Effect of two different types of fibers on the fracture resistance of endodontically treated molars restored with composite resin

PURPOSE

To compare the in vitro fracture resistance of endodontically treated molars with mesio-occluso-distal (MOD) cavities restored with two different types of fibers.

MATERIALS AND METHODS

Sixty extracted human mandibular first molars were selected for the study and randomly assigned to six groups (n = 10). Group 1 served as the control. In groups 2 through 6, endodontic access and standard MOD cavities were prepared. Following root canal treatment, group 2 was left unrestored. In group 3, the teeth were restored with composite resin (Venus, Heraeus Kulzer). In group 4, flowable composite resin (Venus, Heraeus Kulzer) was used before restoring the teeth with composite resin. In group 5, leno-woven ultrahigh molecular weight polyethylene ribbon fiber (Ribbond) was inserted in the flowable resin in a buccal to lingual direction, and the teeth were then restored with composite resin. In group 6, translucent glass fiber (Vectris, Ivoclar) was adapted over the flowable resin in the bucco-lingual direction and restored with composite resin. The specimens were stored in 100% humidity at 37°C for 1 day. Compressive loading of the teeth was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. The mean load necessary to fracture the samples was recorded in Newtons (N). Data were subjected to analysis of variance (ANOVA) and Duncan's post-hoc test, where significance was set at p < 0.001.

RESULTS

The highest and the lowest mean fracture strengths were found in sound teeth (1598.8 N) and unrestored teeth (393.7 N), respectively. The mean load necessary to fracture the samples was 958.6 N in the polyethylene ribbon group (group 5), 913.2 N in the glass-fiber group (group 6), 699.7 N in teeth restored with flowable resin and composite (group 4), and 729.3 N in group 3 with composite resin alone. Statistical analysis showed significantly higher fracture resistance of both the fiber groups compared to composite resin alone (p < 0.001).

CONCLUSION

Both polyethylene ribbon and glass fiber under MOD composite restorations significantly increased fracture strength with no statistical difference between the two groups. Therefore, both polyethylene- and glassfiber- reinforced composites can be used for access cavity restorations in teeth with weakened cusps.

Posts--when it all goes wrong! Part 1: case assessment and management options

Posts have been used for many years to retain restorations or cores for extra-coronal restorations in endodontically treated teeth.This article discusses the variety of post systems that are available and the incidence and reasons for failure of teeth that have been restored with posts. The treatment options available for the management of such failures are considered, in addition to the indications for both non-surgical and surgical management of endodontic failures. The attitudes of dentists and the perceived complications of attempting post removal are reviewed, along with the evidence to support the prevalence of complications.

CLINICAL RELEVANCE

Failure of post-retained restorations is a relatively frequent finding due to failure of the restoration itself or the endodontic treatment. It is therefore important to understand and be aware of the various treatment options available, their indications and associated risks.

Root fortification

An incompletely formed tooth is left with thin dentin walls and experiences a higher incidence of cervical root fracture that reduces the long-term overall prognosis of the tooth. Faced with these situations, clinicians have attempted to use various restorative methods to reinforce the remaining root. Various techniques have been reported, and the scientific evidence for each has been reviewed. The biomechanical considerations of reinforcing a weakened root are also reviewed, and the most current information about failure analysis, fracture characteristics of natural dentin, and in vitro test configurations used have been considered. In light of these additional considerations, some recommendations for future understanding of this complex problem have been proposed.

[Fatigue and fracture resistance of the flared roots restored with computer aided design and computer aided manufacturing glass fiber posts]

OBJECTIVE

To evaluate the fatigue and fracture resistance of the flared roots restored with computer aided design (CAD) and computer aided manufacturing (CAM) glass fiber posts.

METHODS

In the study, 32 maxillary central incisors with roots longer than 13 mm were selected and their canals were flared, and the roots were allocated into 4 groups (n=8) by a random number chart: CAD/CAM glass fiber posts, prefabricated quartz fiber posts, cast gold alloy posts, and CAD/CAM zirconia posts. The posts were luted to the roots by resin cement and fabricate zirconia crown for every specimen. An addition-type silicone impression material was used to simulate the periodontal ligament. All the specimens were submitted to 1.2×10(6) cycles loaded with a 49 N force, at 45 degree to the long axis of the teeth simultaneously with 3 000 thermal cycles (5 °C-50 °C-5 °C). After that, the specimens were subjected to a load at a crosshead speed of 1 mm/min in a servo-hydraulic testing machine applied at 45 degree to the long axis of the tooth until fracture. The data were subjected to ANOVA test and the patterns of the failure were examined.

RESULTS

After the cycling loading, 4 crowns from prefabricated quartz fiber posts groups were deboned, and no other failure was found after the cycling loading; the fracture strengths of CAD/CAM glass fiber posts group [(441.5± 103.2) N] and cast gold alloy posts group [(462.9±170.0) N] were higher (F=4.613, P<0.05) than those of CAD/CAM zirconia posts group [(284.1±99.0) N] and prefabricated quartz fiber posts group [(315.4±112.3) N]; the entire specimens presented unfavorable failures.

CONCLUSION

Although further in vitro and in vivo studies are necessary, the results of this study show that the use of CAD/CAM glass fiber posts and cast gold alloy posts may achieve better outcomes in flared roots than that of CAD/CAM zirconia posts and prefabricated quartz fiber posts.

Fracture resistance of teeth restored with all-ceramic inlays and onlays: an in vitro study

Fracture resistance of inlays and onlays may be influenced by the quantity of the dental structure removed and the restorative materials used. The purpose of this in vitro study was to evaluate the effects of two different cavity preparation designs and all-ceramic restorative materials on the fracture resistance of the tooth-restoration complex. Fifty mandibular third molar teeth were randomly divided into the following five groups: group 1: intact teeth (control); group 2: inlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press, Ivoclar Vivadent AG, Schaan, Liechtenstein); group 3: inlay preparations, zirconia ceramic (ICE Zirkon, Zirkonzahn SRL, Gais, Italy); group 4: onlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press); and group 5: onlay preparations, zirconia ceramic (ICE Zirkon). The inlay and onlay restorations were adhesively cemented with dual polymerizing resin cement (Variolink II, Ivoclar Vivadent AG). After thermal cycling (5° to 55°C × 5000 cycles), specimens were subjected to a compressive load until fracture at a crosshead speed of 0.5 mm/min. Statistical analyses were performed using one-way analysis of variance and Tukey HSD tests. The fracture strength values were significantly higher in the inlay group (2646.7 ± 360.4) restored with lithium-disilicate glass-ceramic than those of the onlay group (1673.6 ± 677) restored with lithium-disilicate glass-ceramic. The fracture strength values of teeth restored with inlays using zirconia ceramic (2849 ± 328) and onlays with zirconia ceramic (2796.3 ± 337.3) were similar to those of the intact teeth (2905.3 ± 398.8). In the IPS e.max Press groups, as the preparation amount was increased (from inlay to onlay preparation), the fracture resistance was decreased. In the ICE Zirkon ceramic groups, the preparation type did not affect the fracture resistance results.

Influence of remaining coronal structure and of the marginal design on the fracture strength of roots restored with cast post and core

OBJECTIVE

The purpose of this study was to evaluate the fracture strength of roots that were prosthetically restored with cast post and core with or without any remaining coronal structure and with different finish lines.

MATERIALS AND METHODS

Sixty bovine incisors were sectioned below the cementoenamel junction, endodontically treated and randomly divided into six experimental groups (n = 10) containing teeth with or without any remaining coronal structure and with a beveled shoulder, a chanfered or a shoulder finish line design. The cast post and core were luted with dual-cured resin cement. The metal crowns were cemented with zinc phosphate cement. The specimens were subjected to a tangential compressive load (135° angle) at a crosshead speed of 0.5 mm/min until failure, using a universal testing machine. The fracture strength data were analyzed using the ANOVA and LSMeans (least square means) tests (α = 0.05).

RESULTS

The data indicated that the teeth with 2 mm of remaining coronal structure showed the highest fracture strength values when compared with the teeth without any remaining structure (p < 0.05). As to the different finish line designs, the highest fracture strength values were obtained for the beveled shoulder, followed by the chanfered and then by the shoulder designs (p < 0.05).

CONCLUSIONS

It may be concluded that, to increase fracture strength, a beveled shoulder and 2 mm of remaining coronal structure are the ideal conditions.

Hidden contributions of the enamel rods on the fracture resistance of human teeth

The enamel of human teeth is generally regarded as a brittle material with low fracture toughness. Consequently, the contributions of this tissue in resisting tooth fracture and the importance of its complex microstructure have been largely overlooked. In this study an experimental evaluation of the crack growth resistance of human enamel was conducted to characterize the role of rod (i.e. prism) orientation and degree of decussation on the fracture behavior of this tissue. Incremental crack growth was achieved in-plane, with the rods in directions longitudinal or transverse to their axes. Results showed that the fracture resistance of enamel is both inhomogeneous and spatially anisotropic. Cracks extending transverse to the rods in the outer enamel undergo a lower rise in toughness with extension, and achieve significantly lower fracture resistance than in the longitudinal direction. Though cracks initiating at the surface of teeth may begin extension towards the dentin-enamel junction, they are deflected by the decussated rods and continue growth about the tooth's periphery, transverse to the rods in the outer enamel. This process facilitates dissipation of fracture energy and averts cracks from extending towards the dentin and vital pulp.

Assessment of awareness amongst school teachers regarding prevention and emergency management of dentoalveolar traumatic injuries in school children in Pune City, before and 3 months after dental educational program

Children have boundless energy, so, they are continuously engaged in some or the other physical activity. It is seen that when child reaches school age, accidents in the school environment in the form of falls, injuries due to contact sports, fights, abuse, etc. are very common and the main cause of traumatic dental injuries. Trauma may vary from minor enamel chipping or avulsion to extensive maxillofacial damage, more serious neck and brain injury, which may cause pain, disfigurement and mental agony, having immediate and long lasting effects. In such cases, a school teacher is in the right position to handle such an emergency and refer the child to the concerned dental surgeon or a pedodontist for further needful care. The main reason for delayed treatment of dental trauma is that people present at the site of injury are unaware of protocol of rapid and appropriate management leading to improper first aid treatment. The purpose of this study was to investigate the awareness of a group of school teachers from different schools about the prevention and emergency management of dental trauma in school children, by means of a questionnaire. Then educating them and reassessing their knowledge after a period of 3 months. Unfortunately, the public is unaware of the risks and does not have enough information about first aid emergency treatment or to avoid traumatic injuries.

Conservative restorations of endodontically compromised anterior teeth in paediatric patients: physical and mechanical considerations

AIM

Objective of this in vitro study was to evaluate the influence of fiber post placement on fracture resistance of pulpless anterior teeth restored with standardised Class III and Class IV resin composite fillings.

MATERIALS AND METHODS

One hundred and five human maxillary central incisors were selected and randomly divided into 7 (n=15) experimental groups (endodontic therapy/ endodontic therapy and one Class III resin composite filling/ endodontic therapy and one Class IV resin composite filling/ endodontic therapy and two Class III resin composite fillings/ endodontic therapy, fiber post and one Class III resin composite filling/ endodontic therapy, fiber post and one Class IV resin composite filling/ endodontic therapy, fiber post and two Class III resin composite fillings). Specimens underwent fracture strength test. Means (N) were calculated and data were analysed using 1-way ANOVA and Tukey multiple comparisons tests (p=0.05).

RESULTS

Concerning teeth with two Class III, fiber post placement significantly increased fracture strength values from 603.59 to 864.24 N. Specimens restored with one Class III (795.21 N without post, 936.68 N with post) showed higher fracture strength values if compared with specimens with two Class III, with significant differences just concerning specimens without a fiber post. Fracture strength was not significantly influenced by fiber post placement in Class IV groups (720.71 N without post, 799.69 N with post).

CONCLUSION

Data suggest that fiber post placement may significantly improve anterior teeth fracture strength when at least two Class III composite fillings are associated to the endodontic treatment. No significant effect of fiber post placement could be recorded when just one Class III or one Class IV composite filling were present.

A comparative evaluation of the vertical root fracture resistance of endodontically treated teeth using different root canal sealers: an in vitro study

OBJECTIVE

The objective of this study is to evaluate the vertical root fracture resistance of endodontically treated teeth obturated with - Tubli-Seal EWT/Gutta-percha, AH Plus/Gutta-percha, Epiphany SE sealer/Epiphany point.

STUDY DESIGN

Sixty-five single rooted premolars were decoronated and root length was 14 mm for each specimen. Fifty five teeth were enlarged up to ISO size 40 master apical file with stainless steel K-files using standardized preparation and remaining ten teeth were served as negative control. Then teeth were randomly assigned into different groups depending on sealer used for obturation as follows: Group 1: Negative control-no instrumentation was performed. Group 2: Positive control-gutta-percha with out the use of any sealer. Group 3: Experimental group-gutta-percha and Tubli-Seal EWT root canal sealer. Group 4: Experimental group-gutta-percha and AH Plus. Group 5: Experimental group-epiphany SE sealer and epiphany points. After 72 hours, the specimens were embedded in autopolymerizing resin leaving 7 mm of each root exposed and were subjected to fracture testing under universal testing machine at a crosshead speed of 1.0 mm per minute until the root fractured. Results were statistically analyzed using one-way ANOVA and independent t-test.

RESULTS

Showed that Epiphany SE sealer/Epiphany points showed highest mean fracture resistance and Tubli-Seal EWT group showed the least fracture resistance of all the materials tested. There was no statistically significant difference among experimental groups.

CONCLUSION

Epiphany SE sealer/Epiphany points demonstrated highest fracture resistance values than the other materials tested and intact tooth had highest resistance against vertical root fracture.

CLINICAL SIGNIFICANCE

Epiphany SE sealer/Epiphany points may be one of the materials of choice in the endodontic treatment of teeth.

Does ultra-pulse CO(2) laser reduce the risk of enamel damage during debonding of ceramic brackets?

This study seeks to evaluate the enamel surface characteristics of teeth after debonding of ceramic brackets with or without laser light. Eighty premolars were bonded with either of the chemically retained or the mechanically retained ceramic brackets and later debonded conventionally or through a CO(2) laser (188 W, 400 Hz). The laser was applied for 5 s with scanning movement. After debonding, the adhesive remnant index (ARI), the incidence of bracket and enamel fracture, and the lengths, frequency, and directions of enamel cracks were compared among the groups. The increase in intrapulpal temperature was measured in ten extra specimens. The data were analyzed with SPSS software. There was one case of enamel fracture in the chemical retention/conventional debonding group. When brackets were removed with pliers, incidences of bracket fracture were 45% for the chemical retention, and 15% for the mechanical retention brackets. No case of enamel or bracket fracture was seen in the laser-debonded teeth. A significant difference was observed in ARI scores among the groups. Laser debonding caused a significant decrease in the frequency of enamel cracks, compared to conventional debonding. The increase in intrapulpal temperatures was below the benchmark of 5.5 °C for all the specimens. Laser-assisted debonding of ceramic brackets could reduce the risk of enamel damage and bracket fracture, and produce the more desirable ARI scores without causing thermal damage to the pulp. However, some augmentations in the length and frequency of enamel cracks should be expected with all debonding methods.

Resistance to fracture of roots filled with different sealers

The aim of this study was to compare the fracture resistance of roots filled with gutta percha (GP) and different root canal sealers.Fifty-five human maxillary central incisors were selected and randomly divided into three experimental groups (Groups 1-3) and two control groups (Groups 4 and 5). They were Group 1-15 root canals filled with an epoxy resin-based sealer (AH Plus) and GP, Group 2 -15 root canals filled with a calcium silicate-based sealer (iRoot SP) and GP, Group 3: 15 root canals filled with another calcium silicate-based sealer (MTA Fillapex) and GP, Group 4: five roots were instrumented but not filled, and Group 5: five roots were neither instrumented nor filled. Compressive loading was carried out using a universal testing machine until fracture occurred. Force applied at time of fracture was recorded as fracture strength of specimen in Newtons. There were no significant differences in fracture strength among the three experimental groups (p>0.05), whose results were significantly superior to that of Group 4 (p<0.05). In conclusion, all the root canal sealers used in the present study increased the fracture resistance of instrumented root canals.

Fracture resistance of endodontically treated teeth restored with fiber-reinforced composite posts and composite core with varying remaining coronal tooth structure

BACKGROUND

Endodontically treated teeth often have a varying remaining coronal tooth structure, is an important factor in the successful of post-core with crown restoration.

OBJECTIVE

This study compared the fracture resistance of pulpless teeth with variable amounts of remaining coronal tooth structure restored with fiber-reinforced composite posts and composite core.

MATERIAL AND METHOD

Fifty extracted human premolars were endodontically treated and divided into 5 groups of 10 teeth each. Four groups were prepared having axial wall heights of 4 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, mesial axial tooth structure was removed, mesial and lingual axial tooth structure were removed, mesial-lingual and distal axial tooth structure were removed. For the fifth group, all axial tooth structure was removed to the level of the prepared finish line. All 50 prepared teeth were restored with fiber-reinforced composite posts (FRC Postec Plus) and composite resin cores (Multicore Flow). Testing was conducted with a universal testing machine with the application of a static load to the lingual incline plane of buccal cusp at a crosshead speed of 5 mm/min at 45 degrees to the long axis of the tooth. The load at failure was recorded. The data were subjected to 1-way analysis of variance.

RESULTS

The mean value + standard deviation for the failure load of group 1 to 5 were 237.48 +/- 81.87, 242.97 +/- 66.80, 257.67 +/- 70.42, 239.56 +/- 70.42 and 297.70 +/- 99.42 (N), respectively There were no significant differences in the fracture resistance (p < 0.01). No root fractures occurred in any of the groups.

CONCLUSION

The varying remaining coronal tooth structure of endodontically treated tooth had no influenced on the fracture resistance when restored with fiber-reinforced composite posts and composite core.

Mechanical fatigue cycling on teeth restored with fiber posts: impact of coronal grooves and diameter of glass fiber post on fracture resistance

AIM

The aim of this paper was to evaluate the effect of different diameters and surface characteristics of a glass fiber post on the fracture resistance of teeth restored with fiber posts.

METHODS

Eighty single-rooted bovine teeth were prepared, embedded in a PVC cylinder using acrylic resin, and allocated into 8 groups (N.=10) according to post diameter 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 posts with coronal grooves) G5, G6, G7, and G8 with cervical diameters of 1.4 mm, 1.6 mm, 1.8 mm, and 2 mm, respectively. A self-adhesive cement was used for post cementation, and the core build-up was standardized and made with composite resin. Specimens were stored for 7 days and then submitted to the mechanical fatigue testing (load=50 N., angle= 45°, frequency=1 Hz, temperature=37 ± 1 °C, number of cycles=1000000); the specimens that survived were submitted to static resistance testing (1 mm/min, 45°). The fracture loads and fracture modes was recorded. Data were submitted to 2-way ANOVA, post-hoc Tukey test and Pearson Correlation analysis.

RESULTS

The cervical diameter of the post (P<0.0001) and surface characteristics (P=0.01013) significantly affected the fracture resistance (2-way ANOVA). Grooves reduced the fracture resistance when post diameter was 1.4 mm (G1 and G5). A moderate positive correlation was found between the fracture resistance and the fiber post diameter (r2=0.4445; P<0.0001) (Pearson correlation test).

CONCLUSION

It appears that there is a direct relation between the diameter of the fiber post and the fracture strength of roots restored with fiber posts. But other factors may have influenced the fracture strength such as the reduction of intracanal dentin by the preparation for placement of wider fiber posts, since no difference was found for smooth fiber posts with different diameter. Otherwise, grooves at coronal part of the fiber post can damage the fracture resistance.

Resistance to fracture of roots obturated with novel canal-filling systems

INTRODUCTION

This study was conducted to evaluate and compare the fracture resistance of roots obturated with various contemporary canal-filling systems.

METHODS

Fifty single-rooted extracted mandibular premolars were decoronated to obtain 13-mm root segments. Ten roots were left unprepared and unfilled (negative control). Forty canals were instrumented using 0.06 taper EndoSequence files (Brassler, Savannah, GA). Roots were divided according to the obturating system into 4 groups (n = 10): group 1: iRoot SP sealer (Innovative Bioceramix, Vancouver, Canada) + ActiV GP cone (Brasseler USA, Savanah, GA), group 2: iRoot SP sealer + gutta-percha (GP), group 3: ActiV GP sealer + ActiV GP cone, and group 4: ActiV GP sealer + GP. All groups were obturated using single-cone technique. The roots within each group were embedded in acrylic molds and subjected to the fracture resistance test in which a compressive loading (0.5 mm/min) was applied until fracture. Data were statistically analyzed (analysis of variance and Tukey post hoc test).

RESULTS

The significantly highest fracture resistance was recorded for both the negative control group (381.4 ± 53.2 N) and group 1 (iRoot SP sealer/ActiV GP cone [372 ± 62.9 N]) with no significant difference between them, whereas the significantly lowest value was reported in group 4 (ActiV GP sealer/GP cone [288.3 ± 30.5 N]).

CONCLUSION

Bioceramic-based sealer (ie, iRoot SP) is a promising sealer in terms of increasing in vitro resistance to the fracture of endodontically treated roots particularly when accompanied with ActiV GP cones.

Fracture resistance of composite resin cores with or without prefabricated posts over different substrates

The fracture resistance of endodontically treated teeth has been an obstacle to the durability of the remaining teeth and restorations. The aim of this study was to evaluate the fracture resistance of endodontically treated bovine and human teeth that were restored with either prefabricated metal posts, glass fiber posts, or composite resin cores. Statistical analysis revealed significant difference between different substrates, but there was no statistically significant difference between different types of intraradicular posts or in the interaction between substrate and post types. The intraradicular posts do not increase the fracture resistance of endodontically treated teeth. The metal posts presented more unfavorable fracture modes when compared to glass fiber posts and composite resin cores.