Influence of Sealer and Light-Curing Units on Push-Out Bond Strength Of Composite Resin to Weakened Roots

Influence of different endodontic sealers on bond strength of fiber posts to weakened roots after resin restoration

OBJECTIVES

To assess the influence of different sealers used in root canal filling, in terms of bond strength (BS) to dentin, after restoration of weakened roots using resin composite (RC) and fiber posts.

MATERIAL AND METHODS

Roots of 39 maxillary incisors were used. After root canal preparation, root dentin was flared to produce a space between fiber post and root canal walls. The root canals were randomly distributed into three groups (n = 13), according to the sealer used: Endofill, AH Plus, and Acroseal. After removing the filling material to a depth of 12 mm, the flared roots were adhesively restored using RC. Posts were cemented and, after 24 h, roots were sectioned transversely producing 1-mm-thick slices. The slices from 30 roots were used for push-out test, and failure modes were noted. The remaining slices were analyzed by scanning electron microscopy (SEM).

RESULTS

Statistical analysis by 2-way ANOVA showed a significant difference among sealers (p = 0.001) and among root regions (p < 0.001). The BS mean of Endofill was lower and significantly different from the others. Overall, the coronal region presented higher BS mean values, followed by the middle and apical regions of the reinforced roots. The most frequent failure type was the adhesive failure between RC and dentin. SEM analysis showed the formation of a hybrid layer and many tags in the coronal and middle regions, while the apical region exhibited remnants of the endodontic sealers in all groups.

CONCLUSIONS

AH Plus and Acroseal sealer groups presented similar results, and the Endofill sealer negatively affected the BS of fiber post to restored root dentin.

CLINICAL RELEVANCE

Weakened dentin walls are often found in teeth undergoing endodontic treatment, so the sealer used must allow or at least not interfere the bonding between restorative materials and root dentin.

Performance of Multiple Light-curing Units used by Dental Students

Aim:

To investigate the performance of multiple Light-curing Units (LCUs) of different manufacturers used in a dental student clinical setting.

Background:

Manufacturers claim that the irradiance values of the LCUs stay stable over time. However, this may not be accurate among the different units.

Objective:

This study investigated the performance in terms of the irradiance, radiant exposure, and DOC of multiple LCUs of different types used in a dental student clinical setting.

Methods:

Four different LCU were investigated (n=5 units/LCU manufacturer): three Light-Emitting-Diodes (LED) units (Demi Ultra, Mini LED, and E-Morlit) and one quartz-tungsten-halogen (QTH) (PolyluxII). Irradiance and radiant exposure were collected [Managing Accurate Resin Curing-Patient Simulator (MARC-PS)](n=5 readings/unit/tooth). Depth of Cure (DOC) was performed (ISO 4049:2009standards) using a micro-hybrid composite (n=5/unit). Data were analyzed using Kruskal-Wallis and ANOVA followed by Student-Newman-Keuls and Tukey post hoc methods, respectively (α=0.05).

Results:

Using the MARC-PS anterior and posterior teeth sensors, respectively, the mean irradiance for Demi Ultra was (1625.7±38.8) and (1250.4±25.2); Mini LED (1381.1±37.8) and (1058.1±27.3); E-Morlit (1831.1±294.7) and (1545.2±176.0); and Polylux II (932.4±368.5) and (840.4±353.4)mW/cm2. The radiant exposure range was 16-38 J/cm2 for all LCUs. LCUs’ mean DOC ranged from 2.9 to 3.1 mm. Significant differences in irradiance and radiant exposure values were detected among the multiple units and manufacturers. Significant differences in DOC values among the Demi Ultra and Polylux II units were detected. DOC met the standards except for onePolylux II unit.

Conclusion:

The irradiance and radiant exposure values were not the same among the different units, regardless of the manufacturers’ claim of the irradiance values stability over time. Polymerization was not compromised except for one QTH unit per the DOC measurements. Itis highly recommended to closely monitor LCUs used in dental student clinical areas due to the high demand in this type of setting.

Endodontic sealers and post-endodontic waiting time affect the bond strength of the fiber posts

Abstract Introduction The resistance adhesive of a fiber post can be affected by several factors, such as the endodontic sealer and post-endodontic waiting time. Objective The aim of this study was to evaluate the effect of different endodontic sealers and two different post-endodontic waiting times on the bond strength of fiber posts. Material and method Seventy-two bovine teeth were endodontically treated and filled using three endodontic sealers: eugenol-based, epoxy resin-based, or mineral trioxide aggregate-based. The specimens were stored at 37°C for 24 hours or for 30 months. After the respective storage times, the root canals were prepared for luting fiber posts using RelyX U200. Push-out tests and analysis of failures were performed. The push-out data were analyzed by two-way analysis of variance to compare the effects of the endodontic sealer and with the t-test to compare the effects of post-endodontic waiting time. Result The AH Plus sealer yielded the highest bond strength values at 30 months post-endodontics (11.26 Mpa) (p < 0.05), however no had difference with Endofill sealer at the same time. Endofill and MTA Fillapex sealers did not differ significantly in their effects, irrespective of the post-endodontic waiting time. Conclusion In conclusion, the endodontic sealer used and post-endodontic waiting time affect the adhesive resistance of fiber posts. The adhesion increases significantly when the fiber post is cemented 30 months after the root canal filling, while the adhesion is reduced when cementing immediately after root canal treatment, in particular for eugenol-based endodontic sealers.

An Evaluation of the Light Output from 22 Contemporary Light Curing Units

This study measured the radiant power (mW), irradiance (mW/cm2) and emission spectra (mW/cm2/nm) of 22 new, or almost new, light curing units (LCUs): - Alt Lux II, BioLux Standard, Bluephase G2, Curing Light XL 3000, Demetron LC, DX Turbo LED 1200, EC450, EC500, Emitter C, Emitter D, KON-LUX, LED 3M ESPE, Led Lux II, Optilight Color, Optilight Max, Optilux 501, Poly Wireless, Radii cal, Radii plus, TL-01, VALO Cordless. These LCUs were either monowave or multiple peak light emitting diode (LED) units or quartz-tungsten-halogen LCUs used in anterior and posterior teeth. The radiant power emitted by the LCUs was measured by a laboratory grade laser power meter. The tip area (cm²) of the LCUs was measured and used to calculate the irradiance from the measured radiant power source. The MARC-Patient Simulator (MARC-PS) with a laboratory grade spectrometer (USB4000, Ocean Optics) was used to measure the irradiance and emission spectrum from each LCU three times at the sensor located on the facial of the maxillary central incisors and then separately at the occlusal of a maxillary second molar. The minimum acceptable irradiance level was set as 500 mW/cm2. Irradiance data was analyzed using two-way ANOVA and the radiant power data was analyzed by one-way ANOVA followed by Tukey test (a=0.05). In general, the irradiance was reduced at the molar tooth for most LCUs. Only the Valo, Bluephase G2 and Radii Plus delivered an irradiance similar to the anterior and posterior sensors greater than 500 mW/cm2. KON-LUX, Altlux II, Biolux Standard, TL-01, Optilux 501, DX Turbo LED 1200 LCUs delivered lower irradiance values than the recommended one used in molar region, KON-LUX and Altlux II LCUs used at the maxillary incisors. Bluephase G2 and Optilight Max delivered the highest radiant power and KON-LUX, Altlux II and Biolux Standard delivered the lowest power. The emission spectrum from the various monowave LED LCUs varied greatly. The multi-peak LCUs delivered similar emission spectra to both sensors.