caries activity tests-for detection of caries
- 2. Introduction Caries activity: refers to increments of active caries lesions over a stated period of time. Caries susceptibility: refers to inherent tendency of host, target tissue & tooth to be afflicted by carious process. Caries activity tests: measure the degree to which the local environment challenge favors the probability of carious lesions.
- 3. Determine the need & extent of personalized preventive measures. Serve as an index of the success of therapeutic measures. Motivate & monitor the effectiveness. Manage the progress of restorative procedures. To identify high risk individuals.
- 4. Tests. Lactobacillus col0ony count test Synder test Swab test. S mutans level in saliva Dip slide method for S mutans Salivary buffer capacity test. Enamel solubility test Salivary reductase test Alban test S mutans screening test Fosdick calcium dissolution test Dewar test
- 5. Lactobacillus colony count test. Estimates the number of acidogenic & aciduric bacteria in patients saliva by counting the colonies appearing on tomato agar plate after inoculation with a sample of saliva. A selective media favouring the growth of aciduric lactobacilli is the basis of test.
- 6. Procedure. Colllect the stimulated saliva & shake it. Saliva sample is diluted to 1: 10 dilution by pipetting 1ml saliva into 9ml saline solution. 1: 100 dilution is made by pipetting 1ml of 1:10 dilution into another 9ml tube of saline solution. 0.4ml of each dilution is spread on the surface of agar plates. Plates are incubated for 3 – 4days at 37 C . Colonies are counted The number of lactobacilli/mm saliva is calculated by multiplying the number of colonies on plate by the dilution factor of its inoculums.
- 7. L bacilli counts i.r.t caries susceptibility No of organisms/c.c Symbolic designation Degree of caries activity suggested 0 - 1000 +/- Little/ none 1000 - 5000 + Slight 5000 - 10000 ++ Moderate More than 10000 +++ Marked
- 8. Advantage & disadvantages. Usefull for monitoring the effectiveness of restorative care Simple to carry out. Used as a screening test for caries activity I n large groups. Inacurate in predicting the onset of caries. does not completely exclude the growth of other aciduric org. Counting is tedious process. Counts involving single individuals are not reliable.
- 9. Calorimetric Snyder test. Measures the ability of salivary microorganisms to form organic acids from a carbohydreate medium. Medium contains an indicator dye, Bromocresol green. Colour changes from green to yellow in the range of pH 5.4 – 3.8. Test also measures acidogenic & aciduric bacteria.
- 10. Procedure. 0.2 ml stimulated saliva is collected & mised with 10 ml melted agar containing medium in test tube cooled to 50C, allowed to solidify & then incubated at 37C. Amount of acid produced is indicated by changes in pH indicator & is compared to an uninoculated control tube after 24, 48, 72 hours. Rate of colour change from green to yellow is indicative of degree of caries activity.
- 11. Colour observations in Snyder test 24 hr 48 hr 72 hr If yellow Marked caries susceptibility If yellow Definite caries susceptibility If yellow limited caries susceptibility. If green continue to incubate & observe at 48 hr. if green continue to incubate & observe at 72 hr. if green caries inactive.
- 12. Advantages & disadvantages Simple to carry out. Test are of value in assessing the oral environment mental cariogenic challenge. No dilutions are required. Time consumed is more Sometimes colour changes are not clear.
- 13. Swab test Based on same principle like Snyder test. Oral flora is sampled by swabbing the buccal surfaces of teeth with cotton applicator, which is subsequently incubated in the medium. Change in pH following a 48 hour incubation is read on pH meter/ colour change is read by use of colour comparator.
- 14. Interpretation pH 4.1 & < 4.1 = marked caries activity pH 4.2 – 4.4 = active pH 4.5 – 4.6 = slightly active. pH 4.6 & above = caries active.
- 15. Advantages Test is of value in predicting caries increments, particularly in children with low or no previous caries experience. No saliva collection.
- 16. S mutans level in saliva. Test measures the number of S mutans CFU/ unit volume of saliva & culturing of plaque samples from discrete sites, such as occlusal surface, preximal area is used for detecting & quantitating S mutans. Incubation is done on Mitis salivarius agar selective medium with addition of high concentrated of sucrose 20% & 0.2 bacterium/ ml supress the growth of mutans colonies.
- 17. Procedure. Sample is collected by tongue blades which are then pressed against S mutans selective MSB against petri dishes. Plates are incubated at 37C for 48 hours in 95% at 5% Co2 gas mixture.
- 19. Advantages & Disadvantages. The count is used as an adjacent in caries management. Difficulty of distinguishing between a carrier state & cariogenic infection. S mutans may constitute less than 1% of total flora of plaque. Mutans tend to be located at specific sites only.
- 20. Dip slide method for S mutans count. Method is devised for the estimation of S mutans level in saliva. Undiluted stimulated saliva is poured on special plastic slide coated with MSA containing 20% sucrose. Two discs containing 5 mg of bacitracin are placed on agar 20 mm apart. Slide is tightly screwed & incubated at 37C for 48 hours in sealed candle jar.
- 21. Evaluation. Score 1 = low: the colonies are discrete & could be readily counted at 15x magnification with the total count of CFU inside less than 200. Score 2 = Medium: the colonies are discrete & the number in the zone of inhibition is more than 200 & 32x magnification. Score 3 = High: colonies are tiny & almost completely cover the inhibition zone with colonies uncontrollable even with 32x magnification.
- 22. Salivary buffer capacity test. Test measures the no of ml of acid required to lower the pH of saliva through an arbitrary pH interval, such as from pH 7 – 6 or the amount of acid or base necessary to bring colour indicators to their end point. Buffer capacity is quantified using pH meter or colour indicators.
- 23. Procedure. 10 ml of stimulated saliva is collected under oil at least 1 hr after eating; 5ml of this is measured into beaker. After correcting the pH meter to room temp, pH of saliva is adjusted to 7 by adding lactic acid or base. Level of lactic acid is then added to sample until a pH of 6 is reached. The number of ml of lactic acid needed to reduce pH from 7 – 6 is measure of buffer capacity.
- 24. Evaluation. Test gives inverse relationship between buffering capacity of saliva and caries activity. The saliva of individuals whose mouth contain a considerable number of carious lesions frequently has low buffer capacity.
- 25. Advantage : simple to carry out. Disadvantage : do not correlate adequately with caries activity.
- 26. Enamel solubility test. It is based on the fact that when glucose is added to saliva containing powdered enamel, organic acids are formed. Decalcify the enamel, resulting in an increase in amount of soluble calcium in the saliva – glucose - enamel mixture. The extent of increased calcium is direct measure of degree of caries susceptibility.
- 27. Disadvantage Not suitable for office procedures. Complex equipments are required High cost Need personnel training.
- 28. Salivary reductase test. Measures the activity of reductase enzyme present in salivary bacteria. Saliva is collected in plastic container & the sample is mixed with dye diazoresorcinol. Colour changes & caries conduciveness reading is taken after 15 min.
- 29. Colour Time Score Caries activity Blue 15 min 1 Non conducive Orchid 15 Min 2 Slightly conducive Red 15 mins 3 Moderately conducive Red Immediately 4 Highly conducive Pink/ white immediately 5 Extremely conducive.
- 30. Advantages & disadvantages Quick results No incubation required Test results vary with time after food intake & brushing.
- 31. S mutans screening test : Plaque/ tooth pick method. Test involves a simple screening of dilute plaque sample streaked on selctive culture media. Plaque samples are collected from gingival third of buccal tooth surfaces from each quarant & placed in Ringers solution. Sample is shaken till homogenized. Plaque suspension is stretched across MSA plates. Incubated at 37C for 72 hours & colonies in 10 fields are recorded.
- 32. Plaque tooth pick Grade Colonies/ 10 fields. 1 None 2 < 8 3 8
- 33. Saliva/ tongue blade method. Test estimates the number of S. mutans in mixed stimulated saliva when cultured in MSB agar. Subjects chew paraffin for 1 min to displace plaque microorganisms. Subjects are given sterile tongue blade, which they rotate in mouth for 10 mins, so that both the sides are thoroughly inoculated by flora. Flora pressed on to MSB agar & incubated at 37 c for 48 hours.
- 34. Fosdick calcium dissolution test. Test measures mgs of powdered enamel dissolved in 4 hours by acid formed when patients saliva is mixed with glucose & powdered enamel. 25 ml of stimulated saliva is collected & part of it is analysed for calcium content. Rest of saliva is placed in tube with about 0.1 mg of powdered enamel. Tube is sealed & shaken for 4 hours at body temp, after which it is again analysed for calcium content.
- 35. Chewing of gum to stimulate the saliva produces sugar; if paraffin is used, a concentration of about 5% glucose is added. Amount of dissolution increases as the caries activity increases.
- 36. Dewar test. Similar to Fosdick test , only difference is that the final pH after 4 hours is measured instead of amount of calcium dissolved.
- 37. Uses for clinician Determine the need for caries control measures. Indicator of patient co – operation. Acts as an aid in timing of recall appointments. Aid in determining prognosis. Precautionary signal to orthodontist in placing bands.
- 38. Uses for research worker. As an aid in selecting patients for caries studies. To help in screening of potential therapeutic agents. Serve as an indicator of periods of exacerbation & remission.
- 39. Thank you