Indian Journal of Dental Research

: 2014  |  Volume : 25  |  Issue : 2  |  Page : 160--165

Effect of chlorhexidine, povidone iodine, and ozone on microorganisms in dental aerosols: Randomized double-blind clinical trial

Ravleen Kaur1, Inderjot Singh2, KL Vandana3, Rajendra Desai4,  
1 Department of Periodontics, Christian Dental College, Ludhiana, Punjab, India
2 Department of Oral and Maxillofacial Surgery, Christian Dental College, Ludhiana, Punjab, India
3 Department of Periodontics, College of Dental Sciences, Davangere, Karnataka, India
4 Department of Oral and Maxillofacial Surgery, College of Dental Sciences, Davangere, Karnataka, India

Correspondence Address:
K L Vandana
Department of Periodontics, College of Dental Sciences, Davangere, Karnataka


Objective: Dental handpieces, ultrasonic scalers, air polishers, air abrasion units produce the most visible aerosols. The objective of this study was to assess the effect of chlorhexidine (CHX), povidone iodine (PI), and ozone (OZ) on the microorganisms in dental aerosols. Materials and Methods: A total of 60 patients were included in this study, they were randomly assigned into three groups and were subjected to scaling before and after rinsing with 0.2% CHX, 1% PI or irrigation with OZ. Blood agar plates were used to collect the gravitometric settling of aerosols and were sent for aerobic and anaerobic culture. Results: The results demonstrated high percentage reduction of aerobic and anaerobic colony forming units (CFUs) in all three groups. In aerobic CFUs, CHX showed the highest reduction (57%) at mask position whereas at chest position and at 9 ft, PI showed higher CFU reductions (37% and 47%, respectively). In anaerobic CFUs, CHX showed the highest percentage of reduction at chest level (43%) and at 9 ft (44%). Conclusion: CHX, PI and OZ showed similar effects in reducing aerobic and anaerobic CFU«SQ»s at the chest mask and at 9 ft. OZ can be used as a preprocedural agent, considering its beneficial effects.

How to cite this article:
Kaur R, Singh I, Vandana K L, Desai R. Effect of chlorhexidine, povidone iodine, and ozone on microorganisms in dental aerosols: Randomized double-blind clinical trial.Indian J Dent Res 2014;25:160-165

How to cite this URL:
Kaur R, Singh I, Vandana K L, Desai R. Effect of chlorhexidine, povidone iodine, and ozone on microorganisms in dental aerosols: Randomized double-blind clinical trial. Indian J Dent Res [serial online] 2014 [cited 2022 Aug 11 ];25:160-165
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Full Text

Dental professionals are at high-risk for developing infectious diseases. The major source of potential aerosol contamination in a dental set up is the ultrasonic scaler. [1] Veksler et al. have demonstrated that preoperative rinsing with 0.12% chlorhexidine (CHX) gluconate diminished the quantity of aerobic and facultative flora of the oral cavity. [2] Povidone iodine (PI) as a preprocedural rinse effectively reduces gingival surface flora prior to oral prophylaxis with ultrasonic scalers and maintains this reduction throughout the duration of the prophylactic procedure. [3] Ozone (OZ) (O 3 ), which is an allotropic form of oxygen (O 2 ), has also been shown to have some therapeutic effects in dentistry. [4],[5],[6]

Hence, an attempt was made to measure the effect of CHX gluconate, PI and OZ on the reduction of viable bacteria in the dental aerosols.


This study was a randomized, double-blind clinical trial in which 60 patients of both sexes within the age range of 20-50 years were selected. Sample size determination was done on the expense of data collection and the need to have sufficient statistical power and randomization was done on an alternate basis, which was double-blinded. This study was done under the ethical guidelines of the Institutional Research and Ethical Committee. Participants who met the minimal criteria for entry were informed about the purpose of the study, and each patient was provided with an informed consent, after the nature of the procedure and possible discomforts and risks had been fully explained.

Criteria for participation included having a minimum of 20 permanent teeth and excluded any patient who was diagnosed as periodontitis, had medical conditions or taking medications that would contraindicate treatment. Plaque index [7] and Gingival bleeding index [8] were recorded for every patient in the first sitting.

All subjects were assigned to one of three groups (CHX, PI, and OZ) by using a randomization table. To maintain full blinding of the results, the randomization code was held by one of the authors remotely from all assessments and wasn't broken until all data had been collected and analyzed.

Based on the reports that had used similar methods, [2],[9] a 30-min baseline sampling was collected, placing the agar plates at the designated areas, to determine if there is/was any aerosols present in the room before conducting scaling.

Three standardized locations in the same operatory [Figure 1], measuring 30 × 10 × 12 ft were chosen to be evaluated for the aerosol collection that is, chest of the patient, [1],[10],[11] mask of the operator, [1],[9],[10],[11] and 9 ft behind the patient was considered as a parameter in this study as the sterilization operatory and the dental assistants are most often found behind the chair.{Figure 1}

For each patient, three set of agar plates were exposed during the study. The first set of plates were exposed to record the baseline samples for 30 min before the start of the scaling procedures [Figure 2]a]. The second set of plates were exposed at the three designated areas, during the prerinse scaling lasting 10 min followed by 30 min of postscaling exposure (total of 40 min). The third set of agar plates were exposed during postrinse/irrigation scaling for 40 min (10 min during scaling and 30 min postscaling). Supragingival scaling was performed in all subjects with respect to upper anterior segment (tooth number 13-23).{Figure 2}

After the baseline sampling, the patient scaling was performed for 10-min by the operator, with universal tip attached to the ultrasonic scaler. To ensure the room was free from aerosols, only one patient was treated per day. During each scaling procedure, saliva ejector was used. The same procedure was carried out on all subjects by a single operator who was blinded of both, the mouth rinse and irrigation provided to the subjects.

During the treatment, and for 30-min after the treatment, three coded blood agar plates were left uncovered at the predesignated sites to collect samples of aerosolized bacteria. This was followed by rinsing with 0.2% CHX/1% PI or supra-gingival irrigation with ozonated water (OZ output of 0.082 mg/h), for 1 min period. The patients were again subjected to 10-min of scaling by the operator, with the exposure of fresh blood agar plates during the treatment and for 30-min after the treatment [Figure 2]b].

After collecting the samples, blood agar plates were incubated aerobically at 37°C for 48 h and anaerobically in an increased CO 2 chamber for 48 h. Colonies were counted using the colony counter device by the examiner, who was blinded of the rinse provided.

Statistical analysis was performed using one-way ANOVA for plaque index and gingival bleeding index. Paired t-test and post-hoc Turkey's test were performed for analyzing aerobic and anaerobic colony forming units (CFUs).


In this study, 60 patients were selected and were randomly divided into CHX, PI, OZ groups; each group consisted of 20 patients. The clinical parameters recorded that is, plaque index and gingival bleeding index, showed statistically nonsignificant results as shown in [Table 1]. For this study, 60 patients were selected with gingivitis and the mean of their plaque index [7] indicated that all the subjects participating in the study fell in the range of 1.0-1.9. The mean difference between the three groups was 0.55 and P value of 0.58, which was statistically nonsignificant. Mean of gingival bleeding index [8] had the range 20-40%. The mean difference between the three groups was 2.14 and P value of 0.13 which was statistically nonsignificant. The results are discussed here as shown in [Table 1], [Table 2], [Table 3].{Table 1}{Table 2}{Table 3}

At baseline, in all the three standard positions (mask, chest and 9 ft), on inter-group comparison, the difference between the mean values of the three groups, that is, group CHX and PI (P value 0.72), group CHX and OZ (P value 0.97) and group PI and OZ (P value 0.85), was statistically nonsignificant [Table 2].

In aerobic culture, at mask position, within each group (CHX, PI, and OZ) the post rinse CFU reduction was significant as compared to prerinse levels. In intergroup comparison, the mean values of all the three groups at the mask level, P value was 0.28, which was nonsignificant. Comparing the P values between the groups, that is, group CHX and PI (P value 0.30), group CHX and OZ (P value 0.97) and group PI and OZ (P value 0.41), were all statistically nonsignificant [Table 2].

At chest position, within each group (CHX, PI and OZ) the post rinse CFU reduction was significant when compared to prerinse levels. In intergroup comparison, the mean values of all the three groups at the chest of the patient, P < 0.01, which was significant. Comparing the P values between the groups, that is, group CHX and PI (P < 0.01), and group PI and OZ (P < 0.01), were statistically significant, but the difference between groups CHX and OZ (P value 0.78) was statistically nonsignificant.


The American Dental Association has recommended that potential contaminated aerosols or splatter be controlled during dental procedures. [12] While there have been no definitive epidemiologic studies that have linked dental aerosols to disease transmission, the presence of a cloud of contaminated aerosol and splatter, such as that produced by an ultrasonic scaler, should be of concern to the dental practitioner. [1] This study demonstrates that a sufficient amount of aerosol and splatter from the patient will be ejected far enough to come into contact with dental personnel.

In conducting this study, an attempt was made to evaluate and compare the ability of different preprocedural rinsing agents to lower the microbial counts during the use of aerosol producing ultrasonic scalers. The results of this study showed that there was a significant reduction of the bacterial CFU in all the three groups, showing the maximum reduction of up to 57%.

The prerinse level of CFU was maximum at patient's chest followed by the operator's mask and at 9 ft. The highest CFU at the patient's chest position is similar to the findings of Bentley et al. who observed the larger salivary droplets generated during dental procedures settle rapidly from the air with heavy contamination on the patient's chest. [10]

In this study, the prerinse CFU at the mask followed the chest CFU values. Worrall et al. also found that the highest counts were found near the headrest. [13] However, King et al. have reported that CFU count on the face-shield of the operator were found to be less, as the operator was exposed to a deflected spray and not the direct spray that is emitted straight from the subject's mouth. [14] At 9 ft in front of the patient, CFU being decreased have been reported, revealing that the number of CFU decrease as the distance from the reference point increased. [9],[10]

The post rinse CFU's using CHX, PI, and OZ are as follows. At mask position, the reduction in aerobic colonies from prerinse to post rinse was maximum for CHX group (57%), PI group showed 54%, whereas OZ group showed 47%.

Chlorhexidine showed significant reductions in aerobic and facultative bacteria on the mask of the operator followed by the chest of the patient and 9 ft behind the reference point. Logothetis and Martinez-Welles also showed that CHX gluconate pretreatment rinse was effective in reducing bacterial aerosol contamination with the use of air polisher. [9] Muir and others found that a 2 min prerinse with CHX significantly reduced aerosols produced by ultrasonic scalers. [15] Toroπlu et al. have reported that the level of viable microbial bacteria cannot be reduced significantly by preprocedural rinse of 15 ml of 0.2% CHX for 1 min. [16]

In PI group, significant reduction was seen at all the positions, showing maximum reduction of 54% at mask position. This finding may result from the antiseptic mouthwash's ability to inhibit microbial growth. PI is good for quick microbicidal activity unlike CHX which has substantivity effect. [17] It can also be supported by early study by Vanderwyk who noted microbicidal activity of PI showing 72% reduction for 30 min after rinsing and the decrease was still 38% below the prerinse count after 90 min. [18] Cawson and Curson studied the topical effect of 2% tincture iodine and 2% CHX in alcohol and both were found to provide the best antimicrobial activity on the oral mucosa. [19] PI is good for Mycobacterium tuberculosis control while CHX has no adequate antimicrobial effect on M. tuberculosis. [20],[21]

The OZ group also showed significant reductions in CFU, with the maximum reduction of aerobic colonies up to 47% and anaerobic colonies of 35%. Nagayoshi et al. have reported the antimicrobial property of ozonated water and effectiveness for killing Gram-positive and Gram-negative oral microorganisms. [4] An in vivo short term study has reported the antimicrobial, antiviral and antifungal effect of single OZ irrigation. [5] Powered irrigation removed 3 times as much debris and bacterial products as did rinsing and proved that water irrigation was more effective than rinsing. [22] OZ irrigation was used in the present study as OZ rinse was not available.

The results of this study demonstrated maximum reduction of aerobic colonies using CHX rinse at the operator's mask position where as PI exhibited maximum reduction at the patient's chest position to 9 ft behind patient. The OZ group demonstrated lesser reduction of aerobic and anaerobic colonies probably owing to the unstable nature of OZ. [23] However, the reliable microbiologic and metabolic properties of OZ, in either the gaseous or aqueous phases, make it a useful disinfectant with a wide range of activity. OZ, in gaseous or aqueous phases, has been shown to be a powerful and reliable antimicrobial agent against bacteria, fungi, protozoa, and viruses. [5],[23]

The anaerobic culture of aerosol was considered only for the chest position and at 9 ft. The highest anaerobic CFU reduction was found at chest position and at 9 ft for CHX group followed by PI and OZ group.

All the three groups (CHX, PI, and OZ) reduced the growth of CFUs, suggesting that a CHX and PI preprocedural rinse are definitely similar in reducing aerosolized bacteria. The broad antimicrobial effects of CHX includes significant reductions in the numbers of total aerobes (65-85%), anaerobes (42-80%), streptococci (44-78%) and actinomyces (85-97%). [24] CHX also has binding property (substantivity) which enables CHX to bind to the bacterial surfaces and affect the adherence as well as to initiate bacterial destruction. [25]

Though the results present a strong case for mouth rinsing before the dental procedure, few dentists use mouth rinsing as a means to either minimize endogenous spread of infection from patient to the dentist or the dental auxiliaries on a routine basis, why this procedure has not gained more acceptance, is an enigma. Barriers to its implementation may be the taste and the cost of the mouth rinse. Nevertheless, the explanation of the benefits should convince the most reluctant patients to participate.

The extent of this potential hazard due to aerosols is difficult to estimate since there is no evidence in literature that specific disease has been caused in dental personnel by contaminated aerosol or dust. Nevertheless, such contamination must be regarded as undesirable and aerosol control measures such as preprocedural rinse should be strictly implemented in periodontal clinic.

The present study results have prompted a consideration of the routine use of CHX and PI mouthwash as prior to all dental procedures as it results in the reduction in number of oral bacteria available for possible induction of bacteremia or dissemination to the attending dentist and other personnel. OZ irrigation could also serve as a good preprocedural rinse.

The limitations of this study should be considered in the interpretations of the results. The CFUs counted here are values that represent the bacteria capable of growth on blood agar plates. No attempt has been made to identify the type of bacteria, either pathogenic or nonpathogenic. Moreover, viruses, fungi and specific bacteria require specialized media, which were not cultured in this study.

Future studies are needed to investigate the viable pathogenic microorganisms generated during the use of ultrasonic scaling device. The plate count (CFU) only provides an approximation of the number of bacterial cells in the air and these approximations do not take into account the viral content within the aerosols. The ability to grow cultures is ultimately dependent on the ability to isolate, or capture, the original organism. Recent scientific advancements have seen the development of denaturing gradient gel electrophoresis and the use of microarrays as a source of rapid and accurate bacterial detection and identification. Furthermore, being in aqueous or gaseous state, the higher concentrations of OZ can be tested for its antimicrobial effect.

Continued studies could include a repeat of this study using an air sampler unit, which defines the actual respiratory effects of aerosols.

Clinical transfer of this study result is that the preprocedural rinse should be compulsory to prevent disease transmission through aerosols. It becomes mandatory especially in those patients with infectious diseases. To prevent aerosol transmission in such cases, hand scaling is a better choice.


This study indicates that a preprocedural rinse can significantly reduce the viable microbial content of aerosols generated during scaling. Although OZ showed lesser CFU reductions, considering its antibacterial and beneficial effects, OZ can be used as preprocedural agent. Hence, preprocedural rinsing may be of value in protecting patients and dental professionals during dental procedures.


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