1
Original Article Effect of Fiber Resin Coating and Occlusal Preparation Thickness on Endocrown Restoration Jeffrey Dwijayana Susanto1.
Ade Prijanti Dwisaptarini2.
Selviana Wulansari2.
Janti Sudiono3.
Moehamad Orliando Roeslan4 Postgraduate Program of Conservative Dentistry.
Faculty of Dentistry.
Universitas Trisakti.
Jakarta.
Indonesia Department of Conservative Dentistry.
Faculty of Dentistry.
Universitas Trisakti.
Jakarta.
Indonesia Department of Oral Pathology.
Faculty of Dentistry.
Universitas Trisakti.
Jakarta.
Indonesia Department of Oral Biology.
Faculty of Dentistry.
Universitas Trisakti.
Jakarta.
Indonesia Corresponding author:
Selviana Wulansari .
elviana@trisakti.
Background: Tooth rehabilitation after root canal treatment with extensive crown loss is a challenge for clinicians.
Endocrown restorations are indicated for cases of extensive loss of crown structure in conditions where the use of posts is not possible.
The use of fiber resin coating acts as a stress breaker and absorption on the dentin, thereby increasing fracture resistance.
Objective: The objective of this study is to determine the effect of fiber resin coating (FRC) as a core build-up material and occlusal preparation thickness on the fracture resistance of endocrown restorations.
Methods: An experimental study was conducted on 20 extracted molars, and root canal treatments were performed.
The samples were divided into four groups: FRC with restoration thickness of 2 mm.
FRC with restoration thickness of 3.
5 mm, non-FRC with restoration thickness of 2 mm, and nonFRC restoration thickness of 2 mm.
Fracture resistances were tested on the samples using a universal testing machine.
Results: A one-way ANOVA showed a significant difference in fracture resistance values .
<0.
between the tested groups.
TukeyAos post hoc test revealed significant differences in all groups except for the thickness of the 3.
5-mm and 2-mm groups with FRC.
Conclusion: There was a significant difference in fracture resistance between composite resin endocrown restorations with different thicknesses, either with or without FRC as the core build-up material.
Keywords: Endocrown, fiber resin coating, fracture resistance, restoration after endodontic treatment Received : 11-Oct-2023 Revised : 12-Jan-2024 Accepted : 25-Feb-2024 Published online : 28-Apr-2024 Background Rehabilitation after root canal treatment with extensive loss of crown is a challenge for clinicians.
Rebuilding the damaged crown structure of a tooth with an adhesive-based restoration and using a post and crown is a conventional approach.
The material and shape of the post affect the biomechanical properties of a tooth that has undergone root canal treatment.
1 Prefabricated metal posts provide several advantages, such as a simple technique and shorter treatment time compared to cast posts, but the use of prefabricated metal posts does not consider the individual shape of the root canal and proper adaptation to root canals.
This restoration technique has Scientific Dental Journal A Volume 8 A Issue 1 A Januari-April 2024 been proven to provide effective results, but failure often occurs in the form of a fracture that extends to the root area of the tooth.
High stiffness and strength in the restoration that exceeds that of the dentin may be the cause of this problem.
How to treat fractures in teeth after root canal treatment is still a matter of debate.
The biomechanical properties of teeth change after root canal treatment as a result of tissue loss due to pathological processes such as caries.
This creates a need for root canals and preparation for root canals, as well as invasive restorative procedures such as the preparation and fabrication of crowns.
These factors may cause a loss of coronal and radicular tissue structures, making teeth more brittle and increasing the risk of tooth fracture after root canal treatment.
Endocrown restorations can be an alternative to the restoration of posterior teeth that have undergone root canal treatment to overcome this problem.
Endocrown restorations were first introduced in 1999 by Bindl and Mormann as an alternative to post and core Susanto, et al.
: Effect of Fiber Resin Coating and Occlusal Preparation Thickness Endocrown restoration is indicated for cases of large crown structure loss under conditions for which the use of a post is not possible, such as root canal calcification or curved root canals that do not allow intracanal retention to be placed, narrow interproximal spaces, and insufficient space for crowns.
5Ae7 The endocrown restoration technique connects the coronal and core restorations into a monolithic crown with anchorage to the pulp chamber and the cervical margin of the tooth.
Macro-mechanical retention is obtained from the pulp chamber wall, while micro-mechanical retention is obtained through cementation and bonding agents without intracanal retention.
This type of restoration has shown good retention, stability, and mechanical performance, in addition to being able to reduce stress on the dentin.
5 Rocca et al.
state that the use of endocrown may distribute occlusal forces more evenly than the use of posts in root canals.
These adhesive restorations require special preparation techniques to meet the biomechanical criteria so that the form of preparation is different from conventional crown 4 The endocrown does not require the placement of a subgingival margin, reducing the possibility of gingival inflammation and secondary caries recurrence.
Tooth preparation for endocrown restoration is critical in order to meet its biomechanical principles to produce a long-lasting restoration.
Recommended preparation guides indicate a restoration occlusal thickness of 2 mm, a butt joint margin with a height of 1 mm to 1.
25 mm, and a divergence of the pulp chamber wall of 5A to 7A.
Others suggest an occlusal ceramic thickness between 3Ae7 mm.
In vitro studies have shown that the fracture resistance of ceramic crowns increases with increasing occlusal thickness.
The material used for the fabrication of endocrown restorations greatly affects the durability of the restoration.
Glass ceramic lithium disilicate is a ceramic material that can be produced using computer-aided design (CAD) and computer-aided manufacturing (CAD/CAM) technology and has about 70% needle-like crystals by volume in a glassy matrix, which provides high edge strength and fracture resistance.
This allows the material to be used for inlays, onlays, and endocrowns.
9 Lithium disilicate is considered one of the best materials for endocrowns because its adhesive properties obtained from etching allow it to form a micromechanical bond with the resin cement.
The use of composite resin as a material for endocrown restorations has been reported in previous studies.
8,11,12
Sedrez-Porto et al.
showed that composite resin endocrowns have higher fracture resistance than those made with lithium disilicate.
Lithium disilicate endocrowns result in more root fractures than those made with composite resin.
Fiber resin coating (FRC) resin is a type of composite material consisting of a polymer matrix reinforced with very thin and fine fibers.
The polymer matrix consists of monomers that have been polymerized and has the function of uniting the fibers with a composite structure.
Based on in vitro study results.
FRC may increase a restorationAos strength, allowing it to be used to repair tooth cusp.
In addition to increasing the strength of the restoration, the addition of glass fiber to the composite resin material generally prevents cracks in the teeth that are placed above the cemento-enamel junction because the fiber layer functions as a stress absorber and stops the crack from spreading.
4 FRC materials can mimic the stress-absorbing ability of dentin.
The use of FRC as a core material has been variously reported and demonstrates an increase in the fracture resistance of the 4,13 The aim of this study is to determine the effect of FRC as a core material on the fracture resistance of endocrown The thickness of an endocrown restoration has an important role in fracture resistance as reported in the literature.
however, there are differences in the occlusal preparation thickness guidelines suggested by various studies, indicating that there is no gold standard for endocrown restoration occlusal preparation thickness.
Therefore, occlusal preparation thickness is a factor that will be considered in this study.
Materials and Methods This study was an experimental laboratory study to examine the effect of FRC with different occlusal preparation thicknesses .
mm and 3.
5 m.
on the fracture resistance of composite resin endocrowns.
The group without the fiber resin coating became the control group.
This research was conducted at DMT Core (Dental Material and Testing Center of Researc.
Faculty of Dentistry.
Universitas Trisakti.
Jakarta, in May 2022.
The study sampled mandibular first and second molars.
The teeth were freshly extracted and were obtained from a clinic in West Jakarta.
The research has been approved by Ethics Committee for Health Research Faculty of Dentistry.
Universitas Trisakti number 533/S2-Sp/ KEPK/FKG/10/2021.
The inclusion criteria were mandibular first or second molars, with or without caries, and teeth with crown fractures.
The exclusion criteria were teeth with root fractures.
A total of 20 samples were randomly assigned to four test groups based on the treatment.
Group 1 was a test group with FRC and a 2-mm occlusal preparation.
Group 2 was a test group with FRC Scientific Dental Journal A Volume 8 A Issue 1 A Januari-April 2024 Susanto, et al.
: Effect of Fiber Resin Coating and Occlusal Preparation Thickness and a 3.
5-mm occlusal preparation.
Group 3 was a test group without FRC and a 2-mm occlusal preparation, and Group 4 was a test group without FRC and 3.
5-mm occlusal preparation.
Tooth samples were attached to PVC tubes with selfcured acrylic resin (Fig.
Prior to treatment, all tooth samples were impressed using REVEAL Clear Matrix (Bisco Inc.
USA) on a stock tray (Fig.
1b and 1.
to make a guidance mold for maintaining the occlusal shape of the sample so that the endocrown restoration could reproduce the anatomical shape of the tooth.
The silicone guide index was then marked according to the sample numbering.
on the guide index, then the tooth sample, to which had been applied a thin Vaseline separating agent, was replaced on the index according to the numbering that had been given.
The composite resin was polymerized using a LEDEXE LED Light Curing Unit for 20 seconds.
After polymerization was complete, the endocrown restoration was evaluated to determine whether there were parts that had not polymerized completely before proceeding with the cementation procedure.
Fabrication of the endocrowns was followed by the restoration cementation stage.
All tooth samples were etched using Etchant .
USA) for 15 seconds and rinsed using flowing water before being dried with air Adper Signle Bond 2 .
USA) bonding agent was applied using a microbrush on the prepared tooth surface and polymerized using an LEDEXE LED Light Curing Unit for 20 seconds at an intensity of 1,000 mW/ The endocrown restoration was cemented using RelyX Ultimate resin cement .
USA).
Excess resin cement was cleaned using a microbrush.
Polymerization was carried out using the LEDEXE LED Light Curing Unit for 20 seconds at an intensity of 1,000 mW/cm2 on the buccal, lingual, mesial, distal, and occlusal sides.
Figure 1.
Tooth samples attached to PVC tubes.
tooth samples impressed using REVEAL Clear Matrix.
mold of the anatomical crown shape of a tooth sample.
The occlusal reduction margin was measured using a caliper and then marked with a pencil.
Measurements of 2 mm in Groups 1 and 3 and 3.
5 mm in Groups 2 and 4 were measured from the tip of the buccal cusp (Fig.
The root canal access opening was carried out until it reached the orifice using an endo access bur, then occlusal preparation was carried out using a flat wheel diamond bur up to the marking line.
The butt joint margin was used as a preparation finishing margin.
The pulp chamber was filled with everX PosteriorE Fiber Resin Woven core material (GC Corp.
Japa.
and coated with Filtex Z350 XT .
USA) flowable composite resin for Groups 1 and 2, while Groups 3 and 4 only used Filtex flowable composite resin Z350 XT as the core material (Fig.
The core material was filled to 2 mm below the margin of the pulp chamber and polymerized using a LEDEXE Light-Emitting Diode (LED) Light Curing Unit (DentMate.
Taiwa.
for 20 seconds (Fig.
Endocrown restoration was made using Filtex Z350 XT composite resin paste.
The endocrown was made using the silicone guide index that was created before the tooth was prepared (Fig.
The composite resin was placed Scientific Dental Journal A Volume 8 A Issue 1 A Januari-April 2024 Figure 2.
Tooth preparation using a diamond bur.
FRC application as the core material.
FRC polymerization using a light curing unit.
fabrication of endocrown restorations with composite resin using silicone guide indexes created before the teeth were A universal testing machine was used to measure the fracture resistance (Fig.
A load was applied to the center of the composite resin material sample, starting from 0 kilonewtons .
N) continuously at a speed of 1 mm/minute until the fracture occurred.
The values obtained were then converted using a formula to obtain fracture resistance values in megapascals (MP.
The formula used to measure compressive strength was EE (MP.
= FeOiA, where uyce .
n newton.
is the maximum Susanto, et al.
: Effect of Fiber Resin Coating and Occlusal Preparation Thickness failure load, and c .
n mm.
is the cross-sectional area of the specimen surface.
Table 1.
Fracture resistance values of composite resin endocrown restorations based on the core materials and the restoration thickness .
n MPa unit.
Core Materials and Restoration Thickness Without fiber resin coating Mean A Standard Deviation (Mp.
A Thickness of 2 mm 383 A 0.
Thickness of 3.
5 mm 589 A 0.
With fiber resin coating A Thickness of 2 mm 496 A 0.
Thickness of 3.
5 mm 748 A 0.
A one-way ANOVA was used for hypothesis testing in this study (Table .
There was a statistically significant difference in fracture resistance values between the groups tested .
<0.
To determine which tested groups had significant differences.
TukeyAos post hoc test was applied.
Table 2.
Comparison of fracture resistance values of composite resin endocrown restorations based on the core material and the restoration thickness.
Mean Figure 3.
The sample mounted on a universal testing machine for fracture resistance testing.
The data obtained were subjected to normality testing and showed a normal distribution for each test group.
Hypothesis testing was carried out using a one-way ANOVA, and significant results were obtained .
<0.
TukeyAos post hoc test was used to analyze which groups had statistically significant differences.
The significance value used was p<0.
Results Data were tested for normality using the Shapiro-Wilk test, and it was found that all test groups had normal data distribution .
Ou0.
The mean value of the group without FRC with a restoration thickness of 2 mm had the smallest fracture resistance value .
383 A 0.
055 Mp.
among the four test groups, while the largest mean value was found on the FRC group with a restoration thickness 5 mm .
748 A 0.
083 Mp.
The complete results of the mean and standard deviation for each test group are shown in Table 1.
p value Square Fracture *Significance p<0.
TukeyAos post hoc test results, shown in Table 3, demonstrate that there was a significant difference in fracture resistance values between the 2-mm endocrown restoration without FRC group compared to the other groups .
<0.
Similar results were observed in the 3.
5-mm endocrown without FRC group, as well as the 2-mm endocrown with FRC group, when compared to the 3.
5mm endocrown with FRC group .
<0.
A non-significant difference in value was found between the 3.
5-mm endocrown without FRC group compared to the 2-mm endocrown without FRC group .
=0.
Scientific Dental Journal A Volume 8 A Issue 1 A Januari-April 2024 Susanto, et al.
: Effect of Fiber Resin Coating and Occlusal Preparation Thickness Table 3.
TukeyAos post hoc test results for fracture resistance values between groups of composite resin endocrown restorations based on the core material and restoration Tested Groups Mean Differences 2 mm and 3.
5 mm 2 mm (FRC) and 3.
5 mm (FRC) 2 mm and 2 mm (FRC) 5 mm and 3.
5 mm (FRC) 2 mm and 3.
5 mm (FRC) 5 mm and 2 mm (FRC) *Significance p<0.
Discussion Endocrown restoration is an adhesive restoration method that has been proposed for restorations of endodontically treated teeth with extensive loss of the crown structure as an alternative to more invasive conventional restorations.
Endocrown is a monobloc restoration that can support more stress loading compared to conventional restorations comprising multi-interfacial combinations of posts, core materials, and crowns.
Endocrown preparation does not require a ferrule, thus minimizing the removal of the enamel and dentin structures required for ideal bond strength.
14,15
Using composite resin as a restorative material for molars provides advantages, such as lower cost, a simpler fabrication process, and easier handling and reparation in the case of partial restoration fractures, compared to ceramic restorations.
14 Based on finite element analysis and in vitro study results, composite resin endocrown restorations have a uniformly distributed load compared to ceramic restorations.
Therefore, they have better fracture resistance.
However, more research is needed, particularly long-term clinical trials.
Molar teeth were used as samples in this study because endocrown restorations are generally indicated for posterior teeth.
17 In clinical trials, endocrown restoration on premolars has shown a higher failure rate due to the smaller adhesion area and higher crown height compared to molars, and the difference in the crown height ratio causes greater leverage on premolars.
15,18
The fracture resistance test in this study was completed using a universal testing machine.
Loading was carried out on the central groove area because it is the point that is most prone to fracturing, as reported by Saratti et al.
Scientific Dental Journal A Volume 8 A Issue 1 A Januari-April 2024 from fractographic testing of composite resin endocrown The fabrication of composite resin endocrown restorations was a complicating factor in this study due to the limited availability of composite resin blocks for milling on the market.
To overcome this problem, endocrown restorations were made using composite resin paste with the guidance of a silicone index made from polyvinyl siloxane (PVS), so the height of the restoration was uniform to 2 mm or 3.
5 mm.
PVS materials are available with varying viscosities.
The higher the viscosity, the more filler there is in the material, thereby increasing accuracy and reducing constriction.
By contrast.
PVS materials with low viscosity show larger dimensional changes after polymerization due to the presence of less 19,20 The material used in this study was a medium-viscosity, transparent PVS because it is able to provide good accuracy, and the transparency of the material allows for the polymerization of the composite resin using a light curing unit.
FRC was introduced as a material to replace dentin and was intended to absorb the received loads in order to minimize the risk of fracture.
Several studies have shown that FRC may support the remaining tooth structure and increase the durability of the definitive composite restoration.
21Ae24 The low modulus of elasticity materials tends to absorb loads and concentrate them within the material without transmitting them to the tooth structure.
A 3D
finite elements analysis by Ozkir showed that materials that absorb loads tend to have a high failure rate, but this may protect the tooth structure.
25,26
The results of this study indicate that there was a significant difference in fracture resistance values between the group without FRC compared to the group with FRC, both at 2-mm and 3.
5-mm endocrown restoration thicknesses.
The groups with FRC showed better fracture resistance values compared to the groups without FRC.
This shows that the use of FRC, which in this case was everX posterior (GC Corp.
Japa.
, may increase the fracture resistance of composite resin endocrown restorations compared to flowable composite resin as the core Lassila et al.
reported similar results.
in their study, the everX flow and everX posterior materials had higher fracture hardness than the other short FRC materials and bulk fill composite resins tested.
The fracture hardness value of everX posterior material is 2.
6 MPa m1/2, and there is no composite resin material that has a higher value.
Microfiber has a strengthening mechanism derived from the fiberAos ability to prevent crack propagation, bridging as well as preventing opening when cracks occur.
The reinforcing effect of this fiber filler depends on the load transmitted by the polymer matrix Susanto, et al.
: Effect of Fiber Resin Coating and Occlusal Preparation Thickness to the fiber and the characteristics of the fiber as a crack 22,27 Garoushi et al.
showed that fiber filler may stop crack propagation and increase the fracture resistance of composite resin restorations.
28 These short fibers have the ability to reduce load intensity at the crack point, which is the origin of the crack spreading, so it may Increase the fracture resistance of a restoration.
addition, the use of short FRC as a core material for endodontically treated teeth results in smaller microgaps and better load-bearing area capacity.
24,27
This study shows that there is a significant difference in fracture resistance between 2-mm endocrown restorations compared to 3.
5-mm endocrown restorations, regardless of the use of FRC.
An endocrown restoration with an occlusal thickness of 3.
5 mm has better fracture resistance than an endocrown restoration with an occlusal thickness of 2 mm.
Previous in vitro studies have demonstrated that fracture resistance will increase with an increase in the occlusal thickness of ceramic or composite resin endocrown restorations.
The occlusal thickness of endocrown restorations generally ranges from 3 mm to 7 mm.
7,15 An in vitro study by Turkistani et al.
showed different results.
The highest fracture resistance strength was obtained in the endocrown group with a restoration thickness of 3 mm compared to 4.
5 mm and 6 mm.
This difference in results may be due to the use of non-anatomical samples and oblique loading.
An increase in crown height may cause restoration flexing and increase leverage when receiving a load, which causes high stress on the tooth, restoration, and tooth-restoration A comparison of fracture resistance values between the 5-mm endocrown restoration group without FRC and the 2-mm endocrown group with FRC did not reveal a significant difference.
This indicates that the use of FRC as a core material in narrow restoration spaces may provide similar results as restorations with adequate height.
Therefore, the use of FRC may be recommended to obtain maximum results.
The failure of an endocrown restoration is more related to the height position of the load exerted on the crown than to the construction concept of the restoration itself.
Determination of the restoration thickness, the position of the finishing line, and the location of the occlusal contact with the opposing teeth are crucial.
30 Extended preparation into the pulp chamber by 3 mm, as well as expansion in the axial plane, indicates better load distribution on the tooth and restoration surfaces.
18 The force applied on the cuspal plane must be considered because that is the initial cause of the crack that leads to the central groove.
Design reconstructions with less steep cusp slopes, more rounded central grooves, and arranged occlusal contacts to avoid exaggerated contact during mastication should be considered to provide long-lasting composite resin endocrown restorations.
This laboratory experimental study has some limitations in its simulation of clinical conditions.
Clinically, restoration fractures can be caused by cyclic loads received in various directions, so the application of static loads at just one point is a weakness in this study.
The use of natural teeth is one way to mimic clinical conditions in the oral cavity, so the results obtained may describe how the restoration attaches to the natural teeth and simulate the fractures that occur.
Conclusion There was a significant difference in fracture resistance between composite resin endocrown restorations with a thickness of 2 mm compared to 3.
5 mm, regardless of whether FRC was used as the core material.
There was no significant difference in fracture resistance between 5-mm composite resin endocrown restorations without FRC compared to 2-mm composite resin endocrown restorations with FRC as a core material.
Conflicts of Interest There are no conflicts of interest.
References: