Efficacy of different adhesive techniques on bonding to root canal walls: an SEM investigation

Effects of Etching Time and Ethanol Wet Bonding on Bond Strength and Metalloproteinase Activity in Radicular Dentin

(1) Background: The objective of this in vitro study was to evaluate the impact of different etching times and ethanol pre-treatments on the immediate bond strength of a hydrophilic multi-mode universal adhesive (Clearfil Universal Bond Quick, Kuraray, UBQ) and on the consequent gelatinolytic activity of metalloproteinases (MMPs) on radicular dentin. (2) Methods: Sixty single-root teeth were selected and divided into four groups according to the adhesive protocol applied for fiber post cementation: (G1) 15 s H3PO4 application + UBQ; (G2) 30 s H3PO4 application + UBQ; (G3) 15 s H3PO4 application + ethanol pre-treatment + UBQ; (G4) 30 s H3PO4 + ethanol pre-treatment + UBQ. After adhesive procedures, fiber posts were luted into the post space with a dual-curing cement (DC Core, Kuraray) and light-cured for 40 s. To perform the push-out test and nanoleakage analyses for both coronal end apical areas, 1 mm slices were prepared, following a 24 h storage period in artificial saliva. Additionally, an in situ zymographic assay was conducted to explore endogenous MMP activity within the radicular layer. Results were statistically analyzed with ANOVA and Tukey post hoc tests. Statistical significance was set at p < 0.05. (3) Result: ANOVA revealed a statistically significant difference in push-out bond strength related to the pre-treatment variable but did not highlight any significance of etching time. Specimens pre-treated with ethanol wet bond application showed higher bond strength (p < 0.01). In situ zymography quantification analyses revealed that all tested groups, independently of etching time end ethanol pre-treatment, activated MMP gelatinolytic activity. A significant increase in MMP activity was detected for the 30 s etching time. However, ETOH pre-treatment significantly reduced MMP activity within the adhesive interface (p < 0.01). (4) Conclusions: The tested adhesive showed similar results regardless of the etching time protocol. The gelatinolytic activity of MMPs was observed in all the groups. Further investigations and extended follow-ups are required to validate the results of the present study in vivo.

Scientific mapping of hotspots and trends of post and core research based on the Web of Science: A bibliometric analysis

Statement of problem

Post and core (PC) restoration has been widely used to restore endodontically treated teeth. Nevertheless, bibliometric studies focusing on PC research are lacking.

Purpose

The purpose of this bibliometric analysis was to review the general situation and determine the research direction of PC restoration by means of visualization, including the time development, countries, institutions, authors, journals, research categories, and the information of references with the strongest citation burst.

Material and methods

The search was carried out within the topic field of the Web of Science (WoS) database. CiteSpace, VOSviewer, and R language were used to analyze the literature. Bibliometric indicators in terms of title, keyword, reference, publication time, institution, country and citation information were analyzed.

Results

Between 1966 and 2022, dental research on PC trended upward, especially in 2011 and up to 2022. Scholars in Brazil, the United States, and Italy actively participated in PC research. The country that published the most was Brazil. Italy both ranked first in the H-index and average citations per item and had cooperative relations with several countries. The United States ranked first in the world in total citation count. The University of Siena published the most articles. The Journal of Prosthetic Dentistry (JPD) was the major contributing journal. The top three authors in this field were Ferrari M, Goracci C and Naumann M. The largest cooperative network of authors consisted of four Italian scholars. There were six main clusters of research topics on PC through CiteSpace co-citations. In addition, CiteSpace co-citations, CiteSpace Burst detection and VOSviewer keyword analysis showed the most important research interests, such as bond strength, fiber post, fracture resistance, and finite element analysis. Photodynamic therapy is the latest research hotspot. Finally, there were the top 25 references with the strongest citation bursts, which mainly focused on four aspects, namely, studies related to fiber posts, PC bonding strength, finite element analysis, and residual teeth and the ferrule effect.

Conclusions

This bibliometric analysis provides a comprehensive overview of PC research, including the research time, country, institution, author, journal, article clustering, article keywords, and important literature analysis, so that researchers can have a clear understanding of the research situation in this field.

Outcome of chairside CAD/CAM ceramic restorations on endodontically treated posterior teeth: a prospective study

OBJECTIVE

The aim of this study was to evaluate the outcome and risk factors for chairside CAD/CAM full cusp coverage restorations on endodontically treated posterior teeth after 3 years of follow-up.

METHODS

A total of 245 endodontically treated posterior teeth of 224 patients were included and restored with CAD/CAM full cusp coverage all-ceramic restorations according to a standardized protocol. Patients were recalled after treatments 1 to 3 years and underwent clinical and radiological examinations. At recall, modified FDI criteria were used to determine treatment outcomes by 2 evaluators. Success was determined when FDI scores were 1-2, and failure was indicated when FDI scores were 5. Logistic regression analysis was performed to evaluate potential risk factors.

RESULTS

A total of 183 patients presented at recall, and the clinical outcomes of 201 teeth were analyzed with a recall rate of 82.0% for teeth and 81.7% for patients after 1-3 years of follow-up.185 of 201 teeth were found to have FDI scores of 1-2, and the success rate was 92%. No teeth were extracted during the follow-up period. Fourteen failed cases with an FDI score of 5 presented restoration dislocation, fracture of restoration or/and tooth. Logistic regression analysis revealed that oral parafunction (OR 2.281, 95% CI 2.2 ~ 47.5, P value 0.01) was a risk factor for success rate.

CONCLUSION

Chairside CAD/CAM all-ceramic full cusp coverage restoration was (could be) a promising alternative for restoring endodontically treated posterior teeth.

Transmission of radiant light energy through the sides of fiber posts

OBJECTIVES

Resin cements are light polymerized, but the light may not reach all areas of root canals. The purpose of this study was to determine the best predictor of transmitted light radiant exposure (TLRE) from posts' sides.

MATERIALS AND METHODS

Fiber posts were placed in a custom-made apparatus and advanced by 1-mm increments. The LED curing probe tip was activated for 40 s on the coronal end of the post. The TLRE was measured with an LED radiometer detector positioned on the side of the post exposed by an opening in the apparatus. Hierarchical multiple linear regression analysis was performed.

RESULTS

Post system explained an additional 23.62% of the variation in TRLE. Adding actual post diameter explained an additional 62.64% of the variation in TRLE. While adding post length explained an additional 0.67%. Changing post system from FiberKleer to Postec Plus will decrease the mean value of TRLE by 4.90 units on average. Also, a one-unit increase of actual post diameter and length will decrease the value of TRLE by 44.96 and 0.44 units respectively. The TLRE ranged from 46 to 290 mJ/cm² , which was between 0.73% and 6.63% of the original emanating light.

CONCLUSIONS

The changes in post system, posts' diameter and length can be used to predict the unit changes in TLRE on the side of a translucent fiber post. Emanating radiant exposure from the side of the post was lower than 6.63% of the exposure entering the post.

CLINICAL RELEVANCE

Fiber post diameter and length and post system can influence light radiant exposure transmitted from posts' sides, transmitting minimal radiant exposure, which can be increased by increasing curing duration.

Presence of microbrush remnants on the adhesion surface: A microscopical analysis

OBJECTIVES

the aim of this ex vivo report was to evaluate, on a microscopical analysis, the presence of microbrush remnants on in the adhesive surface in extracted teeth.

METHODS

Twenty extracted teeth were divided into four groups. Half of the teeth were prepared as Class I cavities, whereas the other half as Class II cavities, according to Black classification. The teeth were conditioned with primer and bonding, both applied with microbrushes. Each of these groups was divided into halves, and the two sub-groups received a polymerization process or not, respectively. The teeth were then analyzed by scanning electron microscopy working in environmental mode.

RESULTS

All of the analyzed surfaces (100%) showed the presence of residual bristles on the adhesion surface.

CONCLUSIONS

Microscopical analysis showed the presence of residual bristles in the 100% of the surfaces treated with Black Classes I and II cavities. Further studies are necessary to evaluate the influence of this factor on the adhesion strength and capacity.

CLINICAL SIGNIFICANCE

Clinician should be aware of the realistic possibility of the presence of bristles belonging to disposable applicators in the adhesive interface of Black's class I and II cavities. The impact of these remnants has still to be ascertained.

Comparing the bond strength of fiber post cementation in the root canal using pre- and co-curing procedures with the same self-etching bonding system

Background/purpose

Self-etching bonding systems are widely used in fiber post cementation. However, no clear guidelines are established for choosing pre- or co-curing procedures. We investigated the bond strength of fiber post cementation using pre-/co-curing methods in self-etching bonding systems and compared them with those of a self-adhesive system.

Materials and methods

Post spaces were prepared in 30 single-rooted premolars/canines, and the fiber posts were cemented in three ways (10 specimens per group): using a self-etching bonding system with either a pre-curing or simultaneous co-curing procedure (RelyX™ Ultimate; groups SE-pre and SE-co, respectively) and using a self-adhesive system (RelyX™ Unicem 2, group SA). Each specimen was embedded and sliced perpendicularly to the long axis into three 2.5-mm-thick sections. Microphotographs of the coronal and apical surfaces of each section were acquired, and push-out tests (1 mm/min) were performed. One-way analysis of variance was conducted on the data, followed by Tukey's honestly significant difference post hoc test.

Results

The bond strength in the whole root was not significantly different among the three groups. When independently evaluating each portion, group SE-co exhibited significantly lower coronal bond strength. The bond strength varied among root regions only in group SE-pre; the apical region had a significantly lower value.

Conclusion

No cementation method is superior in all portions. Regarding pre-curing methods, clinicians must caution the fit between the post and post space, which may be affected by the pre-polymerized bond layer. The co-curing method used in a larger coronal cement space contributes to the poor bond strength.

Endodontic Irrigants and Their Activation Efficacy on Cleansing Post-Space Root Canal Walls

The aim of this study was to evaluate the efficacy of activated irrigants (EDTA e NaOCL) during the cleansing of root walls, of the smear layer, of the debris, and gutta-percha after the preparation of the restorative space. Twenty single and multi-rooted (n = 20) have been collected. All samples were prepared by the same operator, using Nickel-titanium rotating instruments (Mtwo) through the Simultaneous Shaping Technique. The continuous-wave of condensation technique of obturation was used. To all specimens, the restorative space has been made, leaving 5 mm of apical gutta-percha, and postoperative periapical X-rays were performed. The samples were randomly divided into two groups: Group (A): cleansing of the root walls with ultrasonic activation of the irrigants (NEWTRON P5 XS; Satelec Acteon); Group (B): radicular walls wash without ultrasonic activation of endodontic irrigants (NaOCl 5.25% and EDTA 17%). Both dental sample groups were cut longitudinally with a low-speed saw (Isomet); the samples were observed by using a scanning electron microscope (Jeol, Jsm-6060LV) in order to evaluate: (1) the amount of debris/smear layer; (2) the mount of obstruction of dentinal tubules found in the two groups; and (3) evaluation of the presence of gutta-percha. Then, the other five samples each group (with and without ultrasonic activation) were prepared following the same protocol. Then, a universal bonding system (G-Praemio Bond, GC) and a layer of a flowable resin composite (Gaenial Flow, GC) were light-cured and used on top of the prepared root canal walls. The samples were cut in two pieces along the long axis of the root. Then, half sample teeth were kept in an acidic solution (37% HCl) for 48 h in order to completely dissolve dental structures and to have a direct view of resin tags formation under SEM. The other half was prepared to observe the adhesive interface under SEM. The amount of debris was not satisfactory in 9 out of 10 cases in Group B, while in Group A, which has been treated with ultrasounds, the result was either good or great in most of the samples. For the sample group treated with ultrasound, the tubules were evaluated as perfectly clean in 9 out of 10 cases, instead, the results are unsatisfactory for 9 out of 10 cases of group B not treated with ultrasound. Differences between Group A and B were statistically significant. With respect to the presence of debris and tubules obstruction treatment with ultrasonic activation, it offers with no doubt better results. When ultrasonic activation is used in combination with endodontic irrigants, a clean dentin substrate is be obtained for the adhesion of restorative materials, but in order to confirm the findings of this study, further in vivo trials are needed.

Effects of different bonding systems with various polymerization modes and root canal region on the bond strength of core build-up resin composite

Purpose The aim of this study was to clarify the effects of different bonding systems (BSs) with various polymerization modes and root canal regions on the bond strength of core build-up resin composite to dentin.Methods Post cavities were prepared in the roots of 54 bovine teeth. Three types of BS with various polymerization modes (light, chemical, and dual-cure) were applied to the walls of the cavities, which were subsequently filled with core build-up resin composite, and stored in 37°C water for 7 days. Each tooth was then sectioned perpendicular to the long axis of the tooth into 9-disk from the coronal to the apical side. Bond strengths were measured on two-thirds of the disks, while dye penetration was examined in the remaining third.Results Statistical analysis revealed significant differences between the bond strengths of BSs with different polymerization modes, indicating chemical-cured BS had higher bond strength than light-cured BS. The chemical-cured BS group showed cohesive failure in both resin composite and dentin regardless of the root canal region, while adhesive failure was observed in the coronal region for dual-cured BS and in the apical region for light-cured BS. Dye penetration was significantly more at the bonding interface at the apical region of the light-cured BS.Conclusions Chemical-cured BS displayed a greater bond strength than light-cured BS. Cohesive failure was observed in both core build-up resin and dentin, indicating that the integration of tooth structure with resin composite was effective for retaining the resin core and sealing the root canal.

Effects of different bonding systems with various polymerization modes and root canal region on the bond strength of core build-up resin composite

PURPOSE

The aim of this study was to clarify the effects of different bonding systems (BSs) with various polymerization modes and root canal regions on the bond strength of core build-up resin composite to dentin.

METHODS

Post cavities were prepared in the roots of 54 bovine teeth. Three types of BS with various polymerization modes (light, chemical, and dual-cure) were applied to the walls of the cavities, which were subsequently filled with core build-up resin composite, and stored in 37ºC water for 7 days. Each tooth was then sectioned perpendicular to the long axis of the tooth into 9-disk from the coronal to the apical side. Bond strengths were measured on two-thirds of the disks, while dye penetration was examined in the remaining third.

RESULTS

Statistical analysis revealed significant differences between the bond strengths of BSs with different polymerization modes, indicating chemical-cured BS had higher bond strength than light-cured BS. The chemical-cured BS group showed cohesive failure in both resin composite and dentin regardless of the root canal region, while adhesive failure was observed in the coronal region for dual-cured BS and in the apical region for light-cured BS. Dye penetration was significantly more at the bonding interface at the apical region of the light-cured BS.

CONCLUSIONS

Chemical-cured BS displayed a greater bond strength than light-cured BS. Cohesive failure was observed in both core build-up resin and dentin, indicating that the integration of tooth structure with resin composite was effective for retaining the resin core and sealing the root canal.

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.

Effect of different restorative crown design and materials on stress distribution in endodontically treated molars: a finite element analysis study

Background

The purposes of this simulation study were to evaluate the stresses in the roots of endodontically treated molars with extensive coronal tissue loss which were restored by endocrowns (all-in-one core and crown) and traditional crowns with post-cores, during masticatory simulation using finite element analysis.

Methods

A mesio-distal cross-section of a lower right first molar was digitized and used to create 2-dimensional models of the teeth and supporting tissue; different crown designs, viz., endocrown with 2 mm occlusal clearance, endocrown with 4 mm occlusal clearance and post-core crown; different crown materials, viz., zirconia (Zr) and lithia-disilicate reinforced glass ceramic (LDRGC), and different post and core materials, viz., glass fiber (GF), stainless steel (SS) and metal cast (MC). An axial load of 600 N was applied to the central fossa of occlusal surface.

Results

The stress distributions were similar between Zr and LDRGC for periodontal ligament and alveolar bone. The root canal inner wall maximum principal stresses of SS post (70.8 MPa) and MC post (71.4 MPa) were higher than that of GF post (36.0 MPa) and endocrown (2.4 MPa).

Conclusion

The endocrowns reduced stress concentration for the root canal inner wall in comparison with the conventional post-core crown. Molars restored with endocrowns are less prone to root fracture than those with posts.

Effect of Two Different Surface Treatments on Retention of Cosmopost with Two Different Core Materials

Objective

The objective of this study was to determine the effect of Cosmopost’s two different surface treatments (sandblasting and silica coating) on persistence to various core materials using push-out test set-up.

Material and Methods

A total of 30 Cosmoposts was used in this study. Cosmoposts were divided into three groups (10 samples each) according to the post-surface treatment received. Every category was additionally subdivided into two subgroups according to the type of core material (n = 5 samples). A specially designed copper mold was used for construction of different core materials with standardized dimensions around the posts, in such a way to ensure that the posts will be centralized. Surface roughness was estimated for all Cosmoposts, following different surface treatments using SEM. Cylindrical cores were fabricated of either composite resin or heat-pressed zirconia-containing glass-ceramic (IPS Empress Cosmo, Ivoclar Vivadent). Following the construction of different Core materials, samples were subjected to push-out test set-up to Evaluate the impact of various treatments on post/core bond strength. Data were collected, tabulated and statistically analyzed. SEM was performed on Cosmoposts following debonding of different post/core samples to determine their mode of failure.

Results

Results of push-out bond strength revealed that core material, surface treatment and the interaction between the two variables using Two-way ANOVA had a statistically significant effect on mean push-out bond strength. Regarding the effect of type of core material on Push-out bond strength, results showed that IPS Empress Cores showed statistically significant higher mean push-out bond strength to Cosmopost (36.4±9.7MPa) than composite cores (15.8±2.5 MPa).

Conclusion

Within the limitations of this study, direct heat-pressed ceramic core was more beneficial for zirconia post buildups, than Composite Cores, since they provided higher bond strength. Thanks to a double improvement: increase in fracture resistance and retentive capacity to post. Also, Tribochemical Silicacoating technique was proved to be more effective in Cosmopost treatments than sandblasting technique.

Bond strength of cemented fiber posts to teeth with simulated internal root resorption

Background

Teeth with internal root resorption (IRR) have guarded prognosis, considering that IRR defect could influence on the post bond strength. The aim of this study was to evaluate the bond strength and the bond interface between different glass fiber-reinforced posts (FRP) after cementation in teeth with simulated internal root resorption (IRR).

Material and Methods

Forty-five (45) human premolar roots with simulated IRR were embedded in acrylic resin blocks and cross-sectioned into two segments, enabling them to be re-approximated by screws. Intracanal medication was inserted for 15-days, removed by passive ultrasonic irrigation (PUI) and examined by stereomicroscopy. The push-out bond strength of two fiber reinforced composite posts (Rebilda Post - RP) and Rebilda Post GT – GT, (VOCO) were evaluated at the cervical and IRR regions (n = 20). And, the bonded interface between resin cement and root dentine was analysed by scanning electron microscopy (SEM).

Results

62.5% of IRR were not completely cleaned by PUI. Bond strength values at the cervical region (9.8 and 14.6 MPa) were higher than the IRR region (6.3 and 4.2 MPa). Micrographies showed bubbles in the cement and spaces in the bonded interface.

Conclusions

RP post showed better bond strength at the cervical region while GT had better bond strength at the IRR region.

Key words:Endodontics, root canal filling materials, root resorption, X-Ray microtomography.

Efficacy of phototherapy in the adhesive bonding of different dental posts to root dentin: A systematic review

BACKGROUND

The aim of the current systematic review was to evaluate the efficacy of phototherapy in the adhesive bonding of different dental posts to root dentin.

METHODS

The outline of this systematic review followed the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines. Searches in both electronic and manual literature were performed in the main databases 'MEDLINE' and 'EMBASE' up to March 2019 using the following terms: (Phototherapy) AND (push out test) AND (bond strength) AND (post) OR (fibre) OR (metal) AND (smear layer).

RESULTS

Six in-vitro studies were included and processed for data extraction. All studies incorporated the use of fiber posts. The mean shear bond strength for test group ranged from 2.23 to 15.17 MPa while mean shear bond strength for control group ranged from 2.93 to 9.38 MPa. The wavelengths of diode lasers ranged from 660 to 2940 nm (nm). Power was reported in 5 studies ranging from 0.075 W to 3 W. All studies compared shear bond strength of phototherapy in the adhesive bonding of different dental posts to root dentin. In all the included studies, greater bond strength achieved by phototherapy compared to nonirradiated group.

CONCLUSION

Within the limits, this study shows that the dentin to post bond strength was significantly enhanced by phototherapy.

Comparison of Self-Etching Ceramic Primer and Conventional Silanization to Bond Strength in Cementation of Fiber Reinforced Composite Post

Various mechanical and chemical surface treatments have been proposed to improve the retention of fiber-reinforced composite post (FRCP), but the results are still controversial. The bond strength and durability of a self-etching ceramic primer, which was recently released as an alternative to etching and silane, are not yet known. This study aimed to compare and evaluate the push-out bond strength of different surface treatments of FRCPs after an artificial aging procedure. Four groups (n = 10) were established to evaluated FRCP surface treatments (dentin adhesive bonding; silane and adhesive bonding; hydrofluoric acid, silane and adhesive bonding; and a self-etching ceramic primer). They were bonded with dual-curing rein cement (Multilink N) and stored in distilled water at 37 °C for 30 days, then thermal cycled for 7500 cycles. After being sectioned into 1 mm thickness, each coronal and apical part was evaluated for its the push-out bond strength by a universal testing machine. Each debonded specimen was observed by an optical microscope and divided according to the failure modes. The results showed that silane treatment significantly improved push-out bond strength, but the self-etching ceramic primer did not do so. Additional hydrofluoric acid treatment or the adhesive bonding agent alone did not significantly improve the retention of FRCPs. Cohesive failure of the luting material was found most frequently in all groups.

Effect of Load Cycling on the Fracture Strength/Mode of Teeth Restored with FRC Posts or a FRC Liner and a Resin Composite

The aim of the study was to comparatively evaluate the fracture strength and mode of root canal treated teeth restored with resin composites with and without posts. The lingual cusps of root canal treated first upper premolars (n = 10/group) were removed down to cervical enamel and restored with the following: group A: glass-fiber post (Glassix) followed by a particulate-filled composite resin (PFC, G-aenial posterior, 3 × 2 mm layers); group B: glass-fiber reinforced composite bulk fill liner (EverX posterior, 4 mm layer) with the PFC (2 mm layer). Specimens were immersed in H2O (1 w/37°C), then subjected to load cycling (50 N/0.2 Hz/200k cycles), and fractured under compressive loading. Failure mode was characterized by stereomicroscopy. Statistical analysis was performed by Mann-Whitney (load) and Chi-square (mode) at a = 0.05. No statistically significant differences (p = 0.273) were found in fracture load between median values of groups A (860 N) and B (1059 N). In group A, 60% of the specimens demonstrated catastrophic root fractures and 40% mixed crown fractures (tooth cusp and restoration), whereas in group B, no root fractures were found, and the failure modes were equally distributed between mixed fractures as above and fracture of the buccal cusp. These differences were statistically significant (p = 0.004). The combination of the glass-FRC bulk fill liner with the PFC diminished the catastrophic root fractures induced by FRC posts, at a similar or higher fracture load.

[Research progress in pulpless posterior tooth restored with ceramic onlay]

Minimal invasive restoration is a common technique in the restoration of pulpless posterior teeth. The development of bonding techniques and ceramic materials in recent years has increased the use of high-strength ceramic onlay in the restoration of endodontically treated posterior teeth because of its minimal invasiveness, improved aesthetics, and low requirement of mechanical retention. This study conducts a retrospective analysis on the material, tooth preparation, bonding, and clinical considerations of ceramic onlay in endodontically treated posterior tooth.

Effect of Root Canal Sealers on Bond Strength of Fiber Posts to Root Dentin Cemented after one Week or six Months

Eugenol-based root canal sealers (RCS) have been widely used by clinicians; however, their effect on resinous materials is still questionable. The objective of this study was to evaluate the influence of RCS at 1 week and 6 months' post obturation on the bond strength (BS) of glass fiber posts (GFP) to root dentin, using conventional and self-adhesive cementation systems (CS). The roots of 56 extracted human canines, were divided in eight groups (n=7) according to the combination of the following factors: RCS (with or without eugenol-Endofill and Sealer 26, respectively), storage period post obturation and prior GFP cementation (1 week and 6 months) and cementation systems (Variolink II - conventional resin cement or RelyX U200-self-adhesive resin cement). After one week, the specimens were transversely sectioned into six 1-mm-thick disks and were subjected to the push out BS test. The data were subjected to 3-way ANOVA and Tukey's tests (α=0.05). The BS were not affected by the RCS, neither the CS (P>0.05). Just the period post obturation showed statistically significant differences (P 0.05), where the GFP cemented 6 months after the endodontic treatment showed higher values than those cemented 1 week after it.

Fracture strengths of endocrown restorations fabricated with different preparation depths and CAD/CAM materials

The objectives of this study were to compare the fracture strength of endocrown restorations fabricated with different preparation depth and various CAD/CAM ceramics, and to assess the fracture types. Endodontically treated 100 extracted human permanent maxillary centrals were divided into two preparation depth groups as short (S: 3-mm-deep) and long (L: 6-mm-deep), then five ceramic subgroups, namely: feldspathic-ceramic (Vita Mark II-VM2), lithium-disilicate glass-ceramic (IPS e.max CAD-E.max), resin-ceramic (LAVA Ultimate-LU), polymer infiltrated ceramic (Vita Enamic-VE) and monoblock zirconia (inCoris TZI-TZI) (n=10/subgroup). The endocrowns were fabricated by CAD/CAM and were cemented with resin cement (RelyX U200). The teeth were thermally cycled (5,000cycles) and fracture tests were performed at 45º angle to the teeth. The data were statistically analyzed (Kruskal-Wallis, Mann Whitney U), failure modes were evaluated with stereomicroscopy. Zirconia group provided the statistically highest fracture strength, but also exhibited non-repairable failures. Preparation depth has an effect on the fracture strength only for feldspathic ceramic.

Effect of time interval between core preparation and post cementation on pushout bond strength of glass fiber-reinforced posts

Introduction:

The aim of this study was to investigate the effect of timing of coronal preparation on the pushout bond strength of fiber postluted with resin cement in the root canal.

Materials and Methods:

In this experimental study, 48 mandibular human premolars were selected in a 3-week range. After root canal treatment and postspace preparation, a post #2(Angelus, Brazil) was cemented into the canal by a resin-based cement (Bifix SE, VOCO, Germany). Cylindrical resin composite cores were built on the posts. Then, the specimens were divided into 4 groups of 12 specimens each: one control group without core preparation and 3 experimental groups with core preparation that was done 15 min, 1 h, and 24 h after postcementation. One day after postcementation, each root was sectioned into 3 segments. Each slice was connected to universal testing machine. The load was applied at the speed of 0.5 mm/min till failure happened. The collected data were analyzed (SPSS/PC 20.0; SPSS Inc., Chicago, IL, USA) using two-way ANOVA and post hoc Tukey test at P < 0.05 level of significance.

Results:

Mean shear bond strength differences among interventional groups were not statistically significant (P > 0.05). Nevertheless, there were significant differences among root regions (P < 0.001).

Conclusion:

It was concluded that core preparation and its timing does not affect adversely retention of fiber post and bond strength is higher in the cervical segment.

Degree of conversion of resin cement with varying methacrylate compositions used to cement fiber dowels: A Raman spectroscopy study

STATEMENT OF PROBLEM

Studies on the degree of conversion of dental cement in relation to the number of methacrylate components are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the degree of conversion of single- and multicomponent methacrylate-containing dental cements around opaque and translucent fiber dowels at varying depths.

MATERIAL AND METHODS

Teeth were prepared for standard endodontic therapy, and a dowel space was created. Opaque and translucent fiber dowels consisting of Aestheti-Plus (AP) and FiberKleer were cemented with 4 methacrylate (MA)-containing cements, including RelyX U100 (R), which contains TEGDMA; Duolink (D), which contains TEGDMA and BisGMA; and Variolink N LC (V) and Breeze (B), which contain TEGDMA, BisGMA, and UDMA. Light-emitting diode polymerization was performed for 60 seconds. The specimens were immediately cut into halves and measured within the first hour at depths of 1, 3, and 5 mm using Raman spectroscopy, and the degree of conversion (DC) of resin cement was calculated. Data were analyzed using 3-way ANOVA and the Tukey multiple comparison test (α=.05).

RESULTS

The measured dowel regions were not significantly different at various depths (P=.10). The dowel and cement types significantly influenced the degree of conversion of the cement (P<.05). The V and B cements exhibited a higher DC than D and R cements. With AP dowels, the DC of cement D was lower than that of the V, B, and R cements.

CONCLUSIONS

Within the limitations of this in vitro study, the degrees of conversion of the tested resin cements were not affected by the tested dowel depths. Higher DC was found in cement with more than 2 types of flexible MA. Opaque dowels produced a lower DC than translucent dowels.

Strength comparison of anterior teeth restored with ceramic endocrowns vs custom-made post and cores

PURPOSE

The aim of the study was to compare strength of the anterior teeth restored with ceramic endocrowns versus custom-made post and core.

METHODS

The investigation used the finite element analysis. Three 3-D models of maxillary central incisor were created: model A-tooth restored with metal post and core with ceramic crown; model B-tooth with leucite ceramic endocrown; model C-tooth with lithium disilicate ceramic endocrown. Each model was subjected to a 100N force applied at a distance of 5mm from the incisal edge, at the angle of 130° to the long axis of the tooth. The modified von Mises failure criterion was used to evaluate the strength of the dentin, ceramic and resin cement, and Huber-Mises-Hencky failure criterion for cast alloy. Contact stresses in the cement-tissue adhesive interface were calculated.

RESULTS

The lowest stresses occurred in the anterior tooth restored with custom post and core (model A). The mvM stress of 47.5MPa concentrated in leucite ceramic endocrown (model B) and its value was close to the tensile strength of this material. The maximal mvM stresses in the lithium disilicate ceramic endocrown (model C) were 4 times lower than tensile strength of this material. In all cases contact stresses in the adhesive interface under restorations did not exceed the resin cement bond strength to dentin.

CONCLUSIONS

Leucite ceramic endocrowns in incisors may fracture during physiological loading. Endocrowns made of lithium disilicate ceramic are resistant to failure. Posts and prosthetic crowns are still recommended for anterior teeth restorations.

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.

Fracture resistance of endodontically treated teeth with different direct corono-radicular restoration methods

Background

Endodontically treated teeth are widely considered to be more susceptible to fracture than vital teeth. Obturation procedures and post placement have been a main cause of vertical root fracture.

Material and Methods

Forty-eight human premolars with standardized weakened roots were endodontically treated and allocated to four experimental groups (n=12). After root canal treatment, in group 1, fiber posts #1 were cemented in root canals using Estelite Core Quick, and the crowns were restored with resin composite. For group 2 and 3, the roots and crowns were restored using a light-cured and self-cured adhesive and resin composites respectively. In group 4, it was used the Panavia F 2.0 resin cement and resin composite for corono-radicular reconstruction. In group 5, the teeth remained untouched. After 24 hours storage and 1000 thermocycles, samples were loaded at a cross head speed of 1 mm per minute.

Results

A significant difference was observed in fracture resistance among groups 4 and 5 compared to other groups.

Conclusions

Root reconstruction with fiber post and Panavia resin cement, and crown building using light-cured resin composite resulted in increased fracture resistance equal to that of intact teeth.

Key words:Fracture resistance, fiber post, resin cement, resin composite.

Pull-out retentive strength of fiber posts cemented at different times in canals obturated with a eugenol-based sealer

STATEMENT OF PROBLEM

Currently, no standard luting protocol exists for fiber posts. In addition, no agreement has been reached on the time interval between canal obturation and post space preparation and cementation.

PURPOSE

The purpose of this in vitro study was to evaluate the retention of fiber posts cemented with 3 different types of cement: Paracore, Variolink II, and RelyX Unicem cement after 24 hours or 2 weeks in root canals obturated with gutta percha and a eugenol-based sealer.

MATERIAL AND METHODS

Seventy-two caries-free, freshly extracted, single-rooted human mandibular first premolar teeth with straight root canals were prepared and obturated with gutta percha and Endofil sealer. Specimens were divided into 2 groups (n=36): post spaces prepared 24 hours after obturation and post spaces prepared 2 weeks after obturation. Posts in both groups were luted with 1 of 3 different luting agents (n=12), ParaCore, Variolink II, or RelyX Unicem cement. Each tooth specimen was vertically secured in a universal testing machine, and a constant pull-out loading rate of 0.5 mm/min was applied until cement failure occurred. Data were statistically analyzed with 2-way and 1-way ANOVAs and t tests.

RESULTS

Two-way ANOVA indicated statistically significant differences in mean post retention among the 3 cement types (P<.001) and among the means of the different time intervals investigated (P<.001). Significant differences were noted among all cement types tested between the 24-hour and 2-week time intervals (P<.05).

CONCLUSIONS

Time elapsed between canal obturation and post cementation significantly influenced fiber post retention, regardless of the type of resin cement. Fiber posts showed significantly higher retention if cemented after 24 hours of obturation than if cementation occurred after 2 weeks.

Biomechanical interactions of endodontically treated tooth implant-supported prosthesis under fatigue test with acoustic emission monitoring

BACKGROUND

This study investigated the biomechanical interactions in endodontically treated tooth implant-supported prosthesis (TISP) with implant system variations under dynamic cyclic loads monitored using the acoustic emission (AE) technique.

METHODS

Macrostructure implants using a taper integrated screw-in (TIS; 2-piece implant) and a retaining-screw (RS; 3-piece implant) connected to an abutment were used for this investigation and their corresponding mechanical resistances in conformity with the ISO 14801 standard were evaluated. The endodontically treated TISP samples were constructed containing TIS and RS implants splinted to the second premolar with fatigue tests performed by applying occlusal force onto the premolar simulating the bending moment effect. The numbers of accumulated AE signals in the fatigue tests and failure modes for the sample were recorded to evaluate the mechanical resistance.

RESULT

The maximum load in the static test for RS (3-piece) implant (797N) was significantly higher than that for the TIS (2-piece) implant (559N). Large deformations were found at abutment screws in both RS and TIS implants. Although the numbers of accumulated AE signals for the TIS implant (72511) were higher than those for the RS implant (437), statistical non-significant differences were found between TIS and RS implants. No obvious damage was noted in endodontically treated TISP samples using RS implants but two of the corresponding TIS implants fractured in the abutment screws.

CONCLUSIONS

Splints with RS (3-piece) implant prosthesis produce better mechanical responses than the TIS (2-piece) implant when connected to an endodontically treated tooth restored with a post core and crown.

Push-Out Bond Strength Evaluation of Glass Fiber Posts With Different Resin Cements and Application Techniques

The purpose of this study was to evaluate the push-out strength of two different adhesive cements (total etch and self-adhesive) for glass fiber post (GFP) cementation using two different techniques (microbrush and elongation tip) of cement application. In addition, this study evaluated the effect of total-etch conditioning before the use of a self-adhesive cement. Sixty premolar specimens with a single root canal were selected, endodontically treated, and shaped for GFP cementation. The specimens were randomly placed into one of six groups according to the cement and technique used: RelyX ARC (ARC): ARC + microbrush, ARC + elongation tip; RelyX Unicem (RU): RU + microbrush, RU + elongation tip; or RelyX Unicem + 37% phosphoric acid (RUE): RUE + microbrush, RUE + elongation tip. Each specimen root was cut perpendicular to the vertical axis yielding six 1.0-mm-thick sections. Push-out strength test was performed, followed by statistical analysis using three-way analysis of variance and the Games-Howell test (p<0.05). Statistically significant differences between the groups were found (p< 0.05). The cervical third of the roots had the highest mean push-out strength values, while the apical third had the lowest mean values regardless of the technique used. The elongation technique produced higher mean push-out strength values compared to the microbrush technique. The self-etch adhesive cement had the highest mean push-out strength value in all thirds. The addition of a conditioning step before the self-etch adhesive cementation appears to be effective in enhancing push-out strength with GFPs.

Effect of Chlorhexidine and Ethanol Application on Long-term Push-out Bond Strength of Fiber Posts to Dentin

AIM

The aim of this study was to evaluate the effect of chlorhexidine and ethanol application on the push-out bond strength and bond durability of fiber posts cemented with an etch-and-rinse adhesive system/resin cement to intraradicular dentin.

MATERIALS AND METHODS

Fifty-four bovine roots were shaped for the cementation of a fiberglass post and received the application of 37% phosphoric acid. They were then randomly divided into three groups, according to the type of dentin treatment (n = 18) performed: no treatment (control group), 100% ethanol, or 2% chlorhexidine. Next, the adhesive system (Adper Scotch Bond Multipurpose Plus, 3M ESPE) was applied to the dentin, according to the manufacturer's instructions. Glass fiber posts were cemented with dual resin cement (Rely X ARC, 3M ESPE). After 48 hours, the specimens were serially sectioned for push-out test analysis, providing two slices from each root third (cervical, medium and apical), one of which was tested immediately and the other stored in distilled water for 180 days. The data were analyzed with three-way analysis of variance (ANOVA) for repeated measures and Tukey's test at a 5% significance level.

RESULTS

Intraradicular treatment with chlorhexidine yielded the highest bond strength means, followed by ethanol treatment. The control group presented the lowest bond strength means. Water storage exerted no effect on bond strength values.

CONCLUSION

Both chlorhexidine and ethanol improved push-out bond strength to intraradicular dentin, with the former providing the best results, regardless of the storage time.

CLINICAL SIGNIFICANCE

The application of 2% chlorhexidine or 100% ethanol may be an important step that can be taken to enhance bond strength of fiber posts to intraradicular dentin, when dual resin cements are used.

Evaluation of the resin cement thicknesses and push-out bond strengths of circular and oval fiber posts in oval-shapes canals

PURPOSE

The aim of this study was to evaluate whether the push-out bond strength varies between oval and circular fiber posts, and to examine the effect on the resin cement thicknesses around the posts.

MATERIALS AND METHODS

Eighteen mandibular premolar roots were separated into two groups for oval and circular fiber posts systems. Post spaces were prepared and fiber posts were luted to the post spaces. Roots were cut horizontally to produce 1-mm-thick specimens. Resin cement thicknesses were determined with a metallographic optical microscope and push-out tests were done.

RESULTS

No significant differences were observed in terms of push-out bond strength between the oval and circular fiber posts (P>.05) The resin cement thicknesses of the oval posts were greater than those of the circular posts group in the coronal, middle and apical specimens (P<.05).

CONCLUSION

In the light of these results, it can be stated that resin cement thickness does not affect the push-out bond strength.

Bonding effectiveness of two adhesive luting cements to glass fiber posts: pull-out evaluation of three different post surface conditioning methods

The purpose of this study was to evaluate the bond strength at the post/resin-cement interface with 3 different surface treatments of glass fiber posts and with 2 different luting resin cements. Sixty glass fiber posts (RelyX Fiber Post) were randomly divided into 3 groups (n = 20) and were luted with a dual-polymerizing self-adhesive universal resin cement (RelyX Unicem) and with a dual-polymerizing resin cement (RelyX ARC). This was carried out in association with a dual-polymerizing adhesive (Scotchbond Multi-Purpose Plus) in simulated plexiglass root canals after receiving three different pretreatment procedures. A pull-out test was performed on each sample to measure bond strengths. Data were analyzed with two-way ANOVA. Two samples from each group were processed for SEM observations in order to investigate the morphologic aspect of the post/cement interface. Both resin cements demonstrated significant different bond strength values (P < 0.0001). The surface treatment result was also statistically significant (P = 0.0465). SEM examination showed a modification of the post surface after pretreatment with methyl methacrylate. The dual-polymerizing self-adhesive universal resin cement achieved higher MPa bond strength values. The use of methyl methacrylate as a surface treatment of glass fiber posts provided a significant increase in bond strengths between the posts and both luting materials.

Effect of chlorhexidine and ethanol-wet bonding with a hydrophobic adhesive to intraradicular dentine

PURPOSE

To evaluate the effect of adjunctive application of ethanol-wet bonding and chlorhexidine (CHX) with a hydrophobic adhesive on bond durability of fibre posts to intraradicular dentine.

METHODS

Ninety-six extracted human teeth with a single root and root canal were prepared for post placement after endodontic treatment. The teeth were randomly divided into four groups (n=24) after etching and rinsing for rewetting: Group 1: water-wet bonding, Group 2: water-wet bonding with CHX, Group 3: ethanol-wet bonding and Group 4: ethanol-wet bonding with CHX. Teeth in Groups 1 and 2 were treated with either distilled water or distilled water with 2% CHX for 60 s; while teeth in Groups 3 and 4 were treated with either 100% ethanol or 100% ethanol with 2% CHX. Two coats of primer, followed by neat resin were applied and light-cured for 40 s. Fibre posts were luted to bonded root dentine using dual-cure resin cement. Bonded roots were subjected to push-out bond strength testing and interfacial nanoleakage evaluation after 24 h, 6 and 12 months of storage. Data were analyzed using 3-way ANOVA (rewetting solutions, time and post space regions) and SNK tests.

RESULTS

Groups 3 and 4 showed significantly (p<0.05) higher bond strengths and lower nanoleakage than Groups 1 and 2 after 12 months of ageing. Addition of 2% chlorhexidine to ethanol-wet bonding with a hydrophobic adhesive did not further improve the bonding of a fibre post to intraradicular dentine, when compared to ethanol-wet bonding alone after 12 months of ageing.

CLINICAL SIGNIFICANCE

Ethanol-wet bonding with a hydrophobic adhesive alone could improve the bond durability of fibre post to intraradicular dentine and therefore would increase the success rate of post and core restorations of endodontically treated teeth.

Fiber-post bond strength in canals obturated with a cross-linked gutta-percha core obturator

The aim of this in-vitro study was to evaluate the bond strength of fiber posts cemented in a root canal filled using various root-canal obturation techniques. A total of 33 monoradicular samples, treated endodontically, were randomly assigned to three groups according to the root-canal obturation technique: group 1, continuous-wave technique; group 2, plastic-obturator-core technique; and group 3, cross-linked gutta-percha obturator-core technique. Fiber posts were luted in each sample and each was sectioned perpendicular to the post axis. The push-out test was performed using a universal machine and the maximum failure load was recorded in MPa mm(-2) . Several samples were randomly chosen for scanning electron microscopy evaluation. The mean debris and dentinal tubule-opening scores were calculated separately in the coronal and apical portions. Bond strength was significantly higher in group 1 than in groups 2 and 3. Debris scores were significantly higher in the apical portion of groups 2 and 3 than in group 1. Within the limitations of this study it can be affirmed that thermoplasticized alpha gutta-percha seemed to worsen the cleaning of post-space walls and hence reduced fiber-post bond strength.

The influence of different cements on the pull-out bond strength of fiber posts

STATEMENT OF PROBLEM

Glass fiber posts are commonly used to provide adequate support and retention for the restoration of endodontically treated teeth, but their resistance to dislodgement depends on their adhesion to root dentin.

PURPOSE

The purpose of this study was to assess the effect of cement type on the pull-out bond strength of fiber posts.

MATERIAL AND METHODS

Seventy maxillary canines were endodontically treated and then divided into 7 groups according to the cement used for fiber post cementation as follows (n = 10): RelyX Unicem, BisCem, RelyX Luting 2, RelyX ARC, Panavia F, Enforce, and Allcem. The specimens were subjected to a pull-out bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The results, in newtons, were analyzed with 1-way ANOVA and the Tukey post hoc test (α = .05).

RESULTS

RelyX Unicem (472.3 ± 8.9 N), BisCem (506.6 ± 9.2 N), RelyX ARC (498.0 ± 8.2 N), Panavia F (502.3 ± 7.0 N), and Allcem (470.0 ± 11.3 N) presented significantly higher bond strength than RelyX Luting 2 (241.8 ± 9.70 N) and Enforce (309.5 ± 6.3 N) cements (mean ± SD; P < .05).

CONCLUSIONS

Except for Enforce, all resin cements produced pull-out bond strength values twice that of resin modified glass ionomer cement. However, all cements promoted adequate retention to fiber posts to withstand functional loads.

Degradation in the dentin-composite interface subjected to multi-species biofilm challenges

Oral biofilms can degrade the components in dental resin-based composite restorations, thus compromising marginal integrity and leading to secondary caries. This study investigates the mechanical integrity of the dentin-composite interface challenged with multi-species oral biofilms. While most studies used single-species biofilms, the present study used a more realistic, diverse biofilm model produced directly from plaques collected from donors with a history of early childhood caries. Dentin-composite disks were made using bovine incisor roots filled with Z100(TM) or Filtek(TM) LS (3M ESPE). The disks were incubated for 72 h in paired CDC biofilm reactors, using a previously published protocol. One reactor was pulsed with sucrose, and the other was not. A sterile saliva-only control group was run with sucrose pulsing. The disks were fractured under diametral compression to evaluate their interfacial bond strength. The surface deformation of the disks was mapped using digital image correlation to ascertain the fracture origin. Fracture surfaces were examined using scanning electron microscopy/energy-dispersive X-ray spectroscopy to assess demineralization and interfacial degradation. Dentin demineralization was greater under sucrose-pulsed biofilms, as the pH dropped <5.5 during pulsing, with LS and Z100 specimens suffering similar degrees of surface mineral loss. Biofilm growth with sucrose pulsing also caused preferential degradation of the composite-dentin interface, depending on the composite/adhesive system used. Specifically, Z100 specimens showed greater bond strength reduction and more frequent cohesive failure in the adhesive layer. This was attributed to the inferior dentin coverage by Z100 adhesive, which possibly led to a higher level of chemical and enzymatic degradation. The results suggested that factors other than dentin demineralization were also responsible for interfacial degradation. A clinically relevant in vitro biofilm model was therefore developed, which would effectively allow assessment of the degradation of the dentin-composite interface subjected to multi-species biofilm challenge.

In Vitro Evaluation of the Effect of Different Endodontic Sealers on Retentive Strength of Fiber Posts

Purpose

There is limited information in the literature regarding the effect of different endodontic sealers on the bond strength of fiber posts luted with core buildup materials. The purpose of this study was to evaluate the effect of three different root canal sealers on the retentive strength of prefabricated fiber posts luted with a composite resin cement.

Materials and Methods

Fifty-four extracted single-rooted mandibular premolar teeth were prepared and randomly divided into three groups. The first two groups were obturated with gutta-percha and one of two eugenol-based root canal sealers (Endofil, Tubli-Seal). The third group (control) was obturated with gutta-percha and a resin-based root canal sealer (AH26). Prefabricated fiber posts were luted into the prepared post spaces with a composite resin cement (Multicore Flow). The pullout forces required for dislodgment of posts from their prepared post spaces were recorded. Data were collected and statistically analyzed.

Results

The AH26 group had significantly greater retentive strengths for the posts when compared with the Endofil and Tubli-Seal (eugenol-based sealers) groups (p&lt;0.0001). There was no significant difference between the means of the retentive strengths for the Endofil and Tubli-Seal groups (p=0.745).

Conclusion

The chemical formulation of root canal sealers significantly affected the retentive strength for prefabricated fiber posts luted with a resin cement. Eugenol-based sealers significantly reduced the bond strength of prefabricated fiber posts luted with resin cement.

Microleakage of endodontically treated teeth restored with 3 different adhesive systems and 4 different fiber-reinforced posts

STATEMENT OF PROBLEM

Despite recent advances in adhesive dentistry, fiber-reinforced post/resin cement/dentin adhesive combinations are not able to prevent microleakage. While studies have examined microleakage in endodontically treated teeth restored with posts and cores, microleakage among post and adhesive systems remains a concern.

PURPOSE

This study compared the sealing properties of 4 adhesively luted post systems: glass fiber, quartz-glass fiber, zirconia-glass fiber and polyethylene fiber posts.

MATERIAL AND METHODS

Forty-eight permanent maxillary central incisors were divided into 4 groups (n=12). Post space was prepared and each post was adhesively luted with 1 of 3 systems: a 1-stage self-etch, a 2-stage total-etch, and a 3-stage total-etch adhesive. The specimens were separately immersed in freshly prepared 2% methylene blue solution for 1 week. The cleaned specimens were then embedded in autopolymerizing acrylic resin. The teeth were horizontally sectioned into apical, middle, and coronal portions. An occlusal view of each section was digitally photographed with a stereomicroscope. The methylene blue-infiltrated surface for each specimen was measured and data were collected with software. Dye penetration was estimated as the ratio of the methylene blue-infiltrated surface to the total dentin surface. Nonparametric data were analyzed with the Kruskal-Wallis test (α=.05). The Mann-Whitney U-test was used to compute multiple pairwise comparisons that identified differences among groups. Dentin-luting agent and post interfaces were evaluated with a scanning electron microscope.

RESULTS

Significant differences in adhesive and post systems were observed in all sectioned regions (P<.05). There were significant differences between the apical and coronal sections of each post type, and between the following pairs: middle versus coronal sections of zirconia-glass fiber and glass fiber posts and apical versus middle sections of quartz-glass fiber and polyethylene fiber posts (P<.05). No significant differences were found among post types. The variables of middle section and 3-stage adhesive produced significant differences in microleakage between the following post pairs: zirconia-glass fiber versus quartz-glass fiber, zirconia-glass fiber versus polyethylene fiber, and quartz-glass fiber versus polyethylene fiber (P<.05).

CONCLUSIONS

The 3-stage adhesive and zirconia-glass fiber posts demonstrated the least microleakage.

Ultrastructural evaluation of the hybrid layer after cementation of fiber posts using adhesive systems with different curing modes

This in vitro study evaluated the adhesive interface of intraradicular fiber glass posts and root dentin using scanning electron microscopy (SEM). Forty-eight single-rooted premolars were randomly divided into 6 groups consisting of chemical, dual, or light cured adhesive systems combined with either chemical or dual cure resin cements. Scanning electron microscopic analysis showed the best results for continuity, density and morphology of the hybrid layer and resin tags for the combination of a self-cure adhesive with self-cure cement resin, followed by a dual-cure adhesive with self-cure cement resin, and finally a light-cure adhesive with self-cure cement. For the dual-cure resin cement, the same relation may be observed. The apical third was the most critical region for evaluated the criteria for all combinations of materials (Kruskal-Wallis and Friedman tests; p<0.001). Generally, the simplification of steps in the adhesive system and the polymerization reaction of resin adhesives and cements produced a direct effect on the quality of the adhesive post/dentin substrate interface.

Push-out bond strength of quartz fibre posts to root canal dentin using total-etch and self-adhesive resin cements

Objectives: Several adhesive systems are available for cementation of fibre posts into the root canal. The aim of the present study was to investigate the push-out bond strengths of quartz fibre posts to root dentin with the use of different total-etch and self-adhesive resin cements. Study Design: Ninety single-rooted human premolars were endodontically treated and standardized post-spaces were prepared. Fibre posts were cemented with different luting agents: total-etch (Nexus NX3, Duo-Link, and RelyX ARC) and self-adhesive resin cements (Maxcem Elite, BisCem, and RelyX Unicem). Three post/dentin sections (coronal, middle and apical) were obtained from each specimen, and push-out bond strength test was performed in each section at a cross-head speed of 0.5 mm/min. Data was analyzed with two-factor and one-way analysis of variance and a post-hoc Tukey test at a significance level of p < 0.05. Results: Cement type, canal region, and their interaction significantly influenced bond strength. Significantly higher bond strength values were observed in the apical region of self-adhesive cements. Only Duo-Link and RelyX ARC cements resulted in homogeneous bond strengths. Conclusions: Cementation of quartz fibre posts using self-adhesive cements provided higher push-out bond strengths especially in the apical region, while total-etch cements resulted in more uniform bond strengths in different regions of the root canal.

Key words: Push-out bond strength; quartz fibre post; total-etch resin cement; self-adhesive resin cement.