Journal of Dr. NTR University of Health Sciences

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 9  |  Issue : 1  |  Page : 6--11

Comparative evaluation of microleakage of conventional crowns and endocrowns using confocal laser scanning electron microscope – An in vitro study


Kakollu Sudha1, Thota Murali Mohan2, Kalagotla Aparna1, Bhupathi Sravanthi Yadav1, Ediga Sandhya Rani1, Dunnala Lakshmi Sowjanya1,  
1 Department of Conservative Dentistry and Endodontics, Government Dental College and Hospital, Vijayawada, Andhra Pradesh, India
2 Department of Conservative Dentistry and Endodontics, Government Dental College and Hospital, Kadapa, Andhra Pradesh, India

Correspondence Address:
Dr. Kalagotla Aparna
Department of Conservative Dentistry and Endodontics, Government Dental College and Hospital, Vijayawada, Andhra Pradesh
India

Abstract

Background and Aims: The purpose of this study was to compare the microleakage of conventional crowns and endocrowns using confocal laser scanning electron microscope. Materials and Methods: Thirty extracted human permanent mandibular molars were collected and sectioned parallel to the occlusal surface at 2 mm above the CEJ to deroof the pulp chamber. Endodontic treatment was performed. The gutta-percha was removed 1 mm below the orifice of each canal, and flowable resin composite was filled in the canals up to the level of the pulp chamber. Samples were then randomly divided into two groups with 15 teeth each according to the type of post endodontic restoration given – Group 1: conventional crowns and Group 2: endocrowns. In Group (1), teeth were restored with composite cores, wide circumferential deep chamfer margin (0.8 mm) was prepared at the CEJ and 2 mm from the occlusal surface, 1.5 mm were cut from the axial walls. In Group (2), preparation was performed by making a circular butt margin with a central retention cavity with rounded internal line angles. Impressions were made, crowns were fabricated, and cementation was done, followed by thermocycling. The specimens were coated with varnish up to 1 mm from the crown margins, placed in Rhodamine B dye for 60 h, rinsed thoroughly for 30 s, sectioned with hard tissue microtome and examined for microleakage. Statistical Analysis: Statistical analysis was accomplished with the Student t-test, and significance was predetermined at P < 0.05. Results: In this study, endocrowns (6.158) showed significantly low microleakage compared with conventional crowns (14.052). Conclusion: Endocrowns showed significantly lower microleakage.



How to cite this article:
Sudha K, Mohan TM, Aparna K, Yadav BS, Rani ES, Sowjanya DL. Comparative evaluation of microleakage of conventional crowns and endocrowns using confocal laser scanning electron microscope – An in vitro study.J NTR Univ Health Sci 2020;9:6-11


How to cite this URL:
Sudha K, Mohan TM, Aparna K, Yadav BS, Rani ES, Sowjanya DL. Comparative evaluation of microleakage of conventional crowns and endocrowns using confocal laser scanning electron microscope – An in vitro study. J NTR Univ Health Sci [serial online] 2020 [cited 2020 Nov 25 ];9:6-11
Available from: https://www.jdrntruhs.org/text.asp?2020/9/1/6/284193


Full Text



 Introduction



Restoration of endodontically treated teeth with extensive tooth loss has always followed, with the fabrication of crowns supported on glass fiber posts and/or metal cores.[1],[2],[3],[4] It was believed that this process would provide better reinforcement.[5],[6] Removing a healthy tooth structure to enable the placement of rigid elements devoid of mechanical characteristics resembling those of the tooth could result in the weakening of remaining tooth.[7],[8],[9],[10] With the increasing popularity of adhesive dentistry, a shift in treatment decisions toward more conservative modalities has been observed. Ceramic onlays and endocrowns have been introduced as alternative restorations for endodontically treated molars.

 Materials and Methods



Specimen preparation

Thirty freshly extracted human permanent mandibular molars with approximately similar mesiodistal/buccolingual dimensions and root length were collected. Teeth were ultrasonically cleansed, stored in a 1% chloramine T solution. Teeth sectioning was done parallel to the occlusal surface, 2 mm above the cementoenamel junction (CEJ) to deroof the pulp chamber and remove occlusal tooth structure [Figure 1]. Pulp tissues were removed with an endodontic file and working length was radiographically determined. Canal enlargement was performed with a rotary NiTi system (ProTaper, Dentsply Maillefer, Ballaigues, Switzerland); irrigation was done with 1% Naocl and canals were obturated. The gutta-percha at coronal one-third (1 mm below the orifice of each canal) of the canal was removed using a small carbide bur and filled with flowable composite (Filtek Z350XT flowable, 3M ESPE, St Paul, MN, USA) up to the level of the pulp chamber. The specimens were then divided into two groups of 15 each depending upon the postendodontic restoration given.{Figure 1}

Group 1: Conventional crowns (n = 15)

Group 2: Endocrowns (n = 15)

The teeth in both groups were individually fixed in fast-cure acrylic resin. The roots were placed in resin up to 2 mm below the CEJ. Ethical commitee approval was obtained. (Ref. No1/IEC-CD-GDCH/2017) Approval date: 29-12-2017.

Tooth preparation for conventional crowns

In the conventional crown group (n = 15), molar teeth were restored with composite cores. Wide circumferential deep chamfer margin of 0.8 mm was prepared at the CEJ and 2 mm from the occlusal surface, 1.5 mm from the axial walls were cut [Figure 2].{Figure 2}

Tooth preparation for endocrowns

Intracoronal height of the prepared walls was reduced to 2.0 mm, which were measured from the floor of the pulp chamber to the internal cavity margin, using a periodontal probe. A standardized cavity was prepared in all teeth using a tapered diamond coated stainless-steel bur with a rounded end (G845KR, Edenta, Basel, Switzerland) by placing it perpendicular to the pulpal floor for removal of undercuts of the pulp chamber and alignment of its axial walls with an internal taper of 8–10 degrees held. All internal line angles in the cavity were rounded and smoothed. The axial walls of the cavity were prepared from the pulpal side to provide for a standardized cavity wall thickness and the preparation was made by making a circular butt margin with a central retention cavity and rounded internal line angles and shoulder finish line at CEJ [Figure 3].{Figure 3}

Conventional crown and endocrown fabrication and thermocycling

CAD/CAM ceramic conventional crowns [Figure 4] and endocrowns [Figure 5] were fabricated with a CEREC AC system using the software package (CEREC 3D, version 3.8, Sirona Dental Systems GmbH, Bensheim, Germany). Before cementation, the marginal adaptation of the conventional crowns and endocrowns was checked and any specimen with a marginal discrepancy was rejected and replaced with a new sample. Intanglio surfaces of all conventional and endocrowns were treated according to the manufacturer's instructions for the respective groups. The etching was done with 5% hydrofluoric acid gel (IPS Ceramic Etching Gel, Ivoclar Vivadent, Schaan, Liechtenstein) for 60 s. Prepared parts of the tooth surfaces were etched with 37% phosphoric acid etching gel for 15 s, rinsed for 20 s, and dried using oil-free air for another 5 s. Dentin primer (Syntac, Ivoclar Vivadent) was applied on the tooth surface for 15 seconds and dried for 10 s, then dentin adhesive (Syntac, Ivoclar Vivadent) was used for 10 s and dried for another 10 s. Adhesive resin (Heliobond, Ivoclar Vivadent) was applied and air blown to a thin layer for 15 s. All specimens were cemented with dual-cure resin cement. The resin cement was light-activated at each surface for 20 s. Samples were preserved in double-distilled water at 378°C for 1 week, which allows for the maturation of the bonded interface. Specimens were subjected to 5,000 thermal cycles in two water baths of 58°C and 558°C with a dwell time of 30 seconds (Thermocycler, Willytec, Munich, Germany). After thermocycling, the surface of each specimen was covered with two coats of varnish up to 1 mm from the crown margins. Samples were soaked in an aqueous solution of Rhodamine B dye for 60 h at 378°C. Then, the teeth were rinsed thoroughly with a water syringe for 30 s.{Figure 4}{Figure 5}

Microleakage testing

Each specimen was sectioned Buccolingually with hard tissue microtome using water cooling, producing five sections from each sample [Figure 6]. The two outermost samples were discarded, and the middle three-tooth sections were used for dye penetration evaluation under confocal laser scanning microscopy [Figure 7], [Figure 8], [Figure 9].{Figure 6}{Figure 7}{Figure 8}{Figure 9}

Results

Dye penetration at the tooth/crown interface at both the buccal, lingual, mesial, and distal margins of each section was measured, and dye penetration for each tooth was calculated from the average of all the readings [Figure 10] and [Figure 11]The mean microleakage values for conventional crowns (14.052) and for endocrowns (6.158) are shown in [Table 1]Statistical analysis was accomplished with the Student t-test and the significance was predetermined at P < 0.05.{Figure 10}{Figure 11}{Table 1}

 Discussion



With the introduction of adhesives into dentistry, the need for using posts and cores has become less. Moreover, the appearance of ceramics with high mechanical strength capable of being acid-etched (such as those reinforced with leucite or lithium disilicate) with the adhesive capacity of adhesive systems and resinous types of cement made it possible to restore posterior teeth, especially molars, without cores and intra radicular posts.[11] Thus, it became feasible to restore teeth with extensive coronal destruction by means of overlay and/or onlay and endocrowns, without the use of radicular posts and while using the entire extension of the pulp chamber as a retentive component.[12],[13],[14] Pissis was the forerunner of the endocrown technique, describing it as the “mono-block porcelain technique.”[12] The nomenclature endocrown was described for the first time by Bindl and Mormann in 1999 as adhesive endodontic crowns, which was characterized as total porcelain crowns fixed to endodontically treated posterior teeth. These endocrowns would be anchored to the internal portion of the pulp chamber and on the cavity margins, thus obtaining macromechanical retention from the pulpal walls and microretention would be attained with the use of adhesive cement.[13]

Endocrown as a relatively emerging technique had a few studies evaluating it. Some of them were in vivo, where the clinical performance of the endocrown was assessed. Others were in vitro and were limited by testing the fracture resistance of the endocrown. To our knowledge, no study so far compared and evaluated the microleakage of conventional and endocrown in vitro conditions, where measurements can be obtained more accurately using the confocal laser scanning microscope. This allows reading the marginal gaps of all surfaces, including mesial and distal surfaces which are hard to asses in the Vivo studies.

The overall mean microleakage of the endocrown group (6.158) was significantly less than that of the conventional crown group (14.052), <0.05.

This may be secondary to the rounded shoulder finish line in the proximal surfaces of the endocrown group, whereas it was deep chamfer in all surfaces of the conventional crown group.[15] This corresponds with the Cho et al. study, where they investigated the marginal fit of two types of crowns [Ceramic optimized polymer (Ceromer) and fiber-reinforced composite (FRC)]. They concluded that the shoulder finish line had better marginal fit than chamfer finish line (P < 0.001).[16]

 Conclusion



Within the limitations of this study, it can be concluded that the microleakage of endocrown was less than that of the conventional crown. Thus better chance of success when crowning endodontically treated teeth. However, further clinical studies are needed to confirm this finding.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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