The effect of two root canal sealers on the retentive strength of glass fibre endodontic posts

This study was undertaken to examine the effect of eugenol-containing and non-eugenol-containing root canal sealers on the retention strength of glass fibre endodontic posts (ParaPost Fibre White) luted with a resin cement (ParaPost cement). We also examined the mode of failure that occurred visually by using scanning electron microscopy. Seventy-two single rooted, recently extracted, premolar teeth were root canal treated and randomly divided into two groups. Group 1 was obturated with gutta percha and a calcium hydroxide-based sealer (Sealapex, Kerr). Group 2 was obturated with gutta percha and a eugenol-based sealer (Tubli-Seal Kerr). The teeth were stored for 1 week in distilled water at 37 degrees C and then prepared for 9 mm posts with a 1.40-mm drill. The matching glass fibre post was luted with a resin cement following the manufacturer's instructions. The samples were stored for 1 week and thermocycled. The posts were removed from the root canals using a calibrated testing machine in tensile mode. The mean dislodging force for group 1 was 190.46 N and for group 2 was 183.8 N, with standard deviations of 54.9 and 56.0 N respectively. The t-test indicated no significant difference between the two groups. Failure of the posts occurred mainly within the resin layer. This study showed that under experimental conditions there was no statistically significant difference between Sealapex sealer and Tubli-Seal sealer on the retention of glass fibre posts using a resin cement.     

The use of reinforced composite resin cement as compensation for reduced post length

STATEMENT OF PROBLEM: Cements that yield high retentive values are believed to allow use of shorter posts. PURPOSE: This study investigated the use of reinforced composite resin cement as compensation for reduced dowel length. MATERIAL AND METHODS: The retention values of stainless steel posts (parallel-sided ParaPost and tapered Dentatus in 5-, 8-, and 10-mm lengths) luted with Flexi-Flow titanium-reinforced composite resin and zinc phosphate cements were evaluated. Single-rooted extracted human teeth with crowns (n = 120), removed at the cementoenamel junction, were randomly divided into 4 groups of 30 samples each. Different post lengths were luted with either Flexi-Flow or zinc phosphate. Each sample was placed into a specialized jig and on a tensile testing machine with a crosshead speed of 2 mm/min, applied until failure. The effect of different posts and cements on the force required to dislodge the dowels was evaluated with multiple analyses of variance (ANOVA). One-way ANOVA with Scheffé contrast was applied to determine the effect of different post lengths on the retentive failure of posts luted with the 2 agents. RESULTS: Flexi-Flow reinforced composite resin cement significantly increased retention of ParaPost and Dentatus dowels (P<.001) compared with zinc phosphate. One-way ANOVA revealed no statistically significant difference (P>.05) between mean retention of both dowels luted with Flexi-Flow for all posts length used (5 mm = 8 mm = 10 mm). Mean retention values of the groups luted with zinc phosphate showed a statistically significant difference (P<.001) for the different post lengths (10 > 8 > 5 mm). Parallel-sided ParaPost dowels demonstrated a higher mean retention than tapered Dentatus dowels (P<.001). CONCLUSION: In this study, Flexi-Flow reinforced composite resin cement compensated for the reduced length of shorter parallel-sided ParaPost and tapered Dentatus dowels.     

Effect of EDTA conditioning upon the retention of fibre posts luted with resin cements

Aim To determine if a final rinse with EDTA improves the short‐term in‐tooth retentive strength of adhesively luted fibre‐reinforced composite posts. Methodology Six different commercial fibre post systems were tested. Post spaces in extracted human anterior teeth were irrigated with either 6% NaOCl or 6% NaOCl followed by 17% EDTA. Posts were luted using the manufacturer’s recommended bonding agent and luting cement. Two different sizes of post were tested for each post system. After 24 h of storage, the retentive strength of the post to the tooth (14 per group, 336 total) was tested using a pull‐out technique. Three‐way anova and the Student–Newman–Kuels test were used to test the effects of irrigation regimen, post size and post brand on the retentive strength of the fibre post. Results Almost every sample failed at the interface between dentine and luting cement. Irrigation method did not have any significant effect (P > 0.14) for any group other than ParaPost Fibre White (P < 0.001). The overall retention of a post appeared to be correlated to the amount of surface texture on the post; the smooth ICEPost was the least retentive brand, the textured FibreKor and the ParaPost Fibre White posts were moderately retained, and the threaded Flexi‐Post Fibre and the Flexi‐Flange Fibre posts were the most retentive brands tested. For all brands, larger diameter posts were more retentive than smaller diameter posts (P < 0.008). Conclusions A final rinse of EDTA did not improve the short‐term retention of fibre posts except for ParaPost Fibre White.     

Retention of prefabricated and individually cast root canal posts in vitro

OBJECTIVES: The aim of the study was to evaluate the retention of prefabricated root canal posts made of a variety of materials that have recently been introduced into dentistry. MATERIALS AND METHODS: The posts studied were CosmoPost, Composipost carbon fibres, Composipost Aestheti-Plus, Composipost Light-Post and Para Post Fiber White. The posts were luted in extracted human premolars and the cores were built up with the resin composites recommended by the manufacturers. The retention of individually cast gold alloy posts luted with zinc-phosphate cement were used as reference. A universal testing machine was used to determine the retention of each cemented post Data were compared using ANOVA supplemented with Fisher's PLSD at a significance level of p < 0.05. RESULTS: Only the CosmoPost system exhibited retention values that were significantly lower than for the conventionally cast gold alloy posts luted with zinc-phosphate cement The force necessary to loosen the CosmoPost specimens was significantly less than that needed to loosen the Composipost. Estheti-Plus (p < 0.05) and the Composipost Ught-Post systems (p < 0.001]. The force necessary to loosen the ParaPost Fiber White specimens was significantly less than for the Composipost Light-Post system (p < 0.01). Other combinations did not differ significantly (p > 0.05). CONCLUSIONS: When zirconium oxide ceramic posts are luted with resin composites the bonding between the ceramic and resin composite seems to be weak. Further studies are thus necessary to achieve improved retention of all-ceramic root canal posts.     

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.     

Effect of surface treatment on retention of glass-fiber endodontic posts

STATEMENT OF PROBLEM: The effects of surface treatment on the retention of prefabricated fiber-reinforced epoxy resin posts are not well understood because most studies measure retention shortly after cementation, without artificial aging. PURPOSE: The purpose of this study was to evaluate the effect of surface treatment on the retention of glass-fiber endodontic posts luted with resin cement and subjected to artificial aging. MATERIAL AND METHODS: Thirty-two single-rooted teeth were selected, the coronal aspect of each tooth was removed, and the remaining root received endodontic therapy. Specimens were then divided into 4 groups (n = 8). Post spaces were prepared to a depth of 10 mm by using ISO 90 rotary instruments. The tapered posts received 1 of 4 surface treatments: cleaning with alcohol (Alc), cleaning with alcohol and conditioning with ED-Primer material (Alc-ED), airborne-particle abrasion (Air), or airborne-particle abrasion and conditioning with ED-Primer material (Air-ED). All posts were luted with a composite resin luting agent (Panavia F) after conditioning the canal dentin with autopolymerizing dentin primer (ED-Primer) and without acid etching of the canal dentin. After cementation, the specimens were stored in water at 37 degrees C for 30 days and subjected to simulated aging conditions consisting of 7500 thermal cycles (5 degrees C/55 degrees C) and 300,000 mechanical loading cycles with 30 N. Retention (N) of the posts was measured with a universal testing machine with a crosshead speed of 2 mm/min. The data were analyzed using 1-way ANOVA and the Tukey HSD test (alpha = .05). The dislodged posts were also examined microscopically at x8 and x20 magnification to evaluate the mode of failure. RESULTS: The mean retentive values (N) and SDs of the test groups were as follows: Alc, 375.9 +/- 85.0; Alc-ED, 421.2 +/- 46.8; Air, 534.8 +/- 65.8; and Air-ED, 555.8 +/- 86.9. Airborne-particle-abraded posts had significantly higher retention compared with nonabraded posts (P < .001). Treating the post's surface with ED-Primer material prior to cementation had no significant effect on retention. The failure mode was purely adhesive at the resin cement-post interface for all nonabraded posts. A mixed failure mode, adhesive at the resin cement-dentin interface, at the resin cement-post interface, and cohesive in the resin cement, was observed for airborne-particle-abraded posts. CONCLUSION: Treating the surface of the posts with ED-Primer material before cementation with Panavia F cement produced no significant improvement in the retention of the posts. Airborne-particle abrasion of the surface of the post significantly improved the retention.     

Resistance to cyclic loading of teeth restored with posts

This in vitro study evaluated the effect of presence of post, presence of core, and of shape, type, and surface treatment of posts on resistance to cyclic loading of crowned human teeth. For all teeth, crowns designed without ferrule were cast in sterling silver and luted with resin cement (Panavia F). Each tooth underwent cyclic loading of 600 N at two loads per second until failure. Teeth that had only been crowned showed significantly higher resistance to cyclic loading than teeth with cores or with post and cores. No significant differences were found between teeth restored with cores only or with post and cores, irrespective of surface-treatment of the posts. Teeth restored with parallel-sided cast post (ParaPost XP) and cores showed significantly higher resistance to cyclic loading than teeth with either tapered cast posts or untreated prefabricated posts of titanium alloy (ParaPost XH) or glass fiber composite (ParaPost Fiber White). No significant difference was found between teeth restored with parallel-sided cast post and cores and teeth restored with untreated prefabricated posts of zirconia (Cerapost). Surface treatment of posts significantly increased the resistance to cyclic loading compared with untreated posts. When posts are used, surface treatment is recommended.     

Influence of endodontic post type (glass fiber, quartz fiber or gold) and luting material on push-out bond strength to dentin in vitro.

OBJECTIVES: To determine the influence of post type and luting material on bond strength to dentin. METHODS: The root canals of extracted human upper central incisors were instrumented and post space was prepared using the respective drills for each post system. Glass fiber posts (Luscent Anchor, Dentatus [LA]) were luted using three dual-curing adhesive systems (Excite DSC/Variolink II, Vivadent [VL2]; EnaBond/EnaCem, Micerium [ENA]; Prime & Bond NT/Calibra, DentSply DeTrey [CAL]). A different brand of glass fiber post (EasyPost, DentSply Maillefer [EP]) and quartz fiber post (DT Light Post, VDW [DT]) were luted using CAL. Gold posts (Perma-dor, VDW) were luted either adhesively following tribo-chemical silicate coating (Rocatec, ESPE-Sil, 3M ESPE; CAL) or conventionally using glass ionomer cement (Ketac Cem, 3M ESPE). Three slices of 2mm height were cut perpendicular to the post from each restored root. Bond strength was determined by pushing out the post using a universal testing machine (/1449, Zwick). RESULTS: For all experimental groups combined, bond strength increased from the coronal to the apical section (Friedman test: P<0.001). Significant differences were observed among the fiber posts (DT/CAL>LA/CAL; Mann-Whitney U-test with Bonferroni-Holm adjustment: P<0.05; EP/CAL ranging in between) but not among luting materials (LA/VL2, LA/ENA, LA/CAL: n.s.). The gold posts were equivalent to DT/CAL with both luting procedures. SIGNIFICANCE: Selection of post type may be more important for bond strength than luting material. Bond strength of fiber posts was equivalent but not superior to adhesively or conventionally luted gold posts.     

Effect of eugenol-containing endodontic sealer on retention of prefabricated posts luted with adhesive composite resin cement.

Reported studies have implicated eugenol in the reduction in retention of restorations luted with chemically cured composite resin cement. This study investigated the effect of residual eugenol in the root canal on the retention of ParaPost dowels cemented with Panavia EX composite resin. An attempt was also made to identify and to determine the most effective cleansing procedure. Findings of this study demonstrated a substantial decrease in retention of posts luted with Panavia composite resin cement in the presence of eugenol. Irrigation with ethyl alcohol (ethanol) or etching with 37% phosphoric acid gel was found to be effective in restoring the resistance to dislodgment of the posts, but alcohol produced the most consistent and reliable results.     

The retentive effects of pre-fabricated posts by luting cements

The purpose of this study was to compare the retention of two different pre-fabricated posts cemented to the root canal with four different adhesive luting cements and a zinc phosphate cement. The crowns of 100 freshly extracted human mandibular central and lateral incisors were removed at the cementoenamel junction and divided into two main groups (A = ParaPost and B = Flexi-Post) and further divided into five subgroups to evaluate the effects of five different cements (Rely-X ARC, Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor) each with 10 samples. Post-holes were prepared on all of the roots following the manufacturer's instructions. Each sample was placed into a specialized jig and tensile strength tests performed by using testing machine with a crosshead speed of 0.638 cm min(-1) and force applied until failure. The data were analysed with one-way anova (Post Hoc a Scheffe's S test) and two-way anova (P < 0.001). The Flexi-Post dowels had a mean of 54.21 kg (s.d. = 9.37) and demonstrated statistically higher retention than ParaPost dowels with a mean of 33.93 kg (s.d. = 10.69) for all of the cement groups (P < 0.001). In Flexi-Post and ParaPost dowel groups; Rely-X ARC was statistically higher than the Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor (P < 0.05). Adhesor was significantly lower than the other subgroups (P < 0.05). Resin luting cements have demonstrated very high tensile strength potential for a strong bond to dentin.     

Evaluation of pre-fabricated root canal posts

In this in vitro study, properties of a titanium alloy post recently introduced to the market (IntegraPost), were compared with those of a clinically proven stainless steel post (ParaPost). The IntegraPost has a unique, perforated, spherical head and a microknurled shank surface. The posts were tested for rigidity, for retention within the root canals of extracted teeth and for ability to retain composite resin cores. The two post types exhibited similar properties in core and root canal retention, however, the IntegraPost was significantly less rigid than the ParaPost.     

五种纤维桩/Panavia F粘接剂/牙本质之间微观机械固位研究

目的通过微拉伸实验和粘接界面的扫描电镜观测,研究五种纤维桩的桩核材料/粘结剂/牙本质之间的微观机械固位强度与形态。方法五种纤维桩：NTI-Kahla Fiber,Twin Luscent Anchors,Tenax Fiber White,PD Tapered Crown Post和Ouya FiberⅠ型。每组10支纤维桩,使用Panavia F粘结至经过常规根管充填和桩核修复根管预备后的下颌前磨牙根管内,其中5个样本扫描电镜下观测纤维桩/粘结剂/牙本质之间结合界面形态,另5个样本进行微拉伸实验,并进行断面观测。结果扫描电镜观测到五种纤维桩的桩核材料/粘结剂/牙本质之间存在相似的微观嵌合形态,微拉伸实验中断裂主要发生在纤维桩材料/粘接剂界面,微拉伸强度值NTI-Kahla Fiber为14.33±5.74Mpa,Twin Luscent Anchors为13.48±8.22Mpa,Tenax Fiber White为13.21±7.54Mpa,PD TaperedCrown Post为12.95±6.57Mpa,Ouya FiberⅠ为13.59±6.31Mpa,各组间无统计差异（P〉0.05）。结论Panavia F树脂粘接剂可以建立与牙本质及纤维桩材料之间的良好连接,五种纤维桩与Panavia F粘结剂及牙本质之间的微观机械固位形态与强度相近。微拉伸断裂模式提示在纤维桩修复中,纤维桩/粘接剂界面是修复体粘接的主要薄弱环节。     

Retention of cast posts cemented with zinc phosphate cement using different cementing techniques

PURPOSE: This study compares the effect of different cementation techniques on the retention of cast posts and cores. MATERIALS AND METHODS: Twenty-four extracted single rooted human teeth were used in this study. After routine preparation of the root canals, the canal space was enlarged with reamers. Direct post patterns were made with acrylic resin. Castings were fabricated using Ni-Cr-Mb alloy. Zinc phosphate cement was used as a luting agent using 4 different methods of cement introduction to the root canal space. This created 4 treatment groups consisting of 6 teeth in each group. In Group A, the cement was applied over the posts only. For the specimens in Group B, the cement was introduced into the root canals with a spiral filler and applied over the posts. In Group C, cement was injected into the root canals and then applied over the posts. Finally, for the specimens in Group D, cement was injected into the root canals and a spiral was used to spread it into the root canals, and cement was also applied over the posts. After cementation, teeth were stored in saline solution. The tensile retentive force of cast posts was evaluated using the Instron testing machine (Instron, Canton, MA). RESULTS: The retention obtained by the 4 techniques differed significantly (p <.05). The highest tensile force to post dislodgment was observed in Group D, and the least was in Group A. Analysis of variance test revealed a highly significant difference between groups (p <.0001). According to the Fisher exact test, there was a significant increase in retention from Group A to Group D (p <.05). CONCLUSIONS: Under the conditions of this study, the injection of cement into a root canal space followed by the use of a spiral resulted in the highest level of post retention. Retention was reduced when cement was placed using a Lentulo spiral alone (Kerr/Sybron Corp, Romulus, MI), a Jiffy tube (Teledyne Water Pik, Allegheny Teledyne Co, Fort Collins, CO) alone, or by application to the post only. J Prosthodont 2001;10:37-41.     

Influence of luting agent translucency on fiber post retention

The aim was to assess the influence of cement translucency on the retentive strength of luted fiber posts. Twenty extracted human premolars were randomly divided into four equal groups, based on the combinations of materials to be tested. Two post types of the same size, shape, and chemical composition, but different light‐transmission properties [Translucent post (TP) and Opaque post (OP)] were selected. The two post types were luted using the etch‐and‐rinse, light‐curing adhesive in combination with two shades of the same resin cement of markedly different light‐transmitting ability [Transparent shade (TS) and Opaque shade (OS)]. Early post retention was assessed using the thin‐slice push‐out test. Post type did not significantly influence post retention; however, cement translucency emerged as a relevant factor in intraradicular cementation, with the TS achieving higher push‐out strengths. The between‐factor interaction was also statistically significant; specifically, OP‐OS yielded significantly lower retentive strengths than all the other groups. Post translucency did not influence post retention, provided that a highly translucent cement was utilized for luting.     

Microhardness of different resin cement shades inside the root canal

Objectives: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material. Study Design: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X°Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core°X flow. All materials were applied according to manufacturers' instructions and were all photopolymerized (Bluephase LED unit, Ivoclar Vivadent, 40s). After 24 hours, roots were transversally cut into 9 slices 1 mm thick from the coronal to apical extremes, three corresponding to each root third. Then, VHNs were recorded (100gf, 30 s) on the resin luting materials along the adhesive interface in all sections. Data were analyzed by two-way ANOVA and SNK tests (α=0.05). Results: A significant influence on microhardness of resin luting material in their respective shades (p<0.0001), root third (p<0.0001) and interactions between them was detected (p<0.0001). RelyX Unicem cement showed the highest microhardness values and Calibra the lowest, regardless of the shade selected. All resin luting materials tested exhibited a significantly higher microhardness in the cervical third. Conclusions: Microhardness of resin luting agents tested inside the canal is dependent on material brand and resin cement shade seems to be a less relevant factor. Microhardness decreased along the root canal, regardless of the shade selected.     

Effectiveness of bonding fiber posts to root canals and composite core build-ups

This study investigated the effects of fiber posts, silanization, and luting agents on the interfacial strength to root dentin and composite cores. Root canals of 120 crownless human teeth were instrumented. Three different posts (opaque and translucent), with and without silane treatment, were bonded using etch-and-rinse, self-etch, and self-adhesive luting agents. The restored roots were built up with dual-curing composite. After storage in water for 24 h at 37°C, 2-mm-thick slices were cut from each sample: one from the composite core and one from the restored root. Interfacial push-out bond strengths of the posts were determined in a universal testing machine. Failure modes were analyzed using scanning electron microscopy. The post type and the luting agent had significant effects on both the post-to-dentin and post-to-core strengths. Silanization did not significantly influence post-to-dentin strengths, but enhanced post-to-core strengths. With etch-and-rinse luting agents, debonding occurred predominantly between the post and the cement, while the self-etch and self-adhesive luting agents showed more failures on root dentin. No failures occurred between the composite core and the cement. The combination of translucent posts and etch-and-rinse dual-curing luting agents can positively influence the retention of fiber posts in root canals. Silanization seems to be less relevant for intra-root canal bonding, but may have beneficial effects on post-to-core strengths.     

Retention of serrated endodontic posts with a composite luting agent: Effect of cement thickness

When Prosthodent composite was used as a cementation material for endodontic posts (ParaPost), adaptation of the post to the canal was not crucial. Changes of the composite layer thickness up to 500 microns did not decrease retention. Variation in the diameter of the posts did not effect the retention. The retention obtained for the combinations of posts and cements was high and suitable to resist dislodgment of the posts. Consequently, the thinnest post in the root canal, cemented with a composite is recommended. Thus the removal of tooth structure is unnecessary because the cylindrical preparation is formed in the composite.     

Influence of fatigue loading on four post-and-core systems in maxillary premolars.

OBJECTIVE: Clinical studies show a high failure incidence after years of service of endodontically treated premolars, when restored with post-core crowns, especially those with short posts or deficient ferrules. The reason for this can be a deterioration of the luting cement around the post by fatigue from functional loading. In particular, the anatomy of premolars may frequently be incompatible with the application of long endodontic posts. The aim of this study was to evaluate the influence of fatigue loading on the quality of the cement layer between posts with restricted lengths and the root canal wall in premolars. As the stiffness of posts may affect the outcome, post-and-core systems with varying post stiffness were selected. METHOD AND MATERIALS: Four types of post-and-core systems were selected for this study: three prefabricated post systems combined with a resin composite core material and one cast post and core. The three prefabricated posts were titanium posts (Tenax), quartz-fiber posts (Aestheti-Post), and quartz-coated-carbon-fiber posts (Aestheti-Plus). The post-and-core restorations were made on single-rooted, human, maxillary premolars from which the coronal sections were removed at the level of the proximal cementoenamel junction. Following endodontic treatment, a cast post and core (post length 6 mm) was prepared for each tooth individually (direct method) and cemented into the root canal with chemical cure Panavia 21 TC. The prefabricated posts were directly cemented in the root canal and then, after applying a dual-cure adhesive (Clearfil Photobond), built up with a core build-up composite (Clearfil Photocore). For each group (n = 8), half of the specimens were exposed to fatigue loading (10(6) load cycles) almost perpendicular to the axial axis (85 degrees), while the other half was used as the control. Three parallel, transverse root sections of 1.5-mm thickness, were cut from each specimen. These sections were examined by scanning electron microscopy (SEM) to evaluate the cement integrity, while the retention strength of the cemented post sections was determined with a push-out test. RESULTS: Fatigue loading did not cause separation of the buildups from the roots or affect the push-out strength. On a univariate level, only SEM evaluation showed significant differences between the types of post, fatigue loading, and between the levels of root sections. The cement integrity with the titanium post was significantly less than with the other three systems, which did not differ among themselves. The differences could not be explained by differences in stiffness between the posts. CONCLUSION: A composite core build-up material bonded to the dentin and supported by quartz-fiber posts or quartz-coated-carbon-fiber posts, cemented with adhesive cement like Panavia 21 TC, may be a viable alternative for the conventional cast core.     

Effect of circumferential undercut placement in the root canal wall on the retention of a tapered post in large and small root canals

OBJECTIVES: This study examined the influence of root canal space and circumferential undercut placement in the dentine wall on the retention of a prefabricated Root Keeper post. METHODS: Twenty-four extracted single-rooted teeth, having narrow root canal spaces, were decoronated, treated endodontically, and then centrally embedded in resin blocks. All canal spaces were prepared with a no. 2 Peeso reamer to an 8mm depth, and half the specimens were successively treated with a no. 3 Peeso to depths of 5 and 8mm for the small canal group (SC) and large canal group (LC), respectively. An L-type keeper post (Aichi Steel Co.) was luted to each canal with resin cement. The assembly was thermocycled 2000 times (4-60 degrees C), and post retention was measured. Afterwards the dislodged post with the intact structure was sandblasted, and the canal was cleaned and slightly undercut using an inverted cone bur. Six treated posts were recemented for both grooved large canal (GLC) and grooved small canal (GSC) groups, and the repaired retentive strengths were measured. RESULTS: Keeper posts cemented in SC (84.26+/-31.85N) showed better (p<0.05) retention than those cemented in LC (41.92+/-22.36N). Interestingly, the repaired strengths of the recemented post increased in both GSC (104.29+/-11.89N) and GLC (96.65+/-6.91N). All posts, except for one in the GLC, failed at the keeper-post joint. CONCLUSIONS: Prefabricated Root Keeper posts had lower retentive strength in roots with a large canal space. Placement of a circumferential undercut in the root canal wall significantly enhanced the retention of the short tapered posts.     

Fracture resistance of endodontically treated teeth restored with composite posts

STATEMENT OF PROBLEM: The most recent application of fiber-reinforced composites involves their use as post and core systems to restore endodontically treated teeth. Even though this last application has been advertised and used clinically by many dentists, there is very little information regarding the physical properties of these post systems. PURPOSE: The purpose of this study was to compare the effect of 3 fiber-reinforced composite post systems on the fracture resistance and mode of failure of endodontically treated teeth. MATERIAL AND METHODS: Ninety maxillary central incisors were divided into 8 experimental groups and 1 stainless steel (ParaPost) control group of 10 specimens each. Eighty teeth were assigned to 2 main experimental groups called "narrow" and "flared" canals. For the narrow canal group, post spaces were prepared with the corresponding reamer to restore the teeth with FibreKor, Luscent anchors, and Ribbond posts of 1.5 mm, 1.6 mm, and 2.0 mm in diameter, respectively. For the flared canals group thin-walled canals were simulated. Teeth for the flared canals were restored with the same posts but were cemented into tapered 2 mm wide canals created with a tapered diamond bur. Prefabricated posts (FibreKor and Luscent anchors) for narrow and flared canals were cemented with an autopolymerized resin cement and a flowable composite, respectively, whereas customized Ribbond posts were luted with a light-polymerized flowable composite for both canal types. An additional set of 20 Ribbond posts with coronal portions of variable size and shape referred to as "Ribbond nonstandardized" were also prepared and evaluated. Specimens were loaded to failure (kg) with a universal testing machine at a crosshead speed of 0.05 cm/min until failure occurred. Data were analyzed with analysis of variance and Student t tests (P<.05). RESULTS: Statistical analysis revealed no significant difference between flared and narrow canals in mean load to failure between the post systems except for the Ribbond posts (P<.01). For the narrow canal, the mean load ranged from a low of 4.55 (+/-1.49) kg for the Ribbond standard to a high of 12.9 (+/-1.64) kg for the Luscent anchors. For the flared canal the low mean was 9.04 (+/-1.76) kg for FibreKor and the high was equal for both Luscent anchors and Ribbond standard, 12.87 (+/-2.69) and 12.87 (+/-3.54), respectively. Overall, the ParaPost control group had the highest load value (18.33 +/- 3.27 kg) (P<.05). Ribbond nonstandardized had a mean load to failure of 24.91 (+/-11.53) Kg for the narrow canal group and 31.95 (+/-11.98) kg for the flared canal. Results from these groups were excluded from the statistical analysis because of the uncontrolled core sizes and high standard deviations. No root fractures occurred in any of the experimental groups. CONCLUSION: Results from the study show that the load to failure of the stainless steel posts were significantly stronger than all the composite posts studied. However, the mode of failure or deflection of the fiber-reinforced composite posts is protective to the remaining tooth structure.