Experiments on extracted teeth into the validity of using laser Doppler techniques for recording pulpal blood flow

Time-course of the effect of potassium oxalate in the treatment of hypersensitive dentine in man

OBJECTIVE

Investigate the cause of hypersensitive dentine (HD) by recording the time course of changes in dentine sensitivity, sensory threshold to electrical stimulation (ET) and pulpal blood flow (PBF) following tubular occlusion using in vitro and clinical experiments.

DESIGN

Nineteen teeth with HD and 13 with normal dentine from 8 participants were evaluated, and the intensity of any pain produced by various stimuli was recorded at different times after oxalate treatment. The participants used a visual-analogue scale (VAS) to indicate the intensity of any pain. The ET and PBF were recorded at the same times.

RESULTS

Preliminary in vitro experiments showed that oxalate treatment had no effect on the method used to record PBF, and blocked the treated tubules immediately after application. Considering teeth with HD, a decrease in the median VAS evoked by all forms of stimulation was observed at all post-treatment times, except immediately after treatment (p < 0.05), while the treatment produced no significant effect in teeth with normal dentine. No significant changes in ET or PBF was observed in any of the groups.

CONCLUSIONS

The effect of oxalate in relieving the symptoms of HD is not only due to a reduction in the intensity of stimulation of sensory receptors sensitive to fluid flow in the dentinal tubules, but also to a reduce in the sensitivity of the receptors that respond to dentine stimulation. There was no evidence that acute pulpitis or central sensitization to pain, which would be associated with changes in PBF or ET, contributes to HD.

The Decisive Role of Laser Doppler Flowmetry for Pulp Preservation in Discolored Traumatized Teeth

Objective: It has been stated that blood pigments within discolored teeth may interfere with Laser Doppler Flowmetry (LDF) measurements. The aim of this study was to assess pulp vitality with LDF in a cohort of discolored traumatized teeth referred for endodontic treatment or where the referring dentist had doubts regarding maintained tooth vitality. Background: Discoloration of teeth is a common sequel of dental trauma. Still today, it is taken as an indicator for root canal treatment. Transient apical breakdown (TAB) is confused with apical periodontitis, although it is a sequel of dental trauma in young mature teeth and will result in revascularization and dissolution of the apical radiolucency. Methods: A total of 26 patients with 28 discolored teeth, belonging to a cohort of referred patients with traumatized teeth referred for root canal treatment and/or pulp vitality assessment were screened on color with photographs by three investigators, with traditional sensibility tests and with a Moor VMS II LDF meter. Results: The color of the intrinsically discolored teeth was grayish in 58% of teeth, blue 20%, pink/crimson 12%, and yellow 4%. Eighty-five percent were central maxillary incisors, 11% were mandibulary incisors. Thanks to LDF, 43% of the trauma cases in this small cohort with discoloration underwent root canal treatment instead of 70% with traditional sensibility tests as indicator. TAB was found in 11%. Conclusions: LDF was decisive in diagnosing vitality of discolored teeth and there was no negative impact of tooth discoloration on LDF measurements.

Human pulpal blood flow in different root formation stages measured with transmitted-light plethysmography

OBJECTIVES

To determine the pulp vitality after traumatic injury, dentists often use pulp sensitivity tests, which can be ambiguous in young permanent teeth with incomplete root formation. Transmitted-light plethysmography (TLP) is a non-invasive objective method that uses a 525-nm LED to detect blood volume change in the pulp. The present study aimed (1) to investigate pulpal blood flow with TLP and optical characteristics in healthy permanent maxillary incisors in different root formation stages, and (2) to assess the influences of body growth of the children and tooth color on the TLP amplitude.

DESIGN

Seventy-eight fully erupted maxillary central incisors were divided into four groups, according to the root formation stages. Group 1: root with wide-open apex, Group 2: root completed in length with open apex, Group 3: root with half-closed apex, Group 4: root with complete formation. The TLP amplitude, optical density, electric pulp testing, and cervical tooth color measurements of each group were compared using a one-way analysis of variance followed by the Bonferroni method. The correlation between the weights/heights of children and TLP amplitudes was analyzed using Pearson coefficient.

RESULTS

The TLP amplitude was significantly higher in Group 3 than in the other groups. The amplitude was correlated with the weights/heights of children, but not with the tooth color. Optical density and electric sensitivity increased with tooth maturation.

CONCLUSION

The amplitude of TLP and optical density may be affected by growth and development in children and indicate changes in the vascular dynamics of the pulp and hard tissue maturation during root formation stages.

Magnification—a New Look at a Long-known Optical Property of Dentin

Light propagation in human dentin exhibits a strong directional dependence featuring the long-known optical magnification property. We hypothesized that this anisotropic effect is caused by multiple scattering at the dentin tubules, and not by fiberoptic effects, as had been previously assumed. We performed measurements of the transmitted intensity from dentin disks and compared them with Monte Carlo simulations of light propagation in dentin, considering the scattering by the tissue’s microstructure. We found that the optical anisotropy of dentin can be fully explained with this model. We concluded that the magnification property of dentin is due to multiple scattering by the dental microstructure.

Effect of full crown preparation on pulpal blood flow in man

OBJECTIVE

To determine if full crown preparation causes an increase in pulpal blood flow (PBF), indicating inflammation, in human subjects.

DESIGN

The experiments were carried out on 35 intact, mandibular posterior teeth in 13 subjects: 32 were abutments for 16 fixed bridges that replaced first molars; the other 3 were first premolars adjacent to abutment teeth that served as un-operated controls. Crown preparations were made using an air-rotor with water-spray under regional block anaesthesia (4% articaine with epinephrine 1:100,000). PBF was recorded with a laser Doppler flow meter (LDF) before and after administering the anaesthetic, with the LDF probe on the buccal enamel. PBF was then recorded from the abutment teeth with the probe on buccal dentine after preparing the buccal surfaces of both teeth, after completing the crown preparations, and after 1 and 7days. PBF was also recorded from the buccal enamel of the control teeth on each occasion.

RESULTS

The mean±S.D. PBF values before and after anaesthesia were 2.63±2.13 and 2.42±2.38P.U. respectively, which were not significantly different (Paired t-test). The mean values for the abutment teeth after buccal preparation, after complete crown preparation, and after 1 and 7days were 5.20±2.49, 4.53±2.52, 4.92±2.98 and 5.48±2.65P.U. respectively. The 4 values for each tooth were not significantly different (two-way RM ANOVA). In the control group, the values under all six conditions were not significantly different.

CONCLUSIONS

Regional block anaesthesia produced no change in PBF, nor did full-crown preparation, neither immediately after the procedure nor 1 and 7days later.

Changes in maxillary incisor dental pulp blood flow during intrusion by mini-implants

AIM

The aim of this clinical study was to identify changes in pulpal blood flow (PBF) in human central incisors resulting from short- and long-term intrusive orthodontic forces from mini-implants.

MATERIALS AND METHODS

A total of 40 sound upper central and lateral incisors in 20 patients scheduled for intrusion for orthodontic reasons were divided into two groups. From each group, 20 teeth were subjected to intrusive force from mini-implants (Group 1 = Light Force: 40 g; Group 2 = Heavy Force: 120 g), whereas the remaining 20 contralateral teeth were not subjected to forces from mini-implants and served as controls. Laser-Doppler flowmetry (LDF) measurements were recorded at baseline and at 3 days and 3 weeks following intrusion.

RESULTS

PBF decreased significantly at 3 days (Light Force Group: 7.72 ± 0.50; Heavy Force Group: 7.72 ± 0.52) and then increased towards baseline at 3 weeks (Light Force Group: 10.37 ± 0.58; Heavy Force Group: 10.31 ± 0.45) following intrusion.

CONCLUSIONS

In other words, despite slight regressive changes in pulpal tissue in the short-term, PBF improved after 3 weeks following intrusion by mini-implants, indicating that the changes observed in PBF is reversible, even following radical incisor intrusion.

Pulp and periradicular testing

Pulp and periradicular testing is crucial to the initial trauma evaluation and to subsequent monitoring of the traumatized teeth and supporting structures. An accurate diagnosis serves as the basis for therapeutic intervention and helps to ensure that destruction of the dental structures will be minimized and function will be regained. The purpose of this review is to present the current best evidence for accurate diagnostic testing of the pulp and periapex of traumatized teeth. Five databases were searched for literature pertaining to pulpal testing and trauma. Widely recognized textbooks were also consulted. Currently used pulp vitality testing is constrained by its subjective character and by the fact that it is a measure of neuronal status and not true pulpal viability. Tests that measure tissue perfusion more accurately reflect pulpal vitality, but they are not available commercially. This review discusses the specificity, sensitivity, and accuracy of commonly used tests, with emphasis on the applicability of certain tests to specific patient presentations in trauma. Factors that influence test selection are discussed, and specific recommendations are made on the basis of best evidence. Although differences exist between the various studies as to the accuracy of commonly used pulpal and periradicular tests, most of these have acceptable predictive value. Pulpal and periradicular tests in the trauma patient should be used in conjunction with clinical and radiographic observations to arrive at a diagnosis and treatment plan.

Assessment of pulpal vitality using laser speckle imaging

BACKGROUND AND OBJECTIVE

The pulpal chamber of each tooth contains the vasculature necessary to maintain a viable tooth. A critical need exists to develop an objective, repeatable method to assess pulpal viability. We hypothesized that the existence of blood perfusion within the pulp can be determined with analysis of laser speckle imaging (LSI) patterns generated by transillumination of the tooth.

STUDY DESIGN/MATERIALS AND METHODS

We used nine extracted human cuspids and incisors. A Tygon tube was inserted into a channel created within each tooth and Intralipid pumped through the tube in a controlled manner with a syringe infusion pump. We evaluated the feasibility of LSI for flow assessment using both transillumination and epiillumination imaging configurations. With the transillumination geometry, we also assessed the effect of the angle of incidence of the probe laser light on the speckle flow index (SFI) values extracted from the collected speckle images.

RESULTS

Transillumination LSI, and not epiillumination LSI, enables differentiation between the absence and presence of perfusion in an in vitro tooth model. SFI values are insensitive to the relative angle of incidence of the laser light, over a wide range of angles.

CONCLUSIONS

Our preliminary in vitro data suggest that transillumination LSI is a promising method to identify the presence of blood flow in the pulpal chamber. Future in vivo evaluation is warranted.

Pulpal blood flow changes in abutment teeth of removable partial dentures

The purpose of this study was to investigate the effect of tooth supported (TSD) and tooth-tissue supported (TTSD) removable partial denture wearing on pulpal blood flow (PBF) of the abutment teeth by using Laser Doppler Flowmeter (LDF). Measurements were carried out on 60 teeth of 28 patients (28 teeth and 12 patients of TTSD group, 32 teeth and 16 patients of TSD group) who had not worn any type of removable partial dentures before, had no systemic problems and were non smokers. PBF values were recorded by LDF before insertion (day 0) and after insertion of dentures at day 1, day 7 and day 30. Statistical analysis was performed by student t test and covariance analyses of repeated measurements. In the group TTSD, the mean values of PBF decreased statistically significantly at day 1 after insertion when compared with PBF values before insertion (p<0,01). There was no statistically significant difference among PBF mean values on 1st, 7th and 30th day. However, in the group TSD, there was no statistically significant difference among PBF mean values before insertion and on 1st, 7th and 30th day. In other words, PBF mean values in group TSD continued without changing statistically significant on 1st, 7th and 30th day.TTSD wearing may show negative effect on the abutment teeth due to decreasing basal PBF.

Evaluation of the ability of laser Doppler flowmetry for the assessment of pulp vitality in general dental practice

OBJECTIVES

In this study we investigated pulpal blood flow (PBF) values and moving blood cell velocity (MBCV) curves recorded by laser Doppler flowmetry (LDF) for pulpal vitality diagnosis in general dental practice and to compare MBCV curves to standard diagnostic tests in traumatology.

STUDY DESIGN

LDF tests performed with the PeriFlux System 5000 were applied to vital and nonvital (endodontic treatment) teeth of healthy students (n = 52) and on 24 luxated teeth of patients.

RESULTS

The PBF values were not reproducible and no statistically significant differences were observed between vital and nonvital teeth. MBCV curves in contrast could distinguish between the 2 tooth types. Tests on luxated teeth showed that while 62.5% of MBCV curves correlated with conventional vitality tests, only 12.5% of MBCV curves could help in vital diagnosis.

CONCLUSION

When applied to luxated teeth, the MBCV curve appeared to be accurate when the standard vitality tests indicated a nonvital diagnosis.

Penetration depth of laser Doppler flowmetry beam in teeth

OBJECTIVE

The aim of this study was to determine the penetration depth of laser light in teeth for contact and noncontact probe tip.

STUDY DESIGN

Fifty-one freshly extracted human mature maxillary and mandibular single rooted teeth were selected for the study. A laser Doppler flowmeter was used as a laser source. A digital camera was used to take pictures (with "night shot" mode in total darkness). When probe tip was in contact and when it was 1 mm away from the tooth, the depths of the areas illuminated in high and low density were measured.

RESULTS

In contact probe, root was illuminated to 4.28 +/- 0.14 mm depth with high density and 13.27 +/- 0.27 mm depth with low density. In noncontact probe, 4.36 +/- 0.16 mm with high density and 13.28 +/- 0.30 mm with low density of illumination were seen on the root. Between contact and noncontact probe situations the difference was not statistically significant in the depth of illumination. On the other hand, in both groups the difference between areas illuminated in high and low density was statistically significant (P < .05).

CONCLUSION

Contact or noncontact of the probe on tooth surface did not show any significant difference in light penetration. Besides, we think that, for the present, it is impossible to eliminate the contamination from periodontal tissues completely even if the necessary precautions (periodontal paste etc.) are taken.

Effect of gingiva on laser doppler pulpal blood flow measurements

The purpose of this study was to evaluate the effect of labial and palatinal gingiva on laser Doppler pulpal blood flow measurements. Twenty upper central incisor teeth determined to be vital from 20 volunteers were included into the study. To stabilize the probe, a laboratory-made acrylic splint positioned the probe labially on the cervical third of the tooth crown. We collected measurements without any gingival covering, and under three conditions: after application of an opaque paste on the labial gingiva, the palatal gingiva, or both the labial and palatal gingiva. The measurement values decreased 46% when there was opaque paste on labial gingiva, 10% on palatinal gingiva, and 63% on both. The decrease in the values when there was an opaque paste on palatinal gingiva was not statistically significant (p > 0.05). The differences between all other groups were statistically significant (p < 0.05). In these measurements, the contribution of labial gingiva to laser Doppler pulpal blood flow measurements is more than that of palatinal gingiva.

The sources of laser Doppler blood-flow signals recorded from vital and root canal treated teeth

OBJECTIVES

The aim was to determine the strength of signals derived from the dental pulp and those from the surrounding tissues in human teeth using the laser Doppler flowmetry (LDF).

METHODS

Twenty-six vital teeth (13 experimental and 13 controls) from 12 patients were used. Experimental teeth had root canal treatment in a single visit and their healthy antimeres were controls. Blood flow measurements were made before and after local anaesthesia, after root canal preparation, following root canal filling and coronal restoration.

RESULTS

Perfusion unit (PU) values recorded from empty pulp chamber were determined to be only 30% lower than the values recorded before anaesthesia from the experimental intact teeth. When the measurements in the group were compared with each other the values of variation in the both groups were not statistically significant. The variation between the groups when the measurement values before anaesthesia, 10min after anaesthesia and after coronal restoration were compared, it was not statistically significant (P>0.05). The variation between the groups after preparation and root canal filling in their values of measurements was important statistically (P<0.05). The measurement values of the study group were lower than that of the control group.

CONCLUSIONS

In pulpal, LDF a major portion of the signal comes from tissues other than pulp. Without taking precautions (such as rubber-dam application) in pulp blood flow measurements, the results may be inconsistent.

The sources of laser Doppler blood-flow signals recorded from human teeth

Records of pulpal blood flow obtained from human teeth with a laser Doppler flowmeter include a very large component derived from periodontal and other tissues outside the pulp, but this contamination can be reduced by covering the surrounding tissues with opaque rubber dam. The present experiments were carried out to determine what proportion of the signal obtained with this dam in place is derived from non-pulpal tissues. Recordings were made from 22 healthy, intact upper incisors in 14 individuals (aged 22-40 years) with and without dam under the following conditions: from the intact teeth, after local anaesthesia (LA) and the preparation of a deep cavity in the incisal third of the labial surface of the tooth, and after removal of the pulp and arrest of bleeding. In some cases, a reading was also made after replacing the pulp in the pulp cavity. The rubber dam reduced significantly (P<0.05) the mean blood flow reading from the intact teeth by 73%, from 6.98 arbitrary perfusion units (PU) (+/-1.30 S.D., n=22) to 1.92+/-1.50 PU. After LA and cavity preparation, the mean signal with dam was 1.45+/-0.61 PU (n=16). This fell significantly by 76% to 0.35+/-0.19 PU (n=16) when the pulp was removed but not replaced, and by 43% to 0.98+/-0.36 PU (n=14) when the pulp was removed and replaced in the pulp cavity. The latter condition is thought to reproduce most closely the scattering of light in an intact tooth. The results confirm previous findings that up to 80% of the laser Doppler blood-flow signal recorded from an intact human tooth without rubber dam is of non-pulpal origin. They also show that only approximately 43% of the signal recorded with an opaque rubber dam is from pulp.

Age-related changes in the human pulpal blood flow measured by laser Doppler flowmetry

The purpose of this study was to examine the age-related changes in human pulpal blood flow (PBF). Recordings were taken from 22 clinically healthy upper central incisors in 22 healthy participants (age: 8-75 years). A Moor blood flow monitor (type MBF3D) was used to measure PBF; and subjects' electrocardiogram (ECG), mean blood pressure (BP) and heart rate (HR) were also recorded. The resting PBF was significantly decreased with the increased age of the participants (Pearson's correlation coefficient, P < 0.001). The examined tooth crown was briefly(1 s) cooled using a dental coolant, and significant reductions in PBF were induced (one-way repeated measures anova, P < 0.05). The magnitude of the reduction (%) was significantly decreased with the increased age of the participants (Pearson's correlation coefficient, P < 0.05). The findings indicate that the hemodynamics in the human pulp is reduced with age.

Properties of single nerve fibres that evoke blood flow changes in cat dental pulp

Single nerve fibres innervating tooth pulp were isolated from filaments dissected from the inferior alveolar nerve in 17 anaesthetized cats. The fibres were studied to determine whether electrical stimulation of single units produced detectable changes in pulpal blood flow. Single pulpal nerve fibres were electrically stimulated at just above their thresholds and blood flow was recorded with a laser-Doppler flow meter from the pulp of the ipsilateral canine. The thresholds of single fibres in dissected filaments were determined either by recording antidromic action potentials from the tooth or by using a novel technique based on collision. Units that produced blood flow changes were further characterized by recording their response to hot, cold, osmotic and hydrostatic pressure, and mechanical stimulation of exposed dentine and to drying the dentine. Of 93 units isolated, 14 produced changes in pulpal blood flow when stimulated electrically at 1 or 10 Hz. All had conduction velocities (0.8-2.0 m s(-1)) in the C-fibre range. Ten produced vasodilatation and the remaining four, vasoconstriction. Five of the fibres that produced vasodilatation also responded to the hot stimulus, suggesting that they may form part of an axon reflex or similar mechanism. The four vasoconstrictor units did not respond to any form of stimulus other than electrical and were presumed to be sympathetic post-ganglionic fibres.

Blood flow changes in human dental pulps when capsaicin is applied to the adjacent gingival mucosa

OBJECTIVE

The purpose of this study was to determine whether changes occur in pulpal blood flow when capsaicin is applied to the adjacent gingival or alveolar mucosa in human beings.

STUDY DESIGN

Laser Doppler flowmetry was used to measure changes in pulpal blood flow (PBF) after applying capsaicin to adjacent gingival mucosa in 20 human volunteers. The procedure was repeated on 10 subjects after administration of an ipsilateral inferior alveolar nerve block and on the other 10 subjects after application of topical anesthetic to their adjacent gingival and alveolar mucosa.

RESULTS

PBF increased in 16 subjects and did not change in 4 subjects after capsaicin application. Ipsilateral inferior alveolar nerve block did not alter this effect. Pretreatment with topical lidocaine resulted in no change or decreased PBF in 8 subjects and increased PBF in 2 subjects.

CONCLUSION

Changes occur in the PBF of the mandibular canine teeth of some humans when capsaicin is applied to the adjacent gingival or alveolar mucosa.

The effect of short-term tooth intrusion on human pulpal blood flow measured by laser Doppler flowmetry

The purpose was to examine the effect of brief intrusive forces on human pulpal blood flow (PBF). Laser Doppler flowmetric measurements were made from 17 vital upper left central incisors of 17 participants who had clinically healthy tooth crowns and periodontal tissues. Brief intrusive forces (0.5,1,5 N; duration 20 s) were applied to the incisal edges of the examined teeth, and apical displacement of the teeth and the PBF were measured simultaneously. Recordings were made with and without an opaque rubber dam applied to the examined teeth. Intrusive force significantly reduced PBF flux both with and without the dam (P<0.05, Friedman analysis). The results indicate that transient apical displacement can reduce PBF.

Efficacy of laser Doppler flowmetry for the diagnosis of revascularization of reimplanted immature dog teeth

This study was performed to assess if laser Doppler flowmetry (LDF) is an improved method for the detection of revascularization of replanted teeth. Teeth were extracted and reimplanted under different experimental conditions. LDF readings were taken before extraction and weekly for 3 months. In control teeth, LDF baseline readings were taken and then repeated after the apical blood vessels were cut surgically. At the end of 3 months it was determined radiographically and histologically whether revascularization had occurred, i.e. vitality had returned.

RESULTS

LDF readings correctly predicted the pulp status (vital vs. non-vital) in 83.7% of the readings. 73.9% (17 of 23) were correct for the vital teeth and 95% (19 of 20) were correct for the non-vital teeth. Fisher's exact test (2-tail) indicated that there was no significant association between the efficacy of LDF and tooth type (P = 0.166), although P2 was the least accurate tooth tested. Wilcoxon's matched-pair signed rank test demonstrated that in the revascularized (vital) teeth, the flux value between the baseline and week 2 dropped significantly (P = 0.0001), increased significantly from week 2 to week 4 (P = 0.0001) and then decreased steadily until week 12. However, at week 12 the flux was still significantly higher than at week 2 (P = 0.010). In the teeth that failed to revascularize, the flux value dropped significantly by weeks 1 and 2 (P = 0.004 and P = 0.0001, respectively). Flux values did not increase from week 2. A Fast Fourier Transform (FFT) analysis confirmed a pulse of dominant frequency of 2 Hz in the teeth that returned to vitality and the lack thereof in those that stayed non-vital. One tooth in which the flux value evaluation indicated a non-vital tooth but the radiographic/histologic findings showed vital (false negative) possessed a pulse of dominant frequency and proved by this method to have successfully revascularized.

The effect of wavelength, bandwidth, and probe design and position on assessing the vitality of anterior teeth with laser Doppler flowmetry

OBJECTIVES

To investigate the effect of four variables: wavelength (633 nm and 780 nm), bandwidth filter (3 kHz, 15 kHz, 22 kHz), probe fibre separation (250 microns) and 500 microns) and distance of the probe from the gingival margin (2-3 mm and 4-5 mm) when assessing the vitality of anterior teeth with a laser Doppler flowmetry system.

DESIGN

Split-mouth cohort clinical trial.

SETTING

Childrens dental clinic, Glasgow Dental Hospital and School.

SAMPLE AND METHODS

Sample included 11 non-vital maxillary incisors with necrotic pulps in 10 patients (mean age 12.25 years old). Recordings were taken from the non-vital tooth and from a vital maxillary incisor from the same patient, using all 24 combinations of the recording variables listed above. The vital/non-vital ratios of the signals from the 11 pairs of teeth were calculated and discriminant analysis applied to the data.

RESULTS

Of the variables investigated, the combination of a 633 nm laser source with a 3 kHz bandwidth filter using a probe with a 500 microns fibre separation placed 2-3 mm from the gingival margin was the most reliable, with 10 out of a possible 11 true positives for pulpal necrosis, no false positives, and one equivocal diagnosis, and was the only combination that recorded a smaller blood flow from the non-vital tooth compared with the vital control tooth for all 11 pairs of teeth investigated.

CONCLUSIONS

It was concluded, therefore, that laser Doppler flowmetry can be of use in assessing the vitality of anterior teeth and that this is the preferred combination of recording variables for further investigations.

A comparison of laser Doppler flowmetry with other methods of assessing the vitality of traumatised anterior teeth

Laser Doppler flowmetry is a non-invasive electrooptical technique which allows the semi-quantitative recording of pulpal blood flow. This study aimed to determine the reliability (measured as the sensitivity and specificity) of laser Doppler flowmetry as a method of assessing the vitality of traumatised anterior teeth, and to compare it with standard pulpal diagnostic tests. Recordings of pulpal blood flow were taken from 67 non-vital anterior teeth (55 patients), where the pulpal status was confirmed by pulpectomy. For comparison, recordings were also taken from 84 vital anterior teeth (84 patients). Analysis of the recordings allowed diagnostic criteria to be developed which gave the technique a sensitivity and specificity of 1.0 for this sample. None of the other standard pulpal diagnostic methods tested was as reliable. This was usually due to low sensitivities, which ranged between 0.92 for sensibility testing with ethyl chloride down to 0.36 for periapical radiolucency and 0.16 for a history of pain. Laser Doppler flowmetry was found to be a reliable method of assessing the pulpal status of traumatised anterior teeth, although it is technique-sensitive and time-consuming to use.

Laser light transmission in teeth: a study of the patterns in different species

AIM

The aim of this study was to investigate the pattern of light transmission through teeth of different species and to examine laser light propagation within enamel from various animal sources.

METHODOLOGY

Sectioned teeth from five species--pig, horse, sheep, cat and rat--were evaluated. Samples were illuminated individually by a helium-neon laser light from the buccal surface using a probe 0.5 mm in diameter placed at varying angles between 60 and 120 degrees C. The pattern of light transmission was observed macroscopically. Further evaluation of laser light transmission in enamel was achieved using confocal microscopy.

RESULTS

In each species, light was transmitted through the tooth to the pulp, but in the cat and the rat, light was also transmitted to the far side of the tooth. Despite the different patterns of enamel in the species, light was transmitted through enamel to dentine.

CONCLUSION

Light from a laser Doppler probe appeared to reach the dental pulp in all the species: however, in the mammals with smaller teeth, light may also have been able to reach the periodontium and thus the reflected signal may not be entirely of pulpal origin.

Scattering of laser light directed onto the labial surface of extracted human upper central incisors

The purpose of this study was to evaluate the scatter of light through human teeth with laser Doppler flowmetry. An optical probe (probe 1), which mounted two optical fibers (one for light illumination and another for the measurement of backscattered light intensity) was placed on the labial surface of the extracted teeth. Another optical probe (probe 2) for the measurement of transmitted-light intensity was placed either on the mesial, distal, or palatal surface or in the canal of the teeth. The light intensity at probe 1 was stable, irrespective of the location of probe 2, whereas the transmitted light intensity at probe 2 tended to increase as probe 2 moved to more incisal positions on the mesial, distal, and palatal tooth surfaces. The results indicate that the light scatters to a wide area outside the tooth and provides information regarding the surrounding tissue blood flow.

The effects of 2% lidocaine with 1:100,000 epinephrine on pulpal and gingival blood flow

OBJECTIVE

The dental pulp is a low-compliance system that is particularly vulnerable to physiologic changes. Prolonged vasoconstriction may have detrimental effects. This goal of this study was to determine whether 2% lidocaine with 1:100,000 epinephrine, as used for buccal infiltration, decreases the blood flow in the dental pulp and adjacent gingival tissue.

STUDY DESIGN

The Periflux PF3 laser Doppler monitored pulpal and gingival blood flow before and after injection with local anesthetic. Ten human volunteers with at least one healthy and unrestored maxillary premolar were used in this study.

RESULTS

After injection of 0.9 ml of 2% lidocaine with epinephrine, there was a significant reduction from baseline values (p > 0.05) in both pulpal (73%) and gingival (51%) blood flow rate in all volunteers. Blood flow had not returned to baseline values after 1 hour.

CONCLUSION

This study showed that 2% lidocaine with 1:100,000 epinephrine significantly reduced blood flow pulpally and gingivally. Pulpal blood flow reduction was more than gingival blood flow reduction, which may be critical for compromised pulps with already reduced blood flow. The gingival effects may be of relevance with soft tissue procedures.

Comparison of two laser Doppler systems on the measurement of blood flow of premolar teeth under different pulpal conditions

An in vivo investigation was conducted to assess the ability of two laser Doppler flowmeters (DRT4, Moor Instruments Ltd; Laserflo BPM2, Vasamedics) to differentiate between vital pulp, ischaemically necrosed pulp, and an empty pulp chamber in premolar teeth in children. Sixteen intact, vital teeth in need of extraction for orthodontic purposes were identified. Laser Doppler blood flow readings were taken prior to (T1) and after the administration of adrenaline-free local anaesthetic (T2), after extraction and replantation of the teeth (T3), and after broaching the pulp tissue and replanting the teeth (T4). The data collected (flux values) for both instruments were analysed using a repeated measures ANOVA. Significant differences were found for vital pulp (T1, T2) versus ischaemically necrosed pulp (T3), and for vital pulp (T1, T2) versus an empty pulp chamber (T4), with the Moor DRT4 instrument. This instrument also detected a significant difference in pulpal blood flow to the vital pulp, before and after the administration of local anaesthetic. No other significant differences were found.

Revascularization of traumatized teeth assessed by laser Doppler flowmetry: case report

Infection of the pulp space in addition to the attachment damage of a traumatic injury to a tooth, results in serious complications and often tooth loss. Therefore, the prevention or treatment of root canal infection is a major consideration in these cases. In immature teeth, revascularization of a necrotic pulp is possible and highly desirable. Unfortunately, current sensitivity tests are poor indicators of revascularization, with the result that many pulps are removed unnecessarily. Laser Doppler flowmetry is an objective test of the presence of moving red blood cells within a tissue, which has been reported to be effective in the detection of tooth pulp vitality as well. A case is presented where an eight year old child severely luxated both maxillary central incisors. While only one of the incisors was weakly responsive to CO2 ice at 76 days after replantation, the laser Doppler flowmeter indicated that revascularization was occurring in both teeth at a much earlier time. Because of the laser Doppler readings, endodontic treatment was not initiated and the teeth developed normally.

Effect of brief intrusive force on human pulpal blood flow

The purpose of this study was to evaluate the effect of a 4-minute application of intrusive orthodontic force on human pulpal blood flow (PBF) with laser-Doppler flowmetry. Eight subjects had an intrusive force applied to a maxillary central incisor through a lever system. A cast chrome-cobalt coping was fabricated to fit over the incisor of each subject, and thus provided a reproducible point of force application as well as stabilization for the laser-Doppler flowmetry probe. Each subject participated in five testing sessions. During each session, PBF was measured during a 4-minute baseline period, then during the 4-minute force application, and then for a 12-minute period after removal of the force. Weights of 0, 5, 50, or 500 gm were attached to the end of the lever to produce intrusive forces ranging from 75 to 4498 gm. During the fifth testing session, local anesthetic with vasoconstrictor (epinephrine 1:100,000) was administered in place of the force application to determine the ability of this experimental paradigm to detect reductions in PBF. Baseline PBF values did not differ among sessions. Force levels had no statistically significant effect on PBF. However, PBF did drop significantly after administration of the vasoconstrictor. These results suggest that PBF is not altered during the application of a brief intrusive orthodontic force.

Pattern of transmission of laser light in teeth

This study examined the transmission of helium neon laser light in 20 dog and human teeth. The effect of probe position and angulation was observed both macroscopically and at a microscopic level using confocal microscopy. In all teeth in both species, laser light was transmitted through teeth to the pulpal surface with the light following the path of the enamel prisms and dentinal tubules. Probe angulation did not affect the pattern of light transmission, nor did probe position; however, the position of the probe on the tooth surface determined which section of the pulp was illuminated. Enamel and dentine together are able to collect and distribute light within the tooth, with both enamel prisms and dentinal tubules acting as optical fibres.

Environmental effects on laser Doppler pulpal blood-flow measurements in man

The increasing number of experiments using laser Doppler flowmetry in man for pulpal blood-flow recordings leads to questioning of the experimental recording conditions. The present study focused on three points: the design of the laser probe holder, the isolation of the tooth, and the influence of the recording site. A rigid polyurethane splint used in addition to different isolation devices (cotton roll, metal shield, rubber dam) was compared with a silicone splint. The silicone resulted in significantly higher values (+341%) than the polyurethane splint. The combination of the polyurethane splint with isolation devices decreased, in all cases, the flux values. The polyurethane/rubber-dam combination was the most efficient in individualizing the pulpal blood flow (-69% decrease). Recordings on non-vital teeth confirmed the hypothesis that there was periodontal contamination of the recorded flow, as the signal was abolished when using the polyurethane/rubber-dam combination. Cervical recording sites gave significantly higher values than occlusal sites (+42%). It is concluded that, in man, the part played by the periodontium may have been underestimated in previous recordings of pulpal blood flow. The use of a rubber dam in combination with a rigid splint to enhance the validity of recordings is proposed.

Effect of wavelength and bandwidth on the clinical reliability of laser Doppler recordings

The aim of this study was to investigate the effect of wavelength and bandwidth on laser Doppler flowmeter signals from vital and root-filled teeth, and to establish their sensitivity and specificity. Twenty human subjects were recruited, each with a vital tooth and the contralateral tooth root filled but not restored apart from the palatal access cavity. Readings were taken from these teeth for 3 min at 20 Hz for each of 3.1 kHz, 14.9 kHz and 22.1 kHz bandwidths using a modified laser Doppler blood flow monitor which permitted simultaneous recording using 810 nm and 633 nm light sources with a probe of four optical fibres with 0.25 mm separation. Ten traces from each combination of variables was examined by 10 trained observers who indicated if the traces came from vital or root-filled teeth judged by the amplitude and regularity of pulsatility of the trace. From the accuracy of their replies, sensitivity and specificity were calculated. Median flux values were higher for vital teeth than for root-filled teeth and for the 810 nm wavelength than for the 633 nm wavelength. Flux values increased with wider bandwidth using the 810 nm light source. With the 633 nm light source, the highest flux values were recorded using the 3.1 kHz bandwidth. Using the Mann-Whitney U test, there was a highly significant difference between readings from vital and root-filled teeth for the 3.1 kHz/810 nm wave length combination (p<0.003) and a significant difference for the 3.1 kHz/633 nm wavelength group (p<0.02). Comparison of other groups showed no significant difference (p>0.05). The 810 nm wavelength showed good sensitivity but poor specificity at 14.9 and 22.1 kHz bandwidths. The 633 nm wavelength showed good specificity, but poor sensitivity, at 14.9 and 22.1 kHz bandwidths. The 3.1 kHz bandwidth showed the best sensitivity and specificity for both wavelengths. Sensitivity and specificity were increased if the results of fast Fourier analysis were considered in addition to observations of flux values and pulsatility of traces. The 810 nm/3.1 kHz combination offered the greatest sensitivity and specificity as a test to distinguish between root-filled and vital teeth. This combination was best when the results of Fourier analysis were considered in addition to visual observations.

Experiments in pigs on the sources of laser Doppler blood-flow signals recorded from teeth

A laser Doppler blood-flow meter (Moor Type MBF3D) was used to record from the crowns of eight deciduous mandibular incisors in three anaesthetized pigs. The flow-meter probe was attached to the crown either 2 or 6 mm from the gingival margin. Recordings were made from each tooth with the supporting tissues intact, after exposing the root pulp, after cutting the pulp, and after death of the animal. At each stage the effect of wrapping the crown in aluminium foil was determined. There was no significant change in the signals when the root pulp was exposed (p > 0.05, paired t-test). Without foil, cutting the pulp reduced the signal recorded 2 mm from the gingival margin by an average of 85.1 percent (n = 8, p < 0.001) and at 6 mm by 87.9 percent (n = 4, p < 0.001). There were further significant reductions (p < 0.01) equivalent to 12.9 percent and 9.0 percent, respectively, of the control values when the animal was killed. The foil increased the average blood-flow signals recorded from intact teeth at both 2 and 6 mm from the gingival margin by 77.8 percent and 98.3 percent (p < 0.05), respectively. It also had a similar effect after pulp exposure. With foil, cutting the pulp reduced the signal by 86.2 percent and 92.8 percent at the two sites, respectively, and post mortem there was a further reduction of 12.4 percent and 6.1 percent. Thus, under all conditions the major part of the signal recorded from an intact tooth was from the pulp but a significant component (an average of between 14.9 percent and 7.2 percent depending on the conditions) was from tissues outside the tooth. The best performance was obtained with foil and with the probe 6 mm from the gingival margin.

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.