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Year : 2016  |  Volume : 19  |  Issue : 4  |  Page : 364-367
Comparison of fracture resistance of endodontically treated teeth restored with nanohybrid, silorane, and fiber reinforced composite: An in vitro study

1 Department of Conservative Dentistry and Endodontics, K.M. Shah Dental College, Sumandeep Vidyapeeth, Vadodara, Gujarat, India
2 Department of Conservative Dentistry and Endodontics, K.M. Shah Dental College, Vadodara, Gujarat, India

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Date of Submission18-Mar-2016
Date of Decision06-May-2016
Date of Acceptance11-Jun-2016
Date of Web Publication18-Jul-2016


Background: The present study was undertaken to evaluate the most suitable restorative for badly mutilated endodontically treated teeth.
Aims: To evaluate and compare the fracture resistance of endodontically treated premolars restored with conventional nanohybrid, silorane composite with glass fibers and newer fiber-reinforced composite in mesio-occluso-distal (MOD) cavities.
Materials and Methods: Sixty extracted human maxillary premolars were selected. Fifteen intact teeth served as positive controls (Group 1). Endodontic therapy was done in the remaining 45 teeth. MOD cavities were prepared in all the teeth with standardized dimensions and were randomly divided into three groups (Group 2 - nanohybrid + glass fibers, Group 3 - silorane + glass fibers, and Group 4 – fiber-reinforced composite). Restorations were done for all groups. Fracture resistance was measured by Instron universal testing machine.
Statistical Analysis Used: One-way anova test and Tukey's post hoc test.
Results: Highest fracture resistance was shown by intact teeth group followed by fiber-reinforced composite, nanohybrid, and silorane, respectively. Statistically Significant difference was revealed by anova test (P < 0.0001) and Tukey's post hoc test (P < 0.0001).
Conclusions: Among the experimental groups, fiber-reinforced composite showed the highest fracture resistance. Statistically significant difference was observed for all the groups.

Keywords: Fiber-reinforced composite; fracture resistance; glass fibers; mesio-occluso-distal cavity; nanohybrid; silorane

How to cite this article:
Bilgi PS, Shah NC, Patel PP, Vaid DS. Comparison of fracture resistance of endodontically treated teeth restored with nanohybrid, silorane, and fiber reinforced composite: An in vitro study. J Conserv Dent 2016;19:364-7

How to cite this URL:
Bilgi PS, Shah NC, Patel PP, Vaid DS. Comparison of fracture resistance of endodontically treated teeth restored with nanohybrid, silorane, and fiber reinforced composite: An in vitro study. J Conserv Dent [serial online] 2016 [cited 2022 Aug 9];19:364-7. Available from:

   Introduction Top

Restoration of endodontically treated teeth is one of the biggest challenges in the field of operative dentistry.[1] Root canal treatment is incomplete until the permanent restoration is placed. Crown placement followed by root canal treatment is considered to be the gold standard.[2] However, there may be cases where the tooth is still erupting, or where the tooth or root canal therapy has a questionable prognosis, or where the clinician wants to wait and evaluate the healing of a periapical lesion before proceeding with full-crown restorations. There would be situations where both marginal ridges are involved in caries and cannot be restored with amalgam restoration as tooth need to be reinforced using composite. To prevent the failure of root canal treatment, a material with high strength and acceptable clinical performance desirable.[3]

Demand for having tooth-colored restorations has increased among which nanohybrid composites are considered to be the gold standard.[1] However, the major problem associated with the methacrylate-based resin composite is polymerization shrinkage (2.6–7.1%).[4],[5],[6] To reduce the same, a low-shrinkage silorane-based composite material (Filtek™ Silorane, 3M-ESPE, Germany) was introduced.[4],[5],[6],[7],[8],[9]

Both methacrylate and silorane-based resin composites do not have enough fracture resistance to reinforce endodontically treated teeth with extensive loss of tooth structure, which can be improved by incorporating glass fibers.[10],[11],[12]

From the clinical perspective, placement of fibers is a cumbersome, technique sensitive, and time-consuming procedure which can be improved by restoration of fiber reinforced composite.

No study has been done comparing nanohybrid composite and silorane with glass fibers and everX posterior, so the present study aims to compare the fracture resistance of endodontically treated teeth restored with conventional nanohybrid composite, silorane composite resin with glass fibers at occlusal third, and newer fiber-reinforced composite resin in maxillary premolars. The objective of the study was to evaluate the fracture resistance of all the three materials and to find out which restorative material will provide maximum fracture resistance.

The null hypothesis tested will be that there will be no difference in the fracture resistance of intact teeth and those restored with different composite materials.

   Materials and Methods Top

Sixty human maxillary premolars extracted for orthodontic reason were used in the study. Fully erupted teeth with mature apices, intact enamel, and dentin without any carious lesion, restorations, or developmental disturbances were included in the study. Teeth with open apices or resorption, caries, cracks, root fracture, hypoplastic teeth, and previous restorations or with any anatomical variation were excluded from the study. Specimens were disinfected in 0.5% chloramine T-trihydrate solution for 1 week and were cleaned off calculus and periodontal tissue using an ultrasonic scaler.[12],[13] Then, the teeth were stored in distilled water at 4°C until further processing.

Fifteen intact teeth were used as positive controls (Group 1). Endodontic access cavities were prepared in 45 teeth using a water-cooled diamond bur (Endo Access Bur; Dentsply) with an airotor handpiece, and the pulp tissue was removed with barbed broaches. A size 10 K-file (Mani Prime Dental Pvt. Ltd.,) was introduced into each canal until it could be seen at the apical foramen. The working length was determined by subtracting 1 mm from this length.

The canals were prepared by step-back technique with hand K-files. The coronal portion was enlarged with Gates Glidden drill no 3 to 1. Normal saline and 5.25% NaOCL were used as irrigating solution. Subsequently, the canals were dried with absorbent paper points (Dentsply Maillefer) and obturated with gutta-percha and AH Plus root canal sealer (Dentsply De Trey, Konstanz, Germany) using cold lateral condensation technique.

Mesio-occluso-distal (MOD) cavities were prepared in all the specimens using an airotor handpiece with a long straight fissure diamond point (SF - 12C; Mani Dia Burs). Dimensions of the MOD cavities were standardized by keeping the buccal and lingual wall thickness 2.5 ± 0.2 mm from height of contour of each surface, and the gingival cavosurface margin was kept 1.5 mm coronal to the cementoenamel junction.[14],[15] Dimensions of the cavity were measured with the help of Vernier calipers.

Subsequently, teeth were randomly divided into three groups.

Group 2: Teeth restored with nanohybrid composite with glass fibers

Teeth in nanohybrid composite with glass fibers (Group 2) were restored with conventional nanohybrid composite using incremental layering technique. For glass fiber placement, a groove measuring 2 mm in width and 1 mm in depth was prepared buccolingually on the cusp tips whose ends were on the occlusal third of the buccal and lingual surfaces. After etching and bonding, a piece of glass fiber was adapted to the floor of the groove using flowable composite and was light cured. The exposed fiber surface was then filled with composite resin. After removal of the matrix, all the restorations were light-cured from mesial and distal aspect for 40 s, and finishing and polishing of the restorations were done.[14],[15] (Sof-Lex finishing and polishing disk).

Group 3: Teeth restored with Silorane composite with glass fibers

Teeth in silorane composite with glass fibers (Group 3) were restored with silorane-based resin composite. Then, insertion of glass fibers and finishing and polishing were performed in the same manner as described in Group 2.

Group 4: Teeth restored with fiber-reinforced composite with glass fibers

In the case of fiber-reinforced composite (Group 4), walls of the MOD cavities were buildup with nanohybrid composite. A layer of flowable composite was adapted at the pulpal floor followed by placement of everX posterior. Restoration was completed by placing 2 mm layer nanohybrid composite on occlusal surface followed by finishing and polishing.

Thermocycling of the samples was done (500 cycles) at 5°C ± 2°C–55°C ± 2°C with 30 s dwell time and 5 s transfer time.[14],[15] Then, the specimens were stored in an incubator at 37°C for 24 h and mounted in a block of cold cure acrylic resin up to 1.5 mm apical to cementoenamel junction. Layer of light body elastomeric impression material was applied around the root surfaces to simulate the periodontal ligament.[14]

A compressive force at a strain rate of 1 mm/min was applied using Instron universal testing machine by a 0.5 mm diameter round bar, which was parallel to the long axis of the teeth and centered over the teeth until it just contacted the occlusal surface of the restoration.[14] Forces necessary to fracture each tooth were measured in Newtons (N). The data obtained were tabulated and subjected to statistical analysis.

   Results Top

Highest mean fracture resistance was observed with intact teeth followed by fiber-reinforced composite, nanohybrid, and silorane. One-way ANOVA test [Table 1] revealed statistically significant difference (P< 0.0001) between all the groups. Intergroup multiple comparisons were done by Tukey's post hoc test [Table 2] which also revealed statistically significant difference (P< 0.0001) between all the groups.
Table 1: One-way ANOVA test

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Table 2: Tukey's post hoc test (multiple comparisons)

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   Discussion Top

Tooth-colored restorations are in demand for the present generation due to the many advantages; they offer over the metallic restorations. Majority of metallic restorations are now being replaced by high strength composite restorations. Nanohybrid composites are considered to be the gold standard as a posterior restorative due to their dense filler loading, excellent optical properties, and improved mechanical properties. However, still it undergoes polymerization shrinkage (1.6–7.1%) creates contraction stresses which in turn may cause microleakage and subsequently restoration failure.[1]

To overcome the above-mentioned problem, many strategies can be applied such as incremental layering technique, soft start or ramped curing mode, use of glass or polyethylene fibers, or use of a newer low-shrinkage composite such as silorane. Silorane is composed of unique oxirane monomers responsible for the ring opening chemistry of siloxane resin that reduces shrinkage below 1%.[4],[5],[6],[7],[8],[9]

In spite of ample of improvement in the esthetic restorative materials, they are not used for restoring badly mutilated teeth due to their decreased fracture resistance. Luthria et al. have shown that reinforcement of fibers imparts strength and toughness to composite resins. Glass fibers are known to be resistant to tension and are able to stop the propagation of fractures in the composite mass due to their high tensile strength, density, and percentage of elongation allowing them to withstand high stresses without fracturing.[14]

Placement of fibers can be done at gingival, middle, or occlusal part of the cavity, but according to Jafari Navimipour et al., Belli et al., and Oskoee et al., placement of fibers at occlusal third of the cavities significantly increased fracture resistance of the tooth. The anchorage promoted by occlusal fiber in the most approximate position to the applied load leads to a shorter working arm according to Levers principle. Occlusal placement of fibers also keeps the buccal and lingual cusps together through splinting mechanism, recovering the fracture resistance.[11],[14],[15],[16]

A new fiber-reinforced composite everX posterior contains E-glass fibers impregnated within the nanohybrid composite. This premixed material is more convenient to use as it eliminates the need to place the glass fibers in the cavity which is time-consuming and cumbersome procedure. Total inorganic and filler content is 76 wt%/57 vol%. The short E-glass fibers present in the everX posterior prevent and arrest crack propagation that often starts from the surface of the restoration.

Hence, in the present study, everX posterior was compared with nanohybrid and silorane with glass fibers placed at the occlusal third of the cavity.

Maxillary premolars were chosen as they are more prone to fracture due the anatomical shape with steep cuspal inclines, leads to cuspal separation during mastication and greater incidence of fracture than mandibular premolars. MOD cavities were prepared in the teeth as these are considered to be the worst in terms of fracture resistance.[17],[18]

Thermocycling of the samples was done as it simulates in vitro, thermal changes that occur in the oral cavity. A layer of light body elastomeric impression material, polyvinyl siloxane, was applied around the root surfaces before mounting of specimens in acrylic block to simulate the periodontal ligament.[14],[15]

Results of our study showed statistical significance and higher fracture resistance was exhibited by intact teeth (Group 4, 2285.33 N). Fiber-reinforced composite showed an acceptable fracture resistance after intact teeth (1890.93 N). The E-glass fibers present in the material - prevent the crack propagation due to repetitive cyclic fatigue, in contrast to conventional composites and prevent the crack to go below the gingival margin. Nanohybrid composite (Group 2, 1659.93 N) showed higher fracture resistance than silorane composite (Group 3, 1450.40 N). Silorane is a microhybrid composite with larger size and less percentage of filler particles as compared to that of nanohybrid group, which leads to early crack propagation and decreased fracture resistance. No studies have been done till date comparing fiber-reinforced composite with silorane along with glass fibers, and hence, the results of the study cannot be substantiated with those of any other studies.

   Conclusion Top

Within the limitations of this study, maximum fracture resistance is shown by the fiber-reinforced composite after intact teeth. Hence, it can be concluded that everX posterior is the preferred material for restoring extensive cavities over nanohybrid or silorane composite with glass fibers.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Moezizadeh M, Mokhtari N. Fracture resistance of endodontically treated premolars with direct composite restorations. J Conserv Dent 2011;14:277-81.  Back to cited text no. 1
[PUBMED]  Medknow Journal  
Monga P, Sharma V, Kumar S. Comparison of fracture resistance of endodontically treated teeth using different coronal restorative materials: Anin vitro study. J Conserv Dent 2009;12:154-9.  Back to cited text no. 2
[PUBMED]  Medknow Journal  
Luthria A, Srirekha A, Hegde J, Karale R, Tyagi S, Bhaskaran S. The reinforcement effect of polyethylene fibre and composite impregnated glass fibre on fracture resistance of endodontically treated teeth: Anin vitro study. J Conserv Dent 2012;15:372-6.  Back to cited text no. 3
[PUBMED]  Medknow Journal  
Agrawal VS, Parekh VV, Shah NC. Comparative evaluation of microleakage of silorane-based composite and nanohybrid composite with or without polyethylene fiber inserts in class II restorations: Anin vitro study. Oper Dent 2012;37:E1-7.  Back to cited text no. 4
Yaman BC, Dogruer I, Gümüstas B, Efes BG. Three-year randomized clinical evaluation of a low-shrinkage silorane-based resin composite in non-carious cervical lesions. Clin Oral Investig 2014;18:1071-9.  Back to cited text no. 5
Schmidt M, Kirkevang LL, Hørsted-Bindslev P, Poulsen S. Marginal adaptation of a low-shrinkage silorane-based composite: 1-year randomized clinical trial. Clin Oral Investig 2011;15:291-5.  Back to cited text no. 6
Casselli DS, Martins LR. Postoperative sensitivity in class I composite resin restorations in vivo. J Adhes Dent 2006;8:53-8.  Back to cited text no. 7
Moosavi H, Zeynali M, Pour ZH. Fracture resistance of premolars restored by various types and placement techniques of resin composites. Int J Dent 2012;2012:973641.  Back to cited text no. 8
Jafari Navimipour E, Ebrahimi Chaharom ME, Alizadeh Oskoee P, Mohammadi N, Bahari M, Firouzmandi M. Fracture resistance of endodontically-treated maxillary premolars restored with composite resin along with glass fiber insertion in different positions. J Dent Res Dent Clin Dent Prospects 2012;6:125-30.  Back to cited text no. 9
Calburean F, Galbinasu BM, Ilici RC, Patrascu I. Fracture resistance in fiber reinforced composite restorations – Anin vitro study. JMED Res 2014;2014:1-11.  Back to cited text no. 10
Humel MM, Oliveira MT, Cavalli V, Giannini M. Effect of storage and disinfection methods of extracted bovine teeth on bond strength to dentin. Braz J Oral Sci 2007;6:1402-6.  Back to cited text no. 11
Oskoee PA, Chaharom ME, Kimyai S, Oskoee JS, Varasteh S. Effect of two types of composite fibers on fracture resistance of endodontically treated maxillary premolars: Anin vitro study. J Contemp Dent Pract 2011;12:30-4.  Back to cited text no. 12
Belli S, Erdemir A, Ozcopur M, Eskitascioglu G. The effect of fibre insertion on fracture resistance of root filled molar teeth with MOD preparations restored with composite. Int Endod J 2005;38:73-80.  Back to cited text no. 13
Eakle WS. Fracture resistance of teeth restored with class II bonded composite resin. J Dent Res 1986;65:149-53.  Back to cited text no. 14
Marshall GW Jr. Dentin: Microstructure and characterization. Quintessence Int 1993;24:606-17.  Back to cited text no. 15
Steele A, Johnson BR. In vitro fracture strength of endodontically treated premolars. J Endod 1999;25:6-8.  Back to cited text no. 16
Bogra P, Gupta S, Kumar S. Comparative evaluation of microleakage in class II cavities restored with Ceram X and Filtek P-90: An in vitro study. Contemp Clin Dent 2012;3:9-14.  Back to cited text no. 17
[PUBMED]  Medknow Journal  
Kumar V, Devi A, Bhargava R. Comparative evaluation of microleakage in class 2 cavities restored with A nanohybrid composite using three different increment techniques – An in vitro stereomicroscopic study. J Oral Health Community Dent 2014;8:143-7.  Back to cited text no. 18

Correspondence Address:
Dr. Nimisha Chinmay Shah
Department of Conservative Dentistry and Endodontics, K.M. Shah Dental College, Sumandeep Vidyapeeth, Piparia, Vadodara, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-0707.186458

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