Evaluation of Efficiency of Different Decontamination Methods of Dental Burs: An In vivo Study.

INTRODUCTION: Infection control is very important in dentistry. Both dentist and patients are at risk of communicating diseases during treatment procedures. Dental burs have been identified as a source of cross-contamination between patient and dental personnel. AIM: The present study was done to quantitatively and qualitatively assess the pathogenic contamination of dental burs used for tooth preparation and to determine the effective method of sterilization(autoclave, glass bead sterilizer, hot air oven and surgical spirit immersion) of burs used for crown preparation.
METHODOLOGY: Dental burs were assessed before and after tooth preparation, also after sterilization burs were evaluated.
CONCLUSION: Findings of our study revealed that among the experimental groups used in the present study, Autoclave and Hot air oven was found to be the relatively best method to sterilize burs. Proper cleaning and sterilization of burs should be strictly employed to prevent cross contamination in clinical practice.

INTRODUCTION

Infection control is very important in dentistry because of concern over communicable diseases transmitted during the various invasive and noninvasive dental procedures. Both dentist and patients are at risk of communicating diseases during treatment procedures. In daily practice of dentistry, we use same instruments on many patients which pose the potential risk of disease transmission if proper sterilization is not done.[1] Instruments must be cleaned, disinfected, and sterilized to prevent any contamination. Precleaning and sterilization of some devices can be difficult because of their small size and complex architecture. Dental burs are such instruments. Dental burs come in a variety of shapes and sizes, all with highly complex and detailed surface features. Dental burs have been identified as a source of cross-contamination between patient and dental personnel. They are contaminated with necrotic tissues, saliva, blood, and potential pathogens during use. However, it is difficult to do the precleaning and sterilization of burs because of their complex architecture.[12]

A strict sterilization protocol is essential as the risk of cross-infection is higher in prosthodontics next to maxillofacial surgery. Sterilization can be defined as the process of destruction or removal of all microorganisms from article, surface, or medium, including spores. However, to achieve sterilization of any instrument, three definite stages are to be complete; first is the presterilization–cleaning, next is the sterilization process, and at last the aseptic storage.[23]

Aims and Objectives

The present study was done to quantitatively and qualitatively assess the pathogenic contamination of dental burs used for tooth preparation and to determine the effective method of sterilization of burs used for crown preparation. The objective was to prevent cross-contamination and to achieve effective sterilization by subjecting the used (infected) burs to different sterilization methods and microbiological culture.

MATERIALS

The materials used were Airotor handpiece, transporting medium (phosphate-buffered saline) [Figure 1], culture medium (nutrient agar and blood agar), autoclave, hot air oven, glass bead sterilizer, Surgical Spirit, 5 groups of diamond burs [Figure 2] (blue color coded and Flat End Tapered diamond burs standard grit size - 125 microns) (one group contains 16 samples) totally eighty burs.

Figure 1

Collected samples in test tube

Figure 2

Flat end tapered diamond burs

This is an in vivo study, in which used burs were considered for sterilization. Ethical clearance was obtained from J. K. K. Nattaraja Dental College and Hospital committee. Procedure and purpose of the study were explained to the participants for whom burs were used, and their consent was taken.

The inclusion criteria were patients with missing teeth and treatment plan was fixed partial denture, in them teeth with no caries, not a periodontally affected teeth, vital teeth, and patient with no systemic diseases were selected.

The exclusion criteria were nonvital teeth, carious teeth, and periodontally affected teeth were not included for crown preparation.

Methodology

Eighty burs specified as earlier were taken. These burs were assigned into five Groups (A, B, C, D, and E) of 16 each. They were cultured in nutrient agar and blood agar medium immediately after removal from the pack and the results were obtained. Group A burs serve as control sample. On culturing, the Group A burs contained Staphylococcus epidermidis, Bacillus subtilis, and Fungi; Group B contained B. subtilis, S. epidermidis, Enterococcus species, and Fungi; Group C contained S. epidermidis, Serratia species, and B. Subtilis; Group D contained B. subtilis, Serratia species, Fungi, and S. Epidermidis; and Group E contained S. epidermidis, Enterococcus species, and B. subtilis.

On culturing, the new unused burs Staphylococcus species (Gram-positive cocci) were present more predominantly; this result was used as a control for the reference of further samples.

Group B, C, D, and E burs were used for crown preparation. Crown preparation was accomplished with high-speed hand piece with continuous water spray and the preparation was limited to 3 min for each bur. After which, the burs were removed from air rotor hand piece with a sterile Tweezer, and with the help of transporting medium, they were carried to the laboratory and cultured within 2 h of crown preparation.

On culturing the bur after using on patients, in GROUP B, Bacillus species, S. epidermidis, Enterococcus species, and Streptococcus species were seen; in Group C Enterococcus faecalis, Actinomycetes, Lactobacillus species, Candida species, and Streptococcus species were seen; in Group D, B. subtilis, Serratia species, Fungi, Streptococcus mutans, and S. epidermidis were seen; in Group E, Streptococcus mutans, Micrococcus, Aeromonas species, and Staphylococcus saprophyticus were seen.

Among all the burs, Streptococcus species (Gram-positive cocci) were seen more predominantly than other species.

After that in each group, all the samples were sterilized by the following different methods.[4]

Group B burs were autoclaved [Figure 3]. Steam is the effective means of sterilization because of its high penetrating capacity; it gives large amount of heat to surface with which it comes in contact. Sixteen contaminated burs were autoclaved for 16 min at 120°C under 16 psi. Sterilization monitoring of autoclave was done with color changeable chemical tape.[5]

Figure 3

Hot air oven, glass bead sterilizer

Group C burs were sterilized using hot air oven. Sterilization control of hot air oven was done using Browne's test strip available that contain a chemical indicator. The spores of nontoxigenic strain of B. subtilis and Clostridium tetani are used as a microbiological test of dry heat. Sixteen contaminated burs were placed in hot air oven for 60 min at 170°C. After complete sterilization, burs were recovered and sent for microbiological culture.

Group D burs were sterilized using glass bead sterilizer.[6] The media used are glass beads, molten metal, and salt [Figure 4]. Sixteen contaminated burs were submerged in a glass bead sterilizer at a distance of 2 mm from the wall of the sterilizer for 5 s at 230°C with a sterile tweezers. The glass bead sterilizer was controlled by thermostat and the light indicated the attainment of the required temperature.[7] After sterilization, burs were sent for culture.

Figure 4

Glass bead sterilizer

Group E burs were sterilized using alcohols which acts by denaturing bacterial proteins [Figure 5]. A solution of 70% ethanol is more effective than higher concentrations, as the presence of water, speeds up the process of protein denaturation as reported by Lawrence and Block (1968). Sixteen contaminated burs were immersed in Surgical Spirit (this preparation contains denatured ethyl alcohol 96% with 1% methanol, 2% v/v diethyl phthalate intraperitoneal (I.P), and 0.5% v/v of methyl salicylate I. P) for 15 min and sent for culture.

Figure 5

Surgical spirit

After decontamination by following methods, collected test samples were carried for the microbiological processing to obtain the specific culture.[89]

On culturing the bur after sterilization by glass bead sterilizer and Surgical Spirit, Streptococcus species (Gram-positive cocci) were seen more predominantly than other species.

Statistical analysis

Results were expressed as mean ± standard deviation, range values, and a number of percentage.

Kruskal–Wallis ANOVA and Wilcoxon's Rank Sum test (Mann–Whitney test) were done for multiple group comparisons and reduction in CFU/ml.

RESULTS

In the group of burs that were autoclaved Streptococcus species which were 4 x 106 CFU Were reduced to nil in number. In the group of burs that were sterilized using hot air oven Streptococcus species which were 4 x 106 CFU Were reduced to nil in number. In the group of bburs which were sterilized using Glass bead sterilizer Streptococcus species which were 1.5 × 102 CFU were reduced to 1 x 107 CFU. In the group of burs that were sterilized using surgical spirit Streptococcus species were reduced from 2.7 x 107 CFU to 1.9 x 104 CFU.

Among the other organisms, Streptococcus species were found to be significantly (P < 0.001) occurring in tooth preparation burs, after tooth preparation and sterilization.

On intergroup comparison of reduction of microorganisms, maximum reduction of microorganisms was seen (P < 0.001) in autoclave (Group B) and hot air oven (Group C), followed by glass bead sterilizer and Surgical Spirit (Group D and E).

DISCUSSION

In the current scenario where there is a tremendous development in the field of dentistry, the need for replacement of tooth through fixed partial denture has gained importance. The increase in the number of patients seeking treatment leads the dentists to reuse certain instruments. In this state, the concern over cross contamination has to be considered. There have also been concerns over the possible transmission of microorganisms by contaminated surgical instruments.[10]

Dental burs, the most widely used instrument in dentistry, have the greater potential to transit disease since they contact with saliva blood and teeth.[1112] While most of the dental instruments are effectively cleaned after use, the diamond bur is often neglected and only brushed or immersed in a mild disinfectant before reuse.[13] Hence, there is a need to research on the importance of sterilization of burs. The goal of instrument sterilization in dentistry is to protect patients from cross-contamination through instruments.[14]

The predominant methods of sterilization include autoclave, hot air oven, and glass bead sterilizer, and the most widely used method in clinical practice is the disinfection of burs using surgical spirit. Another method of sterilization, namely, laser, is also available but not widely used.

Dry heat sterilization is slower and requires temperatures higher than those used in moist heat sterilization. This study showed that sterilization by a glass bead sterilizer was not able to completely eliminate microorganisms and that total sterility was not found.[15]

However, in this study, the autoclave was proved to be an effective method of sterilization of burs with regard to the destruction of microorganisms and spores; in other way, this method of sterilization under heat with pressure also reduces the cutting efficiency of burs by reducing the grit size of the diamond particles. Hence, the number of cycles of sterilization should be limited to maintain the cutting efficiency of burs in clinical practice.[5]

CONCLUSION

Findings of our study revealed that, among the experimental groups used in the present study, autoclave and hot air oven were found to be the relatively best method to sterilize burs. Proper cleaning and sterilization of burs should be strictly employed to prevent cross-contamination in clinical practice.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.