The effect of different adhesive system applications on push-out bond strengths of glass fiber posts

PURPOSE

Over the past years, the adhesion of fiber posts luted with simplified adhesive systems has been a matter of great interest. The aim of this study was to assess the post retentive potential of a self-adhesive resin cement using different adhesive systems to compare the push-out bond strengths of fiber posts.

MATERIALS AND METHODS

The post spaces of 56 mandibular premolar roots were prepared and divided into 4 experimental groups and further divided into 2 subgroups according to testing time (n=7). The fiber posts (Rely X Fiber Post) were luted with a self-adhesive resin cement (RelyX Unicem) and one of the following adhesive systems: no adhesive, a total-etch adhesive resin (Single Bond), a two-step self-etch adhesive resin (Clearfil SE Bond) and a one-step self-etch adhesive resin (Clearfil S3 Bond). Each root was cut horizontally, and 1.5 mm thick six root segments were prepared. Push-out tests were performed after one week or three months (0.5 mm/min). Statistical analysis were performed with three-way ANOVA (α=.05).

RESULTS

Cervical root segments showed higher bond strength values than middle segments. Adhesive application increased the bond strength. For one week group, the total-etch adhesive resin Single Bond showed higher bond strength than the self-adhesive resin cement RelyX Unicem applied without adhesive resin at middle region. For 3 months group, the two-step self-etch adhesive resin Clearfil SE Bond showed the highest bond strength for both regions. Regarding the time considered, Clearfil SE Bond 3 months group showed higher bond strength values than one week group.

CONCLUSION

Using the adhesive resins in combination with the self-adhesive resin cement improves the bond strengths. The bond strength values of two-step self-etch adhesive resin Clearfil SE Bond improved as time passes.     

Bonding of fibre-reinforced composite post to root canal dentin

OBJECTIVE: The aim of this study was to determine bonding properties of two types of fibre-reinforced composite (FRC) posts cemented into root canals of molars. Serrated titanium posts served as reference. METHODS: Prefabricated carbon/graphite FRC posts with cross-linked polymer matrix and individually formed glass FRC posts with interpenetrating polymer network (IPN) polymer matrix were compared. The crowns of extracted third molars were removed and post space (diameter: 1.5mm) was drilled, etched and bonded. The posts were treated with dimethacrylate adhesive resin, light-polymerized and cemented with a dual-polymerizing composite resin luting cement. After thermocycling (6000x) the samples were cut into discs of thicknesses: 1, 2 and 4mm (n=12/group). Push-out force was measured by pushing the post from one end. Assessment of failure mode was made under a stereomicroscope (1, adhesive failure between post and cement; 2, cohesive failure of post-system; 3, adhesive failure between cement and dentin). RESULTS: The push-out force increased with increased height of dentin disc in all groups (ANOVA, p<0.001). In the 4mm thick dentin discs the individually formed glass FRC posts showed highest push-out force and the difference to that of the titanium posts was significant (ANOVA, p<0.001). The other differences were not statistically significant. None of the individually formed glass FRC posts showed adhesive failures between the post and the cement. CONCLUSIONS: Contrary to the other posts, there were no adhesive (post-cement) failures with the individually formed glass FRC posts, suggesting better interfacial adhesion of cement to these posts.     

Efficacy of a self-curing adhesive-resin cement system on luting glass-fiber posts into root canals: an SEM investigation

PURPOSE: The aim of this study was to evaluate the efficacy of a new bonding-luting system in resin tag, adhesive lateral branch, and hybrid layer formation when used in combination with an experimental fiber post. MATERIALS AND METHODS: Thirty anterior teeth extracted for periodontal reasons were selected for this study. They were endodontically treated and randomly divided into three groups of 10 samples each: group 1 = Excite light-cured bonding agent in combination with Variolink II resin cement; group 2 = Excite dual-cured bonding agent self-activated by an experimental microbrush in combination with MultiLink resin cement; and group 3 = one-step bonding system in combination with Dual Link resin cement. In groups 1 and 3, the primer-adhesive solution was light cured before placing the resin cement and the post, whereas in group 2 the adhesive/luting materials were not light cured. Twenty FRC Postec translucent posts (groups 1 and 2) and 10 EndoAesthetic translucent fiber posts (group 3) were used. One week later, the root samples were processed for scanning electron microscopic (SEM) observations. RESULTS: Microscopic examinations of restored interfaces from group 2 revealed a resin-dentin interdiffusion zone higher than that seen in samples from groups 1 and 3 (P < .05). At the apical and middle thirds, the samples from group 2 showed significantly more resin tags than the other two groups. CONCLUSION: The dual-cure self-activating system showed a more uniform resin tag and resin-dentin interdiffusion zone formation along root canal walls than light-curing systems.     

Influence of a microbrush on bonding fiber post into root canals under clinical conditions

OBJECTIVE: The objective of this clinical report was to evaluate the effectiveness of a microbrush as a carrier of priming-adhesive solution in formation of resin tags, adhesive lateral branches, and resin-dentin interdiffusion zone (RDIZ) when the brush was used to bond fiber posts under clinical conditions. STUDY DESIGN: Twenty endodontically treated teeth, already scheduled for extraction for endodontic or periodontal reasons, were selected for this study. The patients were informed, and their written consent was obtained. The samples were randomly divided into 2 groups of 10 samples each. In group 1, One-Step (Bisco, Schaumburg, Ill) was applied with a brush with Duo-Link resin cement (Bisco). In group 2, One-Step was applied with a microbrush with Duo-Link resin cement (Bisco). Use of the adhesive systems and resin cements was strictly according to manufacturers' instructions. The priming-adhesive solution was light-cured before the dual resin cement and the post were placed. Twenty Aestheti-Plus posts (white quartz fiber posts; RTD, St. Egreve, France) were used. A week after application, the root samples were extracted and processed for SEM observations. RESULTS: Both adhesive systems showed RDIZ and resin tag and adhesive lateral branch formation. In Group 2 samples, RDIZ morphology was easily detectable and uniform along root canals. Also, resin tag formation was well represented in all thirds. In group 1 samples, resin tag formation at the apical third and RDIZ formation was less evident. Statistically significant differences were found among the two groups at the apical third. CONCLUSION: The microbrush permitted a more uniform RDIZ and resin tag formation along the entire length of the canal than did the standard brush. The microbrush can be routinely used for bonding fiber posts into root canal preparations.     

Does the thickness of the resin cement affect the bond strength of a fiber post to the root dentin?

This study aimed to evaluate the influence of cement thickness on the bond strength of a fiber-reinforced composite (FRC) post system to the root dentin. Eighteen single-rooted human teeth were decoronated (length: 16 mm), the canals were prepared, and the specimens were randomly allocated to 2 groups (n = 9): group 1 (low cement thickness), in which size 3 FRC posts were cemented using adhesive plus resin cement; and group 2 (high cement thickness), in which size 1 FRC posts were cemented as in group 1. Specimens were sectioned, producing 5 samples (thickness: 1.5 mm). For cement thickness evaluation, photographs of the samples were taken using an optical microscope, and the images were analyzed. Each sample was tested in push-out, and data were statistically analyzed. Bond strengths of groups 1 and 2 did not show significant differences (P = .558), but the cement thicknesses for these groups were significantly different (P < .0001). The increase in cement thickness did not significantly affect the bond strength (r2 = 0.1389, P= .936). Increased cement thickness surrounding the FRC post did not impair the bond strength.     

Influence of airborne-particle abrasion on mechanical properties and bond strength of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts

STATEMENT OF PROBLEM: Controversy exists concerning the use of fiber-reinforced posts to improve bond strength to resin cement because some precementation treatments can compromise the mechanical properties of the posts. PURPOSE: The purpose of this study was to analyze the influence of airborne-particle abrasion on the mechanical properties and microtensile bond strength (MTBS) of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts. MATERIAL AND METHODS: Flexural strength (delta(f)), flexural modulus (E(f)), and stiffness (S) were assessed using a 3-point bending test for glass fiber-reinforced and carbon fiber-reinforced resin posts submitted to airborne-particle abrasion (AB) with 50-microm Al(2)O(3), and for posts without any surface treatment (controls) (n=10). Forty glass fiber (GF) and 40 carbon fiber (CF) posts were submitted to 1 of 4 surface treatments (n=10) prior to MTBS testing: silane (S); silane and adhesive (SA); airborne-particle abrasion with 50-microm Al(2)O(3) and silane (ABS); airborne-particle abrasion, silane, and adhesive (ABSA). Two composite resin restorations (Filtek Z250) with rounded depressions in the lateral face were bilaterally fixed to the post with resin cement (RelyX ARC). Next, the specimen was sectioned with a precision saw running perpendicular to the bonded surface to obtain 10 bonded beam specimens with a cross-sectional area of 1 mm(2). Each beam specimen was tested in a mechanical testing machine (EMIC 2,000 DL), under stress, at a crosshead speed of 0.5 mm/min until failure. Data were analyzed by 2-way ANOVA followed by Tukey HSD test (alpha=.05). Failure patterns of tested specimens were analyzed using scanning electron microscopy (SEM). RESULTS: The 3-point bending test demonstrated significant differences among groups only for the post type factor for flexural strength, flexural modulus, and stiffness. The carbon fiber posts exhibited significantly higher mean flexural strength (P=.001), flexural modulus (P=.003), and stiffness (P=.001) values when compared with glass fiber posts, irrespective of surface treatment. An alteration in the superficial structure of the posts could be observed by SEM after airborne-particle abrasion. MTBS testing showed no significant effect for the surface treatment type; however, significant effects for post system factor and for interaction between the 2 factors were observed. For the carbon fiber post, the ABSA surface treatment resulted in values significantly lower than the S surface treatment. SEM analysis of MTBS-tested specimens demonstrated adhesive and cohesive failures. CONCLUSIONS: Airborne-particle abrasion did not influence the mechanical properties of the post; however, it produced undesirable surface changes, which could reduce the bond strength to resin cement. For the surface treatments studied, if silane is applied, the adhesive system and airborne-particle abrasion are not necessary.     

Randomized controlled clinical pilot trial of titanium vs. glass fiber prefabricated posts: preliminary results after up to 3 years

PURPOSE: This randomized parallel-group clinical pilot study aimed to compare the clinical outcome of prefabricated rigid titanium to glass fiber endodontic posts when luted with self-adhesive universal resin cement. MATERIALS AND METHODS: Ninety-eight patients in need of postendodontic restoration were assessed for eligibility. Ninety-one patients met the selection criteria and were randomized and allocated to 2 intervention groups. Forty-five participants were treated using a titanium post and 46 participants received a glass fiber post, each in combination with composite core buildups for postendodontic restoration. All posts had a diameter of 1.4 mm and a length of 13 mm and were cemented 8 mm within the root canal with self-adhesive universal resin cement. A circumferential ferrule of 2 mm was always provided. Surgical crown lengthening was necessary in 13 cases. Patients were observed in intervals of 3, 6, 12, 24, and 36 months after post placement. RESULTS: After 24 to 36 months (mean +/- SD: 27.9 +/- 5.6) of observation following post placement, 1 tooth was extracted because of changes of the prosthetic treatment plan. No failures were observed among the 88 patients with follow-up data. CONCLUSIONS: Both titanium and glass fiber reinforced composite posts result in successful treatment outcomes after 2 years. The material combination used seems to be appropriate in the short term for cementing endodontic posts, irrespective of the post material.     

A one step procedure for luting glass fibre posts: an SEM evaluation

AIM: To evaluate the ability of two luting procedures for bonding translucent fibre posts to form resin tags, adhesive lateral branches, and resin dentine interdiffusion zones (RDIZ). METHODOLOGY: Forty root filled teeth, extracted for periodontal reasons, were selected for the study. The teeth were randomly divided into four groups of 10 each. Group 1: One Step, light-cured (LC) 20 s + dual link resin cement (LC 20 s); group 2: One Step, not light-cured (NLC) + dual link resin cement (LC 30 s); group 3: One Step (NLC) + dual link resin cement (LC 60 s); group 4: One Step (NLC) + dual link resin cement (LC 90 sec). Forty translucent fibre posts (DT posts, RTD) were inserted. Then, root specimens were processed for scanning electron microscope (SEM) observations to assess the continuity of the RDIZ, the presence or absence of gaps and the density and morphology of resin tags using a four-step scale method. RESULTS: With all luting procedures the formation of a RDIZ occurred. However, the microscopic examination of adhesive interfaces revealed that the percentage of RDIZ was significantly higher in group 1 than in the other three groups (P < 0.05). Group 4 had a higher percentage of RDIZ than group 3, which in turn exhibited a greater percentage than group 2, but these differences were not statistically significant (P > 0.05). Resin tag formation was evident in all the groups. The characteristic reverse cone shape of resin tags was always noted in the coronal and middle third of all groups, and in the apical third of group 1. In the apical third a shorter length and a less uniform appearance of resin tags were noted in groups 2, 3 and 4. CONCLUSIONS: In this laboratory study, when bonding a translucent fibre post into a root canal, the luting procedure including light curing of the adhesive solution before the placement of the cement was more satisfactory, from a SEM standpoint, than the procedure involving the simultaneous curing of adhesive and cement (one step procedure).     

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

OBJECTIVES: Recently, several adhesives have been proposed for bonding fiber posts into root canals. The aim of this study was to evaluate the influence of four adhesive procedures in resin tag, adhesive lateral branch and resin dentin interdiffusion zone (RDIZ) formation when used to bond fiber posts. METHOD: Forty anterior teeth, extracted for periodontal reasons and endodontically treated, were selected for this study. The samples were randomly divided into four groups of ten samples each. Group 1: One Step applied with the small brush provided by the manufacturer and LC (Light-cured before resin cement application)+Dual Link resin cement; Group 2: One Step applied with a thin microbrush LC+Dual Link resin cement; Group 3: One Step applied with a small brush (Not light-cured)+Dual Link resin cement; Group 4: All Bond 2+C & B resin cement (as control). In Group 2 and 4 the adhesive system and resin cement were used strictly following manufacturers' instructions. In Group 1, One Step was applied using a thin microbrush, while in the other groups by a small brush. In Group 1 and 2 the priming-adhesive solution of the "one-bottle" system was light-cured before placing the resin cement and the post, whereas in Group 3 the adhesive/resin cement combination was light cured through the translucent post. Forty translucent posts (RTD, France) were used. A week later, the root samples were processed for SEM observations. RESULTS: Microscopic examination of restored interfaces of Group 1 showed a higher % (P<0.05) of RDIZ than those found in samples of Group 2, 3 and 4. In Group 2, 3 and 4 samples RDIZ morphology was well detectable and uniform in the first two thirds of root canals while in the apical third the RDIZ was not uniformly present. No statistically significant differences were found among the groups coronally, whereas apical and middle thirds of Group 1 showed significantly more resin tags than the other three Groups. In the apical third of Group 2, 3 and 4 samples, the resin tags showed a less uniform morphology and a shorter length than those found in the other two thirds. SIGNIFICANCE: A microbrush might clinically be used for bonding fiber posts into the root canal. When a microbrush was used, the bonding mechanism created between root canal dentin and bonding system was uniform along canal walls and more predictable.     

Push‐out bond strength of an experimental self‐adhesive resin cement

The adhesion of fiber posts luted with simplified adhesive systems has been a matter of great interest over the past years. The aim of this study was to assess the post retentive potential of experimental self‐adhesive resin cement (EXP) when used alone and in combination with a self‐etch adhesive. Fiber posts were placed in endodontically treated teeth and divided into four groups (n = 6) according the luting material, as follows: group 1 (EXP alone); group 2 (EXP used with self‐etch adhesive); group 3 (marketed dual‐cured cement used with self‐etch adhesive); and group 4 (marketed self‐adhesive cement). The push‐out test was used to assess the retentive strength of fiber posts (expressed in MPa), and specimens were analyzed under a stereomicroscope to determine failure mode. The adhesive interface between the cement and root canal dentin for each group was evaluated using scanning electron microscopy. The post retentive potential of group 1 (EXP) (7.48 ± 4.35 MPa) was comparable with that of marketed cements from group 4 (6.79 ± 3.68 MPa) and group 3 (8.77 ± 4.58 MPa). When EXP was used in combination with self‐etch adhesive (group 2), significantly higher push‐out bond‐strength values were measured (15.87 ± 4.68 MPa) compared with the other groups.     

Effect of dowel length on the retention of 2 different prefabricated posts.

OBJECTIVE: To compare in vitro the retentive values of stainless steel, parallel-sided posts to quartz-fiber, tapered posts for 2 different dowel lengths (5 and 10 mm). METHOD AND MATERIALS: Both post systems were cemented with a dual-cure adhesive resin cement. Single-rooted extracted human teeth (n = 40) were decoronated and randomly divided into 4 groups of 10 samples each. Posts of 5 and 10 mm in length were luted with the resin cement. Each sample was placed on a universal testing machine, and using a push-out method, a vertical load was applied at a crosshead speed of 2 mm/min. The amount of force required to dislodge the post was recorded. The effect of post type and length was evaluated using a 2-way analysis of variance. RESULTS: A statistically significant main effect was found for post length (P <.001), with the 10-mm posts of both post systems requiring greater force to dislodge than the 5-mm posts. There was no interaction between post length and post type (P >.05). CONCLUSION: It is concluded from this study that there is no statistical difference in retention between quartz-fiber, tapered posts and stainless steel, parallel-sided posts when they are cemented with the same resin cement (P >.05). The study also concludes that adequate retentive values are achieved with both post systems at the shorter, 5-mm post length.     

Multi-step adhesive cementation versus one-step adhesive cementation: push-out bond strength between fiber post and root dentin before and after mechanical cycling

This study evaluated the effects of mechanical cycling on resin push-out bond strength to root dentin, using two strategies for fiber post cementation. Forty bovine roots were embedded in acrylic resin after root canal preparation using a custom drill of the fiber post system. The fiber posts were cemented into root canals using two different strategies (N = 20): a conventional adhesive approach using a three-step etch-and-rinse adhesive system combined with a conventional resin cement (ScotchBond Multi Purpose Plus + RelyX ARC ), or a simplified adhesive approach using a self-adhesive resin cement (RelyX U100). The core was built up with composite resin and half of the specimens from each cementation strategy were submitted to mechanical cycling (45 degree angle; 37 degrees C; 88 N; 4 Hz; 700,000 cycles). Each specimen was cross-sectioned and the disk specimens were pushed-out. The means from every group (n = 10) were statistically analyzed using a two-way ANOVA and a Tukey test (P = 0.05). The cementation strategy affected the push-out results (P < 0.001), while mechanical cycling did not (P = 0.3716). The simplified approach (a self-adhesive resin cement) had better bond performance despite the conditioning. The self-adhesive resin cement appears to be a good option for post cementation. Further trials are needed to confirm these results.     

Microleakage of endodontically treated teeth restored with fiber posts and composite cores after cyclic loading: a confocal microscopic study

STATEMENT OF PROBLEM: The effectiveness of the seal obtained with carbon fiber posts and composite cores is still unclear. Both 3-step dental adhesives and self-etching adhesive primers have been suggested as adhesive systems. PURPOSE: This confocal microscopic study evaluated the microleakage of teeth endodontically treated and restored with fiber posts and composites with 3 adhesive systems. MATERIAL AND METHODS: A total of 72 human mandibular premolars were endodontically treated and divided into 6 groups of 12 teeth each. The first 3 groups were treated with an endodontic sealer containing zinc oxide-eugenol (ZOE) and restored with temporary filling materials containing ZOE. The last 3 groups were treated with ZOE-free materials. Post spaces were prepared in the root canals. The first group treated with ZOE-based materials was restored with fiber posts cemented with zinc phosphate cement and composite cores without adhesive. The other 2 groups of ZOE-treated teeth were restored with fiber posts cemented with All Bond 2 and Panavia 21 dental adhesives, respectively. The last 3 groups were restored with fiber posts cemented with All Bond 2, Panavia 21, and Panavia Fluoro cement, respectively. The teeth were loaded intermittently at 2 cycles per second in a moist environment and, after 300,000 cycles, immersed in a solution of Rhodamine B dye for 48 hours. A confocal microscope was used to observe the teeth. The ratio between the length of the interfaces observed and the length of the dye penetration was evaluated. Two teeth from each group acted as controls and were not subjected to dynamic loads. RESULTS: All resin cement groups leaked significantly less than the group cemented with zinc phosphate cement. No statistically significant difference was found between the microleakage of teeth treated with ZOE-based and non-ZOE-based materials. Teeth restored with All Bond 2 dental adhesive leaked significantly less than those restored with Panavia cement. CONCLUSION: The 3-step dental adhesive (All Bond 2) resulted in a better marginal seal than that obtained with the self-etching primers (Panavia 21 and Panavia F). The use of endodontic sealers and temporary filling materials containing ZOE had no detrimental effect on the marginal seal of carbon fiber post/composite resin core restorations.     

纤维桩导光性对根管内树脂水门汀聚合的影响

目的:评价2种不同导光性能的纤维桩对根管深部树脂水门汀聚合程度的影响.方法:16颗单根人前磨牙去冠后根管预备,随机分为导光组和非导光组(n=8).分别以i-TFC导光纤维桩和非导光性Pananiva纤维桩联合光固化树脂水门汀行桩核修复.每个修复后的牙根制备3枚牙本质片,依照其位置分为根颈段、根中段、根尖段.测试2组树脂水门汀在根管不同深度的努氏(Knoop)显微硬度值(HK)并计算其相对聚合度,进行双因素方差分析.结果:随根管深度的增加,2组树脂水门汀的显微硬度和相对固化率均呈下降趋势,根颈段和中段2项指标组间差异无统计学意义(P＞0.05).导光组和非导光组树脂水门汀在根尖段的HK值分别为33.25±3.04和23.80±5.93(P＜0.05).在根尖段的相对聚合度分别为69.89％与50.05％ (P＜0.05).结论:导光纤维桩有助于提高树脂水门汀在根尖区域的聚合程度.     

The effect of resin cement film thickness on the pullout strength of a fiber-reinforced post system

STATEMENT OF PROBLEM: Debonding is a common cause of failure encountered with fiber posts and usually occurs along the post space-dentin adhesive interface. The ideal thickness of the resin cement needed to improve retentive bond strength is unknown. PURPOSE: The purpose of this study was to evaluate the effect of 4 different post-space diameters and related resin cement film thicknesses on the bond strength between fiber posts and root dentin. MATERIAL AND METHODS: Eighty human maxillary central incisors with similar root lengths were selected, sectioned at the cemento-enamel junction, and the roots were treated endodontically. The roots were divided into 4 groups (n=20), and the post spaces were prepared to a depth of 8 mm using 1 of 4 different drills with a different diameter: Torpan drill ISO 90 for the control group (D90); and Torpan Drill ISO 100 (D100), Torpan Drill ISO 120 (D120), or Enapost Drill ISO 140 (D140) for the 3 test groups. Quartz fiber posts (Endo Lightpost), 0.9 mm in apical diameter, were luted (Panavia 21) in each specimen after dentin bonding procedures. The specimens were then subjected to a pullout test using a universal testing machine at a crosshead speed of 1.0 mm/min, and the maximum force required to dislodge each post was recorded (N). Data were analyzed using 1-way ANOVA and Tukey multiple comparisons tests (a=.05). RESULTS: The mean bond strength values (SD) in N for the experimental groups D100 (181.7 (55.3)) and D120 (210.7 (55.0)) were higher (P=.036 and <.001, respectively) than that obtained for the D90 control group (138.5 (49.2)). The lowest mean value was recorded for the D140 group (91.1 (36.0)). All experimental groups showed significantly different results, when compared to the control group. A multiple comparison between experimental groups showed significant differences (P<.001). Only the comparison between D100 versus D120 was not significant. CONCLUSIONS: Data suggest that the resin cement film thickness influences the pullout strengths of fiber-reinforced posts. For the selected quartz fiber-reinforced post and resin luting cement, the highest bond strength values were not obtained when the thinnest cement layer was tested (D90) but when oversized post spaces were used (D100-D120). However, when the cement film thickness was too great (D140), the dislocation resistance of fiber-reinforced posts was significantly decreased.     

SEM evaluation of the cement layer thickness after luting two different posts

PURPOSE: To verify with SEM the cement layer thickness and uniformity of resin-relined translucent fiber posts (anatomic posts) and standard translucent fiber posts. MATERIALS AND METHODS: On 20 extracted maxillary anterior teeth, the roots were endodontically treated and prepared for the insertion of a fiber post. Translucent fiber posts (DT) were luted with a dual-curing resin cement (Duo-Link) in 10 specimens (group 1) after the canal walls had been treated with the One-Step bonding system. In the other 10 specimens (group 2), experimental anatomic posts (Anatomic Post'n Core) were tested. To these posts, a layer of light-curing resin is added to allow for a pre-cementation relining of the post, aimed at improving its fit into the endodontic space. For luting, the same adhesive-resin cement combination of group 1 was used. All the roots were sectioned and prepared for SEM observations. At the 1-mm, 4.5-mm, and 8-mm level of each root, cement thickness was measured, and the presence of gaps or voids within the luting material or at its interfaces was evaluated. A statistical analysis was performed to test the significance of differences in the cement layer thickness around the two types of post and at different levels of the same type of post. RESULTS: In the presence of anatomic posts, the cement layer was significantly thinner and more uniform at the coronal and middle level of the root. In both groups, voids and bubbles were detected within the luting material, within the abutment material, and between fiber post and cement. Gaps were also visible between post and relining material. CONCLUSIONS: The resin cement thickness was significantly lower in the anatomic post group than in the control group (standardized posts), except at the apical third of the canal, where there was no statistically significant difference. A good adaptation of anatomic posts was evident in all of the specimens.     

Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements

Davis P, Melo LSD, Foxton RM, Sherriff M, Pilecki P, Mannocci F, Watson TF. Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Eur J Oral Sci 2010; 118: 197–201. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aims of this study were to evaluate the flexural strength of two different types of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Forty glass methacrylate‐based fibre posts (GC Fiber Post) and 20 glass fibre inter‐polymerizing network posts (everStick POST) were divided into three groups. Group 1 contained 20 GC posts that were bonded to a dual‐cure composite cement (UnifilCore). Group 2 contained 20 Stick Tech posts that had adhesive applied (Scotchbond Multipurpose resin) and were bonded to a dual‐cure composite resin cement (RelyX Unicem). Group 3 contained 20 GC posts that were pretreated with a silane‐coupling agent before being treated with resin and composite, as in group 1. A 4‐point bend test was carried out to failure on all of the groups. Failure modes were determined using scanning electron microscopy. Pretreatment of the post surface with the silane‐coupling agent did not increase the flexural strength. The flexural strength of the Stick Tech post was significantly lower than the flexural strength of the GC post. The mode of failure for the GC Posts was adhesive, whereas the Stick Tech posts failed cohesively. Different flexural strengths and failure modes were observed among the two fibre post–resin systems.     

INFLUENCE OF DIFFERENT ADHESIVE SYSTEMS ON THE PULL-OUT BOND STRENGTH OF GLASS FIBER POSTS

This in vitro study evaluated the tensile bond strength of glass fiber posts (Reforpost – Angelus-Brazil) cemented to root dentin with a resin cement (RelyX ARC – 3M/ESPE) associated with two different adhesive systems (Adper Single Bond - 3M/ESPE and Adper Scotchbond Multi Purpose (MP) Plus – 3M/ESPE), using the pull-out test. Twenty single-rooted human teeth with standardized root canals were randomly assigned to 2 groups (n=10): G1- etching with 37% phosphoric acid gel (3M/ESPE) + Adper Single Bond + #1 post (Reforpost – Angelus) + four #1 accessory posts (Reforpin – Angelus) + resin cement; G2- etching with 37% phosphoric acid gel + Adper Scotchbond MP Plus + #1 post + four #1 accessory posts + resin cement. The specimens were stored in distilled water at 37°C for 7 days and submitted to the pull-out test in a universal testing machine (EMIC) at a crosshead speed of 0.5 mm/min. The mean values of bond strength (kgf) and standard deviation were: G1- 29.163 ± 7.123; G2- 37.752 ±13.054. Statistical analysis (Student''s t-test; α=0.05 showed no statistically significant difference (p<0.05) between the groups. Adhesive bonding failures between resin cement and root canal dentin surface were observed in both groups, with non-polymerized resin cement in the apical portion of the post space when Single Bond was used (G1). The type of adhesive system employed on the fiber post cementation did not influence the pull-out bond strength.     

Comparison between two clinical procedures for bonding fiber posts into a root canal: a microscopic investigation

The purpose of this study was to evaluate the influence of two brushes used as carriers of a primer-adhesive solution as to the formation of resin tags, adhesive lateral branches, and a hybrid layer when used to bond translucent fiber posts. Twenty endodontically treated teeth, extracted for periodontal reasons, were used. The samples were randomly divided into two groups of 10 samples each (Group 1: Microbrush + Scotchbond 1 + Rely X ARC resin cement; Group 2: small plastic brush + Scotchbond 1 + Rely X ARC resin cement). The adhesive system and resin cement were used strictly following manufacturers' instructions. The priming-adhesive solution of the one-bottle system was light-cured before placing the resin cement and the post. Twenty translucent fiber posts were used. After luting procedures, root samples were processed for SEM observations. The adhesive system showed a resin dentin interdiffusion zone (RDIZ), resin tag, and adhesive lateral branch formation. Microscopic examination of restored interfaces of group 1 showed a higher percentage (p < 0.05) of RDIZ than those found in samples of group 2. In group 1 samples, RDIZ morphology was well detectable and uniform in all thirds of the root canals. In group 2, RDIZ was not visible in the apical third. No statistically significant differences were found among the two groups coronally and at the middle third, but the apical third of group 1 showed significantly more resin tag formation than group 2. The characteristic reverse cone shape of resin tags was always noted in the coronal and middle third of the root canals of both groups and in the apical third of group 1. In the apical third of group 2 root canals, the resin tags showed a less uniform morphology and a shorter length than those found in the other observed thirds.     

The effect of calcium silicate-based sealer on the push-out bond strength of fibre posts

Background: The aim of this study was to assess the effect of the iRoot SP root canal sealer on the push‐out bond strength of fibre posts cemented with self‐adhesive resin cement. Methods:  Forty‐eight extracted maxillary incisors were randomly divided into four groups according to the tested sealer (n = 12): group 1 – control (only gutta‐percha points, no sealer); group 2 – AH Plus Jet (resin‐based sealer); group 3 – Endofill (zinc oxide‐eugenol‐based sealer); and group 4 – iRoot SP (calcium silicate‐based sealer). All root canals were filled with gutta‐percha, and groups 2–4 additionally received one of the sealers. Fibre posts were cemented with the self‐adhesive resin cement Clearfil SA Cement. The specimens were sectioned in the coronal, middle and apical regions, producing three slices of 1 mm thickness. The push‐out test was performed. All data were submitted to ANOVA and Tukey tests (α = 0.05). Results:  No statistically significant differences were found between the control group, AH Plus Jet and iRoot SP (p > 0.05). The Endofill sealer showed significantly lower bond strength compared to the other sealers and the control group (p < 0.05). Conclusions:  The calcium silicate‐based sealer did not adversely affect the bond strength of the fibre posts cemented with self‐adhesive resin cement.