Modern versus Traditional Endodontic Access Cavity Designs

Abstract

By creating a precise access cavity (AC) and finishing the pulp chamber, less invasive endodontic therapy attempts to improve conventional endodontic therapy. The cingulum, oblique ridge, and roof of the pulp chamber, which all play a vital role in functional activity, might be preserved to increase fracture resistance. To reduce tooth structure loss, endodontic new ACs have recently been created. The preparation of the conservative access opening had advanced to a new level with the advent of microscopes and improved root canal equipment. The conservation of the cervical dentin is the most essential factor in preserving the restored tooth's normal function and lifespan. In recent years, minimally invasive endodontics has posed a challenge to the traditional method.

INTRODUCTION

Several access cavity (AC) designs involving minimum tooth tissue removal have been developed in the recent decade for gaining admission to pulp chambers during root canal therapy.[1] Endodontic modern AC designs have lately been developed to reduce tooth structural loss.[1] The debates should not be over whether to completely or partially unroof the pulp chamber roof, or whether to drill a ninja AC or use truss access; ultimately, the outlines of the AC are influenced by anatomical issues, skills, and the tools and methods used to open, clean, shape, and obturate various root canal systems.[2] The maintenance of the pericervical dentin is the most important aspect in retaining the normal function, esthetics, and durability of the treated tooth. Previous research has shown that utilizing more limited AC designs improves the fracture resistance of endodontically treated teeth and reduces the need for more complex, more expensive postendodontic restorations. In recent years, the conventional approach to endodontics has been challenged by minimally invasive endodontics.[2]

TRUSS ACCESS CAVITY

Trials using more conservative (Cons) AC designs, such as the Truss AC, have previously been found to increase endodontically treated teeth's fracture resilience and minimize the need for elaborate, more expensive postendodontic restorations. “Truss” AC is a Cons endodontic AC (Conservative Endodontic Access Cavity (CEC)) technique.[1] Its aim is to keep the dentinal bridge in place between two or more small cavities made to access the canal orifice(s) in each multirooted tooth root.[2] Separate cavities are formed in the mandibular molars to approach the mesial and distal canal systems, whereas, in maxillary molars, the mesio- and disto-buccal canals are accessed via one cavity, while the palatal canal is addressed through another.[1]

ULTRA CONSERVATIVE (NINJA) ACCESS CAVITY DESIGNS

Endodontically treated teeth may have increased fracture strength as a result of this minimally invasive procedure. Cone-beam computed tomography imaging was used to find all of the canals, preserving the dentin in the process.[3] The access outline form was created by drawing a line from the outer canal surface at the furcation level to the outer canal surface at the orifice level on the outer canal wall.[4] At the most deep point of the occlusal surface, a diamond round bur can be utilized to open the cavity perpendicularly. Using a steel round bur to penetrate the pulp after reaching the dentin, the cavity should next be gently enlarged buccolingually with a fissure bur after the pulp chamber has been reached. The cavity's mesiodistal width should be 2 mm, while the buccolingual width is adjusted to 3 mm.[5]

CARIES-DRIVEN ACCESS

Several AC designs utilizing minimum tooth tissue removal for gaining admission to pulp chambers during root canal therapy have been described in the previous decade.

Caries-driven access cavity

Caries is removed and all remaining dental structures are preserved. Included in this is the soft structure, which may be described as the bottom of an architectural feature like a wall or a ceiling corner.[2]

Restorative-driven access cavity

Access to the pulp chamber is achieved in restored teeth with no caries by removing all or part of the current restorations while maintaining all feasible residual tooth components.[2] A diagnostic radiograph that shows the anatomy of the tooth and the morphology of the root canals are required to prepare minimally invasive ACs because it offers a first orientation about where the pulp chamber and root canals are located.[6] One of the most challenging aspects of using minimally invasive ACs is determining where to place root canals due to the restricted view of the pulp chamber floor that may be provided. Rover et al. (2017) observed traditional (Trad) AC found more second mesiobuccal canals in maxillary molars than Cons AC. While using ultrasonic troughing in combination with magnification, there was no difference between the two methods.

Conservative access cavity

Treatment with Cons endodontic cavities (CEC) increases tooth fracture resistance but impairs canal instrumentation in the long run. Despite the fact that CEC was shown to increase the risk of canal instrumentation failure only in the molar distal canals, it maintained the coronal dentin and improved the fracture resistance of mandibular molars and premolars.[7]

EFFECT OF MODERN ACCESS CAVITY DESIGNS ON FRACTURE RESISTANCE OF ENDODONTICALLY TREATED TEETH

When compared to nonendodontically treated teeth, teeth that have been treated endodontically have a decreased long-term survival rate, resulting in lower breakage resistance. As a result, the fact that root canal treatment is a causal factor for tooth fracture caused by loss or reduction in tooth structure has been raised to the attention of numerous clinical investigations.[8] Teeth fracture resistance is frequently tested in the universal testing machine using simulated functional loads until fracture occurs. The loading point, force, and direction may all be adjusted, as well as the load at fracture. Micro-computed tomography (CT) analysis of pre- and post-operative pictures allows for assessments of changes in root canal morphology, such as the volume of dentin removed and canal wall regions left unaffected by instruments. Internal structures may be imaged in high-resolution using micro-CT.[9] Endodontically treated teeth require a final restoration that retain esthetics and function, protect residual tooth structure, and prevent microleakage. It is now feasible to produce Cons, highly cosmetic restorations that are attached directly to the tooth structure and reinforce it due to rapid developments in adhesive technology and stronger adhesive materials.[10] To improve the fracture resistance of endodontically treated teeth, modern therapeutic principles promote a minimally prepared approach to endodontic treatment that maintains as much of the tooth structure as feasible while preserving endodontic treatment quality. However, conventional access has been shown to have a larger proportion of irreparable tooth fractures, which have been linked to more coronal tooth structural loss than alternative access methods.[11]

EFFECT OF MODERN ACCESS CAVITY DESIGNS ON OCCURRENCE OF MISHAPS DURING ROOT CANAL PREPARATION

The goal of endodontic therapy is to thoroughly debridement and cleansing root canal from any diseased tissue so that the canal space may be shaped and prepared to be filled with an inert substance, reducing or decreasing the risk of reinfection. When endodontic therapy falls short of conventional clinical standards, accidents occur. Various factors have been shown to be responsible for endodontic treatment failure (mishaps). Failure to adhere to AC preparation guidelines or the instructions for the use of rotary instruments might result in fractured instruments.[12] Furthermore, straight line access (SLA) will minimize the probability of iatrogenic issues such as zips, elbows, and ledges caused by large (and hence inflexible) stainless steel files attempting to straighten in curved canals, as well as make rotational tool insertion simpler during preparation. When utilizing nickel-titanium instrumentation, SLA is required. Although these instruments are quite flexible, inadequate SLA might cause file distortion and ultimately separation owing to cyclic wear.[13] These tools should, under ideal conditions, reach the apical foramen or at least the first curve of the canal without bending. Excessive instrument bending, which results in ineffective control, can cause a slew of issues. Attempts to clean and shape the canal without SLA frequently results in procedural errors such as ledging, transportation, and zipping. A tool that does not bend during operation, on the other hand, allows for a better tactile sensation of canal anatomy and enhances file performance in the root canal system.[12,13,14]

EFFECTS OF MODERN ACCESS CAVITY DESIGNS ON IRRIGATION TECHNIQUES USED DURING CLEANING OF ACCESS CAVITY AND ROOT CANALS

One of the most important phases in endodontic treatment is biomechanical preparation. Because the significance of intracanal bacteria in the formation and progression of peri-radicular and pulpal illnesses is well established, the primary objective of endodontic therapy is to remove all pulp tissue and disinfect the canal. Different irrigation delivery methods, such as sonic and ultrasonic, are available to increase disinfection and debridement action.[15] Endoactivator (Dentsply Maillefer, Ballaigues, Switzerland) is the most tested sonic device, although it only runs at 0.166–0.3 kHz, and most studies indicated that ultrasonic irrigation produced superior effects, perhaps due to the increased power (approximately 40 kHz).[15] Ultrasonic irrigation methods can be classified into two forms: first, the use of ultrasonic irrigation and instrumentation at the same time and the second method, known as passive ultrasonic irrigation, operates without the use of simultaneous instrumentation (Passive Ultrasonic Irrigation (PUI)). Because of the difficulties in managing the dentin cut, the first one has practically been abandoned in clinical practice. The noncutting technique (PUI) decreases the risk of abnormal forms developing in the root canal system. Ultrasonic waves are used to transport energy from a file or fine wire to the irrigant, generating two physical phenomena: stream and cavitation of the irrigant solution. The acoustic stream is characterized as a fast circular or vortex-like flow of fluid around a vibrating file. Cavitation occurs when pre-existing bubbles in a liquid expand, compress, and/or distort.[16] Laser-activated irrigation is a new light activation technology that has shown to be effective. The mechanism of action is based on the fast absorption of laser energy by erbium: yttrium-aluminum-garnet and diode lasers, resulting in microcavitation and subsequent rupture of irrigant bubbles. When utilized for the same length of time, photoactivation techniques with cavitation produce superior outcomes than ultrasonic methods, with more debris removal, a longer lasting and enhanced response rate, and a higher irrigant temperature. Laser expense and the possibility of apical extrusion are two main drawbacks.[17] Microorganisms can be killed by exposing them to high temperatures. When solutions were heated to 20°C and 45°C, there was a 100-fold increase in killing effectiveness. A 20°C irrigant reached 45°C–60°C in 7–20 min, respectively, using a heating machine. There is limited information on the temperature needed to properly heat the interior of the root canal and eliminate germs. Moreover, heated obturation is the only technique that measures heat dispersion from the increased temperature within the root canal to the surrounding tissues.[18]

OBTURATION TECHNIQUES USED WITH MODERN ACCESS CAVITY DESIGNS

After cleaning and shaping, the goal of obturation is to fill and seal the root canal system as effectively as possible. Recently, researches have shown that the quality of obturation has a strong correlation with treatment effectiveness. Adequate obturation of the root canal system, particularly its ramifications, poses a number of obstacles, largely due to the difficulty in adhering material to root canal walls and having the filling material attach to root canal walls. Research came up with the idea of obturating root canals with injection-molded thermoplasticized dental gutta-percha. They discovered that injected thermoplasticized gutta-percha, when combined with sealer, will form a successful apical seal.[2,3,4,5] Before the commercialization of prefabricated alpha-phase gutta-percha or polycaprolactone-based core-carrier systems, it was a common practice to coat metal carriers such as gold wire, silver points, and endodontic files with heat-softened gutta-percha for three-dimensional obturation of the canal space. They enhance gutta-percha adaptability to canal walls and filling material flow into lateral canals by using core-carrier systems. Plastic obturators have to be used in lieu of the original metal carriers due to issues that arose during retreatment and the preparation of post gaps.[8,9,10,11,12,13,14,15,16,17] The Down Pak is a new and revolutionary instrument that enables for three-dimensional obturation using heat and vibration. The Down Pak is a cordless endodontic heating and vibrating spreader equipment that may be used for both warm vertical and lateral condensation methods.

CORONAL RESTORATION OF THE MODERN ACCESS CAVITY DESIGNS

Several factors impact the success of endodontic therapy, and one of the most common reasons of endodontic failure is microbial infection. Coronal ACs allow for root canal system leakage. More important than endodontic treatment quality is how well a tooth is restored on the periradicular side. Endodontically treated teeth should be restored as soon as possible after root canal treatment to prevent coronal leakage. Direct composite resin restoration is an excellent therapeutic option for preserving more tooth structure in teeth with fillings that have been treated with root canal therapy. Direct composite resin restorations are more resistant to tooth breakage than amalgam restorations, and they also offer intracoronal strengthening. Using composite restoration methods and adhesive procedures, researchers have successfully restored cavities having three or more surfaces. Because they were too brittle to be utilized in permanent fillings in the rear teeth, early versions of GIC had weak physicochemical bonds to enamel and dentin. To compare, after 4 years of research, the newly created condensable GIC and an unique nanofilled resin covering (Equia Restorative System; General Composites of America in Alsip, Illinois) outperformed the microfilled hybrid composite in class I and II cavities. However, no published research has demonstrated how well these new restorative materials perform in teeth that have had endodontic treatment; care should be used when utilizing these materials.

CONCLUSIONS

”Cons access,” “ninja access,” and “truss access” are the “contracted” ACs used as an alternative to Trad access. Cons access is a feasible option for root canal treatment since it preserves tooth structure while allowing for a readily and safely procedure. In the ninja access, a tiny hole is made approximately at the center of the occlusal surface. This method does not appear to offer enough room for the subsequent therapy stages to be carried out properly, but there are currently insufficient scientific data to support it. Truss access is designated for multicanaled teeth because it necessitates the preservation of a portion of the chamber roof as well as an enamel–dentin bridge by providing direct access to each canal.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.