Oxygen as obturation biomaterial in endodontic treatment: development of novel membranous dental restoration system

Introduction

Some variants of concern of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or coronavirus disease 2019 (COVID-19) have been recorded.¹ Dentists are particularly susceptible to COVID-19 infection due to their proximity to a patient’s mouth during treatment. Saliva can harbour various viruses, including coronaviruses,² and is an element that dentists cannot entirely avoid when performing any procedure in the oral cavity. Therefore, both dentists and patients must exercise caution when providing or receiving dental care.

Various measures have been implemented to address the spread of COVID-19 in dental practice, ranging from the closure of dental clinics to the restriction of certain types of treatments that can only be performed under stringent protocols.³ The rationale behind all these decisions is to minimize or reduce interactions with patients who may potentially transmit the coronavirus. Conversely, patients are making efforts to avoid visiting locations they perceive as potentially contaminated with the virus, such as hospitals and dental clinics. Thus far, the COVID-19 pandemic has significantly influenced the manner in which dentists operate.

Endodontic treatment typically necessitates multiple visits, which can pose a disadvantage for patients. Nevertheless, root canal therapy may still be essential for individuals experiencing severe dental pain, as most emergency cases in dentistry require endodontic intervention.⁴ In a study conducted in India during the COVID-19 pandemic, three primary reasons for emergency visits to dental clinics were identified: pulpal problems at 46.0%, abscesses at 16.6%, and periapical lesions at 15%. All of these issues were indeed related to endodontic concerns.⁵

The pandemic has motivated dentists to enhance their efficiency, particularly in resolving patient cases quickly. This drive can persist beyond the pandemic, as streamlining treatment remains advantageous for patients. This article aims to explore a new potential concept, previously undiscussed in any scientific journals, to reduce the time required for endodontic treatment.

Current endodontic treatment

There are ten principles to consider in endodontic treatment. The first and second principles are aseptic technique and the restriction of instruments to the root canal. Third, root canal preparation should be conducted using appropriate instruments. Fourth, the root canal should be expanded, if feasible, to facilitate cleaning. Fifth, the root canal must be thoroughly irrigated with antiseptic solutions. Sixth, any irrigating solutions used must be safe for periapical tissues. Seventh, if a sinus tract is present, it should be addressed following root canal therapy and does not necessitate surgery. An incision in the soft tissue may be performed for an acute periapical abscess to allow for drainage. Eighth, the root canal should be hermetically obturated to ensure a proper seal. Ninth, prior to obturation, a negative culture should be obtained. Tenth, all materials used in obturation must be biocompatible. These principles are based on the conclusions drawn at the International Conference on Endodontics in 1958.^6–8

Successful root canal therapy depends on three key factors: cleaning and shaping, disinfection, and obturation.⁹ Periradicular pathosis is primarily caused by the growth of pathogens in the root canal system, and unsuccessful treatment is not directly linked to errors in the procedure itself.¹⁰

Trepanation: bringing back oxygen circulation to a nonvital tooth

There remains a question regarding the adequacy of single-visit root canal treatment in eliminating root canal bacteria that may lead to future reinfection.²⁰ However, multiple-visit root canal treatment is generally not preferred by patients. Bacteria that are challenging to eliminate from the root canal, particularly within dentinal tubules, can survive in an anaerobic environment. The failure of root canal treatment typically involves the proliferation of anaerobes and facultative anaerobes that become pathogenic and more adept at causing infection in the absence of oxygen.^21–24

Some strategies to avoid reinfection after root canal treatment include preventing coronal microleakage that may result from inadequate temporary or permanent fillings, as well as eliminating bacteria residing in dentinal tubules. Therefore, in addition to ensuring that no saliva, fluids, microorganisms, or debris can enter through coronal microleakage, dentists must also consider the antimicrobial agent utilized and its delivery system. Disinfection must effectively reach the dentinal tubules where certain bacteria can live and survive anaerobically.²² Dental pain can occur in nonvital teeth, including following root canal treatment, and is often indicative of an abscess. Most treatments for dental abscesses utilizing antibiotics focus on targeting anaerobic bacteria and facultative anaerobes.²⁵ Endodontic infections are polymicrobial, with obligate anaerobic bacteria undeniably dominating the microorganism in primary infections.²⁶ NaOCl is mentioned by numerous researches to be effective against polymicrobial root canal biofilms.^27,28 Virgin coconut oil is also believed to have antiprotozoal, antiviral, and antibacterial properties,^29,30 but to use it as an irrigating solution still needs further studies. Understanding on how oxygen can make a difference in the root canal (please see Table 1) is also an attempt to harness its use in preventing endodontic infection that is dominated by obligate anaerobes.

Because the infection of the root canal in nonvital teeth tends to occur in anaerobic conditions, dentists may consider preventing the root canal microenvironment from becoming oxygen-free. At times, creating ventilation to avoid the absence of oxygen may resemble trepanation. The size of the oxygen molecule is smaller than the diameter of dentinal tubules, allowing it to fill the entire space within the tooth. Oxygen can inhibit the growth of anaerobes and prevent facultative anaerobes from becoming more infectious. Utilizing oxygen as an antimicrobial agent to fill the root canal is expected to reduce the working time for dentists performing root canal treatments. It can serve as a replacement for conventional obturation following proper cleaning and shaping.

Oxygen can penetrate the anaerobic microenvironment within the dentinal tubules at the apical third, where irrigating solutions are unable to effectively flush. This presence of oxygen disrupts the existence of anaerobic organisms. However, facultative anaerobes may still be present in the dentinal tubules and cannot be eradicated by oxygen. Enterococcus faecalis is the most frequently discussed facultative anaerobe in endodontic infections and has the ability to colonize dentinal tubules to a depth exceeding 1000 μm.³⁵ Not always pathogenic, Enterococcus faecalis can also be beneficial and may be regarded as a potential probiotic, as demonstrated in a study of E. faecalis in human milk.³⁶ Given the challenge of completely eradicating E. faecalis, even with recommended irrigants and techniques, an alternative strategy can be to enhance its probiotic potential (mutualism) or ensure it remains nonpathogenic and nondestructive (commensalism). Oxygen might help limit its invasion efficiency and pathogenicity when cleaning and shaping fail to eliminate E. faecalis from the root canal. Apart from its commensal attributes, Enterococcus spp. is also a promising probiotic candidate due to its antibacterial, antifungal, and antiviral properties, largely due to its ability to produce bacteriocins.³⁷

Trepanation was originally defined as the act of perforating the skull. It may be the oldest surgical procedure, practiced by numerous civilizations throughout history, from Greece to China, and has been utilized in Western medicine.³⁸ In modern medicine, surgeons continue to employ this method through minimally invasive trepanation and drainage. It is also regarded as highly effective for treating purulent meningitis,³⁹ and its application in dentistry is no exception. Dental trepanation is a straightforward procedure involving the perforation of the pulp chamber while keeping it open without the introduction of any medicament into the pulp. Academic literature discussing this procedure is scarce, but this should not lead to the misconception that it has never existed. The purpose of dental trepanation in a nonvital tooth extends beyond merely allowing the drainage of pus from dental or periapical abscesses; it also serves to prevent the formation of abscesses. The introduction of oxygen into the tooth can help eradicate the bacteria responsible for abscess development. A case report involving a 12-year-old child in Indonesia indicated that a dental abscess on a permanent maxillary lateral incisor showed improvement following the administration of antibiotics and trepanation, which involved creating a hole that penetrated the pulp chamber. The patient did not return as instructed on the third to seventh day. However, after 45 days, the overall condition of the tooth was satisfactory, and there were no complaints. Furthermore, there were no signs of dental abscess, despite the completion of antibiotic treatment a considerable time prior and the absence of any medicament placed within the pulp chamber.⁴⁰ A dental abscess can occur when a tooth becomes nonvital, lacking blood circulation for oxygen supply. In such instances, dental trepanation can be seen as a method to bring back oxygen circulation to a nonvital tooth.

A study that measured the oxygen saturation level of dental pulp found that the oxygen saturation level decreases when the pulp is in an unfavourable condition. Healthy teeth exhibited the highest oxygen saturation level at 94.6%, while reversible pulpitis, irreversible pulpitis, and pulpal necrosis recorded levels of 85.4%, 81.6%, and 70.7%, respectively.⁴¹ There is some uncertainty about the measurement of pulpal necrosis concerning whether it involved necrotic teeth with or without pulp exposure (e.g., nonvital teeth due to trauma). Nonetheless, it can be concluded that more severe pulp pathology correlates with lower oxygen saturation levels.

Another interesting topic of discussion is the comparison between secondary caries and inactive caries. Secondary caries are caused by cariogenic bacteria in saliva that enter through microcracks (at least 50 μm wide) between fillings and dental tissue, proliferating in a conducive environment.⁴² On contrast, inactive caries can remain unchanged for 4 to 5 years in 85-90% of cases and typically do not require treatment, including restoration.⁴³ Inactive caries allow saliva to reach the tooth surface without obstruction, as there is no filling or covering, though bacteria do not easily progress. When saliva interacts with both types, inactive caries is more accessible and easier to clean, helping prevent debris adhesion, which can ultimately also benefit oxygen circulation. The stability of inactive caries suggests that oxygen circulation may aid in preventing infection in a previously cleansed root canal, free of obstructions and contaminants.

Methods: novel membranous dental restoration system

Dental trepanation has been recognized by some, if not many, dental practitioners in Indonesia. It is also believed that this method has persisted until recent times. If this conventional technique of dental trepanation—performed without the subsequent application of any modern root canal preparation techniques—was once deemed beneficial for nonvital teeth, we hypothesize that a thoroughly cleaned, disinfected, and completely dried root canal, sealed with a specific restoration utilizing an oxygen-permeable membrane, will yield superior results. The membrane will allow oxygen to enter while preventing fluids, debris, and microorganisms from accessing the root canal. The oxygen that continuously circulates throughout the entire root canal system and dentinal tubules will function as an antimicrobial agent that is perpetually renewed to inhibit the growth of pathogens within the tooth.

The novel membranous restoration system described below (please see Figures 1 – 4) is expected to decrease the working time in endodontic treatment, as it can replace the time-consuming conventional obturation techniques. Any conventional sealer for obturation, including those that incorporate nanoparticles, and any established technique, cannot achieve a perfect seal within the root canal system. Naturally, oxygen can flow freely and occupy any space it can infiltrate. Utilizing oxygen as an obturation biomaterial is anticipated to be easier and more time-efficient than all current obturation techniques that employ solid substances. Prior to implementing this restoration design, appropriate root canal preparation, including debridement and disinfection, must be conducted first.

Figure 1. (This figure is an original figure produced by the authors for this article). The aseptic technique should always be applied during the whole restoration process.

Access to the root canal should be securely sealed to prevent debris and fluids from entering the clean and dry root canal. A small piece of rubber, such as that taken from a rubber dam sheet, can be utilized to close the access to the root canal. Once the access is sealed, tooth preparation may proceed.

Figure 2. (This figure is an original figure produced by the authors for this article). Open the blockage created in the root canal after completing any necessary procedures for composite filling, then insert a sterile smooth surface miller needle (smooth broach) into the root canal.

The depth does not need to match the working length.

Figure 3. (This figure is an original figure produced by the authors for this article). A sufficient amount of composite material is applied, while ensuring that the smooth broach can still create a duct that connects the root canal system to the external air beyond the restoration.

Figure 4. (This figure is an original figure produced by the authors for this article). The smooth broach is gently extracted by twisting it, and the appropriate location for placing the membrane in the restoration is directly at the orifice of the duct.

Conclusion

Due to the intricate nature of the root canal system and the minuscule size of dentinal tubules, it is exceedingly challenging, if not impossible, to entirely disinfect and obturate them using any recommended and established techniques. Endodontic treatment appears to necessitate considerable time and multiple visits to address this issue. A new approach is required to reduce the working time and to resolve some unresolved challenges in endodontic treatment. The anticipated outcomes of developing this innovative membranous dental restoration system in the future aim not only to address microorganisms in a nonvital tooth, including Enterococcus faecalis, but also to discover an alternative method for completely filling the root canal system. Disinfecting the resilient E. faecalis and executing complex obturation techniques can be exhausting and time-intensive. It is hoped that oxygen will serve as the agent to inhibit E. faecalis from becoming pathogenic and facilitate the filling of the root canal system with ease.

In this article, we would like to introduce a somewhat novel idea to the field of dentistry: a dental restoration system that utilizes a membrane to provide oxygen to the root canal system. By publishing this concept and making it accessible to the research community, we hope that any ensuing discussions may facilitate the exploration of oxygen-permeable membranes for dental restoration. The role of the oxygen-permeable membrane in the restoration design is analogous to that of a medical mask used during the COVID-19 pandemic, as it allows for the circulation of oxygen while preventing the passage of fluids, debris, and microorganisms. Further research is necessary to identify the most suitable membrane for dental restoration that maximizes oxygen circulation and to evaluate the effectiveness of this method in preventing infection. We are also open to collaborating with other researchers to implement the concept described in this article.