| Abstract|| |
This study aimed to determine the influence of post space preparation with peeso reamers on the marginal integrity of a glass Ionomer cement (GIC) root end restoration. Thirty maxillary anterior teeth were disinfected, decoronated to obtain 16mm root lengths, cleaned shaped and obturated rising cold lateral compaction with AH Plus as the scaler: Teeth were divided into three groups of ten teeth each. In Group 1, the post space preparation was done first, followed by GIC retrograde restoration. In Group II , the GIC retrograde restoration was placed first, allowed to set completely and then followed by post space preparation. Group Ill served as the positive control. Teeth were coated with trail varnish and immersed in Rhodamine B dye for 4(s hours and microleakage assessed under 20X magnification rising a sterecomicroscope. Mean leakage of 1211.36 Um was recorded for Group I, 2088.63 Um for Group II and a complete leakage of 3000 Um far Group III. Significant difference existed between Group I & II (p<0.05) and a vets highly significant difference between Group I &III and Group Il & III. It was concluded that after complete setting of GIC, the vibrational energy of post space preparation is capable of disrupting its seal, when it is used for root end restoration.
Keywords: Post space, Microleakage, Glass Ionomer Cement, Root-End Restoration
|How to cite this article:|
Dutta A, Acharya SR, Saraswathi V, Kundabala M. Influence of post space preparation on the marginal integrity of a glass ionomer cement root end restoration : An in vitro study. J Conserv Dent 2005;8:4-13
|How to cite this URL:|
Dutta A, Acharya SR, Saraswathi V, Kundabala M. Influence of post space preparation on the marginal integrity of a glass ionomer cement root end restoration : An in vitro study. J Conserv Dent [serial online] 2005 [cited 2020 May 30];8:4-13. Available from: http://www.jcd.org.in/text.asp?2005/8/3/4/42586
| Introduction|| |
The elimination of microflora that inhabits the root canal system and all subsequent efforts at preventing their re-colonization of this microecological habitat constitutes much of efforts in an endodontic practice. As early as the 1960's Kakehashi and others had conclusively demonstrated the role of micro-organisms in the development of periapical pathosis in the teeth of rats with pulps exposed to the oral cavity  . Since then, all concepts and theories have guided the evolution of root canal therapy into a science which heralds a conservative, non surgical treatment protocol for the successful resolution of such lesions, and to this end, the merit of such an approach is validated by reports of a high success rate  . Nevertheless, the adoption of a surgical approach to endodontic treatment remains an integral component in the attending clinician's options and has been recommended in several instances including when
- Conventional therapy is not possible or has a high probability of failure
- Conventional therapy has failed and the lesion is refractory to a non-surgical approach
- A biopsy is recommended 
The surgical procedure itself involves the exposure of the root end, root end resection, root end cavity preparation, root end restoration followed by suturing of the soft tissues to their respective anatomic positions: all of which should finally result in healing of the periapex of the tooth. For the purpose of a root end restoration, several materials have been recommended which include amalgam, gutta percha, reinforced zinc oxide engenol cements, zinc polycarboxylate, Cavit, Teflon, cyanoacrylate cement, resin composite, compomers, apatite cement, glass ionomer cement (GIC ) and most recently mineral trioxide aggregate (MTA) ,,,,,,,,,,,,,,,. The material chosen for this purpose must be capable of providing a complete apical seal, possess anti-bacterial properties, be biocompatible, non-absorbable, dimensionally stable, radio-opaque, sans moisture sensitivity and with easy manipulation characteristics  . Perhaps the requisite most frequently in focus is the apical seal obtained with the material since this attribute is responsible for preventing the egress of micro-organisms from the root canal to the periapex as well as impeding the traffic of tissue fluid from the periapical environment into the root canal. In the past decade, the use of glass ionomer cement has gained currency as a retrograde restorative material and is supported by several studies. ,,
In a clinical situation where the tooth has a large periapical lesion (that mandates surgical intervention) and also lacks coronal tooth structure, a dowel and core must also be planned as a part of the post endodontic restoration. The treatment strategy therefore becomes two fold and encompasses procedures that relate to the surgery and those that relate to the dowel and core. The preparation of the post space is one of the procedures associated with the latter and has been frequently performed with the aid of mechanical methods (such as the peeso reamer) A literature search failed to reveal evidence of the effect of such manipulation of the canal on the marginal integrity of a GIC root end restoration. This study was therefore undertaken to determine the influence of post space preparation on the microleakage of a glass ionomer cement root end restoration through an in vitro model using Rhodamine B dye as the indicator.
| Materials and Methods|| |
Thirty three freshly extracted maxillary anterior teeth obtained from the Department of Oral Surgery. Manipal College of Dental Sciences, Manipal were used in the study. The surfaces of the teeth were debried of all adhering tissues using a No. 15 scalpel blade (Lister Sterile surgical Blade, Magna marketing, Kanpur, India) and then disinfected by an overnight immersion in 2.59c sodium hypochlorite (Hospital Pharmacy, Kasturba Hospital, Manipal, India). The teeth were then rinsed in tap water and stored moist during the entire course of the study at room temperature. All the teeth were then decoronated using a carborundum disc in a slow speed handpiece to obtain uniform root lengths of 16 mm each. Orifices of the root canals so exposed were then enlarged with a gates dlidden no.3 drill (Mani Inc., Japan). The anatomic length of the root canal was measured and the working length determined by deducting 0.5 mm form this value. Cleaning and Shaping and was performed using K files (Mani Inc., Japan) with an apical enlargement up to size 40. After each instrument change, the canal was irrigated with 5 ml of 2.5% sodium hypochlorite and 5 ml of 0.2% chlorhexidene gluconate (Hexidine, ICPA Health Products, Ankleshwar, India). Smear layer removal was accomplished by irrigating the canal with 10mI of 2.5% sodium hypochlorite. Obturation was performed with 0.02 taper gutta percha cones (Dentsply Maillefer, China) in cold lateral compaction technique using an epoxy resin based sealer (AH Plus, De Trey Dentsply, Konstanz, Germany). The teeth were then stored for 24 hours before they received further manipulation. These were then randomly assigned into three groups, each of which constituted eleven teeth.
Group I : Gutta percha was completely removed from the coronal 5 mm of the root canal by utilizing peeso reamer No.3 (Mani Inc., Japan) and the post space prepared by the same instrument. Smear layer was again removed in a similar manner to what has been previously described. The apical 2 mm of the teeth were resected with a carborundum disc in a slow speed handpiece without placing a bevel. Subsequently, 3mm deep root end cavities were prepared with a tapering fissure diamond point (FG 170-010. Horico Diamond Products, Germany) in a slow speed contra-angle handpiece. The cavity was conditioned with 10% poly acrylic acid (Dentin Conditioner, GC Corporation, Tokyo, Japan) for 15 seconds, rinsed and finally dried with No. 100 paper point (Dentsply India Pvt.Ltd., Delhi, India). GIC (GC Fuji 11, GC Corporation Tokyo, Japan) was mixed according to the manufacturer's instructions and placed into the prepared cavities and it's surface protected with varnish (GC Fuji Varnish, GC Corporation, Tokyo, Japan).
Group II : All teeth in this group first received a GIC retrograde restoration with it's concomitant preparatory procedures. After it's complete set at 24 hours, the post spaces were prepared in the teeth. The protocol for both the procedures was the same as has been described previously for Group I.
Group III : The teeth in this group served as the positive controls with the apices of the teeth being resected followed by a root end cavity preparation (in a manner similar to Groups I and II). However, these cavities were not restored with GIC and neither were the canals prepared for a post space.
The root surfaces of all the teeth were coated with two layers of nail varnish (except at the apex) and allowed to dry. The samples were then immersed in Rhodamine B dye (Reachem Laboratory Chemicals Pvt. Ltd.,Chennai, India) for 48 hours. The nail varnish coatings were then removed (using scalpel blade No.15) and the teeth rinsed in running tap water and subsequently dried. One millimeter deep grooves were made on the buccal and lingual surfaces of the roots and the teeth spilt into two longitudinal halves with a chisel and mallet. A stereomicroscope possessing a CCD camera (SZ-11, Olympus, Japan) [Figure 1],[Figure 1a] with a micrometer (Leitz Wetzlar, Germany) [Figure 2] attached to the eyepieces was used to measure the microleakage in each half of the split tooth at a magnification of 20X. The maximum leakage seen on either of the split segments was recorded as the value for that particular sample. The mean leakage for each group was computed and statistical analysis to compare the difference in the mean leakage of the three groups performed with the Mann-Whitney U test using the SPSS version 10.0 software.
| Results|| |
A summary of the results is presented in [Table 1]. The mean microleakage observed in Group I was 1211.264µm. in Group 11.2088.636 Um and a compete leakage extending the entire length of the cavity (3000µm) in the positive control group (Graph I ). Representative photographs from Group 1. 11 and III are illustrated in [Figure 3],[Figure 4]&[Figure 5] Comparison of Group I and Group III as well as Group II and Group III revealed a very highly significant difference (p<0.005). Comparison between Group I and Group II also revealed a significant difference (p=0.014)
| Discussion|| |
The success of endodontic therapy rests in ensuring the maintenance of an adequate seal at the apex of the tooth following obturation of the root canal system. The preparation of a dowel space is known to disrupt the apical seal of gutta percha and may be affected by factors such as the technique of obturation and the choice of sealer. AH 26 has shown superior results as compared to zinc oxide engenol based sealers in such a situation  . This prompted the use of resinous sealers during obturation in the present study. AH Plus was chosen in preference to AH 26 owing to it's much shorter setting time of 8 hours as against 43 hours for the latter. Lateral compaction was utilized for obturating the root canal and has been the method adopted by several authors prior to post space preparation ,,
Microleakage that occurs at the margins of a root end restoration following root end surgery is a key determinant for periapical healing. Such leakage itself can be influenced by several variables. It has been previously shown that the depth of the root end cavity did play a role in influencing the marginal seal with a 3 mm deep cavity being recommended , This seems plausible as an increased cavity depth leads to a concomitant increases in the contact length of the restorative material, and therefore may aid in decreasing the probability of leakage.
The material used for root end restorations has been a subject of several conflicting reports. Alhaidany and others found GIC to be superior for this purpose as compared to several other conventional materials such as amalgam, heat sealed gutta percha and zinc polycarboxylate cement (in ascending order of leakage)  . GIC has also often been compared with reinforced zinc oxide eugenol cements by Sutimantanakul et al reporting no difference between the two whereas a study by Lim indicating lower leakage values for GIC , . In a recent study GIC has also been evaluated against a contemporary material, namely MTA  . It was proven to be superior to MTA during the first twenty four hours and on a long tern observation over twelve months GIC showed no difference with MTA. GIC, therefore was found to be a material with acceptable sealing properties and was chosen as the material of choice for this investigation. In addition it comes with its own advantages such as fluoride release, Chemical adhesion to dentin, good biocompatibility with periapical tissues and good anti-bacterial property against some endodontic flora  . Besides, in the patients where it has been used for the root end restoration, it has shown to result in good healing of the periapical tissues with a 90% success rate  . It does however has it's own lacunae which include sensitivity to moisture, slow disintergration in contact with tissue fluids and it's plasticity and stickiness impeding condensation in to the root end cavity .
As a part of our protocol, the root end cavity was conditioned for 15 seconds. This stems from evidence by Lim who demonstrated lesser leakage in cavities which received conditioning before the placement of GIC in the root end cavity.  Several methods have been proposed to evaluate the leakage of root end restorations which include dye penetration, radio-isotopes, bacterial penetration, electrical impedance/resistance, Hiatus measurement with scanning electron microscope and fluid filtration. Of these, dye penetration is the most commonly used method, is simple to perform, inexpensive, requiring no special setup and equipment and safer vis a vis radio-isotopes  . Bearing these considerations, it became an imperative choice to use this technique. Several critics of this method have raised the size of the dye molecule as an issue in contention, the molecular size of dye often being smaller than the size of the micro-organisms seen at the apical end of the tooth  . This in most instances is true. It however does not apply to the ability of tissue fluids, which may leak into the apex of the tooth in manner similar to the dye. Such leakage of tissue fluids may help sustain the growth of microorganism that are existing within the tooth. To assess leakage, it therefore becomes important to select a dye that is as small in size as possible and can pass through even through the smallest of discrepancies at the tooth-restoration interface. Another prominent rationale for selecting a small dye molecule finds support in recently published literature which has substantiated the presence of Human Cytomegalovirus and Epstein Barr viruses of the herpes virus family at the periapex of the tooth  . In view of these findings and the role that these viruses may play in causing periapical pathosis it is important for the dye to be in closer conformity to the cell sizes of these organisms also rather than bacteria and fungi alone. Rhodamine B was an appropriate choice since it's molecular size is relatively small measuring only 1 nanometer.
On comparison of the methods used for assessing dye leakage of the retrograde restoration, many authors have used a scoring criteria to grade the extent of leakage , . This method, however is arbitrary and does not allow for an adequate comparison with other studies. A quantitative measurement is a more objective option and can be done with the aid of a scanning electron microscope or with a stereo-microscope possessing a micrometer. The latter was used in the present study. Group I samples of this study were amenable for comparison with other chemically cured conventional GIC based dye leakage studies and we report results similar to Rosales and others who found leakage occurring to the tune of 1276 µm  Barkhodar post. Pelzner and Stark have reported much lesser leakage values of 460 µm 
This is a preliminary study which has attempted to correlate post space preparation with the apical seal of GIC. It was found that GIC root end restoration demonstrated an increase in leakage values when dowel space preparation was done after the placement and complete setting of the material. A possible explanation could be that the vibrations set up in the tooth by the canal preparation procedure, were capable of disrupting the hydrated silicate inorganic co-matrix. At the same time, it may have also disturbed the existing weak polar bonds and the developing salt bridges.
Since this investigation is a pioneer of it's kind there is much scope for further investigations. Other materials such as resin modified glass ionomers and MTA could be investigated in a similar scenario. Other methods of post space preparation, such as with the Brassler instruments could be compared with peeso reamers for their influence on the apical seal of the root end restoration. Focus could also be placed on the influence of post space preparation on the apical seal of GIC when used as a root end cover rather than one that requires cavity preparation. Further investigations could also address issues such as the effect of periodontal ligament and the cushioning that it affords to the vibrations generated and measuring volumetric leakage of the dye.
| Conclusion|| |
Based on this in vitro study, it can be concluded that the vibrational energy of post space prepartion is able to significantly disrupt the apical seal of completely set glass ionomer root end restoration. This was evidenced by significantly higher values of microleakage (2088.636 µm) as compared to teeth in which post space was prepared prior to the root end restoration (1211.364 µm). Therefore to sequence these clinical procedures, we recommend the preparation of post space before a root end surgery where GIC is to be placed as a retrograde restorative material.
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Department of Conservative Dentistry & Endodontics, Manipal College of Dental Science, Karnataka
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 1a], [Figure 2], [Figure 3], [Figure 4], [Figure 5]