| Abstract|| |
Background: Over a period of the past few years' episodes of dental trauma more commonly coronal fractures of anterior teeth are being increasingly reported in children. Fragment reattachment can be considered as a valid treatment option in such situations. However, ideal medium for storage of fragments before reattachment needs to be explored.
Aim: To compare the fracture resistance of incisor tooth fragments stored in four storage media: Dry air, milk, coconut water, or egg white before reattaching them with G-aenial Universal Flo.
Materials and Methods: Forty-eight freshly extracted maxillary incisors were divided into four groups. Teeth were then sectioned, and fragments were stored in dry air (Group I), milk (Group II), coconut water (Group III), and egg white (Group IV). The fragments were reattached using simple reattachment technique and tested on the Universal Testing Machine. Statistical analysis was performed using one-way analysis of variance and post hoc Tukey's test.
Results: There was statistically significant difference (P < 0.05) in fracture resistance values between the groups. The highest fracture resistance value was demonstrated by Group II, whereas least fracture resistance values were observed in Group IV.
Conclusion: Along with milk, coconut water being tested for the first time can be considered a viable alternative.
Keywords: Fracture resistance; fragment reattachment; G-aenial Universal Flo; storage medium
|How to cite this article:|
Prabhakar AR, Yavagal CM, Limaye NS, Nadig B. Effect of storage media on fracture resistance of reattached tooth fragments using G-aenial Universal Flo. J Conserv Dent 2016;19:250-3
|How to cite this URL:|
Prabhakar AR, Yavagal CM, Limaye NS, Nadig B. Effect of storage media on fracture resistance of reattached tooth fragments using G-aenial Universal Flo. J Conserv Dent [serial online] 2016 [cited 2019 Sep 19];19:250-3. Available from: http://www.jcd.org.in/text.asp?2016/19/3/250/181942
| Introduction|| |
Greater involvement of children and teenagers in contact sports, automobile accidents, and outdoor activities has led to an increased incidence of dental trauma.  The most frequent form being coronal fractures of anterior teeth representing 18-22% of all injuries to dental hard tissues; 96% of them involving the maxillary incisors alone. 
Numerous techniques have been put forth to reconstruct such traumatically injured teeth such as the usage of resin crowns, stainless steel crowns, orthodontic bands, ceramic crowns, and composite resin restorations with and without pins. However, all these interventions tend to sacrifice a lot of healthy natural tissue.  Hence, with the advent of adhesive dentistry; fragment reattachment is increasingly being considered a minimally invasive biological option for managing such injuries. 
Compared to conventional techniques, fragment reattachment offers several advantages the most predominant one being-aesthetics, since it preserves the original shape, color, brightness, and surface texture of enamel. In addition, incisal edges of reattached fragments tend to wear at a much similar rate compared to adjacent natural teeth, unlike other restorative modalities. Furthermore, this technique can be less time-consuming and provide more predictable long-term results. 
The prognosis of the reattached fragment is dictated by the firmness of its' attachment to the tooth and also its' mode of storage immediately following trauma.  Storage medium acts as one of the key determinants since hydration aids to maintain the vitality, esthetic appearance, and the bond strength. , However, there is a paucity of literature on the exact role of the hydrating medium. 
Hence, the present study was planned to compare the fracture resistance of fractured incisor tooth fragments stored in four storage media namely, dry air, milk, coconut water, or egg white which were eventually reattached using a newer nanohybrid flowable composite.
The research hypothesis was framed as there will be a difference in the fracture resistance of reattached tooth fragments stored in four storage media using a nanohybrid flowable composite.
| Materials and methods|| |
Forty-eight freshly extracted permanent maxillary incisors extracted due to therapeutic reasons with intact crown structures were collected. Teeth with defects such as fractures, decalcification, or caries were discarded. Cleaning and removal of tissue remnants on the root surfaces were carried out using curettes and ultrasonic tips. The teeth were disinfected using 0.2% thymol and stored in distilled water until the time they were intentionally fractured. The selected teeth were randomly divided into four groups of 12 each based on the storage medium used.
The procedural steps were as follows:
- Group I: Dry storage
- Group II: Milk as storage medium
- Group III: Coconut water as storage medium
- Group IV: Egg white as storage medium.
- Intentional fracture of freshly extracted sound teeth: The cervicoincisal distance was measured for each of the tooth on the labial surface. One-third of this distance was then calculated and marked on the labial surface from the incisal edge. The tooth was cut on the marked line perpendicular to its long axis with a low-speed diamond disk
- Storage of the fractured fragments in appropriate storage media for 2 h: Immediately after fracturing, the fragments were stored in separate marked containers with appropriate storage media (dry, milk, coconut water, and egg white) for 2 h and the remaining tooth structure was stored in artificial saliva (Pharmacology department, Bapuji Pharmacy College, Davangere) until reattachment
- Reattachment of fractured teeth using flowable composite resin: The fragments and the remaining tooth structure were rinsed in distilled water. Fragments were reattached after 2 h by means of simple reattachment technique. About 37% phosphoric acid was applied to the fragment and the tooth for 15 s, rinsed for 10 s followed by air drying for 5 s. Bonding agent (Prime and Bond NT, Dentsply, India) was applied in two consecutive coats and surfaces were dried for 5 s using an air syringe to allow solvent evaporation. The bonding agent was then light cured for 20 s in the fractured fragment and 20 s in the tooth remnant. Nanohybrid flowable composite G-aenial Universal Flo (GC, India) was applied on the surface of the fragment and tooth remnant. The fragment was then positioned back to the tooth remnant by means of a sticky wax (to carry the fractured fragment). After ascertaining the correct position, light curing was carried out: 1. 40 s labial half 2. 40 s lingual half.
- Incubation of prepared samples at 37°C in artificial saliva: After reattachment, all the samples were kept in artificial saliva and incubated at 37°C for 48-72 h. Each sample was then embedded in a self-cure acrylic resin block such that only the coronal portion of the tooth was exposed
- Fracturing the samples using Universal Testing Machine: All the samples were then subjected to testing using Universal Testing Machine (Hounsfield) within 48-72 h of extraction. The rod of universal testing machine was held perpendicular to the long axis of the tooth at the incisal third of the crown near the bonding line on the labial surface. The load was applied at a crosshead speed of 1 mm/min. The load was increased progressively and the value at which the reattached fragment debonded was recorded in kilograms and converted into Newton (N) using the relationship, 1 kg = 9.81 N. This load represented the fracture resistance of the reattached tooth. The fracture resistance of all the samples was recorded similarly. The data were compiled and put to statistical analysis using the software Statistical Package for the Social Sciences for Windows SPSS Version 16 (SPSS Inc., Chicago, IL, USA). Wherein one-way analysis of variance and post hoc Tukey's test were performed. P ≤ 0.05 was considered statistically significant.
| Results|| |
The values for each group were tabulated, and the mean and standard deviation were calculated for each of the groups [Table 1]. Statistical tests were then applied.
|Table 1: Mean and standard deviation values of the fracture resistance for all the four groups |
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The highest fracture resistance value was demonstrated by Group II, followed by Group III, followed by Group I and least fracture resistance values were observed in Group IV [Table 1]. For group-wise comparison, post hoc Tukey's test was applied and it was seen that there was a statistically significant difference in fracture resistance values between Group I and Group II (P = 0.008 P < 0.05); Group II and Group IV (P = 0.000 P < 0.05); Group III and Group IV (P = 0.007 P < 0.05) [Table 2].
|Table 2: Level of significance on intergroup comparison using post hoc Tukey's test |
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| Discussion|| |
Over a period of the past few years' episodes of dental trauma more commonly coronal fractures of anterior teeth are being increasingly reported due to the changing lifestyle of children and teenagers in the modern era.  The current generation of parents want a very esthetically pleasing and natural remedy for such traumatic injuries. Fragment reattachment can be considered a biologically viable option which not just meets the current expectations but is minimally invasive as well.
The philosophy behind this approach dates back to the early 1960's.  However, the interest in this concept got renewed after it was found that the mode of fragment storage following trauma was a key prognostic determinant.  A study by Farik et al. showed that additional drying of fractured fragment beyond 1 h decreases the fracture resistance significantly, thus emphasizing the importance of keeping the fragment moist.  However, the present study is one of the very few interventions which has solely evaluated the effectiveness of the storage media per se.
Permanent maxillary incisors were selected for this study because of their greater involvement in traumatic episodes.  Previous studies have stated that milk was better in enhancing the fracture resistance of the reattached tooth fragment than dry air. Hence, dry air was taken up as a negative control in the present intervention while milk served as the positive control. ,, In a study conducted to determine the efficacy of egg white in maintaining the viability of human periodontal ligament (PDL) cells on avulsed teeth, it was found that there was no difference in the cell viability between egg white and HBSS media.  Shirani et al. in their study concluded that egg white gave better results when compared to milk and dry air; hence, egg white was considered as one of the test groups.  In a previous study, it was also concluded that coconut water kept PDL cells significantly more viable than HBSS or milk in simulated avulsed teeth.  Hence, it was logical on our part to testify if coconut water gave similar results if used as a storage medium for fragment reattachment as well. Thus, the test groups comprised these four media which are natural as well as readily available.
Lee et al. reported that residual chlorine from saline and sodium hypochlorite can negatively influence the bond strengths when used as storage medium.  Hence, distilled water was chosen as the storage medium for freshly extracted teeth in the present intervention.
In this study, the teeth were cut in a standardized manner using a low-speed diamond disk, as the aim was to evaluate the storage media. The fitting between the fragment and the tooth was not always perfect. However, fracturing a tooth in vitro has its own disadvantages as the fractured fragments produced could be of uneven dimensions. As a result, the amount of material required for reattachment will vary and give inconclusive results. Hence, with this limitation to simulate the natural fracture forces, this procedure of sectioning using a diamond disk was followed as it allows the standardization of the fragment size. 
The storage time was taken as 2 h to simulate a clinical scenario wherein the reattachment procedure is carried out in the same appointment. The technique of simple reattachment was followed as the point of contention here was the hydration media. Dehydration of human dentin has demonstrated a brittle behavior.  Hence, at no point in the entire study was the samples allowed to dry except for the fragments of Group I. The tooth remnants as well as the samples after reattachment were kept in artificial saliva to simulate the natural condition in the oral cavity.
All of the samples were tested within 48-72 h of their extraction to prevent any major variation from occurring in the values between the samples. The direction of load application for fracturing the reattached teeth simulated a clinical scenario wherein a tooth restored using fragment reattachment encounters the second episode of trauma. However, one potential drawback of this study was the amount of load which was applied using the universal testing machine at a crosshead speed of 1 mm/min did not simulate a natural traumatic scenario. 
In our study, the fracture resistance value for Group II was recorded as the highest being statistically significant over Group I and Group IV. It can be attributed to the isotonicity of milk with high water content which allowed adequate rewetting of the dentinal tubules. , This is in accordance to the previous studies. ,, Following Group II, Group III gave the second highest fracture resistance values. Coconut water has higher osmolality than milk.  Furthermore, in previous studies, media with greater osmolality have given better results.  It can also be hypothesized that the water content of coconut water being greater than milk might have allowed better wetting of the dentin preventing the collapse of the collagen fibers which play a role in resin tag formation.  The difference between the fracture resistance values between Group II and Group III were not statistically significant. Group IV demonstrated the least fracture resistance values having a statistically significant difference with respect to Group II and Group III. It could be attributed to the lower osmolality and greater viscosity of egg white as compared to that of coconut water which might have prevented uniform wetting of dentin as a result of which the collagen fibers could have remained in a collapsed state. , This particular aspect of our study is in contrast to a previous intervention by Shirani et al. 
Considering the Indian scenario for the problem in question, there is a greater probability of coconut water being readily available at the site of trauma such as a typical school playground. Hence, this study has the potential to be the eye opener to the fact that the mode of storage of a fragment before its reattachment significantly affects the prognosis. Thus, there is a need to catalyze public awareness about the manner of preservation of such fragments such as their avulsed counterparts.
| Conclusion|| |
Within the limitations of this study, it can be concluded that:
Financial support and sponsorship
- Hydration of the fragment does improve its fracture resistance significantly
- Milk offers the highest fracture resistance values among the tested media
- Coconut water being tested for the first time can also be considered a viable alternative.
Conflicts of interest
There are no conflicts of interest.
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Nandita Shrikant Limaye
Department of Pedodontics and Preventive Dentistry, Bapuji Dental College and Hospital, Davangere - 577 004, Karnataka
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]