Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2006  |  Volume : 24  |  Issue : 2  |  Page : 76--79

Chair side simple caries activity test: Ora test

Bhasin S1, Sudha P2, Anegundi R T3,  
1 Former P. G. Student, CODS, Mangalore, India
2 Head of Department, Dept of Pedodontics, CODS, Mangalore, India
3 Dept. of Pedodontics, S. D. M. Dental College, Dharwad, India

Correspondence Address:
Sudha P
Dept of Pedodontics, College of Dental Surgery, Mangalore


Oratest, a caries activity test was performed on 48 school going children of Mangalore city to estimate efficacy of the test. High statistical significance was found when the means of control and test group were compared [γ = 0.913]. The Oratest is found to be a simple chair side, less time consuming and inexpensive caries activity test.

How to cite this article:
Bhasin, Sudha, AnegundiR. Chair side simple caries activity test: Ora test.J Indian Soc Pedod Prev Dent 2006;24:76-79

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Bhasin, Sudha, AnegundiR. Chair side simple caries activity test: Ora test. J Indian Soc Pedod Prev Dent [serial online] 2006 [cited 2020 Sep 26 ];24:76-79
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Caries activity tests are based on the concept of a specific odontopathic infection, the principle causative organism being Streptococci mutans. Their predominance is attributed to its acidogenic and aciduric nature after a selective growth advantages over the other non-acid tolerant organisms.[1]

Many studies on caries activity are aimed at finding relevant micro organisms. But to date, the ideal method to evaluate in terms of sensitivity, specialization and reliability has not been found. However, in routine clinical practice these caries activity tests require specially prepared culture media and laboratory facilities for incubation and expensive kits to perform them.[2]

Unfortunately, many of these caries activity tests requires extensive work up time and additional equipment. Simple, inexpensive techniques, which do not demand, sophisticated skills or consume much time are required for the caries activity tests and the status they deserve in the routine clinical practice and epidemiological screening programs. Rosenberg et al[3] in 1989 developed Oratest, a simple, economical, non-invasive and less time consuming test for estimating the oral microbial level. This study was designed to estimate the efficiency of the simple Oratest, as a measure of oral microbial levels.


Oratest is based on the rate of oxygen depletion by micro organisms. Under aerobic conditions the bacterial enzyme, aerobic dehydrogenase transfers electrons or protons to oxygen. Once oxygen gets utilized by the aerobic organisms and an anaerobic environment is attained, methylene blue [redox indicator] acts as an electron acceptor and gets reduced to leucomethylene blue. The metabolic activity of the aerobic microorganism is reflected by the reduction of methylene blue to leucomethylene blue.

The test is based on rinsing the mouth with sterile milk which dislodges the micro-organisms and also produces a substrate for their further metabolism. The formation of leucomthylene blue can be easily observed because of the white color of milk. [Table 1] shows advantages and disadvantages of Oratest.[4]

 Materials and Methods

48 School going children of Mangalore city were randomly selected from those who reported to the Department of Pedodontia and Preventive Dentistry, College of Dental Surgery, Mangalore. The study was done in association with the Department of Microbiology, Kasturba Medical College, Mangalore, after obtaining the parent consent.

The study sample was divided into 2 groups

Group I [test group] and Group II [control group] consisting 24 children in each. The criteria for selection of subjects in group I was, children with dental caries involving one or more teeth and Gingival index score of Zero [L φe and Silness index]. Children in group I were further divided into 1,2 and 3 sub groups according to the deft and DMFT of 2-5, 6-10 and 11-18 respectively. The criterias for selection of subjects in group II was, children free from caries, gingivitis and plaques score of zero as per modified Silness and L φe plaque index.


The armamentarium used were:

- Sterilized milk - 0.1% aqueous solution of

methylene blue.

- Sterile beakers - Screw cap test tubes.

- 5ml disposable syringes- Sterile pipettes.

- Mirror - Test tube stand.

- Water. [Figure 1]


The children were asked to rinse their mouth vigorously for 30 seconds with 10 ml of ultra-high temperature sterilized cow's milk containing 3% of fat. The expectorate was collected in a sterile beaker and 3 ml was immediately transferred with a disposable syringe to a screw cap test tube, which contained 0.12 ml of 0.1% methylene blue. (0.1% methylene blue was obtained by mixing 100 mg of methylene blue in 100 ml of distilled water.) The expectorated milk and methylene blue was thoroughly mixed and the test tube was placed on a stand in a well illuminated area. A mirror was used to detect any color change [blue to white] in the bottom of the test tube every 5 minutes. The time taken for the initiation of the color change within a 6 mm ring was recorded [Figure 2][Figure 3].

The data was fed into the computer with Excel and statistical package SPSS version 7 was used. The tests used were χ 2 test, Mann-whitney "U" test, ANOVA and Speramann rank correlation.

 Observations and Results

Oratest was conducted on 48 children randomly selected from those who reported to Department of Pedodontics. The subjects were divided into a test group [Group I] and control group [Group II] of 24 children in each. The mean time for the color change of methylene blue was 148 min 38 for the control group and 58 min 41 was the mean time taken for color change from blue to white in the test group. Comparison between the means of these two groups was found to be statistically very highly significant [ P =0.000]. The correlation between the deft/DMFT and time was found using the Spearman rank correlation and it was found to be negatively correlated [γ =-0.913, P =0.000 VHS] where γ is the correlation coefficient [Table 2].

The test group was divided into 3 subgroup according the deft/DMFT values. Subgroup 1 had children with 1-5 carious teeth, subgroup 2 and subgroup 3 consisted of children with 6-10 and 11-15 carious teeth respectively. The maximum time for color change observed in subgroup 1 was 91 min 21, which had a mean deft/DMFT of 3 1.07. Shortest time for color change observed in the Group 3 was 28 min 7. Subgroup 2 with a mean deft/DMFT of 7.91 1.14 had a mean time for color change of 36 min 8. The correlation between the deft/DMFT and time was found to be negatively correlated for subgroup 1 and 3. The values for subgroup 1 and 3 were γ =-0.592; P =0.122 and γ =0.495 respectively. In subgroup 2, a positive correlation was seen between deft/DMFT and time [γ =0.172; P =0.614].

The plaque index of the 48 subjects was negatively correlated with the time needed for initiation of color change [γ =-0.494, P =0.000 VHS [Table 3]].


The growing interest in the microbiological aspects of dental caries has lead to the development of a variety of diagnostic procedures. A number of caries activity tests have been developed to help detect the presence of oral conditions associated with increased caries risk. For individual patients, currently no single caries activity test can be relied upon to predict caries with a high degree of confidence. Since, many of these tests rely on the samples of salivary bacteria. The reliability of such tests is limited, because the bacteria that are free-floating in the saliva may not necessarily represent the bacteria in plaque and these tests, also need extensive working time and expensive armamentarium.[1]

Individual caries activity tests, despite their limitations can be useful adjuncts to the clinical practitioner, by guiding the clinician in making decisions concerning the need for control measures, the timing of recall appointments, the types of indicated restorative procedures, materials and the determination of the prognosis. The test results also can also be used to motivate patients and to determine patient compliance with treatment regimes. A simple, inexpensive technique, which does not demand sophisticated skills or consume less chair side time will help to give the caries activity tests the status they deserve in routine clinical practice.

In the present study, 48 children were randomly selected from the Department of Pedodontics for the Oratest.[3] It was noted that the correlations were slightly altered by drinking or eating prior to the test, thus all subjects in the study were taken only after a lapse of 90 minutes since the last intake of food or drink. The test was based on whole mouth rinsing with sterile milk, which is a suitable vehicle as it dislodges microorganisms mildly yet effectively. It is non-toxic, provides an excellent medium for subsequent metabolism and also readily acceptable by the children.

The expectorate was then added with the methylene blue and the time taken for initiation of color change was noted. The time taken for color change of methylene blue was compared with the deft/DMFT values and plaque index scores. For the control group, the time taken for color change was 148 min 38 and was 58 min 41 for the test group. A statistically high significance was found when comparing the means of the 2 groups [γ = -0.913; P =0.000]. These findings were in agreement with the findings of Patalay et al , Anand et al[5],[6] who performed Oratest on 50 children. They found the mean time taken for the color change was 279.9 min 89.74 in the control group and 55.6 min 66.33 for the test group. The difference between the 2 groups was highly significant.

In the present study maximum time taken for color change [91 min 21] was observed in children with 1-5 carious teeth and the minimum time taken for the color change [28 min 7] was in children with 11-15 carious lesions. Similar findings were reported by Patalay et al and Anand et al .[5],[6]

In the present study, when all 48 subjects were grouped together, linear regression analysis of the logarithm of time required for color change as a function of plaque index, yielded a correlation coefficient of -0.494 [ P =0.000]. Tal Haim and Rosenberg Mel[3] observed similar results when they compared Oratest scores with commonly used techniques for clinical evaluation of plaque levels and gingival inflammation. They also reported that higher the Oratest scores, lower the value of plaque index [γ = 0.58, P =0.001].

As the Oratest, gives positive observations in cases of gingival diseases, periodontal diseases, halitosis etc, its limitation is the lack of specificity, as it does not identify the source of micro organisms. The test can be easily learnt by the auxillary personnel and hence can be used as a diagnostic tool in school health programs. The positive results can easily be visualized by the practitioner, child and the parent and thus can be used to motivate. As it does not require any special instruments, it can be used to monitor treatment progress. It can provide a baseline with which subsequent changes in clinical status and oral hygiene [i.e., following oral prophylaxis] can be monitored in a chair side or even home environment.

The present study, thus further proved the hypothesis that higher the level of infection, lesser was the time taken for the change in color of the expectorate, reflecting higher oral microbial levels.[3] Thus, the test can be used as one of the tool, to estimate the activity of demineralization by the bacteria conducive to the suitable environment.

Oratest, a simple chair side caries activity test provides a reliable estimate of oral microbial levels. Significant overall correlations were observed between oratest data and deft/DMFT or plaque index.

A caries activity test facilitates the clinical management of patients as they determine the need and extent of personalized preventive measures. It serves as an index for the success of therapeutic measures and also help and to motivate and monitor the effectiveness of educational programs relating to dietary and oral hygiene procedures. It is of particular importance in identifying high - risk groups and individuals.


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