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Year : 2005  |  Volume : 8  |  Issue : 3  |  Page : 23-31
Effect of disinfectants and glass bead size on efficacy of glass bead sterlizer

1 Department of Conservative Dentistry, Balaji Dental College and Hospital, India
2 Department of Conservative Dentistry and Endodontics, SRM Dental College, India

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How to cite this article:
Subbiah, Subba Rao C V, Balaji R G. Effect of disinfectants and glass bead size on efficacy of glass bead sterlizer. J Conserv Dent 2005;8:23-31

How to cite this URL:
Subbiah, Subba Rao C V, Balaji R G. Effect of disinfectants and glass bead size on efficacy of glass bead sterlizer. J Conserv Dent [serial online] 2005 [cited 2023 Dec 8];8:23-31. Available from:

   Introduction Top

In recent years, infection control has come to the forefront since it has been claimed that Acquired Immune Deficiency Syndrome (AIDS) and Hepatitis B (HBV) are transmitted from health care professionals to their patients and vice versa.

It has been reported that among the organisms isolated from infected root canals, Streptococcus viridans and Staphylococcus aureus Scientific Name Search  which form the commensal flora of the mouth and throat, are considered as potential pathogens in the causation of sub acute bacterial endocarditis and pyogenic lesions [22] . Hence proper cleaning and shaping of the root canal is essential for reducing the bacterial population in the root canal system.

Different sterilization techniques for intracanal instruments have been advocated such as dry heat sterilizer, steam autoclave, Harvey vapor sterilizer, ethylene oxide gas sterilization, glass bead sterilizer and hot salt sterilizer. Although primary sterilization can be achieved by glass bead or hot salt sterilizer [2],[9],[11] The Council on Dental Therapeutics, Council on Dental Practice recommend the use of glass bead sterilizer for sterilization of intracanal instruments for a period of 10 to 15 seconds at a temperature of 425-475 o F as it provides rapid sterilization [3]

Prior to sterilization, complete cleansing of the instruments is necessary since cleaning reduces the number of microbes that must be cleaned and also removes blood, saliva or other material that may insulate the remaining microbes from direct contact with the killing agents. Precleaning is an integral part of surface disinfection to reduce the bioburden , which helps to assure success of the overall procedure [16] . The two common methods that have been advocated for instruments cleaning prior to sterilization are hand scrubbing and ultrasonic cleaning . The council of Dental Therapeutics recognized liquid preparation of formaldehyde and glutaraldehyde as high level disinfectants or sterilizing agents [6]

This study has been undertaken to evaluate the efficiency of sterilization of glass bead sterilizer and the effect of cleansing endodontic instruments with various disinfectants prior to sterilization

   Materials and Methods Top

The primary sterilization of files used in this study was done with hot air oven at 160"C for 90 minutes. Files were dipped into the media containing test organisms. Subsequently they were cleaned with gauze soaked in three different disinfectants. The microbiological aspect of the study was conducted at the post-graduate Institute of Basic Medical Sciences. Taramani, Chennai.

The study was divided into two experimental groups.


The sterile metal handle No.60H files which were sterilized in hot air oven were allowed to cool down to room temperature. The glass bead sterilizer was allowed to reach the sterilizing temperature and the temperature was monitored between 232­-237 o C (450-460 o F) through out the study.

The test organisms used were Streptococcus fecalis, Staphylococcus aureus and Bacillus subtilis Scientific Name Search  which were obtained from a stock culture and was subcultured in nutrient broth for 24 hours at 37° C.

A total number of 420 files were used in this study. The experiment was divided into three groups of 140 files each. The groups were

Group-I Files (140 Nos.) dipped in media containing Streptococcus fecalis

Group-II Files (140 Nos.) dipped in media containing Staphylococcus aureus.

Group-III Files (140 Nos.) dipped in media containing Bacillus subtilis and dried for 24 hours at 37 o C.

The contaminated files were then divided into 4 sub groups of 35 files each. The files in the sub­groups were treated as follows

Sub Group A Wiped with gauze saturated in 5.25%h sodium hypochlorite.

Sub Group B Wiped with gauze saturated in 95% Isopropyl alcohol.

Sub Group C Wiped with gauze saturated in 2% Glutaraldehyde.

Sub Group D Wiped with gauze saturated in Normal saline.

After wiping the files, with disinfectants and saline the files in the subgroups were divided into 7 lesser sub-groups of 5 files each. The files in each sub­group were immersed into the glass beads sterilizer containing glass beads of size 1-1.5mm. The files were inserted along the periphery so as to utilize the maximum temperature of the sterilizer. They were immersed into the glass bead sterilizer completely so that no portion of the file is left without being exposed to sterilization procedure. Files were immersed for varying periods of time (i.e.) 3, 5, 10, 15, 20, 25 and 30 seconds.

The files were removed from the glass bead sterilizer and dropped into the test tube containing nutrient broth for primary inoculation and incubated at 37° C for hours. After 24 hours the test tubes were observed for the presence or absence of turbidity.

Subsequently, all the specimens were subcultured in Nutrient agar, incubated at 37 0 C for 24 hours. After 24 hours the nutrient agar plates were examined for presence or absence of colonies.

Five samples of contaminated files without wiping were cultured for negative control and five samples of sterile files removed form Hot air oven were cultured for positive control by following the same culturing procedure and the results were tabulated.[Table 1],[Table 2],[Table 3],[Table 4]

Experiment I

Experiment II

To compare the effect of size of glass bead on the efficiency of sterilization of the glass bead sterilizer two different size of glass bead were used (larger glass bead-2-3mm; smaller glass bead 1-­1.5mm). In this part of the study, after primary sterilization the files were contaminated with the test organisms. Without wiping with disinfectant, the files were immersed in the glass bead sterilizer with larger glass beads for 3, 5, 10, 15, 20, 25,30 and 35 seconds. After immersion into the glass bead sterilizer the files were then dropped into the nutrient broth and incubated at 37 0 C for 24 hours. The test tubes were observed for turbidity. These cultures were then subcultured on to the nutrient agar and incubated at 37 o C for 24 hours. This procedure was repeated with the smaller size glass beads (1-1.5mm) and the results were tabulated.[Table 5],[Table 6]

   Results Top

This study was divided into two experimental groups and the results are tabulated.

   Discussion Top

Microorganisms are the major cause of endodontic disease hence adequate debridement of the root canal and the use of strict aseptic procedures are mandatory [15] . Custer and Anderson stated that sterilization by autoclave causes instrument corrosion [4] . While Neal have reported that apart from corrosion, autoclaving can adversely affect the cutting ability of the files whereas dry heat and glass bead sterilization had no adverse effect on the cutting efficiency of files [17] .

Grossman suggested the use of a glass bead sterilizer because of the rapid sterilization effect on endodontic instruments such as reamers & files [10] . The Council of Dental Therapeutics also recommends the use of glass bead sterilizer, preheated to atleast 425 0 F for a period of 10 seconds. [3]

Glass bead sterilizer works on the principle of intense dry heat [23],[14] . It has been confirmed that intense dry heat damages vegetative and spore forms of bacteria [11] . Cleaning of instruments and equipment surfaces is one of the most important aspects of infection control. It has been emphasized by the American dental Association that the "Patients debris and body fluids must be removed from the instruments and surfaces before sterilization or disinfection" [16] .

Hubbard et al and , Hurt and Rossman have suggested that removel of debris and disinfection of files are essential before sterilization [12],[13] . In our investigations the guidelines of the above workers were followed by manual cleaning of the files with disinfectants prior to sterilization.

Sisco et al emphasized that glass bead sterilizer is the most efficient mode of chairside sterilization in terms of time and convenience [21] . In this study No.60 metal handled H-file were used in confirmation with ANSUADA specification for sterilization. In the present investigation Dry heat sterilizer sterilized all endodontic instruments before contaminating the files with known test organisms.

Most of the investigators have used Bacillus as the test orgainisms [7],[8],[18] since it is one of the most resistant forms of spore forming organisms. Bacillus subtilis are known for their involvement in systemic conditions such as sub-acute bacterial endocarditis and urinary tract infection while Staphylococcus aureus are known to cause dermatological lesions, pyemia and endocarditis.

According to  Atlas More Details and Parks the organisms used in this study can be isolated in nutrient broth, and readily grow in nutrient agar [1]. This medium provided satisfactory growth in our study as observed by other workers. All the three test organisms used in this study are facultative anaerobes. In this study we have used aerobic culturing procedure so as to provide the best environment for growth. Since the bacteria used in the study are fast growing, non fastidious organisms and could grow within 12-18 hours, the incubation was restricted to 24 hours only.

Three different disinfectants were used to wipe the contaminated files to determine the effect of sterilization. Care was taken to provide strict aseptic condition to prevent contamination of air­borne organisms. It has been observed that the wiping with disinfectant resulted in a decrease in time required for sterilization. There was a greater reduction in time in the case of vegetative organisms when compared to spore forming organism. This observation is in confirmation with the earlier workers.

The results obtained in this study by wiping the files with 5.25% sodium hypochlirite and 95% Isopropyl alcohol were similar, and proved to be more effective than 2% Glutaraldehyde. In this study we have shown that these organisms are more efficiently sterilized by glass bead sterilizer after wiping the files with gauze soaked in 5.25% sodium hypochlorite, 95% Isopropyl alcohol and 2% Glutaraldehyde before immersing into the glass bead sterilizer.

While comparing the efficiency of sterilization with larger and smaller glass beads it was observed that larger glass beads required 35 seconds to kill Bacillus subtilis when compared to 30 seconds with smaller glass beads. The time required for files dipped in Streptococcus fecalis and staphylococcus aureus with larger glass beads was 30 seconds when compared to 25 seconds with smaller beads. This may be attributed to better conduction of heat by smaller glass beads. In this study, the files were placed along the periphery of the sterilizer to utilize the maximum temperature for effective sterilization. The reason for the lower temperature at the center of the cylinder is due to the fact the heat to travel through the glass beads and the dead air space between the glass beads to reach the center. Further, it has been claimed that smaller glass beads result in a better conduction of heat when compared to larger glass beads where the presence of air space results in poor conduction of heat.

From the foregoing analysis and discussion it is evident that the use of effective infection control procedures in dental practice will prevent cross contamination among the dentists and dental staff and nosocomial infections in patients. The present study indicates that disinfection followed by chairside sterilization with glass bead sterilizer can be considered as an ideal procedure of choice in clinical practice.[Figure 1]

   References Top

1.Atlas RM, Parks L : Microbiological media, CRC Press, 1933  Back to cited text no. 1    
2.Averbach RE, Kleier DJ : Armamentarium and sterilization in Pathways Of Pulp edited by Cohen S and Burns RC 6 th edititon CV Mosby Co 1994  Back to cited text no. 2    
3.Council of Dental materials, Instruments and Equipments, Counicl of Dental Practice, Council of Dental Therapeutics : Infection control recommendation for dental office and the dental laboratory. J.Am Dent Asso Vol. 116 Feb 1988  Back to cited text no. 3    
4.Custer F, Anderson R : A study of surface changes in instruments during sterilization procedures NYJ Dent 38 : 8-17,1968  Back to cited text no. 4    
5.Deyoub MB, Devine MJ : Endodontic dry heat sterilizer effectiveness J.Endo 2(11) 1976  Back to cited text no. 5    
6.Eichner MA Schoen DM, Goldman M, Kronman J : Effect of Protein and sodium hypochorite on endodontic instruments . J Endo 29 (11) 1976  Back to cited text no. 6    
7.Engelhardt JP, Grun L, Dahl HJ : Factors affecting sterilization in glass bead sterilizers. J Endo 10(1) 1984  Back to cited text no. 7    
8.Fahid A, Taintor JF : The influence of file size, cleaning and time on effectiveness of glass bead sterilizers. Oral Surg 58 :443-445, 1984  Back to cited text no. 8    
9.Goldstein J, James G : Steilization of endodontic equipment and materials in Endodontics Edited by Ingle JI, Taintor JF P Edition. Lea and Febriger, 1985  Back to cited text no. 9    
10.Grossman LI : Dental instrument sterilization by glass bead conduction of heat. J.Dent Res 57(1) 72-73,1978  Back to cited text no. 10    
11.Grossman LI : Principles of endodontic treatment in Endodontic Practice 11'h Ed Varghese Publishing House (India Ed) 1988  Back to cited text no. 11    
12.Hubbard TM, Smyth RN, Pelley GB, Tenca JI : Chair side decontamination of endodontic tiles, oral surg oral med oral path 40 : 148­152 1975  Back to cited text no. 12    
13.Hurrt CA Rossman LE : The sterilization of endodontic hand files. J Enod 22(6) 1996  Back to cited text no. 13    
14.Ingle JI : Microbiology of Endodontics in Endodontics 5` h Edition BC Decker Inc 2002  Back to cited text no. 14    
15.Kekehashi S, Stanley HR, fitzgerald RJ : The effects of surgical exposure exposure of dental pulps in a germ free and conventional laboratory rats. Oral Burg 20 340 1965  Back to cited text no. 15    
16.Miler CH : Cleaning, sterilization and disinfection. Basics for microbial killing for infection control. J. Am Dent Asso 124 : Jan 1993  Back to cited text no. 16    
17.Neal RG, Craig RG, Powers JM : Effect of sterilization and irrigants on the cutting ability of stainless steel files J Endo 9 (3) 983  Back to cited text no. 17    
18.Sahli CC, Pumarola Sune J, Espias -Gromez A, Jimernez Polanceos P : Efficacy of glass bead sterilizer on endodontic instruments Revue Francaise d'endodontie 8(4) 1986  Back to cited text no. 18    
19.Segall RO, del Rio CE, Brady JM, Ayer WA Evaluation of debridement techniques for endodontic instruments oral surg 14 (5)1977.  Back to cited text no. 19    
20.Senia ES, Marraro RV, Mitchell JC, Lewis AC and Thomas L : Rapid sterilization of gutta percha cones with 5.25% sodium hypochlorite J. Endo 1:130-149, 1975  Back to cited text no. 20    
21.Sisco V, Winters LL, Zange LL, Brennan PC Efficacy of various methods of Sterilization 11(2) 1988  Back to cited text no. 21    
22.Subbarao CV, Rajan BP, Subramani S Antibiotic sensitivity pattern of the Asso 50 7-12, 1978  Back to cited text no. 22    
23.Windeler AS, Walter RG : The sporicidal activity of glass bead sterilizers J Endo 1 (8) 1975  Back to cited text no. 23    

Correspondence Address:
Department of Conservative Dentistry, Balaji Dental College and Hospital
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-0707.42588

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  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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