Advanced Diagnostic Techniques
- Conventionally, diagnostic aids have always been methods used to monitor either the etiologic factors of periodontal disease or the metabolic changes caused by them, or the anatomic consequences that result from prolonged progression.
- Diagnostic aids can therefore be classified into these three types, as more or less every diagnostic aid falls into one of these broad categories.
- Advanced diagnostic aids have not necessarily found new parameters to evaluate, as much as they have improvised upon conventionally available methods to make diagnosis more accurate, quick, convenient, and specific.
Read And Learn More: Periodontology Important Question And Answers
- It is, after all, the existing pocket probe that is the forerunner of many new, modified, often computerized probes invading the market today.
- Diagnostic aids are usually assessed on the basis of their specificity, sensitivity, and predictive value.
- Specificity refers to the ability of a test or observation to clearly differentiate one disease from another.
- On the other hand, sensitivity refers to the ability of a test or observation to detect the disease whenever it is present.
- While specific tests may allow for false—negative results, sensitive tests may not allow for false—negative results.
- Vice-versa false positive results may be seen with sensitive tests but false-positive results may not be allowed for in specific tests.
- Predictive value then refers to the probability that the test result, i.e. the proportion of true positive results and true negative results combined, agrees with the disease status.
Question 1. Classify probes. Write in detail about different generations of probes.
Answer:
Periodontal probing is a physical means to determine the extent of periodontal disease. Probes have been classified into.
- First Generation Probes
- The traditional periodontal probe is an instrument with a tapered, rod-like blade that has a blunt and rounded tip. Probing depths of more than 3 mm are considered pathological.
- The technique of probing involves inserting the probe parallel to the long axis of the teeth and walking the probe circumferentially around six sites.
- The probing depth may differ at a given site as it is influenced by the penetration of a probe which in turn is influenced by: the size and shape of the probe tip, the amount of pressure applied by the clinician, the nature of the tissue, angulation of probe and the morphology of the crown and root of the tooth.
- The greater the probing force greater is the probing depth measured. When the clinician applies force on the tissue, the tissue exerts an opposite and equal pressure to the probe, and displacement of the probe into the tissue will increase.
- The probe has greater penetration of the tissue with increased pressure on the probe, and the resistance varied depending on tissue characteristics, morphology, and or tissue inflammation.
- Probing depth increases with inflammation and decreases in the absence of inflammation.
- The pressure exerted on the probe is directly proportional to the force on the probe and inversely proportional to the area at the probe tip.
- With a round probe, a change in tip diameter has a greater effect on pressure than does a similar change in the force. An increase in probing force will increase the pressure by a proportional amount.
- The world health organization proposed a probing tip with a hemispheric shape (less discomfort) and a diameter of 0.5 mm.
- A round tip with a diameter of 0.5 mm is indicated as forces applied is distributed over a wider area. Wider diameter probes may not enter the pocket.
- Smaller diameter tip may result in greater force being applied. Force of 20 grams (0. 20 N) should used with probe tip diameter of 0.6–0.7 mm to obtain pressure that would measure the new sulcus depth and not penetrate the long junctional epithelium following treatment.
- The principal problem being probing force, pressure-sensitive probes have been a part of recent developments in this field.
- The Second Generation (Constant Force) Probes
- These are probes that control force application during measurement. It is similar to first-generation probes with a spring or electric cut-out when the appropriate force is reached.
- For example, Alabama, and Toronto probe.
- The Third Generation Probes (Automated Probes)
- These include those that have controlled force application, automated measurement, and computerized data capture.
- For example, Fluoride probe.
- In a National Institute of Dental Research Workshop on quantitative evaluation of periodontal diseases by physical measurement techniques, the following criteria were laid down for the development of advanced probing systems:
- A precision of 0.1 mm
- A range of 10 mm
- Constant probing force
- Non-invasive, light-weight, comfortable to use the instrument
- Ability to access all locations around teeth
- A guidance system to ensure probe angulation
- Complete sterilization of all portions entering the mouth
- No biohazard from material or electric shock
- Digital output.
- Fourth Generation Probes
- They can record sequential probing positions along the gingival sulcus.
- For example, Jeffoat probe.
- Fifth Generation Probes: These are envisaged as non-invasive three-dimensional probes that use an ultrasound to determine probing depth.
Question 2. Write in detail about the advanced microbial diagnostic techniques.
Answer:
Dark-field or Phase Contrast Microscopy
- This technique has been suggested as an alternative to microbial culture methods on the basis of its ability to assess motile bacteria and spirochetes.
- The use of this technique as a diagnostic test of destructive periodontal diseases is limited.
Immunologic Assays
- These methods use polyclonal antisera or monoclonal antibodies that are specific for bacterial antigens or microbial virulence factors and therefore react only with the target bacterial species and exclude the rest of the bacteria in a given plaque sample.
- Some of the assays that are used as aids in periodontics today are:
Immunofluorescence Microscopy
- There are mainly two types of this technique: The direct type and the indirect type.
- In the direct technique, the antiserum to a micro-organism is conjugated to fluorescein.
- Then the conjugate is incubated along with a microbial sample and then washed off If an antigen-antibody reaction occurs, the organism can be seen by its florescent outline when observed in a florescence microscope.
- In the indirect technique, antiserum and microbial sample are incubated and then a conjugate of a florescent dye and an antiserum to the fist antiserum are incubated with the sample and then washed off.
- Latex Agglutination: This technique is based on the binding of protein to latex. Latex beads are coated with microbial species—specific antibodies and when this comes in contact with the sample antigen, agglutination occurs, which usually becomes obvious in 3–5 minutes.
- Flow Cytometry
- Used for rapid identification of oral bacteria. Bacteria from a patient plaque sample is labeled with a species—specific antibody and a secondary antibody that is coated with fluorescein.
- The complex is then introduced into a flow cytometer which has a laser and is able to detect fluorescence scattered from the cells.
- Enzyme-linked immunosorbent Assay (ELISA)
- The ELISA uses an enzymatically derived color reaction to detect antigens. Sample antigens are added to wells coated with specific antibodies to produce an antigen-antibody complex.
- This complex is labeled with immunoglobulins conjugated to either alkaline phosphatase or horseradish peroxidase.
- To this a chromogen is added which gives color to the solution The intensity of color indicates the concentration of the antigen and can be read photometrically for quantification.
Enzymatic Methods of Bacterial Identification
- Some species like B. forsythias, P. gingivalis, Treponema denticola, and Capnocytophaga species have a common trypsin-like enzyme.
- The activity of this enzyme can be measured with the hydrolysis of a colorless substrate N-benzoyl-DL-arginine-2-naphthylamide (BANA).
- When this substrate is hydrolyzed it releases the chromophore beta-naphthylamide which turns orange-red when a drop of fast garnet is added to the solution.
DNA Probes (Nucleic Acid Prob)
- This test utilizes plaque DNA samples that bind to complementary synthesised strands of DNA or RNA of specifi pathogens.
- The binding can then be detected through various secondary evaluators.
- DNA probes have been developed for A. actinomycetemcomitans, P. gingivalis and P. intermedia and these are now commercially available.
- Checker board-checker board DNA are available that detects a number of periodontal pathogens simultaneously.
Polymerization Chain Reaction (PCR)
- PCR used primers that are sequences of DNA that are specific to periodontal pathogens such as A. actinomycetemcomitans and P. gingivalis.
- This way even minute quantities of bacterial presence can be detected. Several innovations such as multiplex PCR, nested PCR, real-time PCR have been made available.
Diagnostic Aids-Host Response
- Products and mediators of inflammation. These include prostaglandin E2, cytokines, and antibacterial antibodies.
- Pro-inflammatory cytokines- interleukin 1β and tumor necrosis factor have been show to cause bone resorption.
- Host-derived enzymes such as aspartate aminotransferase, neutral protease, collagenase, lactate dehydrogenase, and alkaline phosphatase have been tried as markers of periodontal disease.
- Several of these have been shown to be elevated in GCF of patients with failing implants too.
- Tissue breakdown products such as glycosaminoglycans, fibronectin, type I collagen proteins, osteocalcin, osteopontin may prove to help in identifying disease sites.
Conclusion
- Although there have been several advances in diagnosis, sensitivity and specificity remain less than 100%.
- There is need for the development of rapid chair-side evaluation methods that will deliver personalized information about the extent and progression of periodontal disease and its response
to therapy.
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