ORIGINAL RESEARCH


https://doi.org/10.5005/djas-11014-0041
Dental Journal of Advance Studies
Volume 12 | Issue 1 | Year 2024

Comparison of Fracture Resistance and Quality of Lateral Condensation Obturation in Traditional and Conservative Access Cavity Preparation: An In Vitro Study


Gurkiran Kaur1, Purshottam Jasuja2, Shveta Munjal3, Heena Khurana4, Ekta Gakhar5, Suman Sharma6

1–6Department of Pediatric and Preventive Dentistry, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab, India

Corresponding Author: Gurkiran Kaur, Department of Pediatric and Preventive Dentistry, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab, India, Phone: +91 7696846339, e-mail: kirantoor769@gmail.com

How to cite this article: Kaur G, Jasuja P, Munjal S, et al. Comparison of Fracture Resistance and Quality of Lateral Condensation Obturation in Traditional and Conservative Access Cavity Preparation: An In Vitro Study. Dent J Adv Stud 2024;12(1):13–20.

Source of support: Nil

Conflict of interest: None

Received on: 01 March 2024; Accepted on: 23 March 2024; Published on: 30 April 2024

ABSTRACT

Introduction: Access cavity preparation is indeed a pivotal step in successful endodontic treatment. It ensures efficient removal of diseased or infected tissue, facilitates thorough cleaning, and enables effective shaping and sealing of the root canal system, therefore eventually giving favorable results of the treatment. Conservative endodontic cavity (CEC) preparation aims to reduce the removal of tooth structure while still providing access to the root canal system. Unlike traditional endodontic cavity (TEC) preparation, where the roof of the pulpal chamber is detached, CEC focuses on preserving as much of the tooth architecture as possible, including pericervical dentin. The primary goal is to locate and access the canal orifices while maintaining the integrity of the tooth. Lateral compaction (LC) has been the most widely used root canal obturation technique. Thus, the study objective is to compare the fracture resistance by a universal testing machine (UTM) and to evaluate the compaction quality of lateral condensation (LC) obturation using radiovisiography (RVG) and stereomicroscope.

Objectives:

Materials and methods: Forty extracted permanent mandibular molars were gathered for the study. Through random allocation, they were split into two main groups, group I and group II, each comprising 20 teeth. These groups were then subdivided into two additional subgroups, denoted as group Ia, Ib, group IIa, and IIb, allowing for nuanced examination within the experimental framework. In group I, samples were prepared for determination of fracture resistance. In group Ia TEC was prepared and in group Ia CEC were prepared. Class II mesio-occlusal cavities were prepared for both group Ia and Ib. In group II, samples were prepared for the determination of the compaction quality of LC obturation. In group IIa TEC were made and in group IIb CEC were prepared. A UTM, was employed to test for fracturing for samples in group I, a constant compressive pressure was applied on the central fossa at a 15° angle in the lingual direction to the long axes of the teeth. The speed of pressure application was set at 1 mm/min using a 6 mm round-head tip as before the fracture. Those particular pressures that consequently resulted in concomitant fracture were noted down in Newton units. For compaction quality testing, in group II all samples were subjected to radiographic evaluation in both buccolingual (BL) and mesiodistal (MD) views for the quality of obturation using a four-point scale (Kersten et al. 1987) and then evaluated under stereomicroscope for apical dye penetration (microleakage evaluation) using (WP Saunders et al. 1993) criteria. The data collected was statistically analyzed.

Results: In terms of fracture resistance, group Ib CEC showed higher fracture resistance as compared to group Ia TEC. Whereas, in terms of compaction quality of LC obturation, the group IIa TEC and group IIb CEC showed that, there were no noteworthy differences between compaction quality of LC obturation technique (both radiographic evaluation and microleakage evaluation).

Conclusion: Due to pitfalls of aforesaid in vitro study, it may be summarized as:

Keywords: Conservative endodontic cavity, Dye penetration, Fracture resistance, Lateral condensation, Radiovisiography, Stereomicroscope, Traditional endodontic cavity.

INTRODUCTION

Root canal treatment stands as the foremost choice for preserving teeth afflicted with pulpal disease. Among its initial procedures, meticulous access preparation is paramount, paving the way for subsequent steps in the treatment process.1 Access cavity preparation in endodontic treatment is particularly important because it affects all subsequent procedures and finally the outcome. The final step of root canal treatment is the obturation of the prepared root canal space. Obturation provides three-dimensional hermetic seals for successful root canal treatment. Obturation is usually done with gutta-percha (GP) combined with different root canal sealers.2

In traditionally prepared endodontic cavities (TEC’s), the approach involves the complete elimination of the roof of the pulp chamber, ensuring straight-line access root into the canals.3 However, these types of preparations result in excessive tooth structure removal. It has been previously demonstrated by several researchers that even a difference of 0.5–1 mm of the latter dentin tooth architecture can affect the fracture resistance of the tooth in a significant way.

Fracture resistance of endodontically treated tooth (ETT) is of prime importance as root canal-treated tooth requires almost double the force to qualify for proprioceptive response than a vital tooth. Hence, in access cavity preparation, the focus lies on removing only the necessary amount of tooth structure required for thorough cleaning and shaping of the root canals.4 To conserve tooth structure during access cavity preparation various techniques are proposed based on the principle of minimally invasive endodontics (MIE).

In line with this principle, modern techniques such as conservative endodontic cavity (CEC) preparation or truss access (TA) cavity preparation have emerged. Conservative endodontic cavity involves creating direct access from the occlusal surface to reveal the mesial and distal canal orifices while retaining the intervening dentin intact.5 Preserving this structure mitigates cusp flexion and subsequently lowers the tooth’s fracture susceptibility.

The most common obturation techniques used are cold lateral condensation (LC) and warm vertical compaction. Cold lateral compaction (CLC) is the most widely demonstrated and practiced root canal obturation technique as it is pre-anticipated, economically viable, and permits good apical control.

Root canal obturation failures occur most commonly due to gaps and porosities at the sealer/dentin interface as it allows the re-colonization of microorganisms culminating in failures of the root canal treatment. Therefore, it is important to have a sealer/dentin interface as close as possible.6

A good obturation wards off the infiltration of microorganisms and their toxins, permits the periapical repair, and does not allow further reinfection. Coalescence of GP and an endodontic sealer is popularly used for root canal obturation.

Lateral condensation has been the most widely used root canal obturation technique. Furthermore, it is a benchmark procedure for the evaluation of other techniques as it allows a more successful movement and progressive deformation of GP, which may sequel in a better GP compaction.

So, our study aimed to assess and juxtapose the fracture resistance and the quality of LC obturation between traditional and conservative access cavity preparations in mandibular permanent molars.

MATERIALS AND METHODS

Forty extracted human permanent mandibular molars (Fig. 1) were selected with complete root development and no coronal restoration history. Teeth are excluded with internal resorption, deeply carious molars, vertical fracture in roots, and developmental defects.

Fig. 1: Forty extracted permanent mandibular molars

To eliminate organic debris from the root surface, the teeth samples were placed in a sodium hypochlorite solution. Calculus and remaining soft tissues were removed with the help of hand scalers and curettes and then samples were stored in normal saline.

Prepared samples were classified into 2 groups of 20 teeth each and the respective group was further subdivided into two subgroups:

Group I: (n = 20)—Determination of fracture resistance; Ia (n = 10)— Fracture counteraction ability of teeth using TEC procedure. Ib (n = 10)—Fracture resistance capability of teeth with CEC procedure.

Group II: (n = 20)—Determination of compaction quality of LC obturation IIa (n = 10)—Compaction quality of LC obturation of teeth with traditional endodontic/access cavity (TEC), IIb (n = 10)— Compaction quality of LC obturation of teeth with CEC.

DETERMINATION OF FRACTURE RESISTANCE

For group Ia, traditional endodontic cavity (TEC) preparation involved creating class II mesio-occlusal cavities, by replacing dentin tissue and occlusal enamel amid mesial and distal root canal cavities, and de-roofing the pulp chamber (Fig. 2). Conversely, for group Ib, CEC preparation entailed similar class II mesio-occlusal cavities, with evicting dentin tissue and occlusal enamel among mesial as well as distal root canal openings (Fig. 3). Altogether the orifices maintained a distal marginal ridge of 1.5 mm in thickness and 1 mm length in between the enamel-cement line junction and the gingival margin of the mesial side.

Fig. 2: Traditional cavity (TEC) preparation

Fig. 3: Conservative endodontic/access cavity (CEC) preparation

Preparation Root Canal with Obturation Process

Post preparing the cavities, an ISO no. 15 K file (Mani, Inc. Tochigi, Japan) was used to measure the root canal working length taking a flat non-variable reference. Radiovisiography (RVG) was used to calculate the working length of all the study specimens as it allows adjustment of the contrast, color, and magnification of images. The root canals were made with the step-back technique with the help of Reamers and K-files. While changing the files, 2 mL of a 5.25% sodium hypochlorite solution was used to irrigate the root canals (Septodont Healthcare India Pvt. Ltd.) solution. 2 mL of normal saline was applied for the final irrigation of root canals. After drying with paper points, (Meta Biomed Co. Ltd, Korea) the canals were coated with AH Plus root canal sealer (Dentsply Konstanz, Germany) GP used obdurations by making use of LC technique. Superfluous GP was dislodged from the canal orifices employing a hot burnisher.

Simulating the Periodontal Ligament

Above the enamel-cement line about around 2 mm, all the samples underwent wax coating. Subsequently, working with a PVC mold, samples in total were fixed in self-curing acrylic resin. Upon visual confirmation of polymerization commencement, teeth were extracted from the resin, and molten wax was eliminated with hot water. To mimic the periodontal ligament, the acrylic resin gap was permeated with silicon impression material, and teeth were repositioned within the cleft.7

Sample Restoration

All samples underwent etching using 37% orthophosphoric acid (3M ESPE, Scotchbond, USA) for 30 seconds on enamel and 15 seconds on dentin, followed by a 15 seconds rinse and gentle air drying. Subsequently, a dentin bonding agent (Prime-Dent, Light cure, USA) was applied, followed by 20 seconds of light curing using an LED device unit (Guilin Woodpecker Co. Ltd. China). Access cavities were then revived with complex resin (Te-Econom Plus, Ivoclar vivadent), applied using an oblique incremental technique using an LED light device, and were cured. The occlusal teeth anatomy was reciprocated in consonance with that of mandibular molar teeth (Figs 4 and 5) and SHOFU (finishing and polishing discs) were employed for polishing all restored sample surfaces.

Fig. 4: Composite restoration in TEC

Fig. 5: Composite restoration in CEC

Test for Fracture Strength

Fracture testing involved placing all samples on a UTM, exerting a compressive load at a 15° angle to the longitudinal axes of the teeth, directed from the central fossa in the lingual direction (Fig. 6). Using a 6 mm round-head tip, load was applied at a speed of 1 mm/min to be continued till fracture occurred. Fracture forces were recorded in Newton units. Failures resulting in root fractures vertically below the simulated bone level were classified non-restorable, while adhesive failures above the simulated bone level were tabulated as restorable.

Fig. 6: Testing of samples on universal testing machine

Determination of Compaction Quality of Lateral Condensation Obturation

The Traditional access cavities for Group IIa Conservative access cavities for Group IIb and were prepared and an ISO no. 15 K file was used to measure the root canal working length taking a flat non-variable reference point. Radiovisiography was used to calculate the working length of all the study specimens as it permits adjustment of the contrast, color, and magnification of images. Root canals underwent step-back preparation exercising Reamers and K-files. In the procedure of filing, canals were rinsed in 2 mL of 5.25% sodium hypochlorite solution (Septodont Healthcare India Pvt. Ltd.), followed by final irrigation with 2 mL of normal saline. After drying with paper points (Meta Biomed Co. Ltd, Korea), AH Plus root canal sealer (Dentsply Konstanz, Germany) was employed to coat canals. Subsequent obturation with GP by making use of LC technique was made. Redundant GP was then taken out from canal orifices with a hot burnisher.

After obturation teeth were subjected to radiographic evaluation in both BL and MD views for the quality of obturation using a 4 point scale (Kersten et al. 1987)8 as:

  • Identified as a compact filling material that filled the entire prepared canal, adhered well to the canal walls, and exhibited minimal areas of slight radiolucency (less than 0.25 mm).

  • Identified as a feebly compacted filling that demonstrated irregularities of less than 1 mm in the adaptation.

  • Identified as improperly condensed filling with irregularities less than 2 mm.

  • Identified as poorly condensed filling with irregularities of more than 2 mm.

After radiovisiographic evaluation of TEC (Fig. 7) and CEC (Fig. 8) teeth were coated with nail varnish completely leaving 2 mm of root from the apex and were stored in 2% methylene blue dye at room temperature for 24 hours. Then, samples were washed thoroughly and nail varnish was scrapped off using a scalpel. The samples were then allowed to dry. After drying the samples were subjected to 5% nitric acid for three days to demineralize the teeth at room temperature. The nitric acid solution was replaced daily and shaken using hand thrice a day. As the process of decalcification culminates, the teeth was washed thoroughly. The dehydration process involves a sequence of ethyl alcohol rinses, beginning with an 80% solution left overnight, and then transitioning to a 90% solution for about an hour. Subsequently, 100% ethyl alcohol rinses are conducted for a total of one hour. The dehydrated teeth were then immersed in methyl salicylate until they become clear and then evaluated under stereomicroscope (Fig. 9) for apical dye penetration (microleakage evaluation) using (WP Saunders et al. 1993) criteria as:

Figs 7A and B: Radiographic quality of obturation of traditional endodontic cavity (TEC), (A) Buccolingual view; (B) Mesiodistal view

Figs 8A and B: Radiographic quality of obturation of CEC, (A) Buccolingual view; (B) Mesiodistal view

Figs 9A and B: Apical microleakage evaluation using dye penetration of (A) TEC; (B) CEC

Degree of leakage Depth of dye penetration
0 There is no leakage found.
1 Lesser than 0.5 mm
2 0.5–1 mm
3 Higher than 1 mm

The data collected was then subjected to statistical analysis.

RESULTS

Data was tabulated and statistically analyzed using the Unpaired t-test to compare fracture resistance between group Ia TEC and group Ib CEC (Table 1). The mean fracture resistance was significantly higher in CEC compared to TEC (Fig. 10).

Table 1: Mean fracture resistance of group Ia (TEC) and Ib (CEC) using unpaired t-test mean fracture resistance
Groups Fracture resistance
M mean Standard deviation t-test value p-value
TEC (Group Ia) 1107.29 266.96 –11.304 0.001*
CEC (Group Ib) 2326.43 212.25    

Fig. 10: Mean fracture resistance between TEC and CEC using unpaired t-test

Radiographic evaluation (BL and MD views) and microleakage assessment using dye penetration were employed to compare the LC obturation quality between group IIa (TEC) and group IIb (CEC). The gathered data underwent statistical analysis using the Chi-square test for radiographic evaluation (BL) and (MD) comparisons and microleakage evaluation between TEC and CEC. This analysis revealed no significant differences (Tables 2 to 7 and Figs 11 to 16) in radiographic evaluation or microleakage evaluation between TEC and CEC.

Table 2: Radiographic evaluation (MD) compared between group IIa (TEC) and group IIb (CEC) using Chi-square test
Radiographic evaluation (MD) Groups
TEC (IIa) CEC (IIb)
1 5 2
50.0% 20.0%
2 5 5
50.0% 50.0%
3 0 2
0.0% 20.0%
4 0 1
0.0% 10.0%
  10 10
100.0% 100.0%
4.286 (a)
0.232
Chi-square test; Non-significant difference
Table 3: Radiographic evaluation (BL) compared between group IIa (TEC) and group IIb (CEC) using Chi-square test
Radiographic evaluation (BL) Groups
TEC (IIa) CEC (IIb)
1 7 5
70.0% 50.0%
2 3 4
30.0% 40.0%
3 0 1
0.0% 10.0%
  10 10
100.0% 100.0%
1.476 (a)
0.478
Chi-square test; Non-significant difference
Table 4: Microleakage evaluation compared between group IIa (TEC) and group IIb (CEC) using Chi-square test
Microleakage evaluation Groups
TEC (IIa) CEC (IIb)
0 4 1
40.0% 10.0%
1 5 6
50.0% 60.0%
2 1 3
10.0% 30.0%
p-value 0.236
Chi-square test; Non-significant difference
Table 5: Radiographic evaluation (BL) compared between group IIa (TEC) and group IIb (CEC) using Mann–Whitney U-test
Groups Radiographic evaluation (BL)
Mean rank Sum of ranks z-value p-value
TEC (IIa) 9.35 93.50 –1.009 0.313
CEC (IIb) 11.65 116.50    
Mann–Whitney U test; Non-significant difference
Table 6: Radiographic evaluation (MD) compared between group IIa (TEC) and group IIb (CEC) using Mann–Whitney U-test
Groups Radiographic evaluation (MD)
Mean rank Sum of ranks z-value p-value
TEC (IIa) 8.25 82.50 –1.863 0.089
CEC (IIb) 12.75 127.50    
Mann–Whitney U test; Non-significant difference
Table 7: Microleakage evaluation compared between group IIa (TEC) and group IIb (CEC) using Mann–Whitney U-test
Groups Microleakage evaluation
Mean rank Sum of ranks z-value p-value
TEC (IIa) 8.55 85.50 –1.636 0.102
CEC (IIb) 12.45 124.50    
Mann–Whitney U test; Non-significant difference

Fig. 11: Radiographic evaluation (MD) between TEC and CEC using Chi-square test

Fig. 12: Radiographic evaluation (BL) between TEC and CEC using Chi-square test

Fig. 13: Microleakage evaluation between TEC and CEC using Chi-square test

Fig. 14: Radiographic evaluation (BL) between TEC and CEC using Mann–Whitney U test

Fig. 15: Radiographic evaluation (MD) between TEC and CEC using Mann–Whitney U test

Fig. 16: Microleakage evaluation between TEC and CEC using Mann–Whitney U test

DISCUSSION

The prime motive of coronal access preparation is to establish perpendicular access to canal orifices so that thorough cleaning and shaping of the entire canal length and circumference can be facilitated. Traditional access involves complete removal of the pulp chamber roof, exposing all pulp horns, and ensuring straight-line access to canals, thus enhancing instrumentation efficacy and averting procedural errors. But it causes loss of anatomic structures such as ridges, cusps, and arched roof of the pulp chamber. This might result in increased cuspal deflection during operation which in turn increases the possibility of cuspal fracture.

The damage to tooth structure is the commonest cause of coronal fractures in teeth traditionally (TEC principles) being treated in endodontic procedures. To maintain the fracture resistance of endodontically treated teeth, maximum tooth structure should be preserved.9 A proper and limited endodontic access design may augment the fracture resistance of an ETT.

Therefore, nowadays conservative endodontic access designs have been proposed which may maintain the resistance of an ETT to fracture. Adhering to this principle, CEC is crafted to provide direct access from the occlusal surface, exposing the mesial and distal canal orifices while retaining intervening dentin.10 This preservation mitigates cusp flexion and thereby reduces the tooth’s fracture susceptibility.

In this study, mandibular molar teeth were chosen due to the higher prevalence of vertical fractures observed in endodontically treated posterior teeth. Mesio-occlusal (MO) cavities were prepared in the present study for group I (a and b) directed to mimic prognostic subjects of endodontic treatment as a result of interproximal caries that does not influence the entire occlusal segment of the tooth (class II). Thus there is a paucity for a restorative material that not only restores the lost tooth structure but also boosts the fracture resistance of the residual tooth and improves effective marginal sealing.11

Profound chewing pressure is witnessed by mandibular molar teeth, due to the central occlusal enamel and dentin. With the preparation of CEC, the goal is to redistribute these forces by maintaining the pulpal chamber roof, thereby safeguarding cervical dentin—an essential factor for long-term tooth function and vitality. The outcome of endodontic treatment for teeth primarily relies on two factors: the amount of remaining tooth structure and the durability of the final coronal restoration. These aspects significantly influence the prognosis of the treated tooth. The fracture resistance of endodontically treated teeth augments when restored with bonded restoration, such as resin-based composite. Therefore, in this study composite resin was used for coronal restoration.

Fracture resistance was assessed by applying a compressive load to the central fossa in the lingual direction at a 15° angle to the longitudinal axis of the teeth using a UTM.12 The load applied at a speed of 1 mm/min using a 6 mm round-head tip, continued until fracture, with resulting forces recorded in Newton units. A 15° angle relative to the tooth’s longitudinal axis was chosen to closely replicate clinical conditions in the study.

The study demonstrated that teeth with a CEC design (group Ib) exhibited significantly higher fracture resistance (mean value 2326.43) compared to those with a TEC design (group Ia) (mean value 1107.29). Additionally, group Ib displayed a greater proportion of restorable fractures relative to group Ia.

Albeit CEC has fracture strength higher than TEC, it could elevate the risk of improper canal instrumentation and the occurrence of procedural errors. Additionally, the ideal access cavity as in TEC would permit the whole removal of pulp tissue, debris, and necrotic materials. Despite the fact, that the lesser the access cavity, the more is the risk of bacterial contamination and the possibility of missing a few root canal orifices.13

In endodontic therapy, proper obturation of the radicular space is crucial to impede bacterial ingress into the cleaned and disinfected root canal. This prevents bacterial recolonization and the transmission of toxins from the oral cavity into the periradicular tissues via the root canal.14,15

The aforesaid study was undertaken to compare the compaction quality of the LC obturation technique by using radiographic quality evaluation and apical microleakage evaluation in both TEC and CEC.16 The study groups were subjected to radiographic evaluation in both the BL and MD views for the quality of obturation using 4 point scale (Kersten et al. 1987). Both BL and MD views were studied, as this gave a better view of the adaptation of obturating material which is not feasible in patients. Moreover, a radiographically good obturation appearance does not guarantee a microscopically well-condensed and well-adapted filling impervious to leakage.

The samples were then cleared using the method described by Robertson and Leeb and then evaluated under Stereomicroscope for apical dye penetration.17 The dye penetration was measured from the apex of the tooth (W.P. Saunders et al. criteria 1993).18 The estimation of linear dye penetration is a popular method to find apical leakage of root canal obturation techniques. The dye penetration test is easy to perform. Methylene blue (2%) was used in this study because of its low cost, low molecular weight, and ease of application. Methylene blue is frequently utilized in endodontic fillings due to its exceptional ability to penetrate and tint effectively.

The findings of aforesaid study demonstrated that teeth having TEC (group IIa) [mean rank of radiographic evaluation 9.35 (BL), 8.25 (MD) and microleakage evaluation 8.55] had higher compaction quality of LC obturation as compared to CEC (group IIb) [mean rank of radiographic evaluation 11.65 (BL), 12.75 (MD) and microleakage evaluation 12.45]. But statistically, there is no significant difference in radiographic and microleakage.

It is important to recognize that in vitro studies have inherent limitations, requiring cautious interpretation of their findings. Factors influencing the load-bearing capability of endodontically treated teeth, including adjacent teeth count, occlusal contacts, tooth position, and apical status, cannot be fully replicated in vitro. Additionally, the static loading method differs from the dynamic oral clinical setting. Variability in extracted human teeth and the absence of lateral forces further underscore the limitations of in vitro evaluations, including microleakage assessment.

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