apical thirds of the root canals were identified. The DC was evaluated under micro-Raman spectroscopy and the BS was evaluated by the push-out test. The data were analyzed by two-way ANOVA and Tukey’s test (α=0.05).

Results

Neither the activation mode nor the root regions affected the DC of the resin cement. Higher BS was achieved in the soft-start group (p=0.036); lower BS was observed in the apical third compared to the other root regions (p<0.001). Irrespective of the activation mode and root region, the mixed failure mode was the most prevalent.

Conclusion

The BS of fiber posts to root canals can be improved by soft-started polymerization. The DC was not affected by the curing mode.

A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation

AIM

To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement.

MATERIALS AND METHOD

The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons.

RESULTS

GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement.

CONCLUSION

It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation.