EVALUATION OF CELL PACK PAPER POINTS BEFORE AND AFTER STERILIZATION: A MICROBIOLOGICAL STUDY

Abstract

Bacteria are mainly responsible for the development of pulp/periapical diseases. [...]elimination of bacteria during root canal treatment and maintaining aseptic conditions by instrumentation, irrigation and intracanal medication has always been an important part of any successful endodontic treatment. According to the literature, humid heat (that is, an autoclave) is a feasible and effective option for sterilizing paper points, while preserving asepsis conditions without compromising their properties [12]. According to the obtained results, prior to sterilization, the point cells shown some growth of bacterial culture. [...]the study also evaluated the bacterial growth of sterilized paper points after storing for 3, 5, 7 and 14 days after sterilization.

Headnote

Abstract

Introduction. Bacteria are mainly responsible for the development of pulp/periapical diseases. Therefore, elimination of bacteria during root canal treatment and maintaining aseptic conditions by instrumentation, irrigation and intracanal medication has always been an important part of any successful endodontic treatment. The purpose of this study is to determine the bacterial contamination of paper points before and after sterilization and to evaluate the bacterial growth for various storage period after sterilization of paper points. Materials and methods. 50 paper points, collected randomly from the endodontic department, were divided into five groups of 10 samples each. 250 paper points were collected and randomly divided into 5 groups, depending on the period of sterilization, i.e. immediately, 3, 5, 7 and 14 days after sterilization. Each group contains 50 samples, sterilized prior to the inoculation in the sterilized fluid, in Thioglycolate media. After the incubation period, the samples were aerobically cultured onto Mueller-Hinton agar (MHA). The data obtained was evaluated qualitatively, by the presence of turbidity and bacterial growth on the culture media. Results and discussion. prior to the sterilization of the paper points, all samples showed bacterial growth, yet not statistically significant. No bacterial growth of paper points was observed immediately, 3, 5, and 7 days after sterilization. Bacterial growth was seen only in one group, after 14 days of sterilization. Conclusions. To assure a higher safety of endodontic procedures, the absorbent paper points of any commercial type should be autoclaved before clinical use. All paper points were contaminated before sterilization, so that their sterilization is recommended. One week is the maximum time at which the paper points can stay sterilized before use.

Keywords: paper points, bacterial culture, sterilization, endodontic therapy, Mueller-Hinton agar.

1. INTRODUCTION

The main objective of endodontic therapy is to decontaminate the entire root canal system [1]. A successful endodontic treatment depends on the eradication of the microorganisms present inside the root canal system and also on the prevention of re-infection [2]. Therefore, it is essential to create and maintain an aseptic chain throughout the course of the endodontic treatment [3]. Root canal system asepsis is performed in a number of clinical stages, including biomechanical preparation and irrigation with several chemical solutions [4]. One of the most important treatment procedures for optimizing a long-term clinical success of root canal treatment is adaptation of the material along the walls of the root canal system and apical foramen [5]. Root canal sealing has played an important role in dental therapy, as biomechanical preparation by itself is not capable of disinfecting the root canals [6,7]. Based on the modern concept of infection control, all materials and instruments used during endodontic procedures should be bacteria-free [8]. Some endodontic materials (e.g., gutta-percha points and mixing pads) are packaged in a way that renders sterility impossible throughout clinical storage [9]. An adequate obturation of the root canal system cannot be reached if the canal is wet, so that root canal drying is an important step for a marginal sealing success of the endodontic obturation, because the physicalchemical properties of the filling material adhesion are altered by moisture [10,11]. Standardized absorbent paper points are widely used in endodontic therapy to dry root canals after irrigation [12]. As these are the last materials inserted into the root canal, absorbent paper points must be free of microorganisms, to prevent a possible break in the aseptic chain and subsequent treatment failure [13]. Although these paper points are manufactured under aseptic conditions and present some antibacterial action, they can be contaminated by physical sources during storage, handling, or by aerosols after opening, which is why many professionals should depend on re-sterilization of the points [14]. An in vitro microbiological study was conducted to determine the bacterial contamination of paper points before and after sterilization, and to evaluate the bacterial growth for various storage periods after their sterilization.

2. MATERIALS AND METHODS

The research was developed along two stages; before sterilization (50 samples) and after sterilization (250 samples), with specific time period packing (immediately and after 3, 5, 7 and 14 days). For adequate sample standardization, all absorbent paper points used in the study came from the same manufacturer lot.

Before sterilization

50 paper points collected from the endodontic department were submitted to a microbial study in the microbiology department. The samples were inoculated into sterilized fluid Thioglycolate media (Fig.1) and incubated at 37°C / 24 hrs. Prior to sterilization, the samples were randomly divided into 5 groups of 10 samples each, as follows;

Group 1: cell packed

Group 2: sterilized not opened not expired

Group 3: sterilized not open expired

Group 4: opened not expired

Group 5: opened expired.

Each group of 10 samples was inoculated and, after 24 hrs of incubation, the tubes were examined for microbial growth; in terms of turbidity, all tubes seemed clear. Subcultures were done for each group into Mueller-Hinton agar (MHA) and incubated aerobically at 37°C / 48 hrs. After a 48 hr incubation period, the culture plates were examined for possible microbial growth.

After sterilization

250 paper points were collected and randomly divided into 5 groups. Each group contains 50 samples and was sterilized by autoclaving 121°C / 15 min. and submitted to microbiology laboratory to microbial study.

Group 1: Inoculated immediately after sterilization

Group 2: Inoculated 3 days after sterilization

Group 3: Inoculated 5 days after sterilization

Group 4: Inoculated 7 days after sterilization

Group 5: Inoculated 14 days after sterilization

All samples were inoculated onto sterilized fluid thioglycolate media and incubated at 37°C/12Hrs. After incubation onto Mueller- Hinton agar (MHA) (Fig.2) and keeping for 48 hrs of incubation at 37°C aerobically, the culture plates were examined for possible microbial growth.The study was approved by the ethical committee of the College of Dentistry, King Khalid University, Abha. Data was evaluated qualitatively by the presence of turbidity and bacterial growth on culture media. Statistically significant differences among the groups were set at P < 0.05.

3. RESULTS AND DISCUSSION

Prior to the sterilization of paper points, all samples show bacterial growth, yet statistically not significant (Table 1).

No bacterial growth of the paper points were observed immediately or 3, 5, and 7 days after sterilization. Bacterial growth was seen only in one group 14 days after sterilization (Table 2).

As known, the oral cavity environment is colonized by a large and diverse number of microorganisms [15]. All provisions regarding biosecurity must be strictly followed during all clinical procedures in order to maintain an aseptic chain, thus preventing adverse consequences, such as direct infections and treatment failure. In cases of root canal therapy, the aseptic chain may be broken if bacterial contamination due to gutta-percha and absorbent paper points occurs inside the endodontic cavity. The paper points, the ultimate materials to penetrate inside the root canal before obturation, must be free from contamination at the time of their use [16].

During the endodontic procedure, it is mandatory to keep the environment clean, using aseptic materials, and to make all efforts for removing the undesirable microorganisms [17]. The endodontic therapy is associated with infection control, while maintenance of the aseptic chain is crucial to provide a better prognosis [18]. Commercial absorbent paper points can be obtained from the manufacturer in sterile packages or not. The materials not sterilized by the manufacturer can be subjected to contamination, which can influence the prognosis of the treatment. Thus, the use of sterilized paper points is essential during the therapy. Although the literature presents many studies evaluating the absorbing capacity of paper points [10-12,19], few researches on microbiological evaluation are available.

Sterilization methods, such as dry heat (oven) humid heat (autoclave) and paraformaldehyde tablets, are used to sterilize absorbent paper points after they are taken out of the package [13]. The sterilization process should not compromise the initial physical, chemical and biological properties of the paper points, particularly their absorption capacity, which is one of their most important characteristics [12]. According to the literature, humid heat (that is, an autoclave) is a feasible and effective option for sterilizing paper points, while preserving asepsis conditions without compromising their properties [12].

Absorbing paper points are commonly marketed in plastic boxes containing about 120 units in standard sizes, separated by a plastic division, a commercial presentation which does not ensure the sterility for the product. More recently, manufacturers provided paper points packed in up to 5 units, assuring their sterility. However, several studies which tested the sterility of these cones evidenced materials' contamination, as proved through bacterial growth [13,14,20,21].

The present study initially evaluated whether the cell-packed paper points with open box and expiry combinations were sterile or not. According to the obtained results, prior to sterilization, the point cells shown some growth of bacterial culture. In this respect, all paper points provided by manufacturers should be necessarily sterilized before clinical use. Almeida et al. [10] observed contamination in EndoPoints brand. They also reported that these cells were easily violated during handling, so that the EndoPoints manufacturers could not report the effectiveness of sterilization.

Finally, the study also evaluated the bacterial growth of sterilized paper points after storing for 3, 5, 7 and 14 days after sterilization. No bacterial growth was seen in all samples of paper points stored for a period of up to 1 week. However, 26% of the samples of sterile paper points showed bacterial growth when stored for 14 days. Some studies emphasized the need to sterilize even pre-sterilized commercial points [10,19,22]. The results agreed with those of previous studies, which showed that the sterile points were contaminated [9,19]. The culture media utilized are those recommended in the literature, as well as the methods employed in previous bacteriological studies [10,19,23]. In the present investigation, sterilization of absorbent paper points was done in a single sterilization cycle as, according to Victorino et al. [24] and Kubo et al. [14], the absorption capacity of paper points is influenced by the number of sterilization cycles.

The present study demonstrated that absorbent paper points have a certain level of microbiological contamination, regardless of their origin (i.e., whether they are taken from sealed or open commercial packaging) and operator manipulation. Absorbent paper points from sealed packages showed levels of contamination similar to the papers points 14 days after sterilization. In other words, the risk of contamination was present whether or not the package was sealed. Paper points are not like gutta-percha and Resilon points, as the latter can be disinfected by using substances such as sodium hypochlorite and chlorhexidine [25]. Thus, care with sterilized paper points is crucial for avoiding the contamination of the root canal. The use of a sterilized millimeter ruler is essential at the moment of calibration and measurement of the paper point, so that the root canal should not be contaminated.

4. CONCLUSIONS

Based on the findings of the present study, we conclude that, to assure higher safety in endodontic procedures, the absorbent paper points of any commercial type should be autoclaved before clinical use. All paper points appeared as contaminated before sterilization, so that their sterilization is highly recommended. One week is the maximum time that paper points can stay sterilized before use. This finding demonstrates the importance of the sterilization process prior to using absorbent paper points, and the need for their proper handling, to prevent a break in the aseptic chain during clinical practice.

References

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