Fracture resistance of thermal cycled and endodontically treated premolars with adhesive restorations

Influence of Direct Coronal Restoration Materials on the Fracture Resistance of Endodontically Treated Premolars: An In Vitro Study

(1) Background: The long-term survival of an endodontically treated tooth depends on a successful root canal treatment as well as an adequate definitive coronal restoration. This study aimed to evaluate the strength of endodontically treated premolars with mesial-occlusal-distal (MOD) cavity preparation restored with different direct coronal restoration materials but from the same manufacturer against fracture. (2) Methods: sixty intact premolars were selected and placed into five groups (n = 12): G1-intact teeth, G2-endodontic treatment and unrestored MOD cavities, G3-endodontic treatment and MOD cavities restored with Tetric PowerFlow and Tetric EvoCeram, G4-endodontic treatment and MOD cavities restored with Multicore Flow and Tetric EvoCeram, and G5-endodontic treatment and MOD cavities restored with Multicore Flow. The specimens were subjected to an axial compression load at a speed of 1.6 mm/min and optically inspected before and after with a stereomicroscope. For each premolars group, the following data were recorded: the compression resistance, the compressive strength, and the maximum force supported. The microstructure of the samples after the compression test was analyzed using scanning electron microscopy (SEM). (3) Results: statistical analysis (ANOVA and Tukey test) showed that there was a statistically significant difference between G1 and the other groups. Even though there was no statistically significant difference between the restored groups, a better mechanical behavior was registered within the G3. (4) Conclusions: this in vitro study indicated that none of the materials used can lead to a higher or at least similar fracture resistance as the intact teeth. The coronal restoration only with nano-hybrid composites may lead to a higher therapeutic benefit for the fracture-susceptible premolars.

Fatigue performance of endodontically treated molars reinforced with different fiber systems

OBJECTIVE

The aim was to investigate the fatigue performance of root canal-treated (RCT) molars restored with different direct restorations utilizing discontinuous and continuous fiber-reinforced composite (FRC) systems. The impact of direct cuspal coverage was also evaluated.

MATERIALS AND METHODS

One hundred and twenty intact third molars extracted for periodontal or orthodontic reasons were randomly divided into six groups (n=20). Standardized MOD, regular cavities for direct restorations were prepared in all specimens, and subsequently, root canal treatment and root canal obturation was carried out. After the endodontic treatment, the cavities were restored with different fiber-reinforced direct restorations as follows: SFC group (control), discontinuous short fiber-reinforced composite (SFC) without cuspal coverage (CC); SFC+CC group, SFC with cuspal coverage; PFRC group, transcoronal fixation with continuous polyethylene fibers without CC; PFRC+CC group, transcoronal fixation with continuous polyethylene fibers with CC; GFRC group, continuous glass FRC post without CC; and GFRC+CC, continuous glass FRC post with CC. All specimens underwent a fatigue survival test in a cyclic loading machine until fracture occurred or 40,000 cycles were completed. The Kaplan-Meier survival analysis was conducted, followed by pairwise log-rank post hoc comparisons between the individual groups (Mantel-Cox).

RESULTS

The PFRC+CC group was characterized by significantly higher survival compared to all the groups (p < 0.05), except for the control group (p = 0.317). In contrast, the GFRC group showed significantly lower survival compared to all the groups (p < 0.05), except for the SFC+CC group (p = 0.118). The control group (SFC) showed statistically higher survival than the SFRC+CC group (p < 0.05) and GFRC group (p < 0.05), but it did not differ significantly from the rest of the groups in terms of survival.

CONCLUSIONS

Direct restorations utilizing continuous FRC systems (in the form of polyethylene fibers or FRC post) to restore RCT molar MOD cavities performed better in terms of fatigue resistance when CC was performed compared to the same FRC restorations without CC. On the contrary, teeth restored with SFC restorations performed better without CC compared to the ones where SFC was covered.

CLINICAL RELEVANCE

In the case of fiber-reinforced direct restorations for MOD cavities in RCT molars, direct CC is recommended when utilizing long continuous fibers for reinforcement, however, should be avoided when only SFC is used for their reinforcement.

Influence of single post, oval, and multi-post restorative techniques and amount of residual tooth substance on fracture strength of endodontically treated maxillary premolars

PURPOSE

The aim of this study was to compare the influence of the number of coronal walls and post-endodontic restorations on the mechanical strength of 165 recently extracted endodontically treated maxillary premolars.

METHODS

The teeth were divided into 3 control (no post) and 3 test groups according to the number of residual walls. Each test group was divided into subgroups according to the type of post-endodontic restoration (single, oval, and multi-post techniques). Samples were prepared conforming to the assigned subgroup. A universal loading machine applied a load parallel to the longitudinal axis of the teeth, thus simulating physiological occlusion. ANOVA and the Kruskal Wallis test were used for comparisons (P ≤ 0.05), and Tukey's test for multiple comparisons.

RESULTS

For intact teeth, significant differences were found among all 3 subgroups, with single post showing the highest values. For 3 residual walls, oval post resulted in significantly lower values than single and multi-post systems. For 2 residual walls, the multi-post technique showed almost twice the resistance of oval post restorations.

CONCLUSION

In oval canals the use of a single or multi-post technique increased post-and-core resistance even in intact teeth, whereas oval fiber posts showed no improvements. Multi-post design improved fracture resistance mostly in maxillary premolars lacking both marginal ridges.

Fracture behaviour of MOD restorations reinforced by various fibre-reinforced techniques - An in vitro study

PURPOSE

The aim was to evaluate the fracture resistance of various direct restorative techniques utilizing different fibre-reinforced materials for restoring deep class II. MOD cavities in molar teeth.

MATERIAL AND METHODS

Two hundred forty intact mandibular third molars were randomly divided into twelve groups (n = 20). Except for the control group (G12), deep mesio-occluso-distal (MOD) cavities were prepared all other groups. After adhesive treatment and rebuilding the missing interproximal walls with composite, the specimen were restored with different fibres and a final occlusal layer of composite as follows: composite only (G1), short fibre-reinforced composite (SFRC) (G2), glass fibre net (GFN) on the base of the cavity bucco-lingually (BL) and SFRC (G3), SFRC and GFN on top of it BL (G4), SFRC and occlusal splinting with GFN (G5), GFN circumferentially and SFRC (G6), polyethylene fibres (PF) on the base of the cavity BL and composite (G7), composite and PF on top of it BL (G8), composite and occlusal splinting with PF (G9), PF circumferentially and composite (G10), transcoronal splinting with PF (G11). Fracture-resistance for the restored teeth were tested using universal-testing machine. Fracture thresholds and fracture patterns were measured and evaluated.

RESULTS

The transcoronal splinting (G11) yielded the highest fracture resistance among the restored groups. Groups 1, 3 and 4 showed significantly lower fracture resistance values compared to intact teeth.

CONCLUSION

Incorporating polyethylene or a combination of short and bidirectional glass fibres in certain positions in direct restorations seems to be able to restore the fracture resistance of sound molar teeth.

Fracture Resistance of Endodontically Treated Maxillary Premolars Restored With Different Methods

Purpose:

The purpose of this in vitro study was to evaluate the resistance and patterns of fracture of endodontically treated maxillary premolars (ETPs) restored with different methods.

Methods and Materials:

Mesio-occluso-distal cavities were prepared in 50 extracted caries-free human maxillary premolars after endodontic treatment. The teeth were divided into five groups (n=10), according to the restorative method. G1: intact teeth (control group); G2: conventional composite resin; G3: conventional composite resin with a horizontal glass fiber post inserted between buccal and palatal walls; G4: bulk-fill flowable and bulk-fill restorative composites; and G5: ceramic inlay. For direct restorations, Filtek Z350 XT, Filtek Bulk Fill Flowable Restorative, and Filtek Bulk Fill Posterior Restorative were used. Indirect restorations were fabricated from a pressable lithium disilicate glass-ceramic (IPS e-max Press) and adhesively cemented (RelyX Ultimate). All specimens were subjected to thermocycling (5°C to 55°C/5000 cycles) and additionally submitted to cyclic loading 50,000 times in an Electro-Mechanical Fatigue Machine. Next, the specimens were subjected to a compressive load at a crosshead speed of 1 mm/min until fracture. The fractured specimens were analyzed to determine the fracture pattern using a stereomicroscope, and then representative specimens were carbon coated to allow for the studying of the fracture surface under scanning electron microscopy. One-way analysis of variance (ANOVA) was used to compare fracture resistance of the groups. The results of fracture patterns were submitted to the Fisher exact test (α=0.05).

Results:

All specimens survived fatigue. Mean (standard deviation) failure loads (N) for groups were as follows: G1: 949.6 (331.5); G2: 999.6 (352.5); G3: 934.5 (233.6); G4: 771.0 (147.4); and G5: 856.7 (237.5). The lowest fracture resistance was recorded for G4, and the highest ones were recorded for G2, followed by that of G1 and G3. One-way ANOVA did not reveal significant differences between groups (p&gt;0.05). The highest repairable fracture rates were observed in G1 (100%) and G3 (80%).

Conclusions:

ETPs restored with conventional composite resin with or without horizontal fiber post, bulk-fill composite, and ceramic inlay showed fracture resistance similar to that of sound teeth. Conventional composite resin restorations exhibited the highest prevalence of unrepairable fractures, and the insertion of a horizontal fiber post decreased this prevalence. Intact teeth showed 100% of repairable fractures. It is difficult to extrapolate the results directly to a clinical situation due to the limitations of this study.

Performance of resin composite restorations in the primary dentition: a retrospective university-based study

BACKGROUND

Limited data is available on variables influencing the survival of composite restorations in primary teeth.

AIM

This retrospective university-based study assessed the survival and risk factors associated with failures of resin composite restorations performed in primary teeth.

DESIGN

The sample was composed of 961 restorations from records of 337 patients (178 girls and 159 boys) attended in a university dental clinic. The restorations' longevity up to 48 months of follow-up was assessed using the Kaplan-Meier survival test. Multivariate Cox regression analysis with shared frailty was used to evaluate the factors associated with failures (P < 0.05).

RESULTS

Mean survival time was 41.5 months (95% CI: 39.7-43.3), with 70.6% of the restorations surviving after 48 months of evaluation. The overall annual failure rate up to 48 months follow-up was 8.3%. Restorations placed in lower arch had lower survival rate than those in upper arch (HR: 1.82, 95% CI: 1.02-3.28). Restorations involving two or more surfaces had more risk of failure than restorations placed in cavities involving only one surface (HR: 2.55 95% CI: 1.34- 4.83). Girls had less risk of failure in their restorations (HR: 0.43, 95% CI: 0.19-0.96).

CONCLUSION

Individual and dental variables such as gender, arch type and number of restored surfaces were associated with failure of composite restorations performed in children under daily life clinical environment.

Fracture resistance and stress distribution of repairing endodontically treated maxillary first premolars with severe non-carious cervical lesions

This study was to compare the influence of glass fiber post placement and crown restoration on endodontically treated maxillary first premolars with severe NCCLs using three-dimensional finite element analysis and fracture resistance testing. G1, intact teeth. G2, teeth with artificial defect. G3, composite resin (CR). G4, CR and fiber post in buccal canal (FPB). G5, CR and fiber post in palatal canal (FPP). G6, CR and fiber posts in buccal and palatal canals (FPBP). G7, CR and crown (C). G8, CR, FPB, C. G9, CR, FPP, C. G10, CR, FPBP, C. Teeth in G2, G3, and G5 showed a similar stress concentration at the tip of the defect. The fracture resistance of G2 did not differ significantly from G3 and G5 (p>0.05) but differed significantly from that in other groups (p<0.05). The fractures in G4 were more favorable, and the difference of those in G1 from those in G7, G8, G9, and G10 was statistically significant (p<0.05). Restoration of root-filled maxillary premolars with severe NCCLs using fiber post in the buccal canal may be more efficacious than other restoration methods.

In vitro fracture strength and patterns in root-filled teeth restored with different base materials

BACKGROUND

There is little research on the effects of an intermediate base on the fracture strength of root-filled teeth. This study compared the fracture strengths and patterns of root-filled teeth restored with intermediate bases of glass-ionomer cement (GIC), zinc polycarboxylate cement (ZPC), dual-cured resin composite (DCRC) and Biodentine^® under resin composite.

METHODS

Standardized cavities were prepared in 100 extracted human maxillary and mandibular premolars, and root canal treatment was performed. The teeth were stratified and randomly allocated to five groups (n = 20): (i) GIC; (ii) ZPC; (iii) DCRC; (iv) Biodentine; and (v) prepared but unrestored (control). The teeth were subjected to an oblique, ramped load until fracture. The fracture loads, level, mode and location were recorded.

RESULTS

Mean fracture strengths of all restored groups were not significantly different amongst the groups. There were significant overall effects on mean fracture strength for tooth type (P = 0.002) and buccolingual width of the crown (P = 0.001).

CONCLUSIONS

The four materials were appropriate intermediate bases. The laminate restorative technique promoted fracture strengths that are likely to withstand normal and maximum masticatory function. The base material can influence failure mode, which may have implications for the clinical presentation of fractures of root-filled teeth.

Evaluation of fracture resistance and mode of failure of premolars restored with nanohybrid composite, ORMOCER and ceramic inlays

Objectives

To evaluate the fracture resistance and mode of failure of maxillary premolars restorations restored with nanohybrid Composite, ORMOCER and Ceramic Inlays.

Materials and method

100 extracted first maxillary premolar were collected. Samples were divided into five groups. Group I - Intact premolars, Group II -MOD cavities without restorations, Group III - MOD cavities restored with composite restoration, GROUP IV - MOD cavities restored with ORMOCER restoration and GROUP V - MOD cavities restored with ceramic inlays. All the samples were sent for the axial compression test under the universal testing machine. Fracture resistance and fracture modes were recorded.

Result

Highest fracture resistance was achieved in Group V (1324.74 ± 336.78) almost comparable to that of natural tooth (1381.07 ± 259.36) (p < 0.05), followed by Group IV (MOD cavities with ORMOCER restorations) (1082.27 ± 351.27) (p < 0.01) and least fracture resistance in Group III (MOD cavities with composite restorations) (778.35 ± 100.25) (p < 0.0001). Mode of fracture in Group IV and Group V are almost similar and In Group III 65% of the cases showed non-restorable fractures.

Conclusion

ORMOCER fracture resistance along with other groups of clinically restorable fracture stand better than Nanohybrid composite.

Clinical Relevance

Based on the present study, the dentist can utilize the ORMOCER material as a restoration material for the cavities of posterior teeth which is better in terms of fracture resistance and durability of the restoration when compare to nanohybrid composite.

Effect of cleaning methods on bond strength of self-etching adhesive to dentin

Aim:

The aim of this study was to investigate the influence of cleaning methods to remove zinc oxide-eugenol-based root canal sealer (Endomethasone) on the bond strength of the self-etching adhesive to dentin.

Materials and Methods:

Twenty crowns of bovine incisors were cut to expose the pulp chamber. A zinc oxide- and eugenol-based sealer was placed for 10 min in contact with the pulp chamber dentin. Specimens were divided into four groups according to the cleaning method of dentin used: G1, no root canal sealer (control); G2, 0.9% sodium chlorite (NaCl); G3, ethanol; and G4, followed by diamond drill. After cleaning, the teeth were restored with composite resin and Clearfil SE Bond. All specimens were sectioned to produce rectangular sticks and dentin/resin interface was submitted to microtensile bond testing. The mean bond strengths were analyzed using ANOVA/Tukey (α = 0.05).

Results:

G3 and G4 showed bond strengths similar to the G1 (P > 0.05). A significant decrease in the bond strength in the G2 was observed (P < 0.05). G1, G3, and G4, the predominant failure mode was the mixed type. The prevalence of adhesive failure mode was verified in the G2.

Conclusion:

The cleaning methods affected the bond strength of the self-etching adhesive to dentin differently.

Fracture resistance of endodontically treated teeth restored with indirect composite inlay and onlay restorations - An in vitro study

Objective

The purpose of this in vitro study was to evaluate and compare the fracture resistance and fracture mode of extensive indirect inlay and onlay composite resin restorations performed for endodontically treated premolars.

Materials and methods

A total of 55 extracted maxillary premolars were randomly divided into four groups. The first group (n = 15) remained untreated to serve as a positive control; the second group (n = 15) was endodontically treated with inlay cavities prepared and restored with indirect composite inlay restorations; the third group (n = 15) was also endodontically treated with onlay cavities prepared and restored with indirect composite onlay restorations; and the fourth group (n = 10) was endodontically treated with mesio-occlusodistal (MOD) cavities prepared and left unrestored to serve as negative controls. Dual cure indirect composite resin was used to fabricate the inlay and onlay restorations performed for the second and third groups, respectively. All teeth were subjected to compressive axial loading test using a metal ball (6 mm in diameter) in a universal testing machine (Instron 1195) with a cross-head speed of 0.5 mm/min until a fracture occurred. Statistical analysis of fracture resistance and fracture mode were performed with analysis of variance (ANOVA) (α = 0.05) and Kruskal–Wallis (α = 0.05) tests, respectively.

Results

For the four treatment groups, the mean fracture resistance values were 1326.9 N, 1500.1 N, 1006.1 N, and 702.7 N, respectively. Statistical analyses showed no significant differences between the mean fracture resistance of the intact tooth group and the inlay restoration group (p > 0.05), while significant differences were observed between the mean fracture resistance of all the other groups (p < 0.05). The Kruskal–Wallis test showed statistically significant differences between the fracture modes of the four groups.

Conclusion

Within the limitations of this study, endodontically treated teeth were successfully restored with indirect composite inlay and onlay restorations. However, the fractures that accompanied the inlay restorations were more severe and were unable to be restored.

Patient Risk Factors’ Influence on Survival of Posterior Composites

This practice-based retrospective study evaluated the survival of resin composite restorations in posterior teeth, focusing on the influence of potential patient risk factors. In total, 306 posterior composite restorations placed in 44 adult patients were investigated after 10 to 18 yrs. The history of each restoration was extracted from the dental records, and a clinical evaluation was performed with those still in situ. The patient risk status was assessed for caries and “occlusal-stress” (bruxism-related). Statistical analysis was performed by the Kaplan–Meier method and Cox-regression multivariate analysis. In total, 30% of the restorations failed, of which 82% were found in patients with 1 or 2 risk factors. Secondary caries was the main reason of failure within caries-risk patients, whereas fracture was the main reason in “occlusal-stress-risk” patients. The patient variables gender and age did not significantly affect survival, but risk did ( p < .001). Tooth type ( p < .001), arch ( p = .013), and pulpal vitality ( p = .003) significantly affected restoration survival. Within the limits of this retrospective evaluation, the survival of restorations is affected by patient risk factors, which should be included in survival analyses of restorations.

Fracture resistance and pattern of the upper premolars with obturated canals and restored endodontic occlusal access cavities

We studied whether obturing canals and restoring endodontic occlusal access cavities on upper premolars could provide acceptable resistance and pattern to fracture. Eighteen upper premolars were divided equally into 3 groups. Group 1 consisted of intact controls; group 2 had access cavities and root canal preparations; group 3 as in group 2 but obturated with gutta-percha and AH26, and the access cavity restored with glass ionomer and composite. Specimens were submitted to compressive strength testing using the Hounsfield Universal H50KM testing machine with a load cell of 2000 Newtons and a crosshead speed set at 1.0 mm/min until fracture. The results from the compressive strength tests showed that intact controls (1105.83±90.93 MPa) and restored premolars (936.67±44.67 MPa) were significantly different from premolars with unrestored access cavities 568.33±105.49 MPa. There was no significant difference between intact controls and restored premolars. The predominant fracture pattern for intact teeth was an oblique fracture. For premolars that had endodontic access cavities, restored or unrestored, the most common fracture pattern was a vertical fracture. The restoration of occlusal access cavities with glass ionomer and composite provided fracture resistance close to that of intact controls, but when restored teeth fractured, they were predominantly non-restorable.

Fracture resistance of endodontically treated premolars with direct composite restorations

Purpose:

To determine the fatigue resistance and failure mode of endodontically treated premolars using direct composite resin restorations.

Materials and Methods:

Eighty-four human premolars were divided into seven groups of 12, prepared as follows: Intact teeth used in Group 1 as control, the second group covers the endodontically treated teeth, restored with direct onlays using Z250 composite resin, the next two groups (i.e. 3,4) were similar to the second group, but subjected to 1 and 2 million fatigue load cycles, respectively. Groups 5, 6, 7 were similar to groups 2, 3, 4, however, in these groups Tetric Ceram was used as the restorative material. All specimens were loaded using a Universal Testing Machine until fracture occurred. One-way Anova andTukey's HSD tests were used to analyze the data of onlay groups.

Results:

All specimens withstood the masticating simulation. The mean fracture strength for Goups 1 to 7 was: 1276.92, 1373.47, 1269/70, 486/35, 484/12, 1130/49, 1113/79 Newton, respectively. No statistically significant differences were found between the groups in fracture strength and failure mode.

Conclusions:

No statistically significant differences in fracture strength were found between sound teeth and composite onlays that were subjected to 1 and 2 million fatigue load cycles.

Influence of adhesive system and bevel preparation on fracture strength of teeth restored with composite resin

The aim of this study was to evaluate the fracture strength of teeth with different cavosurface margin cavity preparations and restored with composite resin and different adhesive systems. Eighty premolars were randomly divided in 8 groups, as follow: G1- sound teeth; G2- MOD preparation (no restoration); G3- Adper Single Bond without bevel preparation (butt joint); G4- Adper Single Bond with bevel preparation; G5- Adper Single Bond with chamfer preparation; G6- Clearfil SE Bond without bevel (butt joint); G7- Clearfil SE Bond with bevel preparation; G8- Clearfil SE Bond with chamfer preparation. The adhesive systems were applied according to manufacturers' instructions. Composite resin (Filtek Z250) was incrementally placed in all cavities. After 24 h, the specimens were tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey's test (fracture strength) and Fisher's exact test (fracture pattern). The confidence level was set at 95% for all tests. Prepared and non-restored teeth showed the worst performance and G4 exhibited the highest fracture strength among all groups (p<0.05). In conclusion, all restorative treatments were able to recover the fracture strength of non-restored teeth to levels similar to those of sound teeth. Using a total-etch adhesive system with bevel preparation significantly improved the resistance to fracture.