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An in-depth analysis of Gingival Crevicular Fluid (GCF), also known as sulcular fluid. the definition, formation, function, composition, and methods of collection of GCF. It also discusses the clinical significance of GCF and its use as a diagnostic tool for periodontal disease. various methods for estimating GCF amount and the problems associated with its collection.
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Introduction Gingival crevicular fluid (GCF), also known as sulcular fluid, is defined as physiologic fluid secreted in the gingival crevice that is classified as inflammatory exudate during disease or serum transudate during health. GCF secreted in minute amount in healthy state, which is increased in response to inflammation. Gingival crevice is a V-shaped space bounded by tooth from one side and epithelium lining the free margin of gingiva on the other side. Waerhaug (1950) studied pathologic transformation of gingival sulcus into periodontal pocket. In the same period, work of Brill et al. established the understanding the physiology of gingival crevicular fluid formation and its composition. Later, Loe et al. (1965) used gingival crevicular fluid as an indicator of periodontal disease. Brill and Krasse (1958) had first demonstrated the seepage of GCF. They introduced filter paper into the gingival sulci of dogs previously injected intramuscularly with fluorescein; within 3 minutes, the fluorescent material was recovered on the paper strips. This indicated the passage of fluid from the bloodstream through the tissues and exiting via the gingival sulcus. Later, other studies showed little or no fluid can be collected from the gingival crevice in health condition. Recently, it is agreed that GCF is secreted as transudate due to osmotic gradient in health and it changes into exudate upon in response to inflammation during periodontal disease. Formation of GCF Epithelial lining of the sulcus characterizes by permeability that allows traversing of the molecules through intercellular spaces. Previous studies showed that wide range of molecules could penetrate the epithelial barrier including albumin and endotoxin. Pashley et al. (1976) suggested a model that explains the flow of fluid into gingival crevice area. This model suggested that GCF production is controlled by the passage of fluid from capillaries into the tissues (capillary filtrate) which is removed by lymphatic system. However, when the role
of capillary fluid exceeds that of lymphatic uptake, the fluid accumulate as edema and leave the area as GCF (Fig 1). According to this model, the flow of GCF can be explained as following: A- In the absence of inflammation: In health state, there is a low vascular pressure and low permeability of basement membrane. Subsequently, this will reduce the flow of GCF associated with increased fluid uptake by lymphatics. B- During inflammation: Presence of dental biofilm leads to an increase in osmotic gradient, which is followed by increased leakage of proteins. This will cause increase in hydrostatic pressure and vascular permeability thereby exceeding the capacity of lymphatics to drain fluids leading to upregulation of GCF flow. i ii Figure 1. i) In healthy condition, the majority of interstitial fluid is drained by lymphatic system and only small amount leak into gingival crevice forming transudate. ii) During periodontal disease, the amount of leaked fluid from blood vessels is beyond the drainage capacity of lymphatics, leading to formation of inflammatory exudate.
1 - Absorbing paper strip Paper strips are available in standard sizes that can absorb volume of GCF ranging between 1.2-2 μl. Absorbing papers can be used in two ways a. Intra-crevicular method: the paper strip is placed superficially at the entrance of gingival crevice (Loe and Holm-Pederson technique) to minimize irritation to the sulcular epithelium. The other approach is to insert the paper strip gently within the gingival crevice until minimal resistance is felt (Brill’s technique). Brill’s method cause more irritation to the tissue and may stimulate oozing of the fluid (Fig 2). Typically, absorbing papers are inserted no more than 1– 2 mm into the sulcus/ pocket with gentle placement until mild resistance is felt, and held in place for 30 seconds. i ii Figure 2. i) Loe and Holm-Pederson technique, positioning of paper strip at gingival margin without penetrating gingival sulcus; (ii) Brill’s technique, positioning of paper strip into gingival sulcus-P3.
b. Extra-crevicular method: The paper strip is adapted on the gingiva & the hard tissue of the tooth in this region so the paper strip will absorb the seepage of GCF (Fig 3). Figure 3. Positioning of paper strip overlying the tooth, gingiva, and alveolar mucosa for obtaining GCF 2 - Crevicular washing The Gingival sulcus is perfused with an isotonic solution of fixed volume. Three methods of gingival washing are available: a- Instillation and re-aspiration of 10 μl of Hank’s balanced salt solution at the interdental papilla. It is repeated several times to allow thorough mixing of transport solution and GCF. The fluid collected represents a dilution of GCF that contains both cells and soluble constituents such as plasma proteins. b- Second method is more complicated which involves the construction of a customized acrylic stent that isolates the gingival tissue from the rest of the mouth. The tissues are irrigated with a saline solution, using a peristaltic pump and the diluted GCF is removed. The stent is made of hard acrylic plate covering the maxilla with soft borders and a groove following the gingival margin, connected to four collection tubes. This method lacks accuracy, technically demanding and limited to use for maxillary arch only. c- Third method is a modification that uses two injection needles fitted one within the other such that during sampling, the inner needle (or ejection) is at the bottom of the
2 - An electronic method has been devised for measuring the fluid collected on a “blotter” (Periopaper), employing an electronic transducer (Periotron). Periotron is an electronic instrument that measures the effect of wetness of filter paper strips on the capacitance between the ‘jaws’ of the device, between which the filter paper is placed after the sample has been collected. The wetness of the paper strip affects the flow of an electronic current and gives a digital readout (Fig 7). The readings obtained by Periotron can be converted into corresponding clinical conditions and scores recorded by gingival index (Table 2) Figure 7. Electronic device (Periotron) for measuring the amount of fluid collected on filter paper. Periotron reading Level of gingival inflammation Gingival index 0 - 20 Healthy 0 21 - 40 Mild 1 41 - 80 Moderate 2 81 - 200 Severe 3 Table 2. Translation of Periotron value into associated clinical conditions and gingival index 3 - Weighting the strip: pre-weighted strip is inserted into the gingival crevice & then determined the amount of fluid collected by weighting the sample. 4 - Isotope dilution method to measure extremely small amount of GCF present in a particular space at any given time.