|Year : 2007 | Volume
| Issue : 2 | Page : 88-92
A comparison of impact strength of fragment-bonded anterior teeth using three different restorative materials: An in vitro study
AR Prabhakar, AJ Kurthukoti, G Kayalvizhi
Department of Pedodontics and Preventive Dentistry, Bapuji, Dental College and Hospital, Davangere - 577 004, Karnataka, India
A R Prabhakar
Department of Pedodontics and Preventive Dentistry, Bapuji Dental College and Hospital, Davangere - 577 004, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background and Objective : The purpose of this investigation was to estimate the impact strength of fractured anterior teeth reattached using three different restorative materials and compare their impact strengths to those of control.
Materials and Methods : Sixty human maxillary permanent central incisors were selected and divided into control and experimental groups. The teeth in the experimental groups were fractured and then bonded using Composite resin, Compomer and resin-modified GIC. Intact teeth served as control. All the specimens were then tested in an impact testing machine.
Results : The results revealed statistically significant differences between Compomer and resin-modified GIC groups, control and experimental groups. No statistically significant differences were observed between Composite resin and Compomer groups.
Conclusion : Thus the fractured fragments bonded with Composite resin and Compomer provided better adhesion than resin-modified GIC.
Keywords: Crown fracture, fragment reattachment, impact strength, trauma
|How to cite this article:|
Prabhakar A R, Kurthukoti A J, Kayalvizhi G. A comparison of impact strength of fragment-bonded anterior teeth using three different restorative materials: An in vitro study. J Indian Soc Pedod Prev Dent 2007;25:88-92
|How to cite this URL:|
Prabhakar A R, Kurthukoti A J, Kayalvizhi G. A comparison of impact strength of fragment-bonded anterior teeth using three different restorative materials: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2007 [cited 2020 Feb 18];25:88-92. Available from: http://www.jisppd.com/text.asp?2007/25/2/88/33455
| Introduction|| |
Tooth injuries constitute an integral part of clinical odontology. It has been claimed that the volume represented by dental trauma and its sequelae within the foreseable future will probably exceed dental caries and periodontal disease. 
Crown fractures in a patient normally occur as a result of impact from falls, contact sports and automobile accidents.  Coronal fractures of permanent incisors represent 18-22% of all traumas to dental hard tissues; of these, 96% involve maxillary incisors (80% central incisors and 16% lateral incisors). 
Treatment techniques for noncomplicated crown fractures have undergone modification over the years.  Recently, a number of clinicians have attempted to use the fractured tooth fragment whenever available to restore the fractured crown.
Tooth fragment reattachment technique represents an important step in the science and art of restoring fractured anterior teeth. Fragment bonding usually establishes superior esthetics, positive emotional and social response from the patient towards the preservation of natural tooth structure and is probably less traumatic to the injured tooth than a procedure involving the preparation and cementation of crown; additionally, it also restores the gross and surface anatomy perfectly. ,
Composite resins have become the most esthetically desirable materials for fragment bonding because of their excellent physical and mechanical properties.  Recently hybrid restorative materials like resin-modified glass ionomers and Compomers have been introduced. 
The major drawback of incisal edge reattachment technique (IERT) is that whenever the patient experiences another traumatic episode, the reattached fragment is most highly prone to refracture. Since comparable studies to test the effectiveness of the newer adhesive restorative materials to resist refracture following fragment reattachment has yet to be reported, this study was planned to estimate the impact strength of newer adhesive restorative materials when used to reattach fractured tooth fragment.
| Materials and Methods|| |
Sixty sound human permanent maxillary central incisors which were noncarious, free from cracks, devoid of developmental defects were selected. The collected teeth were cleaned with a slurry of pumice, washed with soap water and stored in water until use.
The selected teeth were randomly distributed into four groups of 15 each i.e., control (Group I) and experimental groups (Group II, Group III and Group IV).
The experiment consisted of three procedures:
- Fracture of sound teeth
- Reattachment of fractured fragment
- Estimation of impact strength
1) Fracture of sound teeth : All the specimens in the experimental groups were fractured transversely to the long axis of the tooth using two custom-made blades mounted in a vise [Figure - 1]. Intact teeth served as control.
2) Reattachment of fractured fragment: Fragments were reattached to the fractured teeth using Composite resin, Compomer and resin-modified GIC, following the manufacturer's instructions. In the Composite resin and Compomer groups, total etch technique  was followed by application of single-bond adhesive, , cured and then reattached using Composite resin and Compomer; whereas in resin-modified GIC, total etch technique was followed by (vitremer) primer application and then reattachment with resin-modified GIC.
All the bonding procedures were done with the aid of a magnifying lens to ensure proper alignment of fragments. Excess of material on the tooth surface was removed with a scalpel.
After restoration, all the teeth were thermocycled between two baths having a temperature differential of 6°C to 60°C for 100 cycles with a dwell time of 30 seconds in each bath. 
3) Estimation of impact strength: Each specimen was then embedded in an acrylic block such that the long axis of tooth was aligned with the central axis of the block and the fragment-bonded line was aligned parallel to the upper surface of the block with 2.5 mm of the crown exposed. Fifteen intact teeth (control group) were also embedded in the same way.
The acrylic blocks containing the specimen were mounted in an Impact Testing Machine with the tooth axis perpendicular to the pendulum of the testing device [Figure - 2]. The specimen was hit by the pendulum and the impact resistance was recorded in joules (J); recorded values were converted and tabulated in kilojoules (kJ).
The fractured surface area of each tooth was measured by recording a photograph of the surface using a digital camera linked to a computer. The surface areas of the fractured crown embedded in the blocks were measured using AutoCAD 2000 software package (by computing 50 points on each of the respective area boundaries) [Figure - 3]. The values were recorded in mm 2 and then converted and tabulated in m 2 .
Impact strength (kJ/m 2 ) was calculated by dividing the impact resistance (kJ) by the area of fractured surface (m2) and the results were statistically analyzed.
| Results|| |
The mean and standard deviation for the impact strength of intact and fragment-bonded teeth (in kJ/m2) using Composite resin, Compomer and resin-modified GIC were recorded and statistically analyzed using Student 't' test and one-way ANOVA.
The results from [Table - 1] show the comparison of impact strength between various experimental groups using Composite resin, Compomer and resin-modified GIC.
Composite resin (Group II) showed mean impact strength values of 1.42 ± 0.72 with a mean difference of - 0.19, when compared to Compomer (Group III) (1.61 ± 0.67). Thus Composite resin group values were not statistically significant when compared to the Compomer group.
Compomer (Group III) showed mean impact strength values of 1.61 ± 0.67 with a mean difference of 0.67 when compared to resin-modified GIC (Group IV) (0.94 ± 0.72). The Compomer (Group III) showed statistically significant difference of P < 0.05 when compared with the resin-modified GIC group.
Composite resin (Group II) showed mean impact strength values of 1.42 ± 0.72 with a mean difference of 0.48 when compared to resin-modified GIC (Group IV) (0.94 ± 0.72). Thus Composite resin group values were not statistically significant when compared to the resin-modified GIC group.
The results depict that the Compomer group had a statistically significant difference when compared to resin-modified GIC. No statistically significant differences were found when the Composite resin (Group II) values were compared with those of Compomer (Group III) and resin-modified GIC (Group IV).
Graph 1 shows the comparison of impact strength between control (Group I) and experimental groups [Composite resin (Group II), Compomer (Group III) and resin-modified GIC (Group IV)].
The results showed that control group had a statistically significant difference of P < 0.01 when compared to the experimental groups employing Composite resin, Compomer and resin-modified GIC.
| Discussion|| |
Dental trauma represents a significant threat to dental health in the young. Advances in adhesive technology continue to drive a growing minimally invasive treatment philosophy among dentists, as evidenced by the renewed interest in the IERT (incisal edge reattachment technique). IERT (incisal edge reattachment technique), a reattachment technique with a modern adhesive approach and one that requires almost no preparation, is compelling because most incisal fractures occur with minimal or no net loss of tooth structure. 
The most commonly used materials in fragment reattachment were Composite resins ,, and Dentin bonding agents. , Recently, reports involving successful reattachment with GIC have appeared. Since major drawback of IERT is a refracture whenever patient experiences another bout of trauma and since no comparable studies assessing the effectiveness of the newer adhesive restorative materials to withstand a refracture following IERT have been reported, this study was conducted.
In our study, the specimens were fractured transversely to the long axis of the tooth using two custom-made blades mounted in a vise as it closely simulates trauma. , Fracturing of teeth was preferred to sectioning according to the recommendations by Badami et al.  and Gwinnett AJ. 
The IERT procedure can be done with or without preparation. In this study, no bevel was placed on the tooth or fragment according to the recommendations by Farik et al.,  Clinically, this finding is important since the tooth involved undoubtedly has undergone significant trauma. Ideally, it would seem that the restorative procedure should require minimal tooth preparation in order to decrease manipulative trauma to the tooth and chair time. Thus "no preparation" technique better fulfills this requirement compared to the "beveling technique." 
The results from this study, while comparing the impact strength of fragment-bonded teeth within experimental groups using Composite resin, Compomer and resin-modified GIC, showed statistically significant differences between Compomer and resin-modified GIC. This correlates with the study by Alumuammar et al.,  where Compomers showed higher shear bond strength than resin-modified GIC.
The reason for the better performance of Compomers in our study may be due to its composition (the presence of 70% of resin content in Compomer compared to 30% in resin-modified GIC).  Due to the higher resin content in Compomer, it requires the use of an adhesive to provide good adherence to substrate.  So single-bond adhesive was used in our study, which could possibly have led to the results comparable to Composites.
The reasons for obtaining no statistically significant differences between Compomer and Composites could be due to the physical properties of Compomers approaching those of Composites and also the use of single-bond adhesive. ,
The results from the present study revealed that the control group showed higher mean impact strength values when compared to experimental groups using Composite resin, Compomer and resin-modified GIC. These findings are in agreement with the fracture strength values obtained in previous studies. ,,
A study by Farik et al.,  showed higher impact strength values as they used bovine teeth, which were larger in size and thickness, with greater surface area; compared to our study, where human maxillary central incisors were used. This could have led to the variation in the results.
Earlier studies , were conducted in human mandibular anterior teeth, which were smaller in size and they evaluated fracture strength. (Constant and slow speed was used until fracture.) Results of our study cannot be compared with those studies, as we used maxillary central incisors and assessed impact strength (sudden impact).
Though reattaching the original coronal fragment of traumatized anterior teeth restored using Composite resin, Compomer and resin-modified GIC would not withstand a second traumatic blow to the same extent as intact teeth. These materials can be used as a short- to medium-term restoration until an ideal alternative is found.
| Conclusion|| |
Compomers compared to resin-modified GIC demonstrated higher impact strength when fractured fragments were bonded.
No statistically significant differences were observed in the impact strength values of fragment-bonded teeth between Compomer and Composites.
Control group showed statistically significant impact strength values compared to the fragment-bonded experimental groups.
Thus we can conclude that Compomers and Composites provide better adhesion when fractured fragments are bonded. Although these materials are incomparable to intact teeth, they can still be used as semipermanent restorations until a suitable alternative is found.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]
[Table - 1]
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