Because there are several ways to cement glass-fiber posts (GFPs) into root canals, there is no consensus on the best strategy to achieve high bond strengths. A systematic review was conducted to determine if there is difference in bond strength to dentin between regular and self-adhesive resin cements and to verify the influence of several variables on the retention of GFPs. This report followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. In vitro studies that investigated the bond strength of GFPs luted with self-adhesive and regular resin cements were selected. Searches were carried out in the PubMed and Scopus databases. No publication year or language limit was used, and the last search was done in October 2012. A global comparison was performed between self-adhesive and regular resin cements. Two subgroup analyses were performed: 1) Self-adhesive × Regular resin cement + Etch-and-rinse adhesive and 2) Self-adhesive × Regular resin cement + Self-etch adhesive. The analyses were carried out using fixed-effect and random-effects models. The results showed heterogeneity in all comparisons, and higher bond strength to dentin was identified for self-adhesive cements. Although the articles included in this meta-analysis showed high heterogeneity and high risk of bias, the in vitro literature seems to suggest that use of self-adhesive resin cement could improve the retention of GFPs into root canals.

The role of resin cement on bond strength of glass-fiber posts luted into root canals: a systematic review and meta-analysis of in vitro studies.

Restorative dental materials

This study aimed to identify factors that can affect the retention of glass fiber posts to intra-radicular dentin based on in vitro studies that compared the bond strength (BS) of GFPs cemented with resin cements. Searches were carried out in PubMed and Scopus until December 2013. Bond strength values and variables as type of tooth, presence of endodontic treatment, pretreatment of the post, type of bonding agent (if present), type of cement and mode of cement application were extracted from the 34 included studies. A linear regression model was used to evaluate the influence of these parameters on BS. The presence of endodontic treatment decreased the BS values in 22.7% considering the pooled data (p = 0.013). For regular cement, cleaning the post increased BS when compared to silane application without cleaning (p = 0.032), considering cleaning as ethanol, air abrasion, or phosphoric acid application. Applying the cement around the post and into root canal decreased the resistance compared to only around the post (p = 0.02) or only into root canal (p = 0.041), on the other hand, no difference was found for self-adhesive resin cement for the same comparisons (p = 0.858 and p = 0.067). Endodontic treatment, method of cement application, and post pretreatment are factors that might significantly affect the retention of glass-fiber posts into root canals mainly when cemented with regular resin cement. Self-adhesive resin cements were found to be less technique-sensitive to luting procedures as compared with regular resin cements.

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A systematic review of factors associated with the retention of glass fiber posts

The Role of Resin Cement on Bond Strength of Glass-fiber Posts Luted Into Root Canals: A Systematic Review and Meta- analysis of In Vitro Studies R Sarkis-OnofreJA SkupienMS Cenci RR MoraesT Pereira-Cenci

The aim of this paper is to perform optimization of photopolymerization process of dental composites in order to obtain maximum hardness. Samples (5 mm diameter; 2, 3 and 4 mm thickness) were made of Universal Composite (UC), Bulk fill Composite (BC) and Flowable Composite (FC). Light curing of specimens was performed with 600, 1000 and 1500 mW/cm2 light intensity and an irradiation time of 20, 40 and 60 s. Vickers microhardness on the top and bottom surfaces of samples was measured. Optimization was carried out via regression analysis using QStatLab software. Photopolymerization process parameters were calculated using a specially designed MatLab software-based algorithm. For all composites, regression models for hardness on top and bottom surfaces of composite layer were established. Layer thickness as well as hardness on top and bottom surfaces of each composite was calculated for 21 curing modes varying with light intensity and irradiation time. It was established that photopolymerization guidelines only of FC manufacturer guarantee the required hardness, while recommended regimes for UC and BC did not satisfy this requirement. Tables, containing recommended light curing regimes, were developed for three composite types, guaranteeing high hardness of composite restoration. They were designed to facilitate work of dentists in dental offices.

https://www.mdpi.com/2227-9717/9/5/779/pdf

Optimization of Photopolymerization Process of Dental Composites

The indirect adhesive procedures constitute recently a substantial portion of contemporary esthetic restorative treatments. The resin cements have been used to bond tooth substrate and restorative materials. Due to recently introduction of the self-bonding resin luting cement based on a new monomer, filler and initiation technology has become important to study the degree of conversion of these new materials. In the present work the polymerization reaction and the filler content of dual-cured dental resin cements were studied by means of infra-red spectroscopy (FT-IR) and thermogravimetry (TG). Twenty specimens were made in a metallic mold (8 mm diameter × 1 mm thick) from each of 2 cements, Panavia® F2.0 (Kuraray) and RelyX™ Unicem Applicap (3M/ESPE). Each specimen was cured with blue LED with power density of 500 mW/cm2 for 30 s. Immediately after curing, 24 and 48 h, and 7 days DC was determined. For each time interval 5 specimens were pulverized, pressed with KBr and analyzed with FT-IR. The TG measurements were performed in Netzsch TG 209 under oxygen atmosphere and heating rate of 10°C/min from 25 to 700°C. A two-way ANOVA showed DC (%) mean values statistically significance differences between two cements (p 0.05). The Relx-Y™ Unicem mean values were significantly higher than Panavia® F 2.0. The degree of conversion means values increasing with the storage time and the filler content showed similar for both resin cements.

Changes on degree of conversion of dual-cure luting light-cured with blue LED

The aim of this study was to evaluate the hardness of a dental composite resin submitted to temperature changes before photo-activation with two light-curing unite (LCUs) Five samples (4 mm in diameter and 2 mm in thickness) for each group were made with pre-cure temperatures of 37, 54, and 60°C The samples were photo-activated with a conventional quartz-tungsten-halogen (QTH) and blue LED LCUs during 40 s The hardness Vickers test (VHN) was performed on the top and bottom surfaces of the samples According to the interaction between light-curing unit and different pre-heating temperatures of composite resin, only the light-curing unit provided influences on the mean values of initial Vickers hardness The light-curing unit based on blue LED showed hardness mean values more homogeneous between the top and bottom surfaces The hardness mean values were not statistically significant difference for the pre-cure temperature used According to these results, the pre-heating of the composite resin provide no influence on Vickers hardness mean values, however the blue LED showed a cure more homogeneous than QTH LCU

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Influence of pre-heat treatment and different light-curing units on Vickers hardness of a microhybrid composite resin

The aim of this study was to determine the influence of three light-curing units, storage times and colors of the dental composite resin on the fluorescence. The specimens (diameter 10.0 ± 0.1 mm, thickness 1.0 ± 0.1 mm) were made using a stainless steel mold. The mold was filled with the microhybrid composite resin and a polyethylene film covered each side of the mold. After this, a glass slide was placed on the top of the mold. To standardize the top surface of the specimens a circular weight (1 kg) with an orifice to pass the light tip of the LCU was placed on the top surface and photo-activated during 40 s. Five specimens were made for each group. The groups were divided into 9 groups following the LCUs (one QTH and two LEDs), storage times (immediately after curing, 24 hours, 7 and 30 days) and colors (shades: A2E, A2D, and TC) of the composite resin. After photo-activation, the specimens were storage in artificial saliva during the storage times proposed to each group at 37°C and 100% humidity. The analysis of variance (ANOVA) and Tukey’s posthoc tests showed no significant difference between storage times (immediately, 24 hours and 30 days) (P > 0.05). The means of fluorescence had difference significant to color and light-curing unit used to all period of storage (P 0.05).

Influence of the light-curing unit, storage time and shade of a dental composite resin on the fluorescence

The aim of this study was to determine the effect of two light-curing units (QTH and LED) on microleakage of Class II composite resin restorations with dentin cavosurface margins. Twenty extracted mandibular first premolars, free of caries and fractures were prepared two vertical “slot” cavities in the occluso-mesial and -destal surfaces (2 mm buccal-lingually, 2 mm proximal-axially and cervical limit in enamel) and divided into 4 equal groups (n = 8): GI and GII: packable posterior composite light-activated with LED and QTH, respectively; GIII and GIV: micro-hybrid composite resin light-activated with LED and QTH, respectively. The composite resins were applied following the manufacturer’s instructions. After 24 h of water storage specimens were subjected to thermocycling for a total of 500 cycles at 5 and 55°C and the teeth were then sealed with impermeable material. Teeth were immersed in 0.5% Basic fuchsin during 24 h at room temperature, and zero to three levels of penetration score were attributed. The Mann-Whitney and Kruskal-Wallis tests showed significant statistically similar (P > 0.05) from GI to GII and GIII to GIV, which the GII (2.750) had the highest mean scores and the GIII and GIV (0.875) had lowest mean scores. The use of different light-curing units has no influence on marginal integrity of Class II composite resin restorations and the proprieties of composite resins are important to reduce the microleakage.

Effect of light-curing units on microleakage under dental composite resins

The purpose of this study was to evaluate the effectiveness of different light-curing units on the bond strength (push-out) of glass fiber posts in the different thirds of the root (cervical, middle and apical) with different adhesive luting resin systems (dual-cure total-etch; dual-cured and self-etch bonding system; and dual-cure self-adhesive cements), Disks of the samples (n = 144) were used, with approximately 1 mm of thickness of 48 bovine roots restored with glass fiber posts, that were luted with resin cements photo-activated by halogen LCU (QTH, Optilux 501) and blue LED (Ultraled), with power densities of 600 and 550 mW/cm2, respectively. A universal testing machine (MTS 810 Material Test System) was used with a 1 mm diameter steel rod at cross-head speed of 0.5 mm/min until post extrusion, with load cell of 50 kg, for evaluation of the push-out strength in the different thirds of each sample. The push-out strength values in kgf were converted to MPa and analyzed through Analysis of Variance and Tukey’s test, at significance level of 5%. The results showed that there were no statistical differences between the QTH and LED LCUs. The self-adhesive resin cement had lower values of retention. The total-etch and self-adhesive system resin cements seem to be a possible alternative for glass fiber posts cementation into the radicular canal and the LED LCU can be applied as an alternative to halogen light on photo-activation of dual-cured resin cements.

S. T. Porto-Neto

Papers

Changes on degree of conversion of dual-cure luting light-cured with blue LED

Influence of pre-heat treatment and different light-curing units on Vickers hardness of a microhybrid composite resin

Influence of the light-curing unit, storage time and shade of a dental composite resin on the fluorescence

Effect of light-curing units on microleakage under dental composite resins

Effect of light-curing units on push-out fiber post bond strength in root canal dentin