Fracture resistance of endodontically treated premolars with fibre-reinforced composite restorations

This study investigated the fracture resistance and failure mode of endodontically treated premolars restored with a glass fibre-reinforced composite resin. Endodontically treated maxillary premolars were divided in 4 groups: group O: occlusal access opening restored with direct composite; group O+: as group O but with fibre reinforcement; group MOD: occlusal access opening and mesio-distal (MOD) cavity restored with direct composite; group MOD+: as group MOD but with additional fibre reinforcement. Pairwise comparisons of the fracture force among all groups was performed (95% confidence level). Fractures were classified in 4 groups depending on the type of fracture. Group O was the strongest (452.7N) and group MOD the weakest (292.4N). Fracture resistance was significantly different among all groups, except between groups O+ and MOD+. The majority of the unreinforced teeth displayed unfavourable fractures, while the reinforced teeth displayed more favourable fractures. The incorporation of glass fibre weakened endodontically treated but otherwise intact premolars; premolars with MOD restorations were stronger if reinforced with fibres. Fibre reinforcement led to more favourable fractures.

Effect of bonded area and/or fiber post placement on the fracture strengths of resin-core reconstructions for pulpless teeth

PURPOSE

To compare the fracture strengths of pulpless teeth restored using resin cores with and without fiber posts, and with and without bonding adhesive in the post cavity.

METHODS

Human extracted roots were prepared with post cavities and divided into four experimental groups: Groups 1 and 2--after application of adhesive to both the top surface of the root and the inner surface of the post cavity, DC core Automix was injected into the post space with or without fiber-post placement; Groups 3 and 4--adhesive was applied to the top surface of the root only, with or without post placement. Resin-cores were then built-up. Teeth prepared for full crowns served as controls. After water storage at 37 degrees C for 24 hours, the all specimens were embedded in acrylic resin at 2 mm below CEJ, and loaded at 45 degrees to the long axis of the tooth using a universal testing machine until fracture. The data were analyzed by one-way ANOVA (alpha = 0.05).

RESULTS

The fracture loads were, Group 1: 1832 +/- 240 N, Group 2: 1815 +/- 347 N, Group 3: 1626 +/- 396 N, Group 4: 1810 +/- 332 N, Control Group: 1622 +/- 274 N. There were no significant differences among all the groups (P > 0.05).

Clinical evaluation of bonded amalgam restorations in endodontically treated premolar teeth: a one-year evaluation

AIM

The aim of this clinical study was to compare the fracture resistance, marginal adaptation, and rate of recurrent caries of bonded and nonbonded amalgam restorations in endodontically treated premolar teeth.

METHODS AND MATERIALS

A total of 36 patients with endodontically treated maxillary first or second premolars were selected and divided into three groups. The treatments in all groups consisted of lingual cusp coverage and cementation of a prefabricated intracanal post (No. 2 long, Dentatus USA, New York, NY, USA). One type of cavity liner was used for each group as follows: copal varnish (Group A), Amalgambond Plus (Group B), and Scotchbond Multi-Purpose (Group C). The teeth were then restored with Cinalux high-copper spherical amalgam (Cinalux, Sh. Dr Faghihi Dental Co., Tehran, Iran). After one year, fracture resistance, marginal adaptation, and secondary caries were evaluated. Fischer's exact test was used for statistical analysis using a 0.05 percent significance level.

RESULTS

There was no significant difference among groups with respect to fracture resistance (p=0.49). However, significant differences in marginal adaptation existed among the three groups (p=0.02) and no recurrent caries were found in any of the restored teeth.

CONCLUSION

Bonding amalgam restorations using Amalgambond Plus and Scotchbond Multi-Purpose Plus did not improve the fracture resistance or affect the resistance to secondary caries in endodontically treated premolar teeth. However, the teeth in both these bonded groups showed significant improvement in marginal adaptation compared with restorations placed with copal varnish (p=0.02).

CLINICAL SIGNIFICANCE

Amalgambond Plus or Scotchbond Multi-Purpose adhesive resins significantly improved marginal adaptation of amalgam compared with copal varnish, but did not enhance fracture resistance or affect the prevention of secondary caries.

Resin composite polyethylene fiber reinforcement: effect on fracture resistance of weakened marginal ridges

PURPOSE

To investigate the in vitro effect of polyethylene woven fiber reinforcement of resin composite on the fracture resistance of weakened marginal ridges in molar teeth.

METHODS

50 sound extracted human mandibular molars were used. Specimens were divided into five groups (n = 10). Group 1: served as a control for comparison; Group 2: Class I cavity preparation with resin composite (Prodigy); Group 3: Class I cavity preparation with polyethylene ribbon fiber (Ribbond) and resin composite. Group 4: Class II cavity preparation with resin composite restoration; Group 5: Class II cavity preparation with polyethylene woven fiber and resin composite. Specimens were stored in 100% humidity at 37 degrees C for 7 days. Compressive loading of the teeth was performed with a universal testing machine at a cross-head speed of 0.5 mm/minute until failure. The data were analyzed with 1-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch Multiple Range Test (alpha = 0.05).

RESULTS

Reinforcement with polyethylene fiber resulted in significant differences for fracture resistance (P < 0.001). Mean fracture resistance (SD) was [1737.4 (84.8) N] for control group. Among the experimental groups, the highest mean fracture resistance (SD) [1543.8 (71.1) N] was associated with Class I cavity preparation with polyethylene fiber and resin composite. The lowest mean fracture resistance (SD) [869.2 (91.7) N] was recorded for Class II cavity preparation with conventional resin composite.

Tooth fragment reattachment through the use of a nanofilled composite resin

AIM

The purpose of this study is to evaluate resistance to fracture with static tests of dental fragments reattached through the use of different light-curing composite resins. For this purpose 40 bovine inferior incisors were utilised, which were randomised into 4 groups; one control group and 3 experimental groups.

MATERIALS AND METHODS

All teeth of the 3 experimental groups were sawed at 3 mm from the incisal margin, and the respective fragments were then reattached utilizing different composite resins: in group 2_EI the hybrid composite Tetric EvoCeram (Ivoclar Vivadent AG) was used, in group 3_ZI the hybrid composite FiltekTM Z250 (3M ESPE) was used, and in group 4_SN the nanofilled composite FiltekTM Supreme (3M ESPE) was used. After reattachment, on each tooth were performed a chamfer on the buccal surface and an overcontour on the lingual surface along the fracture line, which were then filled with the composite resin corresponding to the respective group. Finally, all teeth were embedded in plaster blocks, and a force was applied on the buccal surface.

RESULTS

All teeth in groups 2, 3, and 4 showed a significant loss of resistance to fracture compared to the teeth of the control group (P<0.0001). Resistance to fracture of the teeth belonging to groups 2_EI and 3_ZI was 37.35% and 47.35% of that of intact teeth respectively; in group 4_SN resistance to fracture reached 60.05%. Teeth of group 2 exhibited values of resistance to fracture statistically significant from those of group 4 (P=0.024), but no difference was found between group 2 and group 3 (P=0.298). The difference in resistance between group 3 and group 4 was not statistically significant (P=0.199).

CONCLUSION

Static test showed that reattachment of coronal fragments do not restore resistance to fracture to the value of intact teeth. Resistance to fracture in in vitro studies is influenced by the type of composite resin utilised.

Zirconia ceramic post systems: a literature review and a case report

Cast metal post-core systems have a long history of successful use because of their superior physical properties. However, their high elastic modulus can cause stress concentrations within the surrounding radicular dentin, resulting in root fractures. Moreover, the increasing demand for more esthetically appealing and biocompatible restorations has led to the development of tooth-colored, translucent, metal-free post-core systems. Notably, prefabricated zirconia ceramic post systems have been introduced to satisfy this trend toward a heightened awareness of esthetics, whereby the translucency of all-ceramic crowns can be successfully maintained with the use of ceramic post-core materials. Owing to the keen interest in and widespread use of zirconia ceramic post systems, many in vitro studies on zirconia posts have been published in the last 15 years. The aim of this article was to present data about the retention, fracture resistance, microleakage, light transmission, esthetic advantages, and radiodensity of zirconia posts. Two clinical survival rate studies were also presented. Based on the results of these studies, zirconia posts have been shown to improve the esthetic quality of all ceramic crowns and thus their usage is recommended. Apart from literature review, a case report in which a fractured fiber post was replaced with a custom-made zirconia post was also presented.

Effect of different onlay systems on fracture resistance and failure pattern of endodontically treated mandibular molars restored with and without glass fiber posts

PURPOSE

To investigate the relationship between post and core build-up materials on the fracture resistance of endodontically treated teeth restored with different onlay restorations.

METHODS

60 mandibular molars were endodontically treated and divided into three experimental groups that received one of the following onlay restorations: gold onlays, glass ceramic onlays (Empress I), or resin composite onlays (Gradia). Half of the specimens in each group received a fiber post (n=10). Two controls groups (n=10) were included: one group composed of sound mandibular molars, and the second group was composed of endodontically treated unrestored molars. Fracture tests were carried out by applying axial load using a universal loading machine until fracture. All fractured specimens were fractographically examined using a scanning electron microscope (SEM). Data were analyzed using two-way ANOVA and Tukey multiple comparison tests (alpha=0.05).

RESULTS

Statistical analysis showed that restoration of endodontically treated teeth with gold onlays improved fracture resistance when compared to glass ceramic or resin composite onlays. The presence of a fiber post significantly improved (P<0.045) fracture resistance of gold onlays from 2271 to 2874N while it did not influence the performance of the other two groups. Fractographic analyses revealed that the presence of fiber post resulted in more restorable fractures due to better stress distribution of the applied load. All onlay systems resulted in significant improvement of the fracture resistance compared to unrestored teeth (711N) but neither of them resulted in restoring the fracture resistance to match that of sound teeth (3212 N).

Influence of cavity design and restorative material on the fracture resistance of maxillary premolars

This study sought to evaluate how the type of cavity preparation and indirect restorative material affected the fracture resistance of maxillary premolars. Teeth were divided into seven groups (n = 14) according to the cavity preparation design (inlays, partial onlays with palatal canine coverage, and total onlays with coverage of both canines) and restorative material used. After the teeth were prepared, restorations were manufactured using a ceramic or a composite resin and cemented with a resin-based cement, with the exception of a control group consisting of sound premolars with no preparation. Fracture resistance was assessed using a universal testing machine with a 9 mm steel ball at a speed of 0.5 mm/minute until fracture. ANOVA results showed significant differences between restorative materials and types of preparations (p < 0.05). Cavity design did not affect composite resin restorations, while ceramic restorations with partial and total canine coverage presented the lowest fracture resistance values (p < 0.05). Within the limitations of this study, the authors concluded that indirect composite resin restorations offered better performance than ceramic restorations, regardless of the cavity design.

Fracture resistance of teeth obturated with RealSeal using two different chelating agents: an in vitro study

OBJECTIVES

The aim of this study was to evaluate the fracture resistance of endodontically treated teeth filled with a resin-based obturation material using two different chelating agents.

METHODS AND MATERIALS

Forty extracted single-canal human teeth were prepared, instrumented, and randomly divided into three groups: Group 1 (n=15) received a final flush with 10 ml of neutralized 17% EDTA, followed by 10 ml of sodium hypochlorite (NaOCl), then obturated using lateral condensation with RealSeal. Group 2 (n=15) received a final flush of BioPure MTAD, followed by 10 ml of NaOCl, then obturated using lateral condensation with RealSeal. Group 3, the control group (n=10), was instrumented but not obturated, then the root canal opening was sealed with a temporary filling material. The specimens were stored in 100% humidity for 10 days, mounted in polyester resin, and loaded to failure.

RESULTS

The ANOVA revealed a significant difference between the control group and the experimental groups, although there was no statistically significant difference between Group 1 and Group 2 (p=0.05). The MTAD group displayed higher mean fracture load values than the EDTA group.

CONCLUSIONS

It can be concluded that filling the root canals with RealSeal increased the in vitro resistance to fracture of single-canal extracted human teeth when compared to instrumented and unobturated teeth. Teeth treated with MTAD demonstrated high fracture-resistance values when compared to teeth treated with 17% EDTA, but they were not statistically significant.

CLINICAL SIGNIFICANCE

Filling the root canals with RealSeal with increased bonding to roots will increase resistance to fracture of these teeth.

Resistance to fracture of mandibular premolars restored using post-and-core systems

OBJECTIVE

To assess the influence of post-and-core systems on the resistance to fracture of mandibular premolars restored with metal crowns and a 2.0-mm cervical ferrule.

METHOD AND MATERIALS

Forty extracted premolars were selected and divided into 4 groups of 10 teeth each. Samples were sectioned 2.0 mm coronal to the CEJ. Following canal preparation, four restorative treatments were performed: group 1, post and core cast in type IV gold alloy; group 2, prefabricated titanium post with composite resin core; group 3, prefabricated quartz-fiber post combined with composite resin core; and group 4, composite resin core without post. Posts (groups 1, 2, and 3) were cemented with resin cement. Metal crowns were fabricated using nickel-chromium alloy. Specimens were placed in acrylic resin blocks and filled up to 2.0 mm apical to the CEJ. Fracture resistance was assessed by applying a continuous compressive force on the buccal cusp of the crowns at a 45-degree angle until fracture. Results were analyzed using ANOVA and Tukey multiple comparison test at a significance level of 5%.

RESULTS

Mean loads at fracture were as follows: group 1 = 1,189.23 N, group 2 = 1,816.43 N, group 3 = 1,224.51 N, and group 4 = 2,010.63 N. Groups 2 and 4 presented statistically similar results; the same was observed in groups 1 and 3. However, groups 2 and 4 presented significantly better results than groups 1 and 3.

CONCLUSION

Restoration of mandibular premolars with composite resin core (without post) showed an increased resistance to fracture when compared with other post-and-core systems whenever a minimum of 2.0 mm of remaining tooth structure was covered with a full metal crown (ferrule effect). Preservation of tooth structure was the most important factor in tooth resistance.

Effect of ferrule placement on the fracture strength of cyclically loaded bovine teeth restored with cemented cast post-cores and crowns

This experiment investigated the effect of a ferrule on the strength and fracture resistance of bovine teeth restored with cemented cast post-cores and crowns, compared to crowns alone or to crowns over non-ferrule cores. Thirty restored bovine teeth were subjected to 4 x 1095) cycles from 20 N to 120 N at 10 Hz, followed by fracture testing. Crowns alone were weaker than post restored teeth. There was no difference in fracture strength between ferrule and non ferrule teeth restored with crowns. All of the fractured teeth were subsequently unrestorable.

CONCLUSIONS

Fracture resistance was not enhanced by 2 mm ferrule height.

Effect of posts on the fracture resistance of load-cycled endodontically-treated premolars restored with direct composite resin

AIM

The aim of this study was to investigate the fracture resistance and failure mode of premolars restored with composite resin using various prefabricated posts.

METHODS AND MATERIALS

Sixty sound maxillary premolars were divided into four equal sized groups. All but the control group received endodontic treatment followed by placement of mesiodistocclusal (MOD) composite restorations (Tetric Ceram) as follows: Group T = no post, Group DT = fiber reinforced composite (FRC) post (DT Light), Group FL = prefabricated metal post (Filpost). The control group (C) had no cavities prepared. After thermal and load cycling, static load was applied at a 30 degrees angle until fracture. Failure modes were categorized as restorable and non-restorable. Data were analyzed using the analysis of variance (ANOVA) and Duncan tests (a = 0.05).

RESULTS

The mean values of fracture loads (N) for all groups were: C (880+/-258); T (691+/-239); DT (865+/-269); and FL (388+/-167). Statistically significant differences (P<0.05) were observed for all groups except between groups C and DT. The Chi Square test showed failure modes in groups C and DT were mostly restorable. The most non-restorable fractures were observed in group FT.

CONCLUSION

Intact teeth and the teeth restored with composite and quartz fiber posts had a similar fracture resistance and the failure modes were mostly restorable. The lowest fracture resistance and the most non-restorable failures were observed in conjunction with metal posts.

CLINICAL SIGNIFICANCE

The results of this in vitro study suggest the use of a quartz fiber post used in conjunction with an MOD composite resin restoration improves fracture resistance in an endodontically treated premolar.

Effect of coronal macroretentions and diameter of a glass-FRC on fracture resistance of bovine teeth restored with fiber posts

AIM

The aim of this study was to evaluate fracture resistance of bovine teeth restored with glass fiber posts of different diameter and shape.

METHODS

Eighty single-rooted bovine teeth were prepared, embedded in a PVC cylinder using acrylic resin, and allocated into eight groups (N.=10) based on the post diameter (White Post DC) and shape: smooth double-tapered fiber post -- G1, G2, G3, and G4 with cervical diameters of 1.4 mm, 1.6 mm, 1.8 mm, and 2 mm, respectively; double-tapered fiber post with coronal macroretentions -- G5, G6, G7, and G8 with cervical diameters of 1.4 mm, 1.6 mm, 1.8 mm, and 2 mm, respectively. A three-step etch-and.rinse adhesive and resin cement system was used for postcementation. Afterwards, the core build-up was standardized with composite resin (Oppalis). The specimens were stored for seven days and later submitted to monotonic load at a crosshead speed of 0.05 cm/min (45 degrees ) until failure. The fracture loads were determined and the fracture mode was recorded.

RESULTS

The post diameter (P=0.0007) and post-surface characteristic (P=0.0149) factors affected the fracture resistance results significantly (2-way ANOVA). Low fracture strength values were noted in the group with narrower diameter and macroretentions (G5). The macroretentions damaged the fracture resistance results when post diameter was 1.4 mm (G1 and G5). On fiber posts having diameters of 1.6 mm, 1.8 mm, and 2 mm, macroretentions did not impair fracture strengths significantly.

CONCLUSIONS

A direct relation between the diameter of the fiber post and the fracture strength seems likely. Coronal macroretentions reduced fracture strength in thinner fiber posts.

Simulated fatigue resistance of composite resin versus porcelain CAD/CAM overlay restorations on endodontically treated molars

OBJECTIVE

To assess the influence of material selection (porcelain versus composite resin) for overlay-type restoration of endodontically treated molars and its effect on the in vitro fatigue resistance and failure mode.

METHOD AND MATERIALS

A standardized tooth preparation was applied to 30 extracted molars, including root canal treatment, 3-mm coverage of all cusps, a mesial box 1.5 mm below the cementoenamel junction (CEJ), a distal box in enamel, a glass-ionomer base, and immediately sealed dentin. Using the Cerec machine (Sirona), all teeth were restored with an overlay of standardized thickness and occlusal anatomy. Fifteen restorations were milled in the ceramic Vita MKII block (Vident) and the other 15 using the composite resin Paradigm MZ100 block (3M ESPE). The intaglio surfaces of the ceramic restorations were etched and silanated. The intaglio surfaces of the composite resin overlays were airborne-particle abraded and silanated. Preparations were airborne-particle abraded and etched before restoration insertion. All restorations were adhesively luted with an adhesive resin (Optibond FL, Kerr) and a light-curing composite resin (Filtek Z100, 3M ESPE). Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 200 N (5,000 cycles), followed by stages of 400, 600, 800, 1,000, 1,200, and 1,400 N at a maximum of 30,000 cycles each. Samples were loaded until fracture or to a maximum of 185,000 cycles.

RESULTS

MKII overlays fractured at a mean load of 1,147 N, and none of them withstood all 185,000 loading cycles (survival = 0%); with MZ100, the survival rate was 73%. With MKII, 40% of the fractures ended below the CEJ; with MZ100, only 25% did.

CONCLUSIONS

Composite resin MZ100 increased the fatigue resistance of overlay-type restorations in endodontically treated molars when compared to porcelain MKII. The efficiency of the bond strategy (immediate dentin sealing) was demonstrated by the absence of adhesive failures.

Fracture strength of endodontically treated molars transfixed horizontally by a fiber glass post

PURPOSE

To assess the effect of a horizontally transfixed fiber glass post placed between buccal and palatal surfaces, on the fracture strength of endodontically treated molar teeth with MOD cavities, either restored with resin-based composite, or not.

METHODS

75 sound maxillary human third molars were extracted, embedded in acrylic resin blocks and randomly assigned to five groups (n=15). Group A (sound teeth), (control) and Groups B, C, D and E, which were subjected to the following procedures after endodontic treatment: GB--(MOD+Endo), GC--(MOD+Endo+Post), GD--MOD and composite restoration (MOD+Endo+CR), GE--(MOD+Endo+Post+CR). The specimens were stored in distilled water at 37 degrees C for 24 hours. Later, a compressive force was applied by means of a universal testing machine at 1 mm/minute speed, parallel to the long axis of the teeth until fracture occurred.

RESULTS

The means of the results (N) followed by the same letter represent no statistical difference by ANOVA and Tukey (P<0.05): GA = 4289.8 (+/- 1128.9)a, GB = 549.6 (+/- 120.7)b, GC = 1474.8 (+/- 338.1)c, GD = 1224.7 (+/- 236.0)c, GE = 2645.4 (+/- 675.1)d. In the analysis of qualitative variables, there was a tendency to cusp fracture in all groups except for Group C. The fiber glass post transfixed horizontally in a MOD cavity significantly increased the fracture resistance of the teeth restored with resin composite.

[Strategies for posterior teeth reconstruction after endodontic treatment: a case report]

Reconstruction of hard dental tissue after endodontic treatment is a difficult and important duty of the dentist. According to the general opinion, endodontically treated teeth are inferior in quality, more brittle, predisposed to fractures and cracking. Logically, such teeth require reconstruction to prevent fractures, cracks, and bacterial microleakage leading to reinfection. The procedure of choice in the nineties of the 20th century was restoration with a metal post and prosthetic crown. Advances in materials resulting in improved adhesion to hard dental tissue have prompted a change in the reconstruction strategy for posterior teeth after endodontic treatment. In the case of molars, the crown can be restored with composite materials thanks to additional retention offered by the chamber of these teeth. The recommendation for premolars is to reinforce them with a glass fiber post. We now present a case which illustrates the actual trends in reconstruction of posterior teeth after endodontic treatment.

Effect of ferrule and bonding on the compressive fracture resistance of post and core restorations

AIM

The purpose of this study was to compare the fracture resistance of endodontically treated teeth restored with different post and core systems in combination with complete metal crowns in teeth with no coronal structure.

METHOD AND MATERIALS

Fifty extracted mandibular premolars were divided into five groups. The coronal portion of each tooth was removed at the cementoenamel junction (CEJ) in all groups except Group 1. In this group the teeth were sectioned 1 mm above the CEJ to create a ferrule. After root canal preparations, cast posts were placed in the first four groups. Prefabricated glass fiber posts and composite cores were placed in the fifth group. An opaque porcelain layer was applied to the metal post surfaces in the third group and an alloy primer was applied to the posts in the fourth group before using Panavia F2 resin cement. No bonding agent or surface treatments were used for the first and second groups. A Ni-Cr full cast crown for each sample was prepared and cemented. A compressive load was applied at an angle of 45 degrees to the crown with a universal testing machine. After 500,000 mechanical cycles at 1.5Hz, the maximum load at fracture (N) was recorded.

RESULTS

Significantly higher fracture resistance values (216.87 N) and survival rates (75%) were demonstrated for non-ferrule teeth restored with opaque layered posts than for other non-ferrule groups. The prefabricated post group showed the most favorable fracture pattern in all test groups (P=0.04).

CONCLUSION

Either a ferrule preparation or bonding with the use of an opaque porcelain layer can increase the fracture resistance of teeth with little remaining tooth structure that are restored with cast crowns following endodontic therapy.

CLINICAL SIGNIFICANCE

Bonding cast posts to the tooth structure has a significant effect on compensating for the lack of a ferrule on endodontically treated teeth.

Reconstruction of endodontically treated posterior teeth--with or without post? Guidelines for the dental practitioner

The clinical concepts regarding the restoration of root canal treated teeth are not clear today and often based on conjecture due to a lack of sound empirical data. The diversity of published opinions is confusing and may lead to less-than-optimal treatment selections. There is also emerging debate whether or not a post is necessary. The purpose of the present article is to organize this topic in evidence-based principles and provide dental practitioners with clear guidelines about restorative therapy for premolar and molar teeth. Two clinical reports are presented, to exemplify the different clinical situations. The first case highlights a conservative restoration of an endodontically treated molar, maintaining an adequate quantity of healthy residual tissue and only covering the cusp with restoration material, which was not sustained by healthy dentin. In the second case, the fact that the premolar was so badly damaged by carious pathology meant that it was necessary to use a pin to anchor the composite material, and the cusp was covered completely. Based on the two presented clinical reports and a literature review, the concept of fiber post application is explained. Searches by hand and MEDLINE were employed to identify peer-reviewed articles on reconstruction of endodontically treated posterior teeth. A total of 70 articles published between 1967 and 2008 were reviewed.

Fracture resistance of teeth restored with different post systems using new-generation adhesives

AIM

The aim of this study was to investigate the fracture strength of three post systems cemented with a dual cure composite resin luting cement by using different adhesive systems.

METHODS AND MATERIALS

In this study 63 extracted anterior teeth with single roots were endodontically prepared and filled. Teeth were randomly assigned to one of three post systems placed into the prepared canals: Group I - titanium posts (n=21) (Filpost); Group II - glass fiber posts (n=21) (Mirafit White); and Group III zirconia posts (n=21) (CosmoPost). Each group was again randomly divided into three subgroups according to the bonding materials used [Single Bond (n=7), Clearfil SE Bond (n=7), and Prompt L Pop (n=7)]. A dual cured resin cement (Rely X ARC) was used for bonding the posts into the root canals. Standard cores were made by a composite resin (Clearfil Photocore) using core build-ups. The samples were tested in the compression test machine for 1 mm/min and fracture resistance of the teeth were recorded. The data was analyzed by using two-way analysis of variance (ANOVA) and Duncan's New Multiple Range Tests. A significance level of p<.05 was used for all comparisons.

RESULTS

There was a significant difference in fracture resistance between the post systems (p<0.05) and the interaction of adhesive resins and post systems (p<0.05). Mirafit White was more resistant to fracture than other groups; Filpost showed the least resistance to fracture. CosmoPost post system bonded with Single Bond recorded the lowest fracture resistance (p<0.05).

CONCLUSION

Endodontically treated anterior teeth restored with glass fiber posts exhibited higher failure loads than teeth restored with zirconia and titanium posts. Self-etching adhesives are better alternatives to etch-and-rinse adhesive systems for luting post systems.

CLINICAL SIGNIFICANCE

Under the condition of this study, glass fiber posts are preferable to restore endodontically treated anterior teeth.

Effect of reduced post length on the resistance to fracture of crowned, endodontically treated teeth

OBJECTIVE

To examine the influence of a reduced post length sealed with a titanium-reinforced composite luting agent on the fracture resistance of crowned endodontically treated teeth with a 2-mm ferrule on healthy tooth structure.

METHOD AND MATERIALS

The study consisted of 60 intact single-rooted premolars with similar root diameters and lengths. Teeth were endodontically treated and randomly divided into 6 experimental groups (n = 10) with various post lengths (5, 8, and 10 mm) and types (ParaPost and Dentatus) of equal diameter. Posts were luted with a titanium-reinforced composite resin luting agent. Titanium-reinforced composite resin cores were constructed, and cast crowns with a 2-mm ferrule on healthy tooth structure were cemented. Specimens were mounted in a jig that allowed loading of the buccal cusp in the axio-occlusal line at a 30-degree angle to the long tooth axis. A continuous compressive force at a crosshead speed of 2 mm/min was applied by an Instron testing machine. Forces at fracture (in newtons) and mode of failure were recorded. One-way analysis of variance (ANOVA) and the Scheffe test were used to statistically compare the differences among groups at a significance of 5%.

RESULTS

ANOVA showed no statistically significant differences among the mean failure forces for the tested groups in their resistance to fracture under load. The Scheffé contrast test showed no statistically significant differences among all combinations of the 6 tested groups (F [5.59] = 0.032; P > .05).

CONCLUSION

Within the limitations of this study, post length did not influence the fracture resistance of crowned endodontically treated teeth with a 2-mm ferrule on healthy tooth structure. For tooth resistance, prosthesis design is more important than post characteristics.

Fracture resistance of anterior teeth restored with a novel nonmetallic post

OBJECTIVE

To determine the fracture resistance of endodontically treated anterior teeth restored with a novel nonmetallic post in combination with self-etching adhesives.

MATERIALS AND METHODS

Extracted maxillary anterior teeth were sterilized with gamma irradiation, and each crown was severed 2 mm above the cementoenamel junction. Endodontic treatment was performed, and the teeth were divided into 7 test groups according to the post-adhesive combination used (n = 8 in each group). The following combinations of posts and adhesives were used: group 1, ParaPost stainless steel post with glass ionomer cement (control group); group 2, Light Post post with Clearfil SE Bond bonding agent and Panavia-F adhesive; group 3, Light Post post with Xeno-III bonding agent and Panavia-F adhesive; group 4, ParaPost Fiber White post with Clearfil SE Bond bonding agent and Panavia-F adhesive; group 5, ParaPost Fiber White post with Xeno-III bonding agent and Panavia-F adhesive; group 6, everStick post with Clearfil SE Bond bonding agent and Panavia-F adhesive; and group 7, everStick post with Xeno-III bonding agent and Panavia-F adhesive. Core build-ups to restore anatomic form were made from light-cured composite (TPH3). Specimens were stored in water at 37 degrees C. The roots of each tooth were embedded in an acrylic base, and the teeth were mounted at 135 degrees to the horizontal. The teeth were loaded in an Instron machine, and loading was applied to the point of fracture. Fracture loads were recorded, means and standard deviations (SDs) were calculated, and the data were analyzed with analysis of variance (ANOVA) and Tukey"s tests.

RESULTS

The mean fracture load (and SD) for each group was as follows: for group 1, 536.8 (75.1) N; for group 2, 1,000.1 (190.9) N; for group 3, 1,049.9 (231.5) N; for group 4, 1,548.5 (290.0) N; for group 5, 1,171.3 (296.9) N; for group 6, 1,711.7 (516.7) N; and for group 7, 1,825.7 (527.3) N. ANOVA revealed significant differences among the groups (p < 0.001). In addition, the mean fracture value for group 7 was significantly higher than those of the other groups p < 0.05) except for groups 4 and 6.

CONCLUSIONS

Use of a novel glass fibre post (the everStick post) was associated with the highest mean fracture force for maxillary anterior teeth, regardless of the bonding agent used, whereas the stainless steel post was associated with the lowest mean fracture force.