18 July 2025

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Polymerase chain reaction A molecular diagnostic tool in periodontology

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This review discusses the principles of polymerase chain reaction (PCR) and its application as a diagnostic tool in periodontology. The relevant MEDLINE and PubMed indexed journals were searched manually and electronically by typing PCR, applications of PCR, PCR in periodontics, polymorphism studies in periodontitis, and molecular techniques in periodontology. The searches were limited to articles in English language and the articles describing PCR process and its relation to periodontology were collected and used to prepare a concise review. PCR has now become a standard diagnostic and research tool in periodontology. Various studies reveal that its sensitivity and specificity allow it as a rapid, efficient method of detecting, identifying, and quantifying organism. Different immune and inflammatory markers can be identified at the mRNA expression level, and also the determination of genetic polymorphisms, thus providing the deeper insight into the mechanisms underlying the periodontal disease.

A clinical diagnosis of periodontal disease is made by measuring the loss of connective tissue attachment on the root surface (clinical attachment loss) and loss of alveolar bone (radiographic bone loss). But the clinical diagnosis does not indicate the cause, pathogenesis, clinical course, progress, and prognosis of the disease. In addition to the conventional examination, various diagnostic methods play a vital role in the confirmation of the clinical diagnosis.

The traditional culture methods have inherent advantages, but have shortcomings, including the need to preserve bacterial vitality, the inability to detect low numbers of microorganisms with a detection limit averaging 103–104 bacterial cells, labor intensiveness, need for experienced personnel, strict sampling, transport conditions, and a prolonged period of time before results. Other microbiological tests such as dark field microscopy are not able to detect the nonmotile periodontal pathogen, and immunodiagnostic methods like flow cytometry, immunofluorescence assay, etc., and enzymatic assays can lead to false positive results and cross-reactions.

The molecular biological techniques analyze deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein. Restriction fragment length polymorphism (RFLP) was the DNA profiling genetic technique that exploited variations in homologous DNA sequences; it was laborious, time-consuming, expensive, and needed large sample. The nucleic acid probe, a nucleic acid molecule artificially synthesized and labelled for detection of a specific organism has the limitation of cross-reactivity. Hybridization refers to the pairing of complementary DNA strands to produce double stranded nucleic acid and the checkerboard DNA-DNA hybridization technology used for epidemiological research, and ecologic studies require sophisticated laboratory equipment and expertise. Polymerase chain reaction (PCR) overcomes the above limitations and is capable of detecting even one copy of the searched DNA targets from clinical microbiologic samples.

The subgingival microbiota in patients with periodontitis is complex and the difference in plaque composition serves as the basis for the clinical application of microbiological techniques in the diagnosis and therapy control of progressive and refractory forms of periodontitis. The development of PCR has generated vast benefits in genetic analysis for the study of gene expression and diagnosis of genetic diseases. Genetic analysis using PCR for identification of susceptibility of an individual to periodontitis will help in the determination of the type and frequency of treatment. Studies based on PCR for the determination of mRNA expression of various immune and inflammatory markers are useful in understanding the pathogenesis of periodontitis.

The MEDLINE and PubMed databases were searched manually and electronically in English language by typing PCR, applications of PCR, PCR in Periodontics, Polymorphism studies in Periodontitis, and molecular techniques in periodontology. Out of 248 searched articles, 88 articles describing PCR process and its relation to periodontology were used to prepare a concise review. The aim of this review is to discuss the principles, advantages, applications, and limitations of PCR in the field of periodontology with their future perspectives.

Authors: Maheaswari, Rajendran; Kshirsagar, Jaishree Tukaram; Lavanya, Nallasivam

Source: https://journals.lww.com/