Cross-cultural adaptation of the Brazilian version of the Dentine Hypersensitivity Experience Questionnaire (DHEQ-15).

The dentine hypersensitivity (DH) is able to impair the oral health related quality of life (OHRQoL). However, there isn't any specific validated questionnaire to be used in Brazil. The objective was to adapt and to validate the English version of the Dentine Hypersensitivity Experience Questionnaire (DHEQ-15) for use in Brazil. DHEQ-15 was cross-culturally adapted into the Brazilian-Portuguese language and then validated in a cross-sectional study with 100 participants recruited at a University clinic. Study sample comprised 2 groups: 100 individuals with DH, and 100 individuals without. The instrument was self-administered twice 7 to 10 days apart. The participants answered a global rating of oral health. The psychometric properties of the Brazilian version of DHEQ-15 were verified through internal consistency (Cronbach's α) and test-retest reliability (intraclass correlation coefficient - ICC), convergent (Spearman correlation) and discriminant (Mann-Whitney test) validity. The significance threshold was set at p<0.05. Sample comprised 69 men and 131 women, of mean age 30.4y. The Brazilian DHEQ-15 demonstrated very good internal consistency (α = 0.945). Test-retest reliability revealed excellent reproducibility (ICC = 0.959, p < 0.001). There was statistically significant correlation between the scores obtained on all DHEQ-15 domains and the global rating of oral health (p<0.001). Participants with DH scored significantly higher than those without DH (p<0.001). This study provides evidence supporting the cross-cultural validity of the Brazilian version of DHEQ-15 for use in Brazil.

Molecular basis of dental sensitivity: The odontoblasts are multisensory cells and express multifunctional ion channels.

Odontoblasts are the dental pulp cells responsible for the formation of dentin. In addition, accumulating data strongly suggest that they can also function as sensory cells that mediate the early steps of mechanical, thermic, and chemical dental sensitivity. This assumption is based on the expression of different families of ion channels involved in various modalities of sensitivity and the release of putative neurotransmitters in response to odontoblast stimulation which are able to act on pulp sensory nerve fibers. This review updates the current knowledge on the expression of transient-potential receptor ion channels and acid-sensing ion channels in odontoblasts, nerve fibers innervating them and trigeminal sensory neurons, as well as in pulp cells. Moreover, the innervation of the odontoblasts and the interrelationship been odontoblasts and nerve fibers mediated by neurotransmitters was also revisited. These data might provide the basis for novel therapeutic approaches for the treatment of dentin sensibility and/or dental pain.

Cross-cultural adaptation of the Brazilian version of the Dentine Hypersensitivity Experience Questionnaire (DHEQ-15)

Abstract The dentine hypersensitivity (DH) is able to impair the oral health related quality of life (OHRQoL). However, there isn't any specific validated questionnaire to be used in Brazil. The objective was to adapt and to validate the English version of the Dentine Hypersensitivity Experience Questionnaire (DHEQ-15) for use in Brazil. DHEQ-15 was cross-culturally adapted into the Brazilian-Portuguese language and then validated in a cross-sectional study with 100 participants recruited at a University clinic. Study sample comprised 2 groups: 100 individuals with DH, and 100 individuals without. The instrument was self-administered twice 7 to 10 days apart. The participants answered a global rating of oral health. The psychometric properties of the Brazilian version of DHEQ-15 were verified through internal consistency (Cronbach's α) and test-retest reliability (intraclass correlation coefficient - ICC), convergent (Spearman correlation) and discriminant (Mann-Whitney test) validity. The significance threshold was set at p<0.05. Sample comprised 69 men and 131 women, of mean age 30.4y. The Brazilian DHEQ-15 demonstrated very good internal consistency (α = 0.945). Test-retest reliability revealed excellent reproducibility (ICC = 0.959, p < 0.001). There was statistically significant correlation between the scores obtained on all DHEQ-15 domains and the global rating of oral health (p<0.001). Participants with DH scored significantly higher than those without DH (p<0.001). This study provides evidence supporting the cross-cultural validity of the Brazilian version of DHEQ-15 for use in Brazil.

Age-related morphological, histological and functional changes in teeth.

Throughout lifetime, the teeth are continuously exposed to numerous chemical and physical impacts, which cause the wear of the dental hard tissues, gingival recession and other oral changes with sometimes subsequent problems. Age-related wear of tooth surfaces reduces the dental enamel thickness and exposes deeper layers of enamel, which have different physical and chemical properties than the surface enamel. Gingival recession is the main causal factor of root caries and dentine hypersensitivity. Age-related changes in dentine include the formation of secondary dentine and the reduction in tubular lumen diameter (dentine sclerosis), which lead to a reduction in the volume of the pulp chamber. In addition to the reduction in the volume of pulp chamber, changes to the dental pulp also include dental pulp calcifications. The age-related physiological changes to the teeth should be carefully distinguished from pathological changes, especially when they induce pain or a negative impact on the oral health-related quality of life (OHRQoL) of the older individuals. Therefore, regular oral examinations coupled with early preventive measures should aim at maintaining oral health until old age.

Stress and its role in the dentin hypersensitivity in rats.

INTRODUCTION: The perception of pain varies individually. Chronic stress leads to analgesia. The use of animal chronic mild stress model to mimic human condition was previously developed and now applied in the evaluation of pain perception in rats with dentin hypersensitivity (DH). AIMS: Using DH model induced by dentin erosion (DE) mediated by acidic solution, the present study aimed the evaluation of the interaction of chronic stress and pain induced by DH in rats with DE. METHODS: DH was induced by ad libitum 30-day intake of acidic solution. Stress was induced by the New York subway model. Body weight was weekly taken, during treatment. Groups WO (water, no stress), WS (water and stress), EO (acidic solution, no stress) and ES (acidic solution, stress) were submitted to treatments. RESULTS: After 30 days, all groups were submitted to DH test assessed by cold water stimuli in the labial surface of molars, for 5s, and the rats responses were scored as grades 0, 0.5, 1, 2, or 3. After euthanasia, blood was taken to obtain the levels of corticosterone, stomachs were observed in fresh preparations, kidneys and livers were submitted to histological evaluation. Open field model supported stress evaluation, as did corticosterone analysis. Stressed animals showed significant increase in pain perception and a decrease in locomotion frequency, tending to be more frequent in the periphery of the arena, corroborating stressed behavior and the need of protection as a pain relief. Corticosterone levels were increased in the stressed rats with dentin erosion and also corroborate present findings. Finally, reduction in weight gain was impaired in stressed group with dentin erosion. CONCLUSION: The animal model enabled the evaluation of how chronic mild stress interfered in DH pain perception.

Factors affecting intra-oral pH - a review.

One of the greatest challenges to modern dentistry is the progressive destruction of tooth material due to chemical erosion. Dental erosion is the loss of dental hard tissue, without the action of bacteria, in which demineralisation of enamel and dentine results due to a decrease in intra-oral pH. The aim of this review was to appraise the scientific literature on the factors that can affect intra-oral pH. The review will examine (i) the protective role of human saliva, in terms of its mineral composition, flow rates and buffering systems and (ii) sources of in-mouth acids such as extrinsic acids, which are derived from the diet and environment, as well as intrinsic acids, which are related to disorders of the gastro-oesophageal tract. This review may assist clinicians to identify the risk factors for tooth wear and to recommend adequate preventive measures to patients.

Effect of cavity depth on dentine sensitivity in man.

OBJECTIVE: To determine if dentine at the enamel-dentine junction (EDJ) in man is more sensitive to hydrostatic pressure stimuli then deeper dentine. DESIGN: Cavities (1mm diam.) were cut at the tips of the buccal and lingual cusps of 8 premolars in 3 subjects (ages: 22-25 years). Both cavities were initially deepened to expose the EDJ then one (the test cavity) was deepened in steps of 0.5mm to a maximum of 2.0 mm below the EDJ. The cavities were tested at each stage, before and after etching, with 5s, hydrostatic pressure stimuli between 400 mm above, and 400 mm below atmospheric. The intensity of any pain produced was recorded on a VAS scale and electrodes were placed in both cavities in an attempt to monitor any action potentials evoked in intradental nerves. RESULTS: In all the teeth, the intensity of the pain produced by a stimulus tended to increase as the cavity was deepened, as did the number of action potentials recorded (in 6 of the 8 teeth). The responses were greater from etched than unetched dentine, and negative pressures evoked greater responses than the corresponding positive pressures. CONCLUSION: There was no evidence that dentine close to the EDJ was more sensitive to hydrostatic pressure stimuli than deeper dentine. It may however be more sensitive to mechanical stimuli as it is more compliant.

Quantitative sensory testing of dentinal sensitivity in healthy humans.

OBJECTIVE: The study was to provide information on quantitative sensory testing (QST) of normal teeth to establish a sensory profile and investigate the possible gender and regional differences. MATERIALS AND METHODS: A modified QST protocol was applied on both left and right upper-jaw incisors and pre-molar sof 14 healthy men and 14 age-matched healthy women (18-25 years). Mechanical stimulus sensitivity (MSS), cold detection threshold (CDT), cold pain threshold (CPT), warm detection threshold (WDT), heat pain threshold (HPT), electrical detection threshold (EDT) and electrical pain threshold (EPT) were determined from the four teeth (labial side of incisor and buccal side of the first premolar). The QST parameters were analysed by ANOVA. RESULTS: The applied mechanical or thermal stimuli did not evoke any pain sensation. A normal tooth did not seem to be able to distinguish between the warm or cold stimuli applied. No significant differences were found between genders (p > 0.099) or teeth (p > 0.053) regarding mechanical and thermal stimuli. The EDT and EPT were significantly higher in the pre-molar compared with incisor (p < 0.002) without gender differences (p > 0.573). CONCLUSION: The established methods and results provided important information on diagnosis and treatment evaluation of dentinal hypersensitivity.

Evaluation of dentin tubule occlusion after laser irradiation and desensitizing agent application.

PURPOSE: To evaluate the effects of lasers (Nd:YAG and Er:YAG) and of topical desensitizing agents on dentin tubule occlusion by measuring real-time dentin fluid flow (DFF). METHODS: 32 molars were prepared with V-shape cavity at the cervical area, acid-etched, water rinsed, blotted dry, and treated with (1) Nd:YAG laser; (2) Er:YAG laser; (3) SuperSeal, a desensitizing agent; (4) ClinproXT, a resin-modified glass-ionomer (RMGI) varnish (n = 8 each). A real-time fluid flow measuring instrument (nano-Flow) was used to measure the DFF throughout the procedures. The DFF rates before and after the treatment were compared. Moreover, the surface topography of dentin tubules after each desensitizing method was examined using SEM. RESULTS: DFF varied among the groups. The DFF rate was significantly reduced after laser irradiation/application of the desensitizing agents (P < 0.05). ClinproXT showed the greatest reduction of DFF rate (71.9%), followed by the SuperSeal (34.8%) and laser groups (P< 0.05). However, there was no significant difference between the Nd:YAG (24.1%) and Er:YAG (20.6%) groups (P > 0.05). In SEM images, narrowed dentin tubules were observed in both lased groups and SuperSeal group. In the ClinproXT group, the occluded dentin tubules by the RMGI covering were observed.

Assessment of Pain Intensity in Patients with Dentin Hypersensitivity After Application of Prophylaxis Paste Based on Calcium Sodium Phosphosilicate Formula.

BACKGROUND: One of many functions of the pulp-dentin complex is sensory function. Acute, situated, receding pain after the cessation of the stimulus action is called dentin pain. Dentin hypersensitivity has been described as one of the most painful and least successfully treated chronic ailments of teeth. The aim of this research was the clinical evaluation of the effectiveness of professional polishing paste containing calcium sodium phosphosilicate formula (NovaMin) in eliminating dentin hypersensitivity after a single application. MATERIAL AND METHODS: The study comprised 92 teeth with dentin hypersensitivity diagnosed on the basis of history and clinical examination. The pain reaction of exposed dentine was induced by tactile and dehydrating stimuli, asking patients to assess the severity of pain on the VAS scale. Clinical trial and survey were carried out twice: before and 1 week after the application of the polishing paste. RESULTS: After the application of the examined paste, the percentage of teeth reacting with a severe pain to the touch of the probe decreased from 16.3% to 4.3%, and with a moderate pain from 42.4% to 12%. Examination after applying dehydrating stimulus a week after carrying out the application showed a decrease in the proportion of teeth with strong pain from 28.3% to 0% and moderate pain from 38% to 15.2%. The lack of pain increased from 12% to about 50%. CONCLUSIONS: The use of prophylactic professional paste with NovaMin formula in in-office procedure provides the reduction of dentin hypersensitivity noticeable by 1 week after application.

Different Brain Responses to Pain and Its Expectation in the Dental Chair.

A dental appointment commonly prompts fear of a painful experience, yet we have never fully understood how our brains react to the expectation of imminent tooth pain once in a dental chair. In our study, 21 patients with hypersensitive teeth were tested using nonpainful and painful stimuli in a clinical setting. Subjects were tested in a dental chair using functional near-infrared spectroscopy to measure cortical activity during a stepwise cold stimulation of a hypersensitive tooth, as well as nonpainful control stimulation on the same tooth. Patients' sensory-discriminative and emotional-cognitive cortical regions were studied through the transition of a neutral to a painful stimulation. In the putative somatosensory cortex contralateral to the stimulus, 2 well-defined hemodynamic peaks were detected in the homuncular orofacial region: the first peak during the nonpainful phase and a second peak after the pain threshold was reached. Moreover, in the upper-left and lower-right prefrontal cortices, there was a significant active hemodynamic response in only the first phase, before the pain. Subsequently, the same prefrontal cortical areas deactivated after a painful experience had been reached. Our study indicates for the first time that pain perception and expectation elicit different hemodynamic cortical responses in a dental clinical setting.

Comparative evaluation of the effectiveness of desensitizing agents in dentine tubule occlusion using scanning electron microscopy.

BACKGROUND: Dentine hypersensitivity (DH) occurs on exposed dentine and is dependent on the patency of dentinal tubules. This study compared the effectiveness of red propolis extract (RPE), calcium sodium phosphosilicate (Novamin) and arginine-calcium carbonate (ACC) in occluding dentine tubules. METHODS: Eighty dentine discs from extracted human molars were randomly divided into four groups (n=20): Group 1--RPE; Group 2--Novamin; Group 3--ACC; Group 4--saline. The discs were etched with 37.5% phosphoric acid and treated with the test agents. Ten treated discs from each group were then exposed to 6% citric acid challenge. The extent of tubule occlusion was assessed using scanning electron microscopy (SEM). Three blinded assessors scored each SEM image on the degree of tubule occlusion. Differences in occlusion were tested using ANOVA and Tukey adjustment. RESULTS: Discs treated with ACC demonstrated more tubule occlusion, followed by RPE and Novamin, and were greater in statistical significance when compared to discs treated with saline. Following acid challenge, RPE treated discs maintained more occlusion, followed by ACC and Novamin. CONCLUSIONS: All three agents demonstrated tubule occlusion. Although ACC showed more occlusion following treatment, RPE demonstrated a higher degree of occlusion following acid challenge.

Dentin and pulp sense cold stimulus.

Dentin hypersensitivity is a common symptom, and recent convergent evidences have reported transient receptor potential (TRP) channels in odontoblasts act as mechanical and thermal molecular sensor, which detect stimulation applied on the exposed dentin surface, to drive multiple odontoblastic cellular functions, such as sensory transduction and/or dentin formation. In the present study, we confirmed expression of TRP melastatin subfamily member-8 (TRPM8) channels in primary cultured cells derived from human dental pulp cells (HPCs) and mouse odontoblast-lineage cells (OLCs) as well as in dentin matrix protein-1 (DMP-1) and dentin sialoprotein (DSP) positive acutely isolated rat odontoblasts from dental pulp tissue slice culture by immunohistochemical analyses. In addition, we detected TRPM8 channel expression on HPCs and OLCs by RT-PCR and Western blotting analyses. These results indicated that both odontoblasts and dental pulp cells express TRPM8 channels in rat, mouse and human, and therefore we hypothesize they may contribute as cold sensor in tooth.

Dentine hypersensitivity.

Dentine hypersensitivity is a common oral pain condition affecting many individuals. The aetiology is multifactorial; however, over recent years the importance of erosion has become more evident. For dentine hypersensitivity to occur, the lesion must first be localised on the tooth surface and then initiated to exposed dentine tubules which are patent to the pulp. The short, sharp pain symptom is thought to be derived from the hydrodynamic pain theory and, although transient, is arresting, affecting quality of life. This episodic pain condition is likely to become a more frequent dental complaint in the future due to the increase in longevity of the dentition and the rise in tooth wear, particularly amongst young adults. Many efficacious treatment regimens are now available, in particular a number of over-the-counter home use products. The basic principles of treatment are altering fluid flow in the dentinal tubules with tubule occlusion or modifying or chemically blocking the pulpal nerve.

Clinical and scanning electron microscopy evaluation of the Er,Cr:YSGG laser therapy for treating dentine hypersensitivity: short-term, randomised, controlled study.

Er,Cr:YSGG laser is a rising treatment option for dentine hypersensitivity (DH). However, there is no data available concerning the scanning electron microscope (SEM) evaluation of the clinical application of Er,Cr:YSGG laser in the treatment of DH. The aim of this study was to evaluate and compare the desensitising and tubule occlusion effects of Er,Cr:YSGG laser with different power settings. Twenty patients (60 teeth) participated in this study. For each patient, teeth were randomised to 3 groups. In groups 1 and 2, patients were treated with Er,Cr:YSGG laser at 0.25 and 0.5 W, respectively. In control group, same laser was applied without laser emission. DH was assessed for all groups with a visual analogue scale (VAS). When compared with the baseline data and control group, in both active treatment groups laser irradiation provided a desensitising effect immediately after treatment (P < 0.001). In group 2, VAS scores were significantly lower than group 1. The tubule diameters in the both laser groups were significantly smaller than the control group (P < 0.01). When group 1 compared with group 2, group 2 showed significantly smaller tubule diameters (P < 0.001). Both 0.25 and 0.5 W laser irradiation were effective for the treatment of DH; however, 0.5 W laser irradiation showed best results for the decrease in VAS scores. The SEM findings of the reduction in number/patency of dentine tubules seem to be related to the clinical findings, which were associated with improvement in treatment efficacy.

Dentin hypersensitivity induces anxiety and increases corticosterone serum levels in rats.

AIMS: Investigate the relationships between experimentally induced dentin hypersensitivity (DH) with behavioral, endocrine and dentin erosion data. METHODS: Male Wistar rats divided into four groups, two controls and two experimental, received tap water or isotonic solution (Gatorade®, lemon, pH2.7) for 30 or 45 days. The DH test was performed by a cold water stimulus on molars. A score (0-3) was given to the rats' pain response. Anxiety was evaluated by the elevated plus maze model and by serum corticosterone levels. The dentin erosion was observed by scanning electron microscopy (SEM). Anatomopathological studies were performed on the stomach, adrenal, kidney, and liver. RESULTS: Relative to control groups, experimental rats showed: 1) increased hypersensitivity scores (control group, 0; experimental groups, 2 (limits 0.5-3) on the 30th day and 2 (limits 1-3) on the 45th day); 2) reduced percentage of time and entries in the open arms and in serum corticosterone levels; 3) totally exposed dentinal tubules on the 30th day in SEM analysis of the teeth; and 4) no alterations in the anatomopathological and histological evaluations. CONCLUSIONS: The treatment with isotonic solution for 30 days was able to induce DH after erosive challenge and severe DH was observed after isotonic solution treatment for 45 days. The pain induced by cold stimuli was consistent with the grade of DH. The close relationships between dental erosion, response to pain, serum levels of corticosterone and the EPM behavior responses reveal the effects of DH at several levels.

Evaluation of potassium binoxalate gel and Nd:YAG laser in the management of dentinal hypersensitivity: a split-mouth clinical and ESEM study.

Dentinal hypersensitivity is one of the oldest recorded complaints of discomfort to mankind and yet there appears to be no permanent treatment for this clinical condition. This study was designed to evaluate the clinical efficacy of potassium binoxalate gel and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser on dentin hypersensitivity for a period of 9 months. Eighty teeth (20 subjects, 25-55 years old, M = F) were evaluated in a split-mouth design to receive potassium binoxalate (group A, 40 teeth) and Nd:YAG (group B, 40 teeth: 1 W, 10 Hz, and 60 s, irradiated twice). The diameter of output beam was about 300 µm with a distance of 2 mm between laser fiber or tip and tooth surface. The clinical efficacy was evaluated by air-blast test and cold-water test using visual analog scale. Electron microscopy photomicrographs were taken to confirm the results. Analysis was done at baseline; immediately post-treatment; and at 3, 6, 9 months post-treatment. Student's paired and unpaired T tests were used to evaluate the statistical analysis. Both treatment modalities were effective in reducing dentine hypersensitivity. However, Nd:YAG laser was better when intragroup comparison was made at 9 months post-treatment. Nd:YAG lasers is better in long-term treatment (up to 9 months) owing to the melting of dentinal tubules. However, due to depth of penetration of microcrystals, gel was better when ease of the procedure is considered. Nevertheless, both treatment modalities resulted in recurrence. Hence, further studies are needed to discover an agent, which can be considered as a "gold standard".

Dentine hypersensitivity--guidelines for the management of a common oral health problem.

UNLABELLED: Dentine hypersensitivity (DHS) remains a worldwide under-reported and under-managed problem, despite making some dental treatments more stressful than necessary and having a negative impact on the patient's quality of life. This article is designed to build dental professionals' confidence and remove any confusion regarding the diagnosis, prevention and treatment of sensitive teeth caused by dentine hypersensitivity in those patients known to be at risk. There is a need for simple guidelines, which can be readily applied in general practice. However, it is also obvious that one strategy cannot suit all patients. This review describes a DHS management scheme for dental professionals that is linked to management strategies targeted at three different groups of patient. These patient groups are: 1) patients with gingival recession; 2) treatment patients with toothwear lesions; and 3) patients with periodontal disease and those receiving periodontal treatment. The authors also acknowledge the role of industry as well as dental professionals in a continuing role in educating the public on the topic of sensitive teeth. It is therefore important that educational activities and materials for both dental professionals and consumers use common terminology in order to reduce the possibility for confusion. CLINICAL RELEVANCE: This review article provides practical, evidence-based guidance on the management of dentine hypersensitivity for dental professionals covering diagnosis, prevention and treatment. Sensitivity associated with gingival recession, toothwear and periodontal disease and periodontal treatment are specifically addressed in the article.

Cellular and molecular mechanisms of dental nociception.

Due, in part, to the unique structure of the tooth, dental pain is initiated via distinct mechanisms. Here we review recent advances in our understanding of inflammatory tooth pain and discuss 3 hypotheses proposed to explain dentinal hypersensitivity: The first hypothesis, supported by functional expression of temperature-sensitive transient receptor potential channels, emphasizes the direct transduction of noxious temperatures by dental primary afferent neurons. The second hypothesis, known as hydrodynamic theory, attributes dental pain to fluid movement within dentinal tubules, and we discuss several candidate cellular mechanical transducers for the detection of fluid movement. The third hypothesis focuses on the potential sensory function of odontoblasts in the detection of thermal or mechanical stimuli, and we discuss the accumulating evidence that supports their excitability. We also briefly update on a novel strategy for local nociceptive anesthesia via nociceptive transducer molecules in dental primary afferents with the potential to specifically silence pain fibers during dental treatment. Further understanding of the molecular mechanisms of dental pain would greatly enhance the development of therapeutics that target dental pain.

In vitro evaluation of dentinal hydraulic conductance and tubule sealing by a novel calcium-phosphate desensitizer.

In the current trend of materials used for dentin hypersensitivity treatment, calcium-phosphate-containing desensitizers are expected to have advantages in oral environment. A newly formulated desensitizer containing tetracalcium phosphate and dicalcium phosphate anhydrous (CPD-100) was evaluated in comparison to oxalate containing desensitizer (SS) regarding permeability reduction (PR%) by measuring hydraulic conductance on the etched dentin discs in vitro. CPD-100 exhibited mean PR% of 91%, which significantly increased to 98% after immersion in artificial saliva (AS) for 4 weeks (p < 0.001), while SS showed a significant decrease from 99% to 93% (p < 0.01). SEM observation showed newly formed crystallites on CPD-100 treated dentin, which did not exist in SS treated dentin after AS immersion, suggesting that calcium oxalate inhibited formation of new calcium-phosphate minerals. Five-minute acid challenge did not significantly affect PR% of dentin treated by any of the desensitizers. The energy dispersive X-ray spectroscopy (EDS) analysis indicated that the formed layer of CPD-100 were minerals with similar Ca/P ratio to hydroxyapatite. In conclusion, the newly developed calcium-phosphate desensitizer has the potential to exhibit long-term stability in the oral environment, owing to its chemical properties that promote the crystal growth in salivary fluid.