Blood-flow mapping of oral tissues by laser Doppler flowmetry

Evaluation of perfusion parameters of gingival inflammation using laser Doppler flowmetry and tissue spectrophotometry- a prospective comparative clinical study

BACKGROUND

The aim of this study was to determine the values of different perfusion parameters- such as oxygen saturation, the relative amount of hemoglobin, and blood flow- in healthy subjects compared to patients with gingivitis as a non-invasive measurement method.

METHODS

A total of 114 subjects were enrolled in this study and separated into subjects with gingivitis (50) and without gingivitis (64) based on clinical examination. Gingival perfusion was measured at 22 points in the maxilla and mandible using laser Doppler flowmetry and tissue spectrophotometry (LDF-TS) with the "oxygen to see" device. All patients underwent measurement of gingival perfusion, followed by the clinical evaluation (measurement of probing depths, evaluation of bleeding on probing, plaque level, and biotype). Perfusion parameters were compared between the groups, associations between the non-invasive and clinical measurements were analyzed, and theoretical optimal cut-off values for predicting gingivitis were calculated with receiver operating characteristics.

RESULTS

The mean oxygen saturation, mean relative amount of hemoglobin, and mean blood flow all significantly differed between the groups with and without gingivitis (p = 0.005, p < 0.001, and p < 0.001, respectively). The cut-off value for predicting gingivitis was > 40 AU (p < 0.001; sensitivity 0.90, specificity 0.67).

CONCLUSIONS

As a non-invasive method, LDF-TS can help determine gingival hyperemia. Flow values above 40 AU indicate a higher risk of hyperemia, which can be associated with inflammation. The LDF-TS method can be used for the objective evaluation of perfusion parameters during routine examinations and can signal the progression of hyperperfusion before any change in clinical parameters is observed.

TRIAL REGISTRATION

All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the institutional Clinical Research Ethics Committee (Ethik-Kommission der Medizinischen Fakultät der RWTH Aachen, Decision Number 286/20) and retrospectively registered by the German Clinical Trials Register (File Number DRKS00024048, registered on the 15th of October 2021).

Gingival blood flow before, during, and after clenching, measured by laser Doppler blood flowmeter: A pilot study

INTRODUCTION

This study aimed to investigate the effects of the strong occlusal force on the hemodynamics of gingival microcirculation.

METHODS

Eleven adult volunteers with healthy periodontium and normal occlusion participated in this study. Using a noncontact laser Doppler flowmeter placed at the attached gingiva and the interdental papilla of the maxillary first premolar, changes in gingival blood flow (GBF) were examined during and after clenching.

RESULTS

When the strong occlusal pressure was applied on the maxillary first premolar by clenching, GBF in the attached gingiva on the buccal side decreased significantly compared with the resting GBF, with medians of 2.3 mL/min/100 g and 5.4 mL/min/100 g, respectively (P <0.05). After the release of the maximum clenching, GBF recovered immediately and transiently increased to a median of 2.4 mL/min/100 g, showing a significant difference to the resting GBF (P <0.05). In contrast, in the interdental papilla, no significant change in GBF was found by clenching.

CONCLUSIONS

Ischemia of the buccal attached gingiva associated with strong clenching may be due to compression of the vascular network of the periodontal membrane. Through reactive hyperemia resulting from the release of clenching, it is possible not only that blood flow will be restored to the tissue but that the tissue itself may be damaged by the reperfusion. During active orthodontic treatment, it is suggested that occlusal management to prevent occlusal trauma is important to avoid detrimental effects on periodontal tissues.

Effect of physical stimulation (gingival massage) on age-related changes in gingival microcirculation

The decline in circulatory function with aging may be alleviated by a combination of gingival massage (physical stimulation) and mechanical cleaning. Several studies have reported the systemic effect of physical stimulation on various parts of the body, including its therapeutic effect on pain in the neck and shoulders that becomes evident with age, and improvement in blood circulation. In contrast, few studies have reported on the changes in gingival microcirculation induced by gingival massage, while no previous study has evaluated the effect of gingival microcirculation on age-related changes in the hemodynamics of the oral cavity. This study aimed to investigate how gingival massage affects age-related changes in gingival microcirculation. Male Wistar rats (7-week, 6-month and 1-year old) were prepared for a gingival massage group and a control group. Mechanical stimulation was applied on the maxillary molar gingiva for 5 seconds twice a week for 4 weeks. Subsequently, gingival reactive hyperemia was measured using a laser Doppler flowmeter. In addition, morphological analyses were also performed by hematoxylin and eosin and Indian ink staining and a vascular resin cast model. Base Flow, maximum response (Peak), and time required for the maximum response to halve (T1/2) were reduced in 1-year-old rats compared with the other age groups. In the mechanical stimulated group, T1/2 was increased in 7-week, 6-month, and 1-year-old rats, and total blood flow (Mass) was increased in 6-month and 1-year-old rats. In addition, clear blood vessel networks and loop-like revascularization were only observed in the mechanical stimulated group. Changes in age-related decline in gingival microcirculatory function and vascular construction were reported in this study, and the results suggested that gingival massage activates both the functional and morphological aspects of gingival microcirculation and may be effective for maintaining oral health.

Blood Flow Alterations in the Anterior Maxillary Mucosa as Induced by Implant-Retained Overdenture

PURPOSE

Blood flow disturbance from functional pressure may lead to ischemia and accumulation of metabolites leading to residual ridge resorption (RRR) underneath complete dentures. The purposes of this study were to determine the effect of mandibular complete denture (CD) and implant-retained overdenture (IRO) on blood flow disturbance in the opposing denture bearing-mucosa of maxillary CD and to compare the blood flow disturbance to RRR of the anterior maxilla.

MATERIALS AND METHODS

The test group included 9 participants rehabilitated by maxillary CD opposing mandibular IRO, while the control group consisted of 4 participants with CDs. Blood flow was measured by laser Doppler flowmetry (LDF) after denture removal for 0, 30, 60, and 90 minutes. RRR was quantified as reduction in bone volume a year post-treatment. The measurement of blood flow was then compared to the quantification of RRR.

RESULTS

The mean blood flow measure for the IRO group was significantly lower than CD after immediate denture removal and 30 minutes later. After 60 minutes, the mean difference was not significant between groups, and at 90 minutes, the mean blood flow of both groups equalized to reach a steady state of 377 BPU. The mandibular IRO had reduced the initial blood flow measure in the opposing anterior maxilla mucosa to almost a quarter (103 BPU) of the steady state value (377 BPU) compared to the CD, which reduced it to only about one half (183 BPU), suggesting greater blood flow disturbance in the IRO group. This result is in tandem with the greater reduction of bone volume observed in the IRO group, which was 7.3 ± 1.3% after a year, almost three times higher than CD group at 2.6 ± 1.7%.

CONCLUSION

IRO may cause significantly higher blood flow disturbance than CD and may have contributed to greater RRR in the anterior maxilla.

The use of laser Doppler flowmetry to evaluate oral soft tissue blood flow in humans: A review

The objective of this work is to define the conditions for improving the use of laser Doppler flowmetry (LDF) and to determine the limits for the use of this technique. This article systematically reviews the literature on the evaluation of oral soft tissue blood microcirculation by LDF. We analysed the available literature through October 2016 using the database resources Medline/PubMed, the Cochrane Oral Health Group Specialist Trials Register and the ISI Web of Knowledge. Several points emerged from this literature review The use of LDF involves specific constraints; however, the influence of different factors (temperature, tobacco, pressure etc.) must be adequately controlled when using LDF. LDF measurements of soft tissue within the oral cavity vary depending on the anatomical site. In dentistry, LDF can be used to track healing progress in periodontal surgery and to diagnose vascular flow changes in the connective tissue of mucosae covered by a removable prosthesis at an early stage prior to the onset of clinical inflammation signs.

Macroglossia associated with brainstem injury

BACKGROUND

Macroglossia has been reported in patients undergoing posterior fossa neurosurgical procedures and is thought to be as a result of venous engorgement from intubation or mechanical positioning during these prolonged procedures.

METHODS

We report three patients who developed macroglossia and dysautonomia of central neurogenic origin following brainstem injury.

RESULTS

The three patients developed macroglossia and dysautonomia with wide hemodynamic fluctuations in the setting of posterior fossa injury of the lower brainstem structures, necessitating tracheostomy placement. Macroglossia was managed with dexamethasone and there was complete resolution of dysautonomia while treated with beta-blockers and gabapentin.

CONCLUSIONS

Neurointensivists should be aware of macroglossia with dysautonomia complicating brainstem injury, which may have perilous consequences in the setting of cerebral edema or intracranial hypertension.

Doppler flowmetry as a tool of predictive, preventive and personalised dentistry

Periodontal lesions are considered a major problem in the global burden of oral diseases due to their high frequency and negative impact on quality of life. Periodontal inflammation is accomplished by a breakdown of microcirculatory function. Early detection of gingival microvessel dysfunction helps diagnose and prevent the progression of initial periodontal pathology. Doppler flowmetry is a useful tool in the diagnosis, monitoring, prognosis and management of periodontal patients which allows access not only of gingival blood flow but also of pulpal microcirculation. Doppler flowmeters might help to realise the ultimate target of predictive, preventive and personalised periodontology tailored with respect to the particular patient. This article highlights the main working principles of laser Doppler flowmeters and the ultrasonic Doppler flowmeters. The advances in blood flow measurement by ultrasonic flowmetry are discussed.

Changes in gingival blood flow during orthodontic treatment

The aim of the study was to investigate the changes in gingival blood flow due to orthodontic forces. Eleven volunteers, with the maxillary canine in an ectopic position were tested. A Laser Doppler Flowmeter (LDF) with a gingival probe was used, registering both the blood flow and temperature of the gingivae. After baseline measurement, a fixed orthodontic appliance was bonded. Measurements were repeated monthly, after activation of the appliance. The study lasted 6 months. The baseline value was 338.7 ± 201.56 P.U. [Perfusion Unit (mean ± S.D.)] which decreased to 218.9 ± 74.83 P.U. (p < 0.05) after two months and the final value of 363.9 ± 194.86 P.U was not significantly different from that initially (p > 0.5). The results showed that application of a force of 75 g resulted in a decrease in gingival blood flow up to 50%, but this returned to previous values after a few months. The study supports this measurement technique as a useful tool for monitoring gingival blood flow in long-term studies as well.

Local gingival blood flow at healthy and inflamed sites measured by laser Doppler flowmetry

BACKGROUND

This investigation aimed to: 1) develop a method to obtain reproducible laser Doppler flow readings (LDFRs) at the gingiva of the maxillary front teeth; 2) evaluate regional gingival blood flow (GBF) in healthy gingiva by laser Doppler flowmetry; 3) compare hand-held LDFR (H-LDFR) with splint LDFR (S-LDFR); and 4) monitor changes in GBF in experimental gingivitis (EG) and chronic gingivitis (CG).

METHODS

The LDFR, gingival index (GI), and plaque index (PI) were measured at 13 gingival sites (teeth #6 to #11) in 10 healthy volunteers (five males and five females), 23 to 34 years of age, over a period of 12.5 +/- 3.27 days employing a partial-mouth EG model and in 11 patients (three males and eight females), 20 to 63 years or age, with CG. LDFRs were obtained by S-LDFR or H-LDFR.

RESULTS

H-LDFRs were significantly higher than S-LDFRs (P <0.05). All EG subjects developed gingivitis (PI: 2.77 +/- 0.23; GI: 1.5 +/- 0.53). EG-LDFRs at diseased sites increased slightly but not significantly over the study period. All CG-patients had high plaque and inflammation scores (PI: 2.8 +/- 0.2; GI: 1.63 +/- 0.78). CG-LDFRs at sites with GI >1 were significantly higher than LDFRs at healthy sites (P <0.05). CG-LDFRs were significantly higher than EG-LDFRs at sites with a comparable GI (P <0.05).

CONCLUSIONS

LDFRs are positively correlated with the degree of gingival inflammation. GBF demonstrated significant differences in EG and CG. Modifications of the probe are needed to enhance its clinical applicability in clinical research of periodontal diseases.

Oral mucosal blood flow following dry ice stimulation in humans

The aim of the current pilot study was to establish a procedure that would allow the investigation of microcirculatory changes in the oral cavity. The authors studied the effects of painful stimulation using dry ice (CO2). To investigate potential regional differences in the change of blood flow, recordings were made for the tongue and at the mucosa of the hard palate, lip, and oral vestibule. The authors investigated 26 patients divided into groups of younger subjects (10 men, 3 women; age range 21-31 y) and older patients (2 men, 11 women; age range 54-74 y). Mucosal blood flow (mBF) was obtained at the hard palate, at the tip of the tongue, on the midline of the oral vestibule, and at the lip. Measurements were made during rest and for 2 minutes after application of dry ice for a 10-second duration, using a pencil-shaped apparatus. Blood pressure, heart rate, cutaneous blood flow, transcutaneous partial pressure of carbon dioxiode (PCO2) and partial pressure of oxygen (PO2) were recorded. Mucosal blood flow increased at all sites in response to application of dry ice (p <0.001), with peak flow at 0.5 minute to 1.5 minutes after onset of stimulation. During the 1.5 minutes to 2 minutes, blood flow decreased at all measurement sites with a tendency to return to baseline. Heart rate, blood pressure, pCO2, PO2, and cutaneous blood flow did not show significant changes. Overall, responses in older patients showed more variance when compared with younger patients. Stimulation by dry ice appears to be an effective, noninvasive, and tolerable means to investigate mucosal blood flow at different mucosal sites. Preliminary data indicate different levels of responsiveness to painful cold stimulation at different sites on the oral and perioral mucosa; particularly, mucosal blood flow response at the tongue was least pronounced. Therefore, assessment of stimulated mucosal blood flow appears to be a promising tool to investigate the pathophysiology of a number of neurologic symptoms, eg, the burning mouth syndrome.

Analysis of scar tissue distribution on rat palates: a laser Doppler flowmetric study

OBJECTIVE

The aim of this study was to evaluate the effectiveness of laser Doppler flowmetry (LDF) to discriminate postoperative scar tissue distribution on the palate.

METHODS

Nineteen male Wistar rats at the 20th postnatal day were divided into experimental and control groups. In the experimental group, lateral palatal mucoperiosteum was excised to form scar tissue on the palate. At the 11th postnatal week, changes in the palatal blood flow were recorded with LDF in both groups by occluding exposed common carotid arteries. Perfusion values of nonoccluded (stable) and occluded states and the ratio of occluded to stable states were compared for scar tissue and normal tissue areas, and also for the normal tissue areas. After the LDF measurements, India ink-injected specimens and tissue sections were prepared for histological observations.

RESULTS AND CONCLUSIONS

Scar tissue areas showed lower perfusion values both in the stable and occluded states, reflecting a lower vascular density in the scar tissue. The ratio of the occluded to stable states was higher in the scar tissue than in the normal tissue areas. In normal tissue areas, perfusion values of both the stable and occluded states appeared to vary, but the ratio did not vary among the areas. In the LDF study, the ratio of the occluded to stable states was considered to be the better parameter for discriminating scar tissue from normal tissue.

Electrical impedance. A method to evaluate subtle changes of the human oral mucosa

In a previous study, we mapped the differences in electrical impedance between various anatomical locations in the oral mucosa. We now explore the ability of the impedance technique to detect mild reactions in the buccal mucosa induced by the irritant sodium lauryl sulphate. This substance was applied for 15 min at a concentration of 2% to the mucosa of 26 healthy subjects. A contralateral site was used as a control. Responses were evaluated by measuring electrical impedance before exposure and after removal of the irritant, and also by visual inspection and histology. Magnitude and phase of impedance were determined in the frequency range 1 kHz to 1 MHz at 5 depth settings, and 4 physically distinct indices were calculated from the impedance data. The results showed the response to be at its maximum 5 min after removal of the test chamber, for all indices. These changes were statistically significant, whereas visual and histological alterations were slight or negligible. We conclude that the electrical impedance technique is capable of detecting mucosal changes in the invisible or barely visible range, and that the mucosal response to sodium lauryl sulphate is well characterised by the 4 indices.

The effect of hyperbaric oxygen on irradiated oral tissues: transmucosal oxygen tension measurements

PURPOSE

This study measured the effect of hyperbaric oxygen (HBO) treatment on transmucosal oxygen tension in irradiated human oral mucosa.

PATIENTS AND METHODS

Ten patients received 30 dives of HBO as part of their treatment for mandibular osteoradionecrosis. A noninvasive, nonheated oxygen electrode was used to measure the tissue surface transmucosal oxygen tension directly on the attached gingiva. Measurements were done before, during, and after HBO treatment. The normal level of gingival surface transmucosal oxygen tension was measured in five healthy volunteers.

RESULTS

During HBO treatment, the transmucosal oxygen tension increased significantly after five dives of HBO (P < .05). After 30 dives, the increases were from a mean of 50% to a mean of 86% of the transmucosal oxygen tension of normal healthy gingiva.

CONCLUSION

An increase in the transmucosal oxygen tension is based on neo-angiogenesis. Patients with subischemic tissues, such as the study population with postirradiation mucosal and osseous necrosis, therefore may benefit from treatment with HBO.