Blood flow in the dental pulp in dogs measured by local H2 gas desaturation technique

Exploring approaches to pulp vitality assessment: A scoping review of nontraditional methods

INTRODUCTION

Diagnostic procedures for pulp vitality assessment are a crucial aspect of routine dental practice. This review aims to provide a comprehensive overview of nontraditional techniques and methodologies for assessing pulp vitality, specifically exploring promising approaches that are currently not used in dental practice.

METHODS

The study protocol was registered a priori (https://osf.io/3m97z/). An extensive electronic search was conducted across multiple databases, including MEDLINE via PubMed, Scopus, Web of Science, and Embase. Inclusion criteria were guided by the research question based on the PCC model as follows: "What are the potential nontraditional techniques (Concept) for assessing pulp vitality (Population) in the field of endodontics or clinical practice (Context)?" Studies were included that explored possible approaches to pulp vitality assessment, utilizing a range of techniques, whilst any studies using traditional pulp tests (cold, heat, and electric stimulation) or well-known methods (pulse oximetry and laser Doppler flowmetry) were excluded. Reviewers independently screened articles and extracted data. A patent search was also performed.

RESULTS

Of 3062 studies, 65 were included that described nontraditional approaches for assessing pulp vitality. These included a range of optical diagnostic methods, ultrasound Doppler flowmetry (UDF), magnetic resonance imaging (MRI), terahertz imaging, tooth temperature measurements, as well as invasive methodologies, including 133xenon washout, radioisotope-labelled tracers, hydrogen gas desaturation, intravital microscopy and fluorescent microspheres isotope clearance. The patent search included artificial intelligence and biomarkers methods.

CONCLUSIONS

This review provides details for potential innovative tests that may directly describe pulp vitality. Importantly, these methods range from clinically impractical through to promising methods that may transform clinical practice. Several nontraditional techniques have the potential to enhance diagnostic accuracy and could provide valuable insights into the assessment of pulp vitality in challenging clinical scenarios.

The effects of gingival blood flow on pulpal blood flow detection using ultrasound Doppler flowmetry: animal study

Objectives

This study evaluated the effect of adjacent gingival blood flow on detection of pulpal blood flow (PBF) using ultrasound Doppler flowmetry (UDF) through animal study.

Materials and Methods

The study included 36 right and left maxillary the third incisors and canines in 9 experimental dogs. The study included 2 main steps: In the first step, the pulse sound level (PSL) was recorded on the cervical part of each tooth without flap elevation (Group 1), with flap elevation (Group 2), and after it was repositioned in place (Group 3). In the second step, the PSL was recorded on the cervical part of each tooth (Group 4), after pulpotomy (Group 5), after partial pulp extirpation (Group 6), after complete extirpation (Group 7), and after canal filling (Group 8). In Groups 5-8, the study was performed with and without flap elevation in the left and right teeth, respectively. The PSL was graded as follows: 0, inaudible; 1, heard faintly; and 2, heard well. The difference between each group was analyzed using Friedman's test with Wilcoxon signed-rank tests (α = 0.05).

Results

In step 1, the PSL results were Group 1 > 2 and 3. In step 2, there was no significant difference between the groups when the flap was not elevated, while PSL results were Group 4 > 5 ≥ 6 and 7 ≥ 8 when the flap was elevated.

Conclusions

PBF is affected by gingival blood flow when measured with UDF. UDF measurements require isolation of gingiva from the tooth.

Changes in human pulp blood flow during canine retraction

AIM

To evaluate the effects of maxillary canine retraction on pulpal blood flow (PBF) in humans as recorded by laser Doppler flowmetry (LDF).

METHODS

Maxillary canines of 24 participants were divided into two groups (n = 12 each). Teeth in the study group underwent maxillary canine retraction using mini-implants as anchorage for approximately 4 months, with 100 g of force applied via coil springs. Subjects in the control group received no orthodontic treatment. LDF measurements were recorded at baseline (T0); during retraction, at 24 hours (T1), 3 days (T2), 7 days (T3) and 1 month (T4); and at the end of retraction (T5) in the study group and at similar time-points in control subjects. Data were analyzed using the Friedman, Wilcoxon signed rank and Mann-Whitney U tests, with the significance level set at 0.05.

RESULTS

No significant changes in PBF perfusion units (PU) were observed in the control group over the course of the study. However, PBF in the study group increased significantly from T0 (3.6 ± 0.2 PU) to T1 (3.7 ± 0.2 PU, p < 0.001) and decreased severely from T1 to T2 (3.3 ± 0.1, p < 0.001). PBF in the study group was still significantly lower at T3 (3.4 ± 0.1 PU, p < 0.001) in comparison to T0; however, at T4 and T5, PBF was found to have returned to pre-retraction levels.

CONCLUSION

The fact that PBF values returned to initial levels within one month of the initiation of retraction despite short-term, hyperaemic, regressive changes demonstrates that the changes observed in PBF during canine retraction are reversible.

The use of pulse oximetry in evaluation of pulp vitality in immature permanent teeth

BACKGROUND AND AIM

The current methods of pulp vitality assessment, either electric or thermal, are of limited use in children. Recently, traumatized and immature teeth may not respond to such methods and because such methods require subjective responses, it may not provide accurate results particularly in children. Pulse oximetry, an atraumatic approach, is used to measure oxygen saturation in vascular system. The aim of this study was to investigate the use of pulse oximetry to evaluate pulp vitality status in immature permanent teeth.

METHODS AND MATERIALS

The study was conducted on 329 maxillary central and lateral incisors in children. The negative control group consisted of 10 root filled teeth. Systemic oxygen saturation was first measured on the thumb of the individual using a custom-made sensor. Oxygen saturation values of the teeth were then evaluated. The correlation between oxygen saturation measurement obtained from finger and tooth, and the correlation between oxygen saturation values and stage of root development were analyzed. A further comparison was made between the teeth with open and closed apex.

RESULTS

Mean oxygen values recorded in the patient's finger were 97.17%, and mean oxygen values in the maxillary central and lateral incisors were 86.77% and 83/92%, respectively. There was no significant correlation between blood oxygen levels in the finger and in the teeth. (P > 0.05) There was a significant negative correlation between the stage of root development and the blood oxygen levels in the patients' teeth. (P < 0.05) Mean oxygen values in the teeth with open apex were significantly higher than the teeth with closed apex. (P < 0.001).

CONCLUSION

Vital teeth provided consistent oxygen saturation readings, and non-vital teeth recorded no oxygen saturation values. During tooth development, the oxygen saturation values decreased. These findings confirm that the pulse oximetry is capable of detecting the pulpal blood flow and oxygen saturation.

Computerized infrared thermographic imaging and pulpal blood flow: Part 1. A protocol for thermal imaging of human teeth

AIM

To observe the thermographic appearance of teeth and to develop a suitable protocol for imaging teeth in human subjects using modern thermographic imaging (TI) equipment in a thermologically controlled environment.

METHODOLOGY

The emissivity of enamel was investigated using an extracted incisor tooth. A total of 12 unrestored maxillary lateral incisors in six healthy patients were then imaged under rubber dam after a 20-min equilibration period and the thermographic data analysed using a dedicated software package. Recordings were made from standardized gingival and incisal sites on each tooth and the temperature gradient established for each tooth. Subsequently, a sequence of images of both maxillary central incisors in one patient was stored every 30 s during a 20-min equilibration period with and without an air-conditioning unit in operation.

RESULTS

For the lateral incisors there was a consistent temperature gradient (mean 1.28 degrees C) from gingival area to incisal area and there were no statistically significant differences between right and left sides for the gingival site (t = 0.34, NS) or the incisal site (t = 0.62, NS). The air-conditioning unit had a rapid and profound cooling effect. With the air-conditioning disabled there was a mean tooth surface temperature increase of 1.1 degrees C from 0 to 5 min of the equilibration period and 0.3 degree C from 15 to 20 min.

CONCLUSIONS

There was no significant difference in gingival or incisal temperatures between pairs of contralateral maxillary lateral incisors and a consistent temperature gradient existed from gingival to incisal areas of healthy maxillary lateral incisor teeth. The protocol described is suitable for TI of vital teeth. However, TI measured tooth surface temperature only which was extremely sensitive to air currents. A 15-min acclimatization period under rubber dam was adequate to allow stable tooth surface temperature measurement.

The role of sensory neuropeptides and nitric oxide on pulpal blood flow and tissue pressure in the ferret

A study was designed to investigate the effects of close intra-arterial infusion of antagonists to the sensory neuropeptides calcitonin gene-related peptide and substance P, as well as the effect of the nitric oxide synthesis inhibitor L-NAME on pulpal blood flow and interstitial fluid pressure during resting conditions and after electrical tooth stimulation. The micropuncture technique was used to measure tissue pressure and laser-Doppler flowmetry for blood flow recordings in ferret canine teeth. Close intra-arterial infusion of antagonists to calcitonin gene-related peptide and substance P significantly reduced resting blood flow (p < 0.05) and interstitial fluid pressure (p < 0.005) by unchanged systemic arterial pressure, while L-NAME administration caused a significant rise in interstitial fluid pressure (p < 0.05) and systemic arterial pressure (p < 0.005), with a concomitant fall in resting blood flow (p < 0.005). Tooth stimulation after calcitonin gene-related peptide antagonist infusion gave no significant change in blood flow or interstitial fluid pressure, whereas substance P antagonist infusion only partly eliminated the vasodilator response. L-NAME had no effect on the vasodilation induced by tooth stimulation. It is concluded that a resting vasodilator tone due to release of calcitonin gene-related peptide, substance P, and nitric oxide exists in the ferret dental pulp. The sensory neuropeptides exert their effect predominantly on pre-capillary vessels, and nitric oxide predominantly on post-capillary vessels. The sensory neuropeptide calcitonin gene-related peptide seems to be mainly responsible for the increase in blood flow and interstitial fluid pressure during tooth stimulation, whereas there was no evidence that nitric oxide participates in the vasodilation induced by tooth stimulation.

Optical detection of hemoglobin in pulpal blood

An in vitro, flow-through optical system was designed to measure hemoglobin (Hb) concentrations in the pulp space. The system included light-emitting diodes and a silicon photodetector positioned on opposing surfaces of human teeth. A syringe pump allowed a controlled flow of blood through the pulp chamber. The Hb concentration was computed as a nonlinear function of transmitted light intensity. Transmitted light intensities were also used as indicators of oxygenation level. Optical measurements correlated with Hb values measured by the conventional cyanmethemoglobin method (r=0.993). The mean percentage error was 5.8%, and the standard error of prediction was 0.77 g/dl for Hb concentrations ranging from 4 to 20 g/dl. Deoxygenated blood exhibited up to 31% lower transmitted intensity. Light transmission through teeth may be useful in the assessment of total Hb and blood oxygenation within the pulp chamber.

Optical characteristics of human extracted teeth and the possible application of photoplethysmography to the human pulp

In order to record pulp blood flow by photoplethysmography, the light transmission properties of extracted human teeth and human peripheral blood at wavelengths between 400 and 800 nm were first investigated. Transmission through peripheral blood and extracted teeth was lower at wavelengths shorter than 600 nm. Transmitted-light photoplethysmography (TLP) was applied to teeth in situ using a tungsten light, or one of two light-emitting diodes (LED) with peak wavelengths of 565 and 695 nm. A CdS-CdSe photoconductive cell was used as a detector. The LED with a peak intensity at 565 nm was the most efficient of the three light sources for recording the TLP. The results indicate that the TLP could be used to assess pulp vitality.

Identification of alpha 2 adrenoceptors in the blood vessels of the dental pulp

Using selective agonists and antagonists of alpha2 adrenoceptors, attempts were made to identify the subtype alpha2 adrenoceptors in the blood vessels of the canine dental pulp. In chloralose-anaesthetized dogs, intra-arterial administration of noradrenaline and guanabenz in different doses produced a dose-related pulpal vasoconstriction which was measured using hydrogen-gas clearance. The vasoconstrictor response to noradrenaline was inhibited by phentolamine, a non-selective alpha adrenoceptor antagonist. The response to guanabenz was inhibited by rauwolscine, a highly selective alpha2 adrenoceptor antagonist. The results demonstrated that alpha2 adrenoceptors are present in the blood vessels of dog dental pulp.

Biphasic pulp blood-flow response to substance P in the dog as measured with a radiolabelled, microsphere injection method

A dose of the vasoactive substance P (SP), affecting local circulation only (0.0001-0.001 micrograms/kg body weight) when given by a close injection into the maxillary artery, caused a biphasic flow response in pulpal blood flow (PBF), as measured by a radioisotope-labelled 15 micron microsphere injection technique. Immediately after the SP injection, PBF increased some 66 per cent (p less than 0.02) and vascular hindrance (Z) decreased to 40 per cent against control values (p less than 0.02), indicating vasodilation. Thirty seconds after the SP injection, PBF decreased by 53 per cent (p less than 0.05), and pulpal Z increased 139 per cent against control values (p less than 0.02), indicating decreased blood flow. This biphasic flow response may be due to the active vasodilation of arterioles by SP, which causes a compression of venules and hence a reduction of PBF in what is a low-compliance system.

Blood flow changes in the dental pulp of the cat and rat measured simultaneously by laser Doppler flowmetry and local 125I clearance

Blood flow changes in the dental pulp of lower canine teeth of mature cats and incisors of mature rats were investigated with simultaneous laser Doppler flowmetry and local 125I-clearance (wash-out) during electrical sympathetic stimulation, efferent stimulation of n. alveolaris inferior (IAN) (cats) and i.a. infusions of substance P (SP) (cats). Stimulation (1-4 Hz, 4 V., 1.5 ms) of the cervical sympathetic trunk produced frequency-dependent decreases in both laser Doppler output and disappearance rate of iodine tracer from the dental pulp. For the effects of sympathetic stimulation, the correlation (r2) between the results obtained by the two methods was 0.89 (12 observations, six animals). Blood flow measurements by both methods were increased following i.a. infusions of SP (r2 = 0.64, six observations, three animals). However, upon stimulation of IAN (10 Hz 10 V, 5 ms) the laser Doppler flow values showed an increase while the local 125I clearance rate was unaffected or even decreased. The discrepancy between the results obtained following IAN stimulation indicates that the two methods reflect blood flow changes in different parts of the pulpal vascular bed and that the flow is unevenly distributed to these parts during antidromic IAN stimulation. The laser Doppler flowmetry seems to reflect the total blood flow in the coronal pulp and therefore this non-invasive method may be useful for monitoring blood flow changes in the tooth.

Pulpal blood flow in immature permanent dog teeth after replantation

Pulpal blood flow (PBF) was measuring by H2-gas clearance in 35 replanted (incisors and premolars) and 22 contralateral control dog teeth. The PBF measurements were taken 6, 10, 16, 21 and 28 days after replantation. At 6, 10 and 16 days after replantation there was no measurable blood flow in the coronal pulp of either replanted incisors or premolars. 21 days after replantation a considerable reduction in PBF was measured in all replanted teeth. On average, PBF was reduced to about one fifth of PBF in the simultaneously measured contralateral controls. Four weeks after replantation, a more than threefold increase in PBF was measured in premolars with two roots, while PBF in premolars with one root and incisors was consistently reduced to an average of 40% of the controls. The vascular pattern of the teeth 4 wk after replantation was identified with perfusion of silicon rubber. The measurements suggest that replanted multirooted teeth revascularize more easily than single-rooted teeth, and that pulpal repair is restored by a gradual replacement and proliferation of new tissue.

Regulation of pulpal blood flow

The regulation of blood flow of the dental pulp was investigated in dogs and rats anesthetized with sodium pentobarbital. Pulpal blood flow was altered by variations of local and systemic hemodynamics. Variation in pulpal hemodynamics was attained by means of close intra-arterial injections of adrenergic agonists (NE and ISO) and their antagonists (PBZ and Propranolol). Variation in systemic hemodynamics was achieved by hemodilution, hemo-concentration, hemorrhage, and SNP infusion. Macrocirculatory blood flow (ml/min/100 g) in the dental pulp was measured with both the 133Xe washout and the 15-microns radioisotope-labeled microsphere injection methods on the canine teeth of dogs, to provide a comparison of the two methods in the same tooth. Microcirculatory studies were conducted in the rat incisor tooth with microscopic determination of the vascular pattern, RBC velocity, and intravascular volumetric flow distribution. Pulpal resistance vessels have alpha- and beta-adrenergic receptors. Activation of alpha-receptors by intra-arterial injection of NE caused both a reduction in macrocirculatory Qp in dogs and decreases in arteriolar and venular diameters and intravascular volumetric flow (Qi) in rats. These responses were blocked by the alpha-antagonist PBZ. Activation of beta-receptors by intra-arterial injection of ISO caused a paradoxical reduction of Qp in dogs. In rats, ISO caused a transient increase in arteriolar Qi followed by a flow reduction; arteriolar dilation was accompanied by venular constriction. These macrocirculatory and microcirculatory responses to ISO were blocked by the alpha-antagonist propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of blood flow in the dental pulp of dogs with the 133xenon washout method

Following rapid injection of 133Xe into the maxillary artery, the radioactivity from a dog canine tooth was monitored with a specially-designed scintillation probe connected to a multichannel analyser. With a PDP 11/10 minicomputer, the semilogarithmic radioactivity-time curve was resolved into a fast component and a slow component using best fit least-square lines and the exponential rate constant (k) was determined for each component. The blood flow per unit of pulp mass (Q, in ml/min per 100 g) was obtained using the equation: Q = k X lambda tb, where lambda tb is the tissue-blood partition coefficient of 133Xe in the pulp determined for the haematocrit value of the individual experiments. The fast-component blood flow was 53.12 +/- 3.12 and the slow-component blood flow was 8.86 +/- 0.53 ml/min per 100 g (mean +/- SEM, n = 21). Although the exact anatomical areas for the fast and slow components are yet to be determined, the results show heterogeneity of blood flow in the pulp. The study showed that pulp blood flow in an intact tooth can be measured with the 133Xe washout method; the method enables study of circulatory physiology of the pulp in health and disease.

Effect of dehydration on renal blood flow in dog

The effect of dehydration on intrarenal blood flow was investigated in 11 dogs, using polarographic determination of H2-gas desaturation for measuring local blood flow in inner cortex (ICF) and outer cortex (OCF). Dehydration was induced by 48 h water deprivation +2-300 mg ethacrynic acid (EA) per os the day before the experiment. Compared to a control group (n=9) ICF was markedly reduced to 2.40 +/- 0.47 ml/min X g (control 3.23 +/- 0.64) whereas OCF 3.29 +/- 0.80 ml/min X g was nearly unchanged (control 3.59 +/- 0.85). The ratio OCF/ICF was increased to 1.37 (1.11). Further dehydration by hypertonic peritoneal dialysis for 3 h increased Hct to 60 +/- 4 and further reduced OCF and ICF, without significant change of the OCF/ICF-ratio. At Hct above 55 sudden and intermittent changes in local cortical blood flow were recorded randomly at individual electrode sites, showing ischemic periods lasting for 1 to 60 min. Such flow changes were observed in 13 of 14 expts. and were not accompanied by changes in RBF. It is concluded that moderate dehydration causes a greater reduction of ICF than of OCF. Severe dehydration gives in addition rise to patchy, intermittent ischemia in both cortical layers.

Quantification of pulpal blood flow in developing teeth of dogs

Pulpal blood flow was determined in 32 dogs ranging in age from 6 weeks to 18 months by the isotope fractionation method incorporating diffusible and nondiffusible tracers. Dogs were placed into selected age groups by the developmental status of the canine teeth. For the teeth sampled, the maxillary first, second, and third incisors along with the canines and first molars, pulpal blood flow was determined to be not different in teeth at various developmental stages. For some dental pulps, alveolar mucosa, and bone, the tracers were not determining equivalent blood flows. Because of incomplete trapping of the 7- to 10 mu microspheres and the flow limitation of 86Rb, the 15 mu spheres would appear to be a reliable indicator of "total" blood flow to pulpal tissues. However, in alveolar mucosa and bone, and 15 mu microspheres may not be completely trapped and thus, may underestimate blood flow to these tissues. Within the age range of these dogs, tissue blood flow was not dependent upon the stages of oral development.

Effect of vasodilating drugs on external carotid and pulpal blood flow in dogs: "stealing" of dental perfusion pressure

Blood flow in the external cartoid artery (ECBF) and dental pulp (PBF) was measured during arterial infusion of vasodilators (isoprenaline, papaverine, acetylcholine and bradykinin). Systemic arterial pressure (AP) and local arterial pressure of the teeth (LAP) were recorded in a femoral and the lateral nasal artery respectively. All four vasodilators were found to increase ECBF and simultaneously reduce lateral nasal arterial pressure--or in other words-to STEAL" PERFUSION PRESSURE FROM THE TEETH. AP remained practically unchanged whereas PBF was variably affected. During infusion of isoprenaline PBF decreased on average by 19% of control. Papaverine nearly doubled PBG, while bradykinin caused no consistent change. Great pulpal flow variations were often recorded during constant acetylcholine infusion rate. The variable effect of the four vasodilators on PBF could partly be explained by the fall in LAP. Calculated pulpal resistance (LAP/PBF) showed no consistent change during isoprenaline infusion, bradykinin caused a slight fall and papaverine reduced LAP/PBF by 49%. The experiments demonstrate that due to the "stealing" of dental perfusion pressure caused by vasodilation in the neighbouring tissues, the effect of vasodilators on pulpal resistance vessels cannot be estimated without knowledge of the pressure in the small arteries directly feeding the teeth.