|Year : 2015 | Volume
| Issue : 1 | Page : 40-43
Shear bond strength evaluation of adhesive and tooth preparation combinations used in reattachment of fractured teeth: An ex-vivo study
Ramachandruni VamsiKrishna, Koppolu Madhusudhana, Aluru Swaroopkumarreddy, Anumula Lavanya, Chinni Suneelkumar, Govula Kiranmayi
Department of Conservative Dentistry and Endodontics, Narayana Dental College, Nellore, Andhra Pradesh, India
|Date of Web Publication||9-Jan-2015|
Dr. Koppolu Madhusudhana
Department of Conservative Dentistry and Endodontics, Narayana Dental College, Nellore - 524 002, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objectives: The objectives of this study were to evaluate the bond strengths of different adhesive materials, different tooth preparation designs and adhesive tooth preparation combinations to reattach fractured incisor fragments. Materials and Methods: The study sample comprised 48 intact human maxillary central incisors divided into two groups A and B. The incisal third was sectioned with a diamond disc. The teeth in Group A were reattached with bonding agent and in Group B with resin luting cement. The teeth in each Group were further divided into three sub-groups based on the preparation designs viz., simple attachment, chamfer on labial surface, groove with shoulder on labial surface and restored with nano-composite. Shear Bond Strength was calculated by applying load incisal to the fracture line. T-test and one-way ANOVA were used to evaluate the bond strength between the groups and within the group respectively. Results: Reattachment with resin luting cement showed high bond strength compared to bonding agent (P < 0.05). Within the subgroups 'groove with shoulder' showed better bond strength compared to simple attachment and chamfer and the result was statistically significant (P < 0.05).Conclusion: Reattachment of fractured fragments can be considered as a good alternative treatment option when the fragment is available.Reattachment with resin luting cement and the preparation design of "groove with shoulder" showed better results.
Keywords: Bonding agent, chamfer, groove with shoulder, luting cement, reattachment, simple attachment, tooth fracture
|How to cite this article:|
VamsiKrishna R, Madhusudhana K, Swaroopkumarreddy A, Lavanya A, Suneelkumar C, Kiranmayi G. Shear bond strength evaluation of adhesive and tooth preparation combinations used in reattachment of fractured teeth: An ex-vivo study. J Indian Soc Pedod Prev Dent 2015;33:40-3
|How to cite this URL:|
VamsiKrishna R, Madhusudhana K, Swaroopkumarreddy A, Lavanya A, Suneelkumar C, Kiranmayi G. Shear bond strength evaluation of adhesive and tooth preparation combinations used in reattachment of fractured teeth: An ex-vivo study. J Indian Soc Pedod Prev Dent [serial online] 2015 [cited 2020 May 31];33:40-3. Available from: http://www.jisppd.com/text.asp?2015/33/1/40/148975
| Introduction|| |
The majority of dental injuries involve the anterior teeth, especially the maxillary central incisors, because of its position in the arch. , The fractured teeth are generally restored using composite resin or complex ceramic restorations associated with metals where the former do not promote adequate long-term esthetics while the later required a significant tooth reduction during preparation. The reattachment of tooth fragment became a more usual procedure because of the excellent retention obtained with the fluid resin, with the development of the acid-etch technique. This treatment may offer several advantages over conventional composite restoration like improved esthetics as enamel's original shape, color, brightness and surface texture are maintained. In addition, the incisal edge will wear at a similar rate to adjacent teeth. , Furthermore, this technique can be less time-consuming, which reduces the cost of the treatment.
Many techniques have been proposed for reattaching the fragment to the remaining tooth: Using a circumferential bevel before reattaching, , placing a chamfer at the fracture line after bonding, , using a V-shaped enamel notch,  placing an internal groove or a superficial over contour over the fracture line. Some authors have also indicated bonding with no additional preparation. ,
In light of many published studies that verified the efficacy of the fragment reattachment techniques, it has become apparent that both the preparation technique and the kind of material used to bond fractured fragments may have significant effects on the fracture strength of such restored teeth.  Hence, it seems reasonable to study fracture resistance of the different designs used to re-attach tooth fragments with the recently developed adhesive systems. The aim of this study was to compare the shear bond strength of two different adhesive materials and three different tooth preparation designs to reattach broken incisor fragments. The preparation designs used were simple attachment, placement of a chamfer, and new technique i.e., placement of 'groove with shoulder'.
| Materials and Methods|| |
The study sample comprised 48 intact human maxillary central incisor teeth freshly extracted for periodontal reasons. The teeth that were within 1mm difference of their mesio-distal widths, with incisal edges intact, free from cracks, caries or any other kind of structural defect will be included in the study.
The teeth were rinsed under tap water in order to remove blood and tissue debris and then stored in distilled water at room temperature until use. All specimens were mounted in standardized self cure acrylic resin mould. After mounting, the teeth were randomly divided into two groups, Group A and Group B with each group comprising of 24 teeth. Group A is again divided into three subgroups A1; A2; A3 with each subgroup comprising of eight teeth. Similarly Group B was divided into B1; B2; B3. The materials and techniques used in Groups A and B are shown in [Table 1] and [Table 2], respectively.
|Table 1: Showing the two main groups and the materials used for reattachment|
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|Table 2: Showing sub-groups in Group A and B with techniques of reattachment|
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The study consists of three procedures: 1) Sectioning of incisal third, 2) Reattachment of sectioned incisal fragments using different adhesive materials and different tooth preparation designs and 3) Fracture of reattached tooth for evaluating shear bond strength.
The teeth were measured on the labial side, from the cervical to the incisal edge, with a digital caliper and the incisal third was sectioned perpendicularly to the long axis of the tooth, with a water-cooled low-speed diamond disc.The teeth in Group A were attached using Total Etch bonding agent (Adper Single Bond 2, 3M ESPE) and the teeth in Group B were attached using resin luting cement (Panavia F 2.0, Kuraray, Japan).
In Group A1, the sectioned fragments were reattached with no additional preparation. In Group A2, after reattaching the fragments, a 1mm depth chamfer was placed along the fracture line on the labial surface using a round diamond point. The preparation was etched, bonded and a layer of nano-composite (Tetric N-Ceram, Ivoclar Vivadent) placed and light cured for 40 sec. Finishing and polishing was done. In Group A3, following reattachment, a 1mm depth shoulder was placed along the fracture line on the labial surface by means of a cylindrical diamond point and a layer of nano-composite was placed as mentioned above. The procedure was similar for Group B except for the fragment reattachment, which was carried out with resin luting cement (Panavia F 2.0, Kuraray, Japan) according to the manufacturer's instructions
All the specimens from the six reattached groups were positioned in the jig adapted in a Universal Testing Machine and the load was applied to each tooth in a labial-to-palatal direction. The force required to fracture 48 teeth was recorded in kilograms. The results were statistically analyzed using SPSS version 16. Group comparison was performed between the two groups using an independent sample t test. Comparison of means of more than two groups was performed by ANOVA. Statistical significance was set at P < 0.05.
| Results|| |
Mean shear bond strength for Group B (24.87 ± 5.35) was significantly higher than Group A (20.63 ± 4.88).T test revealed a statistically significant difference between the two groups [Table 3]. The mean fracture strength values in subgroups of A and B are mentioned in [Table 4] and [Table 5], respectively. One-way ANOVA revealed a statistically significant between the subgroups of A and B.
|Table 3: Comparison of mean fracture strength between Group A and Group B|
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|Table 4: Comparison of mean fracture strength among different subgroups of Group A with one way ANOVA|
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|Table 5: Comparison of mean fracture strength among different Subgroups of Group B with one way ANOVA|
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| Discussion|| |
Only maxillary central incisors were included in the study because in natural conditions also, these teeth are most prone to trauma.  In case of enamel and dentin fracture, as the fracture is quite massive, there are greater chances of availability of intact fragment, which can be bonded to the tooth with the help of reattachment procedure. 
A fractured surface tends to run parallel to the main direction of the enamel prisms, while orientation of the sectioned surface is dictated by alignment of the diamond saw used to section the incisal edge. Therefore, the approximation between the tooth and the fragment was not perfect and sometimes even presented a gap in sectioned groups. Hence, the results obtained in this study should be an underestimation of what could be achieved clinically using these techniques. However, using a saw resulted in smooth surfaces, which is an advantage as the number of defects in the adhesive interface is lower and it allowed to standardize the mode of 'fracture' that would have been otherwise random.  The cross-head speed used to fracture the specimens in this study was 1mm/min as recommended by ISO standard (ISO/TS 11405:2003-Dental Materials-Testing of adhesion to tooth structure).
The high mean bond strength for Group B may be due to the filler content in the luting cement (Panavia F 2.0, Kuraray, Japan) was 78% (wt%), as claimed by the manufacturer, which could be accounted for its high mechanical properties i.e., high physical strength, high wear resistance, high adhesive strengths to a variety of materials,  whereas the bonding agent used (Adper Single Bond, 3M) contains 5-10% wt of colloidal silica filler particles.
Despite significant improvements in adhesive systems and composite resins in the last decades, some limitations are still present with these materials, such as polymerization shrinkage and questionable longevity of the adhesive interface. These critical factors can affect the fracture strength of reattached teeth, being a problem for longevity of the reattached teeth. However, studies conducted have shown that the material combinations used to reattach the fragments are secondary to the technique used which influences the fracture toughness of a reattached tooth.
The lower bond strength for fragments reattached with simple attachment might be due to availability of smaller bonded area, because there was no cavosurface enamel preparation, and also the surface area of the adhesive interface was low, which may have contributed to the lower fracture strength found in Group A1 and B1.  However, many studies showed that with these techniques, the restored teeth do not recover the original mechanical strength. , In fact, the possibility of debonding of the fragment in this group is higher if teeth subjected to any further impact.
The probable reason for chamfer to show a higher value when compared to simple attachment might be due to the reinforcement of the reattachment by preparing a chamfer adjacent to the fracture line and restored with resin composite.  The removal of the aprismatic superficial enamel layer which is richer in fluoride content, favoring the acid etching; increasing the free surface energy, favoring surface wetting; enhancingthe surface area of exposed enamel; providing better marginal seal; better esthetic results, making it difficult to detect the interface; and improving the material retention. 
But the probable reason for Group A2 and B2 showing a lesser value when compared to Group A3 and Group B3, respectively - might be due to concentration of stresses at the fracture line,  because only a small surface area is available for placement of composite resin which cannot withstand the fracturing load.
The probable reasons for the higher values of Groups reattached with "groove with shoulder" (A3;B3) might be due to the enlargement of the adhesion area around the fracture site with an additional preparation in these groups.  Also, the greater the extension of material on that surface, the better the force distribution over a large enamel area  and the higher toughness of resin composite placed on the labial surface is likely to absorb the fracturing load applied to the tooth before its failure. 
| Conclusion|| |
The following conclusions have been drawn from this study:
Reattachment of fractured fragments can be considered as a good alternative treatment option when the fractured fragment is available and resin luting cement will give better results compared to bonding agent. Among the different reattachment techniques, the "groove with shoulder," showed the better result compared to chamfer and simple attachment.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]